FACILE SYNTHESIS OF ISOXAZOLES AND PYRAZOLES FROM SS-Diketohydrazones

Abstract

-pyrazoles may be obtained by reaction of 3-[2-(R 1 -phenyl)hydrazono)]pentane-2,4-dione with H 2 NOH·HCl and R 2 -4-C 6 H 4 -NHNH 2 , respectively. The reactions were performed in ethanol as solvent and catalyzed by glacial acetic acid.

Dimers linked by type-I C—F...F—C contacts in (Z)-3-methyl-4-[2-(4-methylphenyl)hydrazinylidene]-1-(pentafluorophenyl)-1H-pyrazol-5(4H)-one

“…Ethyl (Z)-3-oxo-2-(2-p-tolylhydrazinylidene)butanoate was prepared according to the method recommended in the literature (Yao, 1964;Bertolasi et al, 1999;Bustos, Sá nchez, Martínez et al, 2007;Bustos et al, 2009) and recrystallized from ethanol. Solvents (EtOH, CHCl 3 , CDCl 3 and glacial acetic acid) were provided by Merck and perfluorophenylhydrazine was provided by Aldrich.…”

3,5-Dimethyl-4-[(E)-(2-nitrophenyl)diazenyl]-1-(2,3,4,5,6-pentafluorophenyl)-1H-pyrazole

“…Pyrazole compounds have also been used as ligands for obtaining transition metal complexes, since their heterocyclic nuclei may coordinate to the metal directly via one or both of the vicinal N atoms (Rojas et al, 2004). In a previous paper, we reported preliminary results of the synthesis of a large library of pyrazoles by reaction of -diketohydrazones with substituted arylhydrazines (Bustos et al, 2009). We present here the structure of a new member of this family, the title compound, (I), and compare it with that of the previously reported 3,5-dimethyl-4-[(E)-(4-nitrophenyl)diazenyl]-1-(2,3,4,5,6-pentafluorophenyl)-1H-pyrazole, (II) (Bustos et al, 2007).…”

On substituted pyrazole derivatives. I. 3-Methyl-4-[(Z)-2-(4-methylphenyl)hydrazin-1-ylidene]-1-(3-nitrophenyl)-1H-pyrazol-5(4H)-one and 3-methyl-4-[(Z)-2-(4-methylphenyl)hydrazin-1-ylidene]-1-[4-(trifluoromethyl)phenyl]-1H-pyrazol-5(4H)-one

“…Ethyl (Z)-3-oxo-2-(2-ptolylhydrazinylidene)butanoate was prepared according to the method recommended in the literature (Yao, 1964;Bertolasi et al, 1999;Bustos et al, 2009) and was recrystallized from ethanol. Preparation of the precursor.…”

“…Considering the synthetic route, we have been able to obtain two 4-hydrazinylidene-substituted 1H-pyrazol-5-ones [see a and b in Scheme 1 (top) (Bustos et al, 2009), where a is in principle a more rigid structure than b]. The hydrazinylidene group in a may generate diazene-hydrazinylidene tautomers, in both of which the keto O atom acts as an acceptor.…”