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 <i>N</i>,<i>O</i>-acetal with various aldehydes is demonstrated. VMAR with α-heteroatom-unsubstituted aldehydes proceeded with a high degree of <i>anti</i>-selectivity. In sharp contrast, moderate to high <i>syn</i>-selectivity was observed when α-heteroatom-substituted aldehydes were used.