Energy Transfer Catalysis Enabled Fluoro‐sulfonylation/‐sulfonimidation with Fluoride ^†

Comprehensive Summary

Sulfonyl and sulfonimidoyl fluorides serve as versatile SuFEx hubs for forming diverse bonds at the S(VI) center, with applications in medicinal chemistry, chemical biology, and materials science. Their state‐of‐the‐art synthesis via modular fluorosulfonylation and fluorosulfonimidation typically relies on the use of acidic fluoride salts and suffers from slow reaction kinetics, primarily due to the intermediacy of the widely adopted S(VI)‐DABCO adducts generated through redox processes. On the other hand, aryl thiophenium salts have been recognized in energy transfer catalysis for their ability to generate aryl radicals and thiophenium radical cations, a reactivity profile that has been exploited in radical coupling with ethylene. Despite this promise, their application in other radical‐radical coupling manifolds remains underexplored. Herein, we report a highly efficient radical‐radical cross‐coupling strategy for assembled fluorosulfonylation and fluorosulfonimidation with aryl thianthrenium salts using cesium fluoride under energy transfer catalysis. The substantial advances stem from the energy transfer process that generates the persistent thianthrenium radical cation and subsequently results in formation of the key highly electrophilic S(VI)‐thianthrenium species, which have enabled fast reaction kinetics with broad functional group tolerance. Mechanistic studies provided compelling evidence for the proposed pathway: the aryl radical was intercepted by TEMPO and BHT, while the pivotal S(VI)–thianthrenium intermediate was directly detected by high‐resolution mass spectrometry. The reaction can be easily scaled up and readily applied for late‐stage functionalization. To be noted, our strategy allows, for the first time, highly regioselective fluorosulfonimidation of aromatics with fluoride. The exceptional regiochemical outcome is attributed to the inherent site selectivity of the thianthrenation step, combined with the superior reaction kinetics imparted by the highly reactive S(VI)‐thianthrenium intermediates. Both the resulting sulfonyl fluorides and sulfonimidoyl fluorides undergo SuFEx reactions smoothly under mild conditions, providing rapid access to complex molecules with diverse S(VI)‐functional groups.