33641-17-7Relevant articles and documents
New 1-substituted 4-cinnamoyl-5-hydroxypyrazoles and precursors thereof: Synthesis, ring closure reactions and NMR-spectroscopic investigations
Holzer, Wolfgang,Krca, Ingrid
, p. 2323 - 2342 (2007/10/03)
Reaction of 1-substituted 5-hydroxy-1H-pyrazoles (pyrazolones) with trans-cinnamoyl chloride / calcium hydroxide in dioxane affords the corresponding 4-cinnamoyl-5-hydroxy-1H-pyrazoles. Cyclization of the latter into 5,6-dihydropyrano[2,3-c]pyrazol-4-ones proceeds in very low yields upon treatment with concentrated sulfuric acid. 1,6-Diphenyl-1H-pyrano[2,3-c]pyrazol-4-one was synthesized by reaction of of 4-acetyl-5-hydroxy-1-phenyl-1H-pyrazole with benzoyl chloride and lithium bis(trimethylsilyl)amide and subsequent cyclization of the thus obtained 1,3-diketone. NMR-spectroscopic investigations with the obtained 4-substituted 5-hydroxypyrazoles and their precursors regarding their tautomeric behavior in various solvents are presented.
Method for producing 1-substituted 5-hydroxypyrazoles
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, (2008/06/13)
A process for preparing compounds of the formula I in which R1is hydrogen, an aliphatic group having 1-8 carbon atoms, C1-C6-alkoxycarbonyl, C1-C6-alkylthiocarbonyl or a cyclic ring system having 3-14 ring atoms, and R2is hydrogen, an aliphatic group having 1-8 carbon atoms, or R1and R2together with the carbon atom to which they are bound form a cyclic or bicyclic ring system having 3-14 ring atoms, comprises the preparation of compounds of the formula II ?in which R3and R4are readily detachable groups and R1and R2are as defined above, as starting materials or intermediates and the cyclization of these under suitable reaction conditions to give compounds of the formula I.
