Cu催化体系的醇有氧氧化反应机理的理论研究

发布时间：2018-05-16 13:52

本文选题：铜系催化剂 + 醇氧化　；参考：《内蒙古工业大学》2017年硕士论文

【摘要】：醇的选择性氧化在有机合成中是非常重要的反应之一,其产品在精细化学品和有机中间体的合成中都有广泛的应用。为了满足环境和经济的需求,人们都在积极的寻找绿色、有效的氧化方法来代替传统的化学计量氧化。模拟天然酶催化的高效性和高选择性的性质来合成小分子化合物是当今化学与仿生学前沿的课题之一。目前,已经提出的以铜为中心的催化剂有很多,它们对醇的催化氧化是非常有效的。因此,了解以Cu为中心的催化剂的微观的反应机制不仅对均相铜体系提供有益的见解,还为设计新型的高效催化剂提供理论基础。本论文主要使用密度泛函方法,从量子化学角度出发,研究了以Cu为中心的催化剂的微观反应机理,计算了反应势能面上的反应物、中间体、过渡态和产物的几何结构。具体的研究工作如下:1.采用B3LYP密度泛函方法计算(bipy)Cu II-TEMPO/DBU(NMI)催化体系催化氧化一级醇的反应机理。我们研究了两条可能的反应路径(路径A和路径B),计算结果显示,底物氧化过程中的氢原子转移步骤为速控步骤,其中,DBU为碱时,Cu-OH夺取Cα-H上的氢原子;NMI为碱时,TEMPO夺取Cα-H上的氢原子,这与动力学实验结果一致。计算得到在(bipy)Cu II-TEMPO催化系统中,DBU为碱时的反应势垒比NMI为碱时的反应势垒低,这与实验上DBU碱的活性比NMI碱的活性高的结论一致。同时,文章中证明了-OTf阴离子的重要性,即-OTf阴离子能帮助碱夺氢。2.采用M06L密度泛函方法计算了二叔丁基二氮杂环丙酮(L)/CuBr催化体系催化氧化一级醇,二级醇成为相应的羰基化合物的反应机理。在该体系中活性物质为[CuL]Br,对于该活性物质,提出了两种可能的结构:二价铜配合物[Cu(II)-·L~-]Br~-或者三价铜配合物[Cu(III)-L~(2-)]Br~-。计算结果显示,活性物质[CuL]Br是以二价铜配合物形式存在的。在该体系中,醇的氧化过程分为两个步骤,质子转移和氢原子转移。根据氢原子转移的不同,提出了两条可能的反应路径(路径A和路径B),计算结果显示,路径A是优势路径。此外,对于一级醇和二级醇来说,质子转移过程为速控步骤,能量势垒分别为16 kcal/mol和16.1 kcal/mol,在室温下能进行反应。对于该反应机理,配体L和反应底物的比例为1:1,与实验结果近似。
[Abstract]:Selective oxidation of alcohols is one of the most important reactions in organic synthesis, and its products are widely used in the synthesis of fine chemicals and organic intermediates. In order to meet the environmental and economic needs, people are actively looking for green, effective oxidation methods to replace the traditional stoichiometric oxidation. The synthesis of small molecular compounds by mimicking the high efficiency and selectivity of natural enzyme catalysis is one of the frontier topics in chemistry and bionics. At present, there are many copper-centered catalysts, which are very effective for the catalytic oxidation of alcohols. Therefore, understanding the microcosmic reaction mechanism of Cu-centered catalyst not only provides useful insights for homogeneous copper system, but also provides a theoretical basis for the design of novel high-efficient catalysts. In this paper, we mainly use density functional method to study the micro reaction mechanism of Cu catalyst from the angle of quantum chemistry, and calculate the geometric structure of reactants, intermediates, transition states and products on the potential energy surface of the reaction. The specific research work is as follows: 1: 1. The B3LYP density functional method was used to calculate the reaction mechanism of the catalytic oxidation of primary alcohols in the catalytic system of CuII-TEMPO / DBU NMIs. We have studied two possible reaction paths (path A and path BN). The calculation results show that the hydrogen atom transfer step in the substrate oxidation process is a rate-controlled step. The hydrogen atom on C 伪 -H is captured by Cu-OH when DBU is base, and the hydrogen atom on C 伪 -H is captured by TEMPO when NMI is base. This is in agreement with the kinetic experimental results. The results show that the reaction barrier of DBU base is lower than that of NMI base in II-TEMPO catalytic system, which is consistent with the experimental conclusion that the activity of DBU base is higher than that of NMI base. At the same time, the importance of the -OTF anion is proved, that is, the -OTF anion can help the alkali hydrogen capture. 2. M06L density functional method was used to calculate the reaction mechanism of the catalytic oxidation of primary alcohols and secondary alcohols into corresponding carbonyl compounds in the catalyst system of second tert Ding Ji diazocyclic acetone L / Cubr. In this system, the active material is [CuL] Br.The two possible structures of the active compound are [CuOIII-Ln-] Brn-, or the trivalent copper complex, [CuCIIII-LUXIAN2-2] Br-ON-, for which two possible structures have been proposed. The results show that the active compound [CuL] Br exists in the form of divalent copper complex. In this system, the oxidation of alcohols is divided into two steps: proton transfer and hydrogen atom transfer. According to the difference of hydrogen atom transfer, two possible reaction paths (path A and path B) are proposed. The calculated results show that path A is the dominant path. In addition, for primary alcohols and secondary alcohols, the proton transfer process is a rate-control step, and the energy barrier is 16 kcal/mol and 16.1 kcal / mol, respectively, and can react at room temperature. For the reaction mechanism, the ratio of the ligand L to the substrate is 1: 1, which is similar to the experimental results.
【学位授予单位】：内蒙古工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O621.251

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