In situ generated iridium nanoparticle-catalyzed highly efficient hydrogenation of nitroarenes.

The catalytic hydrogenation of nitroarenes to anilines is a pivotal transformation, often hindered by the formation of hazardous intermediates and the need for substantial catalyst loadings under mild conditions. In this study, we demonstrate that the commercially available pre-catalyst [Ir(COD)Cl]2 facilitates this transformation with remarkable efficiency (substrate-to-catalyst molar ratio S/C = 1000-100 000) under mild conditions (50 °C, 60 atm H2), through the in situ generation of the active Ir nanoparticle (NP) catalyst. This system achieves quantitative conversion and exceptional isolated yields (up to 99%) across 42 diverse functionalized nitroarenes, including substrates bearing halogens, esters, nitriles, and acetyl and other reducible groups. Mechanistic investigations confirm a direct hydrogenation pathway, effectively suppressing N-N-coupled byproducts. Its practical utility is demonstrated through gram-scale and solvent-free applications. This work establishes a scalable, efficient, and impurity-free benchmark for the synthesis of functionalized anilines.