Selective Cyclization of Arylnitrones to Indolines under External Oxidant-Free Conditions: Dual Role of Rh(III) Catalyst in the C–H Activation and Oxygen Atom Transfer

The first example of Rh­(III)-catalyzed cyclization of arylnitrones to indolines under external oxidant-free conditions is presented. An intermolecular coupling of arylnitrones with internal alkynes is made possible by the dual role of the Cp*Rh­(III) catalyst mediating both the C–H bond activation and O-atom transfer. Synthetically important and pharmacologically privileged indoline derivatives were obtained in good yields with high diastereoselectivity.