Monodisperse crosslinked pHEMA particle-supported chiral Mn(lll)salen catalyst for asymmetric epoxidation of olein

摘要

Monodisperse crosslinked poly(hydroxyethyl methacrylate) particles (pHEMA) were synthesized for immobilization of the chiral Mn(lll)salen homogeneous catalyst by axial coordination. The pHEMA-Mn(lll)salen catalyst was subsequently characterized by FT-IR, UV and scanning electron microscopy. The results showed that, the heterogeneous Mn(lll)salen catalysts also exhibited high activity and enantioselectivity compared to the homogeneous catalyst for the disubstituted cyclic indene and 6-cyano-2,2-dimethylchromene. Moreover, the catalysts were easily separated from the reaction systems and could be renewed several times without significant loss of catalytic activity. Meanwhile, the enantiomeric excess (ee) value remained at 80% in the eighth cycle. The pHEMA support, immobilized by Mn(lll)salen, probably acted as a mediator of the reaction between the substrate and the oxidant, and enhanced the stability of the Mn(III)salen compound.