Modification of (1R,2S)-l,2-Diphenyl-2-aminoethanol for the Highly Enantioselective,Asymmetric Alkylation of N-Diphenylphosphinoyl Arylimines with Dialkylzinc

摘要

Experimental studies on the modification of (lR,2S)-l,2-diphenyl-2-aminoethanol,which is used to promote the alkylation of N-diphenylphos-phinoyl benzalimine with diethylzinc,revealed that N-monosubstituted amino alcohols exhibited higher enan-tioselectivities than their N,N-disubstituted counterparts and imino alcohols.Application of the optimal chiral ligand 3c to activate the reaction of N-diphenylphosphinoyl arylimines with diethylzinc and dibutylzinc resulted in excellent enantiomeric selectivities of up to 98 % ee.The origin of the experimentally observed enantioselectivities was revealed by density functional calculations (B3LYP/6-31G~*) on the transition structures of several model reactions.