可见光诱导氧掺杂氮化碳催化苄基碳氧化合成酮

Aryl ketone scaffolds are widely found in pharmaceuticals and functional materials, making the development of efficient and green synthetic methods highly significant.Recently, visible light-mediated direct oxidation of benzylic C—H bonds in readily available alkylarenes has provided a novel approach to the green synthesis of aryl ketones.In this paper, oxygen-doped graphitic carbon nitride(O-g-C_3N4) was prepared using melamine as the precursor via high-temperature calcination, thermal exfoliation and oxidation.At room temperature, diphenylmethane(Ⅰa) was used as a model substrate and O-g-C_3N4 as the photocatalyst to systematically investigate the effects of solvent, catalyst loading, reaction time, light source, and reaction temperature on the yield of benzophenone(Ⅱa).The optimized reaction system was identified as follows: CH_3CN/H_2O(3 mL/3 mL) as solvent, 15 mg of O-g-C_3N4,24 h reaction time, room temperature, purple light irradiation, and an oxygen atmosphere.Under the optimized conditions, a broad range of alkylarenes were oxidized to afford 19 aromatic ketones in isolated yields ranging from 31% to 96%.The structures of all products were identified by ~1HNMR,13CNMR,and MS,and were consistent with the target compounds.The results demonstrate that this reaction system exhibits good substrate tolerance towards arenes and heteroarenes.Control experiments suggest that the oxidation of benzylic carbons proceeds via a radical-mediated single-electron transfer mechanism.Moreover, the catalyst could be reused for five cycles without significant loss of activity, demonstrating the excellent stability and practical applicability of O-g-C_3N4.