Asymmetric cyanosilylation of ketones catalyzed by bifunctional chiral N-oxide titanium complex catalysts

摘要

A new bifunctional catalytic system based on chiral N-oxide titanium complexes has been used for the asymmetric cyano-silylation of ketones. Screening of a variety of chiral N-oxide metal complexes resulted in (1R,2S)-1-(2'-pyridylmethyl)-2-(diphenylhydroxymethyl)pyrrolidine N-oxide titanium complex, which gave O-TMS cyanohydrins in good yields with enantiomeric excesses of up to 69%. A catalytic cycle based on experimental phenomena and studies was proposed to explain the origin of the asymmetric induction. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).