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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