Aerobic Benzylic C(sp3)–H Bond Oxygenations Catalyzed by NBS under Visible Light Irradiation

An efficient photocatalytic oxidation of benzylic C(sp³)-H bonds to ketones, esters, and amides has been developed using NBS as a metal-free photocatalyst and O₂ as an oxidant. A variety of synthetically and biologically valuable compounds are assembled in moderate to excellent yields. The synthetic utility of this approach has been demonstrated by gram-scale experiments. A possible free radical mechanism was proposed to rationalize the reaction procedure.