Cobalt-Catalyzed Regioselectivepara-Amination of Azobenzenesvia Nucleophilic Aromatic Substitution of Hydrogen

The metal-catalyzed nucleophilic aromatic substitu-tion of hydrogen (SNArH) via coordination of the substituent onthe aromatic ring to the metal catalyst, in terms of reactivity,substrate type, and reaction selectivity, complements the transitionmetal-catalyzed C-H functionalization that proceeds via C-Hmetalation but remains an elusive target. Described herein is thedevelopment of an unprecedented cobalt-catalyzedpara-selectiveamination of azobenzenes, which is essentially a metal-promotedSNArH process as revealed by Hammett analysis, thus illustrating the concept that coordination of the substituent on the arene ringto the metal catalyst may result in electrophilic activation of the arene ring toward SNArH. This cobalt-catalyzed protocol allows theuse of a variety of both aliphatic amines and anilines as aminating reagents, tolerates electronically diverse substituents ofazobenzene, and furnishes the corresponding products in good yields with a regiospecific selectivity forpara-amination.

Automated summary

This work describes the development of an unprecedented cobalt-catalyzed para-selective amination of azobenzenes, which demonstrated the concept of electrophilic activation of the arene ring toward SNArH through coordination of the substituent on the arene ring to the metal catalyst. The reaction showed broad substrate scope, good yields, and regioselectivity for para-amination.