| In 2001, scientists have made a great contribution for the asymmetric synthesis so that they achieved this year’s Nobel chemistry prize, which is the symbol of major achievement and high status about this field in the society and the scientific community. Since then, the research of chiral material and asymmetric methodology developed rapidly. Organic electrochemical asymmetric synthesis has gradually become the emerging research of asymmetric methodology. Organic electrochemical asymmetric synthesis is the way that the latent chiral material is changed into the corresponding enantiomerically enriched substances through the electrode process under the action of different kinds of chiral catalysts. Compared with Organic asymmetric synthesis, the electrochemical method has some advantages, such as under mild and green reaction conditions, easily to be controlled, small amount of chiral catalysts, etc.Carbonates could be the solvent and extracting agent with good performance, which could be widely used in making medicine and chemical products. To meet the large demand of carbonates, the synthesis methodologies have been improved constantly. Using the electrochemical method to active CO2 with epoxides for synthesis of the valuable cyclic carbonates can be one of the most meaningful methodologies. Not only decreasing CO2 which leads to the greenhouse effect, but also using CO2as the economic, nontoxic, cheap and abundant C1 resources to make the medicine and chemical products.Recent years, the investigation of inserting CO2 into enantiomerically pure or racemic epoxides for asymmetric synthesis of the cyclic carbonates has been reported frequently. These investigation results were based on organic asymmetric synthesis which was catalyzed by the chiral coordination complex of aluminum, magnesium, chromium and cobalt, etc. It is well known that the investigation of inserting CO2 into epoxides for asymmetric synthesis of the cyclic carbonates in the organic asymmetric synthesis field has been quite mature. But the reaction conditions needed the high temperature and high pressure, expensive and poisonous catalysts. Electrochemical asymmetric synthesis of cyclic carbonate research has not been reported so far. Electrochemical asymmetric synthesis can successfully avoid the conditions of high temperature and high pressure so that the reaction devices are simple and economic. The whole process of reaction is easy to be controlled. Therefore, styrene oxide was the mainly substrate studied in this thesis. Enantiomerically enriched cyclic-carbonates have been achieved by electrolyzing the R-styrene oxide or racemic styrene oxide with CO2.The mainly studied contents of this thesis are given as follows:(1) Electrosynthesis of R-styrene carbonate from CO2 and R-styrene oxideIn an undivided electrolytic cell with CO2 and acetonitrile (MeCN), a 316 stainless steel (Ss) as cathode and a Mg sacrificial as anode, R-styrene carbonate can be achived from CO2 and R-styrene oxide through electrosynthesis under room temperature and 0.1 MPa. The products were detected by the HPLC (Daicel Chiralcel OD-H) in quantitative analysis. The effects on the yield and ee value of styrene carbonate were investigated under different kinds of electrosynthesis conditions such as supporting electrolytes, current densities, electricity quantity, temperature, etc.Under the optimized electrosynthesis conditions, high yield and ee value could be achieved. The regioselectivity has been firstly studied by the DFT calculation. The combination of comparative electrolysis and DFT calculation proved that a negatively charged CO2 molecule, instead of CO2, inserted into the intermediate in the electrosynthesis. The investigations of the cyclic voltammgrams behaviour of CO2 and styrene oxide were carried out for us to deeply and clearly understand the reaction mechanism.(2) Electrochemical asymmetric synthesis of enantiomerically enriched styrene carbonate from CO2 and racemic styrene oxide catalyzed by CoⅡ-(R, R) (salen).Based on the investigation of electrosynthesis of R-styrene carbonate from CO2 and R-styrene oxide, using a 316 stainless steel (Ss) as cathode and a Pt as anode, electrochemical asymmetric synthesis of enantiomerically enriched styrene carbonate from CO2 and racemic styrene oxide catalyzed by CoⅡ-(R, R) (salen) has been studied. The catalytic ability and the cyclic voltammgrams behaviour of CoⅡ-(R, R) (salen) has been studied. The effects on the yield and ee value of styrene carbonate were investigated under different kinds of electrosynthesis conditions such as solvent, the dosage of the catalyst, electrode material, temperature, etc. At the same time, enantiomerically enriched styrene carbonate can also be made through the step-by-step coordination reaction of Mg2+ and CoⅡ-(R, R) (salen). Some key factors were studied and the reaction mechanism was speculated. |
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