Theophylline Supported on Modified Silica-Coated Magnetite Nanoparticles as a Novel, Efficient, Reusable Catalyst in Green One-Pot Synthesis of Spirooxindoles and Phenazines

In the present work, theophylline immobilized on superparamagnetic Fe3O4@SiO2 nanoparticles were prepared via a multistep method and was fully characterized by means of fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), vibration sample magnetometry (VSM), N-2 adsorption-desorption isotherm analysis, temperature-programmed desorption of carbon dioxide (CO2-TPD) and elemental analysis. The catalytic performance of this novel nanomagnetic catalyst has been studied in the synthesis of spirooxindole derivatives via a one-pot three-component reaction of isatin derivatives, malononitrile or ethyl 2-cyanoacetate, and 5-amino-1,3-dimethyluracil in excellent yields under reflux conditions in water. Also, the highly efficient, green and economical synthesis of poly-substituted benzo[a]pyrano-[2,3-c]phenazine derivatives from four component reaction of 2-hydroxynaphthalene-1,4-dione, diamines, aldehydes, and malononitrile in the presence of this basic magnetic catalyst has been developed. In addition, the used catalyst could be separated conveniently from the reaction system for up to 6 runs without significant loss of its catalytic efficiency.