Photocatalytic Proton-Coupled Electron Transfer-Enabled Radical Decarboxylative Polyfluoroarylsulfonylation of Carboxylic Acids

Abstract

Here, we report a visible-light-driven, organophotocatalytic radical decarboxylative polyfluoroarylsulfonylation of carboxylic acids enabled by a proton-coupled electron transfer (PCET) mechanism. This protocol leverages Na2S2O4 as an inexpensive sulfur dioxide radical anion (SO2̇–) source, which engages in radical–radical anion cross-coupling with in situ generated alkyl radicals from carboxylic acids, followed by SNAr with polyfluoroarenes. The reaction exhibits broad substrate scope, accommodating primary, secondary, tertiary, and allylic carboxylic acids, as well as diverse polyfluoroarenes, with excellent functional group tolerance. Late-stage functionalization of drug molecules and natural products, along with scale-up synthesis, underscores the synthetic utility of this method. Mechanistic studies, including radical trapping, cyclopropane ring-opening, allylic radical isomerization, and sulfinate intermediate identification, support a PCET-initiated radical pathway.