Distinct Roles of Ag(I) and Cu(II) as Cocatalysts in Achieving Positional-Selective C-H Alkenylation of Isoxazoles: A Theoretical Investigation.,The Journal of Organic Chemistry

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Distinct Roles of Ag(I) and Cu(II) as Cocatalysts in Achieving Positional-Selective C-H Alkenylation of Isoxazoles: A Theoretical Investigation.
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2020-06-03 , DOI: 10.1021/acs.joc.0c00721
Jing Zhang _{1,

2} , Lingli Han _{1,

2} , Siwei Bi ₂ , Tao Liu _{1,

2}

Affiliation

For C–H alkenylation of aryl-substituted diarylisoxazoles, one mode is N-directed C–H alkenylation and the other is C–H alkenylation in the isoxazole ring. In this study, selective C–H alkenylations of 3,5-diarylisoxazoles have been investigated theoretically with the aid of density functional theory (DFT) calculations. With Cp*Rh^III as the catalyst, the N-directed C–H alkenylation is preferred as a result of the stronger interaction energy caused by the nitrogen-directing effect. With Pd(OAc)₂ as the catalyst and Ag₂CO₃ as the cocatalyst, their combination switches the regioselectivity to the C–H alkenylation in the isoxazole ring. The strong structural distortion involved in the competing N-directed olefin insertion transition state was found to suppress N-directed C–H alkenylation. With Pd(OAc)₂ as the catalyst and Cu(OTf)₂ as the cocatalyst, the N-directed C–H alkenylation becomes preferred due to the strong coordination of the nitrogen atom to the copper center. In particular, the structural and mechanistic information involved in the above two heterodimetallic Pd/Ag and Pd/Cu catalytic systems will help toward understanding and designing novel relevant heterodimetallic-catalyzed reactions.

中文翻译：

Ag（I）和Cu（II）作为助催化剂在实现异恶唑的位置选择性CH烯基化中的不同作用：一项理论研究。

对于芳基取代的二芳基异恶唑的C–H烯基化，一种模式是N-导向的C–H烯基化，另一种模式是异恶唑环中的C–H烯基化。在这项研究中，借助密度泛函理论（DFT）计算，对3,5-二芳基异恶唑的选择性C–H烯基化进行了理论研究。使用Cp * Rh ^III作为催化剂，由于氮导向作用会产生较强的相互作用能，因此优选N-导向的C-H烯基化反应。以Pd（OAc）₂为催化剂，Ag ₂ CO ₃作为助催化剂，它们的组合将区域选择性切换为异恶唑环中的C–H烯基化。发现在竞争的N定向烯烃插入过渡态中涉及的强结构变形可以抑制N定向CH烯基化。以Pd（OAc）₂为催化剂，Cu（OTf）₂为助催化剂，由于氮原子与铜中心的强配位作用，N-导向的CH链烯基化反应成为首选。特别地，以上两个杂双金属Pd / Ag和Pd / Cu催化体系中涉及的结构和机理信息将有助于理解和设计新颖的相关异双金属催化反应。

更新日期：2020-07-02

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