Hydrazine-mediated Reduction of Nitro and Azide Functionalities Catalyzed by Highly Active and Reusable Magnetic Iron Oxide Nanocrystals

Iron oxide (Fe3O4) nanocrystals generated in situ from an inexpensive and readily available iron source catalyze the reduction of nitroarenes to anilines with unparalleled efficiency. The procedure is chemoselective, avoids the use of precious metals, and can be applied under mild reflux conditions (65 or 80 degrees C) or using sealed vessel microwave heating in an elevated temperature regime (150 degrees C). Utilizing microwave conditions, a variety of functionalized anilines have been prepared in nearly quantitative yields within 2-8 min at 150 degrees C, in a procedure also successfully applied to the reduction of aliphatic nitro compounds and azides. The iron oxide nanoparticles are generated in a colloidal form, resulting in homogeneous solutions suitable for continuous flow processing. Selected examples of anilines of industrial importance have been prepared in a continuous regime using this protocol.