Discovery of chiral catalysts by asymmetric activation for highly enantioselective diethylzinc addition to imines: using racemic and achiral diimines as effective activators

A library of chiral zinc complexes formed in Situ by the combination of achiral and racemic diimines with 3,3'-di(3,5-ditrifluoromethylphenyl)-BINOL and diethylzinc were evaluated in the asymmetric addition of diethylzine to N-acylimines. In the presence of 10 mol % of chiral ligand 4 and racemic diimine 5, high enantioselectivities of up to 97% ee and yields of up to 96% were achieved for a wide range of aromatic imines in dichloromethane at -30 degrees C. (c) 2005 Elsevier Ltd. All rights reserved.