A Switch of Facial Selectivities Using α-Heteroatom-Substituted Aldehydes in the Vinylogous Mukaiyama Aldol Reaction

The vinylogous Mukaiyama aldol reaction (VMAR) of chiral nonracemic ketene silyl N,O-acetal with various aldehydes is demonstrated. VMAR with α-heteroatom-unsubstituted aldehydes proceeded with a high degree of anti-selectivity. In sharp contrast, moderate to high syn-selectivity was observed when α-heteroatom-substituted aldehydes were used.