A novel polymeric chiral salen Mn(III) complex as solvent-regulated phase transfer catalyst in the asymmetric epoxidation of styrene

Abstract

A novel solvent-regulated phase transfer catalyst of polymeric chiral salen Mn(III) complex with chiral diamine bridging was synthesized and its performance in the asymmetric epoxidation of styrene was investigated. In comparison with its low molecular weight counterpart of the homogeneous monomeric chiral salen Mn(III) complex, the polymeric chiral salen Mn(III) complex showed similar yield and enantioselectivity of the epoxide under the same reaction conditions. The effects of axial base, reaction temperature, and solvent on the catalytic performance of the polymeric chiral salen Mn(III) complex were investigated systematically. It was found that, under optimal reaction conditions, the yield of the epoxide and the enantioselectivity were as high as 98 and 47%, respectively. Furthermore, the polymeric chiral salen Mn(III) complex could be conveniently recovered for recycled use. Indeed the complex could be reused at least three times without significant losses of both activity and enantioselectivity.