Nano silica chromic acidwet SiO2 and NaNO2 as an efficient reagent for one-pot synthesis of azo dyes based on 2-naphthol at room temperature under solventfree conditions

A convenient, rapid, and one-pot method for the synthesis of azo dyes has been developed. In this protocol, diazotization reagent (ArN2+ -CrO3–SiO2) was prepared via grinding of aromatic amines, NaNO2, wet SiO2 and nano silica chromic acid (Nano-SCA) without solvent at room temperature. The obtained diazotization reagent, was sufficiently stable to be kept at room temperature in the dry state for long time. Azo dyes, were prepared by coupling of ArN2 + -CrO3–SiO2 with 2-naphthol in good to excellent yields. Mild and heterogeneous reaction conditions, high stability of diazonium salt, easy procedure, short time of reaction and high yields are some important advantages of this protocol.