Modular synthesis of benzimidazole-fused phenanthridines from 2-arylbenzimidazoles and o-dibromoarenes by a palladium-catalyzed cascade process.

An efficient palladium-catalyzed route for the synthesis of benzimidazole-fused phenanthridines from o-dibromoarenes and 2-arylbenzimidazoles is described. The sequentially accomplished reaction comprises intermolecular C-H arylation of 2-arylbenzimidazoles followed by an intramolecular N-arylation reaction promoted by the same Pd catalyst. This Pd-catalyzed double arylation provides a useful tool for the discovery of fluorescent materials.