Highly selective alpha-acylvinyl anion additions to imines.

alpha-Hydroxypropargylsilanes undergo rearrangement to form reactive lithium allenolates. The resulting alpha-acylvinyl anion equivalents undergo highly selective additions to N-tert-butanesulfinyl imines generating beta-substituted aza-MBH-type products. High yields are achieved for a wide range of alpha-hydroxypropargylsilanes as well as for a diverse selection of imines. The reactions proceed with good to excellent diastereoselectivity and regioselectivity (8-20:1 major/ Sigma minor) favoring the Z-isomer of the alkene.