An easy one-step photocatalytic synthesis of 1-aryl-2-alkylbenzimidazoles by platinum loaded TiO2 nanoparticles under UV and solar light

One-pot synthesis of disubstituted benzimidazoles from N-substituted 2-nitroanilines or 1,2-diamines with 3-12 nm-sized platinum particles loaded on the TiO₂ using solar and UV-A light is described. 1-Aryl-2-alkylbenzimidazoles from 2-nitrodiphenylamines are formed by combined redox photocatalytic reaction, condensation and catalytic dehydrogenation on Pt-TiO₂. In case of diamines, this reaction is proceeded by Pt-TiO₂ assisted photocatalytic oxidation of an alcohol and a catalytic dehydrogenation of the intermediate on the surface of platinum nanoparticles. In both cases product formation was achieved by tandem photocatalytic and catalytic reactions on Pt-TiO₂.