Abstract
Epoxidation and allylic oxidation of cholesteryl acetate were studied using hydroperoxide (ROOH : R=H, ethyl, iso-propyl, tert-butyl, or cumyl) and a metal complex [Fe (acac)3 or Mo (CO)8] in benzene or acetonitrile. In the presence of the iron catalyst, formation of the epimeric C (5, 6)-epoxides predominated in the reactions with H2O2, while allylic oxidation giving C (7)-ketone, epimeric C (7)-alcohols and C (7)-alkyl peroxides was favored in the reactions with alkyl hydroperoxide, regardless of the polarity of the solvent. The stereoselective β-epoxidation was independent of the structure of ROOH, but the ratio of allylic oxidation to epoxidation was dependent on it. When the iron catalyst was replaced by the molybdenum catalyst, β-epoxidation decreased and solvent effects on the reaction were sufficiently marked to exclude allylic oxidation in the non-polar medium.
