Nano-Fe3O4 -encapsulated silica particles bearing sulfonic acid groups as a magnetically separable catalyst for the green and efficient synthesis of 14-aryl-14H-dibenzo[a,i]xanthene-8,13-dione derivatives

Article abstract of DOI:10.1007/s11164-015-2073-7

In this research, an efficient and environmentally friendly (green) method for one-pot synthesis of xanthene derivatives was developed in the presence of Fe₃O₄@SiO₂-SO₃H nanoparticles. The functionalization of silica-coated Fe₃O₄ magnetite nanoparticles (Fe₃O₄@SiO₂) using chlorosulfonic acid was afforded by nano-Fe₃O₄ encapsulated-silica particles bearing sulfonic acid (Fe₃O₄@SiO₂-SO₃H) that could be applied as a reusable and efficient heterogeneous nanocatalyst. The multicomponent reactions of 2-hydroxy-1,4-naphthoquinone, β-naphthol and aldehydes were carried out under reflux conditions to obtain some 14-aryl-14H-dibenzo[a,i]xanthene-8,13-dione derivatives. Being a simple procedure with environmental benignness, excellent yields, short reaction times, simple purification and facile catalyst separation are the advantages of this protocol. Fe₃O₄@SiO₂-SO₃H was readily recovered using an external magnet and could be reused several times without significant loss of reactivity. The catalyst was fully characterized by vibrating sample magnetometry (VSM), Fourier transform-infrared (FT-IR) spectrometry, scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, energy dispersive X-ray spectroscopy (EDAX) and transmission electron microscopy (TEM).