Azo dyes are an important class of organic compounds contributing an impressive range of colors. They can tautomerize to azohydrazone, azo-imino, and azonium/ammonium. They are widelyused as colorants in the different products, for example paper, textiles, foodstuffs, leather and gasoline. Azo dyes are made by diazotization of a primary aromatic amine and reaction of generated diazonium salt with a nucleophile (electron-rich), rhodium-catalyzed regioselective C−N bond formation with azides, oxidative dimerization of aromatic amines using tert-butyl hypoiodite (t-BuOI) and redox-driven C-N bond fusion. However, these methods have the disadvantages such as strongly acidic and/or basic media, tedious work-up, heavy metal pollution and safety problems.
