N. V. Shibaeva

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.

Ambidentate reactivity of 3-azapyrylium systems in nucleophilic attack reactions

It has been shown that recyclization of 4-acylmethyl-3-azapyrylium salts under the influence of primary amines affords 4-(β-hydrozystyryl)pyrimidinium salts, which, upon further heating with the amine, are recyclized to form 4-acylaminopyridinium salts. It has been established that nucleophilic attack of 6-acylmethyl-substituted 3-azapyrylium salts in aqueous NaOH solution leads to functionally substituted pyridines. By means of MNDO quantum-chemical calculations with an accounting for solvation effects, in a continuum model, it has been shown that two directions of nucleophilic attack of the azapyrylium ring — at positions 2 and 6 — are equally probable.

Synthesis of the alkaloid dioxyline and other 6,7-dimethoxyisoquinolines in a modified ritter reaction

It has been found that aceto- and benzonitriles and 3,4-dimethoxyphenylacetone in the presence of acetylperchlorate or upon heating in polyphosphoric acid or polyphosphoric ester form the corresponding isoquinoline. The data indicate that the reaction proceeds like a typical Ritter reaction and is defined by electrophilic activation of the carbonyl group of the ketone and the nucleophilicity of the nitrile. This methodology gave the alkaloid dioxyline (dimoxyline), obtained in high yield by the use of benzoylhexachloroantimonate.

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.

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

Abstract4-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.

Formation of γ-Pyrones by Acylation of Benzoylacetone.

The reaction between benzoylacetone (I) and the acyl hexachloroantimonates, generated in situ from the acyl chlorides (II) and SbCl5, yields the title compounds (III) after treatment with alkali.