Rhodium(III)-Catalyzed Heteroannulations of 3-Sulfolene Derivatives through C(sp2)-H Activation: Access to Pyridine ortho-Quinodimethane Precursors

Hydroxamates derived from 3-sulfolene-3-carboxylic acid can be involved in intra- and intermolecular rhodium(III)-catalyzed heteroannulations with alkynes proceeding through C(sp(2))-H bond activation. These transformations allow for a straightforward access to diversely substituted pyridones, and to pyridines fused to a sulfolene ring after functional group transformations. Subsequent cheletropic elimination of sulfur dioxide can be achieved under microwave irradiation to generate pyridine ortho-quinodimethanes. These results demonstrate that the scope of rhodium(III)-catalyzed C(sp(2))-H functionalizations can be extended to sulfolenes, a yet unexplored class of alkenes in these latter transformations, thereby affording access to valuable classes of heterocyclic products.