Nitroacetic Esters in the Regioselective Synthesis of Isoxazole-3,5-dicarboxylic Acid Derivatives

An efficient and high-yielding strategy to prepare “unsymmetrical”
4-aryl-isoxazol-3,5-dicarboxylic acid derivatives from nitroacetic
esters and aromatic aldehydes has been developed. The strategy is
based on the isolation and usage of the previously missed intermediate
of the Dornow reaction5-hydroxy-6-oxo-4-aryl-6H-1,2-oxazine-3-carboxylates. In addition, the mechanism of the Dornow
reaction was partially revised.