Olefin epoxidation by a (salen)Mn(iii) catalyst covalently grafted on glass beads

Abstract

The asymmetric epoxidation of unfunctionalized prochiral olefins catalyzed by chiral (salen)Mn(III) complexes is an important viable route to obtain chiral epoxides. Recently we proposed a monolayer of (salen)Mn(III) molecules on functionalized flat silica substrates as an active heterogeneous catalyst for enantioselective epoxidation of 6-cyano-2,2-dimethylchromene with huge turnover values. In the present study we synthesized a monolayer of modified (salen)Mn(III) molecules on previously functionalized glass bead substrates in order to increase the active surface area. The catalyst activity of this system was tested with different olefins and in some cases we observed enantioselectivity higher than in solution. The system was reused up to seven times with no variation in performance.