Gold-catalyzed direct hydrogenative coupling of nitroarenes to synthesize aromatic azo compounds.

The azo linkage is a prominent chemical motif which has found numerous applications in materials science, pharmaceuticals, and agrochemicals. Described herein is a sustainable heterogeneous-gold-catalyzed synthesis of azo arenes. Available nitroarenes are deoxygenated and linked selectively by the formation of N=N bonds using molecular H2 without any external additives. As a result of a unique and remarkable synergy between the metal and support, a facile surface-mediated condensation of nitroso and hydroxylamine intermediates is enabled, and the desired transformation proceeds in a highly selective manner under mild reaction conditions. The protocol tolerates a large variety of functional groups and offers a general and versatile method for the environmentally friendly synthesis of symmetric or asymmetric aromatic azo compounds.