Ethylene Glycol: A Green Solvent for Visible Light-Promoted Aerobic Transition Metal-Free Cascade Sulfonation/Cyclization Reaction

With ethylene glycol as a green solvent, a general transition metal-free photocatalytic system using 9-mesityl-10-methylacridinium perchlorate (Acr(+)-Mes . ClO4-) as catalyst was developed for the synthesis of sulfone-containing heterocycles including thioflavones, oxindoles, and quinoline-2,4(1H,3H)-diones through the cascade sulfonation/cyclization reactions under the irradiation of blue light at room temperature.