Electrochemical radiofluorination:: Labeling of benzene with [18F]fluoride by nucleophilic substitution

F-18-labeling of aromatic compounds normally is achieved by electrophilic substitution. In that case [F-18]fluoride cannot be applied although it is produced very efficiently at medical cyclotrons. By the use of electrochemical methods, however, benzene can be oxidized and thus, the electron density is reduced in a way that nucleophilic attack of [F-18]fluoride occurs. For the first time benzene was shown to be labeled with [F-18]fluoride after being electrochemically oxidized in a 2 ml electrolysis cell with 0.033M Et3N.3BF and 0.066M Et3N.HCl in CH3CN and benzene in various concentrations. After 50 Coulombs (60-90 min) maximum of labeling was reached. With the highest concentration of aromatic compound (1.0M) the radiochemical yields were 16+/-9% with specific activities up to 27 GBq/mmol.