Electrochemical synthesis of cyanoacetic acid from chloroacetonitrile and carbon dioxide

The electrochemical carboxylation of chloroacetonitrile was investigated in dimethylformamide (DMF) and acetonitrile(MeCN) by cyclic voltammetry and controlled-potential electrolysis. Both direct electroreduction and mediated reduction of the halide in CO2-saturated solvents were used to achieve the electrocarboxylation process. Also the effects of cathode material and cell type (divided or undivided with dissolving anode) were examined. In DMF the electrolyses performed in the divided cell resulted in low to moderate yields of NCCH2CO2H (25-45%), independent of the electrode material and catalyst type. The process is remarkably more efficient in MeCN, in which acid yields of ca. 60% were obtained under similar conditions. Very good results were obtained in both solvents when an undivided cell with aluminum sacrificial anode was used. In this case, the acid yield increased to 73 and 93% in DMF and MeCN, respectively.