Nano-SnCl4/SiO2 as a Green and Reusable Catalyst for the Synthesis of Azo Dyes Based on 2- Naphtol under Grinding Conditions

It is well known that azo compounds are the most widely class of industrial synthesized organic dyes due to their versatile application in various fields, such as dyeing textile fibers, biological and pharmacological properties[1]. Azo dyes are generally synthesized in two steps: the diazotization of aromatic primary amines, followed by the coupling reaction between diazonium salts and activated aromatic compounds [2]. Previously, aromatic amines have been converted to diazonium salts in the presence of NaNO2 and a mineral acid at 0-5 °C[3]. Herein, we wish to report a convenient and one-pot method for diazotization and diazo coupling reaction with 2-naphoi by using nano-SnCl4/SiO2 under solvent-free conditions by grinding (Scheme1).The advantages of this work are simple work-up, mild condition, short reaction time and high yields.