Reaction 6-arylazo

The reaction is very common in pyrazolone chemistry. Since alkoxypyrazoles and tautomerizable pyrazolones undergo this reaction and 3-pyrazolin-5-ones, like antipyrine, do not, it is assumed that the reaction takes place at C-4 of the OH tautomer. Pyrazolone diazo coupling is an important industrial reaction since the resulting azo derivatives are used as dyestuffs. For instance, tartrazine (Section 4.04.4.1.3) has been prepared this way. 3,5-Pyrazolidinediones react with aryldiazonium salts resulting in the introduction of a 4-arylazo group. As has been described in Section 4.04.2.1.4(v), diazonium salts couple in the 3-position with indazole to give azo compounds. 

Coumarin, 7-amino-7-(diethylamino)-, I, 333 Coumarin, 7-amino-4-methyl-fluorescence spectra, 3, 601 Coumarin, 7-amino-3-phenyl-brightening agents, I, 339 Coumarin, 4-aryl-occurrence, 3, 677 synthesis, 3, 810 Coumarin, 3-arylazo-4-hydroxy-structure, 3, 643 Coumarin, 3-bromo-reactions... 

Jap-KIingermarm reactions, 4, 301 oxidation, 4, 299 reactions, 4, 299 synthesis, 4, 362 tautomerism, 4, 38, 200 Indole, 5-amino-synthesis, 4, 341 Indole, C-amino-oxidation, 4, 299 tautomerism, 4, 298 Indole, 3-(2-aminobutyl)-as antidepressant, 4, 371 Indole, (2-aminoethyl)-synthesis, 4, 278 Indole, 3-(2-aminoethyl)-synthesis, 4, 337 Indole, aminomethyl-reactions, 4, 71 Indole, 4-aminomethyl-synthesis, 4, 150 Indole, (aminovinyl)-synthesis, 4, 286 Indole, 1-aroyl-oxidation, 4, 57 oxidative dimerization catalysis by Pd(II) salts, 4, 252 Indole, 1-aroyloxy-rearrangement, 4, 244 Indole, 2-aryl-nitration, 4, 211 nitrosation, 4, 210 synthesis, 4, 324 Indole, 3-(arylazo)-rearrangement, 4, 301 Indole, 3-(arylthio)-synthesis, 4, 368 Indole, 3-azophenyl-nitration, 4, 49 Indole, 1-benzenesulfonyl-by lithiation, 4, 238 Indole, 1-benzoyl photosensitized reactions with methyl acrylate, 4, 268 Indole, 3-benzoyl-l,2-dimethyl-reactions... 

Boulton-Katritzky rearrangement, 5, 258 Pyrazol-5-one, 4-arylazo-reactions, 5, 262 Pyrazol-5-one, 4-arylidene-configuration, 5, 208... 

Pyrimidine, I-alkyl-2-methyltetrahydro-C-thioacylation, 4, 807 Pyrimidine, 4-alkylsulfinyl-nucleophilie displaeement reaetions, 3, 97 Pyrimidine, 6-alkylsulfinyl-nucleophilic displacement reactions, 3, 97 Pyrimidine, 2-alkylsulfonyl-nueleophilie displaeement reactions, 3, 97 Pyrimidine, 4-alkylsulfonyl-nucleophilic displacement reactions, 3, 97 Pyrimidine, 6-alkylsulfonyl-nucleophilie displaeement reactions, 3, 97 Pyrimidine, alkylthio-dealkylation, 3, 95 desulfurization, 3, 95 oxidation, 3, 96 synthesis, 3, 135, 136 Pyrimidine, 2-alkylthio-aminolysis, 3, 96 hydrolysis, 3, 95 Prineipal Synthesis, 3, 136 Pyrimidine, 4-alkylthio-aminolysis, 3, 96 hydrolysis, 3, 95 Pyrimidine, 6-alkylthio-aminolysis, 3, 96 hydrolysis, 3, 95 Pyrimidine, 4-allenyloxy-rearrangement, 3, 93 Pyrimidine, 4-allyloxy-2-phenyl-rearrangement, 3, 93 Pyrimidine, 4-allynyloxy-rearrangement, 3, 93 Pyrimidine, 4-anilino-2,5,6-trifluoro-NMR, 3, 63 Pyrimidine, 2-aryl-pyrroleaeetic aeid from, 4, 152 Pyrimidine, arylazo-synthesis, 3, 131 Pyrimidine, 4-arylazo-reduetion, 3, 88... 

Pyrimidine, 5-arylazo-reduction, 3, 88 Pyrimidine, aryloxy-hydrolysis, 3, 91 Pyrimidine, arylthio-desulfurization, 3, 95 Pyrimidine, azido-reactions, 3, 82... 

Thiazolin-5-one, 2-alkoxy-4-arylazo-rearrangements, 5, 777 2-Thiazolin-5-one, 4-methyl-2-phenyl-protomeric equilibrium, 6, 249 4-Thiazolin-2-one, 4-aryl-reactions, 6, 286 4-Thiazolin-2-one, 3,4-dimethyl-protonation, 6, 286 4-Thiazolin-2-one, 4-methyl-reactions, 6, 286 Thiazolinones electrophilic attack, 5, 99 Thiazolin-2-ones IR spectroscopy, 6, 241 nucleophilic displacement, 5, 100 2-Thiazolin-4-ones reactions, 6, 287 2-substituted synthesis, 6, 306 synthesis, 5, 129 6, 309, 310 tautomerism, 6, 248 2-Thiazolin-5-ones IR spectroscopy, 6, 242 reactions, 6, 288 synthesis, 5, 138 tautomerism, 6, 249 4-Thiazolin-2-ones synthesis, 6, 314 4-Thiazolin-3-ylacetic acid esters... 

The conversion of a 4-arylazo-5-oxazolone into a 1,2,4-triazole by reaction with a Grignard reagent is mentioned in Section II, B, 3. In HiTnilar fashion, the rearrangement of compound 30 to derivatives of 3-carboxy-l,5-diphenyl-lfl -l,2,4-triazoles (40) proceeds readily in the presence of strong nucleophiles [Eq. (26)]. This transformation undoubtedly occurs by ring opening and dehydrative cychzation, and, indeed, the acyclic amide and hydrazide 41 have been isolated. ... 

Ravindranath and co-workers studied the electrochemical behavior of 5-amino-2-phenyl-4-arylazo-l,2-dihydro-3//-pyrazol-3-one (90UC864) and 5-methyl-4-arylazo-2-(pyridin-2-ylcarbonyl)-2,4-dihydro-3//-pyrazol-3-(Mie (90IJC895). Similar studies were undertaken by Jain and Damodharan of pyrazol-3-ones 408a-f (95CJC176) (Scheme 94). The underlying rationale for this study on the electrochemical reduction of these biologically important pyrazol-3-ones is that it can lead to information on the reaction routes and mechanisms of biological redox reactions. 

The ionization of alkyl (E)-arylazo ethers is subject to general acid catalysis when the reaction is carried out in the presence of carboxylic acid buffers (see Scheme 6-3), and the ionization is also subject to steric acceleration in the presence of bulky substituents ortho to the azo ether group (Broxton and Stray, 1980 Broxton and McLeish, 1983 a, and earlier work of Broxton s group). 

The replacement of an electrofugic atom or group at a nucleophilic carbon atom by a diazonium ion is called an azo coupling reaction. By far the most important type of such reactions is that with aromatic coupling components, which was discovered by Griess in 1861 (see Sec. 1.1). It is a typical electrophilic aromatic substitution, called an arylazo-de-hydrogenation in the systematic IUPAC nomenclature (IUPAC 1989c, see Sec. 1.2). 

There are also some couplings in which hydrazones are formed but for which the azo tautomer is not detectable and probably does not exist. This is the case in some coupling reactions involving methyl groups of aromatic heterocycles (see, for example, 12.48 and 12.49 in Sec. 12.5). Replacement of a methyl proton by an arylazo group (Scheme 12-3) would result in an azo compound containing an sp3-hybridized — CH2 — group (12.1). The latter is less stable than the tautomeric hydrazone (12.2), in which there is a n-n orbital overlap from the heteroaromatic to the aromatic system. 

Azo coupling reactions with phenol ethers give in some cases the expected arylazo-phenol ether. In others, however, hydrolysis of the ether bond is observed and the arylazophenol is isolated. This ambiguity has, to the best of our knowledge, never been investigated systematically. 

The azo coupling reaction of the calix[4]arene 12.32 shows an unexpected auto-catalytic effect. If the molar ratio of the diazonium ion (X=N02) to the calix[4]arene is 4 1, the yield of the tetra(arylazo)calix[4]arene 12.33 is 99%, but with ratios 3 1, 2 1, and 1 1 the tetra(arylazo) compound is also a major product (70%, 45%, and 22% respectively). If ratios 3 1, 2 1, and 1 1 are used the yields of the tris- and bis(arylazo) products are in the range of only 1.2-3.4%, and the mono(arylazo) compound is formed with a yield of 5.3-6.0%. Using the ratio 4 1 the bis- and mono(arylazo) products are not found at all, and the tris(arylazo) com-... 

The coupling reaction of 3-methylindole (Scheme 12-21) is complex, as it involves an initial ipso-addition at the 3-position followed by rearrangement of the arylazo group to the 2-position (Jackson and Lynch, 1987 Jackson et al., 1987). However, under slightly different conditions Spande and Glenner (1973) isolated the unusual triazene 12.41. Based on the change in the UV spectrum of the reaction mixture with time, Sarma and Barooah (1977) proposed a mechanism involving initial formation... 

Some insertion reactions, particularly those of carbon monoxide, are reversible, but many are not. Reactions have also been reported which result in extrusion of Y from M—Y—X, even though the reverse of this process [Eq. (1)] is not known to occur. Elimination of Nj from arylazo... 

Refluxing a mixture of hydrazonoyl halides 13 and heterocyclic thiones 14 in ethanol in the presence of triethylamine resulted in the formation of 3-arylazo-l,4-dihydro-l,7-disubstituted-pyrimido[l,2,-3]-l,2,4,5-tetrazin-6-ones 8. The reaction starts with the initial formation of the hydrazidine derivatives 15, which in turn undergo cyclization with the elimination of thiolate to give the desired product 8 (Scheme 1)<2004JCM399>. 

Arylazo-4-(3-ethoxycarbonylureido)furoxans 62, which were synthesized by the reactions of 4-amino-3-arylazo-furoxans with ethoxycarbonyl isocyanate, were subjected to cascade rearrangements under the action of potassium r/-butoxidc in dimethylformamide or by heating in dimethyl sulfoxide to form 4-amino-2-aryl-5-nitro-2//-l,2,3-triazoles 63 (Scheme 13) <2001MC230, 2003RCB1829>. 

Diimines such as bpy and phen replace 2-(arylazo)pyridine ligands (aap) in [Pd(aap)Cl2] by a simple second-order process, whose detailed mechanism may depend on the nature of the incoming ligand (254). Three phthalocyanine units, each containing Zn2+, can be bonded to tetrahedral phosphorus, to give [PPh(pc-Zn)3]+. Mechanistic proposals are advanced for this novel exchange reaction in which palladium-bound phthalocyanine replaces phenyl on phosphorus (255). 

Since arylazoamidoximes release nitric oxide when incubated in rat liver microso-mial fraction [172], 3-arylazo-l,2,4-oxadiazol-5-ones 136 have been prepared from the corresponding arylazoamidoximes 134 as their potential pro-drugs [172]. Reaction with chloroformate afforded compounds 135 which underwent cyclisation to 136 in alkaline medium (Scheme 6.26). 

Reaction of melatonin with various aryldiazonium chlorides in ethanolic sodium acetate solution afforded arylazo-melatonin derivatives. Reactions of these products with either malonitrile or ethyl cyanoacetate formed the corresponding ary lam inotriazino[4,3-/z indole scaffolds 60-63 <2005BMC1847>. 

The influence of substituents on the rates of degradation of arylazo reactive dyes based on H acid, caused by the action of hydrogen peroxide in aqueous solution and on cellulose, has been investigated [43]. The results suggested that the oxidative mechanism involves attack of the dissociated form of the o-hydroxyazo grouping by the perhydroxyl radical ion [ OOH]. The mechanism of oxidation of sulphonated amino- and hydroxyarylazo dyes in sodium percarbonate solution at pH 10.6 and various temperatures has also been examined. The initial rate and apparent activation energy of these reactions were determined. The ketohydrazone form of such dyes is more susceptible to attack than the hydroxyazo tautomer [44]. 

Arylazo-l-naphthylamines were first reacted with ethyl orthoformate in boiling xylene for 2 hr diethyl malonate and piperidine were then slowly added to the reaction mixture over a period of 15-20 min. The resulting... 

Migrations of arylazo groups were first detected in the l,2,3,4,5-penta(methoxycarbonyl) cyclopentadiene 259 (equation 89)119-122. The randomization mechanism was considered as most probable because the reaction rate increases with increase in the solvent polarity (AGf9S = 56.9 to 69.1 kJmol-1). 

ReOCU reacts with PhNCO to give the rhenium(VI) compound [Re(NPh)Cl4] which forms adducts with donor solvents such as TFIF or acetonitrile. Anionic [Re(NPti)Cl5] is obtained when [Re(NPh)Cl4] is treated with [Mc4N]Cl. Two other approaches to rhenium(VI) arylimido compounds include an azo splitting reaction starting from 2-(arylazo)pyridines and the oxidation of rhenium(V) imides by nitric acid. ... 

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