Sulfoxonium-Ylide-Directed C-H Activation and Tandem (4 + 1) Annulation.

Rh(III)-catalyzed C-H activation and cyclization of sulfoxonium ylide with acrylates leads to an efficient synthesis of indanone derivatives. The reaction proceeds under mild and external metal-oxidant-free conditions. The sulfoxonium ylide acts as a traceless directing group as well as an internal oxidant. (4 + 1) Annulation after C-H activation leads to the formation of a carbocyclic ring, and the byproduct obtained is DMSO, which can be easily separated.