Reaction of pyrylium salts with amidines

2,4,6-Substituted pyrimidines were obtained by reaction of 2,4,6-triarylpyrylium perchlorates with amines. 2,4-Substituted pyrimidines were similarly synthesized from 2,6-diphenylpyrylium perchlorate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 456–458, April, 1978.     

Hydroamination of pyrylium salts

Some pyrylium salts and condensed systems derived therefrom have been hydromethyl-aminated to saturated azaheterocycles and N-methylpyridinium salts. Attempts to hydroarylaminate pyrilium salts resulted in the formation of the corresponding hydrocarbons.Translated from Khimiya Geterotsoklicheskikh Soedinenii, No. 12, pp. 1652–1655, December, 1984.     

Hydroamination of pyrylium salts

The catalytic reductive amination of pyrylium salts proceeded stereoselectively to give piperidine bases with a cis-structure. The reaction involved the formation of a pyridine intermediate; the course of the reaction depended on the structure of both the substrate and the aminating agent.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, 608–611, May, 1990.     

Reactions of pyrylium salts with nucleophilic agents

The reaction of -unsubstituted pyrylium salts with alkali-metal cyanides gives cyano- and carboxy-substituted pyrans and pyrylium salts, while the reaction with sodium sulfide gives dipyranyl sulfides. A phthalimide derivative of pyran is obtained from 2,6-diphenylpyrylium perchlorate and potassium phthalimide, while pyrylium cations react with zinc to give the corresponding dipyranyls.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1313–1316, October, 1972.     

Reaction of some pyrylium salts with hydrazine

2,6-Diphenyl- and 2,6-di-tert-butylpyrylium salts react with excess hydrazine to give 1,2-diazeplne derivatives. Under the same conditions, 4-(1-methyl-3-indolyl)flavylium perchlorate forms 3-phenyl-5-(1-methyl-3-lndolyl)pyrazole.Translated from Khimiya Geterotsiklichesikikh Soedinenii, No. 1, pp. 45–48, January, 1973.     

Reaction of pyrylium salts with heterocyclic amines

It has been established that in the reaction of 2, 4, 6-trimethylpyrylium perchlorate with 2-, 3-, and 4-aminopyridines, cytosine, adenine, guanine, and the corresponding nucleosides, and also with 2-amino-1-methylbenzimidazole, 2-amino-4-methylthiazole, 2-amino-4-phenylthiazole, 2-amino-6-bromobenzo-thiazole, and 2-amino-6-methoxybenzothiazole, either the corresponding quaternary pyridinium salt is formed or the pyrylium ring opens, depending on the basicity of the amino group.     

Thiapyrylium and pyrylium salts with furyl substituents

The possibility of obtaining pyrylium and thipyrylium salts that contain acidophobic furyl substituents by the action of protic acids on the corresponding 1,5-diketones in acetic acid or methanol, depending on the position of the furan rings relative to the carbonyl groups, was established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1604–1607, December, 1981.     

Recyclization of indolo[2,3-c]pyrylium salts by reaction with secondary amines

1-R-3-methylindolo[2,3-c]pyrylium salts react with cyclic secondary amines (morpholine, piperidine, and N-methylpiperazine) to give, depending on the structure of the alkyl substituent R, either 1- (when R=Me) or 3-aminocarbazoles (when R=i-Pr), or mixtures of both (when R=Et). The position of the amino-substituent in 1-morpholino-3,9-dimethylcarbazole has been established by x-ray diffraction examination.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 546–551, April, 1990.     

The spectroscopy of pyrylium salts

The spectra of pyrylium perchlorate, various alkyl and aromatic derivatives, and cyanine-like dyes derived from pyrylium salts are discussed. These molecules are closely related to molecules which belong to the C_2v point group, and the existence of the symmetry permits a more detailed discussion of the spectra than has been attempted heretofore.     

Reaction of 2-functionalized pyrylium salts with amidrazones

A number of derivatives of the bicyclic 1,2,4-triazolo [1,5-a] pyridine ($\text{3}$) and pyrido [2,1-f][1,2,4] triazine ($\text{4}$ and $\text{7}$) have been prepared by reaction of 2-methylthio- and 2-ethoricarbonyl-4, 6-diphenylpyrylium salts, respectively, with amidrazones.     

Catalytic hydrogenation of pyrylium salts

On catalytic reduction of 2,6-diphenylpyrylium salts, hydrogenolysis occurs at the C–O bond with the formation of 1,5-diphenylpentanes. The principal direction of the hydrogenation of 9-phenyl-sym-octahydroxanthylium tetrafluoroborate is the formation of a mixture of products of partial and complete reduction of the heterocycle. The structure of the substances obtained was established by IR and¹³C NMR spectroscopy.N. G. Chernyshevskii Saratov State University, Saratov 410026, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 614–617, May, 1998.     

Reaction of methyl-substituted pyrylium salts with tertiary amines

2,4,6-Trimethylpyrylium perchlorate reacts with heterocyclic compounds containing apyridine nitrogen atom and having basicities higher than 9 pK_a units (in acetonitrile) through a step involving the formation of a methylenepyran. 4-Methyl-2,6-diphenyl- and 2-methyl-4,6-diphenylpyrylium perchlorates react with benzimidazole to give 1,2-ethanediylidenebispyrans. Methyl-substituted pyrylium salts react with 2,6-diphenylpyrylium and flavylium perchlorates in the presence of benzimidazole to give methylidynecyanines and with acetic anhydride to give trimethylidynecyanines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1484–1489, November, 1976.     

Synthesis of pyrimidine derivatives by reaction of pyrylium salts with guanidine and compounds of the guanidine series

2,4,6-Triphenylpyrylium perchlorate reacts with methylguanidine to give 1-methyl-2-amino-4,6-diphenylpyrimidinium perchlorate, which undergoes the Dimroth rearrangement to give 2-methylamino-4,6-diphenylpyrimidine. 2,4,6-Triarylpyrylium perchlorates react with guanidine to give N-pyrimidinylpyridinium salts. Pyrylium salts react with aminoguanidine, sulfanilylguanidine, and symmetrical diphenylguanidine at one amino group to give the corresponding pyridinium salts. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 748–752, June, 1980.     

Reaction of pyrylium salts with amines of the benzimidazole series

The reaction of pyrylium salts with primary amines of the benzimidazole series gives benzimidazolylpyridiniumperchlorates. The bacteriostatic action of the synthesized preparations was investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1685, December, 1973.