Library

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1985-1989  (3,724)
  • 1970-1974  (4,290)
  • 1890-1899  (8,112)
  • 1860-1869  (423)
  • Inorganic Chemistry  (15,815)
  • Electron microscopy  (734)
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Rheumatology international 9 (1989), S. 49-51 
    ISSN: 1437-160X
    Keywords: Synovium ; Monoclonal antibodies ; Immunohistochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cells making up the lining of the synovium have long been known as type A and B synoviocytes, with an intermediate form sometimes also described. Accumulating evidence shows that the type A cells are macrophages and the type B cells are fibroblasts. Recently, a definite orientation of these cells within the synovial lining has been observed. The number of synovial lining cells increases in joint disease, and this now seems more likely to be due to cellular recruitment rather than local proliferation.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of gynecology and obstetrics 246 (1989), S. 169-179 
    ISSN: 1432-0711
    Keywords: Human fetal endometrium ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Human fetal endometrium was examined by light and electron microscopy. Our study shows the following new morphological aspects: (1) Glands are already present. (2) Endometrium undergoes a maturation process during gestation and at late gestational age resembles late proliferative endometrium. (3) The nuclear bodies are present in cell nuclei throughout gestation. (4) Nucleolar channel systems (NCS) sometimes appear at a late gestational age. (5) Cells with the same morphology as that of endocrine cells are found in the basal layers of endometrium at a late gestational age. The significance of these morphological aspects is discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-2307
    Keywords: Hyperoxia ; Lung broncho-vascular reaction ; Electron microscopy ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to clarify the early phenomena involved in the lung reaction to hyperoxia, twenty adult male rats were exposed to 100% oxygen at 1 ATA. Morphological pulmonary lesions were detectable after only 24 h hyperoxia, and included vasoconstriction and perivascular oedema, bronchiolar constriction, and pericyte reaction. The lesions were irregularly scattered within the lung parenchyma and occurred preferentially in areas centred on bronchiolo-vascular stems. Even at the latest stages, pulmonary heterogeneity was obvious, from the coexistence of areas damaged at different times. Neuro-epithelial-bodies were found under the bronchiolar epithelium; the morphological aspect of the neuro-endocrine cells observed was consistent with hyperoxia-induced modulation of their secretory activity. Taken together, our findings show the speed of development of hyperoxia-induced pulmonary changes and raise some pathogenic considerations.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-2307
    Keywords: Thyroid neoplasms ; Electron microscopy ; Immunohistochemistry ; Calcitonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An ultrastructural study, both morphological and immunohistochemical, has been carried out on eight thyroglobulin-positive and nine thyroglobulin-negative medullary carcinomas of the thyroid. The morphometric analysis of granule size showed that all tumours contained cells with small granules and cells with medium size granules, whereas eight tumours had additional cells with large granules. The small granules had an electron dense core, while the medium and large sized granules were both pale-cored and dense-cored. The cells with small, medium or large secretory granules were all immunoreactive for calcitonin and CGRP. No ultrastructural differences were observed between thyroglobulin-positive and thyroglobulin-negative cases of medullary carcinoma of the thyroid.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 415 (1989), S. 297-300 
    ISSN: 1432-2307
    Keywords: Non-Hodgkin's lymphoma ; Electron microscopy ; Immunohistochemistry ; Intercellular junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A rare example of pleomorphic B cell non-Hodgkin's lymphoma is described in which tumour cells possessed simple intercellular junctions.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-2307
    Keywords: Human acute pancreatitis ; Zymogen granules ; Acinar cells ; Electron microscopy ; Immunocytochemistry ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study fine structural changes of acinar zymogen granules were investigated in human acute pancreatitis. Pancreatic tissue was obtained at surgery from 6 patients, prepared for ultrastructural analysis, and stained immunocytochemically for trypsinogen. Stereological parameters of zymogen granules were evaluated. The density of the immunocytochemical labelling for trypsinogen was estimated over zymogen granules, the rough endoplasmic reticulum, Golgi apparatus and the acinar lumina. In acute pancreatitis the number of zymogen granules was diminished and their size reduced. The density of the labelling for trypsinogen was unchanged over zymogen granules but showed a significant reduction over the rough endoplasmic reticulum, Golgi apparatus, and the acinar lumina. In general the integrity of zymogen granules was well preserved. Focally degenerative changes of zymogen granules and large autophagosomes were observed. From the immunogold labelling a disturbance of enzyme synthesis and secretion was suggested. Evidence is given that a disruption of the zymogen granule membranes and a fusion with lysosomal bodies might contribute to the pathogenesis of human acute pancreatitis.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-2307
    Keywords: Salivary gland ; Myoepithelioma ; Neoplasm ; Electron microscopy ; Immunohistochemistry ; Cytoplasmic filaments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The histological and ultrastructural features of five major salivary gland tumours, which have little or no evidence of duct- or gland-type differentiation in routine sections, are described. Four of the cases have the tumour cells organized as narrow, anastomosing cords of cells separated by a myxoid and vascularized stroma; we have designated such lesions as reticular-type myoepitheliomas. The fifth case has a solid growth pattern and is largely composed of hyaline cells, that is, a plasmacytoid myoepithelioma. Ultrastructurally, one reticular myoepithelioma reveals myoepithelial cell differentiation with microfilament aggregates, while the other three examples are composed of modified myoepithelial cells displaying widened intercellular spaces, prominent synthesis of extracellular glycosaminoglycans, distinct basal lamina development, and obvious accumulations of cytoplasmic intermediate filaments. In electron micrographs, the modified myoepithelial cells of the plasmacytoid variant closely resemble the tumour cells in the reticular form. Three cases had expression of both glial fibrillary acid protein (GFAP) and vimentin, but only one of the myoepitheliomas contained muscle-specific actin. At least focally, each of the cases exhibited a considerable spectrum of cytokeratin filaments. Using double-labeled immunofluorescent microscopy of one reticular variant and the plasmacytoid myoepithelioma, there was individual tumour cell co-expression of GFAP and vimentin focally in the plasmacytoid myoepithelioma, but co-expression of cytokeratins 13, 16 and GFAP were not noted in either case. As expected, co-expression of high- and low-molecular weight cytokeratin filaments was wide-spread in both myoepitheliomas. Most described myoepitheliomas have a solid growth pattern and are composed of spindle and plasmacytoid cells, but based on cytological features and growth patterns in this series, it is apparent that polygonalshaped cells with novel architecture can occur in myoepitheliomas. The results also indicate the close relationship between pleomorphic adenoma and such variants of myoepithelioma.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1432-2307
    Keywords: Human heart ; Papillary muscle ; Hypertrophy ; Mitochondria ; Specific staining ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Biopsy material of the hypertrophied human papillary muscle has been processed according to various electron microscopical techniques in order to study the mitochondrial ultrastructure and the association between mitochondria and sarcoplasmic reticulum (SR).En bloc staining with a Cu-Pb citrate solution resulted in specifically contrasted mitochondrial and sarcotubular membranes, characterized by numerous, discrete, electron-dense particles. The differences in staining patterns between the perinuclear mitochondria and their subsarcolemmal and interfibrillar counterparts suggest differences in chemical properties and/or metabolic activities. The selectively contrasted mitochondrial particles may represent a conglomorate of extrinisic and intrinisic respiratory enzymes and other membrane-associated proteins, while the majority of the electron-dense particles of the sarcotubular membrane may represent positively stained Ca2+-pumps. Ultrastructural findings in the present study strongly indicate that the slender mitochondrial projections represent an initial stage in a process leading to the formation of large and pleomorphic mitochondria. Intimate contact between adjacent mitochondria as well as between mitochondria and SR are documented. In the contact regions some of the specifically contrasted particles of the adjacent membranes had fused with each other. It is suggested that these particles represent membrane-bound transport proteins providing a system for interorganelle exchanges of metabolites and/or ions.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 415 (1989), S. 1-6 
    ISSN: 1432-2307
    Keywords: Visceral leishmaniasis ; L. donovani ; Parasitism ; Liver pathology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Liver parenchymal cell parasitism with the amastigotes form ofL. donovani was detected by electron microscopy in human visceral leishmaniasis. Endocytosis was considered to be the mechanism by which the leishmania entered the cell. Evidence of well preserved parasites within hepatocytes suggest this parasitism as a possible reservoir for recrudescence.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1432-2307
    Keywords: Clear cell sarcoma ; Melanosomes ; Cytochemistry ; Electron microscopy ; Nude mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to clarify the histogenesis of clear cell sarcoma of tendons and aponeuroses (CCS), two cases of human and one nude mouse-transplanted CCS line were studied using an ultrastructural and enzyme cytochemical approach. Most of the tumour cells obtained from the primary and transplanted CCS demonstrated melanosomes in various stages of development within the cytoplasm, whereas no melanosomes could be identified in the metastatic CCS. However, cholinesterase and tyrosinase activities could be demonstrated not only in the melanotic primary and transplanted CCS but also in the amelanotic metastatic CCS. The results therefore support the hypothesis that CCS is a soft tissue tumour derived from the neural crest.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 11
    ISSN: 1432-2307
    Keywords: Collagen secretion granule ; Myofibroblast ; Spindle cell tumour ; Electron microscopy ; Diagnosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Collagen secretion granules, representing stages in the intracellular packaging, transport and secretion of collagen-fibril precursor, have been studied by transmission electron microscopy in non-neoplastic human myofibroblasts and in neoplastic cells from a preliminary study of tumours exclusively or partly of spindle cell type. Vesicles, newly separated from Golgi saccules and containing finely fibrillar material, were identified as early presecretory granules, the most immature type of granule. Later stages exhibited longitudinally arranged, densely fibrillar bundles. Subsequently, secretory granules developed more homogeneously dense content. Fibril-containing cisternae near the plasma membrane were interpreted as either endocytotic or lysosomal structures, or as participants in the final stages of secretion. The features by which collagen secretion granules can be distinguished from other Golgi products, in particular melanosomes, Weibel-Palade bodies and lysosomes, are pointed out. The significance of these organelles for cell identification and tumour diagnosis is discussed.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Virchows Archiv 415 (1989), S. 91-95 
    ISSN: 1432-2307
    Keywords: Carcinosarcoma ; Urinary bladder ; Immunohistochemistry ; Electron microscopy ; Rhabdomyoblast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A case of urinary bladder carcinosarcoma (UBCS) is reported with light, immunohistochemical and electron microscopical findings. The tumour consisted of a squamous cell carcinoma, variable spindle cell stromal elements compatible with fibrosarcoma, and rhabdomyoblasts. Intermediate filament co-expression of cytokeratin and vimentin was shown by immunohistochemistry. Electron microscopy (EM) confirmed the nature of the three components, and indicated some similarities between the three cell-types present. Comparisons with the previous UBCS in the literature are made.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 78 (1989), S. 555-560 
    ISSN: 1432-0533
    Keywords: Sporadic motor neuron disease ; Lewy body-like hyaline inclusions ; Immunocytochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Lewy body-like hyaline inclusions were immunocytochemically and electron microscopically investigated in a patient with sporadic motor neuron disease. The hyaline inclusions were chiefly observed within the perikarya of both normal-looking and chromatolytic anterior horn cells in the lumbar spinal cord, but some were detected in the axons and dendrites. Usually, a single inclusion was found in the perikaryon, but in rare cases two or more were observed. Immunocytochemically, these inclusions were intensely immunostained with anti-ubiquitin anti-body. Ultrastructurally, the hyaline inclusions were chiefly composed of randomly arranged linear structures associated with ribosome-like granules, varying from compactly arranged linear densities to more loosely packed ones. They contained scattered vesicles of various sizes and occasionally a focal accumulation of randomly arranged 10-nm neurofilaments or 13–25-nm filamentous structures.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 79 (1989), S. 340-346 
    ISSN: 1432-0533
    Keywords: Paraganglioma ; Melanin ; Orbit ; Immunocytochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A paraganglioma of the orbit in a 21-year-old woman is presented, containing oculo-cutaneous melanin in many tumor cells, occasionally adjacent to neurosecretory granules, and in macrophages. This tumor expands the list of neuroectodermal tumors with potential melaninization.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 180 (1989), S. 237-242 
    ISSN: 1432-0568
    Keywords: Perineurium ; Lanthanum ; Diffusion barriers ; In vivo ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary While the perineurium as a diffusion barrier has been extensively investigated by light and electron microscopy, copy, such studies have been largely restricted to the use of protein tracers. In the present study the permeability of the perineurium to a physiologically more relevant ionic tracer has been assessed. In vivo the rat sural or tibial nerve was either microinjected with lanthanum nitrate solution for endoneurial application or bathed in the lanthanum solution for epineurial application. The findings generally demonstrated an effective barrier to the tracer which failed to penetrate the inner layers of the perineurium. Only at the highest lanthanum concentration and longest time intervals employed did trace quantities occasionally penetrate the barrier and then only in the presence of some cytopathological changes to the outermost perineurial cells. The usefulness of the microinjection method was limited by the slight but unavoidable trauma to the perineurium. The findings are related to those of other studies which have used electron dense tracers, also to studies using physiological including electrophysiological techniques and morphological including freeze-fracture methods.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 180 (1989), S. 273-280 
    ISSN: 1432-0568
    Keywords: Wallerian degeneration ; Myelin breakdown ; Light microscopy ; Electron microscopy ; Marchi staining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Morphological aspects of myelin breakdown in the posterior funiculus during Wallerian degeneration were studied in kittens subjected to lumbosacral dorsal rhizotomies 6–8 days after birth. The first sign of myelin breakdown was characterized by swollen or shrunken nerve fibers. Shortly thereafter there was an increased occurrence of collapsed myelin sheaths and later of rounded myelin bodies. Myelin was clearly seen in microglial cells. Correlative observations on Marchi-stained material indicated the simultaneous and frequent appearance of Marchi-positive bodies (MPB:s) and myelin bodies. Due to the rapidity of the degeneration process in the kitten, the increase in the occurrence of Marchi-positive granules (MPG:s) seemed to start concomitantly with increased occurrence of MPB:s. However, the frequent occurrence of MPG:s outlasted that for MPB:s. The findings indicate that the MPB:s may be the counterpart to myelin bodies and the MPG:s to lipid droplets. Microglial cells may be responsible for the primary uptake of degenerating myelin and the subsequent transformation of myelin bodies to lipid droplets. The much faster breakdown of myelin and elimination of lipid material in the degenerating posteror funiculus of the kitten, as compared to the adult, seemed to be due not only to the lower myelin content in the kitten, but also to a higher density of microglia and a greater efficiency in the myelin breakdown process in the degenerating posterior funiculus of the kitten.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 17
    ISSN: 1432-0533
    Keywords: Schwann cell ; Oligodendrocyte ; Electron microscopy ; Myelin ; Optic nerve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neonatal rats were exposed to Tellurium (Te), via the mother's milk, from the day of birth until sacrifice at 7, 14, 21, and 28 days of age. Light and electron microscopy revealed Schwann cell and myelin degeneration in the sciatic nerves at each age studied. These changes were similar to those described in weanling rats as a result of Te intoxication. In the CNS, hypomyelination of the optic nerves was convincingly demonstrated at 14, 21, and 28 days of age, accompanied by some evidence of myelin degeneration. These changes were also seen in the ventral columns of the cervical spinal cords, although less markedly, and were confirmed by quantitative methods. There was little evidence of oligodendrocyte pathology in the CNS, and it appears that degeneration of these cells is not the primary cause of the CNS hypomyelination, in contrast to the PNS where Schwann cell degeneration has been shown to precede the myelin pathology.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 78 (1989), S. 472-483 
    ISSN: 1432-0533
    Keywords: Astroblastoma ; Electron microscopy ; Immunohistochemistry ; Organ culture ; Tanycytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two examples of cerebral astroblastoma have been studied by electron microscopy and immunohistochemistry, one of them having been maintained in vitro in an organ-culture matrix system for 8 months and the explants studied by light and electron microscopy at different time intervals. The fine structural characteristics were those of a glial cell type with features intermediary between those of astrocytes and ependymocytes. They recapitulated the structure of the tanycyte, a glial precursor cell which is normally found scattered along the ependymal lining of the embryonal and neonatal mammalian brain, but is distinct from epithelial ependymocytes. The possible origin of some astroblastomas from such a cell would account for a number of characteristics in this enigmatic type of glioma.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 180 (1989), S. 243-257 
    ISSN: 1432-0568
    Keywords: Dorsal lateral geniculate nucleus ; Synapse formation ; Synaptic glomerulus ; Rat ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Synapse formation and maturation were examined in the rat dorsal lateral geniculate nucleus (dLGN) from birth to adulthood. Examination of animals, whose ages were closely spaced in time, showed that the maturation of the synaptic organization of the nucleus takes place chiefly during the first 3 weeks of postnatal life. This period of maturation may be divided into 3 broad stages. During the first stage, which spans the first 4 days of life, there are only a few immature synapses scattered throughout the nucleus; occasionally aggregates of 3 or 4 synapses are encountered. Dendrodendritic synapses first appear at the end of this stage. The second stage, which lasts from the end of the first stage through day 8, is characterized by intensive synaptogenesis as well as extensive growth and degeneration. For the first time, large boutons resembling retinal terminals form multiple synaptic contacts with dendrites and dendritic protrusions; these synaptic arrangements are partially covered by glial processes. A feature characteristic of the developing dLGN during the first 2 postnatal weeks, and particularly during the second stage, is the presence of membrane specializations that resemble vacant postsynaptic densities. These specializations, which may be unapposed or opposite another neuronal process, decrease in frequency as the number of synapses increases. It is not known whether these densities are converted to synapses or whether they result from loss of presynaptic elements. The third stage in the process of synaptogenesis, which spans a period between days 10 and 20, is characterized by myelination and by the diminution of growth cones, degenerating profiles and vacant postsynaptic densities. There is also a very significant increase in the number and maturation of synapses including synaptic glomeruli. However, it is not until the end of this stage that synapses appear qualitatively indistinguishable from synaptic arrangements identified in adult animals.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 20
    ISSN: 1432-0533
    Keywords: Senile plaque-like structure ; Periodicacid methenamine silver (PAM) method ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Numerous diffuse senile plaque-like structures (SPLSs) were found in the cerebral cortex from cases with dementia of the Alzheimer type by means of the methenamine-Bodian method. SPLSs varied in shape and size. They were never recognized in the original Bodian, PAS and Congo red preparations, but were positive with anti-β-protein immunostaining and periodic-acid methenamine silver (PAM) methods, which are thought to specifically stain amyloid substance. With PAM electron microscopy, we found sparse aggregations of amorphous, often ramified, structures with fine granular silver deposits in SPLS. Routine electron microscopic examination on the same portion where SPLS were confirmed by PAM electron microscopy revealed amorphous, partially fibrous structures. These structures might be amyloid or amyloid-precursor substance. In SPLSs only a few degenerated neurites and astrocytic processes with glycogen granules were seen. We consider SPLSs to be a kind of senile plaque.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 78 (1989), S. 594-604 
    ISSN: 1432-0533
    Keywords: Neurocysticercosis ; Pathogenesis ; Histochemistry ; Immunohistochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study was based on two cases of disseminated human neurocysticercosis from India. The material availabel was examined grossly, and by light microscopy, histochemistry, immunomorphology and electron microscopy. The results showed that the parasites commonly embolized to the anatomically discernable gray-white matter junction of the brain and were located in cavities, the walls of which were dilated vascular channels. The parasite-nutrition process was through endocytosis and microtrichal activity. To camouflage themselves from the host-defense mechanisms, the parasites apparently covered themselves with host-tissue-like material. Host reactivity to the parasite was heralded morphologically by the physical anchoring of the parasite by activated endothelial cells, loss of the host-tissue-like cover and an acute polymorphonuclear leucocytic response.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 77 (1989), S. 664-666 
    ISSN: 1432-0533
    Keywords: Hemimegalencephaly ; Golgi study ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pathological findings in a case of hemimegalencephaly are presented. Hemispherectomy, performed because of intractable seizures, allowed an electron microscopic and Golgi study. Glial abnormalities consisted of hyperplasia of glia cells with giant astrocytes often containing several nuclei and proliferation of numerous Rosenthal fibers. Golgi stain showed many giant neurons with a perikaryon covered by perisomatic processes, and a complex dendritic tree. Glial abnormalities could be correlated with the firmness of the hemisphere and intense hypersignal on magnetic resonance imaging. Giant neurons were associated with an increase in size of the perikaryon and dendritic tree; this pattern suggests a polyploidy.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 23
    ISSN: 1432-0533
    Keywords: Cerebral ischemia ; Ischemic neuronal injury ; Long-term recovery ; Mongolian gerbil ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Unilateral transient cerebral ischemia was produced in Mongolian gerbils by clipping the left common carotid artery for 1h. About 60% of the gerbils with neurological symptoms had post-ischemic seizures. The majority of those that had seizures died within a few days, and sections of their cerebral cortices contained many dark and shrunken neurons. However, the gerbils that did not have seizures survived without any severe complications. In the cerebral cortex of the latter, the neurons with diffuse or peripheral pallor of the perikarya were seen along with a small number of dark and shrunken neurons. Diffuse pallor occurred within a few hours following ischemia in layers III, V and VI, and disappeared 1 or 2 days after recirculation. Electron microscopically, these neurons showed dispersion of ribosomes, simple and elongated profiles of rough endoplasmic reticulum (r-ER), clustered vacuoles, and mild to moderate mitochondrial swelling. Occasional net-like tubulomembranous structures, probably derived from r-ER, were observed. On the other hand, peripheral pallor became apparent after 5 days following ischemia, usually involving layer II first and gradually extending to the deeper layers. Concomitantly, the amount of neuropil decreased and the dendrites exhibited tortuosity and irregularity in layer II. Electron microscopically, these neurons showed marked swelling of peripheral perikarya and polyribosomes and organelles were located peripherally to the nuclei. In addition, numerous degenerated axon terminals and distended dendrites were observed around the neurons. These observations indicate that diffuse pallor represents damage directly induced by ischemia and subsequent recirculation, while peripheral pallor is the delayed and remote effect of ischemia, probably due to degeneration of neuronal processes.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 79 (1989), S. 10-17 
    ISSN: 1432-0533
    Keywords: Locus ceruleus ; Pick bodies ; Lewy bodies ; Immunocytochemistry ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In classical Pick's disease with typical Pick bodies, inclusions resembling those present in the cerebral cortex are frequently found in the locus ceruleus. In three such cases Pick bodies were studied by light and electron microscopy and compared with Lewy bodies, inclusions more commonly found in this location. In contrast to the situation in the cerebral cortex, nerve cells with multiple Pick bodies were often found in the locus ceruleus, but in other respects definite light and electron microscopic differences between Pick bodies and Lewy bodies were present. Pick bodies were slightly basophilic and never had a central core or a peripheral halo. They were intensely argyrophilic. Differences in immunocytochemical reactions were especially marked with antibodies to tau and to paired helical filaments. Pick bodies displayed an intense reaction with these two antibodies, contrasting with that of Lewy bodies, which either lacked reactivity or reacted in a peripheral band. By electron microscopy the Pick bodies were composed of random filaments with smooth contour, whereas typical Lewy bodies had fuzzy deposits on filaments that radiated from a central core. Pick bodies in the locus ceruleus therefore maintained their immunocytochemical and electron microscopic characteristics and did not take on the character of Lewy bodies. Such differences point to a different pathogenesis and perhaps etiology of these two types of inclusions and attest to the marked difference clinically and pathologically between Pick's and Parkinson's diseases.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 281 (1989), S. 165-172 
    ISSN: 1432-069X
    Keywords: Netherton's syndrome ; Retinoid therapy ; Etretin ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A young female patient, expressing the symptom triad of Netherton's syndrome, i.e., ichthyosis linearis circumflexa Comèl, trichorrhexis invaginata and other hair shaft defects, and atopic diathesis, has been treated successfully with the new retinoid preparation Etretin. Our electron microscopical study especially focused on the ultrastructural effect on the characteristic, active part of the skin lesions, which is only found within a narrow borderline just preceding the lesion's margin. In untreated skin, this part is characterized by dermal inflammation, immigrating inflammatory cells, and specific keratinization disturbances: synthesis of keratinization proteins is suppressed, serum exudates invade the epidermis, either filling the intercellular spaces of the upper spinous and the granular layer as finely granular, amorphous material, or they are partly phagocytosed and lie within intracellular, round-oval inclusions. The portions of the lesions lying towards the center are unspecific and represent recovery stages, ultrastructurally resembling stages of normal wound repair. Oral therapy with Etretin did not heal the basic defect, but drastically reduced exoserosis and the deposition of intra- and extracellular material. Keratinization seemed to normalize. The condition of the hair was also improved.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    Springer
    Archives of dermatological research 281 (1989), S. 254-259 
    ISSN: 1432-069X
    Keywords: Innermost cell layer ; Tonofilaments ; Huxley's cells ; Henle's cells ; Anagen hair follicles ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To elucidate the biologic roles and further cytologic characteristics of the innermost cell (IMC) layer of the outer root sheath (ORS), human anagen hair follicles were ultrastructurally examined. In the lower follicle, the transeversely running tonofilaments in the inner side of the cytoplasm of the IMCs showed a massive accumulation, facing the keratinized part of a Huxley's cell protruding through a Henle's pore. In a rare instance, a spindle-shaped cell was seen between the IMC layer and the keratinized Henle's layer. At the lower isthmus portion, some of the IMCs containing a large number of tonofilaments showed a partial degeneration of the inner side of the cytoplasm. More distally, intercellular spaces between the keratinized IMCs and keratinized Henle's cells were partly dilated and contained amorphous substances. It is suggested that the IMCs in the lower follicle may play a role to support and cover the inner hair structures, tightly as hoops of a barrel. In the isthmus portion, the IMCs may loosely support and guide the keratinized Henle's cells undergoing degeneration.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 27
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 75 (1989), S. 563-568 
    ISSN: 1432-1106
    Keywords: Retina ; Diencephalon ; Co-culture ; Synapses ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Explants of chick embryo diencephalon co-cultured with explants of retina display areas of complex neuropil containing large retinal-like endings which establish synaptic contact with conventional and presynaptic dendrites. Transection of fibre bundles linking retinal to diencephalic explants results in the degeneration of endings of this type, suggesting that axons of extrinsic (retinal) origin innervate the diencephalic explants in an in-vivo-like manner.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 28
    ISSN: 1432-1106
    Keywords: Nerve growth factor ; C6 glioma cells ; Chromaffin cells histofluorescence ; Electron microscopy ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to maintain a chronic supply of growth factor for medulla cells in vitro, chromaffin cells from rat, African green monkeys and man were co-cultured with C6 glioma cells, which secrete growth factors that sustain sympathetic neurons in vitro. The response of chromaffin cells to coculture was compared to treatment of medullary cells with nerve growth factor (NGF) alone. Dispersed chromaffin cell preparations were obtained by a trypsin-collagenase procedure, and subjected to differential plating on collagen-coated surfaces. With both human and monkey tissue, non-chromaffin cells did attach to the culture plates and an enriched chromaffin cell population could be replated. Rat adrenal medulla cells survived very poorly in vitro and were not enriched in this procedure. Cultured human and monkey chromaffin cells survived as epithelial cells (50%) and showed neuritic outgrowth on 55 to 66% of the cells after eight days when treated with nerve growth factor (NGF). These cells showed strong catecholamine histofluorescence, tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DBH) immunoreactivity. In contrast, only ten percent of adult rat chromaffin cells survived in culture, although NGF treatment rescued an additional 20% of the cells and induced neuritic outgrowth after one week in vitro. C6 glioma cells were treated with mitomycin C bromodeoxyuridine to inhibit mitosis and were plated with the various medulla cells in a one to one ratio. Both human and monkey chromaffin cells expressed extensive and enhanced neuritic arborization within eight days of co-culture, (64–82% respectively) and exhibited intimate contact with the glioma cells as seen at the ultrastructural level. Importantly, survival of adult rat adrenal medulla cells was enhanced to 50% or more with 40% of the cells extending neurites when co-cultured with glioma cells for seven days. Chromaffin cells from all three species reacted for TH, DBH and PNMT in co-culture and were histofluorescent. The majority of these cells were also immunoreactive for serotonin and enkephalin, while only 37% of chromaffin cells indicated the presence of NPY. These data indicate that adrenal medulla can be maintained in vitro as the neuronal phenotype when co-cultured with growth factor producing cells and that this strategy may be useful for in vivo transplantation studies.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 78 (1989), S. 425-434 
    ISSN: 1432-1106
    Keywords: Avian forebrain ; Synapses ; Stereology ; Disector ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The lobus parolfactorius (LPO) of the chick has been shown to undergo an increase in the mean synaptic numerical density (Nv syn) in response to one-trial passive avoidance learning (Stewart et al. 1987). The present study was undertaken in order to describe the pattern of normal development of synapses in the LPO, to further investigate the significance of this plastic response. The LPO's from each hemisphere of pre-hatch (16 days), and post-hatch (1 day, 9 day and 22 day old) chicks were processed for electron microscopy. Synapses were classified into asymmetric spine, asymmetric shaft, symmetric spine, and symmetric shaft synapses, on the basis of the density of the post-synaptic thickening and the nature of the post-synaptic target. A 3-dimensional stereological probe was used (the ‘disector’) to calculate Nv syp, and mean projected height (H syp) of the post-synaptic density (PSD). Mean values for each age and hemisphere were compared with a 2-way analysis of variance test using paired samples. A six-fold increase in Nv syp was seen between 16 days in ovo, and 9 days post-hatch. There was a hemispheric asymmetry at 9 days post-hatch, with the left hemisphere LPO containing 1.6 times as many synapses per μm-3. There was a subsequent period of reduction in synaptic density in the left hemisphere LPO between 9 and 22 days post-hatch. The Nv of all classes of synapse increased with age, but the proportions of the symmetrical synapses with respect to the total number of synapses, decreased with age. This decrease was of a similar magnitude for each hemisphere. A hemispheric difference was seen in post-hatch asymmetric synapses, with a greater proportion of asymmetric spine synapses in the left hemisphere. The magnitude of the hemispheric asymmetry was constant throughout the 3 week period of post-hatch development, but was not present in pre-hatch chicks. The PSD increased in length in each hemisphere by approximately 40% between post-hatch day 1 and post-hatch day 9. These data show that the LPO contains a synaptic population which undergoes substantial modification during the first week post-hatch. An asymmetry exists at post-hatch day 9 which is not present at the earlier ages investigated, nor indeed after 22 days post-hatch. This may have significance with regard to studies of passive avoidance learning in the one-day old chick, where an increase in both the size and number of synapses in the LPO has been demonstrated (Stewart et al. 1987). It is possible that ‘training’, in this situation, may simply enhance the timing of synaptic events that result as a consequence of normal development.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 30
    ISSN: 1432-198X
    Keywords: IgA nephropathy ; Electron microscopy ; Glomerular basement membrane lesions ; Prognosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Seventy-three patients with IgA nephropathy (IgAGN), under the age of 15 years at the time of the discovery of the disease, were investigated with respect to glomerular basement membrane (GBM) lesions. Irregular attenuation or widening of GBM, especially on the epithelial side, was observed in 28 cases (38%). These two changes are referred to aslysis of GBM and were considered to be the primary and specific changes among the GBM lesions in IgAGN. GBM thickening with layering of lamina densa was found in 37 of 73 cases (51%), but this change has been observed in other types of glomerular diseases. GBM lesions similar to those seen in IgAGN were also observed in Henoch-Schönlein purpura nephritis (HSPN) and poststreptococcal acute glomerulonephritis (PSAGN). Lysis of GBM was observed only in IgAGN, HSPN and PSAGN. Subepithelial and intramembranous deposits appeared to have an important role in the development of these GBM lesions. The presence of GBM lesions was correlated with a high incidence of cellular crescents but not with other clinical or light microscopic findings. The presence of these GBM lesions in IgAGN does not have a significant effect on the prognosis, at least in childhood. The affected GBM seemed to recover without leaving any significant residual damage in most cases. In the long-term prognosis of the disease non-immunological factors, such as ageing or hypertension, seem to be important.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 236 (1989), S. 361-363 
    ISSN: 1432-1459
    Keywords: Mitochondrial encephalomyopathy ; MELAS ; Mitochondrial inclusion ; Pilovacuolar inclusion ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The case of a 33-year-old man with clinical features of mitochondrial encephalomyopathy is presented. He suffered from recurrent cerebral infarctions, cerebellar ataxia, deafness, retinopathy, weakness, and cardiac and renal disorders. Biochemical and light microscope investigations of skeletal muscle did not show any mitochondrial abnormality. Electron microscopy revealed the presence of a hitherto unreported peculiar “pilovacuolar” inclusion in numerous mitochondria, composed of an electron dense pile or rod within a vacuole, while globular or crystalline inclusions were absent.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 32
    ISSN: 1432-072X
    Keywords: Aggregation substance ; Enterococcus faecalis ; Electron microscopy ; Field emission scanning electron microscopy ; Immunogold labelling technique ; Sex pheromone system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution of sex pheromone induced aggregation substance was studied on the cell surface of various Enterococcus faecalis strains. In the accompanying paper we have shown that the aggregation substance appears as a layer of hairlike structures. Using direct and indirect immunogold technique, transmission electron microscopy and high resolution scanning electron microscopy we investigated the appearance and distribution of the aggregation substance. The “hairs” increase in number with increasing exposure to sex pheromones (maximum density: 1300/μm2). We show that these structures are unequally distributed over the cell surface, even if the cells were induced by sex pheromones for a long period of time. Statistical analysis of the unequal distribution indicates that aggregation substance is incorporated into pre-existing “old” cell-walls and that this incorporation shows a saturation ca. 40 min after addition of sex pheromones.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 33
    ISSN: 1432-0878
    Keywords: Anterior pituitary gland ; Electron microscopy ; Growth hormone ; Spontaneous dwarf rats (dr/dr)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The spontaneous dwarf rat is a novel experimental model animal on the study of pituitary dwarfism. The fine structure of the anterior pituitary cells was studied in the immature and mature dwarf rats. Pituitary glands were removed from 5-, 10-, 20-day-old immature dwarfs, adult (45 days-16 weeks) dwarfs and normal 3-month-old rats and processed for electron-microscopic observation. In the control animals, growth hormone cells were readily identified by their ultrastructural characteristics, such as the presence of numerous electron-dense secretory granules, 300–350 nm in diameter, well developed rough endoplasmic reticulum and a prominent Golgi complex. In contrast, growth hormone cells were not found in the anterior pituitary gland of the spontaneous dwarf rat at any age examined. Other pituitary cell types, i.e., luteinizing hormone/ follicle stimulating hormone, thyroid stimulating hormone, adrenocorticotropic hormone and prolactin cells, appeared similar in their fine structure to those found in the control rats. In the pituitary gland of dwarf rats, a number of polygonal cells were observed either with no or relatively few secretory granules. The rough endoplasmic reticulum was arranged in parallel cisternae and the Golgi complex was generally prominent in these cells. In addition, many were found to have abundant lysosomes. A few minute secretory granules were occasionally observed; however, the immunogold technique failed to localize growth hormone or prolactin in the granules. The nature of these cells remained obscure in this study. Since their incidence and fine structural features, other than the secretory granules, were quite similar to those of the growth hormone cells in normal rats, we postulate that these cells are dysfunctional growth hormone cells. These results suggest that the cause of the growth impairment in the spontaneous dwarf rat is due to a defect in the functional growth hormone cells in the pituitary gland, and since other pituitary cell types appeared normal, the disorder seems to be analogous to the isolated growth hormone deficiency in the human.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 34
    ISSN: 1432-0878
    Keywords: Subcommissural organ ; Secretory activity, neural control ; Transplantation ; Long-spacing collagen ; Immunocytochemistry ; Molecular markers (neuronal, glial) ; Electron microscopy ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary There is increasing evidence that, in the rat, a serotonin-mediated neural input may have an inhibitory influence on the secretory activity of the subcommissural organ (SCO). In the present investigation the rat SCO was studied 7, 30 and 90 days after transplantation under the kidney capsule, an area devoid of local serotonin-containing nerves. The grafted tissue was examined by use of immunocytochemistry employing a series of primary antisera, lectin histochemistry and transmission electron microscopy. The grafted SCO survived transplantation and contained, in addition to secretory ependymal and hypendymal SCO-cells, also elements immunoreactive with antisera against glial fibrillary acidic protein or S-100 protein. In transplants, SCO-cells produced a material displaying the characteristic immunocytochemical and lectin-binding properties of SCO-cells observed under in-situ conditions. The ependymal cells lined 1–3 small cavities, which contained secretory material. A fully developed structural equivalent of Reissner's fiber was, however, never found. The immunocytochemical and ultrastructural study of the grafted SCO showed an absence of nerve fibers within the graft and suggested a state of enhanced secretory activity. A network of protruding basal lamina structures connected the secretory cells to the newly formed capillaries revascularizing the SCO. One week after transplantation, long-spacing collagen started to appear in expanded areas of such laminar networks and also in the perivascular space. It is suggested (i) that the formation of long-spacing forms of collagen is triggered by factors provided by the SCO-secretory cells, and (ii) that secretory material of the ependymal and hypendymal cells may reach the reticular extensions of the basal lamina. In contrast to the SCO in situ, the grafted SCO-cells showed a positive immunoreaction for neuron-specific enolase. They became surrounded by a S-100-immunoreactive glial sheath that separated them from other transplanted cell types and the adjacent kidney tissue of the host.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 35
    ISSN: 1432-0878
    Keywords: Proximal colon ; Distal colon ; Cholesterol ; Filipin ; Freeze-fracture ; Electron microscopy ; Guinea Pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary It is generally accepted that variations in membrane cholesterol content affect the fluidity of the bilayer, thus altering its permeability. In the biological membranes, in physiological conditions, a high cholesterol content rigidifies the bilayer decreasing its permeability, a lower cholesterol content induces the opposite effect by increasing the permeability. Since differences in the epithelial permeability for short chain fatty acids have previously been demonstrated in the proximal and distal colon of the guinea pig, these two regions were investigated to establish whether differences in membrane cholesterol content of the absorbing cells can be demonstrated. Freeze-fracture replicas of filipin-treated colonic tissue were used. The results show that in the proximal colon the density of filipin cholesterol complexes located on the luminal plasma membrane of the columnar absorbing cells was significantly higher (about twice) than in the distal colon. Therefore the lower amount of cholesterol present in the membrane of the absorbing cells in the distal colon indicates a greater fluidity of the membranes of the epithelial cells in this region. Such fluidity could be correlated to the higher absorption rates of shortchain fatty acids characteristic of this region.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 36
    ISSN: 1432-0878
    Keywords: Stomach ; Endocrine cells ; Electron microscopy ; Morphometry ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ultrastructural morphometric study of the endocrine cells of the oxyntic mucosa of the stomach in gastric biopsies collected from five male and five female healthy volunteers aged 19–31 was performed. No sex-related differences were disclosed. Endocrine cells accounted for 1.2±0.4% of the epithelial volume and 0.9±0.4% of the mucosal volume, i.e., including the lamina propria. After classification of the specific endocrine cell types according to the ultrastructural morphology of secretory granules, the volume densities of ECL, P and D cells (30±9%, 24±7%, and 22±4% of the entire endocrine cell mass, respectively) were higher than those of other endocrine cell types. In particular, EC cells contributed less than 10% and X cells represented a very low proportion of the total cells. Non-granulated profiles of cells which in all other respects appeared to be endocrine were also found with a volume density of 8±4%. D cells were distinguished by the high fraction of cytoplasm occupied by secretory granules (31±5%). Subdivision of the whole mucosa into four horizontal segments revealed the endocrine cells to be mostly distributed in the three lower, with virtually no endocrine cells in the superficial segment. The quantitative ultrastructural analysis of the endocrine cell population of the normal human oxyntic mucosa provided by this study may allow a better evaluation of physiological and pharmacological variations of the endocrine cell population.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 37
    ISSN: 1432-0878
    Keywords: Penile erection ; Electron microscopy ; Immunohisto(cyto)chemistry ; Vasoactive intestinal polypeptide (VIP) ; Neuropeptide Y (NPY) ; Cercopithecus aethiops (Primates)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cavernous body of green monkeys contains many unmyelinated and few myelinated axons. The unmyelinated axons form terminals in the adventitia of the arteries, between trabecular muscle cells, in the interstitium, and close to endothelium cells of the sinuses. All terminals displayed predominantly “small clear vesicles” and very few “large granular vesicles”; “small granular vesicles” were not seen. However, in rabbit penises, terminals with many large granular vesicles are prominent. Immunohistochemistry (PAP technique) showed a dense network of VIP- and NPY-reactive fibres around the arteries and around trabecular muscles. The density of nerve fibres was particularly high around the subendothelial cushions of the helicine arteries. Double staining for NPY and VIP revealed that both peptides were colocalized. Immunocytochemistry (preembedding PAP technique) showed VIP- and NPY-reactivity in terminals with small clear vesicles; the reaction product was bound to the cytoplasmic face of different membrane types. Although the intracellular localization of the reaction product is probably due to artefactual displacement during preparation, the uniformity of the terminals questions the view that large and small granular vesicles in all species characterize peptidergic and noradrenergic terminals, respectively. The essential findings can be summarized as (1) a high degree of uniformity of nerve terminals, (2) colocalization of VIP and NPY, (3) heavy innervation of the subendothelial cushions of the helicine arteries, and (4) possible innervation of endothelial cells.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 256 (1989), S. 573-580 
    ISSN: 1432-0878
    Keywords: Epididymis ; Epithelium ; Monolayer culture ; Histochemistry ; Electron microscopy ; Rat (Sprague-Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary N-acetylglucosaminidase (NAG), acid phosphatase (ACP) and alkaline phosphatase (AKP) were localised histochemically in fixed cells from the 37-day-old rat epididymis grown in static monolayer culture for 2–8 days. ACP and NAG were cytosolic enzymes found in perinuclear positions, whereas staining of AKP was consistent with a membranous position. These enzymes were also examined in frozen tissue sections of the epididymis, from rats of the equivalent age, where NAG had intense activity in both supra- and infra-nuclear cytoplasm and ACP was more active apically. For the first time AKP was localised along basolateral membranes of the epithelium and in the lumen of the mid-caput region. The monolayer in culture was of principal cells only and they maintained their polarity and ultrastructural characteristics, but the height of the cells was reduced compared to that obtained in situ.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 257 (1989), S. 61-67 
    ISSN: 1432-0878
    Keywords: Kidney ; Peripolar cells ; Renal corpuscle ; Electron microscopy ; Raja erinacea, Mustelus canis, Rhinoptera bonasus, Sphryna lewini, Rhizoprionodon terraenovae, Squalus acanthias (Elasmobranchii)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Granulated epithelial cells at the vascular pole of the renal corpuscle, peripolar cells, have been found in the kidneys of five species of elasmobranchs, the little skate (Raja erinaced), the smooth dogfish shark (Mustelus canis), the Atlantic sharpnose shark (Rhizoprionodon terraenovae), the scalloped hammerhead shark (Sphryna lewini), and the cow-nosed ray (Rhinoptera bonasus). In a sixth elasmobranch, the spiny dogfish shark (Squalus acanthias), the peripolar cells could not be identified among numerous other granulated epithelial cells. The peripolar cells are located at the transition between the parietal epithelium of Bowman's capsule and the visceral epithelium (podocytes) of the glomerulus, thus forming a cuff-like arrangement surrounding the hilar vessels of the renal corpuscle. These cells may have granules and/or vacuoles. Electron microscopy shows that the granules are membrane-bounded, and contain either a homogeneous material or a paracrystalline structure with a repeating period of about 18 nm. The vacuoles are electron lucent or may contain remnants of a granule. These epithelial cells lie close to the granulated cells of the glomerular afferent arteriole. They correspond to the granular peripolar cells of the mammalian, avian and amphibian kidney. The present study is the first reported occurrence of peripolar cells in a marine organism or in either bony or cartilagenous fish.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 40
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Pregnancy ; Electron microscopy ; Stereology ; Golden hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the hamster, the weight of the adrenal glands increases during the course of gestation, with the highest value at day 5. In comparison to non-pregnant control animals, there were no changes in the volume of the zona glomerulosa (ZG) and zona fasciculata (ZF), while the volume of the zona reticularis (ZR) increased notably. The average volume of ZG-cells rose at day 5 of pregnancy and thereafter gradually decreased to that of control hamsters. A marked drop in the volume of ZF-cells was seen at days 5 and 10 of pregnancy, whereas at day 15 the cells were larger than in controls. At day 5 of pregnancy, a conspicuous increase in the cell volume was found in ZR, followed by lower values at day 10 and again higher than in control hamsters at day 15. The total number of parenchymal cells in hamster adrenal cortex increased at day 10 of gestation, then underwent a marked decrease, reaching the control value at the final day of pregnancy; this drop was mainly due to a reduction in the number of ZF-cells. The changes in the cell volume were paralleled by rather proportional changes in the volume of the mitochondrial compartment and in the quantity of smooth endoplasmic reticulum. The volume of the lipid-droplet compartment significantly rose in the course of gestation in both ZF- and ZR-cells. The cortisol output by adrenal homogenates gradually decreased during pregnancy.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 256 (1989), S. 645-648 
    ISSN: 1432-0878
    Keywords: Mammosomatotropes ; Adenohypophysis ; Electron microscopy ; Immunohistochemistry ; Mouse (SMA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two types of mammosomatotropes (MS), the small-granule and vesicle-granule MS, were detected in mouse adenohypophysis by electron microscopy and immunohistochemistry. Both cell-types were immunoreactive to prolactin (PRL) and growth hormone (GH) antisera. The small-granule MS contained small, round, solid secretory granules about 100 nm in diameter, and were smaller than the classical GH and PRL cell-types. The vesicle-granule MS contained secretory granules like cored vesicles, and were larger than classical GH and PRL cells. Small-granule MS were immunoreactive to both PRL and GH antisera in the same region of the cell cytoplasm; the vesicle-granule MS, however, were immunoreactive to only PRL antiserum in most cytoplasmic areas, and a positive response to both PRL and GH antisera was confined to only certain small areas.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 255 (1989), S. 193-198 
    ISSN: 1432-0878
    Keywords: Mucosa-associated lymphoid tissue ; Nose ; Lymphoepithelium ; Electron microscopy ; Immunohisto-chemistry ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure and organization of paired lymphoid tissue in the nasal mucosa, situated in the transitional zone on both sides of the septal opening to the pharyngeal duct, of conventionally-housed rats was examined by light microscopy and scanning and transmission electron microscopy. Each lymphoid structure consisted of follicles containing T- and B-cell areas, and was covered with specialized epithelium. This epithelium consisted of cuboidal ciliated cells with oval nuclei parallel to the basal lamina. Goblet cells were sparse. Occasionally, islands of microvilli-bearing cells (so called membraneous or M cells) covered the lymphoid structures. M Cells were also found as single cells among the ciliated cells. The morphological characteristics and the particular localization justify the conclusion that the nasal lymphoid tissue described belongs to the mucosa-associated lymphoid tissue. It is therefore suggested that this nasal structure be designated nasal lymphoid tissue.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 43
    ISSN: 1432-0878
    Keywords: Pituitary gland ; Neural lobe ; Intermediate lobe ; Intraventricular graft ; Immunocytochemistry ; Electron microscopy ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Neurointermediate lobes from adult or 10-dayold rats were implanted by a stereotaxic procedure into the third ventricle of adult male rats, in an area close to the paraventricular nucleus. They were examined, using immunocytochemical and ultrastructural techniques, at times ranging from 1 week to 8 months. All grafts were recovered in a healthy condition although some rejection of the tissue was detected at the 1and 2-week stages. In the neural lobe, clusters of pituicytes were scattered among the loose network of capillaries, most of which had a fenestrated endothelium. The intermediate lobe remained organized in compact avascular lobules. Axons similar to those projecting into the neurointermediate lobe in situ, but also axons of other types (e.g., somatostatinergic, enkephalinergic) penetrated the grafts. Synapses with melanotrophic cells in the intermediate lobe and neurohaemal contacts in the neural lobe were frequent from 2 1/2 months after transplantation. Immunocytochemical and ultrastructural characteristics indicated intense secretory stimulation of the melanotrophic cells in the early stages. All cells enclosed in a same glandular lobule reacted in a similar manner. In later stages, when re-innervation occurred, the cells recovered their initial characteristics. The overall effect of the re-innervation of the intermediate lobe grafted in this location is inhibitory, as in the lobe in situ.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 256 (1989), S. 419-429 
    ISSN: 1432-0878
    Keywords: Kidney ; Glomerulus ; Podocytes ; Tissue culture ; Electron microscopy ; Morphometry ; Rat (Sprague Dawley)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of rat glomerular epithelial cells (podocytes) in kidney slices in vitro was examined using qualitative and quantitative electron microscopy. The kidney slices were cultured in Medium 199 with Hanks' salts in a 5% CO2/95% O2 environment for up to 14 days. Few changes in podocyte ultrastructure occurred in the first 12 h of culture, but by 24 h cell bodies were rounded, microvilli were present on all podocyte surfaces, and some foot processes had been replaced by flattened expanses of cytoplasm. These changes were more pronounced by 3 days, when some podocytes had developed pseudopodal extensions and appeared to be migrating from glomeruli onto the slice surface. Podocytes could still be identified after 8, 10 and 14 days of culture, although relatively few glomeruli remained at 14 days. Morphometric methods were used to analyse podocyte shape, volume and surface area during the first 4 days of culture. The most significant change involved loss of foot processes: the number of filtration slits per 100 μm of basement membrane decreased from 211.8 ± 15.0 (mean ± SD) at the commencement of culture, to 55.3 ± 22.6 after 2 days (P 〈 0.001). These data provide baseline information for in vitro studies on the effects of nephrotoxins on podocytes.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 164 (1989), S. 209-214 
    ISSN: 1615-6110
    Keywords: Algae ; Chrysophyceae (Synurophyceae) ; Mallomonadaceae ; Mallomonas alphaphora ; Electron microscopy ; phytoplankton ; scale-bearing flagellate ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new species ofMallomonas, M. alphaphora (Chrysophyceae), was found in freshwater ponds in the Perth region, Western Australia. It is distinguished from other species ofMallomonas by its very distinctive scale and bristle morphology and is placed in a new section,Alphaphorae, of the genusMallomonas.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 46
    Electronic Resource
    Electronic Resource
    Springer
    European journal of plastic surgery 12 (1989), S. 29-34 
    ISSN: 1435-0130
    Keywords: Revascularization ; Vessel implantation ; Bone grafts ; Corrosion casts ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The microsurgical implantation of a saphenous vascular axis into free transplanted autologous isolated rib segments in Beagle dogs led to complete revascularization of the bone after two, three and four weeks. Indian ink and Mercox-injected specimens showed a vascular network which penetrated the entire cortical layer. Semi-thin sections revealed osteoblasts and osteoclasts visible in the canals of the revascularized cortical layer, while the control specimen without vessel implantation showed nothing but ground substance. The revascularized bones did not contain any necrotic areas. The newly formed vascular system consisted of arteries, veins and their anastomoses. The veins appeared to produce a greater number of new vessels than the arteries.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    Springer
    European archives of oto-rhino-laryngology and head & neck 246 (1989), S. 428-432 
    ISSN: 1434-4726
    Keywords: Otitis media with effusion ; Mucociliary system ; Eustachian tube ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have examined the function and fine structure of the mucociliary system of the eustachian tube in an experimental study of otitis media with effusion induced by X-ray irradiation. Functional examination demonstrated that the ciliary activity was diminished in such a condition, while morphological observations showed pathological findings including compound cilia, vacuolation of ciliated cells and expansion of intercellular space. These findings show that irradiation-induced otitis media with effusion results in impairment of the mucociliary system. As evidenced by these studies, the mucociliary system in the eustachian tube has an important role in the clearance of fluid produced in the tympanic cavity as well as affording improvement in this disease.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 19-24 
    ISSN: 0009-2940
    Keywords: Bis(diorganoboryl)chalcogenides ; Pyrazaboles ; Pyrazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Neuartige Substituierte B2ElVIN2 HeterocyclenDie Bis(diorganoboryl)chalkogenide (R2B)2O [R = C2H5 (3); R2 = 1,5-C8H14 (1)], (R2B)2S [R2 = 1,5-C8H14 (5)], und (R2B)2Se [R2 = 1,5-C8H14 (7)] reagieren mit Pyrazol (Pz) und dessen Derivaten 3-Methylpyrazol (3-MePz) und Indazol (benzo-Pz) in hohen Ausbeuten (65-92%) zu stabilen 1:1-Additionsverbindungen [z. B. 2 (El = O), 4 (El = O), 6 (El = S), 8 (El = Se)]. 1H-, 13C-, 11B-NMR-Spektren und Röntgenstrukturanalysen (von 2 und 6) zeigen eine Grundstruktur mit einem zentralen B2ElN2-Heterocyclus (El = O, S, Se). Die Reaktion von 2 mit R2BH und die Thermolyse von 4 führen zu den dimeren 1-Pyrazolylboranen 9a bzw. 9b.
    Notes: The bis(diorganoboryl) chalcogenides (R2B)2O [R = C2H5 (3); R2 = 1,5-C8H14 (1)], (R2B)2S [R2 = 1,5-C8H14 (5)], and (R2B)2Se [R2 = 1,5-C8H14 (7)] react with pyrazole (Pz) and its derivatives 3-methylpyrazole (3-MePz) and indazole (benzo-Pz) to form in high yields (65-92%) stable 1:1 adducts [e.g. 2 (El = O), 4 (El = O), 6 (El = S) and 8 (El = Se)]. 1H-, 13C-, 11B-NMR spectra and X-ray analyses (of 2 and 6) show a basic structure with a central B2ElN2 (El = O, S, Se) heterocycle. The reaction of 2 with R2BH and the thermolysis of 4 give the dimeric 1-pyrazolylboranes 9a and 9b, respectively.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 31-36 
    ISSN: 0009-2940
    Keywords: Mercury - mercury contacts ; Naphthalenediylmercury compounds ; Organomercury compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Extremely Short Mercury-Mercury Contacts in peri-Dimercurated Naphthalene Compounds1-Naphthylmercury chloride (1) and 1,8-naphthalenediylbis(mercury chloride) (2) were prepared from the corresponding naphthyllithium precursors and HgCl2 in ca. 80% yield. In an alternative route, 2 can be obtained from 1,8-naphthalenediyldiboric acid anhydride and HgCl2 in 85% yield. The structure of 2·DMSO has been determined by X-ray diffraction methods. The lattice contains discrete adducts in which the two mercury atoms are bridged by the DMSO oxygen atom. The HgCl moieties are bent away from each other through distortions of the naphthalene framework and of the C—Hg—Cl axes, which results in a Hg ‥ Hg distance of 3.102(1) Å. - Symmetrization of 2, induced by treatment with NaI in aqueous ethanol, affords bis(μ-1,8-naphthalenediyl)dimercury (3). In the X-ray structure determination of this compound the shortest „non-bonding“ Hg·Hg contact reported in the literature has been detected: Hg1··Hg2 = 2.797(1) Å. The molecule also shows distortions in the naphthalene framework and in the C—Hg—C axes [C—Hg—C = 173.3(5)°].
    Notes: 1-Naphthylquecksilberchlorid (1) und 1,8-Naphthalindiylbis-(quecksilberchlorid) (2) werden aus den zugehörigen Naphthyllithium-Verbindungen und HgCl2 mit ca. 80% Ausbeute erhalten. Alternativ kann 2 auch aus 1,8-Naphthalindiyldiborsäureanhydrid und HgCl2 gewonnen werden (Ausbeute 85%). Von 2·DMSO wurde die Kristallstruktur bestimmt. Es liegen diskrete Addukte vor, in denen die beiden Hg-Atome durch das O-Atom des DMSO überbrückt werden. Die HgCl-Einheiten sind durch Verzerrungen im Naphthalingerüst, durch Winkelung der Achsen C—Hg—Cl und durch deren Auslenkung aus der Naphthalinebene voneinander weggebogen, so daß ein Hg·· Hg-Kontakt von 3.102(1) Å resultiert. - 2 symmetrisiert sich bei der Einwirkung von NaI in wäßrigem Ethanol unter Bildung von Bis(μ-1,8-naphthalindiyl)diquecksilber (3). Bei der Strukturanalyse dieser im Kristall zentrosymmetrischen Verbindung wurde der bisher kürzeste „nichtbindende“ Hg··Hg-Kontakt von 2.797(1) Å gefunden. Auch in 3 sind die C—Hg—C-Achsen abgewinkelt [C—Hg—C = 173.3(5)°], und das Naphthalingerüst ist verzerrt.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 59-61 
    ISSN: 0009-2940
    Keywords: N-Butyl-N′-dansylthiourea ; Complexing agent, fluorescent ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Butyl-N′-dansylthiourea as Fluorescent Broad-Band Complexing AgentN-Butyl-N′-dansylthiourea (2) [dansyl = 5-(dimethylamino)-1-naphthylsulfonyl] is obtained by the reaction of dansylamide (1) with butyl isothiocyanate. The compound is a stable, fluorescent complex agent for a broad spectrum of metal ions. The UV spectra and fluorescence of the ligand and some metal complexes are discussed. The fluorescence of the dansyl group is strongly affected by metal ions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 51
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 83-94 
    ISSN: 0009-2940
    Keywords: Enaminecarbaldehydes ; Enamino ketones ; hetero Diels-Alder reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Struktur von Enaminecarbaldehyden und Enamino KetonenDie Synthese der Enamincarbaldehyde 1a-s und 17a-c sowie der Enamino-Ketone 2a-k und deren N-Acyl-Derivate 19a-k und 21-t mit Elektronenacceptor-Substituenten an C-2 bzw an der CO-Gruppe wird beschrieben. Kondensation von 2-Formyl-3-oxopropansäure-methylester (13) mit Ammoniak und den Aminen 14b-s ergab die Enamincarbaldehyde 1a bzw. 1b-s in einer Ausbeute von 72-93%. Die Enamincarbaldehyde 17 konnten durch Formylierung von 15 mit dem gemischten Ameisensäureessigsäureanhydrid erhalten werden. Die Synthese der Enamino-Ketone 2a-k erfolgte mit einer Ausbeute von 61-97% durch Kondensation von Ammoniak und Aminen mit den Enolethern 24a-f, die durch Umsetzung reaktiver Acylchloride 23 mit Ethylvinyl-ether dargestellt wurden. Die für hetero-Diels-Alder-Reaktionen benötigten N-Acyl-Derivate 19a-k und 21-t wurden durch Acylierung des Enamincarbaldehyds 1a und der Enamino-Ketone 2a-k gebildet.
    Notes: The synthesis of enaminecarbaldehydes 1a-s and 17a-c as well as enamino ketones 2a-k, and their N-acyl derivatives 19a-k and 21-t with electron accepting substituents at C-2 and at the CO group, respectively, is described. Condensation of methyl 2-formyl-3-oxopropanoate (13) with ammonia and the amines 14b-s gave the enaminecarbaldehydes 1a and 1b-s, respectively, in 72-93% yield. The enaminecarbaldehydes 17 were obtained by formylation of 15 with acetic formic anhydride. The synthesis of the enamino ketones 2a-k was accomplished in 61-97% yield by reaction of ammonia and amines with the enol ethers 24a-f, which were formed by treatment of reactive acyl chlorides 23 with ethyl vinyl ether. The enaminecarbaldehyde 1a as well as the enamino ketones 2a-k could be acylated to give 19a-k and 2l-t, respectively, which can be used in the hetero Diels-Alder reaction.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 119-122 
    ISSN: 0009-2940
    Keywords: Bis(phosphonium) salts ; Pyridylphosphonium salts, tri-n-butyl- and triphenyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry of Triphenyl-(or Tri-n-butyl-)pyridylphosphonium salts, 2. - 2,4-Pyridinediylbis(phosphonium) Salts2,4-Pyridinediylbis(phosphonium) salts 1 react with nucleophiles to give 4-substituted products 6-8. Under radical reaction conditions the 5-position in 1a is attacked to yield 9. sodium azide transforms 1a into 8. This salt is used as starting material for 11. The removal of the phosphonium groups in 1 and in the resulting products can be carried out selectively.
    Notes: 2,4-Pyridindiylbis(phosphoniumsalze) 1 lassen sich mit nucleophilen Reaktionspartnern in die 4-substituierten Produkte 6-8 überführen. Unter radikalischen Bedingungen wird selektiv die 5-Position in 1a unter Bildung von 9 angegriffen. Nach Umsetzung mit Natriumazid entsteht zunächst das Salz 8, das als Ausgangsverbindung für 11 dient. Die Substitution der Phosphoniumgruppen aus den Edukten 1 und Produkten kann selektiv durchgeführt werden.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 145-149 
    ISSN: 0009-2940
    Keywords: Cycloalkenes, 1-methyl- ; Ozonolysis ; Peroxyhemiacetals, cyclic ; Rubber, natural ; Tetrahydrofurans, 2-hydroperoxy- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ozonolyses of 1-Methylcyclopentene, 1-Methylcyclobutene, 5-Hexen-2-one and Natural Rubber in the Presence of MethanolOzonolyses of 1-methylcyclopentene (8a) and of 1-methylcyclobutene (8b) in methanol proceeded in each case in the two possible directions. The resulting methoxyperoxides 13 and 14 afforded the corresponding peroxyhemiacetals 15 and 19 by intramolecular reactions of the OOH with the corresponding carbonyl groups. Ozonolysis of 1-methylcyclobutene (8b) additionally gave the corresponding ozonide 17b and 2-hydroperoxy-5-methoxy-2-methyl-as well as 5-hydroperoxy-2-methoxy-2-methyltetrahydrofuran (16b and 18b). The mode of formation of these hydroperoxy compounds has been elucidated by ozonolyses of 5-hexen-2-one (25) and of natural rubber (28) in the presence of methanol.
    Notes: Ozonolysen von 1-Methylcyclopenten (8a) und von 1-Methylcyclobuten (8b) in Methanol verliefen jeweils nach beiden möglichen Spaltungsrichtungen. Die dabei gebildeten Methoxyhydroperoxide 13 und 14 ergaben durch intramolekulare Reaktionen der OOH- mit den Carbonylgruppen die entsprechenden Peroxyhalbacetale 15 bzw. 19. Bei der Ozonolyse von 1-Methylcyclobuten (8b) wurden zusätzlich das entsprechende Ozonid 17b sowie 2-Hydroperoxy-5-methoxy-2-methyl- und 5-Hydroperoxy-2-methoxy-2-methyltetrahydrofuran (16b und 18b) gebildet. Die Bildungsweise dieser Hydroperoxy-Verbindungen wurde durch Ozonolysen von 5-Hexen-2-on (25) und von Naturkautschuk (28) im Beisein von Methanol aufgeklärt.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 169-174 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of New 3-substituted PyrrolesThe synthesis of 3-alkyl- (4), 3-(ω-bromoalkyl)- (5), 3-iodo- (6), 3-formyl- (9a), 3-acetyl-1-(triisopropylsilyl)pyrrole (9b), of 2-[1-(triisopropylsilyl)-3-pyrrolyl]-2-propanol (7), 1-(triisopropylsilyl)-3-pyrrolecarboxylic acid (8), and 7-[1-(triisopropylsilyl)-3-pyrrolyl]heptanoic acid (10) as well as the desilylation of these products to the corresponding 3-substituted pyrroles 11 is described. Intermediates in these syntheses are 1-(triisopropylsilyl)pyrrole (1), 3-bromo- (2), and 3-lithio-1-(triisopropylsilyl)pyrrole (3).
    Notes: Die Synthese von 3-Alkyl- (4), 3-(ω-Bromalkyl)- (5), 3-Iod- (6), 3-Formyl- (9a) und 3-Acetyl-1-(triisopropylsilyl)pyrrol (9b), von 2-[1-(Triisopropylsilyl)-3-pyrrolyl]-2-propanol (7), 1-(Triisopropylsilyl)-3-pyrrolcarbonsäure (8) und 7-[1-(Triisopropylsilyl)-3-pyrrolyl]heptansäure (10) sowie die Desilylierung dieser Produkte zu den entsprechenden 3-substituierten Pyrrolen 11 wird beschrieben. Zwischenstufen der Darstellung sind 1-(Triisopropylsilyl)pyrrol (1), 3-Brom- (2) und 3-Lithio-1-(triisopropylsilyl)pyrrol (3).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 223-230 
    ISSN: 0009-2940
    Keywords: Gold(I) silyl complexes ; Transition-metal silyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition-Metal Silyl Complexes, 26. - Gold(I) Silyl ComplexesComplexes of type L-Au-SiR3 with L = PR′3 or PhNC and SiR3 = Si(aryl)3, Si(SiMe3)3, or SiPh2Me are prepared by reaction of L-Au-Cl with LiSiR3. Depending on L and R, their stability decreases, in the order R′3P-Au-Si(aryl)3 〉 R′3P-Au-Si(SiMe3)3 〉 R′3P-Au-SiPh2Me ≈ PhNC-Au-SiR3. Reaction of R′3P-Au-CH3 or R′3P-Au-OAc with HSiR3 does not yield silyl complexes. However, using chlorinated silanes like HSiR2Cl, CH3/Cl or OAc/Cl exchange takes place. The Mössbauer spectrum of MePh2P-Au-SiPh3 (6) and NMR- and IR-spectroscopic investigations show that silyl groups act as strong σ donors towards the gold atom. MePh2P-Au-SiPh3 (6) and MePh2P-Au-Si(SiMe3)3 (7) have been characterized by X-ray structure analyses [Au—Si 235.4(4) and 235.6(2) pm]. The Au-Si bond in MePh2P-Au-SiPh2Tol (5) is cleaved by X2 (X = Cl, Br, I), HCl or MeI, but not by H2O or MeOH.
    Notes: Komplexe des Typs L-Au-SiR3 mit L = PR′3 oder PhNC und SiR3 = Si(aryl)3, Si(SiMe3)3 oder SiPh2Me wurden durch Umsetzung von L-Au-Cl mit LiSiR3 dargestellt. Ihre Stabilität sinkt in Abhängigkeit von L und R in der Reihenfolge R′3P-Au-Si(aryl)3 〉 R′3P-Au-Si(SiMe3)3 〉 R′3P-Au-SiPh2Me ≈ PhNC-Au-SiR3. Umsetzung von R′3P-Au-CH3 oder R′3P-Au-OAc mit HSiR3 ergibt keine Silyl-Komplexe, bei Verwendung chlorierter Silane, HSi-R2Cl, findet lediglich CH3/Cl- bzw. OAc/Cl-Austausch statt. Das Mößbauer-Spektrum von MePh2P-Au-SiPh3 (6) sowie NMR- und IR-spektroskopische Untersuchungen zeigen, daß Silylreste als starke σ-Donor-Liganden gegenüber dem Goldatom wirken. MePh2P-Au-SiPh3 (6) und MePh2P-Au-Si(SiMe3)3 (7) wurden durch Röntgenstrukturanalysen charakterisiert [Au—Si 235.4(4) und 235.6(2) pm]. Die Au—Si-Bindung in MePh2P-Au-SiPh2 Tol (5) wird durch X2 (X = Cl, Br, I), HCl oder MeI, nicht aber durch H2O oder MeOH gespalten.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 245-252 
    ISSN: 0009-2940
    Keywords: Germylenes ; Germanium nitrogen compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Germylenes with Azides: Iminogermanes, Azidogermanes, Tetrazagermoles and HexaazadigermadispirododecanesGermylenes, X2Ge, stabilized by steric blocking and/or incorporation into five-membered ring systems, react with azido compounds YN3 depending on the steric requirements of the substituents X and Y to give iminogermanes, X2Ge=NY (1, 2) azidogermanes X2Ge(N3)NY2 (6-8) tetrazagermoles, X2Ge(— NY — N =)2 (10-16), and hexaazadigermadispirododecanes, [(— NR — CH2 — CH2 — NR —)Ge(μ-NY -)]2 (17, 18). NMR (1H, 13C, 14N, 15N, and 29Si), MS data, and X-ray structure analyses of the compounds 8, 9, 16, and 18 are reported.
    Notes: Durch sterische Blockierung und/oder Einbau in fünfgliedrige Ringsysteme stabilisierte Germylene, X2Ge, reagieren mit Azidoverbindungen, YN3, in Abhängigkeit von der Raumerfüllung der Substituenten X und Y zu Iminogermanen X2 Ge=NY (1, 2), Azidogermanen, X2Ge(N3)NY2 (6′8), Tetrazagermolen, X2Ge-(-NY-N=)2 (10-16), bzw. Hexaazadigermadispirododecanen, [(—NR—CH2—CH2—NR— )Ge(μ-NY-)]2 (17, 18). NMR-(1H, 13C, 14N, 15N und 29Si), MS-Daten und Röntgenstrukturanalysen für die Verbindungen 8, 9, 16 und 18 sind angegeben.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 271-277 
    ISSN: 0009-2940
    Keywords: Chalcogenogermanes, (trifluoromethyl)- ; Disilaselenanes ; Germachalcogenanes, bis(trifluoromethyl)- ; Germanes, (trifluoromethyl)- ; Germatranes, (trifluoromethyl)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: (Trifluormethyl)germanes, III. - Preparation of New (Trifluormethyl)germanium Chalcogene CompoundsStarting with the dihalogenobis(trifluoromethyl)germanes (CF3)2-GeX2 (X = Cl, or I), halogen-chalcogen exchange leads to corresponding chalcogen derivatives of the general type [(CF3)2GeE]n (6, 7) (E = O, NH, S, or Se). The resulting compounds differ in their degree of polymerisation. [(CF3)2GeO]x and the corresponding sesquioxane [(CF3)GeO1, 5]x are highly polymeric, quite in contrast to the corresponding germathianes and -selenanes. The crystal structure of [(CF3)2GeO]x (6a) was determined by X-ray single crystal diffraction. The reaction of CF3GeCl3 with triethanolamine results in the formation of 1-(trifluoromethyl)germatrane (13). Disilaselenane (10) reacts at low temperatures with chloro-(trifluoromethyl)germanes (CF3)nGeCl4-n under retention of one Si—Se bond to give (CF3)nGe(SeSiH3)4-n (11) and H3SiCl. Compounds with n = 3 and 2 could be isolated. Exchange of iodine by ECF3 takes place with iodogermanes (CF3)nGeI4-n and Hg(ECF3)2 (E = S, Se) with formation of a complete series of (trifluoromethyl)(trifluoromethylchalcogeno)germanes (CF3)nGe-(ECF3)4-n (3, 5).
    Notes: Durch Halogen-Chalkogen-Austauschreaktionen an (CF3)2)GeX2 (X = Cl, I) wurden Bis(trifluormethyl)germachalkogenane [(CF3)2GeE]n (6, 7) E = O, NH, S, Se) von unterschiedlichem Oligomerisierungsgrad erhalten. Die Germoxane [(CF3)2GeO]x und (CF3GeO1,5)x sind im Gegensatz zu den homologen Germathianen und -selenanen polymer, wobei die Struktur von [(CF3)2GeO]x (6a) durch eine Kristallstrukturanalyse ermittelt wurde. Durch Umsetzung von CF3GeCl3 mit Triethanolamin wird 1-(Trifluormethyl)germatran (13) erhalten. Disilaselenan (10) reagiert bei tiefen Temperaturen mit den Chlor (trifluormethyl)-germanen (CF3)nGeCl4-n monofunktionell unter Erhalt einer Si—Se-Bindung zu (CF3)nGe(SeSiH3)4-n (11) und H3SiCl, von denen die Verbindungen mit n = 3 und 2 isoliert werden konnten. Reaktionen der Iodgermane (CF3)nGeI4-n(1) mit Hg(ECF3)2) (E = S, Se) führen unter Substitution des Iods gegen die ECF3-Gruppen zur vollständigen Reihe der (Trifluormethyl)(trifluormethylchalkogeno)germane (CF3)nGe(ECF3)4-n (3, 5).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 59
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 291-292 
    ISSN: 0009-2940
    Keywords: (Phthalocyaninato)copper complex, substituted with crown ethers ; Alkali metal extraction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A soluble (phthalocyaninato)copper(II) complex containing eight symmetrical benzo-15-crown-5 substituents, namely {2,3,9,10,16,17,23,24-octakis[[benzo-15-crown-5)-4′ -yl]oxymethyl]phthalocyaninato}copper(II) (2) from 1,2-bis{[benzo-15-crown-5)-4′-yl]oxymethyl}-4,5-dibromobenzene (1) and CuCN in quinoline or pyridine was synthesized. The crown-ether groups in 2 were shown to prefer intramolecular complexation with alkali metal ions.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 60
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 463-466 
    ISSN: 0009-2940
    Keywords: C—C Rotation ; Sterical hindrance by SF5 groups ; Rotational barriers ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sterical Hindrance of the C—C Rotation by two SF5 GroupsAddition of SF5Cl to SF5CH=CF2 gives products carrying two SF5 groups on one carbon atom. As a consequence, C—C single bond rotation is strongly hindered. The highest rotational barrier observed is 61.7 kJ mol-1, rotational isomers are hence detectable at room temperature.
    Notes: Die Addition von SF5Cl an SF5CH=CF2 ergibt Produkte, die zwei SF5-Gruppen an einem Kohlenstoff tragen. In diesen kommt es zu einer starken Hinderung der Rotation um die C—C-Einfachbindung. Die höchste Rotationsbarriere wird mit 61.7 kJ mol-1 gefunden, d. h. Rotationsisomere sind bei Raumtemperatur getrennt nachweisbar.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 467-472 
    ISSN: 0009-2940
    Keywords: Tetracarbonylchromium complexes ; 1,2,3,6-Tetrahydro-1,2,3,6-diphosphadiborine derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Structure, and Reactions of 1,2,3,6-Tetrahydro-1,2,3,6-diphosphadiborine DerivativesThe 1,2,3,6-tetrahydro-1,2,3,6-diphosphadiborine derivatives 3a and 3b are obtained by cyclocondensation of 1,2-bis[chloro(dialkylamino)boryl]ethenes 2 and 1,2-dipotassium 1,2-di-tert-butyldiphosphanediide. As in the case of 2,5-dihydro-1H-1,2,5-phosphadiborole derivatives 1 the temperature-dependent 1H-NMR spectra of 3b exhibit a lowered barrier of inversion at phosphorus. The X-ray structure analysis of 3b shows, that the six-membered C2B2P2 ring is nonplanar and the P atoms are coordinated pyramidally. Attempts to substitute the dialkylamino groups at the boron atoms of 3a and 3b with HCl·Et2O or tBuLi lead to cleavage of the B—P bonds. Reaction between 3a or 3b and Cr(CO)3(MeCN)3 does not result in the formation of tricarbonylchromium complexes but of tetracarbonylchromium complexes 6a and 6b with pentahapto-bonded ligands 3a and 3b.
    Notes: Die 1,2,3,6-Tetrahydro-1,2,3,6-diphosphadiborin-Derivate 3a und 3b entstehen durch Cyclokondensation aus 1,2-Bis[chlor(dialkylamino)boryl]ethenen 2 und 1,2-Dikalium-1,2-di-tert-butyldiphosphandiid. Die Temperaturabhängigkeit der 1H-NMR-Spektren von 3b dokumentiert wie bei 2,5-Dihydro-1H-1,2,5-phosphadiborol-Derivaten 1 eine erniedrigte Phosphor-Inversionsbarriere. Die Röntgenstrukturanalyse von 3b zeigt, daß der C2B2P2-Sechsring im Kristall nicht eben ist und daß die P-Atome pyramidal koordiniert sind. Versuche zur Substitution der Dialkylaminogruppen an den Boratomen von 3a und 3b mit HCl·Et2O oder tBuLi führen zur Spaltung der B—P-Bindungen. Die Umsetzung von 3a bzw. 3b mit Cr(CO)3(MeCN)3 ergibt keine Tricarbonylchrom-Komplexe, sondern die Tetracarbonylchrom-Komplexe 6a bzw. 6b, in denen die Liganden 3a und 3b pentahapto gebunden sind.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 62
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organic Synthesis via Transition Metal Complexes, 34. - Novel Formation of C=C Bonds by Condensation of Acid Amides with Carbene Complexes Involving an Insertion of C2 Units into M=C BondsCarben complexes LnM=C(OEt)C6H5 1 [LnM = Cr(CO)5, Mo(CO)5, W(CO)5] and acid amides RCH2CONMe2 2 undergo a novel condensation reaction in presence of POCl3/Et3N to give alkenyl aminocarbene complexes 3. The reaction involves an insertion of a C2 unit of 2 into the M=C bond of 1 to give a C=C bond. It can be achieved with open-chain and cyclic amides like N-methyl-2-pyrrolidone (8). the structures of the complexes have been determined spectroscopically. A mechanism of the reaction is suggested.
    Notes: Carbenkomplexe LnM=C(OEt)C6H5 1 [LnM = Cr(CO)5, Mo(CO)5, W(CO)5] lassen sich mit Säureamiden RCH2CONMe2 2 und POCl3/Et3N zu Alkenyl-Aminocarben-Komplexen 3 kondensieren. Dabei wird eine C2-Einheit von 2 in die M=C-Bindung von 1 eingeschoben und eine C=C-Bindung neu geknüpft. Die Reaktion gelingt mit offenkettigen und cyclischen Amiden wie N-Methyl-2-pyrrolidon (8). Die Strukturen der Komplexe wurden spektroskopisch ermittelt und Vorschläge zur Deutung des Reaktionsablaufs gemacht.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 63
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 711-714 
    ISSN: 0009-2940
    Keywords: Azulenes ; 1,6-Methano[10]annulenes ; 1,2,4,5-Tetrazine ; [4 + 2] Cycloadditions, „inverse“ ; Pyridazines, annulated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azulene and 1,6-Methano[10]annulene as Dienophiles in the Diels-Alder Reaction with 3,6-Bis(trifluoromethyl)-1,2,4,5-tetrazineThe LUMO-diene-controlled [4 + 2] cycloadditions of azulene (2) and 1,6-methano[10]annulene (14) with the electron-deficient s-cisfixed diazadiene system of 3,6-bis(trifluoromethyl)-1,2,4,5-tetrazine (1) are described. Contrary to expectation, 1 reacts under unusually mild conditions with 2 (or its valence tautomer 3) to yield the adduct 4 which after N2 elimination rearranges to the benzo[f]phthalazine 11. The Diels-Alder reaction of 1 with 14 (or its valence tautomer 13) leads to the annulated dihydropyridazines 15 and 16, which can be dehydrogenated by silver(I) oxide to the methano-bridged aromatic cyclodecapyridazine 17 and the olefinic phthalazino[5,6-f]phthalazine 18, respectively. Besides, the methano-bridged cyclodeca[d]pyridazine 24 is prepared.
    Notes: LUMO-Dien-kontrollierte [4 + 2]-Cycloadditionen von Azulen (2) und 1,6-Methano[10]annulen (14) an das elektronenarme, s-cis-fixierte Diazadiensystem von 3,6-Bis(trifluoromethyl)-1,2,4,5-tetrazin (1) werden beschrieben. Wider Erwarten reagiert 1 unter ungewöhnlich milden Bedingungen mit 2 (oder dessen Valenztautomerem 3) zum Addukt 4, das nach N2-Eliminierung und nachfolgender Umlagerung das Benzo[f]phthalazin 11 liefert. Die Diels-Alder-Reaktion von 1 mit 14 (oder dessen Valenztautomer 13) führt zu den beiden anellierten Dihydropyridazinen 15 und 16, die mit Silber(I)-oxid zu dem Methano-überbrückten aromatischen Cyclodecapyridazin 17 bzw. dem olefinischen Phthalazino[5,6-f]phthalazin 18 dehydriert werden können. Daneben wird das Methano-überbrückte Cyclodeca[d]pyridazin 24 dargestellt.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 715-719 
    ISSN: 0009-2940
    Keywords: Alkyne ; Carbene ; Cycloisomerization ; Pyrolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über die thermische Cycloisomerisierung langkettiger Alkylacetylene in der GasphaseDie thermische Cycloisomerisierung einiger Alkylacetylene wurde in einem Laborrohrreaktor aus Quarzglas untersucht. 1-Hexin (1) wird dabei durch 1,2-H-Verschiebung und 1,5-C,H-Insertion des intermediär gebildeten Pentylidencarbens (vgl. Schema 1) in 3-Methyl-1-cyclopenten (5) umgelagert. 5-Methyl-1-hexin (2) reagiert analog; es entsteht 3,3-Dimethyl-1-cyclopenten (6). Im Gegensatz zur Bildung von in 3-Stellung methylierten Cyclopentenen aus 1-Alkinen ensteht aus 2-Hexin (3) 1-Methyl-1-cyclopenten (7). Offenbar ist die Acetylen-Vinyliden-Umlagerung nicht auf 1,2-H-Verschiebung beschränkt. Der Mechanismus der Cycloisomerisierung von Alkylacetylenen wird durch Untersuchungen mit D-markierten Alkinen bestätigt. Die Ergebnisse lassen den Schluß zu, daß die Cycloisomerisierung ohne weiteres mit dem überwiegend nach einem Radikalketten-Mechanismus verlaufenden thermischen Zerfall konkurrieren kann.
    Notes: The thermal cycloisomerization of some alkylacetylenes was investigated in a tubular quartz reactor. At 570°C 1-hexyne (1) rearranges to 3-methyl-1-cyclopentene (5) with a selectivity of about 27 by a reaction sequence including an acetylene-vinylidene rearrangement and 1,5-C,H insertion of the intermediately formed alkylidenecarbene species. 5-methyl-1-hexyne (2) behaves analogously forming 3,3-dimethyl-1-cyclopentene (6), while 2-hexyne (3) provides 1-methyl-1-cyclopentene (7) indicating that the acetylene-vinylidene rearrangement is obviously not restricted to 1,2-H shifts. The mechanism of the cycloisomerization of alkylacetylenes is investigated by means of D-labeled parent alkynes. The results show that the unimolecular cycloisomerization via alkylidenecarbenes obviously can be an important channel despite the dominance of a radical chain course.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 745-748 
    ISSN: 0009-2940
    Keywords: Flash Pyrolysis ; Matrix IR spectroscopy ; Photolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Methoxy- und AminoisocyanatMethoxyisocyanat (1) kann durch Photolyse von Azidoameisensäure-methylester (3) oder Pyrolyse von N-Methoxycarbonyl-O-methylhydroxylamin (4) dargestellt werden. Aminoisocyanat (2) ist auf ähnliche Weise durch Photolyse von Carbamoylazid (12) und Pyrolyse von Carbazinsäure-methylester (13) oder 3,4-Diaminofurazan (14) zugänglich. Die IR-Spektren von 1 und 2, aufgenommen in einer Argon-Matrix bei 10 K, werden diskutiert.
    Notes: Methoxyisocyanate (1) can be prepared by photolysis of methyl azidoformate (3) or pyrolysis of N-methoxycarbonyl-O-methyl-hydroxylamine (4). Aminoisocyanate (2) is similarly formed on photolysis of carbamoyl azide (12) and pyrolysis of either methyl carbazate (13) or 3,4-diaminofurazan (14). The infrared spectra of 1 and 2 in an argon matrix at 10 K have been measured, and some of their properties are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 749-752 
    ISSN: 0009-2940
    Keywords: Matrix isolation ; Photochemistry ; Theoretical vibrational spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Infrarot-Spektren und Photochemie von Isodiazen und seinen deuterierten IsotopomerenDie Matrixisolation von Aminoisocyanat eröffnet einen neuen ergiebigen Weg zur Darstellung von Isodiazen (Aminonitren). Damit ist es möglich geworden, nicht nur sein IR-Spektrum eindeutig festzulegen und mit Hilfe von ab-initio-Rechnungen zu interpretieren, sondern auch seine Photochemie zu untersuchen.
    Notes: The matrix isolation of aminoisocyanate opens a new efficient route for the preparation of isodiazene (aminonitrene). Its infrared spectrum can now, with the help of ab initio calculations, be interpreted, and its photochemistry can be studied.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 795-796 
    ISSN: 0009-2940
    Keywords: Thiochalcones ; Thienylchalcones ; Fries rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four new thienylchalcones (1, 4, 5, and 6) were synthesized by condensing hydroxy-nitroacetophenones with 2-thiophene and 3-thiophenecarboxaldehydes in the presence of dilute NaOH.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 767-779 
    ISSN: 0009-2940
    Keywords: Molecular twisting ; cis-9,10-Dihydronaphthalenes, persubstituted ; Valence isomerizations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Valence Isomerizations, 17. - Persubstituted cis-9,10-Dihydronaphthalenes and their Valence IsomerizationsThe tricyclic diester 10 is available from 2-butyne in a six-step synthesis with an overall yield of 10%. Thermolysis of 10 gives the bicyclic diester 11 which upon UV irradiation yields 12 as the first persubstituted cis-9,10-dihydronaphthalene. X-ray analysis of 12 shows the molecule considerably twisted along the central bond. In addition, the planes of the ester groups are at an angle of approximately 60° to the „planes“ of the six-membered rings so that conjugation of the diene systems with the carbonyl functions is virtually interrupted, an effect which is reflected by the unusual spectroscopic properties of 12. The same structural features can be found in decamethyl-cis-9,10-dihydronaphthalene (16). When heated slightly, 12 is converted to the tetracyclic valence isomer 34. On reduction of 12 with diisobutylaluminum hydride both, dihydronaphthalene dicarbinol 25 as well as its unexpected positional isomer 26, are formed depending on the reaction conditions. Etherification of the reduction products with CH2N2/Et2O—BF3 furnishes a mixture of the three isomeric bis(methoxymethyl) compounds 31, 32 and 33. They can be separated by chromatography in the cold, but revert to the mixture of the three isomers at room temperature. We consider diradical 38 to be the intermediate of this intriguing valence isomerization.
    Notes: Der tricyclische Diester 10 ist in sechs Stufen in einer Gesamtausbeute von 10% aus 2-Butin zugänglich. Thermolyse von 10 liefert den Bicyclus 11, bei dessen UV-Bestrahlung das erste persubstituierte cis-9,10-Dihydronaphtalin 12 gebildet wird. Eine Röntgenstrukturanalyse von 12 beweist die starke Verdrillung des Moleküls um die zentrale Bindung. Die Ebenen der Ester-Gruppen stehen ungefähr in einem 60°-Winkel zu den Sechsring-„Ebenen“, so daß die Konjugation der Dien-Systeme mit den Carbonyl-Funktionen praktisch unterbrochen ist, ein Effekt, der sich in den ungewöhnlichen spektroskopischen Eigenschaften von 12 widerspiegelt. Analoge Strukturmerkmale gelten auch für das Decamethyl-cis-9,10-dihydronaphthalin (16). Bicyclus 12 wandelt sich bei leichtem Erwärmen in den valenzisomeren Tetracyclus 34 um. Reduktion von 12 mit Diisobutylaluminiumhydrid gibt je nach den Reaktionsbedingungen das Dihydronaphthalindicarbinol 25 bzw. das unerwartete Stellungsisomere 26. Veretherung der Reduktionsprodukte mit CH2N2/Et2O—BF3 liefert ein Gemisch der drei isomeren Bis(methoxymethyl)-Verbindungen 31, 32 und 33, die chromatographisch in der Kälte trennbar sind, aber schon bei Raumtemperatur wieder das Gemisch der drei Isomeren zurückbilden, wobei das Diradikal 38 als Zwischenprodukt dieser erstaunlichen Valenzisomerisierung anzunehmen ist.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 803-808 
    ISSN: 0009-2940
    Keywords: Bismuth organic compounds ; Fluorinated aromatic rings ; Square pyramidal bismuth ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structures of Pentaarylbismuth CompoundsPentaarylbismuth compounds were synthesized by the known reaction Ar3BiX2 + 2 Ar′Li → 2 LiX + BiAr3Ar′2. Whenever possible they were characterized by single-crystal X-ray structure determination. In two cases almost ideal square-pyramidal geometry was found, in a third case there were two different molecules in the unit cell, both again with square-pyramidal geometry. None of these novel bismuth pentaaryls exhibit the deep coloration and the dichroism of Bi(C6H5)5.
    Notes: Pentaarylbismut- Verbindungen wurden durch die bekannte Reaktion BiAr3X2 + 2 Ar′Li → 2 LiX + BiAr3Ar′2 hergestellt und, soweit möglich, durch Röntgenbeugung an Einkristallen strukturell untersucht. In zwei Fällen erwies sich die Struktur als nahezu ideal quadratisch-pyramidal, in einem dritten Fall wurden zwei unterschiedliche Moleküle im Kristall gefunden, die aber beide wiederum quadratisch-pyramidal sind. Keines der hier vorgestellten neuen Bismutpentaaryle zeigt die tiefe Färbung und den Dichroismus von Bi(C6H5)5.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 533-535 
    ISSN: 0009-2940
    Keywords: Free radicals ; Triphenylmethyl radicals ; ESR measurements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sterically Hindered Free Radicals, XIX. - Stable 4,4′,4″-Trisubstituted Triphenylmethyl RadicalsThe title radicals (4-R—C6H4)3C. (1), R = F, Cl, Ph, OMe, NO2, tBu, OEt, SMe, CN, CF3, have been prepared, the latter four for the first time, and the ESR spectra have been recorded. aoH, amH, and apR are listed. The intensities of the ESR signals remain constant within the accessible range of -30 to + 100°C. Within this range these radicals are kinetically stable and do not dimerize like other trityls by, e.g., α,p-, α,o-, α,α -recombinations.
    Notes: Die Titelradikale (4-R—C6H4)3C· (1), R = F, Cl, Ph, OMe, NO2, tBu, OEt, SMe, CN, CF3, wurden dargestellt, davon die vier letzten erstmalig, und mittels ESR-Spektroskopie vermessen. aoH, amH und apR werden angegeben. Die ESR-Signale bleiben im gesamten zugänglichen Temperaturbereich - 30 bis + 100°C in ihrer Intensität unverändert. Daraus folgt, daß alle diese Radikale im genannten Temperaturbereich kinetisch stabil sind, also nicht wie andere Trityle zu Dimerisierungen, etwa α,p-, α,o-, α,α-, neigen.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 71
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 523-531 
    ISSN: 0009-2940
    Keywords: Dicyclopenta-s-indacene ; 2-Osxa[3.3.3]propellane derivatives ; Pentalene derivatives ; [3.3.3]Propellane-3,7-dione ; Weiss reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Novel Products in the Weiss Reaction of 1,2-Cyclopentanedione. Improved Preparation of [3.3.3]Propellane-3,7-dioneThe reaction of 1,2-cyclopentanedione (1c, 9) with the 3-oxoglutarate 4 in methanol/water in the presence of sodium bicarbonate followed by hydrolysis and decarboxylation of the product mixture affords the oxa[3.3.3]propellane ester 11c in addition to the [3.3.3]propellanedione 6c. The alkali enolates of 4 react with 9 in boiling methanol to yield the yellow, poorly soluble alkali dihydropentalenolates 12M and the [3.3.3]propellane tetraester 5c, which on hydrolysis and decarboxylation yields 53% of 6c. The dihydropentalenol 12H equilibrates with the tautomeric β-oxodiester 13, the proportion of which increases with solvent polarity. In methanol solutions, 12H and 13 add diastereoselectively forming the dicyclopenta-s-indacene tetraester syn-14, which is derived from a novel pentacyclic ring system. The configuration of syn-14 is determined by X-ray diffraction analysis. The mechanisms of formation are discussed for 11c, 12M, and syn-14.
    Notes: Nach Umsetzung von 1,2-Cyclopentandion (1c, 9) mit dem 3-Oxoglutarsäureester 4 in Methanol/Wasser in Gegenwart von Natriumhydrogencarbonat, saurer Hydrolyse und Decarboxylierung des Produktgemischs erhält man neben dem [3.3.3]Propellandion 6c den Oxa[3.3.3]propellanester 11c. Die Alkali-Enolate von 4 reagieren mit 9 in siedendem Methanol zu den gelben, schwer löslichen Dihydropentalenolaten 12M und dem [3.3.3]Propellantetraester 5c, der nach Hydrolyse und Decarboxylierung 53% 6c ergibt. Das Dihydropentalenol 12H liegt im Gleichgewicht mit dem tautomeren β-Oxodiester 13 vor, dessen Anteil mit der Polarität des Lösungsmittels zunimmt. In Methanol addieren sich 12H und 13 diastereoselektiv und bilden den Dicyclopenta-s-indacentetraester syn-14, der sich von einem neuartigen, pentacyclischen Ringsystem ableitet. Die Konfiguration von syn-14 wird durch Röntgenstrukturbestimmung aufgeklärt. Die Mechanismen der Bildung von 11c, 12M und syn-14 werden diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 553-559 
    ISSN: 0009-2940
    Keywords: Amino acids ; Diastereoselective addition ; 1-(Methacryloyl)proline derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Amino Acids, 15. - Diastereoselective Addition of Thiocarboxylic Acids to 1-(Methacryloyl)proline and-prolinol DerivativesThiocarboxylic acids 6 add to 1-(methacryloyl)-substituted proline and prolinol derivatives stereoselectively to give the 1-[3-(acylthio)-2-methylpropionyl]proline and -prolinol derivatives 7,7′ and 9. The less soluble (2S,2′R)-diastereomers are obtained in optical yields ≥ 98% by digestion of the crude products, the configuration of which was determined by acid hydrolysis of (2S,2′R)-7,7′ to (R)-3-mercapto-2-methylpropionic acid [(R)-8]. The stereoselectivity of the additions may be explained by a sevenmembered ring intermediate with an intramolecular H bridge, to which the S-nucleophiles add preferentially to give the compounds with the (2′R)-configuration.
    Notes: Thiocarbonsäuren 6 addieren stereoselektiv mit hohen optischen Ausbeuten an 1-(Methacryloyl)-substituierte Prolin- und Prolinol-Derivate zu den 1-[3-(Acylthio)-2-methylpropionyl]prolin-und -prolinol-Derivaten 7,7′ und 9. Durch Digerieren der Rohprodukte mit Diethylether werden die schwerer löslichen (2S,2′R)-Diastereomeren in optischen Ausbeuten ≥98% erhalten, deren Konfiguration durch Acidolyse von (2S,2′R)-7,7′ zu (R)-3-Mercapto-2-methylpropansäure [(R)-8] bewiesen wurde. Die Stereoselektivität der Additionen wird über einen Siebenring mit intramolekularer H-Brücke als Zwischenstufe, an die Schwefelnucleophile bevorzugt unter Bildung der (2′R)-Konfiguration addieren, gedeutet.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 545-551 
    ISSN: 0009-2940
    Keywords: Amino acids ; Diastereoselective addition ; 1-Acryloylproline esters ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Amino Acids, 14. - Diastereoselective Addition of Benzenesulfenyl Chloride to 1-Acryloylproline Esters(S)-Proline esters (S)-1 react with acryloyl chloride (2) to give 1-acryloylproline esters (S)-3 in good yields. Addition of benzenesulfenyl chloride (6) to (S)-3 at -95°C in dichloromethane results in 1-[2-chloro-3-(phenylthio)propionyl]proline esters (2S,2′R/2S,2′S)-7. The diastereoselectivity of the addition depends on the conformer ratio 3′/3″ of the starting material (S)-3. The diastereomers are separated by MPLC. Configuration at C-2′ of the resulting main products (2S,2′S)-7 was proved by independent synthesis. The diastereoselectivity of the addition of 6 to (S)-3 is interpreted to result from formation of a complex of the benzenesulfenyl cation with the proline ester group and subsequent electrophilic addition to a thiiranium intermediate B with (2S,2′R) configuration; the (2S,2′S) diastereomeric adduct 7 then results by nucleophilic attack of chloride at C-2′ under ring opening.
    Notes: Die 1-Acryloylprolinester (S)-3 werden durch N-Acylierung der Prolinester (S)-1 mit Acryloylchlorid (2) in guten Ausbeuten hergestellt; sie addieren Benzolsulfenylchlorid (6) bei -95°C in Dichlormethan mit hoher Diastereoselektivität zu 1-[2-Chlor-3-(phenylthio)propionyl]prolinestern (2S,2′R/2S,2′S)-7, die mittels MPLC getrennt werden. Die Diastereoselektivität der Addition hängt vom Konformerenverhältnis 3′/3″ der Edukte (S)-3 ab. Der Beweis der Konfiguration an C-2′ der als Hauptprodukte anfallenden Diastereomeren (2S,2′S)-7 wird durch eine unabhängige Synthese erbracht. Die Diastereoselektivität der Addition von 6 an (S)-3 wird über eine Komplexbildung des Phenylsulfenylkations mit der Prolinestergruppe und eine sich anschließende elektrophile Reaktion zu einer Thiiranium-Zwischenstufe B mit (2S,2-R)-Konfiguration gedeutet; das (2S,2′S)-diastereomere Additionsprodukt 7 entsteht dann durch nucleophilen Angriff des Chlorids an C-2′ unter Ringöffnung.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 851-855 
    ISSN: 0009-2940
    Keywords: Diphosphines ; Tungsten - tungsten quadruple bond ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Struktur von W2Cl4{μ(iPr2PCH2CH2CH2PiPr2)}2: Eine durch sperrige, chelatisierende Diphosphane überbrückte Wolfram - Wolfram-VierfachbindungDie Reduktion von WCl4 in THF durch zwei Äquivalente Na/Hg in Gegenwart des sperrigen, chelatisierenden Diphosphinopropans iPr2PCH2CH2CH2PiPr2 (dippp) liefert den violetten, zweikernigen Komplex W2Cl4(μ-dippp)2. Der Komplex besitzt eine W-W-Vierfachbindung und β-Struktur, d.h. die chelatisierenden Diphosphinopropan-Liganden verbrücken die beiden Metall-Zentren. Die 1H-NMR-spektroskopischen Daten zeigen Tieffeldverschiebungen für die dippp-Liganden, die im Einklang mit der β-Struktur stehen. Das 31P{1H}-NMR-Spektrum besteht aus einem Singulett mit 183W-Satelliten. Die Röntgen-Stukturanalyse ergibt für die β-Struktur einen Torsionswinkel P-W-W-P von 75.9° und eine W-W-Bindungslänge von 2.297(1) Å. Aus den Molekülstruktur-Daten und den 1H-NMR-Tieffeldverschiebungen kann die diamagnetische Anisotropie χ der W-W-Vierfachbindung mit - 3000 ± 300 × 10-36 m3/Molekül abgeschätzt werden. Die für den festen Zustand beobachtete Chiralität wird auch in Lösung beibehalten.
    Notes: The reduction of WCl4 in THF by two equivalents of Na/Hg in the presence of the bulky chelating diphosphine iPr2PCH2-CH2CH2PiPr2 (dippp) generates the purple, binuclear complex W2Cl4(μ-dippp)2. The quadruply-bonded molecule has a β structure, that is, the chelating diphosphine bridges the two metal centers. 1H-NMR spectral data show downfield shifts for the ligand protons consistent with the β structure. The 31P{1H}-NMR spectrum consists of a singlet with 183W satellites. The X-ray crystal structure has a twist angle (P-W-W-P torsion angle) of 75.9°, and the W-W bond length is 2.297(1) Å. Using the solidstate data and the observed downfield shifts in the 1H-NMR spectrum, the diamagnetic anisotropy χ has been estimated as - 3000 ± 300 × 10-36 m3/molecule. The chiral structure observed in the solid phase is retained in solution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 861-864 
    ISSN: 0009-2940
    Keywords: Aminoiminophosphanes ; 1,3,2λ5,4-Thiazaphosphaboretidines ; 1,2,4,3,5-Trithiadiborolanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Characterization of 1, 3, 2λ5, 4-ThiazaphosphaboretidinesThe reaction of 1,2,4,3,5-trithiadiborolanes with silylated aminoiminophosphanes leads to the 1,3,2λ5,4-thiazaphosphaboretidines 1a-i. The formation of 1h, i is accompanied by an exchange of the substituents bonded to the N atoms. 1H-, 11B-, 13C-, 29Si-, 31P-NMR, and mass spectra are discussed.
    Notes: Die Umsetzung von 1,2,4,3,5-Trithiadiborolanen mit silylierten Aminoiminophosphanen führt zu den 1,3,2λ5,4-Thiazaphosphaboretidinen 1a-i. Die Bildung von 1h, i wird von einem Austausch der N-ständigen Substituenten begleitet. 1H-, 11B-, 13C-, 29Si-, 31P-NMR- und Massenspektren werden diskutiert.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 857-860 
    ISSN: 0009-2940
    Keywords: Alkenylboranes ; Alkenylstannanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A Convenient Route from Alkenylboranes to AlkenylstannanesAlkenyldialkylboranes 1 with various substituents at the C=C double bond, including organometallic groups such as the trimethylstannyl or trimethylsilyl group, react in hexane solution with (diethylamino)- or (dimethylamino)trimethylstannane (2) in the presence of a catalytic amount of lithium dimethyl- or diethylamide (3) to give aminodialkylboranes 4 and alkenyltrimethylstannanes 5 in high yields with retention of the configuration at the C—C double bond. With (diethylamino)trimethylplumbane (2c) the less stable alkenes 5Pb are obtained. A mechanism is proposed, and 1H-, 13C-, 29Si-, 119Sn- und 207Pb-NMR-data are reported.
    Notes: Alkenyldialkylborane 1 mit verschiedenen Substituenten an der C=C-Doppelbindung, einschließlich organometallischer Gruppen wie dem Trimethylstannyl- oder dem Trimethylsilyl-Rest, reagieren in Hexan mit (Diethylamino)- oder (Dimethylamino)trimethylstannan (2) in Gegenwart einer katalytischen Menge von Lithium-diethylamid (3b) oder -dimethylamid (3a) in hoher Ausbeute unter Beibehaltung der Konfiguration an der C—C-Doppelbindung zu den entsprechenden Alkenylstannanen 5 und Aminoboranen 4. Durch Einsatz von (Diethylamino)trimethylplumban (2c) lassen sich die weniger stabilen Alkene 5Pb erhalten. Ein Mechanismus wird vorgeschlagen, und 1H-, 13C-, 29Si-, 119Sn- und 207Pb-NMR-Daten werden mitgeteilt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1919-1924 
    ISSN: 0009-2940
    Keywords: Hydrogen transfer ; Ziegler catalysis ; Dihydroarenes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ziegler Nickel Catalysts for Hydrogen Transfer ReactionsCatalysts prepared from Ni(acac)2 and AlEt3 show high catalytic activity in the hydrogen transfer between dihydroarenes, but hardly any isomerisation and H/D scrambling is observed. The active form of the catalyst is produced only in the presence of the starting material. Kinetic experiments, especially those concerning the introduction periods and the inhibition, are indicative of a complex reaction mechanism. The first hydrogen is preferentially abstracted from the 2-position, the second with complete cis selectivity.
    Notes: Der aus Ni(acac)2 und AlEt3 dargestellte Katalysator zeigt eine hohe Aktivität beim H-Transfer zwischen Dihydroarenen, neben dem Isomerisierungen und H/D-Austausch kaum ablaufen. Die aktive Form entsteht erst in Gegenwart des Edukts. Kinetische Untersuchungen, vor allem zur Induktionsperiode und zur Hemmung, deuten auf einen komplexen Ablauf. Der Wasserstoff wird cis-selektiv abgespalten, primär bevorzugt aus der 2-Position.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 78
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1925-1927 
    ISSN: 0009-2940
    Keywords: Hydrogen transfer ; Olefin isomerization ; Cobalt complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Hydrogen Transfer Reactions, 13.  -  Catalysis of Disproportionation by (Dinitrogen)hydridotris(triphenylphosphine)cobalt(I)For both C—H activation and olefin isomerization, CoH(N2)(PPh3)3 (1) is a more powerful catalyst than the Wilkinson complex. In 1,2-dihydronaphthalene (2), a two-step cis abstraction of the hydrogen atoms is found with small regioselectivity in the first step.
    Notes: Die Aktivität des Komplexes CoH(N2)(PPh3)3 (1) liegt bei der C—H-Aktivierung deutlich höher als beim Wilkinson-Katalysator. Noch effektiver wird aber eine Olefin-Isomerisierung induziert. Die zweistufige H-Abstraktion erfolgt beim 1,2-Dihydronaphthalin (2) cis-selektiv, der Primärschritt aber kaum regioselektiv.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1935-1938 
    ISSN: 0009-2940
    Keywords: as-Triazinium salt, fused ; Ring transformation ; Solvatochromy, negative ; Zwitterion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Ringtransformation von neuen kondensierten as-Triazinium-SalzenDie Reaktion des 1,2-Diaminopyridinium-Salzes 1 mit dem Furandion 2 ergab ein Pyrido-as-triazinon 3, das zum tricyclischen Furo[2,3-e]pyrido[1,2-b]-as-triazinium-Salz 5 cyclisiert wurde. Die Reaktion von 5 mit Nucleophilen führte zu unterschiedlichen Produkten: mit wäßriger Base entstand das bicyclische Triazinon 4, mit dem Methoxid-Ion und sekundären Aminen wurden die stabilen Zwitter-Ionen 7a, b erhalten, wohingegen Ammoniak und Hydrazine unter Transformation des Furanringes die neuen tricyclischen kondensierten Pyrrole 10, 11 bzw. Pyridazine 13, 14a, b ergaben.
    Notes: The 1,2-Diaminopyridinium salt 1 was treated with furandione 2 to give pyrido-as-triazinone 3, which could be cyclized to the tricyclic furo[2,3-e]pyrido[1,2,-b]-as-triazinium salt 5. Reaction of 5 with nucleophiles resulted in different types of products. Thus, aqueous base afforded bicyclic triazinone 4, methoxide ion or secondary amine led to stable zwitterions 7a, b, whereas ammonia and hydrazines resulted in ring transformation of the furan moiety, and gave new fused tricyclic pyrroles (10, 11) and pyridazines (13, 14), respectively.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1947-1953 
    ISSN: 0009-2940
    Keywords: Enol ethers ; [n](2,4)Phloroglucinophanes ; Autoxidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations of the Autoxidation and the Rearrangement of [n](2,4)PhloroglucinophanesIn the autoxidation of [n](2,4)phloroglucinophanes 3 hydroperoxides 7 are isolated in several cases as the first oxidation products; they react to the more stable monohydroxylated compounds 8 with different rates. Acylphloroglucinophanes 5, however, react with oxygen to give the dihydroxylated compounds 9. The autoxidation rate of the phloroglucinophanes 3, 5 is markedly larger than that of diethylphloroglucinols 6. In alkaline solution the hydroxy compounds 8 rearrange to the dihydroxycyclopentenones 12; the rate of rearrangement correlates with the decrease of ring strain.
    Notes: Bei der Autoxidation von [n](2,4)Pholoroglucinophanen 3 können in einigen Fällen Hydroperoxide 7 als erste Oxidationsprodukte isoliert werden, die unterschiedlich rasch in die stabileren monohydroxylierten Verbindungen 8 übergehen. Aclphloroglucinophane 5 reagieren mit Luftsauerstoff dagegen zu den zweifach hydroxylierten Verbindungen 9. Die Geschwindigkeit der Autoxidation ist bei den Phloroglucinophanen 3, 5 deutlich größer als bei den 2,4-Diethylphloroglucinen 6. Im alkalischen Medium lagern sich die Hydroxyverbindungen 8 in die Dihydroxycyclopentenone 12 um, wobei für die Geschwindigkeit der Umlagerung eine Korrelation mit der Abnahme an Ringspannung gefunden wird.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1963-1967 
    ISSN: 0009-2940
    Keywords: Allenyl azides, ring closure of ; Propargyl azides, rearrangement, base-induced ; Triazafulvenes, nucleophilic addition to ; 1,2,3-Triazoles, preparation of ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Unsaturated Azides, 7.  -  Base-catalyzed Formation of Allenyl Azides from Propargyl Azides: New Syntheses for 1,2,3-TriazolesThe propargyl azides 10, 14, 17, 20, and 28 undergo a base-catalyzed (prototropic) rearrangement to short-lived allenyl azides. These intermediates rapidly cyclize to triazafulvenes, which can be trapped by nucleophiles (methanol, sodium hydroxide, ammonia) to give 1,2,3-triazoles. Starting with the precursors 9, 13, 16, 19, and 27 one-pot syntheses lead to the heterocycles 12, 15, 18, 21, and 29. Depending on the reaction conditions, compound 10 regioselectively yields 12c (75%) by prototropic rearrangement (path B) or by migration of the azide group (path A) the isomer 11c (62%).
    Notes: Die Propargylazide 10, 14, 17, 20 und 28 lagern sich basenkatalysiert (prototrop) zu kurzlebigen Allenylaziden um. Diese Zwischenstufen cyclisieren rasch zu Triazafulvenen, die mit Nucleophilen (Methanol, Natriumhydroxid, Ammoniak) als 1,2,3-Triazole abgefangen werden können. Ausgehend von den Vorläufern 9, 13, 16, 19 und 27 führen Eintopf-Synthesen zu den Heterocyclen 12, 15, 18, 21 und 29. In Abhängigkeit von den Reaktionsbedingungen liefert 10 über die prototrope Umlagerung (Weg B) regioselektiv 12c (75%) oder durch Azidwanderung (Weg A) die isomere Verbindung 11c (62%).
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2023-2025 
    ISSN: 0009-2940
    Keywords: Homoallylic alcohols ; [2,3] Sigmatropic rearrangement ; Stereoselective synthesis of alcohols ; [2,3] Wittig rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reductive cleavages of allyl [(phenylthio)methyl] ethers (8, 11) and an allyl [(tolylsulfonyl)methyl] ether (14) with lithium naphthalenide in THF furnish homoallylic alcohols (9, 12). The steric course of these transformations (E/Z selectivity in the case of 9, syn/anti selectivity for 12) is very similar to that of analogous Wittig-Still rearrangements.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 83
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2049-2054 
    ISSN: 0009-2940
    Keywords: Ligating properties ; Pentaphosphaferrocenes ; Sandwich and triple-decker complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Pentaphospaferrocenes as Complex LigandsThe interaction of [Cp*Fe(P5)] (1a) with [Cr(CO)5(thf)] and [Cp(CO)2Mn(thf)], respectively, affords [Cp*Fe(P5){Cr(CO)5}2] (2) as well as [Cp*Fe(P5){Mn(CO)2Cp}n] (4a-d; n = 1-4; Cp* = η5-C5Me5). Irradiation of 1 and [CpFe(C6H6)]PF6 gives the cationic 30-VE triple-decker complexes [CpFe(μ, η5-P5)Fe(C5Me4R)]PF6 (3a: R = CH3; 3b: R = C2H5; Cp = η5-C5H5). In addition to the NMR studies 2 and 3b have been characterized by X-ray structure analyses.
    Notes: Die Umsetzung von [Cp*Fe(P5)] (1a) mit [Cr(CO)5(THF)] bzw. [Cp(CO)2Mn(THF)] ergibt [Cp*Fe(P5){Cr(CO)5}2] (2) sowie [HCp*Fe(P5){Mn(CO)2Cp}n] (4a-d; 1-4; Cp* = η5-C5Me5). Aus 1 und [CpFe(C6H6)]PF6 lassen sich photochemisch die kationischen 30-VE-Tripeldeckerkomplexe [CpFe(μ, η5-P5)Fe(C5Me4R)]PF6 (3a: R = CH3; 3b: R = C2H5; Cp = η5-C5H5) aufbauen. Zusätzlich zu den NMR-spektroskopischen Studien wurden von 2 und 3b Kristallstrukturanalysen angefertigt.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1139-1145 
    ISSN: 0009-2940
    Keywords: C-(Alkylideneamino)ketene imines ; Isocyanides, C=C coupling with aminocarbene ligands ; (2-Azaallenyl)chromium complexes ; 2-Imidazolin-5-ones ; α-Amino acids ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organic Syntheses via Transition Metal Complexes, 35. - (C-Amino) Ketene Imines, 2-Imidazolin-5-ones, and α-Amino Acids from Aminocarbene Chromium Complexes and IsocyanidesC-(Alkylidenamino)ketene imines 1,4-diaza-1,2,4-pentatrienes) 8 are easily accessible by C=C coupling of isocyanides R1 - NC (2, R1 = t-C4H9, c-C5H11, CH3) with the (alkylideneamino)carbene (= 2-azaallenyl-) ligand of (6). The tendency for an insertion of 2 into M=C bonds of aminocarbene complexes strongly depends on the electronic character of the aminocarbene ligand. Electron-rich aminocarbene chromium complexes like (CO)5Cr=C(NR2)C6H5 (1, R = H, CH3), show only little tendency for an insertion but mainly give cis-(R1-NC)(CO)4Cr=C(NR2C6H5 (3) by substitution of CO. Electron-poor aminocarbene complexes like 6 (readily available on N-benzoylation of 1a) undergo a facile insertion of 2 into the M=C bond with smooth formation of 7. From 7 ketene imine 8 is spontaneously disengaged by a second equivalent of 2. The reaction works especially well with bulky isocyanides 2a, b. In the case of methyl isocyanide (2c) a [bis(imino)dihydropyrrol]chromium complex 15 is obtained as a minor product besides 8c. 15 results from a [4+1] cycloaddition of 2c at the ketene imine ligand of 7c. C-(Alkylideneamino)ketene imines 8 are easily accessible by our method. They prove to be very thermolabile in solution and spontaneously isomerize to give 2-imidazolin-5-ones 10 and C-amidoketene imines 11. Under the influence of wet silica gel keten imine derivatives 8 rapidly form α-amino acid amides 16 by hydrolysis with concomitant migration of a benzoyl group. Under the same conditions 11 also gives the „normal“ α-amino acid amides 17.
    Notes: C-(Alkylideneamino)ketenimine (1,4-Diaza-1,2,4-pentatriene) 8 wurden durch C=C-Kupplung von Isocyaniden R1-NC (2, R1 = t-C4H9, c-C5H11, CH3) mit dem (Alkylideneamino)carben-(= 2-Azaallenyl-)Ligand von (6) erstmals hergestellt. Die Bereitschaft zur Insertion von 2 in M=C-Bindungen von Aminocarbenkomplexen hängt stark von den elektronischen Eigenschaften der Aminocarbenliganden ab. Elektronenreiche (Aminocarben)chromkomplexe, wie z. B. (CO)5Cr=C(NR2)C6H5 (1, R = H, CH3), zeigen eine nur geringe Neigung zur Insertion von 2 und bilden bevorzugt cis-(R1-NC)(CO)4Cr=C(NR2C6H5 (3) unter Substitution von CO. Elektronenarme (Aminocarben)chromkomplexe hingegen, wie z. B. 6 (durch N-Benzoylierung von 1a leicht zugänglich), zeigen ausschließlich Insertion zu 7. Aus 7 wird spontan 8 freigesetzt durch Substitution mit einem zweiten Äquivalent 2. Sperrige Isocyanide 2a, c reagieren besonders einheitlich. Mit Methylisocyanid (2c) entsteht zusätzlich zu 8c der [Bis(imino)dihydropyrrol]-chromkomplex 15 unter [4+1]-Cycloaddition von 2c am Keteniminligand von 7c. C-(Alkylidenamino)ketenimine 8 sind nach unserem Verfahren einfach zugänglich; sie isomerisieren jedoch leicht zu 2-Imidazolin-5-onen 10 und C-Amidoketeniminen 11. An feuchtem Kieselgel entstehen aus 8 rasch α-Aminosäureamide 16 durch Hydrolyse unter Wanderung eines Benzoylrestes; aus 11 unter gleichen Bedingungen zusätzlich „normale“ α-Aminosäureamide 17.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2177-2181 
    ISSN: 0009-2940
    Keywords: Benzonitriles ; Hetero Diels-Alder reactions, “inverse” ; Pyrazines, annulated ; Triazines, benzofuro- and benzothieno- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Donor-Substituted Benzoitriles as Side-Chain Dienophiles in the Intramolecular [4+2] Cycloaddition with Inverse Electron DemandExpanding the scope of the intramolecular Diels-Alder reaction of 1,2,4,5-tetrazines to include donor-substituted benzonitriles as side-chain dienophiles we describe synthetic routes to novel fused heterotricycles such as the benzofuro[3,2-e]-1,2,4-triazines 11a, b and the benzothieno[3,2-e]-1,2,4-triazines 14a, b, and 17. The doubly annulated pyrazines 22 and 23 are constructed by a subsequent second intramolecular Diels-Alder cycloaddition of the benzonitrile moiety with the fused 1,2,4-triazine system, starting from 11a and 14a.
    Notes: Unter Einschluß donorsubstituierter Benzonitrile als Seitenkettendienophile haben wir die Anwendungsbreite der intramolekularen Diels-Alder-Reaktion von 1,2,4,5-Tetrazinen erweitert und beschreiben Synthesewege zu neuen anellierten Heterotricyclen wie den Benzofuro[3,2-e]-1,2,4-triazinen 11a, b und den Benzothieno[3,2-e]-1,2,4-triazinen 14a, b sowie 17. Die doppelt anellierten Pyrazine 22 und 23 lassen sich durch eine nachfolgende zweite intramolekulare Benzonitril/1,2,4-Triazin-Diels-Alder-Cycloaddition mit 11a bzw. 14a als Edukten herstellen.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2147-2157 
    ISSN: 0009-2940
    Keywords: 1,3-Dipolar cycloadditions, intramolecular ; Nitrile oxides ; Regioselectivity ; Furanophanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Intramolecular Cycloadditions with Nitrile Oxides: Investigtions towards the Synthesis of HeterophanesThe intramolecular cycloaddition reactions of the nitrile oxides 30a-d, 35, 36, and 47, obtained in situ from the 2,5-difunctional furan hydroximoyl chlorides 12a, b, 18 and the nitro compounds 9c, d, 21, 29, are described. With 30c the expected isoxazolofuranophane of type 31 is formed in acceptable yield; the additionally formed regioisomer 32c and the dimer 34c are very minor products in this case. Whereas the highest homologue 30d gives a complex product mixture with small amounts of 31 d and the macrocycle 34d as the only identified compounds, the derivatives bearing a shorter side chain (30a, b; n = 1, 2) give rise to the exclusive reaction of the dipole with a double bond of the furan system (to give 33a, b). The same behavior is observed in the case of the electronically and sterically modified dipole systems 35/36 and 47, resp.; in spite of the much more favorable conditions for the formation of cyclophanes the cycloadditions result in the exclusive formation of the heterotricycles 41, 42 and 49. Possible preparative applications of the isomeric cycloaddition compounds are discussed.
    Notes: Die intramolekularen Cycloadditionsreaktionen der aus 2,5-difunktionellen Furan-Hydroximsäurechloriden (12a, b und 18) bzw. den Nitroverbindungen 9c, d, 21 und 29 in situ hergestellten Nitriloxide 30a-d, 35, 36 und 47 werden beschrieben. Eine Reaktion zu den angestrebten Isoxazolo-furanophanen des Typs 31 verläuft für 30c in brauchbarer Ausbeute; das Regioisomere 32c sowie das Dimere 34c treten hierbei nur in geringem Maße auf. Während das höchste Homologe 30d neben 31d und dem Makrocyclus 34d hauptsächlich Zersetzungsprodukte bildet, reagieren die Derivate mit kürzerer Seitenkette (30a, b; n = 1, 2) ausschließlich unter dipolarer Addition an eine Furandoppelbindung zu 33a, b. Für n = 1 entsprechen diesem Verhalten auch die elektronisch bzw. sterisch modifizierten Dipolsysteme 35/36 und 47, die trotz günstigerer Voraussetzungen für die Cyclophanbildung nur zu den Tricyclen 41, 42 bzw. 49 reagieren. Die präparativen Anwendungsmöglichkeiten der isomeren Cycloadditionsverbindungen als Synthesezwischenprodukte werden diskutiert.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2183-2185 
    ISSN: 0009-2940
    Keywords: [4 + 2] Cycloaddition ; 3,5-Dihydroxytropone ; Singlet oxygen ; Y aromaticity ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese von 3,5-DihydroxytroponWir beschreiben eine vierstufige Synthese des bisher unbekannten 3,5-Dihydroxytropons (6), die von Tropon ausgeht und eine [4 + 2]-Cycloaddition mit Singulett-Sauerstoff einschließt.
    Notes: Starting from tropone, the hitherto unknown 3,5-dihydroxytropone (6) is prepared in a four-step synthesis including a [4 + 2] cycloaddition reaction of singlet oxygen.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2207-2208 
    ISSN: 0009-2940
    Keywords: Allenes ; Hetero Diels-Alder reactions ; Catalysis, heterogeneous ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some examples of cycloadditions of 1-ethoxy-1,2-propadiene with 1-oxa-1,3-dienes, catalyzed by acid-free silica gel, are reported.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 92
    ISSN: 0009-2940
    Keywords: Bisporphyrinates, cerium(IV) ; Lanthanoid porphyrins ; Metalloporphyrins ; Tetrapyrrole complexes, sandwich-like ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metallkomplexe mit Tetrapyrrol-Liganden, LIV.  -  Synthese, Spektren, Struktur und Redox-Chemie von Cer(VI)-Bisporphyrinaten mit gleichen und verschiedenen Porphyrin-Ringen im Sandwich-SystemWeitere symmetrische Cer(IV)-Bisporphyrinate werden aus Cer-(III)-acetylacetonat und Tetraphenylporphyrin, Tetra-p-chlorphenylporphyrin, und Hexadecahydrotetrabenzporphyrin hergestellt. Aus dem letzteren Porphyrin entsteht auch ein Biscer(III)-Tripeldecker; ein solcher bildet sich als einziges Produkt aus Octamethylporphyrin. Aus einem Gemisch zweier verschiedener Porphyrine, nämlich Octaethylporphyrin [H2(OEP)], und Tetraphenyl-porphyrin [H2(TPP)] oder Tetra-p-chlorphenylporphyrin [H2-(TClP)] erhält man neben den symmetrischen Spezies Ce(OEP)2 und Ce(TPP)2 die unsymmetrischen („gemischten“) Doppeldecker Ce(OEP)(TPP) oder Ce(OEP)(TClP), die verschiedene Porphyrin-Ringe im Sandwich-System haben und sich trennen lassen. Die Kristallstrukturanalyse von Ce(OEP)(TPP) zeigt CeIV in quadratisch-antiprismatischer Umgebung der Pyrrol-N-Atome der Porphyrin-Ringe. Während die IR- und NMR-Spektren der unsymmetrischen Doppeldecker-Überlagerungen der Spektren, die einzelnen Ringe darstellen, zeigen ihre UV/VIS-Spektren und die cyclischen Voltammogramme, daß die zwei unterschiedlichen Porphyrin-Ringe sich wie ein gemeinsames π-Elektronensystem verhalten. Die Darstellung der π-Kation-Radikal-Salze [Ce(OEP)2]-ClO4 und [Ce(OEP)(TPP)]SbCl6 wird ebenfalls beschrieben. In letzterem scheint sich das Defektelektron bevorzugt im OEP-Ring aufzuhalten.
    Notes: Further symmetrical cerium(IV) bisporphyrinates are prepared from cerium(III) acetylacetonate and tetraphenylporphyrin, tetra-p-chlorophenylporphyrin, and hexadecahydrotetrabenzporphyrin. In the latter case, a biscerium(III) triple-decker is also found which is the only product in the case of octamethylporphyrin. From a mixture of two different porphyrins, namely octaethylporphyrin [H2(OEP)] and either tetraphenylporphyrin [H2(TPP)] or tetra-p-chlorophenylporphyrin [H2(TClP)], besides the symmetrical species Ce(OEP)2 and Ce(TPP)2, the unsymmetrical (“mixed”) double-deckers Ce(OEP)(TPP) or Ce(OEP)(TClP) are obtained which have different porphyrin rings in the sandwich system and can be separated by chromatography. The crystal structure analysis of Ce(OEP)(TPP) shows CeIV in a square-antiprismatic geometry of the pyrrole N atoms of the porphyrin rings. While the IR and NMR spectra of the unsymmetrical double-deckers are superpositions of the spectra of the individual rings, their UV/VIS spectra and cyclic voltammograms indicate that the two porphyrin rings behave as a common π-electron system. The preparation of the π-cation radical salts [Ce(OEP)2]ClO4 and [Ce(OEP)(TPP)]SbCl6 is also described. In the latter, the defect electron seems to reside preferentially in the OEP ring.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2261-2264 
    ISSN: 0009-2940
    Keywords: Iron, thiocarbonyl complex ; Iron-tin bond ; NMR, 13C-, 17O-, and 119Sn ; Dynamic molecules ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Formation of Fe-Sn Bonds by the Reaction of Tris(trimethylstannyl)amine with Fe(CO)5 and Fe(CO)4CS; 13C-, 17O-, and 119Sn-NMR-Spectroscopic StudiesThe reaction between N(SnMe3)3 and Fe(CO)5 gives the known complex cis-Fe(CO)4(SnMe3)2 (1) in high yield. In the analogous reaction of Fe(CO)4CS the complex fac-Fe(CO)3(CS)(SnMe3)2 (2) is obtained together with small amounts of 1. In addition to the 13C-NMR data, the 17O- and 119Sn-NMR measurements proved particularly useful for studying the dynamic behaviour of 1 and 2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2273-2274 
    ISSN: 0009-2940
    Keywords: Fluorine, application in organometallic chemistry ; Rhenocene(V)-trichloride ; Rhenocene(VII)-dichloride trication ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dichlorobis(η5-cyclopentadienyl)rhenium(VII) Tris(hexafluoroantimonate): Synthesis of the First Rhenocene(VII) Dichloride CationRhenocene trichloride ([Cp2ReCl2]⊕ Cl⊖, 1) reacts with one equivalent of AgSbF6 and three equivalents of SbF5 to provide [Cp2ReCl2]3⊕[SbF6]⊖3 (2) in high yield. 2 contains the first rhenocene(VII) dichloride cation and is the first member of a 16-electron group-7 species of the type [Cp2MCl2]n⊕ [EF6]n⊖ (M = Ti, Zr, Hf: n = 0; M = V, Nb: n = 1; M = Mo, W: n = 2; M = Re: n = 3; E = As, Sb).
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 95
    ISSN: 0009-2940
    Keywords: Manganese complexes ; Thiophosphinito complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal-Containing Heterocycles: Preparation, Properties, Reactions, LXVII.  -  Stereochemical Impacts on the Transition of Monomeric Thiophosphinito Manganese Compounds to the Dimeric Complexes The η2-thiophosphinito manganese complexes (3d, e) and the dimeric complexes (4a-c, f) are obtained from BrMn(CO)5 (1) and the secondary phosphane sulfides R2P(S)H (2a-f) [R = Me (a), Et (b), n-Pr (c), i-Pr (d), Cy (e), Ph (f)] in the presence of the auxiliary base Et(i-Pr)2N with elimination of CO. For the kinetic stabilization of 3d, e sterically demanding substituents R at the phosphorus are suitable. The Mn—S bond in 3e is easily cleaved under CO pressure (100 bar) resulting in the formation of (5e). The reaction 3e ⇆ 5e is reversible.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2283-2287 
    ISSN: 0009-2940
    Keywords: Indium, trialkyl derivatives ; Dialkylchloroindium ; Alkyldichloroindium ; Alkylindium dialkylamides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Properties of iPr2InCl, iPrInCl2, and (iPr2InHRtBu)2The reactions of triisopropylindium (1) with half an equivalent or two equivalents of indium (III) chloride leads to iPr2InCl (2) and iPrInCl2 (3), respectively. (iPr2InNHtBu)2 (4) can be synthesized from 2 and LiNHtBu. According to NMR, IR, and RE studies, 2-4 from dimers in solution and solid state. The X-ray analysis of 4 is reported.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2311-2317 
    ISSN: 0009-2940
    Keywords: Allenes, 1,3-diamino- and 1-amino-3-thio- ; Propene iminium salts ; Propyne iminium salts ; MO calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Propyne Iminium Salts: Ambifunctional reactivity reactivity towards Sulfur and Nitrogen NucleophilesPropyne iminium ions 2a-d have been studied by both ab initio (3-21G//3-21G for 2a) and MNDO calculations (2a-d). It is found that the amino group stabilizes the propargyl cation structure at the expense of the allenyl cation structure. Furthermore, the highest positive charge density is located at the amino-substituted carbon atom.  -  Reactions of 2-propyne iminium triflates 6a, b with thiols, thiolates, morpholine, lithium morpholide, and phenylhydrazine have been investigated. C-1 attack at 6, expected under kinetically controlled conditions, is observed in a few cases only. In all other cases, products resulting from C-3 attack takes place leading either to 1,3-donorsubstituted allenes (8, 10, 12) in the absence of proton sources or to their C-2-protonated forms (9, 11, 13-15) otherwise.
    Notes: Für die Propiniminium-Ionen 2a-d werden ab-initio- (3-21G//3-21G für 2a) und MNDO-Rechnungen (2a-d) durchgeführt. Danach stabilisiert die Aminogruppe die Propargylkation- eindeutig gegenüber der Allenylkation-Struktur. Die höchste positive Ladungsdichte befindet sich am aminosubstituierten Kohlenstoffatom.  -  Umsetzungen der 2-Propiniminium-triflate 6a, b mit Thiolen, Thiolaten, Morpholin, Lithium-morpholid und Phenylhydrazin zeigen, daß nur in einigen Fällen unter kinetisch kontrollierten Bedingungen der erwartete C-1-Angriff erfolgt, ansonsten wird C-3-Angriff gefunden. Letzterer führt in Abwesenheit von Protonquellen zu 1,3-donorsubstituierten Allenen (8, 10, 12), andernfalls entstehen deren C-2-protonierte Formen (9, 11, 13-15).
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 98
    ISSN: 0009-2940
    Keywords: Diels-Alder reactions, intramolecular ; Allenecarboxyamides, N-(hetarylmethyl)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cycloadditons, 17.  -  Influence of Methyl and Phenyl Groups in the Allenic ω-Position on the Thermally Induced Isomerizations of N-[2-Furanyl-(Thienyl-, Pyrrolyl-)methyl] allenecaboxamindesThe N-(2-hetarylmethyl)-1,2-alkadienecarboxamides 9a-q were synthesized by the ylide route, and their readiness to participate in the intramolecular Diels-Alder reaction was studied. Whereas the pyrrole derivatives 9p and 9q and the thiophene derivative 9o without directly bonded phenyl nuclei only decompose, the thiophene allenes 9m and 9n form the “normal” tricycles 12a and 12b by reaction of their amide phenyl nucleus (R1 = Ph). In all N-furfurylallenecarboxamides 9a-1 the furan nucleus is involved in the intramolecular Diels-Alder reaction, irrespective of the amine substituent R1. The furan nucleus reacts in all cases with the terminal allenic double bond to form the oxatricycles 10a-1 containing a six-membered lactam moiety. Reaction with the first allenic double bond (formation of 11c, d, and g) only takes place, when the reaction with the other double bond is slowed down by one or two methyl groups in the ω-position and the formation of 11 is not prevented by a methyl group in the furan 5-position.
    Notes: Die N-(2-Heteroarylmethyl)-1,2-alkadiencarboxamide 9a-q werden auf dem Ylid-Weg synthetisiert und auf ihre Bereitschaft zur intramolekularen Diels-Alder-Reaktion untersucht. Die Pyrrolderivate 9p und 9q und das Thiophen-Derivat 9o ohne direkt gebundenen Phenylkern zeigen lediglich Zersetzung, während die Thiophen-Allene 9m und 9n durch Reaktion ihrer Amid-Phenylkerne (R1 = Ph) die „normalen“ Tricyclen 12a und 12b bilden. In allen Furfuryl-allencarboxamiden (9a-1) geht der Furankern die intramolekulare Diels-Alder-Reaktion ein, unabhängig von der Art des Aminsubstituenten R1. Der Furankern reagiert in allen Fällen mit der endständigen Doppelbindung zu den Oxatricyclen 10a-1 mit sechsgliedrigem Lactamteil. Reaktion mit der ersten allenischen Doppelbindung (s. Bildung von 11c,d und g) wird daneben nur beobachtet, wenn durch Einbau von Methyl-gruppen in die ω-Position die Reaktion mit der endständigen Doppelbindung stark verlangsamt und die Bildung von 11 nicht durch eine Methylgruppe in der Furan-5-Position verhindert wird.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2377-2389 
    ISSN: 0009-2940
    Keywords: EPC syntheses ; Δ4-1,3-Oxazoline, derivatives ; Simmons-Smith reaction ; Sakurai reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cycloadditions to the Double Bond of Methyl (R)-2-tert-Butyl-Δs4-1,3-oxazoline-3-carboxylates1The title compounds (with or without an additional substituent, such as methyl or vinyl, in the 5-position) are allowed to react with peracids (→ dihydroxy derivatives 3), with cyclopropanation reagents (such as ICH2ZnEt, N2CHCOOEt, HCBr3, or HCCl3/NaOH → products 5-9), with tetracyanoethylene and OsO4 (see four- and five-membered rings in 19, 20), with dienophiles (maleic anhydride, see 23). The double bond of the oxazolines reacts in a highly diastereoselective manner, with the attack preferred from the face of the five-membered ring remote from the tert-butyl group. Some of the products obtained undergo or are subjected to further reactions (4, 12-18, 23, 29-33). Stereochemical and synthetic aspects of the reactions are discussed.
    Notes: Die Titelverbindungen (mit und ohne zusätzliche Substituenten wie z. B. Methyl oder Vinyl in der 5-Stellung) werden mit Persäuren (→ Dihydroxyderivate 3), mit Cyclopropanierungsreagentien (wie z.B. ICH2ZnEt, N2CHCOOEt, HCBr3 oder HCCl3/NaOH → Produkte 5-9), mit Tetracyanethylen und OsO4 (→ Produkte 19-20) und mit Dienophilen (Maleinsäureanhydrid, siehe 23) umgesetzt. Die Doppelbindung der Oxazoline reagiert hoch diastereoselektiv, wobei der bevorzugte Angriff von der der tert-Butylgruppe abgewandten Seite erfolgt. Einige der erhaltenen Produkte werden weiter umgesetzt (siehe 4, 12-18, 23, 29-33). Stereochemische und synthetische Aspekte der Reaktionen werden diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 2397-2398 
    ISSN: 0009-2940
    Keywords: Nucleophilic ring opening ; Regioselectivity ; Ambident nucleophiles ; Aziridines ; Tryptamine ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions with Aziridines, 52.  -  branched-Chain Tryptamine Compounds from Indolyllithium and Activated AziridinesReaction of indolyllithium 1 with activated aziridines 2 in toluene provides the tryptamines 3 or 4 in good yields.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...