Photocatalyzed synthesis of unsymmetrical ureas via the oxidative decarboxylation of oxamic acids with PANI-g-C3N4-TiO2 composite under visible light

[Display omitted] •PANI−g-C3N4−TiO2 composite-catalyzed the radical synthesis of unsymmetrical ureas under visible light is described.•The semiconductor composite is readily prepared and cost-effective.•The reaction conditions are mild, green, and the yields are satisfactory.•The catalyst shows good stability and photocatalytic performance, and can be reused for several runs. The synthesis of unsymmetrical ureas via the photocatalyzed oxidative decarboxylation of oxamic acids has been developed. The carbamoyl radicals were generated from oxamic acids in the presence of a hypervalent iodine reagent and the PANI(Polyaniline)-g-C3N4-TiO2 composite under visible light irradiation. The radicals were converted in situ into the corresponding isocyanates, which were then trapped by amines to afford the corresponding products in moderate to good yields. This protocol avoided the direct use of environmentally unfriendly isocyanates and a series of substrates were tolerated. Moreover, the photocatalyst could be readily recovered by simple filtration and be reused for several runs with only a slight decrease in the catalytic activity.