Metal-Free Oxidation of Aldehydes to Carboxylic Acids

Metal-Free Oxidation of Aldehydes to Carboxylic Acids 

Aromatic and aliphatic aldehydes have been successfully oxidized to their corresponding carboxylic acids by the use of a H2O2/HCI system in the presence of hydroxylamine hydrochloride (Eq. (10.2)) [9]. The method is selective and tolerates the presence of other functional groups such as, carbon-carbon double bonds, hydroxyl groups, and other heteroatoms. 

Metal-Catalyzed Oxidation oTAldehydes to Carboxylic Acids 

An established procedure for the conversion of an aldehyde to a carboxylic add involves the use of Ag20 in the presence of NaOH [21, 22]. This has inspired researchers to employ different forms of Ag(I) compounds as catalysts in combination with an oxidant. Recently, a mild and selective method for the transformation of aldehydes into carboxylic acids with a silver catalyst was reported [23]. Thus, in the presence of 10 mol% AgN03 and 5 equiv. of 30% aq. H2O2 in acetonitrile at 50 °C, various aromatic, conjugated, and aliphatic aldehydes were readily oxidized to the corresponding carboxylic acids in good yields. 

The use of 150nm-size Ag20/CuO and CuO catalysts was found to catalyze the oxidation of aromatic and aliphatic aldehydes to their corresponding acids by molecular oxygen in good yields [24]. This method has been used in the industrial production of furoic acid, although the obvious choice in this case would be CuO because of easy collection and regeneration of the catalyst 

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