Photocatalytic oxidation of benzene to phenol using dioxygen as an oxygen source and water as an electron source in the presence of a cobalt catalyst.

Photocatalytic hydroxylation of benzene to phenol by dioxygen (O2 ) occurs under visible light irradiation of an O2 -saturated acetonitrile solution containing [RuII (Me2 phen)3 ]2+ as a photocatalyst, [CoIII (Cp*)(bpy)(H2 O)]2+ as an efficient catalyst for both the water oxidation and benzene hydroxylation reactions, and water as an electron source in the presence of Sc(NO3 )3 . The present study reports the first example of photocatalytic hydroxylation of benzene with O2 and H2 O, both of which are the most green reagents, under visible light irradiation to afford a high turnover number ( e.g. , >500). Mechanistic studies revealed that the photocatalytic reduction of O2 to H2 O2 is the rate-determining step, followed by efficient catalytic hydroxylation of benzene to phenol with H2 O2 , paving a new way for the photocatalytic oxygenation of substrates by O2 and water.