Modular Synthesis of Benzimidazole-Fused Phenanthridines from 2‑Arylbenzimidazoles and <i>o</i>‑Dibromoarenes by a Palladium-Catalyzed Cascade Process

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