Borenium-Ion-Catalyzed C–H Borylation of Arenes,Journal of the American Chemical Society

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Borenium-Ion-Catalyzed C–H Borylation of Arenes
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2022-12-16 , DOI: 10.1021/jacs.2c12151
Xinyue Tan ₁ , Xi Wang ₁ , Zhen Hua Li ₁ , Huadong Wang ₁

Affiliation

Non-metal-catalyzed C–H borylation of arenes represents a sustainable and environment-friendly approach for the functionalization of arenes. Despite its promise as an alternative to traditional transition-metal systems, its substrate scope is generally limited to electron-rich arenes, thus hindering its application in organic synthesis. Herein, we report the development of a borenium-ion catalyst which can borylate unactivated arenes under ambient conditions with 4-chlorocatecholborane (HBcat^Cl) as borylation reagent. This metal-free catalytic system is suitable for the borylation of C–H bonds in sterically encumbered positions, which has been a challenging task for transition-metal systems. Additionally, this catalytic system allows para-selective one-pot borylation of phenols, which has not been achieved by using transition-metal systems. Our mechanistic investigations and computational studies support a synergistic activation of the H–Bcat^Cl bond by the arene substrate and the borenium-ion catalyst. This generates a Wheland intermediate and a neutral hydroborane species and is followed by deprotonation of the Wheland intermediate with the hydroborane species. The latter step of C–H bond cleavage is likely the rate-limiting step.

中文翻译：

硼离子催化的芳烃 C-H 硼酸化反应

芳烃的非金属催化 C-H 硼化代表了一种可持续且环境友好的芳烃功能化方法。尽管它有望替代传统的过渡金属体系，但其底物范围通常仅限于富电子芳烃，因此阻碍了其在有机合成中的应用。在此，我们报告了一种硼离子催化剂的开发，该催化剂可以在环境条件下使用 4-氯儿茶酚硼烷 (HBcat ^Cl ) 作为硼酸化试剂对未活化的芳烃进行硼酸化。这种无金属催化体系适用于空间位阻位置 C-H 键的硼化，这对过渡金属体系来说一直是一项具有挑战性的任务。此外，该催化系统允许对-酚类的选择性一锅硼化，这尚未通过使用过渡金属系统实现。我们的机理研究和计算研究支持芳烃底物和硼离子催化剂对 H-Bcat ^{Cl键的协同活化。}这会生成 Wheland 中间体和中性氢硼烷物质，然后 Wheland 中间体与氢硼烷物质发生去质子化。C-H 键断裂的后一步可能是限速步骤。

更新日期：2022-12-16

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