Guria Saikat, Hassan Mirja Md Mahamudul, Dey Sayan, Singh Krishna Nand, Chattopadhyay Buddhadeb
Department of Biological & Synthetic Chemistry, Center of Biomedical Research, SGPGIMS Campus, Raebareli Road, Lucknow, 226014, Uttar Pradesh, India.
Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi, 221005, India.
Angew Chem Int Ed Engl. 2024 Oct 7;63(41):e202409010. doi: 10.1002/anie.202409010. Epub 2024 Sep 5.
Site-selective C-H bond functionalization of arenes at the para position remains extremely challenging primarily due to its relative inaccessibility from the catalytic site. As a consequence, it is significantly restricted to limited molecular scaffolds. Herein, we report a method for the para-C-H borylation of aromatic aldimines and benzylamines using commercially available ligands under iridium catalysis. The established method displays excellent para selectivity for variously substituted aromatic aldimines, benzylamines and bioactive molecules. Based on several control experiments, it is proposed that a Lewis acid-base interaction between the nitrogen and boron functionality guides the para selectivity via a steric shield for the aromatic aldimines, where Bpin acts as a transient directing group. However, the steric shield of the in situ generated N-Bpin moiety controlled the overall selectivity for the para borylation of benzylamines.
芳烃在对位的位点选择性C-H键官能化仍然极具挑战性，主要原因是其相对难以从催化位点接近。因此，它被显著限制在有限的分子骨架上。在此，我们报道了一种在铱催化下使用市售配体对芳香醛亚胺和苄胺进行对位C-H硼化的方法。所建立的方法对各种取代的芳香醛亚胺、苄胺和生物活性分子表现出优异的对位选择性。基于几个对照实验，有人提出氮和硼官能团之间的路易斯酸碱相互作用通过对芳香醛亚胺的空间屏蔽来引导对位选择性，其中Bpin作为瞬态导向基团。然而，原位生成的N-Bpin部分的空间屏蔽控制了苄胺对位硼化的整体选择性。
