Exogenous Photosensitizer‑, Metal‑, and Base-Free Visible-Light-Promoted C–H Thiolation via Reverse Hydrogen Atom Transfer

Abstract

Visible-light-driven, intramolecular C­(sp2)–H thiolation has been achieved without addition of a photosensitizer, metal catalyst, or base. This reaction induces the cyclization of thiobenzanilides to benzothiazoles. The substrate absorbs visible light, and its excited state undergoes a reverse hydrogen-atom transfer (RHAT) with 2,2,6,6-tetramethylpiperidine N-oxyl to form a sulfur radical. The addition of the sulfur radical to the benzene ring gives an aryl radical, which then rearomatizes to benzothiazole via RHAT