Efficient Synthesis of Spirooxindole Pyrrolones by a Rhodium(III)‐Catalyzed C−H Activation/Carbene Insertion/Lossen Rearrangement Sequence

A rhodium(III)‐catalyzed domino annulation of simple olefins with diazo oxindoles to give spirooxindole pyrrolone products is described. This reaction can be formally viewed as the result of an anomalous tandem C?H activation, carbene insertion, Lossen rearrangement, and a nucleophilic addition process. The potential utility of this reaction was further demonstrated by the late‐stage diversification of drug molecules.