Copper‐Catalyzed Aerobic Oxidative Dehydrogenative Coupling of Anilines Leading to Aromatic Azo Compounds using Dioxygen as an Oxidant

Abstract

Aromatic azo compounds are ubiquitous motifs and are widely used in industry as organic dyes, indicators, pigments, food additives, radical reaction initiators, and therapeutic agents. Despite numerous efforts towards the synthesis of azo derivatives, big challenges still remain because: 1) the catalytic procedures that have been reported to afford high yields have been less widely explored; 2) stoichiometric and environmentally unfriendly oxidants, such as manganese salts, lead salts, mercury salts, or ferrates were previously employed for their preparation form aromatic amines; 3) unsymmetric aromatic azo compounds are not easy to prepare. Usually, two step syntheses are used, proceeding from anilines via diazonium salt or nitrosobenzene intermediates, using stoichiometric amounts of nitrite salts or other oxidants, to produce unsymmetric aromatic azo compounds, with inorganic salts as the by-products [Eq. (1)].