Highly enantioselective cyanosilylation of aldehydes catalyzed by a Lewis acid–Lewis base bifunctional catalyst

A new bifunctional asymmetric catalyst containing a Lewis acid and a Lewis base (1) was developed and applied to the catalytic asymmetric cyanosilylation of aldehydes. The products were obtained generally with excellent enantiomeric excess. The experiments using the control catalyst (5) and the catalyst containing more electron-rich phosphine oxide (6) suggest that the catalyst 1 should promote the reaction via a dual activation of the aldehyde by the aluminum and TMSCN by the phosphine oxide. This reaction is practical and was applied to the catalytic asymmetric total synthesis of epothilone A.