铑(III)催化2-乙烯基苯酚衍生物与乙炔或一氧化碳的环加成反应机理研究

本文采用密度泛函理论M06-2X方法计算了铑催化直接合成苯并氧杂环庚三烯和香豆素衍生物的环加成反应. 通过对乙炔或一氧化碳的碳原子从六元环反应物的两个不同方向攻击和插入的两种竞争机制进行了计算研究，以阐明这种转变的主要特征. 计算结果表明：(i)炔烃或一氧化碳的插入过程是反应的关键步骤；(ii)对于乙炔的(5+2)环加成反应，需要更高的能量来破坏反应物的Rh$-$O 键，反应倾向于从Rh$-$C键一侧完成插入；(iii)对于一氧化碳的(5+1)环加成反应，两条反应路径的活化自由能都较低，两个通道会产生竞争机制.

Mechanistic Investigation on Rhodium(III)-Catalyzed Cycloaddition of 2-Vinylphenol Derivatives with Ethyne or Carbon Monoxide by DFT Study

Rhodium-catalyzed cycloaddition re-action was calculated by density func-tional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives. In this work, we conducted a computational study of two competitive mechanisms in which the carbon atom of acetylene or carbon monoxide attacked and in-serted from two different directions of the six-membered ring reactant to clarify the principle characteristics of this transformation. The calculation results reveal that: (i) the insertion process of alkyne or carbon monoxide is the key step of the reaction; (ii) for the (5+2) cycloaddition reaction of acetylene, higher energy is required to break the Rh-O bond of the reactant, and the reaction tends to complete the insertion from the side of the Rh-C bond; (iii) for the (5+1) cycloaddition of carbon monoxide, both reaction paths have lower activation free energy, and the two will generate a competition mechanism.