Solvent-free synthesis of alkyl and fluoroalkyl sulfonium salts from sulfides and fluoroalkyl trifluoromethanesulfonates

Abstract

A series of diaryl(fluoroalkyl)sulfonium salts were synthesized from electron-rich diaryl sulfides and fluoroalkyl trifluoromethanesulfonates under solvent-free conditions. Unlike diaryl sulfides, dialkyl and alkyl(aryl) sulfides reacted with fluoroalkyl trifluoromethanesulfonates (e.g. CF3SO3CH2CF3, CF3SO3CH2CF2H) to provide trialkyl- and aryl(dialkyl)sulfonium trifluoromethanesulfonates in good yields, wherein dialkyl- and alkyl(aryl)(fluoroalkyl)sulfonium salts were formed, respectively, and nucleophilically attacked by a second sulfide to yield the non-fluorinated sulfoniums. The SN2-type reaction could stop at the first step and exclusively afford dialkyl- and alkyl(aryl)(fluoroalkyl)sulfonium salts, which was dramatically dependent upon the structure of sulfides, the nature of fluoroalkyl trifluoromethanesulfonates, the reactant ratio, and/or the reaction temperature. This protocol allows for an efficient and convenient access to a variety of alkyl and fluoroalkyl sulfonium salts.