Preyssler heteropolyacid supported on silica coated NiFe 2 O 4 nanoparticles for the catalytic synthesis of bis(dihydropyrimidinone)benzene and 3,4-dihydropyrimidin-2(1 H )-ones

A novel magnetic acidic catalyst comprising Preyssler (H 14 [NaP 5 W 30 O 110 ]) heteropoly acid supported on silica coated nickel ferrite nanoparticles (NiFe 2 O 4 @SiO 2 ) was prepared. The catalyst was characterized by Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive spectrum, VSM and particle size neasurement. Its catalytic activity was investigated for the synthesis of bis(dihydropyrimidinone)benzene and 3,4-dihydropyrimidin-2(1 H )-ones derivatives by the Biginelli reaction. With the catalyst, the reactions occurred in less than 1 h with good to excellent yields. More importantly, the catalyst was easily separated from the reaction mixture by an external magnet and reused at least five times without degradation in the activity.