Mechanism of Z-Selective Hydroalkylation of Terminal Alkynes.
Mechanism of Z-Selective Hydroalkylation of Terminal Alkynes.
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DOI：
10.1021/jacs.1c07613
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发表时间：
2021-10-13
影响因子：
15
通讯作者：
Lalic, Gojko
中科院分区：
文献类型：
--
作者：
Lee, Mitchell T.;Lalic, Gojko
本文对银催化末端炔的z选择性氢烷基化反应进行了详细的机理研究。结合已建立的炔选择性氢烷基化的机理范式，我们探索了炔自由基碳金属化的机理。实验结果为最初提出的自由基机制提供了强有力的证据，并使我们提出了一种基于硼酸盐形成和1,2-金属酸盐位移的z -选择性烷基化的新机制。这一新机制为反应中观察到的良好的z选择性提供了理论依据。一系列的化学计量实验已经探讨了所提出的基本步骤的可行性，并揭示了银催化剂在中间体原波解中的额外作用。最后，通过一系列的动力学测量、KIE实验和竞争实验，我们确定了催化剂的周转限制步骤和静息状态。我们相信这一研究结果将有助于进一步探索和发展相关的炔烃转化。
This article describes a detailed mechanistic study of the silver-catalyzed Z-selective hydroalkylation of terminal alkynes. Considering the established mechanistic paradigms for Z-selective hydroalkylation of alkynes, we explored a mechanism based on the radical carbometallation of alkynes. Experimental results have provided strong evidence against the initially proposed radical mechanism and have led us to propose a new mechanism for the Z-selective hydroalkylation of alkynes based on boronate formation and a 1,2-metallate shift. The new mechanism provides a rationale for the excellent Z-selectivity observed in the reaction. A series of stoichiometric experiments have probed the feasibility of the proposed elementary steps and revealed an additional role of the silver catalyst in the protodeboration of an intermediate. Finally, a series of kinetic measurements, KIE experiments, and competition experiments allowed us to identify the turnover limiting step and the resting state of the catalyst. We believe that the results of this study will be useful in further exploration and development of related transformations of alkynes.
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