Hantzsch Ester as a Visible-Light Photoredox Catalyst for Transition-Metal-Free Coupling of Arylhalides and Arylsulfinates.

Diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (HEH) has been utilized as a visible-light photoredox catalyst for the cross coupling of arylhalides and arylsulfinates without transition metal, sacrificial agent, and mediator. This method is compatible with various functional groups and provides diaryl sulfones in good to high yields. Mechanistic studies indicate that this reaction undergoes the stepwise light irradiation of HE- , single electron transfer (SET) in donor-acceptor complex (DAC) from *HE- to arylhalide, trapping of aryl radical with sulfinate, and SET oxidation of sulfone radical anion by HE. to sulfone by the DAC method.