Lei and co-workers introduced an innovative photoredox catalytic methodology combining the photocatalyst Ru(bpy)₃(PF₆)₂ 2 with a proton-reducing catalyst, Co III (dmgH)₂(4-NMe₂-C₅H₄N)Cl 6. This system operates under mildly alkaline conditions and utilizes amides 39a,b as substrates. The reaction, conducted under blue LED irradiation and using bases such as sodium glycinate/DMAP or TBAOH, yields products 40a,b with high efficiency under oxidant-free conditions, accompanied by concurrent H₂ generation (Scheme 12). This approach demonstrates excellent performance with substrates bearing either electron-donating or electron-withdrawing substituents. However, the presence of strongly electron-donating groups (e.g., OMe) or strongly electron-withdrawing groups (e.g., CF₃) on the N-aryl ring reduces reactivity, and no product formation occurs when a nitro group (R 1 = NO₂) is present. Importantly, this catalytic system is scalable, achieving gram-scale synthesis with excellent yields. The mechanism begins with the excitation of Ru This dual functionality of the catalytic system enables efficient benzothiazole synthesis alongside hydrogen gas generation, demonstrating the versatility and practicality of this photoredox approach . This advanced system highlights the synergy between photoredox and proton reduction catalysis, offering a scalable, sustainable, and efficient method for benzothiazole synthesis. Using a ruthenium photocatalyst, Gustafson et al. presented an oxidative C-H thiolation methodology for synthesizing benzothiazoles (Scheme 13). This approach utilizes thiobenzanilides 41 as substrates, Ru(bpy)₃Cl₂ 1 as a photocatalyst, sodium persulfate as an oxidant, and pyridine as a base, all under blue LED irradiation at room temperature. The proposed mechanism begins with the activation of sodium persulfate by the excited photocatalyst, leading to the formation of the sulfate radical anion (SO₄ • ⁻) and Ru³⁺. Together, these species act as potent oxidizing agents. Specifically, Ru³⁺ oxidizes the sulfur atom in thiobenzanilide A to produce the radical cation B. This species then undergoes intramolecular radical cyclization, generating intermediate C. Subsequent rearomatization of intermediate D yields the final benzothiazole product. This method provides access to 2-alkyl and 2-aryl benzothiazoles 42 with yields ranging from moderate to good, reaching up to 79% . Scheme 13. Ru(bpy)3Cl2 1 catalyzed synthesis of benzothiazoles 42.