| In recent years, researchers have carried out many research experiments in the transition metal-catalyzed reactions, which possess the advantages of high selectivity and high stability, etc. However, unlike the great concern received in the experimental studies, theoretical studies are relatively lagging behind and leaving many problems cannot be solved. For some experiments, reaction phenomena can not be explained by general chemical law, and the inherent mechanism can not be clearly explained. The reaction mechanism study using traditional methods are inadequate to do the research on transition metal-catalyzed reactions. Because of these problems, it is not conducive to the further development new organic transition metal catalyst and skeleton construction of new molecules. Therefore, in order to explore the mechanism of the experimental phenomenon, it is of great scientific and practical significance to carry out the corresponding theoretical study with the help of quantum chemical tools.In the thesis, the Au-catalyzed [2 + 2 + 2] cycloadditions of ynamides with two discrete nitriles were theoretically studied with the aid of DFT calculations, and clarified the detailed reaction mechanism in the molecular level. The study has a deeper understanding in the [2 + 2 + 2] cycloaddition reaction, and the research findings may help future experimental study in [2 + 2 + 2] cycloaddition reaction.The main innovation and research results of this thesis are as follows:The reaction under consideration is found to start from binding of the catalyst with the ynamide rather than with the nitrile. The Au(I)–ynamide species(1) can effectively induce dimerization of two nitrile molecules while the catalyst only cannot. The Au(I)–ynamide species(1) is revealed to be more reactive than the Au(I)–nitrile species(2). Also, the regioselectivity and the influence of EWG vs. EDG involved in the reaction were also rationalized.
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