Nanocrystalline silica-H2SO4 as an efficient Heterogeneous catalyst for the synthesis of 2/-aminobenzothiazolo-arylmethyl-2-naphthols under solvent-free conditions

With the development of green chemistry, solid acid catalysts have received much attention for green catalytic procedures with advantages of no pollution, easy separation and reusability. However, compare with the catalytic activities of traditional protonic acids such as H2SO4 etc, that of the solid acid catalysts were always not good enough mostly because of the lower acid density and strength. For decades’ researchers in this field around the world has been committed to improve the acid density and strength as well as the stability of solid acids. In addition, there is a several interest in heterogeneous system because of its importance in industry and in developing technologies [1-3]. In this paper, nanocrystalline silica-H2SO4, as a newly reported catalyst, has been used as an efficient and reusable catalyst for the synthesis of 2/-aminobenzothiazolo-arylmethyl-2-naphthols with using benzothiazol-2-amine, 2-naphthol, aromatic aldehydes [4]. In practice, this method is a combination of a satisfactory synthesis and more significantly easy product isolation and purification. A simple, high yielding in the presence of nanocrystalline silica-H2SO4 as a catalyst is described. The catalyst could be used at least five times without any change in the activity. Full characterization of the catalyst was performed by XRD, IR, TGA spectra and also by FE-SEM images