CoFe2O4@SiO2: A magnetically recyclable heterogeneous catalyst for the synthesis of spirooxindole derivatives

We described the characterization, preparation, and catalytic application of CoFe2O4@SiO2 nanoparticle. The characterization was done using transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX), and Fourier transform infrared (FT-IR) analyses. Using Scherrer's approximation and powder X-ray diffractometry (XRD), an average crystallite size is determined from the full width at half the maximum of the strongest reflection. In the synthesis of spirooxindoles of malononitrile, various isatins with 1,3-dicarbonyl compounds, The CoFe2O4@SiO2 efficiency is investigated. Good to excellent yields are observed in the coupling products, which was in result of excellent catalytic activity of the nanocatalyst. Furthermore, at least five times of the recoverability and reusability of CoFe2O4@SiO2 without any apparent decrease in the activity and selectivity are confirmed. This confirmed the high efficiency and stability of the nanocatalyst under the reaction conditions and during the recycling stages. (c) 2019 Elsevier B.V. All rights reserved.