Visible-Light-Induced Pyridylation of Remote C(sp3 )-H Bonds by Radical Translocation of N-Alkoxypyridinium Salts

Abstract

Metal-free, visible-light-induced site-selective heteroarylation of remote C(sp³ )-H bonds has been accomplished through the design of N-alkoxyheteroarenium salts serving as both alkoxy radical precursors and heteroaryl sources. The transient alkoxy radical can be generated by the single-electron reduction of an N-alkoxypyridinium substrate by a photoexcited quinolinone catalyst. Subsequent radical translocation of the alkoxy radical forms a nucleophilic alkyl radical intermediate, which undergoes addition to the substrate to achieve remote C(sp³ )-H heteroarylation. This cascade strategy provides a powerful platform for remote C(sp³ )-H heteroarylation in a controllable and selective manner and is well suited for late-stage functionalization of complex bioactive molecules.

Keywords: C−H activation; heterocycles; photochemistry; radicals; reaction mechanisms.