摘要/Abstract

偕位二氟烯烃在药物设计及含氟分子构建等方面都有广泛的应用.其电化学合成研究的开展有限，主要集中于利用三氟甲酮的脱氟烯醇硅醚化反应.利用β-三氟甲基肉桂酸酯的烯丙位氢化脱氟制备偕二氟烯烃的方法简单直接，但相关报道有限.利用电化学方法，以氨气为氢源，以石墨毡为阴阳极材料，实现了一系类的β-三氟甲基肉桂酸酯电化学烯丙位氢化脱氟反应，以中等到优秀的收率获得了多种α-取代偕二氟苯乙烯类化合物.反应中氨气与石墨毡阴极的组合可以高效地抑制阴极析氢的反应，确保阴极向底物的电子转移的高选择性.循环伏安和方波伏安实验表明反应是经历分步的电子转移过程，从而实现C—H键的形成以及C—F的断裂.
关键词: 电化学, 氨气, C—F键活化, 石墨毡电极
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.
Key words: electrochemistry, ammonia, C-F bond activation, graphite felt electrode


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