著者

大胡 惠明 武内 征司 吉村 寿次

出版者

天然有機化合物討論会

雑誌

天然有機化合物討論会講演要旨集

巻号頁・発行日

no.14, pp.101-107, 1970-10-01

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Catalytic asymmetric hydrogenation of benzil was examined by use of bis-dimethylglyoximato cobalt(II)-optically active amine complex. This system gave an extroadinarily high optical yield (50%) never seen before in the case of homogeneous metal complex-catalyzed asymmetric syntheses. The results were summarized as follows. a) Co(DMG)_2 complexes with optically active polyfunctional bases such as quinine, quinidine, cinchonidine, O-acetyl-quinine and brucine resulted in asymmetric hydrogenation, especially amino alcohols were highly effective. However, simple amine could not affect asymmetric induction. b) Increase in the molar ratio of substrate to cobalt or base does not bring about decrease in optical yield, but rather small increase. c) It is worthy to mention that molar equivalent of optically active base is enough to affect asymmetric induction. d) Asymmetric yield increased with increasing polarity of the solvent used. This asymmetric reaction is presumably due to an asymmetry induced on the bis-dimethylglyoxime ring by optically active axial base, provided that this reaction proceeds through the same mechanism as alkyl-Co(DMG)_2B formation from Co(DMG)_2B and olefines under hydrogen atmosphere.

著者

吉村 寿次 佐藤 憲一

出版者

The Society of Synthetic Organic Chemistry, Japan

雑誌

有機合成化学協会誌 (ISSN:00379980)

巻号頁・発行日

vol.40, no.5, pp.415-426, 1982-05-01 (Released:2009-11-13)

参考文献数

72

被引用文献数

2 2

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Stereoselectivities in the nucleophilic addition of various nucleophiles to various 2-, 3-, 4-uloses were examined, and discussions were made on the possible, conformational change of substrates and on the following, three, main factors to control the stereoselectivities depending on the nature of reactions ; a) non-bonded interactions, after the preceding, conformational change by the coordination of magnesium to the C=O and adjacent C-O oxygens (methylmagnesium iodide) or by the solvent-dependent, dipole repulsion between the C=O and C-O bonds (methyllithium), b) intramolecular, electrostatic, attractive force between an axial oxygen or lone-paired electron of ringoxygen and diazomethyl cation in the transition states (diazomethane), c) thermodynamical stabilities of epimers to be produced in equilibration reaction.