Photoinduced cross-coupling of indoles with ICF2SO2Ph promoted by DABSO

Abstract

DABSO, typically a solid surrogate of SO₂, enables the efficient synthesis of sulfonyl compounds, such as sulfonamides and sulfones. Here, DABSO was identified as an effective electron donor compound in the coupling reaction of indoles with ICF₂SO₂Ph. Under blue light irradiation in methanol or a mixed solvent of methanol and dichloromethane, DABSO promotes selective (phenylsulfonyl)difluoromethylation at the C2–H bond of indole, delivering the corresponding products in up to 93% yield. Compared with existing methods, this approach exhibits significantly enhanced reactivity and superior chemoselectivity. In contrast, when the C2 position is substituted, the reaction in methanol preferentially occurs at the C3–H bond to afford the corresponding methyl ester. Switching to acetonitrile as the solvent allows selective introduction of a phenylthiol group at the C3–H position, yielding the products in moderate amounts.