New protocol of copper-catalyzed oxidative C(CO)C bond cleavage of aryl and aliphatic ketones to organic acids using O2 as the terminal oxidant

•Cu(NO3)2 could catalyze the oxidative CC cleavage of ketones to acids.•A wide range of ketones have good to excellent yields.•In situ NMR and EPR gave possible intermediates and mechanism.•Electrochemical study of copper salts in various solvents has been conducted.

Catalytic oxidation of CC bond is a key technology to transform petroleum-based as well as sustainable biomass feedstock into more valuable oxygenates. We herein describe a convenient and useful oxidation strategy of converting ketones into carboxylic acids using homogeneous copper catalyst without additives and with O2 as the terminal oxidant. A wide range of aryl and aliphatic ketones as well as β-O-4 lignin models were selectively oxidized to acids via CC bond cleavage. Mechanism studies by EPR and in situ NMR elucidate the principles of Cu/O2 reactivity that involves CH bond and O2 activation via a peroxide species. This provides an important foundation for expanding the scope of useful aerobic oxidation reactions using copper catalysts.

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