The first example of reversible C-azo coupling in a series of aromatic and heteroaromatic compounds

Mokrushin, V. S.; Bezmaternikh, Maxim A.

doi:10.1070/mc1998v008n05abeh001024

Cited by 4 publications

(3 citation statements)

References 6 publications

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“…Evidence of complete reversibility of the electrophilic aromatic substitution reaction concerns only a few cases as in sulfonation reactions and in nitration reactions . An instance of the reversible C-azo coupling reaction is described when the reaction was carried out in the presence of p -toluenesulfonic acid …”

Section: Introductionmentioning

confidence: 99%

Evidence of Reversibility in Azo-Coupling Reactions between 1,3,5-Tris(N,N-dialkylamino)benzenes and Arenediazonium Salts

et al. 2007

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The reactions between strongly electron-rich aromatic substrates (1,3,5-tris(N,N-dialkylamino)benzenes, neutral carbon super nucleophiles) and diazonium salts produce moderately stable sigma complexes (Wheland complexes). The reactivity of Wheland complexes with electrophiles (other diazonium salts, or 4,7-dinitrobenzofuroxan) produces exchange reactions in the electrophilic part: the better electrophile replaces the less powerful electrophile. In the same way, in Wheland complexes with the 1,3,5-tris(morpholinyl)benzene, the 1,3,5-tris(piperidinyl)benzene replaces the less powerful nucleophile 1,3,5-tris(morpholinyl)benzene. Evidence is reported here indicating that for the title system the reaction of the attack of the electrophilic reagent producing Wheland complexes is a reversible process. The final products of the diazo-coupling reactions undergo a further attack of some diazonium salts. From the final products of the double diazo-coupling reactions (diazo compounds), we collected evidence that is a clear instance of complete reversibility of the diazo-coupling reaction.

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Section: Introductionmentioning

confidence: 99%

Evidence of Reversibility in Azo-Coupling Reactions between 1,3,5-Tris(N,N-dialkylamino)benzenes and Arenediazonium Salts

et al. 2007

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“…Evidence for the reversibility of the azo coupling at a carbon atom has been hitherto found in only a few examples; for the first time, probably by Zollinger6 upon the diazotization of 2‐amino‐1,3,4‐thiadiazole and the subsequent azo coupling with 3‐hydroxynaphthalene‐2,7‐disulfonic acid in 50 % H 2 SO 4 . Another example was described by Mokrushin a Bezmaternikh7 in the case of the reaction of 1‐(imidazol‐5‐yldiazenyl)naphthalene‐2‐ol and 1‐phenyldiazenylnaphthalene‐2‐ol, respectively, with N , N ‐dimethylaniline in the presence of p ‐toluenesulfonic acid. Štěrba8 confirmed the reversibility of the azo coupling by means of a kinetic study of the reaction of 2,6‐dioxo‐5(3)‐(4‐methoxyphenyldiazenyl)‐3(5)‐(4‐methoxyphenylhydrazono)‐1,2,3,6‐tetrahydropyridine‐4‐carboxylic acid with the 4‐nitrobenzenediazonium ion.…”

Section: Resultsmentioning

confidence: 99%

Diazonium Exchange and Migration of Pivaloyl Group upon Azo Coupling of β‐Enaminones

Šimůnek¹,

Bertolasi²,

Macháček³

2013

Eur J Org Chem

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4,4-Dimethyl-1-methylamino-1-phenyl-2-(substituted phen- yldiazenyl)pent-1-en-3-ones (prepared upon azo coupling of 4,4-dimethyl-1-methylamino-1-phenylpent-1-en-3-one 6a with the corresponding benzenediazonium tetrafluorobor- ates) react with another molecule of substituted benzenedi- azonium tetrafluoroborate (in dichloromethane in the pres- ence of anhydrous sodium acetate) to form substituted 4,4- bis(substituted phenyldiazenyl) derivatives 8. The second azo coupling is reversible. Derivatives 8 undergo either re- verse cleavage of a diazonium ion or [1,3] sigmatropic re- arrangement forming substituted formazane 9. In the case of the sequential use of two different diazonium tetrafluoro- borates, the less electrophilic group splits off more easily. The structures of the products 9 were studied by means of X-ray, 1H, 13C, 19Fand 15N NMR and MALDI HRMS analyses. The formazans 9 exhibit a reduced mobility of the phenyl group adjacent to the pivaloyl group, giving rise to anisochronism of proton and carbon atoms, to eventually form conformers. The reduced mobility was observed by means of NMR spec- troscopy. A temperature dependence of the spectral behav- iour was also studied

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“…5 Since derivatives 5a-f cannot be prepared by direct cyclization of the corresponding 4 substituted 5 (2 hydroxynaphthylazo)imidazoles 3a-f, we attempted to modify the ester group in 1 ethoxycarbonyl [1,2,4]triazines 5a-f, which cannot be obtained by direct cyclization of azo compounds 3a-f, on the basis of compound 5i (Scheme 3). This route includes two consecutive chemical reactions, namely, nitrosation of compound 5j at the carbohydrazide group to give azide 5l followed by nucleophilic displacement of the azide group upon the reaction with aromatic and aliphatic amines (see Scheme 3).…”

Section: Triazinesmentioning

confidence: 99%

Synthesis of 4-arylcarbamoyl-5-(2-hydroxynaphthylazo)imidazoles and 1-substituted naphtho[2,1-e]imidazo[5,1-c][1,2,4]triazines

Садчикова¹,

Mokrushin²

2006

Russ Chem Bull

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The reactions of β naphthol with 5 diazoimidazoles and imidazolyl 5 diazonium salts containing chemically different carboxamide groups in position 4 were studied. Hetero cyclization of 4 arylcarbamoyl 5 (2 hydroxynaphthylazo)imidazoles formed in these reac tions was investigated. The presence of the NH fragment in the amide group prevents this process, the reaction giving instead 3 substituted 3,7 dihydroimidazo[4,5 d] [1,2,3]triazin 4 ones, which is due to reversibility of C azo coupling. Methods for modification of 1 ethoxy carbonyl group in the naphtho[2,1 e]imidazo [5,1 c] [1,2,4]triazine system were developed and used to prepare substituted carboxamides inaccessible by other routes.It is known 1,2 that azo compounds based on diazo nium derivatives of pyrazole, triazole, tetrazole, and phenols or naphthols undergo intramolecular cyclization upon refluxing in methanol, glacial acetic acid, or 2 M sulfuric acid to give azolotriazines, whereas in the reac tion of 2 diazoimidazole with β naphthols, the cycliza tion product is formed already under azo coupling condi tions.The purpose of this work is to study the reactivity of 5 diazoimidazole 4 carboxamides 1a-h and imidazolyl 5 diazonium salts 2a-d containing chemically differ ent substituents in the carboxamide fragment toward β naphthol and to synthesize new naphtho[2,1 e]imid azo[5,1 c] [1,2,4]triazines based on the C azo coupling products obtained. 1a-h, 2a-d: R = NHC 6 H 4 Z, Z = p Me (a), p Cl (b), p OMe (c), p COOEt (d); R = NHC 6 H 11 (e), NHMe (f), (g),It should be emphasized that, when performing azo coupling with 5 diazoimidazoles 1a-f having an NH frag ment in the amide function, one should be aware of the possible formation of intramolecular cyclization prod ucts, namely, imidazo[4,5 d][1,2,3]triazin 4 ones. This type of cyclization is known 3 to take place almost instan taneously in highly acidic or alkaline media (рH <1, pH >7) or on heating and to be retarded at рH values from 1 to 6 and temperatures not exceeding room tem perature.Our study of the reactions of 5 diazoimidazole 4 (N substituted)carboxamides 1a-h with β naphthol has shown that the formation rate and the yields of products are markedly affected by the structure of the carboxamide substituent. By long term keeping of the reaction mixture at room temperature in dry acetonitrile, we were able to couple β naphthol only with diazoimidazoles 1e-h con taining aliphatic substituents in the amide part of the molecule (Scheme 1). This gave 5 (2 hydroxynaphthyl azo) 4 morpholinocarbonylimidazole (3g) and 5 (2 hydr oxynaphthylazo) 4 piperidinocarbonylimidazole (3h) in 54 and 48% yields, respectively (Table 1). Azo compounds 3e,f were formed together with imidazo[4,5 d] [1,2,3]tri azin 4 ones 4e,f in 33 and 42% yields, respectively. However, upon the reaction of 5 diazoimidazole 4 (N aryl)carboxamides 1a-d with naphthol under similar conditions, only traces of azo compounds were detected by chromatography. Only 3 substituted 3,7 dihydro imidazo[4,5 d] [1,2,3]triazin 4 ones 4a-d were isolated fro...

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The first example of reversible C-azo coupling in a series of aromatic and heteroaromatic compounds

Cited by 4 publications

References 6 publications

Evidence of Reversibility in Azo-Coupling Reactions between 1,3,5-Tris(N,N-dialkylamino)benzenes and Arenediazonium Salts

Evidence of Reversibility in Azo-Coupling Reactions between 1,3,5-Tris(N,N-dialkylamino)benzenes and Arenediazonium Salts

Diazonium Exchange and Migration of Pivaloyl Group upon Azo Coupling of β‐Enaminones

Synthesis of 4-arylcarbamoyl-5-(2-hydroxynaphthylazo)imidazoles and 1-substituted naphtho[2,1-e]imidazo[5,1-c][1,2,4]triazines

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