Chiral Salen Mn(III) Complex Axial Coordination Immobilized on Diamine Modified Alspp and Highly Efficient Large-Scale Epoxidation of Olefins as a Recoverable Catalyst

Abstract

Aluminium oligo-styrenyl phosphonate-hydrogen phosphate (AlSPP) was used as organic–inorganic hybrid support after chloromethylation, and then with using different diamines as a reactive surface modifier. We realized the homogeneous chiral salen Mn(III) complex axially immobilized on modified AlSPP by a covalent grafting method. The prepared heterogeneous salen Mn(III) complexes were characterized by different techniques such as FT-IR, diffusion reflection UV–Vis, AAS, XPS, N2 volumetric adsorption, SEM, TEM and TG. The chiral salen Mn(III) complexes were immobilized onto the AlSPP through axial coordination for the first time with m-CPBA/NMO as an oxidant system for asymmetric epoxidation of unfunctionalized olefins. The supported catalyst showed very good performance in the asymmetric epoxidation of α-methylstyrene and indene. The catalyst could be easily recovered and reused without significant loss of activity and enantioselectivity after nine cycles. This novel heterogeneous catalyst could be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which offer great possibilities for application in industry.