V. V. Tkachenko

Synthesis of 4-alkoxybenzopyrylium salts and chromones

The reaction of substituted o-hydroxyacetophenones with ethyl orthoformate in the presence of 70% perchloric acid gave 4-alkoxybenzopyrylium salts, which were converted to the corresponding chromones in almost quantitative yield on refluxing with water.

Synthesis of khellin derivatives

The reaction of orthoformic ester with o-hydroxychalcones in the presence of perchloric acid has yielded 4-ethoxy-5,9-dimethoxy-6,7-fluroflavylium salts which have been converted by treatment with aqueous ethanol into 5,9-dimethoxy-6,7-furoflavones.

Reactions of 4-ethoxyflavylium, 4-ethoxychromylium, and 4-ethoxyfurochromylium salts with several amines

The reactions of 4-ethoxyflavylium, 4-ethoxychromylium, and 4-ethoxyfurochromylium salts in acidic media with several acids were investigated. In the reaction with hydrazine the furochromylium salt forms pyrazole, whereas both α,β-substituted benzopyrylium salts are converted to azines. The reaction of hydroxylamine with the flavylium salt gives a flavone oxime, whereas the reaction with the furochromylium salt gives an isoxazolylbenzofuranol.

Synthesis of o- and p-hydroxyacetophenones and 2-methyl-4,6-diarylpyrylium and 2-aryl-4-methyl-benzopyrylium salts by acetylation of some phenols

Acylatton of phenols with acetic anhydride in the presence of 70% perchloric acid results in the synthesis of hydroxyaryl methyl ketones and substituted benzopyrylium salts.