Vanadium-Schiff base complex covalently bonded on modified MCM-41 as catalyst for asymmetric oxidation of methyl phenyl sulfide

摘要

The vanadium-Schiff base complex was immobilized on mesoporous MCM-41 by a covalent grafting method using 3-aminopropyltriethoxysilane as a reactive surface modifier. The formation and integrity of the complex have been studied using XRD, FT-IR, UV-Vis, ESR, Si-29-MAS-NMR and N-2 adsorption-desorption. The heterogeneous VO(Schiff)-MCM catalyst shows an activity and an enantioselectivity comparable to those obtained with the homogeneous catalyst VO(Schiff), for the asymmetric oxidation of methyl phenyl sulfide. The combination of the heterogenous catalyst with CHP as oxidant offers a selective catalytic system for oxidation of methyl phenyl sulfide with a significant enantioselectivity in the range of 17-23 % ee. In addition, the heterogeneized catalyst could be easily separated from the products and reused.