Rhodium-Catalyzed NH-Indole-Directed C–H Carbonylation with Carbon Monoxide: Synthesis of 6H-Isoindolo[2,1-a]indol-6-ones

An efficient synthesis of 6H-isoindolo[2,1-a]indol-6-ones through rhodium-catalyzed NH-indole-directed C–H carbonylation of 2-arylindoles with carbon monoxide has been developed. Preliminary mechanistic studies revealed that this reaction proceeds via N–H bond cleavage and subsequent C–H bond cleavage. Reaction monitoring via ESI-MS was used to support the formation of five-membered rhodacycle species in the catalytic cycle.