NiFe2O4@SiO2–Cu as a novel and efficient magnetically recoverable nanocatalyst for regioselective synthesis of β-thiol-1,2,3-triazoles under benign conditions

Abstract

A green, mild and eco-friendly approach for the three component one-pot regioselective synthesis of 1,2,3-triazoles from thiiranes has been introduced in the presence of NiFe₂O₄@SiO₂–Cu as a new and recoverable nanocatalyst. First, the NiFe₂O₄ nanoparticles have been produced through a solid-state reaction of hydrated nickel sulfate, hydrated iron(III) nitrate, NaOH and NaCl salts, and then calcined at 700 °C. Next, in order to protect the ferrite particles from oxidation and aggregation, the NiFe₂O₄ was core-shelled using tetraethyl orthosilicate (TEOS) and converted to NiFe₂O₄@SiO₂. Finally, the novel NiFe₂O₄@SiO₂–Cu nanocomposite was successfully prepared by adding copper(II) chloride solution and solid potassium borohydride. The catalyst has been characterized by FT-IR, SEM, EDX, VSM, ICP-OES, TEM and XRD techniques. The 1,3-dipolar cyclization of 1,2,3-triazoles was performed successfully in water at room temperature in high yields. The recoverability and reusability of the heterogeneous NiFe₂O₄@SiO₂–Cu have also been investigated using VSM, SEM and FT-IR analyses. The catalyst was used four times in consecutive runs without considerable loss of activity. The presented procedure provides significant benefits such as using water as a green solvent, absence of hazardous organic solvents, high yields, benign conditions and recyclability of the magnetic catalyst.