Preparation of Diastereomerically Pure and Mixed (<i>S</i>)-PhGly/BIPHEP/Ru(II) Complexes and Their Catalytic Behavior with Li2CO3 in Asymmetric Cyanosilylation of Benzaldehyde

• Nobuhito Kurono

  Division of Chemical Process Engineering, Faculty of Engineering, Hokkaido University

• Taiki Katayama

  Division of Chemical Process Engineering, Faculty of Engineering, Hokkaido University

• Takeshi Ohkuma

  Division of Chemical Process Engineering, Faculty of Engineering, Hokkaido University

Abstract

A diastereomerically mixed complex [Ru{(S)-phgly}2{(±)-biphep}] is readily prepared from achiral diphosphine BIPHEP in two steps. These diastereomers are then separated by silica gel column chromatography. A 61:39 equilibrium mixture of [Ru{(S)-phgly}2{(S)-biphep}] and [Ru{(S)-phgly}2{(R)-biphep}] with Li2CO3 is used to catalyze cyanosilylation of benzaldehyde to afford the R cyanated product in 92% ee. The enantioselectivity is just slightly lower than that by using the pure [Ru{(S)-phgly}2{(S)-biphep}]/Li2CO3 catalyst system of 96%. The high enantioselective ability of the diastereomerically mixed catalyst is revealed through a series of kinetic experiments in which the highly enantioselective [Ru{(S)-phgly}2{(S)-biphep}]/Li2CO3 system is shown to catalyze the reaction 16.8 times faster than the less selective [Ru{(S)-phgly}2{(R)-biphep}]/Li2CO3 system, affording the product in 2.6% ee. An equation is derived to approximate the relationship between the diastereomeric ratio of the catalyst and the ee value of the product.

Journal

• Bulletin of the Chemical Society of Japan

  Bulletin of the Chemical Society of Japan 86 (5), 577-582, 2013-03-23

  Oxford University Press (OUP)

Keywords

• General Chemistry

Details

• CRID: 1360846644027023872
• NII Article ID: 10031167849
• NII Book ID: AA00580132
• DOI: 10.1246/bcsj.20120351
• ISSN: 13480634
• ISSN: 00092673
• Web Site: https://academic.oup.com/bcsj/article-pdf/86/5/577/56275267/bcsj.20120351.pdf
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