Bi4O5Br2 catalyzed selective oxidative of C=C double bonds to ketones with molecular oxygen under visible-light irradiation

Ketones plays important role in pharmaceuticals, food additives, and organic synthesis intermediates. Selective oxidation cleavage of olefins under efficient, green methods are important for the synthesis of ketones. Both homogeneous and heterogeneous catalysis are used in this reaction. Homogeneous catalyst is difficult to recover and separate, which is not meet the requirements of green chemistry. Compared with homogeneous catalyst, heterogeneous catalyst can solve these adverse factors. Herein, we used a bismuth-rich Bi4O5Br2 obtained by microwave method as a heterogeneous photocatalyst, water/dioxane (3 : 1, v/v) as the solvent, molecular oxygen as the oxygen source, various ketones were obtained in moderate to good yields under visible-light irradiation. The catalyst can be used for 4 times and without a significant reduction in activity. Through the EPR experiment and mechanism verification experiments, superoxide radicals or photogenerated electrons and holes played important roles in the oxidative cleavage of C=C double bonds.