Oxidative Cleavage of C−C Bonds in Non‐aromatic Oxygenates with Molecular Oxygen for Synthesis of Carboxylic Acids

Abstract Oxidative carbon‐carbon cleavage reactions of non‐aromatic oxygenates such as vicinal diols are reviewed. In comparison with aromatic oxygenates where the benzyl positions are easily oxidized, non‐aromatic alcohols are difficult to be oxidized. The use of excess base in combination with metal catalysts is a typical approach, and the oxidations of 1,2‐cyclohexanediol and dihydroxylated derivatives of oleic acid have been reported with good yields of (di)carboxylate. Oxidation under acidic conditions typically uses vanadium as a key component of catalyst. Vanadium alone is active in oxidation of hydroxyketones and not effective in oxidation of saturated alcohols and polyols. Oxidation of sugars to formic acid is catalyzed by vanadium. For the oxidation of vicinal diols, the combination of platinum and vanadium is effective. There are some recently‐discovered systems for carbon‐carbon dissociation reactions of 1,2‐difunctionalized compounds, such as 2‐methoxycyclohexanone oxidation to adipic acid with polyoxometalate catalysts. On the other hand, the progress of research in the oxidation of cyclohexanone to adipic acid, which is an important industrial process, is less rapid, and we commented on the situation.