Mechanistic Study of Unprecedented Highly Regioselective Hydrocyanation of Terminal Alkynes: Insight into the Origins of the Regioselectivity and Ligand Effects,Journal of Computational Chemistry

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Mechanistic Study of Unprecedented Highly Regioselective Hydrocyanation of Terminal Alkynes: Insight into the Origins of the Regioselectivity and Ligand Effects
Journal of Computational Chemistry ( IF 3.4 ) Pub Date : 2019-11-11 , DOI: 10.1002/jcc.26099
Dandan Jiang ₁ , Mingxing Fu ₁ , Yajun Zhang ₂ , Qianqian Li ₁ , Kai Guo ₂ , Yanhui Yang ₁ , Lili Zhao ₁

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Density functional theory (DFT) calculations were performed to gain insight into the mechanism of the nickel‐catalyzed hydrocyanation of terminal alkynes with Zn(CN)2 and water to exclusively generate the branched nitrile with excellent Markovnikov selectivity. After precatalyst activation to give the LNi(0) active species, the transformation proceeds via the following steps: (1) oxidative addition of H2O to the LNi(0) provides the intermediate LNi(II)H(OH); (2) ligand exchange of LNi(II)H(OH) with Zn(CN)2 gives the intermediate LNi(II)H(CN); (3) alkyne insertion to the LNi(II)H(CN) forms the alkenyl nickel complex, followed by the reductive elimination step reaching the final product. This mechanism is kinetically and thermodynamically more favorable than that of the experimental proposed ones. On the basis of the experimental observations, more water molecules cannot further improve the reaction as it has also been rationalized. Furthermore, the origin of the high regioselectivity of the product, the variable effectiveness of the metal mediator as function of ligands, as well as the high yield of the alkyl‐substituted alkynes substrates, is analyzed in detail. © 2019 Wiley Periodicals, Inc.

中文翻译：

末端炔烃前所未有的高区域选择性氢氰化的机理研究：深入了解区域选择性和配体效应的起源

进行密度泛函理论 (DFT) 计算以深入了解镍催化末端炔烃与 Zn(CN)2 和水的氢氰化反应机理，以专门生成具有优异马尔可夫尼科夫选择性的支化腈。在预催化剂活化得到 LNi(0) 活性物质后，转化通过以下步骤进行：(1) 将 H2O 氧化加成到 LNi(0) 中，提供中间体 LNi(II)H(OH)；(2) LNi(II)H(OH)与Zn(CN)2配体交换得到中间体LNi(II)H(CN)；(3) 炔烃插入 LNi(II)H(CN) 形成烯基镍配合物，然后通过还原消除步骤到达最终产物。这种机制在动力学和热力学上比实验提出的机制更有利。根据实验观察，更多的水分子不能进一步改善反应，因为它也被合理化了。此外，详细分析了产物高区域选择性的起源、金属介体作为配体函数的可变有效性以及烷基取代的炔烃底物的高产率。© 2019 威利期刊公司。

更新日期：2019-11-11

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