Recent Advancements on Nitration of Anilines Utilizing Diverse Nitrating Agents

Nitroarenes are important intermediates in the synthesis of dyes, pharmaceuticals, and functional materials. The nitro group serves as a key precursor to amines, which have been widely employed in ortho-C(sp²)-H bond activation. Although the conventional electrophilic nitration of aniline using a strong acid mixture is well established, it suffers from several drawbacks, including the generation of acidic waste, low yields, poor selectivity, over-nitration, and limited functional group tolerance. As an alternative, transition-metal-catalyzed, directing-group-assisted regiospecific ortho-nitration of arene C-H bonds has emerged as a more efficient, convenient, atom-and stepeconomical approach that can proceed under mild conditions. In addition, various transition metal nitrates have demonstrated potential in the selective electrophilic nitration of anilines. However, ortho/para-mixtures of regioisomers are obtained in some cases. This review article summarizes all such recent advancements in the nitration reaction of protected anilines using a range of nitrating agents.