Visible-Light-Driven Oxidation of Benzylic C—H Bonds Enabled by Anthraquinone in Water

An efficient photochemical protocol for the oxidation of alkylarenes to ketones was developed using anthraquinone (AQ) as a organic small molecule photocatalysts, O2 as an oxidant and water as green solvent.The main feature of this method is that visible light, molecular oxygen and water are low-cost, abundance and eco-friendliness in green chemistry.Moreover, the system shows a broad substrate scope and good functional-group tolerance, which can also easily be scaled-up to gram scale.A series of control experiments was conducted to study the influence of superoxide radicals on the reaction, and a reasonable catalytic cycle mechanism was proposed.The mechanism studies revealed that AQ absorbed the light and served as a photosensitizer to promote the transformation of O2 to the highly reactive 2 O -via single electron transfer (SET) process, which then oxidized alkylarenes to ketones.