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.

In the past decades, CÀH oxidative olefination of indole at C-2, C-3, C-4 and C-7 positions was well addressed. We report here a rhodium-catalyzed NH-indole-directed ortho CÀH bond olefination of 2arylindoles. This cross-dehydrogenative-coupling proved to be broad in substrate scope, tolerating a variety of functional groups. The synthesis of 6H-isoindolo[2,1-a]indoles via rhodium-catalyzed ortho CÀH olefination and subsequent intramolecular aza-Michael reaction of 2-arylindoles was also demonstrated.

Two facile methods for the preparation of 6H-isoindolo[2,1-α]indol-6-ones were developed. In the first protocol, 6H-isoindolo[2,1-α]indol-6-ones were prepared from 2-(2-iodophenyl)-1Hindoles via palladium-catalyzed intramolecular aminocarbonylation. The second involves intermolecular carbonylation of indoles with iodobenzenes followed by intramolecular crossdehydrogenative-coupling.2015 Elsevier Ltd. All rights reserved.

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