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Paper | Regular issue | Vol 34, No. 8, 1992, pp.1547-1554
Published online, 1st January, 1970
DOI: 10.3987/COM-92-6038
Structure Determination of Some Pyronylpyrazoles, Correction of the Structures Described as Pyrano[4,3-c]pyrazoles

Ana Brbot-Saranovic,* Branka Katusin-Razem, and Ivan Vickovic

*Department of Chemistry and Biochemistry, Veterinary Faculty, University of Zagreb, Croatia


Reaction of ethyl 2-hydroxy-4-(4-hydroxy-6-methyl-2-pyron-3-yl)-4-oxo-2-butenoate (1) with phenylhydrazine has been reported to give four products. The corrected structures (4 and 5) were subsequently established for two of them, which had been reported previously as 3,5-disubstituted N-phenylpyrazole-4-carboxylic acids (8, 9). Consequently, the structures of their cyclized products, instead of the reported pyrano[4,3-c]pyrazoles (10, 11) are pyronylpyrazoles (6, 7). The structure (6) was also confirmed by means of X-ray crystallography.