Regioselectivity in the reductive bond cleavage of diarylalkylsulfonium salts: variation with driving force and structure of sulfuranyl radical intermediates

The product ratios are studied from the reductive cleavage of di-4-tolylethylsulfonium and di-4-tolyl-2-phenylethylsulfonium salts by a variety of one-electron reducing agents ranging in potential from -0.77 to +2.5 eV and including thermal reductants, indirect electrolyses mediated by a series of cyanoaromatics and excited singlet states. The differences between reductive cleavages of mono- and diarylsulfonium salts are direct consequences of the structures of the sulfuranyl radical intermediates and the bond dissociation energies of the alkyl and aryl bonds.