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

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