Magnetically recoverable ferromagnetic 3D hierarchical core-shell Fe3O4@NiO/Co3O4 microspheres as an efficient and ligand-free catalyst for C–S bond formation in poly (ethylene glycol)

Abstract

ABSTRACT A simple and efficient protocol for the synthesis of diaryl thioethers from the reaction of thiourea with a wide variety of aryl halides, including aryl iodides, aryl bromides and aryl chlorides in the presence of 3D hierarchical core-shell Fe3O4@NiO/Co3O4 microspheres has been described. This reaction enables the one-pot synthesis of diaryl thioethers in good to high yields using a non-toxic and magnetically separable catalyst in PEG-400 as an eco-friendly, safe, inexpensive and thermally stable solvent. Magnetic separation and reusability of catalyst for eight times without any significant loss of activity, the use of a commercially available, eco-friendly, cheap and chemically stable sulfur transfer agent and solvent, operational simplicity, environmentally benign, easier work-up procedure and cost efficiency make this method a promising candidate for potential applications in some organic reactions. The catalytic activity of Fe3O4@NiO/Co3O4 as a novel and inexpensive catalyst was investigated in the C-S cross coupling reaction.