OXIDATIVE DECARBONYLATION OF BETA-ARYLPYRUVIC ACIDS USING SODIUM PERBORATE

Oxidation of beta-aryl- and beta-heteroarylpyruvic acids using sodium perborate tetrahydrate (SPB) in aqueous solution at ambient temperatur e gives the corresponding arylacetic acids in good yield (68-86%). The mild conditions are convenient for the preparation of thermally unsta ble acids. In particular the method has been applied to the preparatio n of an unstable 5-nitroimidazol-2-yl ethanoic acid which could not be obtained using other reagents apparently due to enolisation of the py ruvic acid precursor. Attempts to achieve decarbonylation using calciu m hypochlorite or SPB in acidic solution lead to the 2-chloromethyl de rivatives. The novel 5-nitroimidazol-2-yl ethanoic acid, which was req uired as a precursor of molecules of biological interest, has been ful ly characterised and converted to a known amide. Reaction of this acid with Vilsmeier's reagent gave an enamine derivative and not the expec ted vinamidinium salt. This novel mode of reaction is attributable to intramolecular hydrogen-bonding and favourable conjugation. (C) 1998 E lsevier Science Ltd. All rights reserved.