Visible‐Light‐Induced C4‐Selective Functionalization of Pyridinium Salts with Cyclopropanols

Abstract The site‐selective C−H functionalization of heteroarenes is of considerable importance for streamlining the rapid modification of bioactive molecules. Herein, we report a general strategy for visible‐light‐induced β‐carbonyl alkylation at the C4 position of pyridines with high site selectivity using various cyclopropanols and N‐amidopyridinium salts. In this process, hydrogen‐atom transfer between the generated sulfonamidyl radicals and O−H bonds of cyclopropanols generates β‐carbonyl radicals, providing efficient access to synthetically valuable β‐pyridylated (aryl)ketones, aldehydes, and esters with broad functional‐group tolerance. In addition, the mild method serves as an effective tool for the site‐selective late‐stage functionalization of complex and medicinally relevant molecules.