Oxidative decarbonylation of β-arylpyruvic acids using sodium perborate

Article abstract of DOI:10.1016/S0040-4020(98)00518-3

Oxidation of β-aryl- and β-heteroarylpyruvic acids using sodium perborate tetrahydrate (SPB) in aqueous solution at ambient temperature gives the corresponding arylacetic acids in good yield (68-86%). The mild conditions are convenient for the preparation of thermally unstable acids. In particular the method has been applied to the preparation of an unstable 5- nitroimidazol-2-yl ethanoic acid which could not be obtained using other reagents apparently due to enolisation of the pyruvic acid precursor. Attempts to achieve decarbonylation using calcium hypochlorite or SPB in acidic solution lead to the 2 chloromethyl derivatives. The novel 5- nitroimidazol-2-yl ethanoic acid, which was required as a precursor of molecules of biological interest, has been fully characterised and converted to a known amide. Reaction of this acid with Vilsmeier's reagent gave an enamine derivative and not the expected vinamidinium salt. This novel mode of reaction is attributable to intramolecular hydrogen-bonding and favourable conjugation.