| Popis: |
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 |
