Phosphotungstic acid supported on SiO2@NHPhNH2 functionalized nanoparticles of MnFe2O4 as a recyclable catalyst for the preparation of tetrahydrobenzo[b]pyran and indazolo[2,1-b]phthalazine-triones

Abstract

MnFe2O4@SiO2@NHPhNH2–phosphotungstic acid was synthesized by the reaction of diamine-modified silica coated manganese ferrite nanoparticles with H3PW12O40, the Keggin-type heteropoly acid. This is the first time that H3PW12O40 supported on diamine functionalized MnFe2O4 nanoparticles has been reported. The synthesized catalyst was characterized by various techniques, including Fourier Transform Infrared Spectroscopy (FTIR), Transmission electron-microscopy (TEM), X-ray Powder Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), Thermogravimetric Analysis (TGA), and Vibrating Sample Magnetometer (VSM). The synthesized nanoparticle was examined as the heterogenous nanocatalyst for the synthesis of tetrahydrobenzo-[b]-pyran derivatives and 2H-indazolo-[2,1-b]-phthalazine-triones under the solvent-free heating or ultrasonic irradiation conditions. This method offers several advantages including high yield, low reaction times, and the simple work-up procedure due to the presence of the magnetic nanoparticles in this catalyst, so that, it can be easily recovered and reused for at least six successive times without the loss of its high catalytic activity, suggesting its great Potential for industrial applications.