Chuan-Hua Lia, Gao-Qing Yuan, a, Xiao-Chen Jia, Xiu-Jun Wanga, Jian-Shan Yea and Huan-Feng Jiang, a,
a School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China
Received 23 April 2010; revised 14 June 2010; accepted 18 June 2010. Available online25 June 2010.
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 thesole 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.
Keywords: Electrosynthesis; Carbon dioxide; 1,3-Diene;Dicarboxylic acid; Adipic acid
2.3. The electrocarboxylation of 1,3-butadiene with carbon dioxide
2.4. The electroreduction of 3-hexene-1,6-dioic acid into adipic acid
2.5. Characterizations of products
3. Results and discussion
3.1. Electrosynthesis of 3-ene-1,6-dioic acids from dienes and CO2
3.2.Influence of cathode materials
3.3. Influence of electricity and CO2 pressure
3.4. The electroreduction of 3-hexene-1,6-dioic acid into adipic acid
3.5. The reaction mechanism of 1,3-butadiene and CO2
The electrochemical fixation of CO2 into unsaturated hydrocarbons has received much attention and become an interesting topic in syntheticorganic chemistry ,  and . From an environmental viewpoint, CO2 is a renewable, low cost, abundant and nontoxic C1-synthon , ,  and . The fixation and conversion of CO2 are beneficial to environment. From the viewpoint of synthetic methodology, electrochemical process is one of green, atom-economical and efficient processes because no harmful wastes are generated along withproduction of desired compounds. Especially, the carboxylic acids obtained via the electrochemical fixation of CO2 are usually important synthetic intermediates in organic synthesis and the production of polymer materials or pharmaceuticals . Up to now, many efforts have been devoted to the investigation on the electrocarboxylation of CO2 with various organic compounds including alkenes , ,,  and , alkynes  and , ketones , ,  and , halides , , , , , ,  and , imines , epoxides ,  and  and dienes , , , ,  and . It is worth noting that the electrocarboxylation of 1,3-butadiene aimed at synthesizing adipic acid ,  and , one of the most important industrial chemicals,has been one of the most topical problems in synthetic electroorganic chemistry for more than 30 years . Until now, the electrochemical reaction between CO2 and 1,3-butadiene often led to the generation of a complicated mixture containing 3-pentenoic acid, 4-pentenoic acid, 2-ethylsuccinic acid and 3-hexene-1,6-dioic acid . Therefore, it is still necessary to exploit an efficientelectrochemical route for the synthesis of 3-hexene-1,6-dioic acid from 1,3-butadiene and CO2.
Al and Mg as sacrificial anodes have been widely used in undivided cells for the electrocarboxylation process of organic compounds with CO2. Some researches showed that Al3+ or Mg2+ ions formed on the anode or added to the cell could strongly affect the processes of electrocarboxylation  and , and that...