Synthesis of pyrido[1,2-a]benzimidazoles by photo-stimulated C-N bond formation via SRN1 reactions

The photo-stimulated cyclization of 2-(2-halophenylamino)pyridines in liquid ammonia afforded pyrido[1,2-a]benzimidazoles via SRN1 mediated C-N bond forming reactions in moderate to excellent yields (58-94%). This general synthetic strategy was also extended to a 2-(2-bromophenylamino)pyrazine to give pyrazino[1,2-a]benzimidazole. Attempts to employ this reaction using N-(2-chlorophenyl)-3-isoquinolinamine, however, resulted in C-C bond formation generating 7H-indolo[2,3-c]isoquinoline.