CP-STAR-MOO2CL-CATALYZED EPOXIDATION OF OLEFINS BY ALKYL HYDROPEROXIDES

Irradiation of Cp*Mo(CO)3Cl in the presence of oxygen affords the Mo(VI) oxo complex Cp*MoO2Cl (5). Complex 5 was found to act as a catalyst of the reaction of alkyl hydroperoxides and olefins to yield the corresponding epoxides and alcohols. No oxidation of the pentamethylcyclopentadienyl ligand of 5 was observed under the conditions of the epoxidation reaction. The characteristics of the epoxidation reaction catalyzed by 5 is similar to that of other Mo(VI) catalysts. In the absence of added olefins, 5 reacts with alkyl hydroperoxides to yield the peroxo complex Cp*Mo(O2)OCl (6). The peroxo complex 6 is inert to reaction with olefins, thus ruling out 6 as the intermediate responsible for olefin oxidation in this system. An investigation of the relative rate of epoxidation of cyclohexene, 1-methylcyclohexene, and 1,2-dimethylcyclohexene with various alkyl hydroperoxides demonstrates that the relative rates depend on the structure of the alkyl group of the alkyl hydroperoxide. This result demonstrates that the alkyl hydroperoxide is incorporated in the transition state for the oxygen-transfer step of the reaction.