Bisai Milan Kumar, Łosiewicz Justyna, Nichol Gary S, Dominey Andrew P, Thomas Stephen P, Macgregor Stuart A, Ingleson Michael J
EaStCHEM School of Chemistry, University of Edinburgh Edinburgh EH9 3FJ UK
GSK Medicines Research Centre Gunnels Wood Road, Stevenage Hertfordshire SG1 2NY UK.
Chem Sci. 2025 Apr 15. doi: 10.1039/d5sc02085a.
The metal-catalyzed intermolecular C-H borylation of arenes is an extremely powerful C-H functionalization methodology. However, to date it is effectively restricted to forming organo-boronate esters (Aryl-B(OR)) with its application to form other organoboranes rarely explored. Herein, we report a catalytic intermolecular heteroarene C-H borylation method using the commercial hydroborane 9-borabicyclo-[3.3.1]-nonane, (H-BBN). This process is effective for mono- and di-borylation to form a range of heteroaryl-BBN compounds using either NacNacAl or NacNacZn (NacNac = {(2,6-PrCH)N(CH)C}CH) based catalysts. Notably, mechanistic studies indicated a highly unusual σ-bond metathesis process between NacNacZn-Aryl and the dimeric hydroborane, with first order kinetics in the hydroborane dimer ((H-BBN)). Our calculated metathesis pathway involves ligand non-innocence and addition of both H-BBN units in (H-BBN) to the NacNacZn-heteroaryl complex. This is in contrast to the conventional σ-bond metathesis mechanism using other hydroboranes which invariably proceeds by reaction of one equivalent of a monomeric hydroborane (, H-B(OR)) with a M-C unit. Overall, this work demonstrates the potential of extending catalytic arene C-H borylation beyond boronate esters, while highlighting that the σ-bond metathesis reaction can be mechanistically more complex when utilizing dimeric hydroboranes such as (H-BBN).
金属催化的芳烃分子间C-H硼化反应是一种极为强大的C-H官能团化方法。然而，迄今为止，它实际上仅限于形成有机硼酸酯（芳基-B(OR)），很少探索其用于形成其他有机硼烷的应用。在此，我们报道了一种使用市售硼烷9-硼双环-[3.3.1]-壬烷（H-BBN）的催化分子间杂芳烃C-H硼化方法。该过程对于单硼化和双硼化是有效的，使用基于NacNacAl或NacNacZn（NacNac = {(2,6-PrCH)N(CH)C}CH）的催化剂可形成一系列杂芳基-BBN化合物。值得注意的是，机理研究表明NacNacZn-芳基与二聚硼烷之间存在高度不寻常的σ键复分解过程，硼烷二聚体（(H-BBN)）呈现一级动力学。我们计算出的复分解途径涉及配体的非无辜性以及(H-BBN)中两个H-BBN单元都加成到NacNacZn-杂芳基配合物上。这与使用其他硼烷的传统σ键复分解机理形成对比，后者总是通过一当量的单体硼烷（H-B(OR)）与M-C单元反应进行。总体而言，这项工作展示了将催化芳烃C-H硼化反应扩展到硼酸酯之外的潜力，同时突出了在使用二聚硼烷如(H-BBN)时，σ键复分解反应在机理上可能更复杂。
