The first Ru-catalyzed synthesis of benzothiazoles via photooxidative decarboxylation of α-keto acids was reported in 2014 , demonstrating the synthesis of a single example, 2phenylbenzothiazole (Scheme 6). This approach was further improved in 2020 with the discovery of a decarboxylative cross-coupling reaction between α-keto acids and 2-aminothiophenols to produce benzothiazoles 31 under blue LED irradiation without the use of any photocatalyst or metal, and at room temperature (Scheme 6) . The mechanistic pathway for this improved protocol involves the initial formation of an electron donor-acceptor (EDA) complex between the starting materials. Upon irradiation, the EDA complex generates intermediate A, which is subsequently converted into imine B. Reaction of intermediate B with H2O2 forms radical C, which undergoes decarboxylation to yield intermediate D. A subsequent 1,5-hydrogen atom transfer (HAT) produces radical intermediate E, which is then converted to F by interaction with the hydrogen superoxide radical (HOO˙). Finally, hetero-radical coupling at intermediate F results in the formation of the desired benzothiazole 31 (R 1 = Ph; R 2 = H).