A practical o-hydroxybenzylamines promoted enantioselective addition of dialkylzincs to aldehydes with asymmetric amplification

Abstract

The addition of dialkylzincs to aldehydes is accelerated considerably by the presence of a catalytic amount of o-hydroxybenzylamine (R,R)-2e to give, after hydrolysis, the corresponding alcohol (S)-9 in good enantiomeric purity. The origins of the enantioselection have been elucidated. A strong positive nonlinear relationship was observed for the reaction enantioselctivity with the use of o-hydroxybenzylamine 2e, which is very accessible through a short stereoselective synthetic route. The enantiomeric purity of the product 9 is much higher than the d.e. of the chiral source 2e, and the rate of the enantioselective catalysis increases considerably with the increase of the d.e. of (R,R)-2e. Copyright (C) 2000 Elsevier Science Ltd.