Radical C−C Bond Formation using Sulfonium Salts and Light

Abstract

Sulfonium salts are playing an increasingly significant role in contemporary organic synthesis.I n particular,t he generation of radicalsf rom sulfonium salts is af undamental process in Naturea nd has been the subject of investigation for over 50 years. However, general synthetic methods that use sulfonium salts as radical precursors are rare.T he advent of photoredox catalysis hast riggered an upsurge of interesti nt he radical chemistry of sulfonium salts and this review surveys recent applications of aryl-and alkylsulfonium saltsi nl ight-mediated, radical C À C bond formation. 1I ntroduction 2E arly Reports on the Photochemistry of Sulfonium Salts 3S ulfonium Salts in C À CB ond Formation 3.1 TheV alue of Arylsulfonium Salts in Light-Mediated C À CB ondF ormation 3.2 TheP reparation of BenzylsulfoniumSalts and their Reactivity in Light-Mediated C À CB ond Formation 3.3 TheD irect Preparation of Arylsulfonium Salts for Light-Mediated C À CB ond Formation 4C onclusion

Synthesis of Cycloheptatrienes, Oxepines, Thiepines, and Silepines: A Comparison between Brønsted Acid and Au‐Catalysis

“…promotes the clean formation of benzothiophenium salt 11a through a 5‐ endo ‐dig cyclization. Instead of the arene, it is the sulfur atom the one that plays the role of the nucleophile and attacks the transient vinyl carbocation . The structure of 11a was confirmed by X‐ray analysis (Figure ).…”

Studies on the Synthesis of Perfluoroaryl Sulfides and their Application in Desulfurative Nickel-Catalyzed Reductive Cross-Coupling

“…The concept of C−S bond activation has also been exploited for the functionalization of C−H /C−X bonds (X = halide). Organosulfur reagents like thianthrene sulfoxide, [60][61][62][63] dibenzothiophene S-oxide, [64][65] xanthate [66][67] , thiocarbamate, [68][69] and tetrafluoropyridinyl disulfide [48][49][50][51][52] can be added to arenes or organohalides to obtain sulfonium salts or sulfides, which contain a weak C−S bond that can be easily replaced in a reductive C−S bond cleavage step. Despite the success of the above methods, which are all based on C−S bond activation, one still lacks a generally applicable tool for the efficient conversion of mercapto groups into other functionalities.…”

Generation of non-stabilized alkyl radicals from thianthrenium salts for C–B and C–C bond formation

“…In a synthetic chemistry setting, general methods that utilize sulfonium salts as radical precursors have been investigated over the past decades [16][17][18] . Recently, the emerging field of photoredox catalysis has also offered new possibilities for these single electron transfer (SET)-induced transformations under mild conditions [19][20][21] . Ritter and coworkers just reported the site-selective C-H functionalization of arenes to build S-(aryl) thianthrenium salts, which could be utilized in radical-involved transformations by photoredox catalysis (Fig.…”