A visible‐light‐promoted synthesis of quinoxalin‐2(1H)‐ones has been developed using 9‐mesityl‐10‐methylacridinium perchlorate as an organo‐photocatalyst. The atmosphere‐controlled method (Ar/air) enabled the selective synthesis of hydroxyl‐ and acyl‐containing quinoxalin‐2(1H)‐ones under mild reaction conditions without the use of any metal catalysts or toxic reagents. A fluorescent labelling experiment showed that hydroxyl‐containing quinoxalin‐2(1H)‐ones may have utility in various biological applications as potent fluorophores.

Biaryls were synthesized via a novel visible-light-promoted Gomberg−Bachmann reaction that does not require a photosensitizer or any metal reagents. The formation of an electron donor−acceptor complex between aryl diazonium salts and pyridine allows, under visible-light irradiation, the synthesis of biaryls in moderate-to-high yields.

An efficient visible-light-induced a-oxidation of N-substituted tetrahydroisoquinolines to dihydroisoquinolones has been developed using eosin Y as an organo-photocatalyst and oxygen as a green oxidant. The reactions were carried out under mild reaction conditions; the desired dihydroisoquinolones were obtained in up to 96% yield at room temperature under oxygen atmosphere. This transformation provides a convenient route to dihydroisoquinolones with a wide range of substrates.

The oxidative cleavage reaction of the C–S bond using singlet oxygen is challenging because of its uncontrollable nature. We have developed a novel method for the singlet-oxygen-mediated selective C–S bond cleavage reaction using silver­(II)–ligand complexes. Visible-light-induced silver catalysis enables the controlled oxidative cleavage of benzyl thiols to afford carbonyl compounds, such as aldehydes or ketones, which are important synthetic components.

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