Quinizarin—an Effective Photocatalyst for Oxidation of Organic Sulfides in a Supercritical Carbon Dioxide Medium

Quinizarin has been used for the first time as a photocatalyst for the oxidation of organic compounds with molecular oxygen in supercritical carbon dioxide medium under visible-light irradiation. The choice of catalyst is justified by the availability and high efficiency of quinizarin compared to structurally related anthraquinone derivatives, namely 2-nitro-1,4-dihydroxyanthraquinone and 2,3-diamino-1,4-dihydroxyanthraquinone. Carrying out the photocatalytic process in scCO2 not only enables the efficient synthesis of sulfoxides and sulfones from the corresponding sulfides but also enhances the safety and environmental sustainability of the oxidation reaction.