Copper-catalyzed electrochemical synthesis of alkylidene lactones from carbon dioxide and 1,4-diarylbuta-1,3-diynes

The novel synthesis of alkylidene lactones from carbon dioxide with 1,4-diarylbuta-1,3-diynes via copper-catalyzed electrochemical route is described. The procedure was smoothly performed in an undivided electrochemical cell fitted with Ni cathode and Al anode, containing n-Bu4NBr–DMF electrolyte with a constant current under 4 MPa pressure of CO2. The corresponding alkylidene lactones could be obtained in moderate to good yields in the presence of catalyst CuI, while the γ-keto carboxylic acids as main products were obtained without any catalysts. A reaction mechanism was also briefly discussed.