Visible-light-induced <i>meta</i>-selective sulfonylation of pyridine <i>via</i> an EDA complex

Pyridine is a versatile structural unit found in a broad spectrum of pharmaceuticals, agrochemicals, and materials. Achieving selective <i>meta</i>-functionalization under mild conditions remains challenging due to its inherent electronic properties. In this work, we accomplished a photoinduced method for <i>meta</i>-selective sulfonylation of pyridines, facilitated by an electron donor-acceptor (EDA) complex between iodide ions and sulfonyl chlorides. The reaction proceeds <i>via</i> an oxazino-pyridine intermediate, with sulfonyl chloride acting as the sulfonyl radical precursor. This protocol stands out for its mild, photocatalyst-free conditions, high C5-selectivity, and good scalability, offering a promising approach for the synthesis of <i>meta</i>-sulfonylated pyridines.