Chiral C2-symmetric 2,3-disubstituted aziridine and 2,6-disubstituted piperidine as chiral ligands in the addition reaction of diethylzinc with arylaldehydes

Article abstract of DOI:10.1016/S0957-4166(00)00479-1

Chiral C₂-symmetric 2,3-disubstituted aziridines and 2,6-disubstituted piperidines having a β-amino alcohol moiety have been successfully synthesized and their catalytic chiral induction properties have been examined in the asymmetric addition reactions of diethylzinc with arylaldehydes in hexane. When N-(2,2-diphenyl-2-hydroxyethyl)-(S,S)-2,3-bis(methoxymethyl)aziridine 11 was used as a catalytic chiral ligand, sec-alcohols having (S)-configuration formed in high yields of 86-92% but low enantiomeric excesses (ee's) of 11-13%. However, when N-(2,2-diphenyl-2-hydroxyethyl)-(R,R)-2,6-disubstituted piperidine derivatives 16 and 20 were used as the chiral ligands under the same reaction conditions, the ee's of the corresponding sec-alcohols were 20-30 and 5-6%, respectively, along with the inversion of absolute configuration. A plausible mechanism for this inversion is proposed.