Access to [4,3,1]-Bridged Carbocycles via Rhodium(III)-Catalyzed C–H Activation of 2-Arylindoles and Annulation with Quinone Monoacetals

Reported herein is Rh(III)-catalyzed annulation of N-unprotected 2-arylindols with quinone monoacetals for straightforward synthesis of [4,3,1]-bridged carbocycles with exclusive C(3)-selectivity. Mechanistic studies, particularly deuterium labeling experiments, suggest that the coupling likely proceeds via twofold C-H activation with twofold migratory insertion into the enone mioeties