An improved methyltrioxorhenium-catalyzed epoxidation of alkenes with hydrogen peroxide

Methyltrioxorhenium (MTO)-catalyzed epoxidation of alkenes with H(2)O(2) has been significantly improved by using 3-methylpyrazole as an additive. A system consisting of 35% H(2)O(2) and MTO-3-methylpyrazole in CH(2)Cl(2) catalyzes the epoxidation of various alkenes in excellent yields. The catalytic activity of MTO-3-methylpyrazole surpasses MTO-pyrazole and MTO-pyridine catalysts. Quantitative yields of epoxides from cyclic and internal alkenes were obtained with only 0.05-0.1 mol% of MTO in the presence of 10 mol% of 3-methylpyrazole.