Bidentate N-ligand-assisted gold redox catalysis with hydrogen peroxide

Abstract

Gold redox catalysis, which exploits the ability of strong π-acid activation in combination with redox reactions, has emerged as an attractive synthetic method with unique reactivities compared to other transition metals. However, gold redox chemistry bears the challenge to overcome the high redox potential of Au(I)/Au(III) (1.41 V). The classical strategy of gold redox catalysis applies strong external chemical oxidants which inevitably results in low atom economy and substrate limitations due to incompatibility with functional groups. Here we report a bidentate N-ligand (for example, Phen, Bpy) assisted gold redox catalysis using H₂O₂ as oxidant, which proved to be generally applicable for many forms of coupling reactions. In addition, C(sp²)–C(sp²) bicyclization coupling (cross-coupling of two cyclized substrates) is accessible under our conditions. Mechanistic studies reveal a redox elimination process in which a bidentate N-ligand is crucial for the catalytic cycle. The formation of alkynyl-Au^III–OH and vinyl-Au^III–OH species is the key process for the synergistic π-bond activation and Au^I oxidation.