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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 650-668 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparative, Spectroscopic, and Crystallographic Investigations on Phosphinato Complexes of Rhenium with Bidentate Nitrogen LigandsCholestano-cobaloximes and cholestano-rhodoximes, three diastereoisomers of each constitution, were synthesised from cholestane-2,3-dione dioxime (3). The diastereoisomeric complexes were separated and characterised by their spectra. One of the axial ligands was invariably pyridine, the other either chlor (9), methyl (10), 2,2-bis(methoxycarbonyl)propyl (11), 2,2-bis(benzyl-oxycarbonyl)propyl (12), or 2,2-bis(2-naphthylmethoxycarbonyl)propyl (13 and 14). Irradiation of the complexes 11, 12, 13, and 14 in ethanol or 2-propanol afforded, apart from dimethylmalonic diester, other products among which was the corresponding methylsuccinic diester in yields of approx. 1, 20, 23, and 13%, respectively. The methylsuccinic acid bis(2-naphthylmethyl ester) obtained from the irradiation of the diastereoisomeric cholestano-cobaloximes 13a, b and c was found to be practically racemic.
    Notes: Aus Cholestan-2,3-dion-dioxim (3) wurden jeweils drei diastereomere Cholestano-cobaloxime und Cholestano-rhodoxime synthetisiert, die getrennt und spektroskopisch charakterisiert wurden. Pyridin diente durchweg als einer der axialen Liganden, der andere war Chlor (9), Methyl (10), 2,2-Bis(methoxycarbonyl)propyl (11), 2,2-Bis(benzyloxycarbonyl)propyl (12) oder 2,2-Bis(2-naphthylmethoxycarbonyl)propyl (13 und 14). Bestrahlung der Komplexe 11, 12, 13 und 14 in Ethanol oder 2-Propanol gab neben den Dimethylmalonsäureestern und weiteren Produkten auch die entsprechenden Methylbernsteinsäure-diester in Ausbeuten von etwa 1, 20, 23 und 13%. Der aus den diastereomeren Cholestano-cobaloximen 13a, b und c erhaltene Methylbernsteinsäure-bis(2-naphthylmethylester) war praktisch racemisch.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2229-2241 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Steric Course of the Substitution at the Cyclopropane Skeleton by Cobal(I)oxime. Synthesis and Characterisation of Cyclopropylcobaloximes7,7-Dibromodibenzo[b,d]norcaradiene (1) as well as exo- and endo-7-bromodibenzo[b,d]norcaradiene (2a and b) were synthesized and reacted with cobal(I)oxime. (7-Bromodibenzo[b,d]norcaradien-7-yl)(pyridine)cobaloxime (5) was formed from 1 beside some (dibenzo[b,d]norcaradien-7-yl)(pyridine)cobaloxime (6) and (dibenzo[a,c]cycloheptatrien-6-yl)(pyridine)cobaloxime (4), whereas the reaction of 2a yielded 6 as the sole alkylcobaloxime. Under the same conditions 2b was inert. 4-6 were characterized by X-ray crystallography and spectroscopic methods. The substitution in 2a took place with retention, whereas the analogous substitution in the two enantiomeric 1-bromo-1-methyl-2,2-diphenylcyclopropanes (8a and b) occured with racemisation. This shows that the observed retention was caused merely by steric effects and that cyclopropyl radical intermediates occurred in both cases.
    Notes: 7,7-Dibromdibenzo[b,d]norcaradien (1) sowie exo- und endo-7-Bromdibenzo[b,d]norcaradien (2a und b) wurden synthetisiert und mit Cobal(I)oxim umgesetzt. Aus 1 erhielt man (7-Bromdibenzo[b,d]norcaradien-7-yl)(pyridin)cobaloxim (5) neben (Dibenzo[b,d]norcaradien-7-yl)(pyridin)cobaloxim (6) und (Dibenzo[a,c]cycloheptatrien-6-yl)(pyridin)cobaloxim (4), während aus 2a als einziges Alkylcobaloxim 6 gebildet wurde. 2b war unter denselben Reaktionsbedingungen inert. 4-6 wurden durch Röntgenstrukturanalyse und Spektren charakterisiert. Die Substitution an 2a erfolgte unter Retention, die analoge Substitution an den beiden enantiomeren 1-Brom-1-methyl-2,2-diphenylcyclopropanen (8a und b) dagegen unter Racemisierung. Dies zeigt, daß die im ersten Fall beobachtete Retention lediglich sterischen Effekten zuzuschreiben ist und in beiden Fällen eine freie Cyclopropyl-Radikal-Zwischenstufe auftritt.
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