The ortho effect:: copper-catalyzed highly enantioselective 1,4-conjugate addition of diethylzinc to chalcones

The copper-catalyzed enantioselective 1,4-conjugate addition of diethylzinc to chalcones was investigated in the presence of a catalytic amount of NP-ferrocenyl ligands with central and planar chirality under mild conditions (0 degrees C -> rt). It was found that chalcones with ortho-substituents (from ortho-substituted benzaldehydes and acetophenone/substituted acetophenones) led to a dramatic improvement in the enantio selectivities. The (R)- and (S)-antipodes of the addition reaction were obtained with up to 92% ee after this transformation. (c) 2006 Published by Elsevier Ltd.