Enantioselective catalytic addition of allyl organometallic reagents to aldehydes promoted by [Cr(Salen)]: the hidden role played by weak Lewis acids in metallo-Salen promoted reactions

In this paper, we present the data obtained from kinetic analysis and from NLE study in the [Cr(Salen)] catalysed addition of allyl halides to aldehydes. The results show the key role played by weak Lewis acids in the catalytic system. Weak Lewis acids such as manganese salts and the [Cr(Salen)X] complex drive the stereochemistry of the reaction toward a high level of diastero- and enantioselectivity. Therefore, the Lewis acids and their properties must be taken into account in the rational design of metallo-Salen mediated processes. (C) 2001 Elsevier Science Ltd. All rights reserved.