Effect of solvents on the selective electrofluorination of aromatic compounds containing active methylene groups

Voltammetry and constant current electrolysis was used to study the oxidati ve fluorination of PhSCH2COOMe, PhSCH2CONH2, PhSCH2COOPh and PhCH2CN in sol vent-free Et3N.3HF and Et3N.3HF dissolved in CH3CN, THF, DME and sulfolane. Sulfolane, DME and THF containing Et3N.3HF show much lower oxidation limit s when compared to CH,CH3CN/Et3N.3HF. These compounds undergo simultaneous oxidation along with background oxidation processes. Solvent-free Et3N.3HF has a much wider anodic potential range for the oxidation of organic compou nds. Selective electrofluorination of PhSCH2COOMe and PhSCH2COOPh does not show significant solvent effects. THF and DME were found to be more efficie nt for the selective:fluorination of PhSCH2CONH2 and PhCH2CN compared to CH 3CN. (C) 1998 Elsevier Science S.A. All rights reserved.