An improved methyltrioxorhenium-catalyzed epoxidation of alkenes with hydrogen peroxide

Methyltrioxorhenium (MTO)-catalyzed epoxidation of alkenes with H2O2 has been significantly improved by using 3-methylpyrazole as an additive. A system consisting of 35% H2O2 and MTO-3-methylpyrazole in CH2Cl2 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.