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本文运用密度泛函理论(DFT)计算,研究了Ni(0)催化炔烃与醛分子间还原偶联反应的机理,确定了该反应最优反应路径是氧化环化、转金属以及还原消除.计算结果表明,无论使用IMes还是SIPr作为配体,反应的区域选择性都由氧化环化步控制;而硅烷的转金属化是整个反应的决速步.这不同于以往对Ni(0)催化炔醛还原偶联反应的理论研究.理论计算表明,当使用IMes作为配体时,主要产物为2-甲基-3-苯基烯丙基硅醚;当使用SIPr作为配体时,主产物则是3-甲基-2-苯基烯丙基硅醚.无论从主产物还是区域选择性,本文的计算结果都与实验报道一致.本文使用反应路径形变-结合能模型研究了IMes作为配体时的区域选择性.结果表明,形成主产物时具有较低的形变能.也就是说,过渡态中炔烃部分与苯基折叠程度较小,共轭程度更大,因此主产物为2-甲基-3-苯基烯丙基硅醚.本课题组还使用2D投影图模型研究了空间效应对不同配体的影响.结果表明,当使用IMes配体时,由于配体体积较小,可以容纳苯基在其周围,从而减小了炔烃上的苯基与醛上苯基的排斥;而使用大位阻的SIPr作为配体时,配体与炔烃上的苯基排斥很大,从而不利于2-甲基-3-苯基烯丙基硅醚的生成.
In this paper, the mechanism of Ni (0) -catalyzed reductive coupling reaction between alkyne and aldehydes was studied by using density functional theory (DFT) calculations. The optimal reaction route of the reaction was oxidative cyclization, metathesis and reduction. The calculated results show that the regioselectivity of the reaction is controlled by the oxidative cyclization step whether IMes or SIPr is used as the ligand, and the trans-metallization of silane is the strongest step of the whole reaction, which is different from the previous studies on Ni (0) catalysis Theoretical studies on the reductive coupling reaction of acetylenic aldehydes The theoretical calculations show that when IMes is used as the ligand, the major product is 2-methyl-3-phenylallylsilyl ether and when SIPr is used as the ligand, the main product 3-methyl-2-phenylallylsilyl ether.Compared with the experimental results, the calculation results of this thesis are in good agreement with the experimental results in both the main product and the regioselectivity.In this paper, we used the reaction path deformation-binding energy model The results show that the main product has lower deformation energy, that is to say, the degree of conjugation of the alkyne moiety in the transition state is smaller and the degree of conjugation is greater, so the main product is 2 - methyl-3-phenyl allyl siloxane.The group also use 2D projection The model studies the effect of spatial effects on different ligands. The results show that when the IMes ligands are used, the phenyl groups can be held around them due to their small size, reducing the phenyl and aldehydes on alkynes Phenyl group. However, when using sterically hindered SIPr as a ligand, the phenyl groups on the ligands and alkynes are highly repulsive, which is unfavorable for the formation of 2-methyl-3-phenyl allylsilyl ether.