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 the Rh­(III)-catalyzed annulation of N-unprotected 2-arylindoles with quinone monoacetals for the 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 two-fold C–H activation with two-fold migratory insertion into the enone moieties.