Over the last two decades, radical chemistry, particularly photoredox catalysis, has emerged as a prominent and versatile approach for C-H functionalization. Among its many applications, direct C(sp²)-H activation followed by intramolecular C-S bond formation has been extensively investigated for the synthesis of 2-substituted 1,3-benzothiazoles. A groundbreaking study by Peñéñory and coworkers in 2009 demonstrated the cyclization of thiobenzanilides 35 to form 2-substituted 1,3benzothiazoles 36, using a stoichiometric amount of p-chloranil (CA) 14 under UV irradiation (365 nm) from a medium-pressure Hg lamp at 80 °C in non-polar solvents such as toluene or 1,2dichloroethane (Scheme 10) . The proposed mechanism begins with the generation of tripletstate p-chloranil (³CA) under UV light, which acts as a hydrogen atom acceptor in non-polar solvents. This process produces a sulfur-centered radical from the substrate, which undergoes intramolecular cyclization and subsequent re-aromatization to yield the benzothiazole, with yields ranging from low to excellent. Specifically, the mechanism involves the formation of ³CA 14, followed by HAT from Nphenylbenzothioamide to ³CA, generating the thiyl radical A and the hydroquinone radical CAH˙ (Scheme 10, pathway a). Radical A adds intramolecularly to the aromatic ring, forming a cyclohexadienyl radical B, which undergoes a second HAT to CAH˙ to furnish benzothiazole 36 (R 1 = H, R 2 = Ph). Alternatively, in polar solvents, an electron transfer (ET) mechanism is proposed (Scheme 10, pathway b). Energy transfer from N-phenylbenzothioamide to ³CA forms the radical cation of thiobenzamide (C⁺˙) and the radical anion CA⁻˙. Subsequent deprotonation yields intermediate C and CAH˙, while hydrogen transfer produces sulfur-centered cation D. Cation D undergoes intramolecular electrophilic addition to the phenyl ring, followed by deprotonation, to produce benzothiazole 36 (R 1 = H, R 2 = Ph). The experimental data suggest that the reaction mechanism is highly solventdependent. In non-polar solvents such as benzene or toluene, HAT (pathway a) is the dominant process, whereas electron transfer (pathway b) is favored in polar solvents such as MeCN. Interestingly, both mechanisms appear operative in 1,2-dichloroethane. These findings highlight the dual functionality of CA 14 as a hydrogen atom acceptor in non-polar media and as an electron oxidant in polar environments. Moreover, HAT (pathway a) was determined to be more efficient for the synthesis of benzothiazoles 36. Scheme 10. p-Chloranil 14 catalyzed synthesis of benzothiazoles 36.