Visible-Light-Induced Remote C(sp3)-H Pyridylation of Sulfonamides and Carboxamides.

Visible-light-induced site-selective C(sp3)-H pyridylation of amides has been accomplished using N-amidopyridinium salts. The N-centered radicals generated by the single-electron reduction of N-amidopyridinium substrates undergo 1,5-hydrogen atom transfer to form alkyl radical intermediates. Excellent C4-selectivity in radical trapping with pyridinium salts is observed for the alkyl radicals to provide δ-pyridyl sulfonamides and γ-pyridyl carboxamides. The utility is demonstrated by offering a practical approach for the late-stage functionalization of complex amide derivatives.