Abstract The reaction of ethyl 2-(dimethylamino) methylene-3-oxobutanoate with diethyl oxalate in the presence of sodium hydride in THF gave diethyl 4-oxo-4H-pyran-2, 5- dicarboxylate, from which 4-oxo-4H-pyran-2, 5-dicarboxylic and 4-oxo-1-phenyl-1, 4- dihydropyridine-2, 5-dicarboxylic acids and their derivatives were obtained in good yields.
