Aminations of Aryl Halides Using Nitroaromatics as Coupling Partners: Overcoming the Hydrodehalogenation Pathway under a Hydrogen Atmosphere in Water

: A novel catalytic aqueous micellar technology has been developed for the C-N cross-coupling of nitroarenes with aryl halides. The catalytic cycle involves in-situ reduction of nitroaromatics and subsequent coupling of resulting amine with aryl halide, while avoiding undesired hydrodehalogenation of aryl halide. The bimetallic palladium-copper (Pd-Cu) nanocatalyst configuration in aqueous micelles facilitates the amination pathway selectively, possibly through in-situ formation of Cu-hydride species. These species prevent Pd-hydride-mediated hydrodehalogenation. The nanocata-lyst has been thoroughly characterized using various spectroscopic and imaging tools, including 31P and 1H nuclear magnetic resonance, X-ray absorption spectroscopy (XAS), and high-resolution transmission electron microscopy. The oxidation states of Cu and Pd have been verified using X-ray photoelectron spectroscopy, while metal-metal and metal-ligand contact has been confirmed by XAS. Control experiments have been performed to determine the significance of aqueous micelles and each constituent of the nanocatalyst on the desired reaction pathway. As revealed by control mass spectrometry, the reaction pathway does not involve azo- or nitroso-type intermediates. The catalytic methodol-ogy can be applied to numerous substrates with excellent functional and protecting group tolerance. The scalability of this method has been demonstrated in a gram-scale reaction.