Acid-catalyzed acylation of 4-alkyl-3-azapyrylium salts and the synthesis of 4-acylaminopyrylium salts

4-Alkyl-3-azapyrylium salts undergo acylation at the alkyl group under acid-catalyzed conditions to give 4-acylmethyl-3-azapyrylium derivatives, which upon heating in proton-donating solvents recyclize to give 4-acylaminopyrylium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 265–269, February, 1991.     

On the structure of “tetraphenyldipyranyl ether”

The reaction product of 2,6-diphenylpyrylium perchlorate with water in presence of bases, which earlier was assigned the structure of α,α',α″,α″-tetraphenyl-γ,γ'-dipyranyl ether, is identified now as 2,6-dipyranylidene-1, 5-diphenylpentenedione-1,5 from its chemical and spectral properties and by X-ray analysis.Crystals are monoclinic, space group P2₁/n with Z =4 in a unit cell of dimensions a =24.088, b= 9.323, c = 11.289 Å, β = 95.30°. The structure was solved by direct method and refined isotropically to R = 0.126 for 2423 reflections.     

Photomonocyclization of 1,2,6-triarylpyridinium cations

Conclusions It was found by UV spectroscopy and x-ray diffraction analysis that the photocyclization of 1-(3'-halophenyl)-2,4,6-triphenylpyridiniurn cations leads to stable 1,3-diphenyl-11-chloro(bromo)-azoniatriphenylene cations.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 535–540, March, 1982.     

Reactions of heterocyclic cations with nitrogen-containing nucleophiles. 11. Reaction of 2,6-diphenylpyrylium perchlorate with primary amines,hydrazine, and hydroxylamine

The reaction of 2,6-diphenylpyrylium perchlorate with methylamine and various anilines in acetic acid leads to pyridinium salts; 3,4-bispyridinium perchlorates were obtained in dimethylformamide. The reaction of 2,6-diphenylpyrylium perchlorate with hydrazine and the sodium salt of hydroxylamine leads to 3-phenyl-5-phenacyl-2-pyrazoline and -2-isoxazoline.See [1] for Communication 10.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 461–464, April, 1982.     

Condensation of 6-methyl-3-azapyrylium salts to pyrido[1,2-c]pyrimidinium derivatives

Under the influence of DMF/Ac₂O 2,4-diphenyl-6-methyl-3-azapyrylium perchlorates undergo condensation to give pyrido[1,2-c]pyrimidinium perchlorates. The structure of one of the perchlorates was proved by x-ray diffraction analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1556–1561, November, 1991.     

Synthesis of pyrylium salts by condensation of Β-chlorocinnamaldehydes with carbonyl compounds

A method is proposed for the synthesis of unsymmetrical unsubstituted pyrylium salts by condensation of -chlorocinnamaldehydes with methyl and methylene ketones and -dicarbonyl compounds in the presence of HClO₄ or Lewis acids. The probable scheme of the reaction is examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1031–1035, August, 1974.     

Synthesis of substituted γ-pyrones

Substituted -pyrones were synthesized by the acylation of phenylacetaldehyde and its enol acetate with acetic and propionic anhydrides in the presence of 70% HClO₄. The mechanism of the reaction is examined, and the IR and PMR spectra of the synthesized -pyrones are presented. Some of their transformations were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 152–154, February, 1972.     

Electrochemical interconversion of 1-(p-tolyl)-6-methyl-2,4-diphenylpyrimidinium perchlorate and 1-(p-tolyl)-6-methylene-2,4-diphenylpyrimidine

It is shown that reduction of the 6-methyl-1-(p-tolyl)-2,4-diphenylpyrimidinium cation proceeds in two one-electron stages. In the first stage, an unstable radical is formed, and in the second stage, an unstable anion. As a result of dehydrogenation of the radical, the anhydro base 6-methylene-1-p-tolyl-2,4-diphenyl-6H-pyrimidine is formed. Oxidation of this compound in a single one-electron stage forms an unstable cation radical, the hydrogenation of which leads to the original pyrimidinium cation. Data obtained by cyclic voltametry and electrosynthesis with subsequent identification of the products have shown that, the same as in the reaction with the hydroxide anion, the methyl-substituted pyrimidinium cation acts as a CH-acid.Rostov State University, Rostov-on-Don 344101, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 71–75, January, 1999.