【作者】 胡章勇；

【导师】 李明；

【作者基本信息】 西南大学 ， 物理化学， 2010， 硕士

【摘要】 本工作应用量子化学密度泛函B3LYP方法,分别对溴化亚铜催化合成Y,δ-炔基-β-氨基酸衍生物和三氯化金、三氟磺酸银催化1,6-二醇联烯炔环化的反应机理进行了研究,分析了影响催化剂催化活性的因素,讨论了催化剂浓度、催化剂配体对反应化学选择性和催化机理的影响,为设计新型的催化剂提供了有价值的理论依据。1.溴化亚铜催化合成γ，δ-炔基-β-氨基酸衍生物反应的密度泛函研究用密度泛函理论的B3LYP方法对CuBr(溴化亚铜)催化合成γ，6-炔基-β-氨基酸衍生物的机理进行了理论计算,得到三条反应路线。对所有过渡态、中间体和产物做了频率分析。通过IRC扫描确认了重要过渡态的正确性。分析了反应中各物种的电荷分布、重要化学键的成键临界点和成环临界点的电荷密度。计算表明在气相和液相下,优势路线的决速步都是胺与炔酯的结合过程；建议的机理能合理解释所有实验现象。2.三氯化金、三氟磺酸银催化1,6-二醇联烯炔环化反应的理论研究：浓度与配体影响用密度泛函理论的B3LYP泛函以及溶剂化模型PCM对金／银过渡金属催化1,6-二醇联烯炔环化反应的机理进行了理论研究,得到了金／银催化反应机理。该机理详细讨论了催化剂浓度、配体、溶剂化效应对反应的影响。计算结果表明,金、银催化机理不同。反应产生Pχ是金催化剂催化体系的优势线路；生成PZ是银催化剂催化的优势线路,它们与实验结果-致。单分子金催化剂催化1,6-二醇联烯炔的所有反应路径需高的活化自由能,双分子金催化剂的参与使所有反应路径的活化能大大降低。这说明产物的化学选择性与催化剂浓度有很大的关系。配体作为质子运输工具参与反应,协助质子转移,进而降低反应的活化能和改变反应的路径。因此配体的合理选择对催化剂的催化效率有重要作用。溶剂化效应对金、银催化机理影响很大,且不同。理论计算给出的机理能合理的解释所有实验现象。更多还原

【Abstract】 In the present paper, the density functional method (B3LYP functional) is employed to study the reaction mechanisms of direct amination of the synthesis of y,8-alkynyl-β-amino acid derivatives catalyzed by CuBr, and gold/silver-catalyzed cyclization of allenyne-1,6-diols, respectively. Factors that control the efficiency of catalysis are analyzed. The effects of the concentration of catalysts, their ligands on the mechanism and chemoselectivity have been examined, thereby these information for designing new type of catalysis reactions provide in theoretical level.1. DFT Study the Mechanism of the Synthesis of y,8-Alkynyl-β-amino Acid Derivatives Catalyzed by CuBrThe mechanism of the synthesis of y,δ-alkynyl-β-amino acid derivatives is investigated employing the density functional theory (the B3LYP functional is used), and three reaction pathways are suggested. The frequency analysis is performed for all the transition states, intermediates and products. The geometries of the important transition states are confirmed by the IRC scanning. In order to make clear the reaction mechanism, the charge distribution of all species and the electronic densities of the bond critical points (BCP) and the ring critical points (RCP) for the key bonds are calculated and discussed. Our results indicate that in the gas phase and the liquid phase, the rate-determining steps of the dominant pathways are the reaction between amine and alkynyl ester. The suggested mechanism can explain reasonably all experimental observations.2. Mechanism of Cyclization of Allenyne-1,6-diols Catalyzed by Gold and Silver Compounds:the Effects of Concentrations and Ligands of CatalystsBy means of the density functional theory (DFT) combined with the polarized continuum models, the cyclizations of allenyne-1,6-diols catalyzed by the gold and silver complexes are computed, the mechanisms of cyclization are suggested, and the effects of the concentration of catalysts, their ligands, and the solvent on the mechanisms are analysed in detail. As shown, the Au-catalyzed mechanism differs to the Ag-catalyzed mechanism. The most favorable reaction path for the Au-catalyzed mechanism gives the main product Px and that for the Ag-catalyzed mechanism leads to the main product Pz, which are in agreement with the experiment. All the reaction paths for the cyclization of allenyne-1,6-diols catalyzed by single AuCl3 complex have high energy barriers. Participation of two AuCl3 complexes in the catalyzed cyclization can make energy barriers for all the reaction paths be lowered remarkably. These results imply the close relationship between the concentration of catalysts and the chemoselectivity of products. The ligands, as a proton shuttle, can take part in the reaction and assist the transfer of proton, and further lower the reaction energy barriers and change the reaction routes. The choice of the ligands of catalysts may be important to the efficiency of catalysis. The effects of solvent on the gold-and silver-catalyzed mechanisms are remarkable and also quite different. The theoretically suggested mechanisms explain reasonably all the experimental observations.更多还原