Rhodium-Catalyzed Synthesis of 2-Methylindoles via C–N Bond Cleavage of N-Allylbenzimidazole

Abstract

A rhodium-catalyzed oxidative C−H/N−H dehydrogenative [3 + 2] annulation strategy has been reported between anilines and N-allylbenzimidazole for the synthesis of 2methylindole scaffolds. An N-allylbenzimidazole has been used as a 2C synthon for the synthesis of indole, and more importantly, this transformation involves the cleavage of the thermodynamically stable C−N bond of allylamine. Detailed mechanistic studies have been performed and a key intermediate was detected in HRMS. This transformation proceeds through a cascade of C(sp 2 )−H allylation followed by intramolecular cyclization.