Oxidation mechanism of molecular oxygen over cyclohexene catalyzed by a cobalt L-glutamic acid complex

Herein, we introduce a new strategy towards the cyclohexene oxidation reaction, which is driven by molecular oxygen with a cobalt(II)/amine acid complex as the catalyst without any solvents. The as-prepared products include cyclohexene oxide, 2-cyclohexene-1-ol and 2-cyclohexene-1-one. Under optimized conditions, the oxidation of cyclohexene with molecular oxygen yields a conversion rate of 82.5%. Notably, the catalytic oxidation system has the advantages of being clean, safe and operationally simple. Our experiment indicates that the oxidation follows a radical-chain mechanism rather than a catalytic mechanism, which reveals that 2-cyclohexene-1-hydroperoxide could play a key role in the free-radical chain reaction through a complicated but necessary product analysis.