Rhodium(III)‐Catalyzed Heteroannulations of 3‐Sulfolene Derivatives through C(sp 2 )−H Activation: Access to Pyridine ortho ‐Quinodimethane Precursors
Résumé
Hydroxamates derived from 3-sulfolene-3-carboxylic acid can be involved in intra- and intermolecular rhodium(III)-catalyzed heteroannulations with alkynes proceeding through C(sp2)−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(sp2)−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.
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