Abstract: Tetrahydro-6-oxo-3-pyridazinecarboxylic acid(I) was obtained by the condensate of α-oxoglutaric acid with hydrazine hydrate.Iwas dehydrogenated to give 1,6dihydro-6-oxo-3-pyridazinecarboxylic acid(Ⅱ).Under the phase transfer catalysis,Ⅲ and Ⅳwere converted into corresponding N₁-substituted-1,4,5,6-tetrahydro-6-oxo-3-pyridazinecarboxylic acids(Ⅴ)and N₁-substituted-1,6-dihydro-6-oxo-3-pyridazinecarboxylic acids(Ⅵ),which then condensated with ethyl ester of γ-amino butyric acid.Ten ethyl esters of γ-[N₁-substituted-1,4,5,6-tetrahydro(or 1,6-dihydro)-6-oxo-3-pyridazinamide]butyric acid(Ⅶa c and Ⅷa e)were synthesized. All compounds synthesized here have not been found in the literature.

Key words: xo-3-pyridazinecarboxylic acid, Derivatives of pyridazine, Phase transfer catalysis reaction(PTC)