Effects of ion and protic solvent on nucleophilic aromatic substitution (SNAr) reactions

Abstract

We investigate the mechanism of SNAr fluorination reactions under the influence of protic solvents and ions. We find that counterion or protic solvent alone retards the SNAr reactions, but together they may promote the reaction. In this mechanism, the protic solvent acts on the counterion as a Lewis base, and the nucleophile reacts as an ion pair. We also show that an anion (mesylate) may exhibit catalytic effects, suggesting the role of ionic liquids for accelerating the SNAr reactions.