Asymmetric addition of KCN and Ac2O to aldehydes catalyzed by recyclable polymeric salen-Ti(IV) complexes

Polymeric salen-Ti(IV) complexes were employed in the enantioselective O-acetyl cyanation of aldehydes with KCN and Ac2O. The polymeric catalysts with appropriate crosslinking degree exhibited good activities and enantioselectivities, up to 94% yield and 91% ee were obtained at -20degreesC with 1 mol% of catalyst (based on bimetallic catalytic unit). Moreover, the crosslinked polymeric catalyst could be easily recovered and reused for six consecutive runs without obvious decrease in activity and enantioselectivity. (C) 2004 Elsevier Ltd. All rights reserved.