The Immobilized Zirconocene Chloride on Magnetite‐reduced Graphene Oxide: A Highly Efficient and Reusable Heterogeneous Nanocatalyst for One‐pot Three‐component Synthesis of Tetrahydrobenzo[b]pyrans and Dihydropyrano[3,2‐c]chromenes

Abstract

AbstractThe present paper describes the synthesis and characterization of the functionalized magnetite reduced graphene oxide (rGO@Fe3O4) with zirconocene dichloride as rGO@Fe3O4@ZrCp2Cl2. The prepared magnetic nanomaterial was characterized by Fourier‐transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), inductively coupled plasma optical emission spectroscopy (ICP‐OES) and mass spectrometry (MS). This new heterogeneous nanocatalyst showed the perfect catalytic activity towards synthesis of tetrahydrobenzo[b]pyran and Dihydropyrano[3,2‐c]chromenes derivatives through multicomponent reaction of dimedone or 4‐hydroxycoumarin, malononitrile and aromatic aldehydes in polyethylene glycol 400 (PEG‐400) at 100 °C. The influence of the amount of nanocatalyst, varying temperature of the reaction and the kind of solvent on the rate of condensation reaction was investigated. Recovery and reusability of the applied nanocatalyst was examined for five consecutive cycles without the significant loss of its catalytic activity.