Highly Active Chiral Dilithium(I) Binaphthyldisulfonate Catalysts for Enantio- and Chemoselective Strecker-Type Reactions

An enantioselective Strecker-type reaction of aldimines and ketimines was developed by using a chiral dilithium­(I) binaphthyldisulfonate as a chiral acid–base cooperative catalyst. The present catalytic system features an extremely short reaction time (10 min to 4 h), unlike conventional catalytic systems. Along with the design of stronger chiral Li­(I) Lewis acid catalysts, a highly reactive pentacoordinate silicate generated in situ could promote the reactions. In particular, instead of unstable N-Bn Strecker products, more stable N-CH2(9-anthryl) and N-CH2(1-naphthyl) Strecker products could be obtained in high yields with high enantioselectivities. By a switch of the present and previous catalyst systems, chemoselective cyanation to a ketoaldimine could be performed, respectively. Moreover, mechanistic investigations provided useful information regarding the active catalysts, catalytic cycles, and possible transition states.