Properties of the amino group in N-(aminophenyl)pyridinium perchlorates

The pyridinium ring as a substituent in aniline is an electron acceptor, the effect of which is comparable to the effect of NO₂ and N(CH₃)₂ groups. Correlation of the reactivities with the basicities of the amino groups is not observed in the investigated reactions of N-(aminophenyl)pyridinium perchlorates with some electrophilic reagents, inasmuch as steric factors apparently play a greater role.     

Optical and photochemical properties of N-benzalaminophenylpyridinium perchlorates

The electronic spectra of a number of benzylidene derivatives of N-aminoarylpyridinium perchlorates are associated with absorption localized on the individual pyridinium and azomethine fragments and with intramolecular charge transfer (ICT) from the azomethine fragment to the pyridinium ring. The luminescence is associated with the latter process. The photochromism is due to proton transfer in the excited state of the azomethine fragment, which competes with ICT, and is also due to structural factors.     

Reactions of 4-(o-carboranyl)pyrylium salts with nucleophilic agents. Synthesis of nitrogen heterocycles with an o-carboranyl substituent

Nitrogen heterocycles, viz., pyridines, pyridinium salts, diazepine, and pyrazoles, with an o-carboranyl substituent were obtained by reaction of 4-(o-carboranyl)-pyrylium perchlorates with nitrogen-containig nucleophilic agents, viz., ammonia, primary amines, hydrazine, and phenylhydrazine. Opening of the pyrylium ring without involvement of the carborane ring occurs under the influence of bases.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 454–458, April, 1981.     

2-Benzopyrylium salts

The acylation of esters of 3,4-dimethoxyphenylpyruvic acid with anhydrides of aliphatic acids in the presence of 70% HClO₄ leads to the formation of 3-alkoxycarbonyl-1-alkyl-6,7-dimethoxy-2-benzopyrylium salts which, on being boiled with sodium acetate inglacial acetic acid, are converted into 3-alkoxycarbonyl-1-alkyl-6,7-dimethoxyisoquinolines.For Communication XIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1458–1460, November, 1973.     

2-Benzopyrylium salts

The properties of 1,3-dimethyl-6,7-dialkoxy-2-benzopyrylium salts were studied. The heterocyclic oxygen atom is readily replaced by nitrogen by reaction of the 2-benzopyrylium salts with primary amines, hydrazine, phenylhydrazine, glycine ethyl ester, and hydroxylamine; reaction with secondary amines leads to naphthalene derivatives. The activities of the methyl groups in the 1 and 3 positions of the heterocyclic ring are compared.For Communication IX, see [6].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1308–1312, October, 1970.     

Reactions of heterocyclic cations with nitrogen-containing nucleophiles. 10. Synthesis of 3,5,7-triaryl-1,2-oxazepinium perchlorates by the reaction of 2,4,6-triarylpyrylium salts with nitrones and substituted hydroxylamines

2-Substituted 3,5,7-triaryl-1,2-oxazepinium perchlorates were obtained by the reaction of 2,4,6-triarylpyrylium salts in dimethylformamide with nitrones and N-arylhydroxylamines. The products are the first representatives of seven-membered cations with eight electrons.See [1] for Communication 9.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 457–460, April, 1982.     

Anomalous reaction of 1-ethyl(benzyl)-3-methyl-2-benzopyrylium salts with dimethylamine

Chemistry of Heterocyclic Compounds -     

Electrochemical modeling of the oxidative dehydrogenation of 1-phenyl-1H-3-methyl-6,7-dimethoxyisochromene

The electrochemical oxidation of 1-phenyl-1H-3-methyl-6,7-dimethoxyisochromene on a rotating platinum disk electrode with a ring in acetonitrile was investigated. Three one-electron waves are observed on the polarization curves of the disk electrode, and three cathode waves corresponding to reduction of the intermediates are recorded on the ring. The current decreases after the second wave, and this constitutes evidence for the occurrence of a subsequent chemical reaction. It was established that decomposition of the isochromene cation radical leads to the 3-methyl-6,7-dimethoxy-2-benzo-pyrylium ion, while decomposition of the dication leads to the 1-phenyl-3-methyl-6,7-dimethoxy-2-benzopyrylium ion, which is formed via an EEP scheme.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1177–1181, September, 1981.     

Reaction of α and γ-methylpyrylium salts with orthoesters

The reaction of orthoesters with α- and γ-methylpyrylium salts gives 2- and 4-alkoxyvinyl-pyrylium salts the acid hydrolysis of which leads to 2- and 4-hydroxyvinylpyrylium salts and the alkaline hydrolysis to pyranylideneacetaldehydes.