An efficient organic solvent-free methyltrioxorhenium-catalyzed epoxidation of alkenes with hydrogen peroxide

Methyltrioxorhenium/3-methylpyrazole has proved to be an efficient catalytic system for epoxidation of alkenes with aqueous 35% H₂O₂ in excellent yields under organic solvent-free conditions. The yields of epoxides by the organic solvent-free epoxidation are comparable to those using CH₂Cl₂ as the organic solvent. The epoxidations of simple alkenes under organic solvent-free conditions are slower than those in CH₂Cl₂, while the epoxidations of alkenols such as citronellol are faster than those in CH₂Cl₂.