Visible‐Light Photocatalytic Reduction of Sulfonium Salts as a Source of Aryl Radicals

Abstract

International audienceTriarylsulfonium salts are prompted to undergo efficient homolytic reduction by single electron transfer under mild photocatalytic conditions. The liberated aryl radical can then participate in carbon-carbon bond formation processes with allyl sulfones and activated olefins. Triarylsulfonium salts emerge as a valuable and alternative source of aryl radicals for synthesis

Substituted Hantzsch Esters as Versatile Radical Reservoirs in Photoredox Reactions

“…Therefore, we carried out model reactions between 1 and 1,1-diarylethenes 10 (Scheme 5). [14] We found that a nitro group, as well as phenol, pyridine, indole, and thiophene moieties, were unaffected by the reaction conditions, and the corresponding products (11 b-11 g) could be obtained in moderate to good yields. In addition, we evaluated substrates with acid-labile functional groups.…”

A Ni–Ir Dual Photocatalytic Liebeskind Coupling of Sulfonium Salts for the Synthesis of 2‐Benzylpyrrolidines

“…sulfonium salts in photoredox transformations remains underdeveloped. [15] We envisioned that through the combination of nickel-catalyzed cross-coupling of benzylsulfonium salts and the decarboxylative photocatalyzed transformation of Boc-protected prolines a novel synthetic approach could be developed for the synthesis of 2-benzylpyrrolidines in a one-step dual photoredox reaction.…”

Photoredox‐Catalyzed Alkenylation of Benzylsulfonium Salts

“…Indeed,v arious benzylsulfonium salts and alkenes could be coupled under visible light irradiation. It is worth mentioning that electrochemical, [9] chemical, [10] and photosensitized [11,12] formations of aryl or alkyl radicals from sulfonium salts have been well studied, while its application to organic synthesis has been limited to a-carbonyl or a-cyanosulfoniums, [10,12] triarylsulfoniums, [13] and 1-trifluoromethyldibenzothiophenium (Umemoto reagent). [14] In the presence of 2mol %o ffac-Ir(ppy) 3 as ap hotocatalyst, the reaction of 1-benzyltetrahydrothiophenium bromide (1a) with 1,1-diphenylethylene (2a)w as tested under blue LED irradiation.…”