Alkylation Reactions with Alkylsulfonium Salts

Abstract

Application of alkylsulfonium salts as alkyl transfer reagents in organic synthesis has reemerged over the past years. Numerous heteroatom- and carbon-centered nucleophiles, alkenes, arenes, alkynes, organometallic reagents, and others were readily alkylated by alkylsulfonium salts under mild conditions. The reactions feature convenience, high efficiency, readily accessible and structurally diversified alkylation reagents, good functional group tolerance, and a wide range of substrate types, allowing for facile synthesis of various useful organic molecules from the commercially available building blocks. This review summarizes the alkylation reactions using either isolated or in situ formed alkylsulfonium salts via nucleophilic substitution, transition-metal-catalyzed reactions, and photoredox processes.

Empowering boronic acids as hydroxyl synthons for aryne induced three-component coupling reactions

“…In the presence of water as the 3rd component, a ring-opening fluorination product 11 d was obtained as the major one through sulfonium intermediates under otherwise identical conditions. 16,17 Clearly, this platform reaction served as an evaluation criterion of the nucleophilic scale to aid our understanding of the nature of such boronate complexes. When employing potassium hydroxide, lithium hydroxide or cesium hydroxide monohydrate as another option, we observed a significant loss of yield, which could be possibly attributed to the decomposition caused by their strong basicity.…”

Copper-Mediated Deconstructive Ring Cleavage of Cyclic Thioethers with Boron Compounds

“…It is worthy of note that sulfonium salts can also be produced from sulfoxides (S IV ) via the Pummerer reaction . Ritter reported a seminal work on site-selective C–H functionalization by thianthrenation in 2019, making thianthrenium salts an attractive synthetic unit for functional group transformation.…”

“…The ring opening of cyclic thioethers is usually triggered by a highly electrophilic species to form sulfonium salts or zwitterionic intermediates and then followed by nucleophilic attack to break the C–S bond. Alkyl halides and their analogues such as MeI, MeOTf, etc., are conventional electrophilic reactants to prepare stable sulfonium salts in this strategy, although aryl halides are infeasible. Besides that, the substrate scope of this protocol was constrained to a small range of active alkyl halides.…”

Sulfonium Salt Reagents for the Introduction of Deuterated Alkyl Groups in Drug Discovery

“…We first hypothesized that the higher acidity of the α-CÀ H bond in alkyl-substituted salts, [48] including sulfonium, [49][50][51] quaternary phosphonium, [52] ammonium, [53,54] and pyridinium cations, [55][56][57] would facilitate deprotonation under basic conditions to form the corresponding ylides, and subsequent deuteration by D 2 O would provide α-deuterated alkyl salts [48] . In this process, the hydrolysis of the alkyl-…”