The dual-catalyzed (amino alcohol Lewis acid) enantioselective addition of diethylzinc to N-diphenylphosphinoyl imines

摘要

Optimal structural characteristics within a family of (2R,3R)-1-alkoxy-3-dialkylamino-3-phenyl-2-propanols have been determined for maximum enantioselectivity in the addition of diethylzinc to N-diphenylphosphinoyl imines (1-alkoxy = trityloxy; 3-dialkylamino = piperidino). The simultaneous use of silylating agents acting as Lewis acids to induce rate acceleration has been investigated, allowing the identification of triisopropylsilyl chloride and tert-butyldiphenylsilyl chloride as the most efficient mediators in terms of rate enhancement and enantiomeric excess of the resulting phosphinamides. (C) 1999 Elsevier Science Ltd. All rights reserved. [References: 18]