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  • Magnetic resonance imaging
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  • 2005-2009
  • 1985-1989  (3,337)
  • 1945-1949
  • 1940-1944  (1,190)
  • 1920-1924
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 299-302 
    ISSN: 1279-8517
    Keywords: Cryomicrotomy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé La réalisation de coupes congelées dont l'épaisseur varie entre 5 et 50 μm, sur prélèvements cadavériques humains frais et non décalcifiés a été mise au point en Suède par l'un des auteurs en 1983. Cette technique permet d'obtenir des images anatomiques de haute définition qui ont été corrélées avec des coupes en IRM réalisées à des intervalles de 20 μm.
    Notes: Summary The performance of frozen sections of a thickness varying between 5 and 50 μm in fresh undecalcified cadaveric human specimens was perfected in Sweden by one of the authors in 1983. This technique makes it possible to obtain anatomic images of high definition which were correlated with MRI sections made at intervals of 20 μm.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 303-314 
    ISSN: 1279-8517
    Keywords: Magnetic resonance imaging ; Ultrasonography ; Heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les auteurs présentent un travail de corrélation entre l'aspect anatomique du cœur et les images obtenues en imagerie par résonance magnétique (IRM) et en échographie. Six cœurs ont été étudiés par IRM puis découpés suivant les mêmes plans de coupe. Les résultats sont présentés et comparés aux données obtenues in vivo chez des volontaires à la fois en IRM et en échographie. La corrélation entre images IRM de pièces anatomiques et coupes anatomiques est excellente, les plus fins détails anatomiques étant reproduits. L'utilisation de coupes en double obliquité permet l'obtention d'incidences similaires à celle de l'échographie. Ces mêmes incidences peuvent être obtenues in vivo. L'étude morphologique du cœur est ainsi extrêmement précise, de même que l'étude des volumes cardiaques.
    Notes: Summary The authors present a correlation study between the anatomy of the heart and its appearance with magnetic resonance imaging (MRI) and ultrasonography (US). Six hearts were studied by MR, then sliced along the same planes. The results are presented and compared with the data obtained in volunteers by MRI and ultrasonography. The correlation between the MRI of isolated hearts and their anatomic slices is excellent, the thiniest anatomic details are reproduced. The use of double oblique slices provides incidences similar to those of ultrasonography. The same incidences can be obtained in vivo. The morphologic study of the heart by these imaging techniques is thus very precise, as well as the study of cardiac volumes.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0460
    Keywords: Neurogenic dysphagia ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Dysphagia due to CNS pathology usually stems from one of two patterns of disease: (1) bilateral corticobulbar tract dysfunction (“pseudobulbar palsy”) or (2) pontomedullary dysfunction (“bulbar palsy”). Computed tomography (CT) has proved to be useful for evaluating the brainstem in patients with neurogenic dysphagia. Nonetheless, artifacts are common in CT imaging of the posterior fossa. Also, direct sagittal imaging is not usually obtainable by CT in adult patients. Magnetic resonance imaging (MRI), in contrast to CT, simultaneously gathers sequential images in the same plane and can obtain direct reconstructions in any plane of interest. MRI has proven to be more sensitive than CT in demonstrating lesions of the brain, such as demyelinating (e.g., multiple sclerosis) and ischemic diseases, (Brant-Zawadzki et al. 1984, Bradley et al. 1984, Bydder et al. 1982, Sheldon et al. 1985) as well as neoplastic masses that may produce neurogenic dysphagia (Lee et al. 1985, Zimmerman et al. 1986). Five patients with dysphagia are reported for whom MRI was valuable in detecting and characterizing their lesions of the brainstem and the cerebral hemispheres.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 107-121 
    ISSN: 1279-8517
    Keywords: Magnetic resonance imaging ; Liver ; Topographic anatomy ; Frontal (coronal) sections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Habituellement, les coupes frontales du foie en résonance magnétique sont moins utilisées que les coupes passant par les autres plans de l'espace. Des coupes frontales du tronc en résonance magnétique intéressant le foie, réalisées chez plus de 80 patients pour des indications diverses, ont été confrontées avec des coupes frontales du tronc faites sur 10 cadavres. Un schéma général de l'anatomie du foie étudiée dans le plan frontal a été établi. Les coupes frontales en résonance magnétique permettent de faire une très bonne estimation de la morphologie et du volume du foie, et d'en reconnaître les variations individuelles. Elles montrent bien certains rapports inférieurs du foie. Surtout, les coupes frontales en résonance magnétique permettent d'identifier la plupart des principales veines du foie, veines sus-hépatiques et branches de la veine porte et de bien étudier toute la portion rétro-hépatique de la veine cave inférieure. Certaines images vasculaires sont retrouvées presque constamment d'un sujet à l'autre sur les coupes. Le foie droit se prête mieux à cette étude que le foie gauche, en raison de sa morphologie et de la disposition de ses veines. Les coupes frontales du foie en résonance magnétique représentent un moyen privilégié pour étudier l'anatomie du foie. Associées à des coupes transversales, elles permettent de préciser le siège et les rapports veineux à l'intérieur du foie d'un processus pathologique, en vue d'une hépatectomie.
    Notes: Summary In general, frontal sections of the liver in magnetic resonance imaging are used less than sections passing through other planes of space. Frontal sections of the trunk in magnetic resonance imaging involving the liver, performed in over 80 patients for various reasons, were compared with frontal sections of the trunk made in 10 cadavers. A general schema was established of the anatomy of the liver studied in the frontal plane. Frontal sections in magnetic resonance imaging make it possible to form a very good estimate of the structure and size of the liver, and to recognize individual variations. They clearly show certain inferior relations of the liver. In particular, frontal sections in magnetic resonance imaging make it possible to identify most of the main veins of the liver, the main lobar veins and branches of the portal vein, and to properly study the entire retrohepatic portion of the inferior vena cava. Some of the vascular images were found almost constantly in the sections of the various subjects. The right lobe of the liver is more accessible to such study than the left by reason of its structure and its venous arrangements. Frontal sections of the liver in magnetic resonance imaging constitute a preferential method for studying the anatomy of the liver. Together with transverse sections, they make it possible to specify the site and venous relations of a pathologic process within the liver, with a view to hepatectomy.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 9 (1987), S. 141-149 
    ISSN: 1279-8517
    Keywords: Magnetic resonance imaging ; Thoracic aorta ; Gated acquisition ; Oblique slices ; Flow Phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les auteurs présentent les résultats d'une investigation concernant l'imagerie par résonance magnétique de l'aorte thoracique d'après l'étude de huit volontaires et d'un patient suspect de maladie de Takayasu mais ayant une aorte morphologiquement normale. Des coupes axiales, frontales, sagittales et obliques ont été réalisées et les résultats morphologiques sont présentés. De plus, les principaux phénomènes de flux sont expliqués et des exemples de chacun sont montrés.
    Notes: Summary The authors present the results of magnetic resonance imaging (MRI) in the investigation of the anatomy of the thoracic aorta in a group of eight volunteers and in one patient with presumptive Takayasu's disease but with normal aorta. Transaxial, coronal, sagittal and oblique slices were made and the morphologic results are presented. Major flow phenomena are also discussed and some examples given.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1920
    Keywords: Colloid cyst of the third ventricle ; Third ventricle ; Brain tumor ; Computer tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two cases of colloid cyst of the third ventricle are reported. Their computed tomographic (CT), magnetic resonance (MR) and neuropathological features are presented. The MR findings were different in the two cases for reasons not yet fully explained, full biochemical and biophysical analyses of the cyst contents not being available. Neuropathologically, the only significant difference was the abundant presence of cholesterin crystals in the colloid of case 1 and their absence in case 2. One of our cases is also peculiar from a CT point of view, since it was primarily hypodense and did not enhance on intravenous contrast administration.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 120-126 
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Cerebral infections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 18 patients with cerebral infections were investigated with a 1.5 Tesla-Magnetom. The results are compared to CT-findings obtained at the same time. In the majority of cases (n=11) MR is superior to CT because it allows earlier detection of the disease, a more exact definition of the spread and a more detailed representation of complex inflammatory processes. MRI should rank first among all examination methods, especially in the determination of herpes simplex-encephalitis as it allows earlier detection and treatment of this disease.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Systemic lupus erythematosus ; Behcet's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We performed MR (magnetic resonance) brain imaging on 24 patients with a systemic vasculitis. MRI proved to be a sensitive method for detecting brain lesions (clinically silent or manifest) in these patients. The most frequent abnormalities were periventricular lesions seen in 12 cases. Such changes are not specific for vascular disease, and are often seen in multiple sclerosis. However, additional changes were commonly seen which suggested the correct diagnosis.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Gadolinium-DTPA (Gd-DTPA) ; Brain infarction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Five patients (1 female and 4 males) with cerebral infarction of 4 h to 27 months duration were studied 9 times with magnetic resonance (MR) using Gd-DTPA. Spin-echo (SE) MR images (MRI) were obtained before and after the administration of Gd-DTPA, and correlative CT scans were performed on the same day. In 2 cases, 4 h and 27 months after the ictus, there was no enhancement with Gd-DTPA. There was faint enhancement in 2 cases with cerebral infarction of about 24h duration and obvious enhancement in all cases in the subacute stage. Compared with enhanced CT, MR using Gd-DTPA demonstrated more obvious enhancement of infarcted areas. MR enhancement using Gd-DTPA showed a gradual increase and the accumulated Gd-DTPA in infarcted areas slowly diffused to the periphery. MR enhancement with Gd-DTPA is similar to that of enhanced CT, but may be more sensitive in the detection of blood brain barrier breakdown.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 7-9 
    ISSN: 1432-1920
    Keywords: Carotid artery ; Magnetic resonance imaging ; Blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A Siemens 0.5 Tesla Magnetic Resonance Imaging (MRI) system was used with the saddle head coil and transverse scout localization for imaging 10 normal cervical carotid artery bifurcations in the sagittal plane. Good to excellent visualization of the flow voids and vessel contours was accomplished in all cases. Careful technique and patient cooperation are required.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 127-129 
    ISSN: 1432-1920
    Keywords: Brain, diseases ; Brain, white and gray matter ; Magnetic resonance imaging ; Computed tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Twelve MR scans performed on seven patients with neurosarcoidosis are presented. The most common abnormalities were ventricular enlargement (four patients) and diffuse periventricular white matter changes (three patients). Infarcts were seen in three patients and mass lesion in one. The lesions were seen in both T1 and T2 weighted images. The results are compared with CT findings. MRI seems to be more sensitive than CT in detecting white matter changes and infarcts. Ventricular enlargement and granulomas were equally well seen with both modalities.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 246-251 
    ISSN: 1432-1920
    Keywords: Temporal bone abnormalities ; Fracture skull base ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In seven patients with temporal bone fractures examined by both CT and MRI, thin section CT proved superior to MRI in demonstrating the full extent of the fractures and the status of the ossicular chain. MR studies were able to demonstrate fractures, when these fractures contained blood or CSF, and the presence of ossicular dislocation in one case where the middle ear was completely filled with CSF or blood. Admixture of air in the middle ear gave a false impression of ossicular dislocation, while air in the fracture obscured portions of it. MR proved superior to CT in the evaluation of intracranial contents by showing 5 additional subdural hematomas, 2 epidural hematomas and 2 hemorrhagic contusions.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 277-282 
    ISSN: 1432-1920
    Keywords: Paraganglioma ; Catecholamines ; Glomus jugulare ; Sphenopalatine ganglion ; Computed tomography ; Magnetic resonance imaging ; Angiography ; Embolisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three intracranial catecholamine-secreting paragangliomas are described. They involved a glomus jugulare, a sphenopalatine ganglion and the clivus and upper cervical spine respectively. The extent of the tumours was shown by CT and MRI. They were all highly vascular with a substantial blood supply from systemic arteries which was subjected to particulate embolisation, followed in two cases by surgery. The importance of studying any tumour which could possibly be a paraganglioma for hormonal and, especially, for catecholamine secretion prior to any invasive procedure, including angiography and embolisation, is emphasised: all such procedures should be covered with catecholamine blocking agents and, in addition, carefully monitored with resuscitation facilities immediately available.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1432-1920
    Keywords: Trans-sphenoidal hypophysectomy ; Cavernous sinography ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Imaging studies in 47 patients who were to undergo trans-sphenoidal surgery were analysed with reference to the vascular structures in the parasellar region. The results of cavernous sinography, dynamic contrast enhanced Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) showed good correlation with each other and with the appearances found at operation. CT and MRI, both non-invasive investigations, are therefore reliable preliminary screening methods for identifying the small proportion of patients on whom other imaging techniques need to be performed.
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1432-1920
    Keywords: Multiple scleosis, diagnosis of ; Magnetic resonance imaging ; Vascular brain disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Disseminated lesions in the white matter of the cerebral hemispheres and confluent lesions at the borders of the lateral ventricles as seen on MRI are both considered acceptable paraclinical evidence for the diagnosis of multiple sclerosis. Similar changes are, however, also found in vascular diseases of the brain. We therefore aimed at identifying those additional traits in the infratentorial region, which in our experience are not frequently found in cerebrovascular pathology. We evaluated MR brain scans of 68 patients and found pontine lesions in 71% of cases with a clinically definite diagnosis (17 out of 24) and in 33% of cases with a probable diagnosis (14 out of 43). Lesions in the medulla oblongata were present in 50% and 16%, respectively, and in the midbrain in 25% and 7%, respectively. With rare exceptions all brainstem lesions were contiguous with the cisternal or ventricular cerebrospinal fluid spaces. In keeping with post-mortem reports the morphological spectrum ranged from large confluent patches to solitary, well delineated paramedian lesions or discrete linings of the cerebrospinal fluid border zones and were most clearly depicted from horizontal and sagittal T2 weighted SE-sequences. If there is a predilection for the outer or inner surfaces of the brainstem, such lesions can be considered an additional typical feature of multiple sclerosis and can be more reliably weighted as paraclinical evidence for a definite diagnosis.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 1432-1920
    Keywords: Positron emission tomography ; Magnetic resonance imaging ; Cerebrovascular disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Combined Positron Emission Tomography (PET) and Proton Magnetic Resonance Imaging (MRI) study were performed in six patients with chronic supratentorial stroke to investigate whether remote hypometabolic regions revealed by PET showed any abnormality on MRI. Either regional oxygen consumption (n=4) or glucose utilization (n=2) were measured using PET and the 15O steady state 18FGD technique, respectively. Four patients, with deeply located brain lesions, showed a significant metabolic reduction in the overlying cerebral cortex. In the remaining two patients, affected by a large cortical infarct, there was a significant crossed cerebellar hypometabolism. The MRI weighted by the parameters spin density (ϱ), spin lattice (T1) and spin-spin (T2) relaxation times were obtained employing various sequences in the same subjects. In no patient did the MRI show any contrast modification in these hypometabolic remote regions, suggesting that subtle loss of tissue and/or biochemical change do not underlie the reduction in metabolic rate.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Neuroradiology 29 (1987), S. 403-405 
    ISSN: 1432-1920
    Keywords: Magnetic resonance imaging ; Pelizaeus ; Merzbacher disease ; Cerebral sclerosis diffuse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Pelizaeus-Merzbacher's disease is a progressive encephalopathy with demyelination of the cerebral white matter. The diagnosis can not be made on clinical or biological grounds: pathological investigation is necessary to confirm tigroid demyelination. CT scanning failed to visualize this type of anomaly but detection is now possible with the advent of magnetic resonance imaging (MRI). The authors studied the case of a boy who, at the age of 8 presented with symptoms characteristic of the disease: rotatory nystagmus, progressive encephalopathy, and inherited X-linked recessive traits. Magnetic resonance imaging revealed a high signal in the supra-tentorial white matter and the usual contrast was inverted. The authors believe that MRI can make an important contribution to the diagnosis of the disease.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1432-2161
    Keywords: Giant cell tumor ; Bone neoplasms ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In six cases of giant cell tumor the magnetic resonance (MR) images obtained with various pulse sequences and field strengths were compared to the corresponding computed tomography (CT) scans and plain roentgenograms. MRI was superior to CT and plain films in demonstrating areas of tissue inhomogeneity within the tumor as well as soft tissue extension. CT was superior in demonstrating cortical thinning. Multiplanar imaging capability and visualization of articular cartilage may demonstrate intra-articular tumor spread. The characteristic MRI findings with short TR/TE (T1-weighting) and long TR/TE (T2-weighting) are described. We also describe one case where serial MR scans were used to assess response to therapy.
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 1432-2161
    Keywords: Magnetic resonance imaging ; Bone neoplasms ; Chondroblastoma ; Clear cell chondrosarcoma ; Iliopsoas bursa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Three cases of lytic, calcified epiphyseal lesions with plain film and computed tomography features suggestive of chondroblastoma were imaged by magnetic resonance imaging. Histopathologic correlation was obtained in each case. Two cases of chondroblastoma showed low signal intensity on both short (TR600/TE20ms) and long (TR2500/TE80ms) spin echo (SE) images. The third case, a clear cell chondrosarcoma, demonstrated increased signal intensity on moderately T2 weighted (TR2500/TE40ms) images. These findings suggest that magnetic resonance imaging may be helpful in distinguishing these lesions.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 16 (1987), S. 23-29 
    ISSN: 1432-2161
    Keywords: Osteosarcoma ; Magnetic resonance imaging ; Pulsing sequences ; Appearances and clinical value
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Early magnetic resonance (MR) experience in the evaluation of 14 consecutive long bone intramedullary osteosarcomas demonstrates the need for T1 and T2 weighted pulsing sequences in the staging of this disease. Intramedullary disease is best depicted by coronal T1 weighted pulsing sequences and subtle extra-compartmental discase by T2 weighted axial imaging. Both high intensity and low intensity intra-medullary signals were noted on T2 weighting, while all T1 weighted pulsing sequences showed intra-medullary disease to have low signal intensity. Extraosseous tumor on T2 weighting usually had a high signal, and disease extent was therefore sharply demarcated from uninvolved muscle and its relationship to vessels confidently assessed. MR appears optimally suited for local staging of osteosarcoma, further enhancing the role of radiology in planning limbsalvage surgical techniques.
    Type of Medium: Electronic Resource
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  • 21
    ISSN: 1432-2161
    Keywords: Magnetic resonance imaging ; Soft tissues, magnetic resonance studies ; Muscles, neoplasms ; Juvenile fibromatosis, magnetic resonance studies ; Sedation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report the time-dependent magnetic resonance imaging (MRI) changes that resulted from an intramuscular injection of a commonly-used pediatric sedation regimen (“DPT”). These changes at the site of injection consist of a focal abnormality characterized by a slight increase in signal intensity on T1 weighted images and markedly increased signal intensity on T2 weighted images. Alterations in signal are detectable almost immediately after the injection and progress over the first 31 hours. This abnormality, which could be mistaken for real disease, persists up to 36 days following injection.
    Type of Medium: Electronic Resource
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  • 22
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 146 (1987), S. 205-208 
    ISSN: 1432-1076
    Keywords: Lissencephaly ; Agyria ; Pachygyria ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In a patient with clinical manifestations suggestive of brain malformation, computer-assisted tomography (CT) showed lissencephaly: agyria, pachygyria, absent opercularization, and colpocephaly. The patient did not have seizures or a typical EEG of hypsarrhythmia. By magnetic resonance imaging (MRI), using a long inversion-recovery sequence, it was possible to verify the CT-findings and to demonstrate heterotopic grey matter and missing claustrum. By MRI it was much easier to estimate the altered ratio of grey and white matter. High grey-white matter contrast of inversion-recovery scans and the possibility of imaging the brain in sagittal, coronal and transverse planes make MRI the method of choice for the evaluation of lissencephaly and other brain malformations. In this case it helped to verify lissencephaly as one aspect of an unknown clinical entity of type-I-lissencephaly, defective structure of lymphatic nodes, a polyarthritis-like clinical picture, hypodontia, and flaring of the ribs.
    Type of Medium: Electronic Resource
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  • 23
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 146 (1987), S. 49-50 
    ISSN: 1432-1076
    Keywords: Intra-abdominal testis ; Localization ; Orchiopexy ; Laparoscopy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A survey was made of 30 pediatric urologists for their current practice. Localization, important for operative approach, is done by venography and arteriography; ultrasonography, computed tomography and magnetic resonance imaging; and laparoscopy, the last most often immediately before operation. The preferred operation is the long-loop was orchiopexy; two-stage orchiopexy and microsurgical autotransplantation are alternatives.
    Type of Medium: Electronic Resource
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  • 24
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neurology 234 (1987), S. 172-176 
    ISSN: 1432-1459
    Keywords: Spinal epidural lipomatosis ; Hypothyroidism ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Epidural lipomatosis usually occurs as a complication of steroid therapy. This report includes the first description of a case secondary to hypothyroidism. Adults in all age groups can be affected and present with progressive signs and symptoms of spinal cord or cauda equina compression. The dorsal aspect of the thoracic spine is most commonly involved, usually in its total extent. Spine radiographs are normal and myelography poorly delineates the nature and extent of abnormality. While computed tomography can provide information about the nature of the spinal mass, magnetic resonance imaging is the investigation of choice. Extensive decompressive laminectomy is useful but the results are variable. Correction of underlying endocrine abnormality can reverse the process. The need for early diagnosis of this disorder is therefore emphasized.
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  • 25
    ISSN: 1432-1459
    Keywords: Progressive multifocal leucoencephalopathy ; Magnetic resonance imaging ; Interferon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Progressive multifocal leucoencephalopathy was diagnosed by magnetic resonance imaging (MRI) and brain biopsy in a 44-year-old woman, for whom therapeutic trials with various antiviral agents were made. Despite early diagnosis and treatment, her neurological deterioration and extension of MRI-detectable lesions were not halted for a period of about 8 months. After the introduction of intrathecal β-interferon therapy, her neurological status and MRI findings became stable and showed minimal improvement. Early diagnosis of this fatal disorder is important and intrathecal interferon therapy should be considered.
    Type of Medium: Electronic Resource
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  • 26
    Electronic Resource
    Electronic Resource
    Springer
    Child's nervous system 3 (1987), S. 225-227 
    ISSN: 1433-0350
    Keywords: Rathke's cleft cyst ; Suprasellar cyst ; Pituitary cyst ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two cases of Rathke's cleft cyst are presented. The cysts showed as high-density lesions on plain CT with slight enhancement with contrast medium. They appeared as a hyperintense mass in the T1-weighted magnetic resonance images. Preoperative diagnosis is very important because different sellar cystic lesions require different treatment.
    Type of Medium: Electronic Resource
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  • 27
    ISSN: 1432-2161
    Keywords: Wrist ; Magnetic resonance imaging ; Surface coil ; Normal anatomy ; Cadaveric correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Magnetic resonance imaging (MRI) provided adequate depiction of carpal soft tissue structures in normal volunteers, as well as accurate anatomic correlation with cadaveric specimens. Using a high field strength system and surface coil techniques, the intricate anatomy of the wrist was best defined on long TR short TE images. However, from a practical view, T1 weighted images (TR 600 ms, TE 25 ms) were most useful because of short imaging times, satisfactory image quality, and the absence of motion artifacts. The coronal plane provided the clearest definition of important structures. Potential diagnostic limitations exist due to the inability of MRI ot clearly delineate articular cartilage, joint capsules, and small interosseous ligmaents. The presence of intra-articular fluid in both living subjects and cadaveric specimens, however, allowed for fine depiction of these structures on T2 weighted images.
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  • 28
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    Journal of neurology 234 (1987), S. 344-347 
    ISSN: 1432-1459
    Keywords: CNS vasculitis ; Small vessel ; Recurrent cerebral bleeding ; Magnetic resonance imaging ; Immunosuppressive therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A patient with CNS vasculitis limited to small vessels is described. Initial spinal cord involvement with paraparesis was followed by multifocal cerebral and cerebellar involvement, depicted by magnetic resonance imaging (MRI). She also had recurrent cerebral bleeding. A diagnosis of vasculitis was made by cerebral biopsy. Immunosuppressive therapy resulted in clinical improvement and resolution of the MRI abnormalities.
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  • 29
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    Journal of neurology 234 (1987), S. 401-407 
    ISSN: 1432-1459
    Keywords: Multiple sclerosis ; Tetraparesis ; Paraparesis ; Spinal tumour ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The clinical, neuroradiological, electrophysiological and CSF findings of seven patients with slowly progressive paraparesis or tetraparesis are presented. In all patients, the results of the tests performed, including evoked potentials, CT scanning, oligoclonal bands in the CSF and myelography, were normal or inconclusive and did not lead to the correct diagnosis of the aetiology. In contrast, magnetic resonance imaging (MRI) provided the diagnosis of the causative process: multiple sclerosis in four cases, meningioma of the craniocervical junction or upper thoracic spinal cord in two cases, and upper cervical cord low-grade astrocytoma in one case. The patients with tumour could be treated effectively. Without MRI, however, the correct diagnosis would have been delayed. T2-weighted spin-echo scans provided maximal sensitivity for the detection of MS plaques, although they lacked specificity for a special disease. Several morphological criteria during MRI were helpful in differentiating Binswanger's disease, leucodystrophy and adrenoleucodystrophy from MS. It is concluded that at present MRI is the only non-invasive test with which to screen reliably the craniocervical junction and the upper cervical level, both of which are diagnostically difficult regions. The case histories also demonstrate that MRI is essential in all patients where a full clinical evaluation of the suspected spinal segment is not possible. “Pure spinal MS” is a misleading diagnosis and should not be accepted without confirmation by MRI. MRI has to be performed early enough to permit timely treatment of spinal and brain-stem disorders.
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  • 30
    ISSN: 1432-1459
    Keywords: Syringomyelia ; Syringomyelic syndrome ; Metrizamide CT myelography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The clinical features of 31 cases of syringomyelic syndrome, confirmed by metrizamide CT myelography (CTM) or magnetic resonance imaging (MRI), were analysed. Bilateral suspended sensory disturbance, previously regarded as a characteristic feature, was encountered in only 2 cases (6.5%). Thirteen patients (41.9%) showed no motor deficits of the upper limbs and 7 patients (22.6%) did not have weakness or atrophy in any of the four extremities. Cervical segmental signs were absent in 7 cases (22.6%) and in 2 (6.5%) signs were only present in the lower limbs. Scoliosis and foot deformity, such as pes cavus or equinovarus, were seen in 17 (54.8%) and 5 cases (16.1%) respectively. These skeletal abnormalities were initial symptoms in some childhood cases. In syringomyelic syndrome, clinical features are variable with many atypical clinical manifestations, apart from the previously recognized characteristic clinical features.
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  • 31
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    Journal of neurology 235 (1987), S. 95-98 
    ISSN: 1432-1459
    Keywords: Haemangioblastoma ; Magnetic resonance imaging ; Gadolinium-DTPA ; Angio-MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Magnetic resonance imaging (MRI) patterns of 11 haemangioblastomas examined with a 1.5-T scanner are described. MRI was as effective as contrast-enhanced CT in the detection of vascular tumour components, but was less sensitive than angiography. MRI was superior to CT in delineating the exact extent of the lesions, for example contact with the arachnoid surface. Even if a cystic tumour component is absent, MRI can provide helpful criteria for differential diagnosis; in particular, T2 values allow differentiation from meningiomas. In three patients additionally administered gadolinium (Gd) diethylenetriaminepenta-acetic acid (DTPA) the angiomatous parts of the tumour showed a remarkable decrease in T1 value, but the time dependence of the enhancement was not the same as that seen in dynamic CT.
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  • 32
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    Langenbeck's archives of surgery 372 (1987), S. 952-952 
    ISSN: 1435-2451
    Keywords: Magnetic resonance imaging ; Aortic aneurysms ; Dissections ; Kernspintomographie ; Aortenaneurysmen ; Dissektionen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Um die diagnostische Wertigkeit der Kernspintomographie (KST) im Bereich der Aortenchirurgie zu überprüfen, wurden 47 Untersuchungen (22 prä-, 25 postoperativ) bei 28 Patienten mit aortalen Aneurysmen und Dissektionen durchgeführt. Präoperativ konnte die Grösse des Aneurysmas, intramuraler Thrombus, perivasculäre Strukturen, assoziierte Prozesse grösserer Gefässabgänge dargestellt werden. Nachweis einer Dissektion und Differenzierung von wahren und falschen Lumen war immer möglich. Postoperativ wurde das Operationsergebnis dokumentiert und die KST als Verlaufskontrolle eingesetzt. Aufgrund der hohen räumlichen Auflösung in jeder gewünschten Schnittebene, der Nichtinvasivität, der Vermeidung von Röntgenstrahlen und Kontrastmittel stellt die KST eine wertvolle Erweiterung des diagnostischen Instrumentariums für den Bereich aortaler Erkrankungen dar.
    Notes: Summary For diagnostic evaluation of magnetic resonance imaging (MRI) of aortic disease, 47 examinations (22 pre-, 25 postoperatively) were performed in 28 patients with aortic aneurysms and dissections. Preoperatively, the extent of the aneurysm, intramural thrombus, perivascular structures, and associated process of major side branches could be documented. Diagnosis of dissection and differentiation of true and false lumen were always possible. Postoperatively, the operative result could be imaged and MRI was used for follow-up. As there is a high spatial solution in every section desired, non-invasiveness, and no X-rays or contrast material, MRI is a valuable enrichment to the diagnostic armamentarium of aortic pathology.
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  • 33
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    European archives of oto-rhino-laryngology and head & neck 243 (1987), S. 424-428 
    ISSN: 1434-4726
    Keywords: Chondroma ; Skull base ; Nasopharynx ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We report a case of an extracranial chondroma of the skull base. This tumor occupied mainly the skull base, the nasopharynx and the parapharyngeal space. Magnetic resonance imaging was effective in diagnosis and determining the extent of the lesion. Total extirpation of the lesion was performed via an external cervical approach. A survey of the available literature revealed only three similar cases treated to date.
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  • 34
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1099-1104 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nucleophile Addition von Triorganotin-Anionen on Carbon Disulfide, IX1 - Synthesis and Complexation of Novel Triphenylstannane DithioestersThe known alkyl esters Ph3SnC(S)SR (1: R=Me, 2: R=CH2Ph) and the novel stannyl(methyl) esters (3: R=SnPh3, 4: R=CH2SnPh3) were obtained by the reaction of the dioxane adduct Ph3SnCS2Li · 2 C4H8O2 with appropriate organo(element) halides. As the first derivative of a homologous stannylalkanedithiocarboxylic acid, the 3-(triphenylstannyl)propane dithioester Ph3Sn[CH2]3C(S)SMe (5) was synthesized by Grignard reaction of (3-chloropropyl)triphenylstannane with activated magnesium (addition of anthracene, ultrasound). The new η1-coordinated pentacarbonylchromium and -tungsten complexes LM(CO)5 (1a: L=1, M=Cr; 2a: L=2, M=Cr; 2b: L=2, M=W; 3b: L=3, M=W; 5b: L=5, M=W) were prepared by modification of previously reported methods.
    Notes: Durch Umsetzen des Dioxan-Addukts Ph3SnCS2Li · 2 C4H8O2 mit geeigneten Organo(element)-halogeniden entstehen die bekannten Alkylester Ph3SnC(S)SR (1: R=Me, 2: R=CH2Ph) sowie die neuartigen Stannyl(methyl)ester (3: R=SnPh3, 4: R=CH2SnPh3). Als erstes Derivat einer homologen Stannylalkandithiocarbonsäure stellten wir den 3-(Triphenylstannyl)propandithioester Ph3Sn[CH2]3C(S)SMe (5) durch Grignard-Reaktion von (3-Chlorpropyl)triphenylstannan mit aktiviertem Magnesium (Anthracen-Zusatz, Ultraschall) dar. Durch Modifikation früher beschriebener Methoden erhielten wir die neuen, η1-koordinierten Pentacarbonylchrom- und -wolfram-Komplexe LM(CO)5 (1a: L=1, M=Cr; 2a: L=2, M=Cr; 2b: L=2, M=W; 3b: L=3, M=W; 5b: L=5, M=W).
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  • 35
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1117-1123 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Diphenylphosphane Oxide with Organodiboranes - Structure of a Zwitterionic -POB- -Compound1)(C6H5)2 (3′a), prepared from diphenylphosphane oxide (C6H5)2P(O)H (1) and activated triethylborane (2a*), reacts with tetraalkyldiboranes(6) (R2BH)2 [R=C2H5: (4a)2; R=C3H7: (4b)2] to form the BH3-addition compounds (C6H5)2P(BH3)OBR2 [R=C2H5: 3′a-BH3], [(C6H5)2P(BH3)O]2BR [R=C2H5: 5a-(BH3)2], and [(C6H5)2P(BH3)O]3B [6-(BH3)3]. The reaction of bis(9-borabicyclo[3.3.1]nonane) (4c)2 with 1 leads to (C6H5)2POBC8H14 (3′c) or 3′c-4c and (C6H5)2PH (7) or (C6H5)2PH-HBC8H14 (7-4c). The crystalline zwitterionic (C6H5)2P(H)OB[OP(BH3)(C6H5)2]3 [1-6-(BH3)3] (X-ray analysis) is isolated from the reaction of 1 with (4a)2.
    Notes: Aus Diphenylphosphanoxid (C6H5)2P(O)H (1) erhält man mit aktiviertem Triethylboran (2a*) das Derivat (C6H5)2POB(C2H5)2 (3′a). Aus 3′a sind mit Tetraalkyldiboranen(6) (R2BH)2 [R=C2H5: (4a)2; R=C3H7: (4b)2] die BH3-Additionsverbindungen (C6H5)2P(BH3)OBR2 [R=C2H5: 3′a-BH3], [(C6H5)2P(BH3)-O]2BR [R=C2H5: 5a-(BH3)2] und [(C6H5)2P(BH3)O]3B [6-(BH3)3] zugänglich. Bis(9-borabicyclo[3.3.1]nona) (4c)2 und 1 reagieren unter Bildung von (C6H5)POBC8H14 (3′c) oder 3′c-4c und (C6H5PH-HBC8H14 (7-4c). Das kristallisierte zwitterionische (C6H5)2P(H)OB[OP(BH3)-
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  • 36
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1125-1132 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure Analysis of 1,2,3,4-Tetrahydrobenzo[g]-quinoxaline-5,10-quinones2,3-Diamino-1,4-dihydroxynaphthalene reacts with different aromatic aldehydes to give 2,3-disubstituted 1,2,3,4-tetrahydrobenzo[g]quinoxaline-5,10-quinones (1-7). In the course of the reaction a new C-C bond is formed stereoselectively. The yields are in the range of 80%. The corresponding benzoquinoxalinequinone 8 with different substituents in 2- and 3-positions is formed by a two-step preparation. Oxidation of these trans products leads to the benzo[g]quinoxaline-quinones and subsequent catalytic reduction yields the cis isomers. The structures and the configuration of 1 and 9 were determined by X-ray crystallography. The conformations of the new heterocycles are discussed with respect to the results obtained in solid and liquid phase.
    Notes: 2,3-Diamino-1,4-naphthohydrochinon reagiert mit Benzaldehyden unter Cyclisierung und Protonenwanderung stereoselektiv zu 2,3-disubstituierten 1,2,3,4-Tetrahydrobenzo[g]chinoxalin-5,10-chinonen (1-7) (Ausbeuten ca. 80%). Benzochinoxalin-5,10-chinon 8, das in 2- und 3-Stellung unterschiedlich substituiert ist, wird durch eine zweistufige Reaktion erhalten. Die Anordnung der Phenylreste in 2- und 3-Stellung wird für 1 und 9 durch Röntgenstrukturanalysen ermittelt; beide Spezies liegen in trans-Konfiguration vor. Durch Oxidation zu Benzo [g]chinoxalin-chinonen und anschließende katalytische Hydrierung werden cis-Isomere erhalten. Unter Berücksichtigung der Ergebnisse aus den Kristallstruktur- und NMR-Untersuchungen werden verschiedene Konformationen diskutiert.
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  • 37
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1105-1115 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of (Organo)phosphorus-Oxygen Compounds with Diorgarno-hydro-boranes1)Trialkyl phosphites P(OR)3 [R=CH3 (2a), C2H5 (2b), CH(CH3)2 (2c), C4H9 (2d)] react with tetraalkyldiboranes(6) (R′2BH)2 [R′=C2H5 (1a)2, C3H7 (1b)2] in a temperature-dependent manner between 20 and 130°C to form the trialkyl phosphite-boranes (RO)3P-BHR′2, (RO)3P-BH2R′, and (RO)3P-BH3, which have various stabilities toward alcohols. With bis(9-borabicyclo-[3.3.1]nonane) (1c)2 the easily protolyzed addition compounds are obtained [e.g. 2a-1c, 2c-1c]. - Diorgano phosphites (RO)2P(O)H [R=CH3 (3a), C4H9 (3b), C6H5 (3c), CH2C6H5 (3d)], triorgano phosphates (RO)3PO [R=CH3 (4a), C4H9 (4b), C6H5 (4c), 2-CH3C6H4 (4d)], and the monosaccharide-diphenyl phosphates 4f, 4g, and 4h are reduced by (1a)2 or (1c)2 to give H2, PH3, and insoluble yellow phosphorus compounds, respectively. Phosphoric acid (4e), their derivatives OP(OBR2)3 [R=C2H5 (4ea), R2=C8H14 (4ec)], and phenylphosphonic acid C6H5P(O)-(OH)2 (6) are not deoxygenated at 130°C by (1a)2 to (1c)2. - Diorganophosphinic acids R2P(O)OH [R=C6H5 (5a), c-C6H11 (5b)] and phenylphosphinic acid C6H5(H)P(O)OH (5c) are reduced by (1a)2-(1c)2. Reaction of 5a with (1a)2 leads to the compounds [(C6H5)2P(BH3)O]B(C2H5)2 (8a-BH3), [(C6H5)2P-(BH3)O]BC2H5 [9a-(BH3)2], and [(C6H5)2P(BH3)O]3B [10-(BH3)3]. 5a reacts with (1c)2 under simultaneous formation of (C6H5)2PH (7) or (C6H5)2PH-HBC8H14 (7-1c) and (C6H5)2-POBC8H14 (8c) or (C6H5)2P(OBC8H14)-HBC8H14 (8c-1c). - 6 reacts with tetraethyldiboroxane (11a) to form a mixture of the oligomeric compounds -P(C6H5)(O)OB(C2H5)O]n-(6′a)n.
    Notes: Trialkylphosphite P(OR)3 [R=CH3 (2a), C2H5 (2b), CH(CH3)2 (2c), C4H9 (2d)] reagieren mit Tetraalkyldiboranen(6) (R′2BH)2 [R′=C2H5 (1a)2, C3H7 (1b)2] in Abhängigkeit von der Temperatur (20 bis 130°C) unter Bildung der gegenüber Alkoholen unterschiedlich stabilen Trialkylphosphit-Borane (RO)3P-BHR′2, (RO)3P-BH2R′ und (RO)3P-BH3. Mit Bis(9-borabicyclo-[3.3.1]nonan) (1c)2 erhält man die protolytisch leicht spaltbaren Additionsverbindungen [z.B. 2a-1c, 2c-1c]. - Diorganophosphite (RO)2P(O)H [R=CH3 (3a), C4H9 (3b), C6H5 (3c), CH2C6H5 (3d)], Triorganophosphate (RO)3PO [R=CH3 (4a), C4H9 (4b), C6H5 (4c), 2-CH3C6H4 (4d)] sowie die Monosaccharid-Phosphorsäure-diphenylester 4f, 4g und 4h werden von (1b)2 bzw. (1c)2 unter Bildung von H2, PH3 und/oder unlöslichen, gelben Phosphor-Produkten reduziert. - Phosphorsäure (4e), deren Derivate OP(OBR2)3 [R=C2H5 (4ea), R2=C8H14 (4ec)] und Phenylphosphonsäure C6H5P(O)(OH)2 (6) lassen sich von (1a)2 - (1c)2 bis 130°C nicht desoxygenieren. - Diorganophosphinsäuren R2P(O)OH [R=C6H5 (5a), c-C6H11 (5b)], Phenylphosphinsäure C6H5(H)P(O)OH (5c) werden von (1a)2 bis (1c)2 reduziert. 5a und (1a)2 bilden [(C6H5)2P(BH3)O]B(C2H5)2 (8a-BH3), [(C6H5)2P(BH3)O]2BC2H5) [9a - (BH3)2] und [(C6H5)2P(BH3)O]3B [10-(BH3)3]. Mit (1c)2 reagiert 5a unter gleichzeitiger Bildung von (C6H5)2PH (7) bzw. (C6H5)2PH-HBC8H14 (7-1c) sowie von (C6H5)2POBC8H14 (8c) bzw. (C6H5)2P(OBC8H14)-HBC8H14 (8c-1c). - 6 bildet mit Tetraethyldiboroxan (11a) ein Gemisch oligomerer - [P(C6H5)(O)OB(C2H5)O]n-Verbindungen (6′a)n.
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  • 38
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Der vinyloge Tricarbonyl-chromophor. Violerythrin-Endgruppen und verwandte Sechsringverbindungen. Synthese, Konformation, Untersuchung mit Photoelektronen-, UV-, NMR-Spektroskopie und Röntgenstrukturanalyse1)Die Synthese von ungesättigten Fünf- und Sechsringen, 3a, 4, 5b, 5c und 17a, die das Strukturelement des 3-Penten-1,2,5-trions enthalten, wird beschrieben. Diese vinylogen Tricarbonyle werden zusammen mit verwandten Verbindungen auf ihre chromophoren Eigenschaften hin untersucht. Die Konformation in Lösung, insbesondere der Torsionswinkel Ring-Seitenkette, wird mit Hilfe von 3JCH-Kopplungen, NOE-Differenzspektren und Kraftfeldrechnungen abgeleitet. Röntgenstrukturanalysen von 11a, 17a, 18a und 35 liefern die Geometrie im festen Zustand. Die Ionisierungsenergien werden photoelektronenspektroskopisch bestimmt. Zur Berechnung und Interpretation der Absorptionsspektren und der Farbe werden die CNDO/S-CI- und die HAM/3-Methode verwendet.
    Notes: The synthesis of five- and six-membered rings 3a, 4, 5b, 5c, and 17a, containing the structural moiety 3-pentene-1,2,5-trione, is described. The chromophoric properties of these vinylogous tricarbonyls together with related compounds are investigated. The conformation in solution, particularly the torsion angle ring/sidechain, can be derived from measurements of 3JCH coupling constants, NOE difference spectra, and force-field calculations. X-ray structure analyses of 11a, 17a, 18a, and 35 afford geometries in the solid state. Ionization energies are determined by means of photoelectron spectroscopy. The theoretical calculations and interpretation of absorption spectra and colour are carried out using the models CNDO/S-CI and HAM/3.
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  • 39
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1183-1190 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Element-Organic Amine/Imine Compounds, XXVIII1). - Polycyclic Phosphorus-Nitrogen Rhenium(I) ComplexesThe thermolysis of [(OC)4RE - NR - P(Cl)(NR2) - NR](2), R = SiMe3 affords the tricyclic phosphorus dispiro compound 3, the cubanelike rhenium complex [Re2(CO)6(μ3-NR)4(μ3 -PNR)2] (4) as well as the tetracyclic rhenium complex 5. The attempt to synthesize 3 from RN-P(NR)(NR2)-NR- P(NR)(NR2 (7), R=SiMe3, and [Re(CO)5X] or [(OC)4ReX]2 (X=Cl, Br), gave the ionic species [RN-(RN)(RHN)P-NR-P- NR-SiMe2-NR]⊕ [Re2(CO)6(μX)3]⊖ (6a, X=Cl; 6b, X=Br). 3, 5, and 6a have been characterized by an X-ray structure analysis.
    Notes: Die Thermolyse von [(OC)4Re-NR -P(Cl)(NR2)-NR] (2), R = SiMe3 ergibt die tricyclische Phosphor-Dispiroverbindung 3, den cubanartigen Rheniumkomplex [Re2(CO)6(μ3-PNR)2] (4) sowie den tetracyclischen Rheniumkomplex 5. Beim Versuch, 3 aus RN-P(NR)(NR2)-NR -P(NR)(NR2) (7), R = SiMe3 und [Re(CO)5X] bzw. [(OC)4ReX]2 (X=Cl, Br) herzustellen, bildeten sich die Komplexsalze [RN- (RN)(RHN)P-NR-SiMe2-NR[⊕ [Re2(CO)6(μX)]⊖ (6a, X = Cl; 6b, X = Br). 3, 5 und 6a wurden durch eine Röntgenstrukturanalyse charakterisiert.
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  • 40
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1151-1173 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Dibenzocyclooctene-, Dibenzochalcocine- and Diarenochalconinediones2,2′-Oxybis-, -thiobis-, and -methylenebisbenzoic esters 2a-c react with methyllithium in ether to give low yields of 5H-dibenzo[b,g]chalcocine-5,7(6H)-diones 6a, 7a, and dibenzo[a,d]cyclooctene-5,7(6H,12H)-dione (8), respectively. Very good yields of such heterocycles with oxygen (6a-h, 37), sulfur (7a-h, 38) and selenium (36) as key atom are obtained when diaryl ethers (21, 22, 25), -sulfides (27, 29, 30), and -selenides (33) that contain 2′ -acetyl- (or -propionyl-) and 2-methoxycarbonyl groups are treated with sodium hydride in boiling toluene. Analogously are prepared the dibenz[b,g]oxonine-11,13(6H,12H)-diones 62a-c and 7H-benzo[h]naphtho[1,8-bc]thionine-7,9-(8H)-dione (65) which are expanded by one ring member. In the analogous reaction of a corresponding benzophenone derivative 35, spiro[1H-indene-1,1′(3′H)-isobenzofuran]-3(2H),3′- dione (41) is formed in a tandem reaction. - Under phase transfer conditions the dibenzochalcocinediones 6, 7, 36 and also the corresponding nitrogen cycles 5 react to give mixtures of C-(42-45) and O-alkyl derivatives (46-49). Methyllithium and diisobutylaluminium hydride provide the carbinols 50-54. With bromine and SO2Cl2, respectively, the methylene group is mono- or dihalogenated to the products 56, 57; defined nitration was only possible for the oxacycle 6a.
    Notes: Die 2,2′-Oxybis-, -Thiobis- und -Methylenbisbenzoesäureester 2a-c reagieren mit Methyllithium in Ether in schlechten Ausbeuten zu den 5H-Dibenzo[b,g]chalcocin-5,7(6H)-dionen 6a, 7a bzw. Dibenzo[a,d]cycloocten-5,7(6H,12H)-dion (8). Sehr gute Ausbeuten an derartigen Heterocyclen mit Sauerstoff (6a-h, 37), Schwefel (7a-h, 38) und Selen (36) als Schlüsselatom erhält man bei der Umsetzung von mit 2′-Acetyl- (bzw. -Propionyl-) und 2-Methoxycarbonyl-Gruppen versehenen Diarylethern (21, 22, 25), -sulfiden (27, 29, 30) und -seleniden (33) mit Natriumhydrid in siedendem Toluol. In analoger Weise lassen sich die um ein Ringglied erweiterten Dibenz[b,g]oxonin-11,13(6H,12H)-dion 62a-c und das 7H-Benzo[h]naphtho[1,8-bc]thionin-7,9(8H)-dion (65) herstellen. Bei der analogen Umsetzung eines vergleichbaren Benzophenonderivates 35 wird in einer Tandemreaktion Spiro[1H-inden-1,1′(3′H)-isobenzofuran]-3(2H),3′-dion (41) gebildet. - Unter Phasentransfer-Bedingungen lassen sich die Dibenzochalcocindione 6, 7, 36 sowie die entsprechenden Stickstoffcyclen 5 zu Gemischen von C-(42-45) und O-Alkylderivaten (46-49) umsetzen. Methyllithium bzw. Diisobutylaluminiumhydrid liefern die Carbinole 50-54. Mit Brom bzw. SO2Cl2 werden die an der Methylengruppe mono- oder dihalogenierten Produkte 56, 57 erhalten; definiert nitrieren ließ sich nur der Oxacyclus 6a.
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  • 41
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1175-1182 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thiastannacyclohexanes (R2SnS)3 and -adamantanes (RSn)4S5: Synthese, Properties, and StructuresCyclotristannathianes (4) are obtained from R2SnCl2 (1) and Na2S · 9H2O or (CH3)3SiSSi(CH3)3. Analogously, hexathiatetrastannaadamantanes are prepared from RSnCl3 (2) and the sulfenylating agents mentioned before. The reaction between dimesityltin dichloride (1a) and Na2S · 9H2O depending on the reaction conditions yields either the corresponding dithiadistannacyclobutane (3) or cyclotristannathiane 4a. The structure of the cyclostannathianes 3, 4, and 5 are elucidated by determining the intensity ratio of geminal 119Sn-117Sn couplings. Calculated data are confirmed by experimental values. Additional proof is provided by measuring the change of intensity ratio in the 117Sn-NMR spectrum of 4c. X-ray structure determination proved for (C6F5Sn)4S6 (5g) to have the same geometry as in solution.
    Notes: Cyclotristannathiane (4) werden durch Umsetzung von R2SnCl2 (1) mit Na2S · 9H2O bzw. (CH3)3 erhalten. Analog werden Hexathiatetrastannaadamantane (5) aus RSnCl3 (2) und obigen Sulfenylierungsagentien synthetisiert. Die Reaktion zwischen Dimesitylzinndichlorid (1a) und Na2S · 9H2O führt je nach Reaktionsbedingungen entweder zum entsprechenden Dithiadistannacyclobutan (3) oder zu Cyclotristannathian 4a. Die Konstitutionen der Cyclostannathiane 3, 4 und 5 wurden durch Intensitätsmessungen der geminalen 119Sn-117Sn-Kopplung ermittelt. Berechnete Werte ließen sich experimentell bestätigen. Die Beweisführung wird im Fall von 4c durch die im 117Sn-NMR-Spektrum aufgezeigte Intensitätsveränderung ergänzt. Die an (C6F5Sn)4S6 (5g) durchgeführte Röntgenstrukturanalyse belegt die in Lösung aufgezeigte Geometrie.
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  • 42
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1183-1190 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Element-Orgainc Amine/Imine compounds, XXVII1). - Polycyclic Phosphorus-Nitrogen Rhenium(I) ComplexesThe amine-stabilized sulfimides RN=SO2 Ň7H13 8, 9, and 10 could be obtained by reaction of sulfamoyl chlorides RNH-SO2Cl [R=C6F5 4, (CF3)2CH 5, (CF3)2CHOCO 6] with quinuclidine (7). A direct approach to 8 and 15 was found by oxidation of N-sulfinylamines RN=SO [R=C6F5 12, (CF3)2CF 14] with quinuclidine N-oxide or trimethylamine N-oxide, respectively. The X-ray structure analysis of 8 indicates a doublebond in the N=SO2 group, while the amine is tetrahedrally coordinated in a distance to the sulfur atom longer than a single bond. Additional reaction of N-sulfinylamines or sulfamoyl chlorides are reported.
    Notes: Die aminstabilisierten Sulfimide RN=SO2Ň7H13 8, 9 und 10 konnten durch Reaktion der Sulfamoylchloride RNH-SO2Cl [R=C6F5 4, (CF3)2CH 5, (CF3)2CHOCO 6] mit Chinuclidin (7) erhalten werden. Ein direkter Zugang zu 8 und 15 wurde durch Oxidation der N-Sulfinylamine RN=SO [R=C6F5 12, (CF3)2CF 14] mit Chinuclidin-N-oxid bzw. Trimethylamin-N-oxid gefunden. Die Röntgenstrukturanalyse an 8 weist auf eine Doppelbindung in der N=SO2-Gruppe hin, während das Amin tetraedrisch in einem Abstand zum Schwefelatom koordiniert ist, der länger als einer Einfachbindung entsprechend ist. Weitere Reaktionen von N-Sulfinylaminen bzw. Sulfamoylchloriden werden beschrieben.
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  • 43
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 55-59 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of N-methyl- and N-benzyl-substituted 5-oxoproline methylesters (1a, b) with thionyl or oxalyl chloride yield N-substituted 5-chloro-2,3-dihydro-1H-pyrrole-2-carboxylic esters. These esters, as α-chloro enamines, undergo further electrophilic reaction in the ß-position by thionyl or oxalyl chloride. Thus, N-substituted bis(pyrrolyl) thioethers 2, bis(pyrrolyl) disulfides 3, and their oxidation products 4,5, and 6 are formed with excess thionyl chloride. N-substituted 5-chloro-4-[chloro(chlorocarbonyl)methyl]-1H-pyrrole-2-carboxylic esters 12 are obtained with oxalyl chloride. Reaction of L-1-benzhydryl-5-oxoproline methylester (L-1c) with thionyl chloride results in the formation of N-unsubstituted bis(pyrrolyl) thioether 9 under comparable conditions.
    Notes: N-Methyl- und N-Benzyl-substituierte 5-Oxoprolin-methylester (1a, b) bilden mit Thionyl- bzw. Oxalychlorid N-substituierte 5-Chlor-2,3-dihydro-1H-pyrrolcarbonsäureester, die als α-Chlor-enamine in ß-Position elektrophil mit Thionylchlorid bzw. Oxalylchlorid weiterreagieren: mit Thionylchlorid zu N-substituierten Bis(pyrrolyl)thioethern 2 und Bis(pyrrolyl)disulfiden 3 sowie deren Oxidationsprodukten 4, 5 und 6, mit Oxalylchlorid zu N-substituierten 5-Chlor-4-[chlor(chlorcarbonyl)methyl]-1H-pyrrol-2-carbonsäureestern 12. Die Umsetzung von L-1-Benzhydryl-5-oxo-prolin-methylester (L-1c) mit Thionylchlorid führt unter vergleichbaren Bedingungen zum N-unsubstituierten Bis(pyrrolyl)thioether 9.
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  • 44
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 67-70 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thioethers 3 and monothioacetals 4 are obtained on cathodic reduction of thiopivalophenone (2) in alcohols as solvents in the presence of alkylating agents.
    Notes: Bei der kathodischen Reduktion von Thiopivalophenon (2) in Alkoholen als Lösungsmittel in Gegenwart von Alkylierungsmitteln erhält man neben den Thioethern 3 die Monothioacetale 4.
    Additional Material: 1 Ill.
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  • 45
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 79-80 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: LiAlH4 reduction of ketone 1 which adopts a norcaradiene form leads to the alcohol 2. Ketone 1 may also be converted into the alkene 3 using McMurry conditions. Both reactions are accompanied by valence isomerisations to a bi- or tetracycloheptatriene
    Notes: Das als Norcaradien-Isomere vorliegende Keton 1 läßt sich durch Reduktion mit LiAlH4 in den Alkohol 2 und unter McMurry-Bedingungen in das Alken 3 überführen dabei beobachteten wir Valenzisomerisierung zu einem Bi- bzw. Tetra(cycloheptatrein)-System.
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  • 46
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 89-91 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Starting from 1,4-bis-(3-iodopropyl)-2,5-dimethoxybenzene (3) via the reaction to the corresponding bis(1,3-dithian-2-yl) compound 4 and its double alkylation by 3 the 22-membered ring system of 5 was obtained from which 9,12,22,25-tetramethoxy[7.7]paracyclophane-4,17-dione (1) was prepared. The molecular structure of 1 is discussed on the basis of an X-ray analysis.
    Notes: Ausgehend von 1,4-Bis(3-iodpropyl)-2,5-dimethoxybenzol (3) wurde über die Reaktion zu der entsprechenden Bis(1,3-dithian-2-yl)-Verbindung 4 und deren erneute doppelte alkylierung durch 3 das 22-gliedrige Ringsystem von 5 aufgebaut, aus dem 9,12,22,25-Tetramethoxy[7.7]paracyclophan-4,17-dion (1) erhalten wurde. Die Molekülstruktur von 1 wird auf der Grundlage einer Röntgen-Strukturanalyse diskutiert.
    Additional Material: 2 Ill.
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  • 47
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 97-104 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The reactions of (η5-C5Me5)Cu(PR3) (1a - c) and (η1-C5Me5)-Au(PR3) (2a,c) with CS2 lead to insertion of carbon disulfide into the C5Me5 - M bond to the formation of the dithiocarboxyalto complexes (C5Me5CS2)M(PR3)n (3a - c, 4a, c). The silver compound (C5Me5CS2)Ag(PPh3)2 (5) is directly obtained from [AgCl(PPh3)]4, C5Me5Li, and excess CS2. The synthesis of 3 - 5 and (C5Me5CS2)Cu(PMe3)3 (6) can also be achieved almost quantitatively from C5Me5CS2Li, formed in situ from C5Me5Li and CS2 and MCl(PR3)n. By use of methyl iodide instead of MCl-(PR3)n, the ester C5Me5CS2Me (7). is obtained. The results of the X-ray structural analyses of (C5Me5CS2)Cu(PPh3)2 (3a) and (C5Me5CS2)Au(PiPr3) (4c) confirm that the dithiocarboxylato ligand to coordinated via both sulfur atoms to copper but only via one sulfur atom to gold. In solution, compound 6 undergoes a fast PMe3 ligand exchange which has been studied by NMR spectroscopy. The sign of J(PH) of 6 has been determined.
    Notes: Die Reaktionen von (η5-C5Me5)Cu(PR3) (1a - c) und (η1-C5Me5)-Au(PR3) (2a,c) mit CS2 führen zu einer Insertion des Schwefelkohlenstoffs in die C5Me5-Metall-Bindung und zur Bildung der Dithiocarboxylat-Komplexe (C5Me5CS2)M(PR3)n (3a - c, 4a, c). Die Silberverbindung (C5Me5CS2)Ag(PPh3)2 (5) ist direkt aus [AgCl(PPh3)]4, C5Me5Li und überschüssigem CS2 erhältlich. Die Synthese von 3 - 5 und (C5Me5CS2)Cu(PMe3)3 (6) gelingt praktisch quantitativ auch durch Umsetzung von in situ aus C5Me5Li und CS2 gebildetem C5Me5CS2Li und MCl(PR3)n. Bei Verwendung von Methyliodid an Stelle von MCl(PR3)n) entsteht der Ester C5Me5CS2Me (7). Die Ergebnisse der Röntgenstrukturanalysen von (C5Me5CS2)Cu(PPh3)2 (3a) und (C5Me5CS2)Au(PiPr3) (4c) bestätigen, daß der Dithiocarboxylat-Ligand über beide Schwefelatome am Kupfer, jedoch nur über ein Schwefelatome am Gold koordiniert ist. Verbindung 6 unterliegt in Lösung einem raschen PMe3-Ligandenaustausch, der NMR-spektroskopisch untersucht worden ist. Das Vorzeichen der PH-Kopplung von 6 wurde bestimmt.
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  • 48
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The pyrimidinium-4-olates of type 1 combine with enol ethers, enamines, ketene acetals, 1,4-dihydro-1,4-epoxynaphtalene, dimethyl fumarate, or dimethyl maleate to produce 2,6-diazabicyclo[2.2.2]octane-3,5-diones 2,3,5,7,9,17 - 19, whereas the reaction of the pyrimide[2.1-b]benzothiazolium-4-olate 13 with 8b or 1,1-bis(dimethylamino)ethene proceeds with formation of the 2(1H)-pyridinone derivative 15. The primary adducts 9a,b fragment thermally into 2(1H)-pyridinones 11a, b. In the example of the reaction of 1a with dimethyl maleate, the stereospecificity is determined.
    Notes: Die Pyrimidinium-4-olate von Typ 1 vereinigen sich mit Enolethern, Enaminen, Keten-acetalen, 1,4-Dihydro-1,4-epoxynaphthalin, Fumarsäure-dimethylester oder Maleinsäure-dimethyl-ester zu 2,6-Diazabicyclo[2.2.2]octan-3,5-dionen 2, 3, 5, 7, 9, 17-19, während das Pyrimido[2,1-b]benzothiazolium-4-olat 13 mit 8b oder 1,1-Bis(dimethylamino)ethen das 2(1H)-Pyridinon-Derivat 15 liefert. Die Primäraddukte 9a, b spalten thermisch in die 2(1H)-Pyridinone 11a, b. Am Beispiel der Umsetzung von 1a mit Maleinsäure-dimethylester wird die Stereospezifität ermittelt.
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  • 49
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 121-122 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The titanation of the sodium salt of ethyl (diethoxyphosphoryl)-acetate (1) results in a reagent which undergoes a stereoselctive Knoevenagel condensation with aldehydes to form the corresponding trisubstituted olefins 3 having the Z-configuration.
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  • 50
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 123-123 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aromatic aldehydes react specifically with (CH3)2TiCl2 to form the geminal dimethylated products.
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  • 51
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 125-129 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The styryl-substituted diphosphanes 2a, b are prepared by the reaction of the chlorophosphanes 1a, b with magnesium or tert-butyllithium, respectively. Compound 2b, substituted with bulky residues, gives the racemic form of the phosphaalkene 5 by Cope rearrangement, which is slowly and irreversibly converted into the meso-form.
    Notes: Aus den Chlorphosphanen 1a, b wurden die Styryl-substituierten Diphosphane 2a, b hergestellt. An der mit sperrigen Resten substituierten Verbindung 2b konnte erstmals die Cope-Umlagerung eines Diphosphans zu einem Phosphaalken 5-rac beobachtet werden. Die Racemform wandelt sich irreversibel in die Mesoform von 5 um.
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  • 52
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Binuclear carbonyl(1-propene-2,3-diyl)iron complexes 4, regioselectively derived from 1,2-propadienes 1, can be stepwise isomerized at 60°C to give binuclear 1-ferra-1,3-diene complexes 6, which at 130°C further rearrange to give ferracyclopentadienes 7 under formation of a C=C bond by a regiospecific insertion of CO at the higher substituted terminal carbon (but not at the Fe=C bond) of the ferradiene unit.
    Notes: Die von 1,2-Propadienen 1 regioselektiv erhältlichen zweikernigen Carbonyl(1-propen-2,3-diyl)eisen-Komplexe 4 isomerisieren stufenweise bei 60°C unter metallinduzierter 1,2-Wasserstoff-Wanderung zu zweikernigen 1-Ferra-1,3-dienen 6, und diese wiederum bei 130°C zu Ferracyclopentadienen 7 unter Aufbau einer C=C-Bindung durch regiospezifische Insertion von CO am höher substituierten terminalen C-Atom (nicht an der Fe=C-Bindung) der Ferradien-Einheit.
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  • 53
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 119-120 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (Trimethylsioxy)maleic anhydride (2) can easily be prepared from pyridinium salt 1 and chlorotrimethylsilane. Reaction of 2 with acetone or acetaldehyde affords the diols 3a and 3b.
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  • 54
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 55
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 135-139 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The 1,3-dithienium- and 1,3-dithiolenium tetrafluoroborates 3 (n=3, 2), respectively, react in good yields with the N,N-dialkylarylamines 4 to give the 2,2-disubstituted cyclic dithio acetals 5, which can be converted after dethioacetalization with HgCl2/HgO into the ketones 7.
    Notes: Die 1,3-Dithienium- bzw. 1,3-Dithiolenium-tetrafluoroborate 3 (n=3, 2) reagieren in guten Ausbeuten mit den N,N-Dialkylarylaminen 4 zu den 2,2-disubstituierten cyclischen Dithioacetalen 5, die sich nach Dethioacetalisierung mit HgCl2/HgO in die Ketone 7 überführen lassen.
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  • 56
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 131-134 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chlorophosphane 1 reacts with substituted allyl-Grignard reagents 2a, b to yield the 1,3-diphospha-1,5-hexadienes 3a, 4b. 31P-NMR temperature run of 3a shows dynamic processes, which can be explained by inversion of the trivalent P-atom. Above 40°C 3a undergoes a [3,3′]-phospha-carbon Cope rearrangement to give the thermodynamically stable product 4a. The structures of 3a and 4a are confirmed by X-ray structure analysis.
    Notes: Das Chlorphosphan 1 reagiert mit den substituierten Allyl-Grignard-Reagenzien 2a, b zu 1,3-Diphospha-1,5-hexadienen 3a, 4b. Bei 3a lassen sich 31P-NMR-spektroskopisch temperaturabhängige dynamische Phänomene beobachten, die auf Inversion am Phosphan-Phosphor zurückgeführt werden. Oberhalb von 40°C unterliegt 3a einer [3,3′]-Phospha-Kohlenstoff-Cope-Umlagerung zum thermodynamisch stabileren Produkt 4a. Die Molekülstrukturen von 3a und 4a wurden röntgenographisch bestimmt.
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  • 57
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 141-151 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: By reaction of alkyne-bridged dicobalt complexes with Fe2(CO)9 or Fe3(CO)12 alkyne- and vinylidene-bridged clusters of the general type FeCo2(CO)9(μ3-L) were accessible. These and the homologous RuCo2 clusters could be subjected to the reaction types metal exchange and alkyne-vinylidene rearrangement. Combination of both reaction types in the appropriate sequence yielded altogether 16 new hetero trinuclear clusters with μ3-vinylidene ligands. Internal alkynes R2C2 with R=Me, Et, Ph and terminal alkynes HC2R with R=H, Me, t-Bu, Ph were used; the latter were also the precursors of the corresponding vinylidene ligands. The resulting metal frameworks were of the FeCoNi, FeCoMo, FeCoW, RuCoNi, RuCoMo, RuCoW, FeNi2, and FeCo2 types. The alkyne-vinylidene rearrangements on the chiral clusters showed diastereoselectivities between 0 and 100%. The crystallographically determined molecular structure of RuCoWCp(CO)8(μ3-CCH-t-Bu) allows to interprete the diastereoselectivity as not resulting from steric effects.
    Notes: Durch Umsetzung von alkinverbrückten Dicobalt-Komplexen mit Fe2(CO)9 bzw. Fe3(CO)12 wurden alkin- und vinylidenverbrückte Cluster des allgemeinen Typs FeCo2(CO)9(μ3-L) zugänglich. Auf diese und die homologen RuCo2-Cluster ließen sich die Reaktionstypen Metallaustausch und Alkin-Vinyliden-Umlagerung anwenden. Kombination beider Reaktionstypen in der geeigneten Reihenfolge lieferte insgesamt 16 neue Hetero-Dreikerncluster mit μ3-Alkin-Liganden und 29 entsprechende Verbindungen mit μ3-Vinyliden-Liganden. Es kamen interne Alkine R2C2 mit R=Me, Et, Ph und terminale Alkine HC2R mit R=H, Me, t-Bu, Ph zum Einsatz; letztere waren auch die Vorläufer der entsprechenden Vinyliden-Liganden C2HR. Die entstehenden Metallgerüste waren vom FeCoNi-, FeCoMo-, FeCoW-, RuCoNi-, RuCoMo-, RuCoW-, FeNi2- und FeCo2-Typ. Die Alkin-Vinyliden-Umlagerungen auf den chiralen Clustern zeigten Diastereoselektivitäten zwischen 0 und 100%. Die kristallographisch bestimmte Molekülstruktur von RuCoWCp(CO)8(μ3-CCH-t-Bu) läßt sich so interpretieren, daß die Diastereoselektivität nicht auf sterischen Effekten beruht.
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  • 58
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 153-158 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: In contrast to a literature report, diazomethane and diazoaceticester add to the CC double bond of tetracyanoethylene and ethylenetetracarboxylic ester. The behavior of the 1- and 2-pyrazolines deviates from the rule.
    Notes: Entgegen einem Literaturbericht finden die Cycloadditionen des Diazomethans und Diazoessigsäureesters an die CC-Doppelbindung des Tetracyanethylens und des Ethylentetracarbonsäureesters statt. Das Verhalten der 1- and 2-Pyrazoline zeigt Abweichungen von der Norm.
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  • 59
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 159-169 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The reaction with excess of diazomethane furnished methyl 4-cyano-1-methylpyrazole-5- and-3-carboxylate (2 and 3) as well as the three N-methyl-1,2,3-triazolecarboxylic esters 4-6. A mechanistic study revealed a poly-step sequence. The initial formation of the pyrazoline 8 proceeded normal. Base catalysis effected an equilibration of trans- and cis-2-pyrazoline, 8⇌12, followed by a fragmentation into methyl 4-cyano-3-pyrazolecarboxylate (26) and methyl cyanoformate (32); a 4H-pyrazole is supposed to be the key intermediate. The final products mentioned above emerged from further reaction of 26 and 32 with diazomethane.
    Notes: Die Reaktion mit überschüssigem Diazomethan lieferte 4-Cyan-1-methylpyrazol-5- und-3-carbonsäure-methylester (2 und 3) sowie die drei N-Methyl-1,2,3-triazolcarbonsäure-methylester 4-6. Eine mechanistische Studie brachte eine vielstufige Reaktionsfolge an den Tag. Die einleitende Bildung des Pyrazolins 8 vollzog sich normal. Unter Baseneinwirkung kam es zur Äquilibrierung von trans-2-Pyrazolin 8 mit cis-2-Pyrazolin 12, gefolgt von einer Spaltung in 4-Cyan-3-pyrazolcarbonsäureester (26) und Cyanameisensäureester (32); ein 4H-Pyrazol wird als Zwischenstufe vermutet. Die oben erwähnten Endprodukte entsprangen der Weiterreaktion von 26 und 32 mit Diazomethan.
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  • 60
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    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phosphorus compounds with Unusual Cooradination, 171). - On the Trapping Reaction Of Phenylthioxophosphane with Hexacarbonylbnis(cyclopentadienyl)dimolybdenumPhenylthioxophosphane (6) - generated in boiling toluene from endo/exo-10 - reacts under these conditions with hexacarbonylbis(cyclopentadienyl)dimolybdenum (12) to yield the two binuclear molybdenum complexes 13a and 14a. A crystal structural analysis has been performed for 13a. Lawesson's reagent (17) leads under the same conditions with 12 to the analogous complexes 13b and 14b.
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  • 61
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 62
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1271-1279 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses, Structures, and Properties of 1,1-Dialkoxy-2-azapropenylium Salts1,1-Dialkoxy-2-azapropenylium salts 1 were synthesized by alkylation at the oxygen atom of N-methylenecarbamates 4 with trialkyloxonium salts 5, in cases, where steric hindrance makes N-alkylation difficult (4a); otherwise the iminium salts 6 are formed preferentially. A more general synthetic route to the salts 1 is based on the reaction of N-(alkoxymethyl)imidocarbonates 8 with acylium ions (acyl cleavage reaction). The salts are thermally not very stable; phenyl ester derivatives are easily converted into 4H-1,3-benzoxazine derivatives 11. - An X-ray analysis of 1aa shows an allenic structure with orthogonal π systems; for steric reasons the C-N-C bond angle is reduced to ca. 150°. - Quantum mechanical ab initio calculations predict high steric flexibility for the salts 1; in the parent compound (16a) an allenic structure is slightly (2-3 kcal/mol) favored over allylic forms (16d). Thermodynamically more stable are the isomeric iminium salts 6 and 17, respectively. - Depending on the substitution pattern in solution (IR, dynamic NMR spectroscopy) allenic (1a) or allylic (1b) structures are observed.
    Notes: 1,1-Dialkoxy-2-azapropenylium Salze 1 können durch O-Alkylierung am Carbonylkohlenstoff von N-Methylencarbamidsäureestern 4 mit Trialkyloxonium-Salzen 5 erhalten werden, falls eine N-Alkylierung sterisch erschwert ist (4a); andernfalls werden die Iminium-Salze 6 gebildet. Eine allgemeinere Darstellungsmethode für die Salze 1 beruht auf der Umsetzung von N-(Alkoxymethyl)-imidokohlensäureestern 8 mit Acylium-Ionen (Acylspaltung). Die Salze 1 sind thermische nicht sehr beständig Phenylester-Derivate gehen leicht in 4H-1,3-Benzoxazin-Derivate 11 über. - Die Kristallstrukturanalyse von 1aa ergibt eine allenische Struktur mit orthogonalen π-Systemen, wobei der C-N-C-Bindungswinkel auf ca. 150° reduziert ist (sterische Effekte). - Quantenmechanische Ab-initio-Berechnungen sagen hohe sterische Flexibilität der Salze 1 voraus, wobei beim Grundkörper allenische Strukturen (16a) geringfügig (ca. 2-3 kcal/mol) gegenüber allylischen Formen (16d) bevorzugt sind. Thermodynamisch günstiger als die Salze 1 (bzw. 16) sind die isomeren Iminium-Salze 6 bzw. 17. - Je nach Substitutionsmuster beobachtet man in Lösung (IR-, dynamische NMR-Spektroskopie) allenische (1a) oder allylische Strukturen (1b).
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  • 63
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organic Syntheses via Transition Metal Complexes, 231). - Bicyclic 3-Imidazolines from Primary Isocyanides and Alkenylcarbene Complexes by a Metal-Induced Anomalous Insertion of a C=N- into an α-CH Bond of the IsocyanideAlkenylcarbene complexes 1 react smoothly with one equivalent of methyl- and primary isocyanides 2 to give 1:1 adducts 3, which contain C-alkenyl ketenimine ligands. To these a second molecule of 2 may be added in a [4 + 1] fashion with formation of bis-(imino)cyclopentene complexes 6 or - in a competing reaction path - with induction of a second spontaneous ring closure to 3-imidazoline complexes 4/5 by an insertion of 2 into the α-CH bond of 3. Complexes 4-6 were characterized spectroscopically, the 3-imidazoline complex 4a also by an X-ray analysis. In competition with the addition of 2c to 3c an isomerisation of 3c to the α-alkoxycyanide complex 9a is observed involving an N/Cmigration of the N-allyl group. Steric factors exhibit strong influences on the course of the different competition reactions.
    Notes: Alkenylcarben-Komplexe 1 bilden mit Methyl- bzw. einem primären Isocyanid 2 1:1-Addukte 3, die einen C-Alkenylketenimin-Ligand enthalten. An diesen läßt sich ein zweites Molekül 2 addieren unter [4 + 1]-Cycloaddition zu Bis(imino)cyclopenten- 6 bzw. unter weiterem Ringschluß zu 3-Imidazolin-Komplexen 4/5 durch metallinduzierte Insertion von 2 in eine α-CH2N-Bindung von 3. Die Komplexe 4-6 wurden spektroskopisch, der 3-Imidazolin-Komplex 4a zusätzlich durch eine Kristallstrukturanalyse charakterisiert. Neben einer Addition von 2c an 3c wird eine Isomerisierung von 3c zum α-Alkoxycyanid-Komplex 9a unter N/C-Wanderung des N-Allylrests beobachtet. Sterische Faktoren beeinflussen entscheidend das Zusammenspiel sämtlicher Konkurrenzreaktionen.
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  • 64
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1281-1285 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Arsenic as a Functional Center and as a Substituent in YlidesBis(dimethylarsino)-, bis(diethylarsino)-, and bis(diphenylarsino)-methane (1-3) are obtained from Cl2AsCH2AsCl2 and the corresponding Grignard reagents. Through the reaction with MeI or EtI, respectively, 1 and 2 give mono- and bis-quarternary salts 4-7. The former (4, 6) when treated with NaNH2 in liquid ammonia, yield the ylides R3As=CH-AsR2 (R=Me: 8; R=Et: 9), while the latter (5, 7) could not be converted into double-ylides R3As=C=AsR3. 3 affords the ylide MePh2As=CH-AsPh2 (11) via the arsonium salt 10. Treatment of 11 with Ph2AsCl gives MePh2As=C(AsPh2)2 (13) as the product of a transylidation reaction. With MeI only C-alkylation of 11 takes place (to give 14). - Ph2PCH2AsPh2 is the starting material for the synthesis of the (arsinomethyl)phosphonium salt 17 and the ylide MePh2-P=CH-AsPh2 (15). This ylide is also exclusively C-alkylated by MeI (to give 16). Methylation of Ph2PCH2AsPh2 by MeOSO2F yields the diquaternary salt 18, which on reaction with NaNH2/NH3 (liq.) affords the first mixed P/As double-ylide MePh2-P=C=AsPh2Me (19). The ylide Ph3P=C(AsPh2)2)2 (20) is converted into semi-ylidic quaternary salts [Ph3PC(AsPh2)-AsPh2Me]I (21) and [Ph3PC(AsPh2Me)2]I2 (22) by MeI, which are analogues of the tris(phosphonio)methanide salts [(R3P)3C]X2.
    Notes: Bis(dimethylarsino)-, Bis(diethylarsino)- und Bis(diphenylarsino)-methan (1-3) wurden aus Cl2AsCH2AsCl2 und den entsprechenden Grignard-Reagenzien dargestellt. 1 und 2 ergeben mit MeI bzw. EtI die Mono- und Bisquartärsalze 4-7. Aus ersteren (4, 6) entstehen bei Einwirkung von NaNH2 die Arsen-Ylide R3As=CH-AsR2 (R=Me: 8, R=Et: 9). Die Isolierung von Doppel-yliden R3As=C=AsR3 aus 5 und 7 gelang dagegen nicht. Aus 3 ist über das Monoquartärsalz 10 analog das Ylid MePh2-As=CH -AsPh2 (11) zugänglich, aus dem mit Ph2AsCl unter Umylidierung das erste Arsonium-bis(arsino)methylid, MePh2-As=C(AsPh2)2 (13), hervorgeht. 11 wird von MeI am ylidischen C-Atom methyliert (zu 14). - Von Ph2PCH2AsPh2 aus gelangt man mit MeI zum (Arsinomethyl)phosphoniumsalz 17, das mit NaNH2 das Ylid MePh2P=CH - AsPh2 (15) liefert. Auch dieses Ylid wird von MeI nur C-alkyliert (zu 16). Die Quartärisierung von Ph2PCH2AsPh2 mit MeOSO2F führt zum Diquartärsalz 18, aus dem das erste gemischte P/As-Doppel-ylid, MePh2-P=C=AsPh2Me (19), entsteht. Das Ylid Ph3P=C(AsPh2)2 (20) kann mit MeI in die Semi-ylid-Quartärsalze [Ph3PC(AsPh2)-AsPh2Me]I (21) und [Ph3PC(AsPh2Me)2]I2 (22) übergeführt werden, die den Tris(phosphonio)methanid-Salzen [(R3P)3C]X2 entsprechen.
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  • 65
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    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organic Syntheses via Transition Metal Complexes, 251). - Cyanoallylation of Carbene Ligands with Ally Isocyanides via Metal-Induced N/C-Allylic Rearrangement of intermediate 3-Aza-1,2,5-hexatriene ComplexesAllyl isocyanides 2 react with (CO)5M=C(OEt)C6H5 (1, M=Cr, W) to give N-allylketenimine/(3-aza-1,2,5-hexatriene) complexes 3 in high yields. In absence of suitable reactants compounds 3 isomerise spontaneously and smoothly already at 0°C via a metalinduced N/C-migration of the allyl group to give 4-pentenenitrile complexes 5, from which the ligand can be disengaged by substitution with pyridine. The regiochemistry of the rearrangement corresponds to the [3,3] type as has been proven by a labeling experiment with α,α-dideuterioallyl isocyanide. In the presence of an alcohol, the reaction of 1 with 2 leads to the formation of competition products resulting from an N/C-rearrangement or the addition of the alcohol to 3, respectively. The competition ratio strongly depends on the type of metal used. The tungsten complex 3b, e.g., at 0°C adds one equivalent of an alcohol to give up to 97% yields of (allylamino)carbene complexes 8b-c, while the corresponding chromium complex 3a rearranges smoothly under these conditions to give 5a only. The addition of alcohols to 3b is reversible: on thermolysis of 8c at 70°C the products of thermal isomerisation of 3b together with a chelate complex 9 are obtained.
    Notes: Durch Addition von Allylisocyaniden 2 an (CO)5M=C(OEt)C6H5 (1, M=Cr, W) erhält man in hohen Ausbeuten N-Allylketenimin-/(3-Aza-1,2,5-hexatrien)-Komplexe 3. Diese isomerisieren in Abwesenheit geeigneter Reaktionspartner spontan und glatt schon bei 0°C unter metallinduzierter N/C-Wanderung des Allylrestes zu 4-Pentennitril-Komplexen 5. Anhand von Markierungsexperimenten mit α,α-Dideuterioallylisocyanid wurde hierfür die Regiochemie einer [3,3]-Umlagerung nachgewiesen. Aus 5 kann der Ligand durch Verdrängung mit Pyridin freigesetzt werden. Bei der Umsetzung von 1 mit 2 in Gegenwart von Alkoholen beobachtet man in Konkurrenz zur N/C-Umlagerung eine Addition des Alkohols an 3. Abhängig vom Metall ergeben sich dabei erhebliche Reaktivitätsunterschiede: der Wolframkomplex 3b z. B. addiert bei 0°C rasch ein äquivalent des Alkohols unter (fast) ausschließlicher Bildung von (Allylamino)carben-Komplexen 8b, c, wohingegen der entsprechende Chromkomplex 3a unter gleichen Reaktionsbedingungen glatt zu 5a isomerisiert. Die Addition von Alkoholen an 3b ist reversibel: bei der Thermolyse (70°C) von 8c erhält man neben einem Chelatkomplex 9 das thermische Isomerisierungsprodukt von 3b.
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  • 66
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 325-329 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: With 3-(2-furyl)acrolein (17) as an example it is demonstrated that umpolung of aldehydes with trimethylsilyl cyanide allows the synthesis of diene-dienophiles (19, 21) for intramolecular Diels-Alder reactions introducing the required protecting group at the same time. In this novel model reaction thermal [4 + 2] cycloaddition finally affords so far unknown tricyclic ketones with one furan ring (25 and 26). This reaction sequence should be useful in natural product synthesis.
    Notes: Am Beispiel von 3-(2-Furyl)acrolein (17) wird gezeigt, daß die Umpolung von Aldehyden mit Trimethylsilylcyanid eine Synthese von Dien-Dienophilen (19, 21) für die intramolekulare Diels-Al-der-Reaktion erlaubt, bei der zugleich die erforderliche Carbonylschutzgruppe eingeführt wird. Thermische [4 + 2]-Cycloaddition erzeugt in dieser neuen Modellreaktion schließlich bisher unbekannte tricyclische Ketone mit einem Furanring (25 und 26). Die Reaktionsfolge dürfte für Naturstoffsynthesen einsetzbar sein.
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 331-333 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Die relative chemische Verschiebung des OH-Protonen-Signals in den 1H-NMR-Spektren eines Paares diastereomerer ß-Hydroxyether erlaubt eine syn/anti-Zuordnung der relativen Konfiguration. Dies basiert vermutlich auf der Bildung von Strukturen mit intramolekularer Wasserstoff-Brücke. Insofern ist diese Regel auf solche ß-Hydroxyether beschränkt, bei denen nur dieser Typ von intramolekularer H-Brücke ausgebildet werden kann.
    Notes: In a pair of diastereomeric ß-hydroxy ethers the relative 1H-NMR chemical shift of the OH proton is diagnostic for the syn or anti stereostructure. This is probably based on the presence of internally hydrogen-bonded structures. The rule is therefore restricted to those compounds for which only this type of internal hydrogen bonding is accessible.
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  • 68
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 307-318 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Die Photoreaktionen von Biacetyl (1) mit verschiedenen elektronenreichen Olefinen wurden untersucht. Im allgemeinen bilden sich bei der Bestrahlung mit λ=400-480 nm (nπ*-Anregung von Biacetyl) in Abhängigkeit von der Olefin-Struktur Oxetane und Allylalkohole. Hinweise auf die primäre Bildung eines Exciplexes liefert die ungewöhnliche Abhängigkeit der Geschwindigketiskonstanten der Lumineszenzlöschung von Biacetyl durch die Olefine (log kq) von der freien Bildungsenthalpie des Elektronentransfers (ΔG2). Ein Mechanismus mit einer Exciplex-Zwischenstufe und einem ionischen Photodissoziationsweg gestattet es nach Anpassung der Parameter, die experimentellen Daten gut zu simulieren (log kq/ΔG2-Korrelation). Vollständiger Elektronentransfer wurde als Folgeprozeß bei einigen besonders elektronenreichen Olefinen mit Hilfe der ESR-Spektroskopie bzw. durch Abfangen der Radikalkationen bewiesen. Die Abhängigkeit der Produktquantenausbeuten von der Lösungsmittelpolarität bestätigt die Konkurrenz zwischen Produktbildung und ionischer Photodissoziation. Die bevorzugte Bildung von Allylalkoholen (Reduktionsprodukte) mit starken Donor-Olefinen und die regioselektiv ablaufende Oxetanbildung mit Ketenacetal werden auf der Basis von stark polaren Exciplexen bzw. Kontaktionenpaaren und Zwitterionen als Zwischenstufen diskutiert.
    Notes: The photoreactions of biacetyl (1) with various electron-rich olefins have been investigated. Oxetanes and allyl alcohols are formed upon irradiation with λ=400-480 nm (nπ* excitation of biacetyl) depending on the nature of the olefin. An unusual relationship between the rate constants of luminescence quenching of biacetyl by olefins (log kq) and the free enthalpies of electron transfer (ΔG2) indicate formation of an exciplex first. A reasonable good fit between experimental results of log kq and ΔG2 has been obtained on the basis of a mechanistic model which includes the exciplex intermediate as well as an ionic photodissociation pathway and some empirical adjustment of the parameters. Complete electron transfer as a consecutive process has been proven for some strong electron-donating olefins by means of ESR spectroscopy and scavenging of the radical cations. The solvent dependence of the product quantum yields further confirms the competition between ionic photodissociation and product formation. The preferred formation of allyl alcohols (reduction products) with strong electron-donating olefins and the highly regioselective oxetane formation with ketene acetal are discussed in terms of exciplexes of strong CT character or even contact ion pairs and dipolar intermediates.
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 351-354 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The mesylhydroxylamines (CH3SO2)2NOH, (CH3SO2)2NOCH3, CH3SO2N(H)OSO2CH3, CH3SO2N(CH3)OSO2CH3 (1-4) and (CH3SO2)2NOSO2CH3 (5) were treated with basic, neutral, and acidic aqueous solutions. The reaction products were identified. Possible decomposition mechanisms were discussed.
    Notes: Die Mesylhydroxylamine (CH3SO2)2NOH, (CH3SO2)2NOCH3, CH3SO2N(H)OSO2CH3, CH3SO2N(CH3)OSO2CH3 (1-4) und (CH3SO2)2NOSO2CH3 (5) wurden in alkalischer, neutraler und saurer Lösung hydrolysiert. Die Zersetzungsprodukte wurden identifiziert und mögliche Reaktionswege ihrer Entstehung diskutiert.
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 339-344 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Die Dipole 3, 13 aus Tosylisocyanat (2a) und Imido(thio)kohlensäureestern 1 (12) geben O → N-Alkyl-Verschiebungen zu (Thio)Allophansäureestern 5 (14). ähnlich führt die Addition von Tosylisothiocyanat (2b) an den Isoharnstoff 24a zum Produkt 28 einer O→S-Methyl-Verschiebung. Ausgehend von 2a und den Imidothiokohlensäureestern 12b,c ergab ein Kreuzungsversuch die vier Produkte 14a-d und bewies so den intermolekularen Verlauf der Umlagerung. Beim Zusammengeben des Isothiocyanats 2b und der Imido(thio)kohlensäureester 1 (12) oder von 2a und der Isoharnstoffe 24a,b bleibt die Reaktion jedoch auf der Stufe der Dipole 8, 19, 25a, b stehen.
    Notes: O→N alkyl shifts are observed in the dipoles 3, 13 from tosyl isocyanate (2a) and imido(thio)carbonates 1 (12) to give (thio)allophanates 5 (14). Similarly, addition of tosyl isothiocyanate (2b) to isourea 24a leads to the product 28 of an O → S methyl shift. A cross-over experiment involving 2a and imidothiocarbonates 12b,c gives the four products 14a-d proving the intermolecular nature of the rearrangement. However, on mixing 2a and isoureas 24a,b or 2b and imido(thio)carbonates 1 (12), the reaction stops at the stage of dipoles 8, 19, 25a,b.
    Additional Material: 2 Tab.
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  • 71
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1323-1330 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: PMO-Analyse von Cycloadditionen, I. - Diels-Adler-Reaktionen von 2,3-Bis(methylen)norbornanEine störungstheoretische Methode (PMO) zur Berechnung der Wechselwirkung von Molekülen auf der Basis des semiempirischen MINDO/3-Verfahrens wird auf die Cycloadditionen von 2,3-Bis(methylen)norbornan (1) mit den elektronenarmen Olefinen 2-5 angewendet. Verschiedene Anteile der Wechselwirkungsenergie, von sterischen Effekten, polaren Beiträgen und Orbitalwechselwirkungen stammend, werden analysiert. Die Ergebnisse werden mit dem Programmpaket PERVAL, das für einen IBM AT Personal Computer entwickelt wurde, berechnet und graphisch ausgewertet. Die Reaktivitätssequenz 2 〈 3 〈 4 〈 5 wird auf die dominante HOMODien-LUMODienophil-Wechselwirkung zurückgeführt. Es werden verschiedene Möglichkeiten der Anwendung des Programms PERVAL aufgezeigt.
    Notes: A perturbational molecular orbital (PMO) treatment within the semiempirical MINDO/3 approximation is applied to the cycloadditions of 2,3-bis(methylene)norbornane (1) to electron-deficient olefins (2-5). Different contributions to the interaction energy deriving from steric effects, polar effects, and orbital interactions are analysed. The results, obtained by the program package PERVAL, which is developed for an IBM AT personal computer, are evaluated graphically. The origin of the reactivity sequence 2 〈 3 〈 4 〈 5 is traced back to the HOMOdiene-LUMOdienophile interaction. Various possibilities to interpret the results of PMO calculations are demonstrated.
    Additional Material: 4 Tab.
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  • 72
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1339-1346 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diels-Alder Reactions with 2H-Pyran-2-ones: Reactivity and Selectivity2H-Pyran-2-ones 1 react with maleic anhydride (2) in a double Diels-Alder reaction to give bicyclo[2.2.2]oct-2-ene-5,6:7,8-tetracarboxylic dianhydrides 5; the syn/syn structure was established. As expected, the reactivity of 1 was increased by electron donor substituents (OR, alkyl) and diminished by electron withdrawing substituents (CO2R). The steric influence of substituents at C-6 also decrease the reactivity of 1. - Methyl propiolate (6) and phenylacetylene (9) react with 1 to form the Diels-Alder products 7 which suffer CO2 elimination to yield methyl benzoates 8 with low and biphenyls 10 with high regioselectivity, respectively.
    Notes: 2H-Pyran-2-one 1 gehen mit Maleinsäureanhydrid (2) eine zweifache Diels-Alder-Reaktion zu Bicyclo[2.2.2]oct-2-en-5,6:7,8-tetracarbonsäure-dianhydriden 5 ein, deren syn/syn-Struktur nachgewiesen wurde. Die Reaktivität von 1 wird erwartungsgemäß durch Donor-Substituenten (OR, Alkyl) erhöht und durch Acceptor-Substituenten (CO2R) verringert; Substituenten in 6-Stellung der α-Pyrone 1 führen infolge ihres sterischen Einflusses zu einer deutlichen Reaktivitätsverminderung. - Aus 1 und Propiolsäuremethylester (6) bzw. Phenylaceylen (9) entstehen über die primären Diels-Alder-Cycloadditionsprodukte 7 unter CO2-Abspaltung isomere Benzoesäure-methylester 8 mit geringer bzw. Biphenyle 10 mit hoher Regioselektivität.
    Additional Material: 11 Tab.
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  • 73
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1347-1355 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses of Highly Substitued Benzenes via Diels-Alder Reactions with 2H-Pyran-2-onesThe 2H-pyran-2-ones (α-pyrones) 1 react as dienes in Diels-Alder reactions with acetylene derivatives. The primarely formed cycloadducts immediately aromatize to benzenes by CO2 elimination. Thus, methyl acetylenedicarboxylate (2a) gives dimethylphthalates 3, and methyl acetylenediphosphonate (2b) gives dimethyl 1,2-phenylenediphosphonates 8. The reactions of 1-(dimethylamino)-1-methoxyethene (9) with 1 regioselectively produce N,N-dimethylanilines 10 and isomeric homophthalate derivatives 12. Naphthoquinones 14 could be generated from 1,4-benzoquinone (13) and 1 in the presence of acetic anhydride and Pd/C. Hydroxy-2H-pyran-2-ones 4 react via their trimethylsilyl ether 6 analogously with 2a to give dimethyl (trimethylsiloxy)-phthalates 7 which are easily converted to phenols 5 by acidcatalyzed hydrolysis.
    Notes: Acetylenderivate reagieren mit 2H-Pyran-2-onen (α-Pyronen) 1 als Dien-Komponenten primär zu Diels-Alder-Cycloadditionsprodukten, die sofort unter CO2-Abspaltung zu Benzolderivaten aromatisieren. So werden mit Acetylendicarbonsäure-dimethylester (2a) Phthalsäure-dimethylester 3 und mit Acetylenbis(phosphonsäure-dimethylester) (2b) 1,2-Phenylenbis(phosphonsäure-dimethylester) 8 erhalten. 1-(Dimethylamino)-1-methoxyethen (9) sowie 2,3-Pentadiendisäure-dimethylester (11) bilden mit 1 regioselektiv N,N-Dimethylaniline 10 sowie isomere Homophthalsäure-Derivate 12. Aus 1,4-Benzochinon (13) und 1 entstehen in Gegenwart von Acetanhydrid und Pd/C Naphthochinone 14. Hydroxy-2H-pyran-2-one 4 lassen sich über ihre Trimethylsilylether 6 mit 2a zu den (Trimethylsiloxy)phthalsäure-dimethylestern 7 umsetzen, deren säurekatalysierte Hydrolyse glatt zu den Phenolen 5 führt.
    Additional Material: 13 Tab.
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  • 74
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1331-1338 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Flash Vacuum Pyrolysis Of o-Alkyaryl- and Arylalkylchloroboranes. - Synthesis of Benzoannutated Boracycloalkenes The dichloroorganylboranes chosen as pyrolytic starting materials were synthesized upon treatment of the corresponding triorganylboroxines and aryltrimethylsilanes (giving 3, 4) or the tetraorganylstannanes (giving 9-12, 17-20) with boron trichloride. At 700°C the flash vacuum pyrolysis of the dichloro(2-ethylphenyl)boranes 10 and 4 led to 1-boraindanes 21 and 22 selectively. The dichloro-2-tolylborane (9), the B-dimethylamino derivative, and mesitylboranes like 3 were completely stable upon pyrolysis. Pyrolyzing the isopropylphenylborane 12 1,5-elimination exclusively took place yielding 26, while pyrolysis of propylphenylborane 11 led to a mixture of boraindane 29 and boratetraline 30. To exclude such competitive reactions, some arylalkyldichloroboranes were pyrolyzed. At 750°C dichloro(2-methylbenzyl)borane (18) exclusively yielded oligomeric 2-chloro-2-boraindane (31). At 950°C even the pyrolysis of benzyldichloroborane (17) succeeded in a 1,4-elimination reaction yielding the eight-membered 2H-benzoborete dimer 34. The inversion barrier of 34 is ΔG228=10.3 kcal mol-1, determined by NMR spectroscopy. The pyrolysis of the next-higher homologous dichloroorganylborane 19 yielded a boraindane 21 and a noncyclic diorganylborane 38 by a dehydroboration/hydroboration pathway. Both reaction types also took place when pyrolyzing dichloro[2-(2-tolyl)ethyl]borane (20): cyclization under formation of a five-membered ring system 39, formed upon attack of an aromatic C-H bond exclusively, and formation of an open-chain chlorodiorganylborane 40.
    Notes: Die als Pyrolyse-Edukte eingesetzten Dichlororganylborane wurden durch Umsetzung der entsprechenden Triorganylboroxine und Aryltrimethylsilane (zu 3, 4) oder der Tetraorganylstannane (zu 9-12, 17-20) mit Bortrichlorid gewonnen. Die Blitzvakuumpyrolyse der Dichlor(2-ethylphenyl)borane 10 und 4 führte bei 700°C selektiv zu den 1-Boraindanen 21 und 22. Das Dichlor-2-tolylboran (9) war thermisch ebenso stabil wie das B-Dimethylamino-Derivat und Mesitylborane wie 3. Auch bei der Pyrolyse des Isopropylphenylborans 12 trat ausschließlich 1,5-Eliminierung unter Bildung von 26 ein, während die Pyrolyse des Propylphenylborans 11 zu einem Gemisch aus Boraindan 29 und Boratetralin 30 führte. Um derartige intramolekulare Konkurrenzsituationen auszuschließen, wurden Arylalkyldichlorborane pyrolysiert. Dichlor(2-methylbenzyl)boran (18) lieferte bei 750°C ausschließlich oligomeres 2-Chlor-2-boraindan (31). Bei 950°C reagierte sogar Benzyldichlorboran (17) unter 1,4-Eliminierung zu dem achtgliedrigen 2H-Benzoboret-Dimeren 34. Die Inversionsbarriere von 34 wurde NMR-spektroskopisch zu ΔG228=10.3 kcal mol-1 bestimmt. Die Pyrolyse des nächsthöheren homologen Dichlororganylborans 19 lieferte ein Boraindan (21) und ein nichtcyclisches Diorganylboran 38 über eine Dehydroborierungs-/Hydroborierungsreaktion. Beide Reaktionstypen wurden auch bei der Pyrolyse von Dichlor[2-(2-tolyl)ethyl]boran (20) beobachtet: Cyclisierung ausschließlich unter Fünfringbildung (39) durch Angriff einer aromatischen C-H-Bindung und Bildung eines offenkettigen Chlordiorganylborans (40).
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  • 75
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1357-1368 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Adduct Formation and Reactivity Of Silane- and Germaneimines Me2E=NR (E=Si, Ge)1)Silane- and Germaneimines Me2E= NR (E=Si, Ge; R=silyl), generated as reactive intermediates by thermal [2+3] cycloreversion from [2+3] cycloadducts of Me2E=C(SiMe3)2 or Me2E=NR with silyl azides RN3, combine with reactants a (e. g. NEtMe2) under addition (formation of adducts 7), with a - b [e. g. RO - H, RHN - H, X - SiMe3 (X=Cl, N3, MeO, Me2N), Cl - GeMe3, Cl - SnMe3] under insertion into the a - b bond (formation 13-16), with a=b (e.g. RN=EMe2, O=CPh2) under [2+2] cycloaddition (e. g. formation of 17, 18), with a=b=c (e.g. R′N=N=N) under [2+3] cycloaddition (formation of 19, 20), and with a=b - c - H (e.g. CH2=CR - CH2 - H, O=CMe - CH2 - H) under ene reaction (formation of 21-24). [2+4] cycloaddition of Me2Si=NR with organic 1,3-dienes (e. g. CH2=CR - CR=CH2, cyclopentadiene) is not observed. By comparison with ethenes Me2E=C(SiMe3)2, imines Me2E=NR have greater tendency for insertion and lesser tendency for cycloaddition; by comparison with silaneimines Me2Si=NR, germaneimines Me2Ge=NR are possibly less Lewis acidic.
    Notes: Silan- und Germanimine Me2E=NR (E=Si, Ge; R=Silyl), erzeugt als Zwischenstufen durch thermische [2+3]-Cycloreversion aus den [2+3]-Cycloaddukten von Me2E=C(SiMe3)2 bzw. Me2E=NR mit Silylaziden RN3, reagieren mit Reaktanden a (z. B. NEtMe2) unter Addition (Bildung von Addukten 7), mit a-b [z. B. RO - H, RHN - H, X - SiMe3 (X=Cl, N3, MeO, Me2N), Cl - GeMe3] unter Insertion in die a - b-Bindung (Bildung von 13-16), mit a=b (z. B. RN=EMe2, O=Cph2) unter [2+2]-Cycloaddition (z. B. Bildung von 17, 18), mit a=b=c (z. B. R′N=N=N) unter [2+3]-Cycloaddition (Bildung von 19, 20) und mit a=b - c - H (z. B. CH2=CR - CH2 - H, O=CMe - CH2 - H) unter En-Reaktion (Bildung von 21-24). [2+4]-Cycloaddition von Me2Si=NR mit organischen 1,3-Dienen (z. B. CH2=CR - CR=CH2, Cyclopentadien) wird nicht beobachtet. Verglichen mit den Ethenen Me2E=C(SiMe3)2 zeigen die Imine Me2E=NSiMe3 eine größere Tendenz zur Insertion und kleinere Tendenz zur Cycloaddition; verglichen mit den Silaniminen Me2Si=NR sind die Germanimine Me2Ge=NR wohl weniger Lewis-sauer
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  • 76
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1375-1395 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions with Diazoazoles, VIII1). - Syntheses of Azolo [5,1-d]-1,2,3,5,-tetrazin-4(3H-onesAzolo[5,1-d]-1,2,3,5-tetrazin-4(3H)-ones 4 and 5 are formed by cycloaddition reactions of α-diazoazoles 2 with aryl or alkyl isocyanates 3a-p, respectively, as well as with diisocyanates 3q, r (Method A). Alternative syntheses for 4 are presented by diazotization of N-alkyl(aryl)-5-amino-1H-pyrazole-1-carboxamides (6) and subsequent intramolecular coupling (Method B), by coupling of 3-diazo-5-methyl-4-phenyl-3H-pyrazole (2A) with primary amines 11 to give pyrazolyltriazenes 12A, and by their carbonylation reaction (Method C). The lability of azolotetrazinones against bases is exemplified with-methyl-3,8-diphenylpyrazolo-[5,1-d]-1,2,3,5-tetrazine-4(3H)-one (4Aa) in its reaction with hydroxide ions or morpholine.
    Notes: Azolo[5,1-d]-1,2,3,5-tetrazin-4(3H)-one 4 und 5 entstehen durch Cycloaddition von α-Diazoazolen 2 an Aryl- oder Alkylisocyanate 3a-p bzw. an Diisocyanate 3q, r (Methode A). Alternativsynthesen für 4 werden durch Diazotierung von N-Alkyl(Aryl)-5-amino-1H-pyrazol-1-carboxamiden 6 und nachfolgende intramolekulare Kupplung (Methode B) sowie durch Kupplung von 3-Diazo-5-methyl-4-phenyl-3H-pyrazol (2A) mit primären Aminen 11 zu Pyrazolyltriazenen 12A und deren Carbonylierung (Methode C) vorgestellt. Die Basenlabilität der Azolotetrazinone wird am Beispiel des 7-Methyl-3,8-diphenylpyrazolo[5,1-d]-1,2,3,5-tetrazin-4(3H)-ons (4Aa) in dessen Reaktion mit Hydroxidionen oder Morpholin aufgezeigt.
    Additional Material: 9 Tab.
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  • 77
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1369-1374 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: NMR Spectroscopic Investigations on the Constitution of Benzyl and 1- Naphthylmethyl Compounds of Titanium, Zirconium, and Hafnium1H- und 13H- spectra of tetrabenzyl compounds (C6H5CH2)4M (M=Ti, Zr, Hf; 1 - 3) and analogous 1-naphtylmethyl derivatives (1-C10H7CH2)4M (M=Ti, Zr, Hf; 4-6) do not show noticable changes in their bonding properties which were postulated on the basis of X-ray structure analyses of 1-3. On exchanging benzyl groups in 1 and 2 against halogen atoms leading to the compounds (C6H5CH2)4 - nMHaln (M=Ti, Zr, Hf; Hal=Cl, Br, I; n=1 - 3; 7-21) the δCH2 values indicate sensitively the alternation of electron density at the metal atoms. In contrast, no alternation of the benzyl group-metal bonds is indicated by the chemical shifts of the phenyl group C and H atoms, but it becomes evident when benzyl groups are substituted by Cp. Whilst in 1 - 3 a η4-coordination of the benzyl groups can be assumed, these groups are η1-bonded in Cp2Ti(CH2C6H5)2 (23) and Cp2Zr(CH2C6H5)2 (25). Furthermore, an alternation of the coordination systems could be proved in case of 3 and 6 in the presence of donor molecules (THF, pyridine).
    Notes: Die 1H- und 13C-NMR-Spektren (T 298 K, C6D6) der Tetrabenzylverbindungen (C6H5CH2)4M (M=Ti, Zr, Hf; 1-3) und der benzylanalogen 1-Napthylmethyl-Derivate (1-C10H7CH2)4M (M=Ti, Zr, Hf; 4-6) lassen keine besonderen Bindungsverhältnisse erkennen, die aufgrund von Röntgenstrukturuntersuchungen bei 1-3 vermutet wurden. Bei einem Austausch von Benzylgruppen in 1 und 2 gegen Halogenatome, d.h. in Verbindungen des Typs (C6H5CH2)4 - nMHaln (M=Ti, Zr, Hal=Cl, Br, I; n=1 - 3; 7-21), zeigt δCH2 empfindlich die veränderte Elektronendichte an den Metallatomen an. Demgegenüber werden aus den chemischen Verschiebungen der Phenyl-C- und -H-Atome keine Veränderungen der Art der Benzyl-Metall-Bindung sichtbar. Diese zeigen sich jedoch beim schrittweisen Austausch von Benzylgruppen gegen Cp-Reste. Während in 1-3 eine η4- Koordination der Benzylreste anzunehmen ist, liegen in Cp2Ti(CH2C6H5)2 (23) und Cp2Zr(CH2C6H5)2 (25) η1-gebundene Benzylgruppen vor. - In Gegenwart von Donorliganden (THF, Pyridin) wird für 3 und 613C-NMR-spektroskopisch ebenfalls eine Änderung der Bindungsart der Organylreste an das Zentralatom nachgewiesen.
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1397-1402 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Diazo Compounds, 691) - 2-(or 4-)(Diazomethyl)-2-(or 4-)H-benzopyrans - Synthesis by Electrophilic Diazoalkane Substitution and Catalytic DecompositionElectrophilic diazoalkane substitution of the (diazomethyl)phosphoryl compounds 9a-c with the benzopyrylium tetrafluoroborate 8 yields the 2-[diazo(phosphoryl)methyl]-2H-1-benzopyrans 10a-c and the 4-isomers 11a-c. Lithiated methyl diazoacetate reacts analogously with 8 under formation of 10d and 11d. At the μ-allylpalladium chloride catalyzed decomposition of 10a-d the benzoxepines 14a-d are formed by ring enlargement reaction; 1,2-H shift is responsible for the additional formation of the 2-methylene-2H shift is responsible for the additional formation of the 2-methylene-2H-benzopyrans 15b and c in the case of 10b and c. The catalytic decomposition of 11a-d proceeds exclusively in the sense of an intramolecular [2 + 1] cycloaddition to afford the 3,4-dihydro-2,3,4-metheno-2H-benzopyrans 18a-d. The benzoxepines 14a,d are characterized by photochemical electrocyclic reaction to 19a and b.
    Notes: Elektrophile Diazoalkansubstitution der (Diazomethyl)phosphoryl-Verbindungen 9a-c mit dem Benzopyrylium-tetrafluoroborat 8 liefert die 2-[Diazo(phosphoryl)methyl]-2H-1-benzopyrane 10a-c und die 4-Isomeren 11a-c. Lithiierter Diazoessigsäuremethylester reagiert analog mit 8 unter Bildung von 10d und 11d. Bei der μ-Allylpalladium-chlorid-katalysierten Zersetzung von 10a-d entstehen die Benzoxepine 14a-d durch Ringerweiterungsreaktion; 1,2-H-Verschiebung ist für die zusätzliche Bildung der 2-Methylen-2H-benzopyrane 15b und c im Fall von 10b und c verantwortlich. Die katalytische Zersetzung von 11a-d verläft ausschließlich im Sinne einer intramolekularen [2 + 1]-Cycloaddition zu den 3,4-Dihydro-2,3,4-metheno-2H-benzopyranen 18a-d. Die Benzoxepine 14a,d sind durch photochemische, elektrocyclische Reaktion zu 19a und b charakterisiert.
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  • 79
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition Metal-Substituted Diphosphenes, IX1). - Synthesis and Structure of Metalated 1,3-Diphospha-2-propanones. - Carbonylation of Diphosphenyl ComplexesThe diphosphenyl complexes (η5-C5Me5)(CO)2M-P=P-Ar (3) (M=Fe, Ru, Os; Ar=2,4,6-t-Bu3C6H2) react with Fe2(CO)9 to yield adducts such as (η5-C5Me5)(CO)2M[Fe(CO)4]P=P-Ar(4) as well as the 1,3-diphospha-2-propanone complexes [(η5-C5Me5)-(CO)2M-P(CO)PAr]Fe2(CO)6 (5) by catalytic carbonylation of the activated P=P double bond. The structures of 4a and 5a are established by X-ray diffraction studies.
    Notes: Die Diphosphenyl-Komplexe (η5-C5Me5)(CO)2M-P=P-Ar (3) (M=Fe, Ru, Os; Ar=2,4,6-t-Bu3C6H2) reagieren mit Fe2(CO)9 zu Addukten des Typs (η5-C5Me5)(CO)2M[Fe(CO)4]P=P-Ar(4) und den 1,3-Diphospha-2-propanon-Komplexen [(η5-C5Me5)-(CO)2M-P(CO)PAr]Fe2(CO)6 (5). Offensichtlich entsteht 5 aus 3 durch katalytische Carbonylierung der aktivierten P=P-Funktion. Von 4a und 5a wurden Röntgenstrukturanalysen durchgeführt.
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1403-1412 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Structure, and Some Reactions of Tris- and Tetrakis(diphenylphosphino)allenesTreatment of the reagent 2, obtained from 1-(diphenylphosphino)-1-propyne (1) and n-BuLi, with Ph2PCl gives high yields of tetrakis(diphenylphosphino)allene (3). On oxidation with H2O2 or Me3SiOOSiMe3, this compound yields the tetraoxide 4a, while with sulfur or selenium the tetrachalcogenides 4b,c are obtained. The allene group is not affected in these processes. In the reaction of 3 with MeLi P - C cleavage occurs to give Ph2PMe and 1,3,3-tris(diphenylphosphino)allenyllithium (5), which is converted into tris(diphenylphosphino)allene (Ph2P)2C=C=CHPPh2 (6) upon hydrolysis. Quaternization with MeI under mild conditions leads to the monoquaternary salts 7 and 8 from 3 and 6, respectively. With excess MeI at higher temperature a phosphonioalkynyl-semiylide salt [(MePh2P)2C-C≡C-PPh2Me]2+ 2 I- (9) is formed from both 3 and 6. The by-product of the P-C cleavage in 3 by MeI is Ph2PMe2+ I-3. - The structures of the allenes 3 and 6 and of the salt 9 have been confirmed by single crystal X-ray diffraction. The Ph2P groups in 3 adopt a similar conformation as found previously for (Ph2P)2C=CH2, with an opposite orientation of the lone pairs of electrons at phosphorus relative to the allene axis. In 6 a rotamer with an approximately symmetrical (“anti”) orientation of the geminal Ph2P groups is present. 9 is found to be another example of semiylidic quaternary salts with a delocalized ylide function.
    Notes: Das aus 1-(Diphenylphosphino)-1-propin (1) mit n-BuLi erhältliche Reagens Ph2P-C≡C-CH2Li(2) ergibt bei der Behandlung mit Ph2PCl hohe Ausbeuten an Tetrakis(diphenylphosphino)allen (3). Diese Verbindung liefert nach Oxidation mit H2O2 oder Me3SiOOSiMe3 das Tetraoxid 4a, mit Schwefel oder Selen die entsprechenden Tetrachalkogenide 4b,c. Die Allengruppierung wird dabei nicht angegriffen. Durch Umsetzung von 3 mit MeLi kommt es zur Spaltung einer P-C-Bindung. Das neben Ph2PMe gebildete 1,3,3-Tris(diphenylphosphino)allenyllithium (5) kann durch Hydrolyse in (Ph2P)2C=C=CHPPh2 (6) verwandelt werden. Bei schonender Quartärisierung mit MeI entstehen aus 3 und 6 die Monoquartärsalze 7 und 8, mit überschüssigem Reagens bei erhöhter Temperatur dagegen als gemeinsames Produkt das Phosphonioalkinyl-semiylid-Salz [(MePh2P)2C-C≡C-PPh2-Me]2+ 2 I- (9). Nebenprodukt der auch hierbei in 3 eintretenden P-C-Spaltung ist Ph2PMe2+ I-3. - Die Strukturen der Allene 3 und 6 sowie des Salzes 9 wurden durch Röntgenbeugungsanalysen an Einkristallen gesichert. Die Ph2P-Gruppen in 3 besitzen ähnliche Konformationen wie im analogen (Ph2P)2C=CH2 mit jeweils entgegengesetzten Orientierungen der freien Elektronenpaare an den P-Atomen zur Allen-Achse. In 6 ist ein Rotameres mit annähernd symmetrischer (“anti”) Orientierung der geminalen Ph2P-Gruppen vorhanden. 9 ist ein weiteres Beispiel für Semiylid-Quartärsalze mit delokalisierter Ylid-Funktion.
    Additional Material: 3 Ill.
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  • 81
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1413-1419 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkylierung der 5-Stellung von Triessigsäurelacton durch [2,3]-sigmatrope Umlagerung von Sulfonium-YlidenDie Reaktionen von 4-Methoxy-6-(phenylthiomethyl)-2H-pyran-2-onen 4 mit drei verschiedenen Diazoverbindungen unter Kupfer- oder Rhodium-Katalyse liefern entsprechende Sulfonium-Ylide, die durch [2,3]-sigmatrope Umlagerung und nachfolgende Prototropie die Pyrone 6, die an der schwer zugänglichen 5-Stellung funktionalisiert sind, ergeben. Entschwefelung von 6 mit desaktiviertem Raney-Nickel ergibt die Pyrone 17-19. Der Einfluß der experimentellen Bedingungen auf die Konkurrenz von [2,3]-sigmatroper und Stevens-Umlagerung wurde bei der Reaktion von 4-Methoxy-6-(phenylthiomethyl)-2H-pyran-2-on (4a) mit Diazomalonsäure-dimethylester studiert. Zusammen mit den aus [2,3]-sigmatroper und Stevens-Umlagerungen abgeleiteten Verbindungen 6d und 8 wurden noch andere Produkte (9, 10 und 11), die über Sulfonium-Ylid-Gleichgewichtseinstellung und Radikalverknüpfung entstehen, isoliert.
    Notes: Reactions of the 4-methoxy-6-(phenylthiomethyl)-2H-pyran-2-ones 4 with three different diazo compounds under copper or rhodium catalysis give the corresponding sulphonium ylides, which through [2,3] sigmatropic rearrangement and further prototropy afford the pyrones 6, functionalized at the difficutly accessible position C-5. Desulphurations of products 6 with deactivated Raney nickel give the pyrones 17-19. The influence of the experimental conditions on the competition between [2,3] sigmatropic and Stevens rearrangement has been studied for the reaction of 4-methoxy-6-(phenylthiomethyl)-2H-pyran-2-one (4a) and dimethyl diazomalonate. Several products (9, 10, and 11) arising from sulphonium ylides equilibration and radical recombination have been found in addition to the [2,3] sigmatropic and the Stevens rearrangement products 6d and 8.
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  • 82
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1427-1431 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Heterocyclische β-Enaminoester, 481). - Heterokondensierte Pyridine durch Cycloaddition-Extrusion-Sequenz bi- und tricyclischer 1,3-Oxazinone mit N,N-Diethyl-1-propinylaminDihalogentriphenylphosphorane überführen die N-benzoylierten 2-Amino-4,5-dihydrofuran- (5b), -pyrrol- (7b), -isoxazol- (9b) und -oxazol-3- oder-4-carbonsäure-ethylester (11b) in die heterokondensierten 1,3-Oxazinone 6, 8, 10 und 12. Mit N,N-Diethyl-1-propinylamin ergeben diese und die bereits beschriebenen 1,3-Oxazinone 1a,b, 2a,b und 3 regiospezifisch in einer Cycloadditions-Extrusions-Sequenz die entsprechenden heterokondensierten Pyridine 13a,b, 14a,b, 15a,b, 16-21, von denen 15b und die 4-Oxonaphthyridine 16, 17 Beispiele für die Insertion des Acetylen-Reagens darstellen.
    Notes: Dihalotriphenylphosphoranes convert the N-benzoylated ethyl 2-amino-4,5-dihydrofuran- (5b), -pyrrole- (7b), -isoxazole- (9b), and -oxazole-3- or-4-carboxylates (11b) into heterocondensed 1,3-oxazinones 6, 8, 10, and 12. Treatment with N,N-diethyl-1-propynylamine of these compounds as well as the already known 1,3-oxazinones 1a,b, 2a,b, and 3 results in a regiospecific cycloaddition-extrusion sequence to afford the corresponding heterocondensed pyridines 13a,b, 14a,b, 15a,b, and 16-21. Of these 15b and the 4-oxonaphthyridines 16, 17 represent examples of insertion of the acetylene reagent.
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  • 83
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1433-1435 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Short-wavelength triphenylene-sensitized UV irradiation of the furo[2,3-d]pyrimidines 2a-c leads to homolysis and rearrangement with formation of the 5,7-diazaspiro[2.5]octanes 3a-c. Employing the 6,6-dimehtyl derivative 2d, homolysis gives A and subsequent ∊-H abstraction (Norrish-type II) furnishes B ⇄ C; radicalic hydroxylation in 5-position (from THF peroxide) finally leads to 5-hydroxy-2,4,6-trioxo-5-propenylpyrimidine 3d.
    Notes: No Abstract
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  • 84
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbene-Analgous Reactions of the Products of Dehalogenation of Dichloro(diisopropylamino)borane with Aromatic Compounds and 1,2-DimethoxyethaneSodium complexes of aromatic compounds in 1,2-dimethoxyethane react with dichloro-diisopropylamino)borane to give compounds formed via carben(oidal) intermediates: From naphthalene 1,2-bis(diisopropylamino)-1,1a,2,8b-tetrahydroborireno[2,3-b][3]benzoborepine (1) is formed. From acenaphthylene 2-(diisopropylamino)-2,3-dihydro-1H-naphtho[1,8-cd]borine (2) and with 1-methylnaphthalene, in addition to 1,2-bis[(diisopropylamino)methoxyboryl]ethyne (3), (diisopropylamino)dimethoxyborane (4) is isolated. 1H-, 11B-, 13C-, 14N-, 15N NMR and MS data are given. For 3 the X-ray structure is reported.
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  • 85
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1441-1443 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photoelectron Spectrum and Electronic Structure of 4-Butadiynylmorpholine, an Amino-Substitued 1,3-DiyneThe PE spectrum of the title compound 1 has been obtained. Based on MNDO calculations, the ionization potentials have been assigned to molecular orbitals of the amino-substituted 1,3-diyne. Besides the n orbitals of the electron lone-pairs of the morpholine ring, there are two pairs of occupied π MOs of the diyne. One pair of π MOs interacts strongly with the n(N) MO, while the other one corresponds to those of unsubstituted butadiyne. MNDO calculations indicate a pyramidal configuration of the nitrogen atom with a rather low inversion barrier.
    Additional Material: 3 Ill.
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  • 86
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1445-1446 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ethylidenephosphorane - Ethenylfluorophosphorane (2λ5σ4P-λ5σ5P) Rearrangement2-Methoxy-1,3,2-dioxaphospholane (4) reacts with 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (1) to furnish 2-methoxy-2-[2,2,2,-trifluoro-1-(trifluoromethyl)ethylidene]-1,3,2λ 5σ5-dioxaphospholane (6) which rearranges upon standing at ambient temperature to form 2-[2,2-difluoro-1-(trifluoromethyl)ethenyl]-2-fluoro-2-methoxy-1,3,2λ5σ5-dioxaphospholane (7).
    Notes: No Abstract
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  • 87
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1447-1448 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sulfur Diimdides Containing Thioarsinyl and Selenoarsinyl SubstituentsWhile bis(di-tert-butylphosphino)sulfur diimide, S(N-PtBu2)2 (1a), readily adds both elemental sulfur and selenium below 0°C to give 1: 2 adducts S[N - P(Y)tBu2]2 [Y=S (1b), Se (1b), Se (1c)], the analogous bis(di-tert-butylarsino)sulfur diimide, S(N - AstBu2)2 (2a), is almost unreactive under comparable conditions. However, thioarsinyl sulfur diimide, S[N - As(S)tBu2]2 (2b), can be obtained from K2SN2 and two equivalents of tBu2As(S)Cl. In contrast to sulfur, selenium is slowly attached to the arsino centers of 2a in toluene solution at 25°C to give both the di- and the monoselenium adduct, S[N-As(Se)tBu2]2 (2c) and tBu2As(NSN)As(Se)tBu2 (2d), respectively.
    Notes: No Abstract
    Additional Material: 2 Tab.
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  • 88
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1449-1450 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: BF3. OEt2-catalyzed reaction of cyclic thioureas (1) with 2-benzylidenecycloalkanones (2) afforded tricyclic 1,3-thiazines (3, 4). The progress of the reactions was found to depend on the ring size of both 1 and 2.
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  • 89
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1451-1453 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Catalytic Synthesis of 5-Benzylidenehydantoins from Alkyl Isocyanates and PhenylacetyleneNew 5-benzylidenehydantions 1-4 have been prepared from alkyl isocyanates and phenylacethylene in the presence of various ruthenium clusters as catalyst precursors. All products have been separated into the expected Z and E isomers.
    Notes: No Abstract
    Additional Material: 2 Tab.
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  • 90
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1455-1459 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of 1λ6- and 1λ4-1,2,6,-Thiadiazines from S,S-Dialkylsulfur Diimides1λ6,2,6-Thiadiazines 4a-h, 1λ4,2,6-Thiadiazines 5a-k, 6a,b, and ring-open products 3a-o are synthesized by reaction of dialkylsulfur diimides 1a-g with ethylene derivatives 2a-h. 1λ6,2,6-Thiadiazines 4h,b,c can be converted into 1λ4,2,6-Thiadiazines 5j, 6a,b under acid catalysis. The ring-open product 3n leads to 1λ6,2,6-thiadiazine 4a when heated with base.
    Notes: No Abstract
    Additional Material: 3 Tab.
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  • 91
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 735-745 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The results of semiempirical MNDO calculations on bond lengths, heats of formation, and net atomic charges of compounds 6, 7, and 8, which all contain an N-alkylpyridinium moiety (see Table 1), allow general trends to be recognized. These trends allow the prediction of important reactivity characteristics of this series of compounds and were the reason for the synthesis of compounds 9, 24, and 26 and for tests of their usefulness. Specifically, the C1-N2 bond length serves as a useful criterion for the reactivity with nucleophilic partners, especially in combination with thermodynamic data calculated from reactions (3) and (4) (Tables 3 and 4). In 7 and 8, this bond is very long as a consequence of an extreme anomeric effect. This observation is reflected in the (experimentally tested) property of the complexes 9 to split off the pyridine moiety. The Cl atom in 6a does not influence the C1-N2 bond length but it does activate the C1 atom toward nucleophilic attack and can itself function as the leaving group [see eq. (10)]. - A remarkable example, both on the basis of the MNDO results (using the model compound 6i) and from the experimental viewpoint, was observed for the class of compounds 24a. The calculated C1-N2 bond length of 6i (1.563 Å) could be classified as adequate for nucleophilic substitution of the pyridine moiety controlled by the anomeric effect on the basis of experimental tests. Whereas “normal” N-alkylpyridinium salts (e.g. the N-methylpyridinium cation, 6b) are hardly ever attacked in the C1 position, the preparative usefulness of this structural element can now be considerably increased by use of the anomeric effect. This is demonstrated by the synthesis of compounds 5, 9h, 17, and 22 from 9, 25a and 25b from 24a as well as 27a from 26a.
    Notes: Ergebnisse aus semiempirischen (MNDO)-Berechnungen der Bindungslängen, Bildungsenergeien und Überschußladungen solcher Verbindungsklassen 6, 7 und 8, die als gemeinsames Strukturelement einen N-Alkylpyridinium-Molekülteil besitzen (vgl. Tab. 1), lassen allgemeingültige Trends erkennen, mit deren Hilfe wichtige Reaktivitätsmerkmale dieser Reihe vorhergesagt werden können und somit Anlaß zur gezielten Herstellung der Beispiele 9, 24 und 26 und deren erste Verwendungstests waren: Insbesondere die C1-N2-Bindungslänge kann bei Umsetzungen mit nucleophilen Reaktionspartnern - bei zusätzlicher Berücksichtigung der entsprechend Gl. (3) und (4) berechneten thermodynamischen Daten (Tab. 3 und Tab. 4) - als ein zuverlässiges Beurteilungskriterium dienen. Diese Bindung ist in 7 und 8 infolge eines extremen anomeren Effekts sehr lang, ein Befund, der sich in der (experimentell überprüften) Eigenschaft der Komplexe 9, den Pyridiniumteil besonders leicht abzuspalten, widerspiegelt. Das Cl-Atom in 6a ist auf die genannte Bindungslänge ohne Einfluß, es erleichtert jedoch den nucleophilen Angriff auf das C1-Zentrum und kann selbst zur Abgangsgruppe werden [vgl. Gl. (10)]. - Ein sowohl aufgrund der MNDO-Ergebnisse (Berechnung des Modells 6i) als auch aus experimenteller Sicht bemerkenswertes Beispiel manifestiert sich als Konsequenz dieser überlegungen in der Substanzklasse 24a: Die berechneten C1-N2-Bindungslänge von 6i (1.563 Å) konnte durch experimentelle Tests [G1. (9)] als hinreichend für die durch den anomeren Effekt gesteuerte nucleophile Substitution des Pyridiniumteils in 24a klassifiziert werden. Während also “normale” N-Alkyl-pyridiniumsalze (z. B. das N-Methylpyridinium-Kation 6b) kaum an der C1-Position angreifbar sind, kann durch gezielte Ausnutzung des anomeren Effekts das präparative Anwendungsspektrum dieses Strukturelements nunmehr deutlich erweitert werden (hier umrissen durch die Herstellung der Verbindungen 5, 9h, 17 und 22 aus 9, 25a und 25b aus 24a sowie 27a aus 26a).
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  • 92
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The rhodium complexes SbF6 (5a, b) [R=Ph (a), c-C6H11 (b)] are obtained by Cl- abstraction from ClRh(COD)PR2CH2C4H7O (3a, b) with AgSbF6. 3a, b result from [μ-ClRh(COD)]2 (1) and the P,O ligands R2PCH2C4H7O (2a, b). Complex 5b is also formed from [Rh(COD)(THF)2]SbF6 (4) and 2b. As was demonstrated with the cis complexes PF6 (8a, b), the introduction of a second ligand 2a, b succeeds either by COD elimination from [Rh(COD)-(PPh2CH2C4H7O)2]PF6 (6a) or by an one-pot reaction of [μ-ClRh(COE)2]2 (7) with 2a, b and NaPF6. In the presence of excess COD 8a is reversibly transformed into 6a with cleavage of two Rh-O bonds. In contrast to 8a, 8b reacts with hydrogen to give the cis hydrido compound PF6 (9b) with reorientation of the P,O ligands from cis to trans, being only stable in solution under an atmosphere of hydrogen. Upon the oxidative addition of CH3I (13CH3I) to 8b, leading to cis-PF6 (10b and 10′b, respectively), also the kinetic instability of the Rh-O bond is of importance. With cleavage of the Rh-O bond 8a, b react with CO (13CO) to give the trigonal-bipyramidally configurated complexes [(OC)3Rh(PR2CH2C4H7O)2]PF6 (11a, b and 11′a, b, resp.) with trans-arranged P,O ligands. As a result of CO (13CO) elimination and reversible Rh-O bond formation 11b and 11′b (13CO enriched) are tranformed into the trans-P configurated complexes PF6 (12b and 12′b, resp.), showing fluctional behaviour at 20°C in the 31P{1H}-NMR spectrum, regarding the Rh-O bond.
    Notes: Die Rhodium-Komplexe SbF6 (5a, b) [R=Ph (a), c-C6H11 (b)] erhält man durch Cl--Abstraktion aus ClRh(COD)PR2CH2C4H7O (3a, b) mit AgSbF6. 3a, b entstehen aus [μ-ClRh(COD)]2 (1) und den P,O-Liganden R2PCH2-C4H7O (2a, b). Komplex 5b bildet sich auch aus [Rh(COD)-(THF)2]SbF6 (4) und 2b. Die Einführung eines zweiten Liganden 2a, b gelingt, wie mit den cis-Komplexen PF6 (8a, b) gezeigt wird, entweder durch COD-Abspaltung aus [Rh(COD)(PPh2CH2C4H7O)2]PF6 (6a) oder durch Eintopfreaktion von [μ-ClRh(COE)2]2 (7) mit 2a, b und NaPF6. In Gegenwart von überschüssigem COD geht 8a reversibel unter Spaltung von zwei Rh-O-Bindungen in 6a über. Im Gegensatz zu 8a reagiert 8b mit Wasserstoff unter Umorientierung der P,O-Liganden von cis nach trans zur cis-Hydrido- Verbindung PF6 (9b), die nur in Lösung unter H2- Atmosphäre beständig ist. Bei der oxidativen Addition von CH3I (13CH3I) an 8b, die zu cis-PF6 (10b bzw. 10′b) führt, spielt ebenfalls die kinetische Labilität der Rh-O-Bindung eine Rolle. Unter öffnung der Rh-O-Bindung reagieren 8a, b mit CO (13CO) zu den trigonalbipyramidal konfigurierten Komplexen [(OC)3Rh(PR2CH2-C4H7O)2]PF6 (11a, b bzw. 11′a, b) mit trans-ständigen P,O-Liganden. 11 b bzw. 11′b (13CO-angereichert) eliminiert CO (13CO) und geht dabei unter reversibler Rh-O-Knüpfung in den trans-P-konfigurierten Komplex PF6 (12b bzw. 12′b) über, der bezüglich der Rh-O-Bindung bei 20°C im 31P{1H}-NMR-Spektrum fluktuierendes Verhalten zeigt.
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  • 93
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The reaction of NH2NHC(O)SMe with MoO2(S2CNEt2)2 and MoO2(ONEt2)2 yields the diazenido-hydrazido complexes [Mo(NNC(O)SMe)(NH2NC(O)SMe)(S2CNEt2)2] · CH2Cl2 (2) and [(μ-OMe)Mo(NNC(O)SMe)(NH2NC(O)SMe)(ONEt2)]2 (4), respectively. X-ray structure analysis shows that 2 contains the side-on hydrazido(1 - ) ligand NH2NC(O)SMe, whereas in 4 the same ligand is N,O-chelated. In 2 the Mo - N distances are 213.1(7) and 213.4(5) pm, the N - N distance is 140.4(9) pm. The nitrogen atoms are sp3 hybridized. Possible factors influencing the coordination mode of hydrazido(1 - ) ligands, i.e. side on, end on, or chelating, are discussed.
    Notes: Die Reaktion von NH2NHC(O)SMe mit MoO2(S2CNEt2)2 und MoO2(ONEt2)2 ergibt die Diazenido-Hydrazido-Komplexe [Mo(NNC(O)SMe)(NH2NC(O)SMe)(S2CNEt2)2] · CH2Cl2 (2) bzw. [(μ-OMe)Mo(NNC(O)SMe)(NH2NC(O)SMe)(ONEt2)]2 (4). Röntgenstrukturanalysen von 2 und 4 ergaben, daß der Hydrazido(1 - )-Ligand NH2NC(O)SMe in 2 symmetrisch “side on”, im dimeren 4 dagegen als N,O-Chelat gebunden ist. Die Mo-N-Abstände in 2 betragen 213.1(7) und 213.4(5) pm, der N - N-Abstand 140.4(9) pm. Die Stickstoffatome sind sp3-hybridisiert. Mögliche Faktoren für die “side-on”-, “end-on”-oder chelatartige Koordination von Hydrazido(1 - )-Liganden werden diskutiert.
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  • 94
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    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 803-809 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The enantiomers (M) and (P) of a series of similar aromatic carboxamides have been, for the first time, investigated analytically and enriched preparatively by liquid chromatography on triacetylcellulose. Enantiomeric purities (7-99%), specific rotations, and barriers to rotation about the C(sp-C(sp bond (87-120 kJ/mol, Table 5) were determined. These energies are discussed in terms of the size of ortho substituents and of the buttressing effects by meta substituents.
    Notes: Die Enantiomeren (M) und (P) einer Reihe verwandter aromatischer Carbonsäureamide wurden erstmals mittels Flüssigkeits-Chromatographie an Triacetylcellulose analytisch untersucht und präparativ angereichert. Enantiomerenreinheiten (7-99%), spezifische Drehungen und Schwellen der Rotation um die C(sp-C(sp-Bindung (87-120 kJ/mol, Tab. 5) wurden ermittelt. Diese Energiebeträge werden im Hinblick auf den Raumbedarf von ortho-Substituenten und die Stützeffekte durch meta-Substituenten diskutiert.
    Additional Material: 10 Tab.
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  • 95
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 811-814 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The cationic [3,3-bis(tert-butyl)-2-azoniaallenylidene]pentacarbonyl complexes [(CO)5M(CNC(tBu)2)]⊖ AlBr4⊕ (2) [M=Cr (a), W (b)] which are synthesized by the reaction of (CO)5M-[C(OEt)N=C(tBu)2] (1) with AlBr3, react with tetrahydrofuran via addition of Br⊖ to give the isocyanide complexes (CO)5M-C≡N-C(tBu)2Br (3). Under nitrogen at room temperature, 3b decomposes in solution within ca. two hours to give the binuclear diisocyanide complex [(CO)5W-C≡N]2C(tBu)2 (4b). When the same conditions are applied to solutions of 3b in the presence of oxygen or of galvinoxyl 3b is stable. The structure of 4b was confirmed by an X-ray analysis.
    Notes: Die kationischen [3,3-Bis(tert-butyl)-2-azoniaallenyliden]pentacarbonyl-Komplexe [(CO)5M(CNC(tBu)2)⊖ (2) [M=Cr (a), W (b)] - darstellbar durch Umsetzung von (CO)5M[C(OEt)- N=C(tBu)2] (1) mit AlBr3 - reagieren mit Tetrahydrofuran unter Addition von Br⊕ zu den Isocyanid-Komplexen (CO)5M - C≡N-C(tBu)2Br (3). Bei Raumtemperatur zersetzt sich 3b unter Stickstoff in Lösung innerhalb von ca. zwei Stunden zu dem zweikernigen Diisocyanid-Komplex [(CO)5W-C≡N]2C(tBu)2 (4b), in Gegenwart von Sauerstoff oder von Galvinoxyl ist 3b unter ansonsten gleichen Bedingungen stabil. Die Struktur von 4b wurde durch eine Röntgenstrukturanalyse gesichert.
    Additional Material: 1 Ill.
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  • 96
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The crystal structure of arene 3 and heteroarenes 4, 5 has been determined by X-ray diffraction. Steric overcrowding in the vic-tri-tert-butyl-substituted part of the molecules causes the aromatic rings to deviate strongly from planarity. Unsymmetrical boat conformations are found in all cases (bow and stern angles: 30.1 and 11.6° in 3, 25.5 and 12.9° in 4), the boat in 5 being rather twisted. Compound 3 represents the most strongly deformed non-bridged and non-condensed benzene derivative for which experimental data are available. Phosphinine 5 has the most distorted non-bridged and non-condensed 6π aromatic system known so far.
    Notes: Die Kristallstruktur der Arene bzw. Heteroarene 3, 4 und 5 wurde durch Röntgenbeugung bestimmt. Die mit dem vic-Tri-tert-butyl-Substitutionsmuster verbundene räumliche überfüllung führt zu einer starken Abweichung der aromatischen Ringe von der Planarität. In allen Fällen liegen unsymmetrische Bootkonformationen vor (Bug- und Heckwinkel: 30.1 und 11.6° in 3, 25.5 und 12.9° in 4), wovon die in 5 stark verdrillt ist. Die Verbindung 3 ist das am stärksten deformierte, nichtüberbrückte und nichtkondensierte Benzolderivat, für das bislang experimentelle Strukturdaten vorliegen; das Phosphinin 5 ist der am meisten verzerrte 6π-Aromat dieser Art überhaupt.
    Additional Material: 3 Ill.
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  • 97
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 847-848 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The diazonium ions 13 have been generated by alkaline cleavage of the analogous nitrosocarbamate 12. The product distribution indicates little participation of the hydroxy group (0.4% 9) while the allyl cation 14 arising from 13 undergoes intramolecular (4.3% 17) as well as intermolecular (75% 16) nucleophilic substitution.
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  • 98
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 853-854 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Upon treatment with trihaloboranes 2b-d the phenyltrimethylsilanes 1, 6, 8, and 10 yield the corresponding phenyldihaloboranes 3, 7, 9, and 11 with high selectivity. Benzylsilanes are not attacked.
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  • 99
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The methyl cyclobutadienecarboxylate 1a adds methyl propiolate (2a) to the regioisomeric Dewar benzenes 3a (73%) and 4a (19%). In contrast, the corresponding tert-butyl carboxylate 1b reacts with the same dienophile as well as the acceptor-substituted olefines 2b and c exclusively by formation of the Dewar benzenes 3b-d (68-82%). - Both Dewar benzenes 3a and b are smoothly transformed into the benzenes 5a and b by thermal means. Photolyses of both aromatic compounds do not lead back to 3a and b but produce the Dewar isomers 7a and b, which finally undergo intramolecular [2+2] cycloaddition to give the prismanes 9a and b. A fundamentally comparable reaction sequence can be achieved with 4a (→ 6a → 8a → 9a). Reaction branching is observed on thermolysis of 9b: On the one hand the benzene 5b (54%) accompanied with 10% of the Dewar benzene 7b, on the other hand a 1:1 mixture of the aromatic compounds 6b and c is obtained. - Photochemically the Dewar benzenes 3a and b can directly be converted into the prismanes 10a and b (97 and 86%, respectively). Prismane/prismane isomerization (10 → 16) succeeds as a consequence of a thermal (10a,b → 12a,b) as well as of two light-induced reaction steps (12a,b → 14a,b and 14a,b → 16a,b). In an analogous way, the prismane 11 is received from 4a and then transformed into the isomer 16 via 13 and 15. As a special feature of the thermolysis of 11 the formation of 12a has to be noted, a reaction which is explained by the benzvalene intermediate 25. - The crystal structure analysis of 10b shows an evident influence of only one of both carbonyl groups (methylester) onto the prismane skeleton. This is manifested by two long, vicinal [C1-C2 1.579(3) and C1-C6 1.567(3) Å] and a short distal three-membered ring bonds [C2-C6 1.528(3) Å]. Furthermore, the C1-C4 bond [1.506(4) Å] is shortened relative to the C2-C3 distance [1.553(3) Å], whereas the C5-C6 bond [1.594(3) Å] is prolonged by the strong repulsion of both tBu groups.
    Notes: Der Cyclobutadiencarbonsäure-methylester 1a addiert Propiolsäure-methylester (2a) zu den regioisomeren Dewar-Benzolen 3a (73%) und 4a (19%). Dagegen entstehen aus dem entsprechenden tert-Butylester 1b und dem gleichen Dienophil sowie den akzeptorsubstituierten Olefinen 2b und c ausschließlich die Dewar-Benzole 3b-d (68-82%). - Thermisch gehen die beiden Dewar-Benzole 3a und b glatt in die Benzole 5a und b über. Photolysen der Aromaten führen nicht zu 3a und b zurück, sondern zu den Dewar-Isomeren 7a und b, die schließlich intramolekulare [2+2]-Cycloaddition zu den Prismanen 9a und b eingehen. Mit 4a läßt sich eine grundsätzlich vergleichbare Reaktionsfolge realisieren (→6a →8a →9a). Reaktionsverzweigung beobachtet man bei der Thermolyse von 9b: Einerseits erhält man das Benzol 5b (54%) neben 10% Dewar-Benzol 7b, andererseits ein 1:1-Gemisch aus den Aromaten 6b und c. - Photochemisch lassen sich die Dewar-Benzole 3a und b direkt in die Prismane 10a und b (97 bzw. 86%) umwandeln. Prisman/Prisman-Isomerisierung. (10 → 16) gelingt als Folge eines thermischen (10a,b → 12a,b) sowie zweier lichtinduzierter Reaktionsschritte (12a,b → 14a,b und 14a,b → 16a,b). Entsprechend läßt sich aus 4a das Prisman 11 gewinnen und dann über 13 und 15 in das Isomer 16 umwandeln. Als Besonderheit der Thermolyse von 11 ist die Bildung von 12a zu vermerken, dessen Entstehen über die Benzvalen-Zwischenstufe 25 erklärt wird. - Die Kristallstrukturanalyse von 10b zeigt einen deutlichen Einfluß nur einer der beiden Carbonylgruppen (Methylester) auf das Prismangerüst. Er äußert sich in zwei langen, vicinalen [C1-C2 (1.579(3) und C1-C6 1.567(3) Å] und einer kurzen distalen Dreiringbindung [C2-C6 1.528(3) Å]. Dar über hinaus ist die C1-C4-Bindung [1.506(4) Å] relativ zum C2-C3-Abstand [1.553(3) Å] verkürzt, während die C5-C6-Bindung[1.594(3) Å] durch die starke Abstoßung der beiden tBu-Gruppen verlängert ist.
    Additional Material: 3 Ill.
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  • 100
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 789-794 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The reaction of the aminophosphonium methylides (Et2N)3P=CH2, Me(Et2N)2P=CH2, (Me2N)3P=CH2, or Me(Me2N)2P=CH2 (1a-d) with the chlorosilanes Me3SiCl and (t-Bu)2SiCl2, resp., yield silylated phosphonium salts 2a-d (Scheme 1). Treatment of these with strong base (KH/THF) or transylidation using a second equivalent of the ylide 1a-d affords the silylated ylides (Et2N)3P=CHSiMe3, Me(Et2N)2P=CHSi(t-Bu)2Cl, and Me(Me2N)2P=CHSi(t-Bu)2Cl (3a-c,c′,d). Attempts for further dehydrohalogenation of the latter to give species R3P=C=SiR′2 were unsuccessfull. Instead, treatment of 3d with t-BuLi/TMEDA yielded the cyclic ylide (4) whose structure was determined by single crystal X-ray diffraction. Addition of HCl (in Et2O) to 4 gives the corresponding phosphonium salt Cl (5). - For reason of comparison, the ylides Me3P=CH2, (i-Pr)3P=CH2, and Ph3P=CH2 (1e-g) were also converted (via silylated phosphonium salts) into ylides Me3P=CHSiR3, (i-Pr)3P=CHSiR3, and Ph3P=CHSiR3, where R3=(t-Bu)2Cl and (t-Bu)MeCl (3e-g). 3f can also be converted into an endocyclic ylide (6), whereas 3g, on standing in THF solution, yields the double ylide [Ph3P=C - Si(t-Bu)2]2 (7) with exocyclic ylide functions. NMR data are presented for all new ylides.
    Notes: Aus den Aminophosphonium-methyliden (Et2N)3P=CH2,Me(Et2N)2P=CH2, (Me2N)3P=CH2 oder Me(Me2N)2P=CH2 (1a-d) entstehen bei der Reaktion mit den Chlorsilanen Me3SiCl bzw. (t-Bu)2SiCl2 die silylierten Phosphoniumsalze 2a-d (Schema 1). Durch die Einwirkung starker Basen (KH/THF) oder durch Umylidierung mit einem weiteren äquivalent Ylid 1a-d werden daraus die silylierten Ylide (Et2N)3P=CHSiMe3, Me(Et2N)2P=CHSi(t-Bu)2Cl und Me(Me2N)2P=CHSi(t-Bu)2Cl (3a-c,c′,d). Eine weitere Dehydrohalogenierung der beiden letzteren Ylide zu den kumulierten Systemen R3P=C=SiR′2 gelingt nicht. Statt dessen wird bei der Einwirkung von t-BuLi/TMEDA auf 3d das cyclische Ylid (4) gebildet, dessen Struktur durch Einkristall-Röntgenbeugung gesichert wurde. 4 ergibt mit HCl in Et2O das korrespondierende Phosphoniumsalz (5). - Zu Vergleichszwecken wurden aus Me3P=CH2, (i-Pr)3P=CH2 und Ph3P=CH2 (1e-g) über die silylierten Phosphoniumsalze auch die Silyl-Ylide Me3P=CHSiR3, (i-Pr)3P=CHSiR3 und Ph3P=CHSiR3 mit R3=(t-Bu)2Cl und (t-Bu)MeCl (3e-g) dargestellt. Aus 3f konnte mit t-BuLi/TMEDA wieder ein endocyclisches Ylid (6) erhalten werden. 3g ergibt beim Lagern in THF-Lösung das Doppelylid [Ph3P=C - Si(t-Bu)2]2 (7) mit exocyclischen Ylidfunktionen. Für alle neuen Ylide werden NMR-spektroskopische Daten vorgelegt.
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