Efficient electrochemical dicarboxylations of arylacetylenes with carbon dioxide using nickel as the cathode

The electrochemical dicarboxylation of arylacetylenes with carbon dioxide could be smoothly achieved in an undivided cell using Ni as the cathode and Al as the anode with n-Bu₄NBr-DMF as the supporting electrolyte, at a constant current under CO₂ pressure of 3 MPa and room temperature in the absence of additional catalysts. The corresponding aryl-maleic anhydrides and 2-arylsuccinic acids were afforded in excellent total yields (82-94%). Under anhydrous conditions, an unsaturated aryl-maleic anhydride as the main product was obtained, while the presence of H₂O would lead to the formation of saturated 2-arylsuccinic acids. The results of cyclic voltammetric experiments show that a nickel cathode itself plays the catalytic role in the reduction reaction of arylacetylenes with CO₂.