Sterically Controlled Lewis Acid−Base Interaction Toward para‐Selective Borylation of Aromatic Aldimines and Benzylamines

Abstract

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 the 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 displayed excellent para‐selectivity for variously substituted aromatic aldimines, benzylamines and bioactive molecules. Based on the several control experiments, it has been realized 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.