Immobilized antimony species on magnetite: a novel and highly efficient magnetically reusable nanocatalyst for direct and gram-scale reductive-coupling of nitroarenes to azoarenes.

In this study, magnetic nanoparticles of Fe 3 O 4 @SbF x from the immobilization of SbF 3 on magnetite were synthesized. The prepared nanocomposite system was then characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, vibrating sample magnetometry and inductively coupled plasma optical emission spectroscopy. Next, the catalytic activity of Fe 3 O 4 @SbF x MNPs was highlighted by one-pot reductive-coupling of aromatic nitro compounds to the corresponding azoarene materials with NaBH 4 . The reactions were carried out in refluxing EtOH within 6-25 min to afford the products in high yields. The reusability of the Sb-magnetite system was also studied for 6 consecutive cycles without significant loss of catalytic activity. This synthetic protocol provided several advantages in terms of introducing a novel catalytic system based on antimony species for direct and gram-scale preparation of azoarenes from nitroarenes, low loading of the nanocatalyst, mild reaction conditions, using ethanol as a green and economic solvent and high yield of the products.