Construction of quaternary stereogenic carbon centers by the Lewis base catalyzed conjugate addition of silyl ketene imines to α,β- unsaturated aldehydes and ketones

Highly site-selective Mukaiyama-Michael additions of silyl ketene imines to α,β-unsaturated aldehydes and ketones are described. The combination of silicon tetrachloride and a chiral bisphosphoramide provides an effective catalyst system for promoting the addition of silyl ketene imines to a variety of aromatic enals with high site selectivity and moderate to good diastereo- and enantioselectivity.