名称:
Asymmetric Michael additions to .alpha.,.beta.-unsaturated oxazolines. An efficient preparation of chiral .beta.,.beta.-disubstituted propionaldehydes
摘要:
A short stereoselective route to a variety of chiral, nonracemic alpha,beta-unsaturated oxazolines derived from (S)-tert-leucinol is described. Addition of organolithium reagents to this chiral oxazoline occurs in a Michael fashion, giving rise to adducts with high diastereoselectivity. Reductive cleavage of the oxazoline leaves the beta,beta-disubstituted aldehydes in > 93% ee. This process represents a significant improvement in one of the earliest asymmetric conjugate additions first reported in 1975.