Elucidating the Role of the Boronic Esters in the Suzuki-Miyaura Reaction: Structural, Kinetic, and Computational Investigations.
Elucidating the Role of the Boronic Esters in the Suzuki-Miyaura Reaction: Structural, Kinetic, and Computational Investigations.
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DOI：
10.1021/jacs.8b00400
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发表时间：
2018-03-28
影响因子：
15
通讯作者：
Denmark SE
中科院分区：
文献类型：
--
作者：
Thomas AA;Zahrt AF;Delaney CP;Denmark SE
Suzuki-Miyaura反应是最实用的钯催化的交叉偶联反应，因为其广泛的适用性、金属（B）的低毒性和各种各样的市售硼底物。已经为该方法开发了各种各样的硼酸和硼酸酯，每种硼酸和硼酸酯具有不同的性质。尽管Suzuki-Miyaura反应很受欢迎，但有机片段从硼转移到钯的精确方式对于这些试剂来说仍然是难以捉摸的。在这里，我们报告的观察和表征的pretransmetalation中间体产生的各种常用的硼酸酯。能够确认pretransmetalation中间体的中间性提供了机会，以澄清机械方面的有机部分从硼转移到钯的关键transmetalation步骤。一系列的结构，动力学和计算研究表明，硼酸酯可以直接transmetalate没有事先水解。此外，取决于所采用的硼酸酯，观察到B-芳基基团的转移的显著速率增强。总之，确定了两个关键特征，使有机片段从硼转移到钯：（1）在钯原子上产生空配位位点的能力和（2）与硼结合的ipso碳的亲核特性。这两个特征最终都与硼酸酯中氧原子的电子密度有关。
The Suzuki–Miyaura reaction is the most practiced palladium-catalyzed, cross-coupling reaction because of its broad applicability, low toxicity of the metal (B), and the wide variety of commercially available boron substrates. A wide variety of boronic acids and esters, each with different properties, have been developed for this process. Despite the popularity of the Suzuki–Miyaura reaction, the precise manner in which the organic fragment is transferred from boron to palladium has remained elusive for these reagents. Herein, we report the observation and characterization of pretransmetalation intermediates generated from a variety of commonly employed boronic esters. The ability to confirm the intermediacy of pretransmetalation intermediates provided the opportunity to clarify mechanistic aspects of the transfer of the organic moiety from boron to palladium in the key transmetalation step. A series of structural, kinetic, and computational investigations revealed that boronic esters can transmetalate directly without prior hydrolysis. Furthermore, depending on the boronic ester employed, significant rate enhancements for the transfer of the B-aryl groups were observed. Overall, two critical features were identified that enable the transfer of the organic fragment from boron to palladium: (1) the ability to create an empty coordination site on the palladium atom and (2) the nucleophilic character of the ipso carbon bound to boron. Both of these features ultimately relate to the electron density of the oxygen atoms in the boronic ester.
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影响因子：
1.7
作者：
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通讯作者：
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