Electrolytic partial fluorination of organic compounds. 31. Regioselectiveanodic fluorination of 2-quinolyl and 4-(7-trifluoromethyl)quinolyl sulfides and the factors affecting its optimization

Electrochemical fluorination of 2-quinolyl and 4-(7-trifluoromethyl)quinoly l sulfides bearing an electron-withdrawing group at the position alpha to t he sulfur atom was studied. Fluorination was successfully carried out using Et4NE . nHF (n = 3, 4) and Et3N . 3HF as a supporting electrolyte and a fl uoride ion source in dimethoxyethane in a divided cell to provide the corre sponding alpha-fluorinated sulfides in good yields. A trifluoromethyl group positioned on the quinoline ring significantly enhanced anodic alpha-fluor ination. 4-(Methylthio)-7-(trifluoromethyl)quinoline was also found to unde rgo anodic fluorination efficiently. Solvent effects of various donor numbe rs were also established.