Electroreductive Dehalogenation of Fluorobenzenes

Article abstract of DOI:10.1021/jo00209a009

The electroreduction of 1,3-difluorobenzene and fluorobenzene on mercury cathodes in diglyme was investigated.In preparative experiments using tetrabutylammonium tetrafluoroborate as the electrolyte, fluorobenzene formed benzene and 1,3-difluorobenzene formed a mixture of fluorobenzene and benzene.When dimethylpyrrolidinium (DMP⁺) tetrafluoroborate was used, benzene was obtained from fluorobenzene but the electrode potential was less negative.In the reduction of 1,3-difluorobenzene, a similar effect of DMP⁺ on the potential was observed.In addition, conditions were found for selective defluorination to fluorobenzene.Results from preparative experiments-products and reaction potentials-and cyclic voltammetry indicate that reductive defluorination in the presence of DMP⁺ is catalytic and mercury from the electrode seems to be involved.A possible mechanism is discussed.