Oxidation of Aromatic Side Chains
Oxidation of Aromatic Side Chains: Laboratory Application
Control of this oxidation is only possible within limits. For example, long-chain substituents on benzene can be fully oxidized to benzoic acid using potassium permanganate. Potassium permanganate oxidation of aromatic compounds substituted with multiple alkyl substituents leads to the corresponding polycarboxylic acids. The same reaction carried out with oxygen as oxidizing agent and Co2+ as catalyst gives a monocarboxylic acid.
However, using tetraalkylammonium permanganate (e.g. with KMnO4 and a tetraalkylammonium salt) under controlled conditions, a substituted aromatic compound can be partially oxidized. The reaction is being carried out in organic solvents.
Oxidations using this methodology show little selectivity. For example, the use of potassium permanganate during the oxidation of multiple-substitued aromatic compounds leads to the corresponding polycarboxylic acid.
Since the oxidation is carried out under drastic conditions, readily oxidizable groups such as amino, hydroxy and others have to be protected.