Synthetic routes of azo derivatives: A brief overview

Azo compounds are important class of compounds and have verstile applications in various fields of life. Because of their broad range of applications, it is necessary to have versatile methods of synthesis to have new azo derivatives in good yields. This review covers the synthetic methodology with emphasis on the classical and versatile ones. The overall feasible methods for azo compounds synthesis mentioned in this review includes, diazotization/azo coupling, solvent free-silica supported boron trifluoride, methyl nitrite-active iron based-Japp-Kalingemann, Novartis/Ciba-Geigy-Cupric chloride catalyzed-Mild one-pot two step-nitroamatics and anilines-deoxygenation of nitrobenzene-decomposition of N,N, Ortho para benzoquinonediimines dioxide dehydrogenation, arylhydrazines dimerization reaction of diazonium salts-metal catalyzed coupling, Opening of benzotriazoles-Oxidation of anilines-arylcalcium and nitrous oxide-quinone acetals and arylhydrazines-quinones, reduction of azoxybenzenes and azo-MOFs, etc, which yield azo compounds in good to moderate yields . The most widely used methods to synthesize azo compounds are by Mills reaction and azo coupling which are important in industrial point of view and are extensively used worldwide. Though there are various reported methods to get azo compounds but they have limitations as well. Therefore there is still a need to have latest and efficient methods keeping in view the advantages and disadvantages of above mentioned methods in order to have innovative and more efficient method for synthesis of azo compounds.