Catalytic oxidation of cycloolefins over Co(cyclam)-functionalized SBA-15 material with H2O2

Cobalt in the form of a Co(III) complex was successfully anchored on a cyclam-tethered SBA-15, which was synthesized from a chemical modification of chloropropyl-functionalized SBA-15 and proved to be a selective catalyst for the allylic oxidation of cycloolefins, such as cyclopentene, cyclohexene, and cycloheptene with hydrogen peroxide. The Co(III)-SBA-15 showed high selectivity for the corresponding allylic hydroperoxides, which exceeded 50% after a 12-h reaction time. We conclude that the cobalt species underwent reversible redox cycles, and the formation of cobalt hydroperoxo species derived from the activation of the Co(III) complex with H2O2 was attributed to the high selectivity for hydroperoxides as major products. The reversible redox cycle between the Co(III) and Co(II) couple during the oxidation of cycloolefins was supported by a cyclic voltammetry analysis.