Regiospecific base-catalyzed hydrogen exchange of triarylsulfonium salts

Solvent isotope labelling method has been used to show that the hydrocarbon products commonly observed in the reaction of triarylsulfonium salts with a number of alkoxide nucleophiles are derived via the radical intermediate rather than the corresponding anions. The results of the determination of the extent and scope of the base-catalyzed hydrogen exchange of the triarylsulfonium salts with the protic solvent medium are reported. No clear explanation for the observed regiospecificity of the hydrogen exchange in the salts is readily available. The enhanced thermodynamic acidity of the ortho hydrogen due to the inductive effect of the electron-withdrawing sulfonium and the dipole stabilization of the corresponding carbanionic species are suggested as explanations for the regiospecific deprotonation of the ortho hydrogen in the triarylsulfonium salts