Synthesis of Heterocyclic Azo Dyes from Quinolin-8-ol

Abstract

Six derivatives of heterocyclic azo dyes were synthesized by coupling diazotized aniline and 4-nitroaniline with quinolin-8-ol, 5-nitrosoquinolin-8-ol and 5-nitroquinolin-8-ol respectively. Benzene diazonium salt and 4-nitrobenzene diazonium salt were prepared by treating aniline and 4-nitroaniline respectively with HNO₂ generated in situ from NaNO₂/HCl at 0-5^oC. 5-nitrosoquinolin-8-ol was prepared by treating a solution of quinoline-8-ol in conc. HCl/H₂O with solution of sodium nitrite at 0-4^o in an ice-salt bath. Oxidation of 5-nitrosoquinolin-8-ol with conc. HNO₃ at 17^o gave 5-nitroquinolin-8-ol. The dyes were of intense colouration. They were characterized by FT-IR, NMR and elemental analysis.

Keywords: Aniline; 4-nitroaniline; quinolin-8-ol; diazotization; nitrosation; oxidation; coupling reaction