JOURNAL OF HETEROCYCLIC CHEMISTRY

1,5-Diphenyl-1H-pyrazole-3,4-(dicarboxylic acid-4-ethyl ester 2, obtained from the 4-ethoxycarbonyl-5phenyl-2,3-furandione 1 and N-benzylidene-N'-phenyl hydrazine, was converted via reactions of its acid chloride 3 with various alcohols or N-nucleophiles into the corresponding ester 5 or amide derivatives 6, respectively. In addition, 2 was decarboxylated to give ethyl 1,5-diphenylpyrazole-4-carboxylate 4. Nitrile 7 derivative of 2 was also obtained by dehydration of 6a in a mixture of SOCl2 and DMF. While cyclo condensation reaction of 2 with hydrazine hydrate leads to the formation of pyrazolo[3,4d]pyridazine-4,7-dione 8, the reaction of 3 with anhydrous hydrazine provided a new bis pyrazole derivative 9