Efficient Synthesis of 2-amino-4H-chromene Derivatives in the Presence of Piperazine-functionalized Fe<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub> Magnetic Nanoparticles as a New Heterogeneous Reusable Catalyst Under Solvent-free Conditions

Abstract

A new piperazine-functionalized Fe3O4/SiO2 magnetite nanoparticle was synthesized through the surface modification of magnetic iron oxide nanoparticles by piperazine. Iron oxide nanoparticles were synthesized by coprecipitation method and the surface modification process was achieved by treating the nanoparticles with tetraethyl orthosilicate (TEOS), chloropropyl trimethoxy silane (CPTS) and piperazine. The developed functionalized iron oxide nanoparticle was evaluated as a reusable heterogeneous organobase catalyst for the synthesis of 4H-chromene derivatives from multi-component condensation reaction of 2-naphthol, malononitrile and aldehydes under solvent-free conditions. To receive morphological and structural information on the as-prepared catalyst, the samples were investigated by various techniques such as FT-IR, TEM, XRD, vibrating sample magnetometry (VSM), TGA and elemental analyzer. Under appropriate conditions, all reactions afforded the desired products in good to excellent yields. Moreover, this catalyst can be easily recovered by using a magnetic field and directly reused for at least six runs without significant loss of its activity.