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  • Electronic Resource  (12,230)
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  • 101
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1164-1168 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Determination of Stability Constants in Ethanol for Li+-selective Ionophores by Differential Vapour Pressure OsmometryStability constants of some neutral carriers and their bridged isologues in interaction with Li+ and Na+ are determined by a differential vapour pressure osmometry method in ethanol utilizing Bjerrum formation curves. All ionophores studied induce high Li+ selectivity in solvent polymeric membranes.
    Additional Material: 1 Ill.
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  • 102
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1170-1172 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 103
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 104
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Halochromic Molecules. Synthesis and Acidobasic Properties of 3′-substituted 6,11-dihydrospiro[[1]benzopyrano[4,3-b]indol-6,9′-9′9′H-xanthenes]We have synthesized a series of 3′-substituted 6,11-ihydrospiro[6H-chromeno[4,3-b]indol-6,9′-9′H-xanthenes] and one of their respective aza analogues. 1H-MR data as well as the fragmentation in the mass spectra of starting and final products supported the postulated structures. With acid, the spiro compounds form ring-opened intensely coloured xanthylium salts. UV/VIS spectra of these salts are listed and discussed. The ∊pH* curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds could possibly be used in ‘pressure sensitive papers’.
    Additional Material: 2 Tab.
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  • 105
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1199-1215 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nitroso-arene dienophiles 1 react regiospecifically with the conjugated dienals 2 and 3a/3b, and lead thereby to the unstable Diels-Alder cycloadducts 4 and 5. These undergo two types of cascade reactions which give pyridinium betaines 6 and pyrrolo-indoles 8 as the major reaction products. The one-pot syntheses of pyrroloindoles 8 represent a new and easy access to the basic skeleton of mitomycins 10. The scope and limitations of the cascade reactions were investigated.
    Additional Material: 5 Tab.
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  • 106
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the demosponge Corallistes sp. (Tetractinomorpha, Lithistida, Corallistidae) collected in the Coral Sea, contains corallistin A (1), the second example, of a free porphyrin from a living organism. The compound proved to be active against the Kb cell line. In contrast with the geoporphyrins which do not bear any O-atom corallistin A (1) carries two carboxylic groups.
    Additional Material: 1 Tab.
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  • 107
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three chromonocoumarins ( =6H, 7H-[1]benzopyrano[4,3-b][1]benzopyran-6,7-diones) 1-3 have been isolated from the leaves and the root bark of polygala fruticosa BERG. (syn. Polygala oppositifolia L.; Polygalaceae). The structure of frutinone A (1) was established by X-ray diffraction analysis. The structures of the previously undescribed compounds frutinone B (2) and C (3) were deduced by spectroscopic methods (EI-MS, UV, IR, 1H-and 13C-NMR, including NOE and COSY) in comparison with 1. Chromonocoumarins 1-3 are the first representatives of a new type of naturally occurring compounds. Frutinone A shows strong fungicidal activity against Cladosporium cucumerinum.
    Additional Material: 1 Ill.
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  • 108
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In 7 steps, 6- or 9-hydroxylated or -methoxylated trans-octahydrobenzo[g]isoquinolines were efficiently synthesized starling from dimethoxynaphtbalenes (Scheme), as potential new selective ligands for serotonin receptors. The 6-substituted compounds had very little affinity to common neurotransmitter receptors, with the exception of adrenergic α2. The 9-substituted compounds, while showing interesting affinity for 5HT1a receptors, had comparable affinities for adrenergic α1 and β2, and in one case for dopamine D2 receptors.
    Additional Material: 2 Ill.
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  • 109
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1554-1582 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Access to the Three Subunits of the Antitumor Antibiotic CC-1065 by Hetero-Cope Rearrangement of Vinyl N-Phenylhydroxamates.The use of the hetero-Cope rearrangement of vinyl N phenylhydroxamates to indoles for the preparation of the 1,2-dihydro-3H, 6H-benzo[1,2-b:4,3-b′]dipyrrole skeleton, the structural subunits characteristic of the antitu-mor antibiotic CC-1065 as well as the phosphodiesterase inhibitors PDE-I and PDE-II is described.
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  • 110
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1537-1553 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By appropriate structural modification of known musk odorants, new strong musk odorants have been discovered. Incorporation of supplementary CH3 or CH2 groups into the basic musk skeleton of type G only slightly modifies the global shape of the molecule but leads to densely packed structures of enhanced lipophilicity. For the construction of these highly substituted 1,2,3,4-tetrahydronaphthalenes, new annulation sequences (intramolecular mono- and dialkylations; see Schemes 3,6, and 8) have been developed and, in certain cases, the design of the target molecules was dictated by both structure-activity-relationship and synthetic considerations (e.g. 46 and 47, Scheme 6). This work also presents an original solution to an analytical problem: the distinction between a C2- and a Cs-symmetrical aromatic hydrocarbon (viz. 71 and 72) by conversion into a [Cr(CO)3arene]complex.
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  • 111
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1817-1824 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound 7 is obtained by reductive dehalogenation from 4-bromo-2,3-dihydro-2,2. -dimethyl-3-oxo-1H-pyrrole-1-carboxylate (8) in 90% yield, Aza-enone 7 undergoes [2 + 2] cycloaddition from the triplet state with both electron-rich and electron-deficient alkenes. The behaviour of 7 in light-induced reactions is compared to those of 2,2-dimethyl-3(2H)-furanone (1a) and of the corresponding thiophenone 1b. In the photodimerization and the cycloaddition to either 2,3-dimethylbut-2-ene or to dimethyl maleate of these ketonic five-membered heterocycles with one heteroatom, the overall efficiency increases in going from the furan 1a to the thiophene 1b and to the pyrrole 7.
    Additional Material: 2 Tab.
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  • 112
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (1R,2S,4R)-2-Cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl (1S′)-camphanate (5) was transformed into (-)-methyl 2,5-anhydro-3,4,6-O-tris[(tert-butyl)dimethylsilyl]-D-allonate (2), (+)-1,3-diphenyl-2-{2′,3′,5′-O-tris[(tert-butyl)dimethylsilyl]-β-D-ribofuranosyl}imidazolidine (3), and the benzamide 20 of 1-amino-2,5-anhydro-1-deoxy-3,4,6-O-tris-[((tert-butyl)dimethylsily)]-D-allitol. Compound 2 was converted efficiently into optically active tiazofurin (1).
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  • 113
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Yeast reduction of rac-ethyl 2-methyl-6-oxocylohexanecarboxylate (rac-1) yielded selectively (+)-ethyl 2-hydroxy-6-methylcyclohexane carboxylate (+)-2 (Scheme 1) which has been alkylated with 5-iodo-2-methylbut-2-ene by (the dianion method to furnish the 4-methylbut-3-enyl derivat 3 (Scheme 3)). NaBH4 reduction of (+)-1 led to three hydroxy-carboxylates (-)-2, (+)-5, and (-)-6 (Scheme 4). Allylation of the dianion of (+)-5 afforded (+)-7.
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  • 114
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl Jasmonate: A Short Synthesis of Naturally Occurring Methyl Jasmonate and its Unnatural Enantiomer via Enantiodivergent Alkylation of Cyclopent-2-ene-1,3-diol Derivatives by Palladium(0)-Induced ReactionsPalladium-catalyzed alkylation of cyclopent-2-ene-1,2-diol derivatives like 2 is a useful method for enantiodivergent functionalization, resulting in both enantiomeric series of chiral building blocks. The chiral building blocks 3 and 13 can be transformed to methyl jasmonate (1)and its unnatural enantiomer ent-1, recent statement [1b] that 1 has no odour at all and that ‘methyl jasmonate's’ fragrance is actually due to its cis-isomer ent-11 has been confirmed also for the enantiomeric series.
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  • 115
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crude petroleum-ether extract of the aerial parts of Hypericum calycinum L. (Guttiferae) exhibited in vitro growth-inhibitory activity against the Co-115 human colon carcinoma cell line. Bioassay-guided fractionation of this extract allowed the isolation of the cyclohexadienone derivatives 1-5, four of which are previously undescribed compounds. The structures of the known chinesin II (1) and of 2 (hypercalin A) were established by 1H- and 13C-NMR spectroscopy and were confirmed by X-ray analysis of their crystalline mixture which revealed the complete relative configuration of both compounds. The structure of 3 (hypercalin B) was elucidated by means of extensive 1D- and 2D-NMR experiments, including DQ-COSY, HETCOR and LR-HETCOR. The structure of compound 4 (hypercalin C) was established by 1H- and 13C-NMR spectroscopy and confirmed by X-ray analysis to be the 3,5-dihydroxy-4-{[(1R*,2S*, 5S*)-2-hydroxy-2-methyl-5-(1-methylethenyl)cyclopentyl]methyl}-6,6-bis-(3-methylbut-2-enyl)-2-(2-methylpropanoyl)cyclohexa-2,4-dien-1-one. The structures of the higher isomeric homologues 5a/5b were deduced by comparison of their UV, 1H-, and 13C-NMR spectra with those of 4. The isolated compounds appeared to be related to chinesin I and II previously isolated from Hypericum chinense L. and were responsible for the growth-inhibitory activity of the extract against the Co-115 human carcinoma cell line. Moreover, 1/2 and 3 showed molluscicidal activity against the schistosomiasis-transmitting snail Biomphalaria glabrata.
    Additional Material: 3 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 1925-1925 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 117
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and NMR-Spectroscopic Characterization of New Adenine- and 6-ThioxopurinecarboxamidinesAdenine (1) or 1H-purine-6(7H)-thione (4) react with carboximidoyl chlorides 2 to yield the adenine-9-carboxamidines 3 or the 6,7-dihydro-6-thioxo-1H-purine-7-carboxamidines 5 and 6,9-dihydro-6-thioxo-1H-purine-9-carboxamidine 6 a, respectively. The structures of the compounds were determined by 1H- and 13C-NMR spectroscopy.
    Additional Material: 2 Tab.
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  • 118
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 668-674 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Activity-guided fractionation of the MeOH extract of the fruits of Tetrapleura tetraptera TAUB. (Mimosaceae) afforded 4 saponins 1-4, which exhibited strong molluscicidal properties against the schistosomiasis-transmitting snails Biomphalaria glabrata. Chemical, enzymatic, and spectral methods (DCI-MS, 1H-NMR, 13C-NMR) showed that they were N-acetylglycosides of oleanolic acid and of echinocystic acid. Apart from saponin 1 (aridanin), previously isolated from this plant, glycosides 2-4 are new naturally occurring compounds.
    Additional Material: 2 Tab.
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  • 119
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 744-755 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Condensation reactions of the 5-amino-6-(subst. amino)-2,4-dithiouracils 12 and 13 with diacetyl or benzil led to the 6,7,8-trisubstituted 2,4-dithiolumazines 14-16. Methylation of these compounds affected both thio functions forming various types of 2,4-bis(methylthio)lumazine derivatives depending on the nature of the substituents at C(7) and N(8). The 6,7,8-trimethyl-2,4-dithiolumazine (14) was converted into 7,8-dihydro-6,8-dimethyl-7-methylidene-2,4-bis(methylthio)pteridine (17), whereas the 8-methyl-6,7-diphenyl-(15) and the 8-(2-hydroxyethyl)-6,7-diphenyl-2,4-dithiolumazine (16) yielded the corresponding covalent inter- or intramolecular 7,8-adducts 18-21. The unusual structures were proven by spectroscopic means and those of the alcohol adducts 20 and 21, furthermore, confirmed by X-ray analysis.
    Additional Material: 3 Ill.
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  • 120
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (E)-5-Demethyl-4-oxo-β-ionone (2), (E)-4-oxo-β-ionone (3), (E)-4-oxo-β-irone (4), and the five-membered ring analogs 36-41 were synthesized by a novel, convergent route starting from 2-methylfuran (1). A recently discovered, intramolecular reaction of 2-(diazoacyl)furans, catalyzed by dirhodium tetraacetate, leading to dienediones served as key step, thereby testing its utility in natural-product synthesis for the first time.
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  • 121
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethyl (1R, 2S)-2-hydroxycyclopentanecarboxylate and -cyclohexanecarboxylate (1a and 2a, respectively) obtained in 40 and 70% yield by reduction of 3-oxocyclopentanecarboxylate and cyclohexanecarboxylate, respectively (Scheme 2), with non-fermenting yeast, are converted to bicyclic dioxanone derivatives 3 and 4 with formaldehyde, isobutyraldehyde, and pivalaldehyde (Scheme 3). The Li-enolates of these dioxanones are alkylated (→5a-5i, 5j, 6a-6g), hydroxyalkylated (→51, m, 6d, e), acylated (→5k, 6c) and phenylselenenylated (→7-9) with usually high yields and excellent diastereoselectivities (Scheme 3, Tables and 2). All the major isomers formed under kinetic control are shown to have cis-fused bicyclic structures. Oxidation of the seleno compounds 7-9 leads to α, β-unsaturated carbonyl derivatives 10-13 (Scheme 3) of which the products 12a-c with the C=C bond in the carbocyclic ring (exocyclic on the dioxanone ring) are most readily isolated (70-80% from the saturated precursors). Michael addition of Cu(I)-containing reagents to 12a-c and subsequent alkylations afford dioxanones 14a-i and 16a-d with trans-fused cyclohoxane ring (Scheme 4). All enolate alkylations are carried out in the presence of the cyclic urea DMPU as a cosolvent. The configuration of the products is established by NMR measurements and chemical correlation. Some of the products are converted to single isomers of monocyclic hydroxycyclopentane (17-19) and cyclohexane derivatives (20-23; Scheme 5). Possible uses of the described reactions for EPC synthesis are outlined. The observed steric course of the reactions is discussed and compared with that of analogous transformations of monocyclic and acyclic derivatives.
    Additional Material: 3 Tab.
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  • 122
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Wharton rearrangement of 2,3-epoxytricyclo[7.1.1.02,7]undecan-3-one, a sterically hindered system, which should have led to an allyl alcohol with the OH group at a bridgehead, gave instead the allylically rearranged alcohol. The desired hydroxy compound was prepared by the Barton modification of the Wharton rearrangement: borohydride reduction to the epoxy alcohols, reaction with N, N′-thiocarbonylbisimidazole, and treatment with Bu3SnH. The bridgehead alcohol (and other 2-oxygenated tricyclo[7.1.1.02,7]undecanes) readily rearranged under acidic or thermal conditions.
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  • 123
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of 7-deaza-N6-methyladenine N9-(2′-deoxy-β-D-ribofuranoside) (2) as well as of 8-aza-7-deaza-N6-methyladenine N8- and N9-(2′-deoxyribofuranosides) (3 and 4, resp.) are described. A 4,4′-dimeth-oxylritylation followed by phosphitylation yielded the methyl phosphoramidites 12-14. They were employed together with the phosphoramidite of 2′-deoxy-N6v-methyladenosine (15) in automated solid-phase oligonucleotide synthesis. Alternating or palindromic oligonucleotides derived from d(A-T)6 or d(A-T-G-C-A-G-A*-T-C-T-G-C-A) but containing one methylated pyrrolo[2,3-d]pyrimidine or pyrazolo[3,4-d]pyrimidine moiety in place of a N6-methylaminopurine (A*) were synthesized. Melting experiments showed that duplex destabilization induced by a N6-Me group of 2′-deoxy-N6-methyladenosine is reversed by incorporation of 8-aza-7-deaza-2′-deoxy-N6-meihyladenosine, whereas 7-deaza-2′-deoxy-N6-methyladenostne decreased the Tm value further. Regiospecific phosphodiester hydrolysis of d(A-T-G-C-A-G-m6A-T-C-T-G1-C-A) by the endodeoxyribonuclease Dpn I, yielding d(A-T-G-C-A-G-m6A) and d(pT-C-T-G-C-A), was prevented when the residue c7m6Ad (2), c7m6z8Ad (3), or c7m6z8Ad′ (4) replaced m6Ad (1) indicating that N(7) of N6-methyladenine is a proton-acceptor site for the endodeoxyribonuclease.
    Additional Material: 4 Ill.
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  • 124
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethyl and tert-butyl azidoformate added to 7-oxabicyclo[2.2.1]hept-5-en-2-one dimethyl (5) and dibenzyl (6) acetals to give mixtures of regioisomeric triazolines. The latter gave the corresponding aziridines (6,6-dialkoxy-3-aza-8-oxatricyclo[3.2.1.02,4]octane-3-carboxylates 15, 19, 23, and 27 and 31) on UV irradiation. In the presence of protic acids, the aziridines were rearranged into protected amines ([3-endo-alkoxy-5-oxo-7-oxabicyclo[2.2.1]hept-2-exo-yl]carbamates 16, 20, 24, and 28 and 33). Using (+)-(1R, 4R)-5,5-bis(benzyloxy)7-oxabicyclo[2.2.1]hept-2-ene((+)-6) derived from furan and l-cyanovinyl (1S)-camphanate, the method was applied to prepare 2-O-benzyl-3-[(tert-butoxy)carbonyiamino]-5-O-(3-chlorobenzoyl)-3-deoxy-β-D-altrofuranurono-6,1-lactone ((-)-37). This compound was converted to methyl 3-amino-3-deoxy-α-D-altropyranoside hydrochloride (44) and several derivatives.
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  • 125
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A regioselective cyclohexannulation procedure, whose key step involves the [4 + 2] cycloaddition of dienamines 12-24 with methyl acrylate, allows the conversion of cycloalkanones 1-11 to bicyclic dienoates 25 - 37. The chemistry of 26 is briefly examined and, in the context of organoleptic studies concerning functionalised 5,5,9-tri-methyldecalins, the transformation of 37 to ketones 44 and 46 as well as to acetates 53-56 is described.
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  • 126
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 929-932 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eight new acetylenic compounds have been isolated and identified from the culture medium of the fungus Eutypa lata. Structural elucidation and biological activity are discussed.
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  • 127
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various Adducts from Ketones, Diazocyanides, and Nitrosobenzene with (Methylidenamino)phosphines(Methylidenamino)phosphine 1a reacts with activated ketones to 2,7-dioxa-5-aza-1λ5-phosphabicyclo-[3.2.0]heptanes 2a, b and with nitrosobenzene to l, 3,5,2λ5-oxadiazaphosphole 3a. The reaction of 1b with nitrosobenzene and diethyl mesoxalate yields 2,7-dioxa-3,5-diaza-1λ5-phosphabicyclo[3.2.0]heptane 4. With the cyano group of diazocyanides, 1a reacts to the adducts 5a-d. The structure of 5a is proven by an X-ray diffraction analysis.
    Additional Material: 1 Ill.
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  • 128
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 975-979 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photolysis (λ = 254 nm) of 4-(t-Bu)-substituted [b]-fused bi- and tricyclic pyrandiones 5 affords title compounds 4 in good yields as well as small amounts of spiroalkanediones 8. The alkyl-substitution pattern at C(4) of the pyran ring in 5 determines the relative amount of α vs. β-cleavage products obtained from the primarily formed acyl-vinyloxy biradical.
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  • 129
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 72 (1989), S. 980-984 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α-Silylated ketones (S)-2 (ee ≥ 98%), easily available through silylation or silylation/alkylation from ketones 1 using the (-)-(S)-1-amino-2-(methoxymethyl)pyrrolidine (SAMP)-/(+)-(R)-1-amino-2-(methoxymethyl)pyrrolidine (RAMP)-hydrazone method, are oxidized to give α-hydroxy-ketones (R)-5 of high enantiomeric purity (ee ≥ 98%) and in good overall yields (51-70%). The key step of the procedure is the silicon-directed diastereoselective oxidation of the corresponding silyl enol ethers of (S)-2, with m-chloroperbenzoic acid or 3-phenyl-2-(phenylsulfonyl)oxaziridine, followed by flash chromatography and desilylation.
    Additional Material: 1 Tab.
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  • 130
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    Helvetica Chimica Acta 72 (1989), S. 993-995 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crystalline salts of the hydrolytic dimer of Cr(III), [Cr2(μ-OH)2(H2O)8]X4·n H2O (X = p-toluenesulfonate (tos) or mesitylene-2-sulfonate (dmtos)) have been prepared in good yields via a simple two-step procedure: H+ oxidation of Cr metal to give Cr2+ (T ≍ 70°) followed by O2 oxidation, of Cr2+ to give the dimer (T ≍ 25°). The mechanism of conversion of Cr2+ into the dimer is discussed.
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  • 131
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    Helvetica Chimica Acta 72 (1989), S. 985-992 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Note on Ellagitannins and Flavonol Glycosides from Rose PetalsPetals from two garden roses proved to be very rich in ellagitannins and flavonol glycosides. Rutin (1), spiraeoside (2), quercitrin (3), isoquercitrin (4), nicotiflorin (5), eugeniin (6), rugosin A (7), rugosin D (10), casuarictin (8), and tellimagrandin I (9) were isolated. Spiraeoside, at physiological pH, exerts a pronounced stabilisation of the anthocyanin colour with enhancement of extinction and bathochromic shift of the absorption maximum in the visible range. The abundance of gallic-acid derivatives 6-10 is in contrast to the apparent inability of rose flowers to produce anthocyanins with a trihydroxylated ring B, a prerequisite in breeding true blue-coloured roses.
    Additional Material: 2 Ill.
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  • 132
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    Helvetica Chimica Acta 72 (1989), S. 996-1000 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (±)-Ambrox (10), the racemic form of (-)-Ambrox®, the commercially most important ambergris odorant has been synthesized from a readily available bicyclic keto ester in five steps. The racemic ether retains the characteristic scent of fine-quality ambergis, and the odor threshold of the racemate and the (-)-enantiomer prepared from natural sclareol were found to be essentially identical.
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  • 133
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    Helvetica Chimica Acta 72 (1989), S. 1001-1007 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three novel prenylated xanthones, 1-3, have been isolated from the root bark of Garcinia gerrardii HARVEY ex T. R. SIM (G. natalensis SCHLECHTER; G. transvaalensis BURTT DAVY; Guttiferae). Structure elucidation was achieved by a combination of one- and two-dimensional NMR spectroscopic techniques, including long-range HETCOR, mass spectroscopy, and chemical methods. Garcigerrin A (1) and B (2) are pyrano derivatives of 3. They all show a rare 1,4,5 oxygenation pattern of the xanthone nucleus. Xanthone 3 is fungicidal against Cladosporium cucumerinum.
    Additional Material: 1 Ill.
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  • 134
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    Helvetica Chimica Acta 72 (1989), S. 1052-1060 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduction of the carbonyl group in the side chain of 4-(1-nitro-2-oxocyclododecyl)butan-2-one (3) with organoboron complexes are influenced by the chiral center, in 4-position with respect to the carbonyl C-atom, to which the NO2 group is attached, a rare type for an asymmetric reduction. Independent of the (R)- or (S)-configuration of the Alpine-Hydride, (+)-3 is reduced only to the (15S)-nitrolactone (+)-5 and, after subsequent transformations, to (+)-(-S)-15-hexadecanolide ((+)-1), enantiomer of the naturally occurring (-)-1.
    Additional Material: 1 Ill.
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  • 135
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    Helvetica Chimica Acta 72 (1989), S. 1061-1065 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Methyl VirensateThe synthesis of methyl virensate (=methyl 4-formyl-3,8-dihydroxy-1,6,9-trimethyl-11-oxo-11H-dibenzo-[b, e][1,4]dioxepin-7-carboxylate; 18) by the condensation of the substituted β-orcinol and orcinol units 9 and 10 followed by formylation and demethylation of the depsidone 13 is described.
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  • 136
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    Helvetica Chimica Acta 72 (1989), S. 1066-1077 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of nine macrocyclic polyamines 2-10 containing pyridine units is described. These compounds are 22- (9), 24- (2-4,6,8,10), or 26- (5, 7) membered hexaaza (2,3,9,10) or octaaza (4-7) macrocycles in which one to four pyridine units are incorporated. Compounds 3,4,9, and 10 are homoditopic ligands, whereas 2 and 5 are heteroditopic and 6-8 multitopic receptors. Compounds 2-10 are potential ligands for metal cations as well as, in their protonated forms, for anions. Protonated macrocycles 2-10 are also potential catalysts for the hydrolysis of nucleotides and polyphosphates.
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  • 137
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N-(cyclobutylmethyl)morphinans 12, 19, 20, 21, 27, and 29 and the N-(2-cyanoethyl) analogue 33 were prepared from different precursors. Pharmacological evaluation (e.g. opioid receptor binding assays, acetic-acid writhing test, hot-plate assay) points to a partial opioid agonism of compounds 12, 27, 29, and 33, and to full opioid agonism of compounds 19-21.
    Additional Material: 3 Tab.
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  • 138
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiospecific Synthesis of (+)-(R)-6-Ethyl-2,3-dihydro-2-methyl-4H-pyran-4-one, Sex-pheromonal Component of the Male Swift Moth Hepialus hecta L.A new synthesis of (+)-(R)-6-ethyl-2,3-dihydro-2-methyl-4H-pyran-4-one ((R)-8), sex-pheromonal component of the male swift moth Hepialus hecta L., has been performed from (-)-(R)-1-(1,3-dithian-2-yl)propan-2-ol with an enantiomeric excess of ≥ 97%.
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  • 139
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    Helvetica Chimica Acta 72 (1989), S. 1262-1267 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel allenic epoxycyclohexanes 1, and related compounds 2 and 3 have been isolated from the culture medium of Eutypa lata. Their structures were established by combination of spectroscopic and chemical techniques. Biogenetic origin and biological activity of these compounds are also discussed.
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  • 140
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By mixing acidic solutions of 1,4,8,11-tetraazacyclotetradecane (Cy) with CuX2 (X = Cl-, Br-), either the hexahalocuprates of the tetraprotonated form of the macrocycle ([CyH4] [CuX6]) or the tetrahalocuprates of its Cu2+ complex ([CuCy] [CuX4]) are obtained. The structures of the chloro derivatives are established by X-ray diffraction analysis. In [CyH4] [CuCl6], the Cu2+ is in a tetragonally distorted octahedral geometry with four short and two long Cu—Cl bonds. The tetraprotonated macrocycle is centrosymmetric, and its conformation is exodentate, so that the four ammonium groups are as far as possible from each other to minimize the electrostatic repulsion. In [CuCy] [CuCl4], the Cu2+ ion complexed by the macrocycle is surrounded by four N-atoms in a square-planar arrangement. In addition, the axial positions are occupied by two Cl- ions of two CuCl42- units, which act as bridges. The macrocycle is in the trans-III-configuration. The other Cu2+ ion is coordinated by four Cl- ions in a distorted tetrahedral geometry. IR and VIS spectra of the chloro and bromo derivatives are used to discuss the structure of the bromo species.
    Additional Material: 3 Ill.
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  • 141
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of tri-N-acetylated heparin pentasaccharide 2 is described. It was assembled from five suitably blocked monosaccharide units (3-7). Glucuronic-acid building block 4 was prepared from glucose by direct Jones oxidation of the 6-O-trityl derivative 18. The resulting acid 16 was esterified to 17 in large mounts using methyl chloroformate/base. Trimethylsilyl bromide proved to be an excellent reagent for the hydrolysis of a prop-1-enyl glycoside (19 →21). The pentasaccharide 29 was obtained by a [2 + 2] + 1 synthesis, the glycosylation reactions furnished good to very good yields. The identity of protected oligosaccharides was confirmed by 1H-NMR spectroscopy. Sequential deblocking of the pentasaccharide, O-sulfation, and N-acetylation gave 2 which was shown to exhibit ca. 600 times lower anticoagulant activity than pentasaccharide 1.
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  • 142
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    Helvetica Chimica Acta 72 (1989), S. 1278-1283 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eight bicyclic ether derivatives 11-18, related to the tricyclic odorant Ambrox® (1) and its analogues 2-6 by formal heteroring-opening, have been prepared; their odoriferous activity/in activity is correlated with the steric accessibility of the ether O-atom, calculated by computer-aided molecular modeling.
    Additional Material: 2 Tab.
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  • 143
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiospecific Synthesis of (-)-(1R, 3R, 5S)-1,3-Dimethyl-2,9-dioxabicyclo[3.3.1]nonaneThe isomer (-)-(1R, 3R, 5S)-endo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane ((1R, 3R, 5S)-8) has been synthesized from (-)-(3R)-methyl 3-hydroxybutanoate. The key intermediate (3R, 5R)-5 is proved to be a useful synthon for EPC syntheses.
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  • 144
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The separation of the enantiomers of the olefinic hydrocarbons multifidene 3 and aucantene 5 from the pheromone blend of the two seaweeds Cutleria multifida and Chorda tomentosa is achieved by gas chromatography on modified cyclodextrins as chiral stationary phases. The method is also applicable for the separation of enantiomeric alkyl-, alkenyl- or alkynyl-substituted cyclooctadienes and cyclopentenes. A plausible rational is presented for the biosynthesis of racemic by-products of algal pheromone blends.
    Additional Material: 2 Ill.
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  • 145
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    Helvetica Chimica Acta 72 (1989), S. 1311-1318 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Substituted 1,6-Methano[10]annulenes by Cycloadditions of 1H-CyclopropabenzeneDiels-Alder reactions of 1H-cyclopropabenzene (1) with electron-poor dienes, leading to substituted 1,6-methano[10]annulenes, are described.
    Additional Material: 3 Tab.
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  • 146
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of optically active 1-amino-2-(hydroxymethyl)cyclopropanecarboxylic acid has been achieved by a route involving cycloalkylation of dimethyl malonate with epichlorohydrin and subsequent Hofmann rearrangement. The reaction of epichlorohydrin with nucleophiles may occur al either electrophilic site, epoxide or halide. Based on the absolute configuration of the starting materials and the lactones obtained, it has been shown that the initial step of the cycloalkylation occurs at the epoxide moiety. The 1-amino-2-(hydroxymethyl)-cyclopropanecarboxylic acid, an analogue of the precursor to the plant growth hormone ethylene, is to be used in affinity purification techniques and in generation of antibodies.
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  • 147
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray crystal structures of 2,11-bis(di-R-phosphinomethyl)benzo[c]phenanthrenes (R = Ph, t-Bu) are reported. Both ligands have the same conformation and the substitution of a Ph by a t-Bu group does not cause significant changes in the tetracyclic aromatic unit which shows the same distortions as the parent hydrocarbon. The conformations and structural features of the two ligands and 18 complexes containing these ligands as well as of one compound with a ligand with Et substituents are compared. It is pointed out that (1) the conformations of the free ligands differ significantly from those of their complexes, (2) in all the complexes characterized to date, these ligands act as chelating agents, and (3) the ligands adopt two different conformations in the complexes, one of them appearing to be more flexible than the other.
    Additional Material: 4 Ill.
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  • 148
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    Helvetica Chimica Acta 72 (1989), S. 1319-1323 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-phase syntheses of enkephalin and somatostatin analogues with C-terminal OH functions instead of the normal carboxylates are described. The OH function of the N-terminal amino alcohol was acylated with succinic acid and esterified to the solid support. Normal Boc-TFA solid-phase strategy can be applied to build up and cleave these peptides. The succinic ‘handle’ can be removed by mild basic hydrolysis after cleavage.
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  • 149
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    Helvetica Chimica Acta 72 (1989), S. 1324-1336 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solid-State Polymerisation of a ‘Push-Pull’-DiacetyleneSolid-state polymerisation of ‘push-pull’-diacetylene 5-(diphenylamino)-1-phenylpenta-2,4-diyn-1-one (1d), initiated by heating of crystals of 1d at 90°, gives ‘push-pull’ poly-diacetylene 2d. X-Ray results and spectroscopic data of monomer 1d as well as of polymer 2d are discussed.
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  • 150
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Successive treatment of conjugated N-enoylsultams 2 with alkyl Grignard reagents/CuCl and aq. NH4Cl solution generated selectively two stereogenic centers at C(α) and C(β) providing, after flash chromatography and crystallization, acylsultams 5 in high purity. Mild cleavage afforded the recovered sultam auxiliary 1 and enantiomerically pure carboxylic acids 7.
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  • 151
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical synthesis of adenylyl-(2′-5′)-adenylyl-(2′-5′)-8-azidoadenosine (15) was performed by the phosphotriester approach. Enzymatic phosphorylation of 15 by [γ-32P]ATP led to the corresponding labelled 5′-monophosphate 16. Photoinsertion of 16 took place on UV irradiation by covalent cross linking to a protein of Mr 80 K known to be RNase L. Radiobinding and core-cellulose assays as well as photoaffinity labelling experiments with 16 are described.
    Additional Material: 2 Ill.
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  • 152
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    Helvetica Chimica Acta 72 (1989), S. 1346-1353 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mixture of isomeric dimethyl-endo-tricyclo[5.2.1.02,6]deca-3,8-dienes (A) resulting from Diels-Alder reactions of 1-, 2-, and 5-methylcyclopenta-1,3-dienes (i-iii, respectively) at 20° was shown by GLC analysis to consist of at least 10 components (Table 1). The structures of the six major isomers 1-6, representing 96% of the total mixture, were established by 1H- and 13C-NMR spectroscopy. Whereas on heating up to 110° the proportions of 1, 2, 4, and 6 remain nearly unaffected (±2 %), the dimers 3 and 5, formed in 22 % and 24 % yield, respectively, at 20°, isomerise above 70° reversibly via [3,3]-sigmatropic rearrangement and equilibrate at 110° to a ca. 10:1 ratio.
    Additional Material: 3 Tab.
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  • 153
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    Helvetica Chimica Acta 72 (1989), S. 1362-1370 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The racemic cis- and trans-5-butyltetrahydro-4-methylfuran-2-ones ( = whisky lactones) and their higher homologues tetrahydro-4-methyl-5-pentylfuran-2-ones ( = cognac lactones) have been prepared in 2-3 steps from 2-(trimethylsiloxy)furan. Regioselective alkylation of the latter afforded the 5-butyl- and 5-pentylfuran-2(5H)-ones which served as precursors for the stereocontrolled construction of either diastereoisomer of the beverage lactones. The structure and tautomerization of the diazomethane adducts of these 5-alkylfuran-2(5H)-ones are also described.
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  • 154
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    Helvetica Chimica Acta 72 (1989), S. 1416-1427 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Derivatives of isothiazol-3(2H)-one 1,1-dioxide react regiospecifically with 1,3-dipolar agents. The main regiocontrolling factor is ascertained to be the C=O group of the dipolarophile. The topology of the adducts is also in general agreement with predictions based on perturbation theory. Several adducts can be aromatized to heterocyclic equivalents of saccharin, and may then be elaborated into structural analogs of tenoxicam (Tilcotil® and piroxicam (Feldene®)).
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  • 155
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    Helvetica Chimica Acta 72 (1989), S. 1435-1437 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 156
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    Helvetica Chimica Acta 72 (1989) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 157
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound 8 was prepared in three steps starting from the optically pure aldehyde (2R, 4E)-2-methyl-hex-4-enal (3), thus constituting the shortest synthetic approach reported. Two of the three stereogenic centers in the product were generated in a coupling reaction of 3 with ethyl isocyanoacetate, catalyzed by a gold(I)/chiral ferrocenylphosphine system, giving the dihydrooxazole 5 in 85% diastereoselectivity (mismatchedcase). The weak effect of double stereodifferentiation in this reaction (matched case 90% ds) is discussed. N-Methylation and hydrolytic ring opening of 5 gave the protected form 7 of MeBmt, The X-ray diffraction study carried out on 7 confirms the absolute configuration of the two stereogenic centers formed in the gold(I)-catalytic reaction.
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  • 158
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    Helvetica Chimica Acta 72 (1989), S. 1495-1500 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general and rapid procedure is developed for the preparation of secoribo-nucleoside analogues. Bu4NF has a marked effect on the condensation of guanine (5) with 2-(chloromethoxy)ethyl benzoate (2) or 1-halo-2-(chloromethoxy)ethanes 12 and 16. Condensation and deprotection of the acyl protecting group and nucleophilic displacement of the halogen atoms to yield 9-[(2-hydroxyethoxy)methyl] guanine (9) occurred in one step.
    Additional Material: 1 Tab.
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  • 159
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction between the buffer 2-amino-2-(hydroxymethyl)propane-1,3-diol (Tris) and the Eu(III) ion has been studied by luminescence spectroscopy in D2O. Emission and excitation spectra (5D0←7F0 transition) indicate an interaction with both [TrisH]+ and neutral Tris species. The former is weak and probably of the outer-sphere type. The latter is of inner-sphere type and corresponds to the formation of the [Eu(Tris)]3+ species (estimated logK1 = 2.3 ± 0.3). Buffer Tris is also demonstrated to prevent the formation of an Eu-hydroxo species in the pD range of 7-8. Potentiometric measurements in H2O allowed a more precise calculation of the stability constant: logK1 = 2.44 ± 0.07. Comparison with the data for aliphatic amines and other metal ions lead to the conclusion that the Eu/Tris interaction is mainly achieved through the amino group. 1H-NMR spectra in presence of Tb(III) ions confirmed both this assumption and the presence of a weak interaction with TrisH+. Quantitative determinations of association constants between lanthanide ions and macromolecules of biological interest performed in presence of Tris should, therefore, be corrected for the Eu/Tris interaction.
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  • 160
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 3:1 mixture of (+)-(2S, 6S)-trans-α-irone ((+)-1) and (-)-(2S, 6S)-trans-γ-irone (-)-2) has been synthesized with ca. 70% e. e. by the ene reaction of (-)-(S)-3 and but-3-yn-2-one.
    Additional Material: 1 Tab.
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  • 161
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 8-aza-2′-deoxyadenosine ( = 7-amino-3H-1,2,3 triazolo[4,5-d]pyrimidine N3-(2′-deoxy-β-D-ribofuranoside); 1) as well as the N2- and N1-(2′-deoxy-β-D-ribofuranosides) 2 and 3 is described. Glycosylation of the anion of 7-amino-3H-1,2,3-triazolo[4,5-d]pyrimidine (6) in DMF yielded three regioisomeric protected 2′-deoxy-β-D-ribofuranosides, i.e. the N3-, N2-, and N4-glycosylated isomers 7 (14%), 9 (11%), and 11 (3%), respectively, together with nearly equal amounts of their α-D-anomers 8 (13%), 10 (12%), and 12 (4%; Scheme 1). The reaction became Stereoselective for the β-D-nucleosides if the anion of 7-methoxy-3H-1,2,3-triazolo[4,5-d]pyrimidine (13) was glycosylated in MeCN: only the N3-, N2, and N1-(2′-deoxy-β-D-nucleosides) 14 (29%), 15 (32%), and 16 (23%), respectively, were formed (Scheme 2). NH3 Treatment of the methoxynucleosides 14-16 afforded the aminonucleosides 1-3. The anomeric configuration as well as the position of glycosylation were determined by combination of 13C-NMR, 1H-NMR, and 1D-NOE difference spectroscopy. Compound 1 proved to be a substrate for adenosine deaminase, whereas the regioisomers 2 and 3 were not deaminated.
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  • 162
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    Helvetica Chimica Acta 72 (1989), S. 1597-1607 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure Determination of N6-, 9-and 7-Acyladenines by 1H- and 13C-NMR Spectroscopy of Solids and in Solution.Adenine (1) reacts with carboxylic acid anhydrides or chlorides 2 to yield the acyladenine isomers 3-5. The isomeric structures were determined by 33C- and 1H-NMR spectroscopy in solution and by solid-state 13C-NMR spectroscopy.
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  • 163
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    Helvetica Chimica Acta 72 (1989), S. 1608-1617 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H-Cyclopropa[b]naphthalene 3c and the 2,7-diphenyl-substituted derivative 3a have been synthesized via cycloaddition of the appropriate isobenzofurans 1a and 1b to 1-bromo-2-chlorocyclopropene and aromatization of the adducts with low-valent Ti. The same procedure afforded the 2,7-dimethyl-H-cyelopropa[g]isoquinoline (15), but failed for the parent azacompound. Reaction of adducts of furans to 1-bromo-2-chlorocyclopropenes with low-valent Ti produced mixtures of cyclopropabenzenes 19 and 1,6-dihalogeno-1,3,5-cycloheptatrienes 18. The latter could be converted to cyclopropabenzenes with BuLi.
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  • 164
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mediterranean alcyonacean Alcyonium (= Parerytkropodium) coralhides (PALLAS, 1766) is shown to contain three novel diterpenes which are of biogenetic significance: the 3,7-cyclized cembranoid Coralloidolide C ( = (+)-(6R*, 7R*, 11S*, 12aS* 3aE)-7,8-epoxy-3,5,6,7,8,9,10,11,12,12a-decahydro-12a-hydroxy-11-isopropenyl-1,4-dimethyl-3-oxocyciopentacydoundecene-8,6-carbolactone; (-)-3), the O-bridged diketonic cembranolide Coralloidolide D (= (+)-(1R*, 2S*, 3R*, 5R*, 12S*, 8Z)-2,5-epoxy-1-hydroxy-12-isopropenyl-5,9-dimethyl-7,10-dioxocyclotetradeca-8-ene-1,3-carbolactone; (+)-4), and the diketonic epoxycembranolide coralloidolide E (=(+)-(1R*, 2R*, 3R*, 12S*, 5Z, 8Z)-1,2-epoxy-12-isopropenyl-5,9-dimethyl-7,10-dioxocyclotetra-deca-5,8-diene-1,3-carbolactone; (+)-5), The latter in pyridine at r. t. undergoes a double bond shift from C(4) = C(5) to C(4) = C(18) to give the isomer (-)-7. Structural assignments are mainly based on ID and 2D NMR and MS spectral data. Either corailoidolide A ((-)-1) or the hypothetic unsaturated 1,4-diketone 9 can be envisaged as the precursors of all coralloidolides.
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  • 165
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    Helvetica Chimica Acta 72 (1989), S. 1627-1638 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H-Cyclopropa[a]naphthalene (1a) is accessible via reduction of the dichloro compound 1c with LiAlH4/AlCl3. Several derivatives of tetrahydrocyclopropa[a]naphthalene were synthesized. However, contrary to their 1,1-dihalogeno analogues, they afforded no cycloproparenes upon attempted aromatization.
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  • 166
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    Helvetica Chimica Acta 72 (1989), S. 1618-1626 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 1H-cyclopropa [b]naphthalene (1a) or 1H-cyclopropa[b]anthracene (10a) with tris(acetonitrile)tricarbonylchromium affords cyclobutanaphthalenone and cyclobutaanthracenone 2 and 11, respectively. In contrast, the bis-silylated Cycloproparenes 1b and 10b undergo complexation at the terminal benzene ring and lead to the arene-tricarbonylchromium complexes 4b and 12, respectively. Desifylation of 4b to 4a is effected by t-BuOK.
    Additional Material: 2 Ill.
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  • 167
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituent Effects on NMR Spectra of Pentafulvenes. 13C, 13C-NMR Coupling Constants (1J(C, C))1H- and 13C-NMR spectra of 6-monosubstituted pentafulvenes 1-8 have been analysed, and 1J(C, C) coupling constants have been determined from ID-inadequate spectra of 13C satellites. It turns out that 13C,13C coupling constants of the ring C-atoms, and especially J(1,2)/J(3,4) and J(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron-donating capacity of the substituent R, J(1,2)/J(3,4) values are decreasing, while J(2,3) (and J(1,5)/J(4,5) as well) are increasing, and linear correlations of Hammett substituent constants σ+ and 1J(C,C) values are obtained.
    Additional Material: 2 Ill.
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  • 168
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    Helvetica Chimica Acta 72 (1989), S. 1718-1721 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new synthetic approach towards the indole ring system is described. When dimethyl 1-methyl-2-oxa-1-aza-spiro[4.5]dec-3-ene-3,4-dicarboxylate (6) was refluxed in toluene, the previously known dimethyl 4,5,6,7-tetra-hydro-1-methyl-1H-indole-2,3-dicarboxylate (7) was obtained in 71% yield, via a 2,3-dihydroisoxazole-pyrrole rearrangement. After treatment with DDQ, the tetrahydro analogue 7 was converted to the corresponding dimethyl 1-methyl-1H-indole-2,3-dicarboxylate (8).
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  • 169
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cytotoxically and antivirally active compounds bvUd (1), flUd (4), acyclovir (7), and Aa (12) have chemically been combined with the appropriately protected (2′-5′)diadenylate 20 by the phosphotriester approach to give the 2′-5′ oligonucleotide trimers 21-24. The deprotection of the various blocking groups by chemical means afforded the 2′-5′ trimers 25-28, which can be regarded as new type of a potential prodrug form delivering nucleotides to the targets inside cells. In an analogous series of reactions, 9-(3′-azido-3′-deoxy-β-D-xylofuranosyl)adenine was coupled with 7 to the 2′-5′ trimer 31. The antiviral screening of the oligonucleotides 25-27 and 31 showed biological activities closely related to the parent nucleosides, possibly indicating their release by enzymatic cleavage of the oligomers.
    Additional Material: 1 Tab.
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  • 170
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    Helvetica Chimica Acta 72 (1989), S. 1749-1752 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic monomorine (12) is prepared in six steps in 26% overall yield from 2-butyl-1H-pyrrole and ethyl (E)-but-2-enoate by exploiting the rhodium(II)-acetate-catalyzed decomposition of (4RS)-4-(2′-butyl-1′ H-pyrrol-1′-yl)-1-diazopentan-2-one (7).
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  • 171
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    Helvetica Chimica Acta 72 (1989), S. 1722-1728 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from dibenzo[a, c]cyclooctene (4) and 4-methyl-3H-1,2,4-triazol-3,5(4H)-dione (MTAD), the strained skeleton of the title azo compound 1 is assembled in a tandem photo-Diels-Alder addition/di-π-methane rearrangement sequence. The synthesis is completed by a stepwise hydrolytic oxidation of the ensuing triazolidine-dione 2 with nickel peroxide. Thermolysis of 1 in benzene solution is shown to be governed by an initial 1,3-dipolar cycloreversion which leads, via an intermediate diazo compound 11, to cyclobuta[1]phenanthrene 8 and two further carbene-derived C16H12 products. Photolysis of 1 at 350 nm leads in modest yield (12%), via a diazenyl diradical, to an unstable bridged bicyclobutane 10 (dibenzooctavalene). MNDO calculations suggest the latter to have a rapidly inverting, twisted structure of C2 symmetry.
    Additional Material: 1 Ill.
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  • 172
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    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new allose-containing iridoid diglycoside, allobetonicoside (1), and a new acyl iridoid glucoside, 6-O-acetylmioporoside (2) have been isolated from the aerial parts of Betonica officinalis L. in addition to two known iridoid glucosides, acetylharpagide (3) and reptoside (4). Their structures have been determined by spectroscopic methods as well as by means of chemical evidence.
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  • 173
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both enantiomers of the novel α-hydroxy-γ -lactone (±)-3 (4,5-dihydro-3-hydroxy-4,4,5,5-tetramethyl-3-phenylfuran-2(3H)-one) have been synthesized via hydrolysis of the oxetanes 2 derived from the photochemical [2 + 2] cycloaddition of the ketones 1 and 2,3-dimethylbut-2-ene (Paterno-Büchi reaction) involving conventional separation of diastereoisomers (Schemes 2 and 3). The absolute configuration of (R)- and (S)-3 and of the corresponding oxetane precursors could be assigned on the basis of an X-ray structural analysis of the (-)-(1S, 4R)-camphanoyl derivative (3′S)-5 of (S)-3. O-Acylation of (S)-and (±)-3 to yield a variety of derivatives ((3′S)- and (3′RS)-5, (S)- and (±)-7, (±)-8, (±)-9) was accomplished by deprotonation with BuLi at room temperature and subsequent quenching of the Li alcoholate with acyl chlorides or acid anhydrides, demonstrating the extraordinary chemical stability of 3. Additionally, the course of the temperature-dependent diastereoselective Paterno-Büchi reaction of 2,3-dimethylbut-2-ene to the benzoylformate (S)-7 ( = (S)-1d; obtained from (S)-3) was shown to proceed with 58% de at 60°, leading to a decrease of enantiomeric purity in the hydrolysis product 3.
    Additional Material: 2 Ill.
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  • 174
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    Helvetica Chimica Acta 72 (1989), S. 1809-1816 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tordanone, a Twice Bent Steroid Structure with Ring A/B β-cis(5β)- and Ring B/C α-cis(8α)-FusedThe 3β, 14α, 25-trihydroxy-5β, 8α-cholestan-6-one ( = tordanone; 4) has been prepared by stereospecific hydrogenation of 3β, 14α, 25-trihydroxy-5β-cholesta-7,22ξ-dien-6-one (5). This is the first stereospecific synthesis of a B/C cis-fused steroid belonging to the 5β, 8α -cholestane group with a H-atom at positions 5β (A/B cis-fused) and 8α. The resulting twice bent structure shows a particularly strong steric hindrance of the β-face where CH3(18) at the C/D ring junction and Hβ—C(7) of the B ring are very close to each other. Structural features and mechanistic aspects of the hydrogenation are discussed.
    Additional Material: 2 Ill.
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  • 175
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of (+)-Aspicilin Using Building Blocks from Renewable ResourcesThe 18-membered lichen macrolide (+)-aspicilin (1) is easily built up from compounds 14, 16, 3, and 24 following the C3 + C7 + C6 + C2 = C18 pattern (see Schemes). The synthesis requires 15 steps and gives 1 in 13% overall yield from D-mannose (2). The latter compound provides the stereogenic centers C(4), C(5), and C(6). The stereogenic center C(17) is supplied by building block 14 (from (-)-(S)-ethyl lactate).
    Additional Material: 3 Ill.
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  • 176
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    Helvetica Chimica Acta 72 (1989), S. 1801-1808 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of formation and dissociation of [V(H2O)5NCS]2+ have been studied, as a function of excess metal-ion concentration, temperature, and pressure, by the stopped-flow technique. The thermodynamic stability of the complex was also determined spectrophotometrically. The kinetic and equilibrium data were submitted to a combined analysis. The rate constants and activation parameters for the formation (f) and dissociation (r) of the complex are: kf298/M-1 · S-1 = 126.4, kr298/s-1 = 0.82; ΔHf≠ /kJ · mol-1 = 49.1, ΔHr≠/kJ · mol-1 = 60.6; ΔSf≠/ J·K-1·mol-1= -39.8, ΔSr≠J·K-1·mol-1 = -43.4; ΔVf≠/cm3·mol-1 = -9.4, and ΔVr≠/cm3 · mol-1 =-17.9. The equilibrium constant for the formation of the monoisothiocynato complex is K298/M-1 = 152.9, and the enthalpy and entropy of reaction are ΔH0/kJ · mol-1 = - 11.4 and ΔS0/J. K-1mol-1 = +3.6. The reaction volume is ΔV0/cm3· mol-1 = +8.5. The activation parameters for the complex-formation step are similar to those for the water exchange on [V(H2O)6]3+ obtained previously by NMR techniques. The activation volumes for the two processes are consistent with an associative interchange, Ia, mechanism.
    Additional Material: 4 Ill.
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  • 177
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 19-24 
    ISSN: 0009-2940
    Keywords: Bis(diorganoboryl)chalcogenides ; Pyrazaboles ; Pyrazoles ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Neuartige Substituierte B2ElVIN2 HeterocyclenDie Bis(diorganoboryl)chalkogenide (R2B)2O [R = C2H5 (3); R2 = 1,5-C8H14 (1)], (R2B)2S [R2 = 1,5-C8H14 (5)], und (R2B)2Se [R2 = 1,5-C8H14 (7)] reagieren mit Pyrazol (Pz) und dessen Derivaten 3-Methylpyrazol (3-MePz) und Indazol (benzo-Pz) in hohen Ausbeuten (65-92%) zu stabilen 1:1-Additionsverbindungen [z. B. 2 (El = O), 4 (El = O), 6 (El = S), 8 (El = Se)]. 1H-, 13C-, 11B-NMR-Spektren und Röntgenstrukturanalysen (von 2 und 6) zeigen eine Grundstruktur mit einem zentralen B2ElN2-Heterocyclus (El = O, S, Se). Die Reaktion von 2 mit R2BH und die Thermolyse von 4 führen zu den dimeren 1-Pyrazolylboranen 9a bzw. 9b.
    Notes: The bis(diorganoboryl) chalcogenides (R2B)2O [R = C2H5 (3); R2 = 1,5-C8H14 (1)], (R2B)2S [R2 = 1,5-C8H14 (5)], and (R2B)2Se [R2 = 1,5-C8H14 (7)] react with pyrazole (Pz) and its derivatives 3-methylpyrazole (3-MePz) and indazole (benzo-Pz) to form in high yields (65-92%) stable 1:1 adducts [e.g. 2 (El = O), 4 (El = O), 6 (El = S) and 8 (El = Se)]. 1H-, 13C-, 11B-NMR spectra and X-ray analyses (of 2 and 6) show a basic structure with a central B2ElN2 (El = O, S, Se) heterocycle. The reaction of 2 with R2BH and the thermolysis of 4 give the dimeric 1-pyrazolylboranes 9a and 9b, respectively.
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 31-36 
    ISSN: 0009-2940
    Keywords: Mercury - mercury contacts ; Naphthalenediylmercury compounds ; Organomercury compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Extremely Short Mercury-Mercury Contacts in peri-Dimercurated Naphthalene Compounds1-Naphthylmercury chloride (1) and 1,8-naphthalenediylbis(mercury chloride) (2) were prepared from the corresponding naphthyllithium precursors and HgCl2 in ca. 80% yield. In an alternative route, 2 can be obtained from 1,8-naphthalenediyldiboric acid anhydride and HgCl2 in 85% yield. The structure of 2·DMSO has been determined by X-ray diffraction methods. The lattice contains discrete adducts in which the two mercury atoms are bridged by the DMSO oxygen atom. The HgCl moieties are bent away from each other through distortions of the naphthalene framework and of the C—Hg—Cl axes, which results in a Hg ‥ Hg distance of 3.102(1) Å. - Symmetrization of 2, induced by treatment with NaI in aqueous ethanol, affords bis(μ-1,8-naphthalenediyl)dimercury (3). In the X-ray structure determination of this compound the shortest „non-bonding“ Hg·Hg contact reported in the literature has been detected: Hg1··Hg2 = 2.797(1) Å. The molecule also shows distortions in the naphthalene framework and in the C—Hg—C axes [C—Hg—C = 173.3(5)°].
    Notes: 1-Naphthylquecksilberchlorid (1) und 1,8-Naphthalindiylbis-(quecksilberchlorid) (2) werden aus den zugehörigen Naphthyllithium-Verbindungen und HgCl2 mit ca. 80% Ausbeute erhalten. Alternativ kann 2 auch aus 1,8-Naphthalindiyldiborsäureanhydrid und HgCl2 gewonnen werden (Ausbeute 85%). Von 2·DMSO wurde die Kristallstruktur bestimmt. Es liegen diskrete Addukte vor, in denen die beiden Hg-Atome durch das O-Atom des DMSO überbrückt werden. Die HgCl-Einheiten sind durch Verzerrungen im Naphthalingerüst, durch Winkelung der Achsen C—Hg—Cl und durch deren Auslenkung aus der Naphthalinebene voneinander weggebogen, so daß ein Hg·· Hg-Kontakt von 3.102(1) Å resultiert. - 2 symmetrisiert sich bei der Einwirkung von NaI in wäßrigem Ethanol unter Bildung von Bis(μ-1,8-naphthalindiyl)diquecksilber (3). Bei der Strukturanalyse dieser im Kristall zentrosymmetrischen Verbindung wurde der bisher kürzeste „nichtbindende“ Hg··Hg-Kontakt von 2.797(1) Å gefunden. Auch in 3 sind die C—Hg—C-Achsen abgewinkelt [C—Hg—C = 173.3(5)°], und das Naphthalingerüst ist verzerrt.
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  • 179
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 59-61 
    ISSN: 0009-2940
    Keywords: N-Butyl-N′-dansylthiourea ; Complexing agent, fluorescent ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Butyl-N′-dansylthiourea as Fluorescent Broad-Band Complexing AgentN-Butyl-N′-dansylthiourea (2) [dansyl = 5-(dimethylamino)-1-naphthylsulfonyl] is obtained by the reaction of dansylamide (1) with butyl isothiocyanate. The compound is a stable, fluorescent complex agent for a broad spectrum of metal ions. The UV spectra and fluorescence of the ligand and some metal complexes are discussed. The fluorescence of the dansyl group is strongly affected by metal ions.
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  • 180
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 83-94 
    ISSN: 0009-2940
    Keywords: Enaminecarbaldehydes ; Enamino ketones ; hetero Diels-Alder reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Struktur von Enaminecarbaldehyden und Enamino KetonenDie Synthese der Enamincarbaldehyde 1a-s und 17a-c sowie der Enamino-Ketone 2a-k und deren N-Acyl-Derivate 19a-k und 21-t mit Elektronenacceptor-Substituenten an C-2 bzw an der CO-Gruppe wird beschrieben. Kondensation von 2-Formyl-3-oxopropansäure-methylester (13) mit Ammoniak und den Aminen 14b-s ergab die Enamincarbaldehyde 1a bzw. 1b-s in einer Ausbeute von 72-93%. Die Enamincarbaldehyde 17 konnten durch Formylierung von 15 mit dem gemischten Ameisensäureessigsäureanhydrid erhalten werden. Die Synthese der Enamino-Ketone 2a-k erfolgte mit einer Ausbeute von 61-97% durch Kondensation von Ammoniak und Aminen mit den Enolethern 24a-f, die durch Umsetzung reaktiver Acylchloride 23 mit Ethylvinyl-ether dargestellt wurden. Die für hetero-Diels-Alder-Reaktionen benötigten N-Acyl-Derivate 19a-k und 21-t wurden durch Acylierung des Enamincarbaldehyds 1a und der Enamino-Ketone 2a-k gebildet.
    Notes: The synthesis of enaminecarbaldehydes 1a-s and 17a-c as well as enamino ketones 2a-k, and their N-acyl derivatives 19a-k and 21-t with electron accepting substituents at C-2 and at the CO group, respectively, is described. Condensation of methyl 2-formyl-3-oxopropanoate (13) with ammonia and the amines 14b-s gave the enaminecarbaldehydes 1a and 1b-s, respectively, in 72-93% yield. The enaminecarbaldehydes 17 were obtained by formylation of 15 with acetic formic anhydride. The synthesis of the enamino ketones 2a-k was accomplished in 61-97% yield by reaction of ammonia and amines with the enol ethers 24a-f, which were formed by treatment of reactive acyl chlorides 23 with ethyl vinyl ether. The enaminecarbaldehyde 1a as well as the enamino ketones 2a-k could be acylated to give 19a-k and 2l-t, respectively, which can be used in the hetero Diels-Alder reaction.
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 119-122 
    ISSN: 0009-2940
    Keywords: Bis(phosphonium) salts ; Pyridylphosphonium salts, tri-n-butyl- and triphenyl- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemistry of Triphenyl-(or Tri-n-butyl-)pyridylphosphonium salts, 2. - 2,4-Pyridinediylbis(phosphonium) Salts2,4-Pyridinediylbis(phosphonium) salts 1 react with nucleophiles to give 4-substituted products 6-8. Under radical reaction conditions the 5-position in 1a is attacked to yield 9. sodium azide transforms 1a into 8. This salt is used as starting material for 11. The removal of the phosphonium groups in 1 and in the resulting products can be carried out selectively.
    Notes: 2,4-Pyridindiylbis(phosphoniumsalze) 1 lassen sich mit nucleophilen Reaktionspartnern in die 4-substituierten Produkte 6-8 überführen. Unter radikalischen Bedingungen wird selektiv die 5-Position in 1a unter Bildung von 9 angegriffen. Nach Umsetzung mit Natriumazid entsteht zunächst das Salz 8, das als Ausgangsverbindung für 11 dient. Die Substitution der Phosphoniumgruppen aus den Edukten 1 und Produkten kann selektiv durchgeführt werden.
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  • 182
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 145-149 
    ISSN: 0009-2940
    Keywords: Cycloalkenes, 1-methyl- ; Ozonolysis ; Peroxyhemiacetals, cyclic ; Rubber, natural ; Tetrahydrofurans, 2-hydroperoxy- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ozonolyses of 1-Methylcyclopentene, 1-Methylcyclobutene, 5-Hexen-2-one and Natural Rubber in the Presence of MethanolOzonolyses of 1-methylcyclopentene (8a) and of 1-methylcyclobutene (8b) in methanol proceeded in each case in the two possible directions. The resulting methoxyperoxides 13 and 14 afforded the corresponding peroxyhemiacetals 15 and 19 by intramolecular reactions of the OOH with the corresponding carbonyl groups. Ozonolysis of 1-methylcyclobutene (8b) additionally gave the corresponding ozonide 17b and 2-hydroperoxy-5-methoxy-2-methyl-as well as 5-hydroperoxy-2-methoxy-2-methyltetrahydrofuran (16b and 18b). The mode of formation of these hydroperoxy compounds has been elucidated by ozonolyses of 5-hexen-2-one (25) and of natural rubber (28) in the presence of methanol.
    Notes: Ozonolysen von 1-Methylcyclopenten (8a) und von 1-Methylcyclobuten (8b) in Methanol verliefen jeweils nach beiden möglichen Spaltungsrichtungen. Die dabei gebildeten Methoxyhydroperoxide 13 und 14 ergaben durch intramolekulare Reaktionen der OOH- mit den Carbonylgruppen die entsprechenden Peroxyhalbacetale 15 bzw. 19. Bei der Ozonolyse von 1-Methylcyclobuten (8b) wurden zusätzlich das entsprechende Ozonid 17b sowie 2-Hydroperoxy-5-methoxy-2-methyl- und 5-Hydroperoxy-2-methoxy-2-methyltetrahydrofuran (16b und 18b) gebildet. Die Bildungsweise dieser Hydroperoxy-Verbindungen wurde durch Ozonolysen von 5-Hexen-2-on (25) und von Naturkautschuk (28) im Beisein von Methanol aufgeklärt.
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  • 183
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 169-174 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of New 3-substituted PyrrolesThe synthesis of 3-alkyl- (4), 3-(ω-bromoalkyl)- (5), 3-iodo- (6), 3-formyl- (9a), 3-acetyl-1-(triisopropylsilyl)pyrrole (9b), of 2-[1-(triisopropylsilyl)-3-pyrrolyl]-2-propanol (7), 1-(triisopropylsilyl)-3-pyrrolecarboxylic acid (8), and 7-[1-(triisopropylsilyl)-3-pyrrolyl]heptanoic acid (10) as well as the desilylation of these products to the corresponding 3-substituted pyrroles 11 is described. Intermediates in these syntheses are 1-(triisopropylsilyl)pyrrole (1), 3-bromo- (2), and 3-lithio-1-(triisopropylsilyl)pyrrole (3).
    Notes: Die Synthese von 3-Alkyl- (4), 3-(ω-Bromalkyl)- (5), 3-Iod- (6), 3-Formyl- (9a) und 3-Acetyl-1-(triisopropylsilyl)pyrrol (9b), von 2-[1-(Triisopropylsilyl)-3-pyrrolyl]-2-propanol (7), 1-(Triisopropylsilyl)-3-pyrrolcarbonsäure (8) und 7-[1-(Triisopropylsilyl)-3-pyrrolyl]heptansäure (10) sowie die Desilylierung dieser Produkte zu den entsprechenden 3-substituierten Pyrrolen 11 wird beschrieben. Zwischenstufen der Darstellung sind 1-(Triisopropylsilyl)pyrrol (1), 3-Brom- (2) und 3-Lithio-1-(triisopropylsilyl)pyrrol (3).
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  • 184
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989) 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 185
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 223-230 
    ISSN: 0009-2940
    Keywords: Gold(I) silyl complexes ; Transition-metal silyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Transition-Metal Silyl Complexes, 26. - Gold(I) Silyl ComplexesComplexes of type L-Au-SiR3 with L = PR′3 or PhNC and SiR3 = Si(aryl)3, Si(SiMe3)3, or SiPh2Me are prepared by reaction of L-Au-Cl with LiSiR3. Depending on L and R, their stability decreases, in the order R′3P-Au-Si(aryl)3 〉 R′3P-Au-Si(SiMe3)3 〉 R′3P-Au-SiPh2Me ≈ PhNC-Au-SiR3. Reaction of R′3P-Au-CH3 or R′3P-Au-OAc with HSiR3 does not yield silyl complexes. However, using chlorinated silanes like HSiR2Cl, CH3/Cl or OAc/Cl exchange takes place. The Mössbauer spectrum of MePh2P-Au-SiPh3 (6) and NMR- and IR-spectroscopic investigations show that silyl groups act as strong σ donors towards the gold atom. MePh2P-Au-SiPh3 (6) and MePh2P-Au-Si(SiMe3)3 (7) have been characterized by X-ray structure analyses [Au—Si 235.4(4) and 235.6(2) pm]. The Au-Si bond in MePh2P-Au-SiPh2Tol (5) is cleaved by X2 (X = Cl, Br, I), HCl or MeI, but not by H2O or MeOH.
    Notes: Komplexe des Typs L-Au-SiR3 mit L = PR′3 oder PhNC und SiR3 = Si(aryl)3, Si(SiMe3)3 oder SiPh2Me wurden durch Umsetzung von L-Au-Cl mit LiSiR3 dargestellt. Ihre Stabilität sinkt in Abhängigkeit von L und R in der Reihenfolge R′3P-Au-Si(aryl)3 〉 R′3P-Au-Si(SiMe3)3 〉 R′3P-Au-SiPh2Me ≈ PhNC-Au-SiR3. Umsetzung von R′3P-Au-CH3 oder R′3P-Au-OAc mit HSiR3 ergibt keine Silyl-Komplexe, bei Verwendung chlorierter Silane, HSi-R2Cl, findet lediglich CH3/Cl- bzw. OAc/Cl-Austausch statt. Das Mößbauer-Spektrum von MePh2P-Au-SiPh3 (6) sowie NMR- und IR-spektroskopische Untersuchungen zeigen, daß Silylreste als starke σ-Donor-Liganden gegenüber dem Goldatom wirken. MePh2P-Au-SiPh3 (6) und MePh2P-Au-Si(SiMe3)3 (7) wurden durch Röntgenstrukturanalysen charakterisiert [Au—Si 235.4(4) und 235.6(2) pm]. Die Au—Si-Bindung in MePh2P-Au-SiPh2 Tol (5) wird durch X2 (X = Cl, Br, I), HCl oder MeI, nicht aber durch H2O oder MeOH gespalten.
    Additional Material: 2 Ill.
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  • 186
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 245-252 
    ISSN: 0009-2940
    Keywords: Germylenes ; Germanium nitrogen compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Germylenes with Azides: Iminogermanes, Azidogermanes, Tetrazagermoles and HexaazadigermadispirododecanesGermylenes, X2Ge, stabilized by steric blocking and/or incorporation into five-membered ring systems, react with azido compounds YN3 depending on the steric requirements of the substituents X and Y to give iminogermanes, X2Ge=NY (1, 2) azidogermanes X2Ge(N3)NY2 (6-8) tetrazagermoles, X2Ge(— NY — N =)2 (10-16), and hexaazadigermadispirododecanes, [(— NR — CH2 — CH2 — NR —)Ge(μ-NY -)]2 (17, 18). NMR (1H, 13C, 14N, 15N, and 29Si), MS data, and X-ray structure analyses of the compounds 8, 9, 16, and 18 are reported.
    Notes: Durch sterische Blockierung und/oder Einbau in fünfgliedrige Ringsysteme stabilisierte Germylene, X2Ge, reagieren mit Azidoverbindungen, YN3, in Abhängigkeit von der Raumerfüllung der Substituenten X und Y zu Iminogermanen X2 Ge=NY (1, 2), Azidogermanen, X2Ge(N3)NY2 (6′8), Tetrazagermolen, X2Ge-(-NY-N=)2 (10-16), bzw. Hexaazadigermadispirododecanen, [(—NR—CH2—CH2—NR— )Ge(μ-NY-)]2 (17, 18). NMR-(1H, 13C, 14N, 15N und 29Si), MS-Daten und Röntgenstrukturanalysen für die Verbindungen 8, 9, 16 und 18 sind angegeben.
    Additional Material: 4 Ill.
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  • 187
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 271-277 
    ISSN: 0009-2940
    Keywords: Chalcogenogermanes, (trifluoromethyl)- ; Disilaselenanes ; Germachalcogenanes, bis(trifluoromethyl)- ; Germanes, (trifluoromethyl)- ; Germatranes, (trifluoromethyl)- ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: (Trifluormethyl)germanes, III. - Preparation of New (Trifluormethyl)germanium Chalcogene CompoundsStarting with the dihalogenobis(trifluoromethyl)germanes (CF3)2-GeX2 (X = Cl, or I), halogen-chalcogen exchange leads to corresponding chalcogen derivatives of the general type [(CF3)2GeE]n (6, 7) (E = O, NH, S, or Se). The resulting compounds differ in their degree of polymerisation. [(CF3)2GeO]x and the corresponding sesquioxane [(CF3)GeO1, 5]x are highly polymeric, quite in contrast to the corresponding germathianes and -selenanes. The crystal structure of [(CF3)2GeO]x (6a) was determined by X-ray single crystal diffraction. The reaction of CF3GeCl3 with triethanolamine results in the formation of 1-(trifluoromethyl)germatrane (13). Disilaselenane (10) reacts at low temperatures with chloro-(trifluoromethyl)germanes (CF3)nGeCl4-n under retention of one Si—Se bond to give (CF3)nGe(SeSiH3)4-n (11) and H3SiCl. Compounds with n = 3 and 2 could be isolated. Exchange of iodine by ECF3 takes place with iodogermanes (CF3)nGeI4-n and Hg(ECF3)2 (E = S, Se) with formation of a complete series of (trifluoromethyl)(trifluoromethylchalcogeno)germanes (CF3)nGe-(ECF3)4-n (3, 5).
    Notes: Durch Halogen-Chalkogen-Austauschreaktionen an (CF3)2)GeX2 (X = Cl, I) wurden Bis(trifluormethyl)germachalkogenane [(CF3)2GeE]n (6, 7) E = O, NH, S, Se) von unterschiedlichem Oligomerisierungsgrad erhalten. Die Germoxane [(CF3)2GeO]x und (CF3GeO1,5)x sind im Gegensatz zu den homologen Germathianen und -selenanen polymer, wobei die Struktur von [(CF3)2GeO]x (6a) durch eine Kristallstrukturanalyse ermittelt wurde. Durch Umsetzung von CF3GeCl3 mit Triethanolamin wird 1-(Trifluormethyl)germatran (13) erhalten. Disilaselenan (10) reagiert bei tiefen Temperaturen mit den Chlor (trifluormethyl)-germanen (CF3)nGeCl4-n monofunktionell unter Erhalt einer Si—Se-Bindung zu (CF3)nGe(SeSiH3)4-n (11) und H3SiCl, von denen die Verbindungen mit n = 3 und 2 isoliert werden konnten. Reaktionen der Iodgermane (CF3)nGeI4-n(1) mit Hg(ECF3)2) (E = S, Se) führen unter Substitution des Iods gegen die ECF3-Gruppen zur vollständigen Reihe der (Trifluormethyl)(trifluormethylchalkogeno)germane (CF3)nGe(ECF3)4-n (3, 5).
    Additional Material: 3 Ill.
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  • 188
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 291-292 
    ISSN: 0009-2940
    Keywords: (Phthalocyaninato)copper complex, substituted with crown ethers ; Alkali metal extraction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A soluble (phthalocyaninato)copper(II) complex containing eight symmetrical benzo-15-crown-5 substituents, namely {2,3,9,10,16,17,23,24-octakis[[benzo-15-crown-5)-4′ -yl]oxymethyl]phthalocyaninato}copper(II) (2) from 1,2-bis{[benzo-15-crown-5)-4′-yl]oxymethyl}-4,5-dibromobenzene (1) and CuCN in quinoline or pyridine was synthesized. The crown-ether groups in 2 were shown to prefer intramolecular complexation with alkali metal ions.
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  • 189
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 463-466 
    ISSN: 0009-2940
    Keywords: C—C Rotation ; Sterical hindrance by SF5 groups ; Rotational barriers ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sterical Hindrance of the C—C Rotation by two SF5 GroupsAddition of SF5Cl to SF5CH=CF2 gives products carrying two SF5 groups on one carbon atom. As a consequence, C—C single bond rotation is strongly hindered. The highest rotational barrier observed is 61.7 kJ mol-1, rotational isomers are hence detectable at room temperature.
    Notes: Die Addition von SF5Cl an SF5CH=CF2 ergibt Produkte, die zwei SF5-Gruppen an einem Kohlenstoff tragen. In diesen kommt es zu einer starken Hinderung der Rotation um die C—C-Einfachbindung. Die höchste Rotationsbarriere wird mit 61.7 kJ mol-1 gefunden, d. h. Rotationsisomere sind bei Raumtemperatur getrennt nachweisbar.
    Additional Material: 4 Ill.
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  • 190
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 467-472 
    ISSN: 0009-2940
    Keywords: Tetracarbonylchromium complexes ; 1,2,3,6-Tetrahydro-1,2,3,6-diphosphadiborine derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis, Structure, and Reactions of 1,2,3,6-Tetrahydro-1,2,3,6-diphosphadiborine DerivativesThe 1,2,3,6-tetrahydro-1,2,3,6-diphosphadiborine derivatives 3a and 3b are obtained by cyclocondensation of 1,2-bis[chloro(dialkylamino)boryl]ethenes 2 and 1,2-dipotassium 1,2-di-tert-butyldiphosphanediide. As in the case of 2,5-dihydro-1H-1,2,5-phosphadiborole derivatives 1 the temperature-dependent 1H-NMR spectra of 3b exhibit a lowered barrier of inversion at phosphorus. The X-ray structure analysis of 3b shows, that the six-membered C2B2P2 ring is nonplanar and the P atoms are coordinated pyramidally. Attempts to substitute the dialkylamino groups at the boron atoms of 3a and 3b with HCl·Et2O or tBuLi lead to cleavage of the B—P bonds. Reaction between 3a or 3b and Cr(CO)3(MeCN)3 does not result in the formation of tricarbonylchromium complexes but of tetracarbonylchromium complexes 6a and 6b with pentahapto-bonded ligands 3a and 3b.
    Notes: Die 1,2,3,6-Tetrahydro-1,2,3,6-diphosphadiborin-Derivate 3a und 3b entstehen durch Cyclokondensation aus 1,2-Bis[chlor(dialkylamino)boryl]ethenen 2 und 1,2-Dikalium-1,2-di-tert-butyldiphosphandiid. Die Temperaturabhängigkeit der 1H-NMR-Spektren von 3b dokumentiert wie bei 2,5-Dihydro-1H-1,2,5-phosphadiborol-Derivaten 1 eine erniedrigte Phosphor-Inversionsbarriere. Die Röntgenstrukturanalyse von 3b zeigt, daß der C2B2P2-Sechsring im Kristall nicht eben ist und daß die P-Atome pyramidal koordiniert sind. Versuche zur Substitution der Dialkylaminogruppen an den Boratomen von 3a und 3b mit HCl·Et2O oder tBuLi führen zur Spaltung der B—P-Bindungen. Die Umsetzung von 3a bzw. 3b mit Cr(CO)3(MeCN)3 ergibt keine Tricarbonylchrom-Komplexe, sondern die Tetracarbonylchrom-Komplexe 6a bzw. 6b, in denen die Liganden 3a und 3b pentahapto gebunden sind.
    Additional Material: 7 Tab.
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  • 191
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organic Synthesis via Transition Metal Complexes, 34. - Novel Formation of C=C Bonds by Condensation of Acid Amides with Carbene Complexes Involving an Insertion of C2 Units into M=C BondsCarben complexes LnM=C(OEt)C6H5 1 [LnM = Cr(CO)5, Mo(CO)5, W(CO)5] and acid amides RCH2CONMe2 2 undergo a novel condensation reaction in presence of POCl3/Et3N to give alkenyl aminocarbene complexes 3. The reaction involves an insertion of a C2 unit of 2 into the M=C bond of 1 to give a C=C bond. It can be achieved with open-chain and cyclic amides like N-methyl-2-pyrrolidone (8). the structures of the complexes have been determined spectroscopically. A mechanism of the reaction is suggested.
    Notes: Carbenkomplexe LnM=C(OEt)C6H5 1 [LnM = Cr(CO)5, Mo(CO)5, W(CO)5] lassen sich mit Säureamiden RCH2CONMe2 2 und POCl3/Et3N zu Alkenyl-Aminocarben-Komplexen 3 kondensieren. Dabei wird eine C2-Einheit von 2 in die M=C-Bindung von 1 eingeschoben und eine C=C-Bindung neu geknüpft. Die Reaktion gelingt mit offenkettigen und cyclischen Amiden wie N-Methyl-2-pyrrolidon (8). Die Strukturen der Komplexe wurden spektroskopisch ermittelt und Vorschläge zur Deutung des Reaktionsablaufs gemacht.
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  • 192
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 711-714 
    ISSN: 0009-2940
    Keywords: Azulenes ; 1,6-Methano[10]annulenes ; 1,2,4,5-Tetrazine ; [4 + 2] Cycloadditions, „inverse“ ; Pyridazines, annulated ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Azulene and 1,6-Methano[10]annulene as Dienophiles in the Diels-Alder Reaction with 3,6-Bis(trifluoromethyl)-1,2,4,5-tetrazineThe LUMO-diene-controlled [4 + 2] cycloadditions of azulene (2) and 1,6-methano[10]annulene (14) with the electron-deficient s-cisfixed diazadiene system of 3,6-bis(trifluoromethyl)-1,2,4,5-tetrazine (1) are described. Contrary to expectation, 1 reacts under unusually mild conditions with 2 (or its valence tautomer 3) to yield the adduct 4 which after N2 elimination rearranges to the benzo[f]phthalazine 11. The Diels-Alder reaction of 1 with 14 (or its valence tautomer 13) leads to the annulated dihydropyridazines 15 and 16, which can be dehydrogenated by silver(I) oxide to the methano-bridged aromatic cyclodecapyridazine 17 and the olefinic phthalazino[5,6-f]phthalazine 18, respectively. Besides, the methano-bridged cyclodeca[d]pyridazine 24 is prepared.
    Notes: LUMO-Dien-kontrollierte [4 + 2]-Cycloadditionen von Azulen (2) und 1,6-Methano[10]annulen (14) an das elektronenarme, s-cis-fixierte Diazadiensystem von 3,6-Bis(trifluoromethyl)-1,2,4,5-tetrazin (1) werden beschrieben. Wider Erwarten reagiert 1 unter ungewöhnlich milden Bedingungen mit 2 (oder dessen Valenztautomerem 3) zum Addukt 4, das nach N2-Eliminierung und nachfolgender Umlagerung das Benzo[f]phthalazin 11 liefert. Die Diels-Alder-Reaktion von 1 mit 14 (oder dessen Valenztautomer 13) führt zu den beiden anellierten Dihydropyridazinen 15 und 16, die mit Silber(I)-oxid zu dem Methano-überbrückten aromatischen Cyclodecapyridazin 17 bzw. dem olefinischen Phthalazino[5,6-f]phthalazin 18 dehydriert werden können. Daneben wird das Methano-überbrückte Cyclodeca[d]pyridazin 24 dargestellt.
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  • 193
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 715-719 
    ISSN: 0009-2940
    Keywords: Alkyne ; Carbene ; Cycloisomerization ; Pyrolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Über die thermische Cycloisomerisierung langkettiger Alkylacetylene in der GasphaseDie thermische Cycloisomerisierung einiger Alkylacetylene wurde in einem Laborrohrreaktor aus Quarzglas untersucht. 1-Hexin (1) wird dabei durch 1,2-H-Verschiebung und 1,5-C,H-Insertion des intermediär gebildeten Pentylidencarbens (vgl. Schema 1) in 3-Methyl-1-cyclopenten (5) umgelagert. 5-Methyl-1-hexin (2) reagiert analog; es entsteht 3,3-Dimethyl-1-cyclopenten (6). Im Gegensatz zur Bildung von in 3-Stellung methylierten Cyclopentenen aus 1-Alkinen ensteht aus 2-Hexin (3) 1-Methyl-1-cyclopenten (7). Offenbar ist die Acetylen-Vinyliden-Umlagerung nicht auf 1,2-H-Verschiebung beschränkt. Der Mechanismus der Cycloisomerisierung von Alkylacetylenen wird durch Untersuchungen mit D-markierten Alkinen bestätigt. Die Ergebnisse lassen den Schluß zu, daß die Cycloisomerisierung ohne weiteres mit dem überwiegend nach einem Radikalketten-Mechanismus verlaufenden thermischen Zerfall konkurrieren kann.
    Notes: The thermal cycloisomerization of some alkylacetylenes was investigated in a tubular quartz reactor. At 570°C 1-hexyne (1) rearranges to 3-methyl-1-cyclopentene (5) with a selectivity of about 27 by a reaction sequence including an acetylene-vinylidene rearrangement and 1,5-C,H insertion of the intermediately formed alkylidenecarbene species. 5-methyl-1-hexyne (2) behaves analogously forming 3,3-dimethyl-1-cyclopentene (6), while 2-hexyne (3) provides 1-methyl-1-cyclopentene (7) indicating that the acetylene-vinylidene rearrangement is obviously not restricted to 1,2-H shifts. The mechanism of the cycloisomerization of alkylacetylenes is investigated by means of D-labeled parent alkynes. The results show that the unimolecular cycloisomerization via alkylidenecarbenes obviously can be an important channel despite the dominance of a radical chain course.
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  • 194
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 745-748 
    ISSN: 0009-2940
    Keywords: Flash Pyrolysis ; Matrix IR spectroscopy ; Photolysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Methoxy- und AminoisocyanatMethoxyisocyanat (1) kann durch Photolyse von Azidoameisensäure-methylester (3) oder Pyrolyse von N-Methoxycarbonyl-O-methylhydroxylamin (4) dargestellt werden. Aminoisocyanat (2) ist auf ähnliche Weise durch Photolyse von Carbamoylazid (12) und Pyrolyse von Carbazinsäure-methylester (13) oder 3,4-Diaminofurazan (14) zugänglich. Die IR-Spektren von 1 und 2, aufgenommen in einer Argon-Matrix bei 10 K, werden diskutiert.
    Notes: Methoxyisocyanate (1) can be prepared by photolysis of methyl azidoformate (3) or pyrolysis of N-methoxycarbonyl-O-methyl-hydroxylamine (4). Aminoisocyanate (2) is similarly formed on photolysis of carbamoyl azide (12) and pyrolysis of either methyl carbazate (13) or 3,4-diaminofurazan (14). The infrared spectra of 1 and 2 in an argon matrix at 10 K have been measured, and some of their properties are discussed.
    Additional Material: 1 Ill.
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  • 195
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 749-752 
    ISSN: 0009-2940
    Keywords: Matrix isolation ; Photochemistry ; Theoretical vibrational spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Infrarot-Spektren und Photochemie von Isodiazen und seinen deuterierten IsotopomerenDie Matrixisolation von Aminoisocyanat eröffnet einen neuen ergiebigen Weg zur Darstellung von Isodiazen (Aminonitren). Damit ist es möglich geworden, nicht nur sein IR-Spektrum eindeutig festzulegen und mit Hilfe von ab-initio-Rechnungen zu interpretieren, sondern auch seine Photochemie zu untersuchen.
    Notes: The matrix isolation of aminoisocyanate opens a new efficient route for the preparation of isodiazene (aminonitrene). Its infrared spectrum can now, with the help of ab initio calculations, be interpreted, and its photochemistry can be studied.
    Additional Material: 2 Ill.
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  • 196
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 795-796 
    ISSN: 0009-2940
    Keywords: Thiochalcones ; Thienylchalcones ; Fries rearrangement ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four new thienylchalcones (1, 4, 5, and 6) were synthesized by condensing hydroxy-nitroacetophenones with 2-thiophene and 3-thiophenecarboxaldehydes in the presence of dilute NaOH.
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  • 197
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 767-779 
    ISSN: 0009-2940
    Keywords: Molecular twisting ; cis-9,10-Dihydronaphthalenes, persubstituted ; Valence isomerizations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Valence Isomerizations, 17. - Persubstituted cis-9,10-Dihydronaphthalenes and their Valence IsomerizationsThe tricyclic diester 10 is available from 2-butyne in a six-step synthesis with an overall yield of 10%. Thermolysis of 10 gives the bicyclic diester 11 which upon UV irradiation yields 12 as the first persubstituted cis-9,10-dihydronaphthalene. X-ray analysis of 12 shows the molecule considerably twisted along the central bond. In addition, the planes of the ester groups are at an angle of approximately 60° to the „planes“ of the six-membered rings so that conjugation of the diene systems with the carbonyl functions is virtually interrupted, an effect which is reflected by the unusual spectroscopic properties of 12. The same structural features can be found in decamethyl-cis-9,10-dihydronaphthalene (16). When heated slightly, 12 is converted to the tetracyclic valence isomer 34. On reduction of 12 with diisobutylaluminum hydride both, dihydronaphthalene dicarbinol 25 as well as its unexpected positional isomer 26, are formed depending on the reaction conditions. Etherification of the reduction products with CH2N2/Et2O—BF3 furnishes a mixture of the three isomeric bis(methoxymethyl) compounds 31, 32 and 33. They can be separated by chromatography in the cold, but revert to the mixture of the three isomers at room temperature. We consider diradical 38 to be the intermediate of this intriguing valence isomerization.
    Notes: Der tricyclische Diester 10 ist in sechs Stufen in einer Gesamtausbeute von 10% aus 2-Butin zugänglich. Thermolyse von 10 liefert den Bicyclus 11, bei dessen UV-Bestrahlung das erste persubstituierte cis-9,10-Dihydronaphtalin 12 gebildet wird. Eine Röntgenstrukturanalyse von 12 beweist die starke Verdrillung des Moleküls um die zentrale Bindung. Die Ebenen der Ester-Gruppen stehen ungefähr in einem 60°-Winkel zu den Sechsring-„Ebenen“, so daß die Konjugation der Dien-Systeme mit den Carbonyl-Funktionen praktisch unterbrochen ist, ein Effekt, der sich in den ungewöhnlichen spektroskopischen Eigenschaften von 12 widerspiegelt. Analoge Strukturmerkmale gelten auch für das Decamethyl-cis-9,10-dihydronaphthalin (16). Bicyclus 12 wandelt sich bei leichtem Erwärmen in den valenzisomeren Tetracyclus 34 um. Reduktion von 12 mit Diisobutylaluminiumhydrid gibt je nach den Reaktionsbedingungen das Dihydronaphthalindicarbinol 25 bzw. das unerwartete Stellungsisomere 26. Veretherung der Reduktionsprodukte mit CH2N2/Et2O—BF3 liefert ein Gemisch der drei isomeren Bis(methoxymethyl)-Verbindungen 31, 32 und 33, die chromatographisch in der Kälte trennbar sind, aber schon bei Raumtemperatur wieder das Gemisch der drei Isomeren zurückbilden, wobei das Diradikal 38 als Zwischenprodukt dieser erstaunlichen Valenzisomerisierung anzunehmen ist.
    Additional Material: 2 Ill.
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  • 198
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 803-808 
    ISSN: 0009-2940
    Keywords: Bismuth organic compounds ; Fluorinated aromatic rings ; Square pyramidal bismuth ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Structures of Pentaarylbismuth CompoundsPentaarylbismuth compounds were synthesized by the known reaction Ar3BiX2 + 2 Ar′Li → 2 LiX + BiAr3Ar′2. Whenever possible they were characterized by single-crystal X-ray structure determination. In two cases almost ideal square-pyramidal geometry was found, in a third case there were two different molecules in the unit cell, both again with square-pyramidal geometry. None of these novel bismuth pentaaryls exhibit the deep coloration and the dichroism of Bi(C6H5)5.
    Notes: Pentaarylbismut- Verbindungen wurden durch die bekannte Reaktion BiAr3X2 + 2 Ar′Li → 2 LiX + BiAr3Ar′2 hergestellt und, soweit möglich, durch Röntgenbeugung an Einkristallen strukturell untersucht. In zwei Fällen erwies sich die Struktur als nahezu ideal quadratisch-pyramidal, in einem dritten Fall wurden zwei unterschiedliche Moleküle im Kristall gefunden, die aber beide wiederum quadratisch-pyramidal sind. Keines der hier vorgestellten neuen Bismutpentaaryle zeigt die tiefe Färbung und den Dichroismus von Bi(C6H5)5.
    Additional Material: 5 Ill.
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  • 199
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    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 533-535 
    ISSN: 0009-2940
    Keywords: Free radicals ; Triphenylmethyl radicals ; ESR measurements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Sterically Hindered Free Radicals, XIX. - Stable 4,4′,4″-Trisubstituted Triphenylmethyl RadicalsThe title radicals (4-R—C6H4)3C. (1), R = F, Cl, Ph, OMe, NO2, tBu, OEt, SMe, CN, CF3, have been prepared, the latter four for the first time, and the ESR spectra have been recorded. aoH, amH, and apR are listed. The intensities of the ESR signals remain constant within the accessible range of -30 to + 100°C. Within this range these radicals are kinetically stable and do not dimerize like other trityls by, e.g., α,p-, α,o-, α,α -recombinations.
    Notes: Die Titelradikale (4-R—C6H4)3C· (1), R = F, Cl, Ph, OMe, NO2, tBu, OEt, SMe, CN, CF3, wurden dargestellt, davon die vier letzten erstmalig, und mittels ESR-Spektroskopie vermessen. aoH, amH und apR werden angegeben. Die ESR-Signale bleiben im gesamten zugänglichen Temperaturbereich - 30 bis + 100°C in ihrer Intensität unverändert. Daraus folgt, daß alle diese Radikale im genannten Temperaturbereich kinetisch stabil sind, also nicht wie andere Trityle zu Dimerisierungen, etwa α,p-, α,o-, α,α-, neigen.
    Additional Material: 1 Tab.
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  • 200
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 523-531 
    ISSN: 0009-2940
    Keywords: Dicyclopenta-s-indacene ; 2-Osxa[3.3.3]propellane derivatives ; Pentalene derivatives ; [3.3.3]Propellane-3,7-dione ; Weiss reaction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Novel Products in the Weiss Reaction of 1,2-Cyclopentanedione. Improved Preparation of [3.3.3]Propellane-3,7-dioneThe reaction of 1,2-cyclopentanedione (1c, 9) with the 3-oxoglutarate 4 in methanol/water in the presence of sodium bicarbonate followed by hydrolysis and decarboxylation of the product mixture affords the oxa[3.3.3]propellane ester 11c in addition to the [3.3.3]propellanedione 6c. The alkali enolates of 4 react with 9 in boiling methanol to yield the yellow, poorly soluble alkali dihydropentalenolates 12M and the [3.3.3]propellane tetraester 5c, which on hydrolysis and decarboxylation yields 53% of 6c. The dihydropentalenol 12H equilibrates with the tautomeric β-oxodiester 13, the proportion of which increases with solvent polarity. In methanol solutions, 12H and 13 add diastereoselectively forming the dicyclopenta-s-indacene tetraester syn-14, which is derived from a novel pentacyclic ring system. The configuration of syn-14 is determined by X-ray diffraction analysis. The mechanisms of formation are discussed for 11c, 12M, and syn-14.
    Notes: Nach Umsetzung von 1,2-Cyclopentandion (1c, 9) mit dem 3-Oxoglutarsäureester 4 in Methanol/Wasser in Gegenwart von Natriumhydrogencarbonat, saurer Hydrolyse und Decarboxylierung des Produktgemischs erhält man neben dem [3.3.3]Propellandion 6c den Oxa[3.3.3]propellanester 11c. Die Alkali-Enolate von 4 reagieren mit 9 in siedendem Methanol zu den gelben, schwer löslichen Dihydropentalenolaten 12M und dem [3.3.3]Propellantetraester 5c, der nach Hydrolyse und Decarboxylierung 53% 6c ergibt. Das Dihydropentalenol 12H liegt im Gleichgewicht mit dem tautomeren β-Oxodiester 13 vor, dessen Anteil mit der Polarität des Lösungsmittels zunimmt. In Methanol addieren sich 12H und 13 diastereoselektiv und bilden den Dicyclopenta-s-indacentetraester syn-14, der sich von einem neuartigen, pentacyclischen Ringsystem ableitet. Die Konfiguration von syn-14 wird durch Röntgenstrukturbestimmung aufgeklärt. Die Mechanismen der Bildung von 11c, 12M und syn-14 werden diskutiert.
    Additional Material: 2 Ill.
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