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

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, beta-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).