Photoredox‐Catalyzed Allenyl Radical Addition to SO ₂ for Allenyl Sulfones †

Comprehensive Summary Allenyl sulfones represent highly valuable scaffolds in synthetic chemistry, yet general and efficient strategies for their construction remain underdeveloped. While significant progress has been made in the coupling of alkyl or aryl radicals with SO 2 for sulfone synthesis, the corresponding coupling involving allenyl radicals has remained an unsolved challenge. Herein, we report a photoredox‐catalyzed difluoromethylation/SO 2 incorporation/polyfluoroarylation cascade of 1,3‐enynes. This strategy employs CF 2 HSO 2 Na as a novel bifunctional reagent that serves as a combined source of the CF 2 H radical and SO 2 , together with polyfluoroarenes as terminating agents via C–F bond cleavage, enabling direct and efficient access to CF 2 H‐substituted allenyl sulfones. The fluoroalkyl radical scope can be further extended to trifluoromethyl, monofluoromethyl, and perfluorobutyl groups, and the electrophilic partners can also be diversified to include alkyl halides. Furthermore, propargylic carboxylic acid derivatives also underwent smooth decarboxylation followed by sequential allenyl radical polyfluoroarylation, further demonstrating the versatility and broad applicability of our reaction system. To the best of our knowledge, this work constitutes the first addition of an allenyl radical to SO 2 , overcoming the inherent reversibility and thermodynamic unfavorability of addition process through rapid downstream conversion of the transient allenylsulfonyl radical. Mechanistic studies, supported by both experimental observations and theoretical analysis, point to a radical‐polar crossover mechanism and identify the S N Ar step as rate‐determining. This method opens new avenues for SO 2 utilization in radical chemistry.