Rh(III)-Catalyzed Synthesis of Isocoumarins via C–H Activation of Phenacyl Phosphoniums with Iodonium Ylides

Abstract A phosphonium-assisted C–H cyclization with iodonium ylides has been developed under redox-neutral rhodium(III) catalysis, offering a wide variety of valuable isocoumarins in moderate to good yields. This transformation proceeds through C–H activation, carbene insertion, and nucleophilic addition processes. The reaction occurs under a low catalyst loading in a short reaction time and does not require an oxidant.