A novel photoaddition of 2-phenylbenzimidazole

Article abstract of DOI:10.1002/jhet.5570330405

Irradiation of 2-phenylbenzimidazole (3) in the presence of methyl acrylate (20 equivalents) using a medium pressure mercury lamp gives methyl 2-(2-phenylbenzimidazol-1-yl)propionate (4) (75%) whose structure has been confirmed by an X-ray analysis. A similar reaction using acrylonitrile gave only a low yield (1%) of the corresponding propionitrile derivative 5. A mechanism involving photoexcitation of 2-phenylbenzimidazole (3) followed by sequential single electron transfer, proton transfer and radical coupling is proposed to account for the formation of the novel photoadducts 4 and 5.