5-Pyrazolones, 3-amino— from

Dyestuffs. The use of thiophene-based dyestuffs has been largely the result of the access of 2-amino-3-substituted thiophenes via new cycHzation chemistry techniques (61). Intermediates of type (8) are available from development of this work. Such intermediates act as the azo-component and, when coupled with pyrazolones, aminopyrazoles, phenols, 2,6-dihydropyridines, etc, have produced numerous monoazo disperse dyes. These dyes impart yeUow—green, red—green, or violet—green colorations to synthetic fibers, with exceUent fastness to light as weU as to wet- and dry-heat treatments (62-64). 

The class of 2-amino-4H-pyrans has been known for several decades. The first representatives 1 and 2 are from the late 1950s to the early 1960s. Spiro-conjugated pyranopyrazole 1 was obtained in studies on pyrazolone dyestuffs (56ACS587), while pyranopyranone 2 served as a precursor for the blood anticoagulant warfarin (62JOC3086). 

Diazo Components With Cycloammonium Groups. Polynuclear N heterocycles that carry an amino group in the carbocyclic aromatic ring can be diazotized and then joined to azo dyes by using aromatic or heterocyclic coupling components. Quatemization at the heterocyclic nitrogen atom may occur before or after coupling. The azo dye 43, from 2-methyl-5-aminobenzimidazole and l-phenyl-3-methyl-5-pyrazolone, used in the form of its hydrochloride, dyes paper and leather in clear yellow shades [130],... 

First, 1 2 metal complexes of (mainly mono-) azo dyes, without sulfonic or carboxylic acid groups, and trivalent metals (see Section 3.11). The metals are preferably chromium and cobalt nickel, manganese, iron, or aluminum are of lesser importance. Diazo components are mainly chloro- and nitroaminophenols or amino-phenol sulfonamides coupling components are (3-naphthol, resorcinol, and 1-phe-nyl-3-methyl-5-pyrazolone. Formation of a complex from an azo dye and a metal salt generally takes place in the presence of organic solvents, such as alcohols, pyridine, or formamide. An example is C.I. Solvent Red 8, 12715 [33270-70-1] (1). 

In the stepwise synthesis of the unsymmetrical complex dye 13 [ 70236-60-1] [10], the azo dye made from diazotized l-amino-2-hydroxy-5-nitrobenzene and 1-phenyl-3-methyl-5-pyrazolone and the 1 1 chromium complex obtained from 6-nitro-l-diazo-2-hydroxynaphthalene-4-sulfonic acid and 2-naphthol are heated together at 80 °C for 5 h. The adduct is salted out with NaCl. A black powder is obtained that dyes wool and leather in dark brown shades. The resulting colors are fast, particularly on shrink-resistant wool. 

Sulfonation of pritnuline-like color bases by the baking process yields sulfonic acids whose azo dye derivatives are more fast to light than those from sulfonic acids prepared in the ordinary way. It is assumed that in the baking process, the sulfo group enters ortho to the amino group, and that this increases the light fastness. This same principle was mentioned in connection with the pyrazolone dyes. 

The reaction of AI with hydrazines follows a complex pathway. Thus 5-amino-isoxazoles react with hydrazine to furnish a mixture of pyrazolone 83, 4-amino-pyrazol-5-one 84, and l-aminopyrazol-5-one 85 (72JHC1219). Bipyrazole 86 and isoxazole ring destruction product 87 were obtained from the reactions of 5-AI with phenylhydrazine (53JPJ387) and semicarbazide (54JPJ138), respectively. This issue seems to require reinvestigation however, these reactions have a complex nature and... 

In mordant dyes, phenols, naphthols, and enolizable carbonyl compounds, such as pyrazolones, are generally the couplers. As a rule, 2 1 metal complexes are formed in the afterchroming process. A typical example of a mordant dye is Eriochrome Black T (18b) which is made from the important dyestuff intermediate nitro-l,2,4-acid, 4-amino-3-hydroxy-7-nitro-l-naphthalenesulfonic acid [6259-63-8]. Eriochrome Red B [3618-63-1] (49) (Cl Mordant Red 7 Cl 18760) (1,2,4-acid — l-phenyl-3-methyl-5-pyrazolone) is another example. The equilibrium of the two tautomeric forms depends on the nature of the solvent. 

Cyclocondensation of 3-methyl-l-(5-substituted-3-phenyl-lH-indol-2-ylcarbonyl)-5-(4fi)-pyrazolones with arylidene derivatives of malononitrile using a catalytic amount of triethylamine in refluxing ethanol affords heterocycle [ ]-fused 6-amino-4-aryl-5-cyano-4H-pyrans (14JHC303). Other fused 6-amino-4-aryl derivatives arise from the three-component reaction of benzaldehydes, active methylene compounds (malononitrile/ ethyl cyanoacetate) and 1,3-dicarbonyl compounds catalyzed by 1,8-diaz-abicyclo[5.4.0]undec-7-ene (DBU) in refluxing water (14JHC618). Similar pyrazole[f)]-fused derivatives are obtained from the reaction of benzaldehydes, malonitrile, and 3-substituted-2-pyrazolin-5-ones using sodium... 

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