Abstract
Tetrakis [3, 5-bis (trifluoromethyl) phenyl] borate (TFPB), a highly lipophilic fluoroaromatic borate ion which is remarkably stable under acid and oxidative conditions, was designed as an anionic phase-transfer catalyst, whose function is to transfer cationic species such as diazonium and oxonium ions in reactive form of ion pair from an aqueous (or solid) phase into a nonpolar organic phase and to promote catalytically the electrophilic reactions in two-phase systems. Some effecive examples of anionic phase-transfer catalysis (PTC) with TFPB were demonstrated in the diazo coupling, the Friedel-Crafts alkylation, the nitrosation (in situ diazo coupling), the acid-mediated hydrolysis of esters, and the redox reactions with methylviologen in liquid membrane system. Kinetic investigations of these PTC reactions clearly indicated that the enhanced reactivities of the cationic species and the specificities of the electrophilic reactions were due to the dehydration of such cationic species ion-paired with TFPB in nonpolar organic phase.
