Divergent Synthesisof Polysubstituted 1,2-Dihydropyridinesand Pyridines through Manganese-Mediated Radical Cascade Cyclizationof Tertiary Enamides

A Mn(III)-mediated radical cascade cyclization of <i>N</i>-propargyl enamides with sodium sulfinates was developed. Mechanistic studies indicated that this cascade process is mainly composed of the chemoselective addition of sulfonyl radical to CC bond and the regioselective intramolecular 6-<i>endo</i>-trig cyclization. This protocol provided a powerful method for the divergent synthesis of diverse polysubstituted <i>meta</i>-sulfonylpyridines or 1,2-dihydropyridines just by varying solvent and temperature featuring good functional group compatibility and simple operation.