Rhodium(III)-Catalyzed Redox-Neutral C-H Annulation of Arylnitrones and Alkynes for the Synthesis of Indole Derivatives

By using a nitrone as the oxidizing directing group, a mild, practical and efficient rhodium(III)-catalyzed C-H functionalization for the synthesis of indole derivatives has been developed. This reaction obviates the need for an external oxidant and shows good functional group tolerance. The employment of a sterically hindered Mes group on the carbon center of the nitrone is crucial to produce indoles in high yield.