N-propylpiperazine sulfonic acid immobilized on Fe3O4 magnetic silica nanoparticles: an efficient and heterogeneous catalyst for the one-pot synthesis of 9H-xanthene or methylenediphenol derivatives under solvent-free conditions

The preparation of N-propylpiperazine sulfonic acid-functionalized Fe3O4-magnetic core–shell silica nanoparticles (Fe3O4/SiO2-Propyl-Pip-SO3H) as a new recoverable and heterogeneous nanocatalyst is described. The size, morphology and other properties of this catalyst were characterized using various techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, elemental analysis, vibrating sample magnetometery and acid–base titration. Moreover, we have examined the catalytic activity of these nano-sized particles for one-pot, efficient and facile synthesis of biologically active 9H-xanthene or methylenediphenol derivatives via three-component condensation reaction of xylenol and aldehydes under solvent-free conditions at 120 °C. This method provides many advantages such as high yields of products, short reaction times, waste free and mild reaction conditions. Also, this nanocatalyst can be easily recovered by an external magnetic field and can be reused for this condensation five times in succession without considerable loss of its catalytic activity.