New 1-Substituted 4-Cinnamoyl-5- hydroxypyrazoles and Precursors thereof: Synthesis, Ring Closure Reactions and NMR-Spectroscopic Investigations
作者:Wolfgang Holzer、Ingrid Krca
DOI:10.3987/com-03-9857
日期:——
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.
Heinisch, Gottfried; Hollub, Christian; Holzer, Wolfgang, Journal of Heterocyclic Chemistry, 1991, vol. 28, # 4, p. 1047 - 1050
作者:Heinisch, Gottfried、Hollub, Christian、Holzer, Wolfgang