Nano-gama-Al2O3.SbCl5; an efficient and heterogeneous solid acid for the synthesis of azo dyes based on 2-naphthol at room temperature

In recent decades, organic color chemistry is undergoing very exciting development as a result of the opportunities presented by dye applications in high technology fields: electronic devices, linear and nonlinear optics, reprography and sensors. In pharmaceutical, azo compounds are well known for antifungal, antiviral activity and some are useful as chemotherapeutic agents polymer [1]. Commonly, they are prepared by diazotization, a procedurein which a primary aromatic amine is treated with a source of nitrous acid. In spite of all precautions the formation of dark decomposition products due to the existence of nitrous acid and its aromatic amine is unavoidable, thus lowering the yield and also making the product difficult to isolate [2]. Antimony pentachloride (SbCl5), a thin, colored and fuming liquid, is used in industry and organic synthesis. Since Antimony pentachloride is a liquid with a high specific gravity which fumes in air and reacts with moisture to form HCl, its handling and usability in the liquid form is laborious, the supported form is indeed preferable. It has been claimed that the supported SbCl5 is a solid superacid [3]. Herein, we wish to report a convenient method for diazotizationand diazo coupling reactions by using nano-gama-Al2O3.SbCl5 at room temperature by grinding (scheme 1).