• Archives of Pharmacal Research
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• v.14 no.3
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• pp.237-241
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• 1991

The tautomerism in 3-phenyl-4-arylazo-5-isoxazolones 1 was examined by $^1H-NMR$ spectra of $^15N-labeled$ compound and by HMO method. Both spectra data $(^1H-NMR\;and\;IR)$ and bonding energies are in support of the assignment of the hydrazone structure to such compounds. It is further shown that intermolecular and intramolecular hydrogen bondings favor the hydrazone tautomer.

• Journal of the Korean Chemical Society
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• v.56 no.1
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• pp.82-91
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• 2012

Novel azopyrazolin-5-one dyes 4a-f were synthesized by the regioselective reaction of phenylhydrazine with 2,3,4-chromantrione-3-arylhydrazones 2a-f. The acid dissociation constants $pK_a$ for the series prepared were determined and correlated by the Hammett equation. The results of such correlation together with the spectral data indicated that the studied compounds exist predominantly in the hydrazone keto structure, (D) as the Z-configuration. The dyes were applied to polyester fabrics, affording orange-yellow shades and assessments of their dyeing performance are considered. Further, the compounds 4a-f were screened for their antimicrobial activity against various microorganisms.

• Journal of the Korean Chemical Society
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• v.56 no.3
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• pp.348-356
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• 2012

In an attempt to find a new class of bisazo disperse dyes with better dyeing properties, a series of novel bisazo dyestuffs based on 4-arylhydrazono-3-(2'-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones $\mathbf{3a-f}$ were prepared by diazocoupling of p-nitrophenyl diazonium chloride with 4-arylhydrazono-3-(2'-hydroxyphenyl)-1-phenyl-2-pyrazolin-5-ones $\mathbf{2a-f}$. Compounds $\mathbf{3a-f}$ were subsequently reacted with acetic anhydride in the presence of p-toluenesulfonic acid afford the corresponding O-acetyl derivatives $\mathbf{4a-f}$. The latter products as well as spectral data indicated that compounds $\mathbf{3a-f}$ exist predominantly in the azo-hydrazone tautomeric form (H) as the ZE-configuration. Additionally, two series of the synthesized dyes $\mathbf{3a-f}$ and $\mathbf{4a-f}$ were applied as disperse dyes for dyeing polyester fabrics and their fastness properties were evaluated. Also the position of color in CIELAB coordinates ($L^*$, $a^*$, $b^*$, $H^*$, $C^*$*) was assessed.