Iridium-Catalyzed C–H Borylation of Heteroarenes: Scope, Regioselectivity, Application to Late-Stage Functionalization, and Mechanism,Journal of the American Chemical Society

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Iridium-Catalyzed C–H Borylation of Heteroarenes: Scope, Regioselectivity, Application to Late-Stage Functionalization, and Mechanism
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2014-03-06 , DOI: 10.1021/ja412563e
Matthew A. Larsen ₁ , John F. Hartwig ₁

Affiliation

A study on the iridium-catalyzed C-H borylation of heteroarenes is reported. Several heteroarenes containing multiple heteroatoms were found to be amenable to C-H borylation catalyzed by the combination of an iridium(I) precursor and tetramethylphenanthroline. The investigations of the scope of the reaction led to the development of powerful rules for predicting the regioselectivity of borylation, foremost of which is that borylation occurs distal to nitrogen atoms. One-pot functionalizations are reported of the heteroaryl boronate esters formed in situ, demonstrating the usefulness of the reported methodology for the synthesis of complex heteroaryl structures. Application of this methodology to the synthesis and late-stage functionalization of biologically active compounds is also demonstrated. Mechanistic studies show that basic heteroarenes can bind to the catalyst and alter the resting state from the olefin-bound complex observed during arene borylation to a species containing a bound heteroarene, leading to catalyst deactivation. Studies on the origins of the observed regioselectivity show that borylation occurs distal to N-H bonds due to rapid N-H borylation, creating an unfavorable steric environment for borylation adjacent to these bonds. Computational studies and mechanistic studies show that the lack of observable borylation of C-H bonds adjacent to basic nitrogen is not the result of coordination to a bulky Lewis acid prior to C-H activation, but the combination of a higher-energy pathway for the borylation of these bonds relative to other C-H bonds and the instability of the products formed from borylation adjacent to basic nitrogen.

中文翻译：

铱催化的杂芳烃的 C-H 硼化：范围、区域选择性、后期功能化的应用和机制

报道了铱催化杂芳烃的 CH 硼化的研究。发现几种含有多个杂原子的杂芳烃适合由铱 (I) 前体和四甲基菲咯啉的组合催化的 CH 硼化。对反应范围的研究导致了预测硼化的区域选择性的强大规则的发展，其中最重要的是硼化发生在氮原子的远端。报告了原位形成的杂芳基硼酸酯的一锅官能化，证明了所报告的方法对合成复杂杂芳基结构的有用性。还展示了这种方法在生物活性化合物的合成和后期功能化中的应用。机理研究表明，碱性杂芳烃可以与催化剂结合，并将在芳烃硼化过程中观察到的烯烃结合复合物的静止状态改变为含有结合杂芳烃的物质，从而导致催化剂失活。对观察到的区域选择性起源的研究表明，由于快速的 NH 硼酸化，硼酸化发生在 NH 键的远端，为与这些键相邻的硼酸化创造了不利的空间环境。计算研究和机理研究表明，与碱性氮相邻的 CH 键缺乏可观察到的硼化并不是在 CH 活化之前与庞大的路易斯酸配位的结果，

更新日期：2014-03-06

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