Synthetic Applications of Sulfonium Salts as Aryl Radical Precursors

Abstract

The utilization of aryl radicals as open‐shelled intermediates has become an essential tool for both conventional and state‐of‐the‐art synthetic chemistry. However, the current methods for generating aryl radicals are still inefficient, greatly impeding their practical applications. Encouragingly, sulfonium salts have emerged as appealing sources of aryl radicals for a wide range of transformations aimed at creating novel chemical bonds driven by their distinctive structural attributes and chemical tendencies. This review primarily focuses on the specific reaction mechanisms underlying the cleavage of C−S bonds in sulfonium salts, leading to the generation of corresponding aryl radicals within diverse reaction conditions.

Multicomponent reactions to access S-aryl dithiocarbamates via an electron donor–acceptor complex under open-to-air conditions

“…In view of the extraordinary properties of thianthrene salts and their sensitivity to single-electron reduction, various reports described the synthesis of thianthrene salts and their application in the construction of C–C and C–heteroatom backbones catalyzed by transition-metal and photoredox catalysts to obtain a host of aryl derivatives. 33 d ,34 Very recently, the Wang, 35 Yang 36 and Wu 37 groups, respectively, developed methods that allow access to S -aryl dithiocarbamates from dibenzothiophenium salts via EDA complex photoactivation during the preparation of our manuscript (we have applied for a Chinese patent (202211493902.4) on Nov. 25 th , 2022) (Scheme 2C). Although there are many advantages, these transformations are usually carried out by UV light irradiation and pre-prepared sodium dithiocarbamate salts; substrates are mostly limited to aromatic compounds bearing electron-donating groups and secondary aliphatic amines or require inert gas protection.…”

Nucleophilic functionalization of thianthrenium salts under basic conditions

“…Sulfonium salts [1][2][3][4][5][6][7][8][9][10] have been extensively utilized as readily accessible synthetic building blocks in organic synthesis, particularly in the ipso-functionalization of C-S bonds. Of the sulfonium salts, organothianthrenium salts exhibit distinct structural properties and reactivities, thereby offering further potential in organic synthesis.…”

“…Significant advancements in the synthesis of arylthianthrenium salts have prompted a growing interest in their utilization as versatile precursors for the conversion of C-H bonds in arenes into C-C/X bonds through transition-metal-catalyzed cross-coupling processes [12][13][14][15][16][17][18][19][20]. On the other hand, sulfonium salts have emerged as appealing sources of aryl radicals for a wide range of transformations aimed at creating novel chemical bonds driven by their distinctive structural attributes and chemical tendencies (Scheme 1a) [9,[21][22][23][24][25][26]. In addition to late-stage C-H functional-Scheme 1: Synthetic application of thianthrenium salts.…”

Photoredox Ring Opening 1,2-Alkylarylation of Alkenes with Sulfonium Salts Toward Thioether-Substituted Oxindoles

“…Sulfonium salts can be treated as useful synthetic building blocks in organic synthesis, widely used in organic synthetic chemistry for the construction of various biological activity molecules and functional materials because of their stability, easy preparation, and rich reactivity. − Among the various sulfonium salts, cyclic sulfonium salts, mainly including aryl sulfonium salts, aryl thianthrenium (TT or TFT) salts, aryl dibenzothiophenium (DBT) salts, and phenoxathiinium (PXT) salts (four types), are a class of the most versatile and practical sulfonium salts, which are commonly used as electrophilic reagents in various categorys of chemical reactions . Generally, the desulfurization cross-coupling reactions of aryl sulfonium salts are more reactive than dehalogenation cross-coupling of aryl halides.…”