Among the numerous studies reporting the photochemical synthesis of benzothiazoles from aminothiophenols and aldehydes, only one has been conducted under anaerobic conditions . In this study, a one-pot coupling reaction catalyzed by eosin Y 18 was performed using tert-butyl hydroperoxide (TBHP) as the oxidant in acetonitrile under blue LED irradiation (Scheme 1) . Although the mechanism remains incompletely elucidated, a plausible pathway has been proposed to rationalize the formation of the desired products The use of a visible-light-absorbing intermediate as a photosensitizer simplifies and enhances the sustainability of chemical processes by eliminating the need for additional chemical additives. This strategy has been effectively employed in several studies (Scheme 2) . In the synthesis of benzothiazoles from 2-aminothiophenol and aldehydes, the formation of a photosensitizing disulfide intermediate was proposed and confirmed through detailed mechanistic investigations. Yan and coworkers successfully demonstrated the broad applicability of this method, employing a wide range of aromatic, heteroaromatic, and aliphatic aldehydes to synthesize benzothiazoles 26 under blue LED irradiation in ethyl acetate (Scheme 2) . Subsequently, You and Cho showed that a similar scope of benzothiazole derivatives could be synthesized in water using white LED irradiation (Scheme 2) . These reactions achieved good to excellent yields, irrespective of the electron density or substituent positions on the aldehydes. The mechanism begins with the reaction of benzaldehyde and 2-aminothiophenol to generate intermediates A and B. Under photoirradiation, B, which is in equilibrium with the starting materials, acts as a photosensitizer. It facilitates the production of reactive oxygen species, including superoxide anion (O2 •-) and singlet oxygen ( 1 O2), via SET and energy transfer pathways, respectively. In the electron transfer pathway, photoexcited B* donates an electron to molecular oxygen (O2), generating O2 •-and the radical cation B •+ . The latter undergoes reduction, regenerating B through the oxidation of A to A •+ . The radical cation A •+ is then deprotonated and reacts with O2 •-, resulting in the formation of benzothiazole 26 (R 1 = H; R 2 = Ph) along with hydrogen peroxide (H2O2). In the energy transfer pathway, 1 O2 undergoes insertion at the C-H bond at the 2-position of A, releasing H2O2 and forming 26 (R 1 = H; R 2 = Ph). The production of H2O2 during the reaction was confirmed using a peroxide indicator. Notably, even in the absence of light irradiation, the reaction still proceeds, albeit with low yields of 9-13%. Scheme 2. External photocatalyst-free synthesis of benzothiazoles 26.