Nano silica gel supported perchloric acidwet SiO2 an efficient reagent for one - pot synthesis of azo dyes based on 1-naphthol in room temperature and solventfree conditions

A convenient, rapid, and one-pot method for the synthesis of azo dyes based on 1-naphthol has been developed. In this protocol, diazotization reagent (ArN2+ -ClO4/nano SiO2) was prepared via grinding of aromatic amines, NaNO2, wet SiO2 and nano silicagel supported perchloric acid (nano-SPCA) 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+ -ClO4/nano SiO2 with 1-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.