A Rh(III)‐catalyzed 4 + 2 annulation of 2‐aryl imidazoles/benzimidazoles with α‐diazocarbonyl compounds has been developed for the synthesis of π‐conjugated imidazo/benzimidazo2,1‐ a isoquinolinones systems. This method exhibits a broad substrate scope and excellent functional group tolerance, enabling the access of diverse tricyclic and tetracyclic π‐extended imidazole and benzimidazole derivatives. Mechanistic studies and control experiment revealed that the reaction proceeds via imidazole‐directed ortho C(sp2)–H activation, followed by carbene C–H insertion and subsequent intramolecular amidation to furnish the 4 + 2 annulation product. An optimized scaffold demonstrated potential relevance in materials and medicinal chemistry.
Pawar et al. (Fri,) studied this question.