【作者】 肖艳；

【导师】 陆嘉星；

【作者基本信息】 华东师范大学 ， 物理化学， 2014， 硕士

【摘要】 2001年,科学家在催化不对称合成方面做出重大贡献而获得该年度的化学诺贝尔奖,这标志着不对称合成这一学科在社会上和科学界已取得重大成就和较高地位。自此,手性物质的研究异军突起,有关不对称方法学的研究发展迅猛,而有机电化学不对称合成方法已逐渐成为不对称方法学的新兴研究方向。电化学不对称合成就是在各种手性诱导剂的作用下,将潜手性的物质通过电极过程转化为相应的有光学活性的物质。与一般的有机不对称合成相比,电化学方法具有反应条件温和、易于控制、手性催化剂用量小等优点。碳酸酯是性能优良的溶剂及萃取剂,医药化工应用广泛,由于碳酸酯的大量需求对其合成方法的研究起到推动作用,利用电化学方法将CO2与环氧化合物合成有价值的环状碳酸酯是最有前途的转化方法之一。因为该方法不仅可以固定导致温室效应的罪魁祸首C02,还可以将其作为经济、无毒、廉价且丰富的C1资源,合成重要的化工医药产品。近年来,将C02嵌入光学纯的或者外消旋的环氧化合物不对称合成环状碳酸酯的研究成果频繁地被报道,这些研究成果都是基于手性铝、镁、铬和钴等的金属配合物作为催化剂的有机反应研究体系。众所周知,有机不对称合成领域对C02与氧化苯乙烯不对称合成具有光学活性的苯乙烯环状碳酸酯的研究已经相当成熟,但是反应需要在高温高压、昂贵有毒的催化剂等苛刻的条件下才能进行。截止目前,电化学不对称合成环状碳酸酯的研究还没有被报道过,电化学不对称合成可以成功地避免在高温高压的苛刻条件下发生反应,对反应装置的要求不高,易于控制反应过程,大大降低成本。因此,本论文主要以氧化苯乙烯为基底,分别研究了由R-氧化苯乙烯电合成R-苯乙烯环状碳酸酯和由外消旋的氧化苯乙烯不对称电合成具有光学活性的苯乙烯环状碳酸酯。本论文的主要研究内容如下：(1)电催化R-氧化苯乙烯与CO2合成R-苯乙烯环状碳酸酯常温常压下,在饱和了C02的一室型电解池中,乙腈作溶剂,镁棒作阳极,Ss(316)作阴极电催化R-氧化苯乙烯与CO2合成R-苯乙烯环状碳酸酯。运用含手性柱的HPLC(OD-H)对产物进行定量分析,考察各个电解条件(如支持电解质、电量、电流密度、反应温度等)对环状碳酸酯的ee值及产率的影响。在实验条件的优化基础上,该电合成方法能够获得较高的产率和ee值。该研究首次利用DFT高斯计算对环氧化合物的区域选择性开环进行研究,结合电化学对比实验与DFT高斯计算证明参与电解反应的是二氧化碳自由基负离子而不是CO2分子。运用循环伏安法考察CO2、环氧化合物等的电化学还原行为,参考文献并结合实验分析结果,推测出反应机理。(2)CoⅡ-(R,R)(salen)催化外消旋的氧化苯乙烯与CO2不对称电合成具有光学活性的苯乙烯环状碳酸酯在电催化R-氧化苯乙烯与CO2合成R-苯乙烯环状碳酸酯的研究基础上,以外消旋的氧化苯乙烯为基底,Ss(316)作阴极,Pt作阳极,在Co⒉-(R,R)(salen)催化作用下,进行电化学固定CO2不对称电合成具有光学活性的苯乙烯环状碳酸酯的研究。常压,50℃下,考察了CoⅡ-(R,R)(salen)的催化能力,运用循环伏安法研究了该催化剂的电化学行为,考察了溶剂、催化剂的用量、电极材料、温度对该反应ee值和产率的影响,推测出合理的反应机理。同时运用镁离子和催化剂CoⅡ-(R,R)(salen)进行分步协同反应不对称合成具有光学活性的苯乙烯环状碳酸酯,考察各种影响因素,推测反应机理。更多还原

【Abstract】 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.更多还原