H4 [W12SiO40] grafted on magnetic chitosan: A green nanocatalyst for the synthesis of [1,2,4]triazolo/benzimidazolo quinazolinone derivatives

A novel nanocomposite, H4SiW12O40 immobilised magnetic chitosan (HSiW-MC) was prepared via a facile procedure in one-pot fashion. This composite was fully characterised using several methods including, Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and scanning electron microscopy. It was applied as a novel catalyst in two three components reaction involving, dimedone, differently substituted aryl aldehydes and either 3-amino-1,2,4-triazole or 2-amino benzimidazole to afford the corresponding [1,2,4]triazolo/benzimidazolo quinazolinone derivatives. It showed excellent performance in the aforementioned reaction with the high yield of 96%. Also, the effect of HSiW-MC amount, catalysts, solvents and temperatures were studied and the best results were obtained in CH3CN in the presence of HSiW-MC (0.04 g) under refluxing conditions