Electrochemical Allylic Hydrodefluorination Reaction Using Gaseous Ammonia as Hydrogen Source

Abstract

gem-Difluoroalkenes have wide applications in the drug designs and act as the synthon of molecules containing fluoride. The current researches on the electrochemical syntheses of gem-difluoroalkenes are limited to the silylation of enolated trifluoromethyl ketones. Herein, by using graphite felt as electrodes, the electrochemical allylic hydrodefluorination of α-trifluoromethyl cinnamates is realized using gaseous ammonia as hydrogen source, giving gem-difluorostyrenes in moderate to good yields. The usage of ammonia and graphite felt cathode is important to inhibit the cathodic hydrogen evolution, keeping the electron transfer from cathode to substrate with high selectivity. The cyclic voltammetry (CV) and square wave voltammetry (SWV) analyses support a stepwise electron transfer process to achieve the C-H bond formation and C-F bond cleavage.