美国普林斯顿大学Paul J. Chirik研究团队报道了C(sp2) -H活化的动力学和热力学控制实现了位点选择性硼化。相关研究成果于2023年12月8日发表于国际一流学术期刊《科学》。

在不依赖空间效应或引导基团的情况下区分电子上不同的碳-氢（C–H）键的催化剂在设计上具有挑战性。

该文中，描述了由N-烷基咪唑取代的吡啶二卡宾（ACNC）钳形配体负载的钴预催化剂，其能够实现氟代芳烃的无定向远程硼化，并将范围扩大到包括富电子芳烃、吡啶以及三氟和二氟甲氧基化芳烃，从而解决了第一排过渡金属C–H官能化催化剂的主要局限性之一。

尽管热力学上优选邻位C–H活化产生的钴-芳基络合物，但机制研究确定了在间位对C–H键活化的动力学偏好。因此，使用单个预催化剂初步证明了C–H硼化反应中的可切换位点选择性与硼试剂的关系。

附：英文原文

Title: Kinetic and thermodynamic control of C(sp2)–H activation enables site-selective borylation

Author: Jose B. Roque, Alex M. Shimozono, Tyler P. Pabst, Gabriele Hierlmeier, Paul O. Peterson, Paul J. Chirik

Issue&Volume: 2023-12-08

Abstract: Catalysts that distinguish between electronically distinct carbon-hydrogen (C–H) bonds without relying on steric effects or directing groups are challenging to design. In this work, cobalt precatalysts supported by N-alkyl-imidazole–substituted pyridine dicarbene (ACNC) pincer ligands are described that enable undirected, remote borylation of fluoroaromatics and expansion of scope to include electron-rich arenes, pyridines, and tri- and difluoromethoxylated arenes, thereby addressing one of the major limitations of first-row transition metal C–H functionalization catalysts. Mechanistic studies established a kinetic preference for C–H bond activation at the meta-position despite cobalt-aryl complexes resulting from ortho C–H activation being thermodynamically preferred. Switchable site selectivity in C–H borylation as a function of the boron reagent was thereby preliminarily demonstrated using a single precatalyst.

DOI: adj6527

Source: https://www.science.org/doi/10.1126/science.adj6527