Lang, Li, and co-workers developed a visible-light-driven C-H thiolation method that eliminates the need for photosensitizers, metal catalysts, or bases (Scheme 14). This innovative procedure involves the intramolecular cyclization of thiobenzanilides 43 via a reverse Hydrogen-Atom Transfer (RHAT) mechanism, employing TEMPO (2,2,6,6-tetramethylpiperidine N-oxide) as a mediator. Upon absorption of a photon, the substrate 43 (R 1 =H, R 2 =Ph) is excited to 43*. The excited state undergoes a reversible HAT process with TEMPO, forming a thiyl radical A and TEMPOH. Radical A can be trapped by TEMPO to create adduct B, which then undergoes homolytic cleavage, regenerating A and TEMPO. The S-O bond relatively weak dissociation energy facilitates this step. The thiyl radical A undergoes a 1,5-homolytic radical cyclization to generate aryl radical C. The final benzothiazole product 44 (R 1 =H, R 2 =Ph) is obtained via a photomediated RHAT process between the activated radical C* and TEMPO. This method achieves high efficiency, affording benzothiazoles 44 with electron-rich, -neutral, and -withdrawing groups in good to excellent yields, reaching up to 95%. Scheme 14. Exogenous photosensitizer-, metal-, and base-free synthesis of benzothiazoles 44.