Homogeneous copper-catalyzed aerobic oxidation of alcohols and aldehydes: mechanistic insights and recent advances.

Abstract

Copper-catalyzed aerobic oxidation of alcohols and aldehydes has become a key transformation for the sustainable synthesis of carbonyl compounds, combining high efficiency with the use of molecular oxygen as a benign terminal oxidant. Owing to its earth-abundance, low cost, low toxicity, and versatile redox properties, copper offers a compelling alternative to traditional noble metal catalysts and stoichiometric oxidation methods. This review highlights the evolution of copper-catalyzed aerobic oxidation of alcohols, emphasizing two distinct mechanistic regimes: nitroxyl radical-mediated systems and nitroxyl-free pathways, in which copper-ligand complexes directly promote dioxygen activation and substrate oxidation. Methods for conversion of aldehydes to carboxylic acids were also discussed. Apart from historical overview of the considered protocols, recent advances in the field were deliberated. Despite significant progress, the development of simpler, mediator-free catalytic systems based on readily available reagents remains a central challenge and a promising direction for future research.