Catalysis Communications (Nov 2021)
Efficient catalytic oxidation of primary benzylic CH bonds with molecular oxygen catalyzed by cobalt porphyrins and N-hydroxyphthalimide (NHPI) in supercritical carbon dioxide
Abstract
The oxidation of benzylic CH bonds by metalloporphyrins in supercritical carbon dioxide (scCO2) has still limited. Herein, an efficient protocol of aerobic oxidation of primary benzylic CH bond by cobalt porphyrin and NHPI (N-hydroxyphthalimide) in scCO2 was established. Using toluene as model substrate, 21.6% conversion and 81.2% benzoic acid selectivity was obtained under the optimized conditions. The protocol also exhibited good tolerance towards the oxidation of various substrates with different electron property groups. Moreover, a plausible mechanism involving free radical and high-valence cobalt species was proposed.