Highly regioselective electrochemical synthesis of dioic acids from dienes and carbon dioxide

A simple and efficient electrochemical method has been developed for highly regioselective synthesis of unsaturated 1,6-dioic acids from 1,3-dienes and CO2. The electrosynthesis was successfully carried out by using a nickel cathode and an aluminum anode in an undivided cell containing n-Bu4NBr-DMF electrolyte with a constant current under 3 MPa pressure of CO2, and the sole 1,4-addition products were obtained in good to excellent yields. The plausible mechanism for electrodicarboxylation reaction of 1,3-butadiene with CO2 was discussed briefly. In addition, further research shows that 3-hexene-1,6-dioic acid could be easily converted into adipic acid via the electroreduction in the diluted H2SO4 solution.