Copper‐Catalyzed Synthesis of Benzimidazole‐Fused Phenanthridines and Quinolines

A modular synthetic method for benzimidazole‐fused phenanthridines, benzo[4,5]imidazo[1,2‐ f ]phenanthridines, has been developed via copper‐catalyzed sequential C(sp 2 )─C and C(sp 2 )─N bond formations between 2‐(2‐bromoaryl)benzimidazoles and 2‐bromoarylboronic acids under microwave irradiation. The construction of benzimidazole‐fused quinolines, benzo[4,5]imidazo[1,2‐ a ]quinolines, is also achieved by treating 2‐(2‐bromovinyl)benzimidazoles with 2‐bromophenylboronic acid under similar copper catalysis. A control experiment indicates the involvement of competing copper‐catalyzed Suzuki–Miyaura‐type C─C and Ullmann‐type C─N coupling pathways.