Synthesis of 4-(acylacetyl)-1-phenyl-2-pyrazolin-5-ones from 3-acyl-2H-pyran-2, 4 (3H)-diones. Their synthetic applications to functionalized 4-oxopyrano [2, 3-c] …
Some years ago, the formation of 3, 6-dimethyl-1-phenyl-4-oxopyrano [4, 3-c] pyrazole (mp 158 OC)(3) and 5-hydroxy-3-methyl-l-phenyl-4-(3-methyl-1-phenylpyrazol-5-y1) pyrazole (mp 260" C)(4) was rep~ rted.~,~ Surprisingly, in a more recent paper, 5 5-anilino-3, 6-di- methyl-4-oxo-l-phenylpyrazolo [4, 3-c] pyridine (5)(named as pyridinopyrazole by the authors) was described from the reaction of dehydroacetic acid (la) and phenylhydrazine ( ...