Enantioselective Borodeuteride Reduction of Aldimines Catalyzed by Cobalt Complexes:  Preparation of Optically Active Deuterated Primary Amines

The enantioselective borodeuteride reduction catalyzed by optically active β-ketoiminato cobalt complexes was applied to N-(di(o-tolyl)phosphinyl)aldimines to afford the corresponding optically active deuterated primary amines in high yields with high enantiomeric excesses after simple deprotection. The present deuteride reduction of aldimines is in the opposite sense of the enantioselective for the previously reported borohydride reduction of ketones or diphenylphosphinyl aldimines. The stereochemical course in these enantioselective reductions is discussed.