Synthesis of <i>meta</i>-Sulfonylpyridinesvia Copper(II)-Catalyzed Cascade Sulfonylation/Cyclization/Aromatizationof Tertiary Enamides with Sulfonylhydrazides

A copper(II)-catalyzed radical cascade reaction of <i>N</i>-propargyl enamides with sulfonyl hydrazides was developed, which provided an unprecedented method for the direct synthesis of <i>meta</i>-sulfonylpyridines in high efficiency with good functional group compatibility and simple operation. Mechanistic studies indicated that this tandem process might be composed of the radical addition, intramolecular cyclization and oxidative aromatization.