Alexander V. Safrygin

Novel method for the synthesis of 3-[(3-arylpyrazol-5-yl)methylidene]-quinoxalin-2-ones on the basis of 2-methylchromones

3-(Chromon-2-ylmethylidene)quinoxalin-2-ones reacts with hydrazine hydrate in boiling n-BuOH at the chromone moiety to form 3-(3-arylpyrazol-5-ylmethylidene)quinoxalin-2-ones in 47–86% yields.

Synthesis of 4-arylamino-3-(trifluoromethyl)pyridazines and pyridazino[3,4-b]quinoxalines (as by-products) from 3-aroylmethyl-2-(trifluoromethyl)quinoxalines and hydrazine hydrate

A number of 4-arylamino-3-(trifluoromethyl)pyridazines were obtained in good yields via the novel reaction of 3-aroylmethyl-2-(trifluoromethyl)quinoxalines with an excess of hydrazine hydrate in refluxing n-butanol with or without acetic acid. This reaction is accompanied by the formation of side-products with the pyridazino[3,4-b]quinoxaline skeleton. The possible reaction mechanism was discussed.

Synthesis of 6-(2-hydroxyaryl)-2-pyridones by the reaction of chromones with cyanoacetic, acetoacetic, and malonic acid amides

A reaction of chromones with cyanoacetic, acetoacetic, and malonic acid amides in the presence of sodium ethoxide furnished a number of new 3-substituted 6-(2-hydroxyaryl)-2-pyridones in good yields, including those containing a polyfluoroalkyl group at position 4.

Synthesis and chemical properties of 2-acylchromones

Methods of synthesis and reactivity of 2-formyl-, 2-alkanoyl-, 2-aroyl- and 2-trifluoroacetylchromones are summarized and systematized. It is shown that these chromone derivatives react mainly with N-, C- and P-nucleophiles, as well as undergo reduction and oxidation. The conditions of these reactions and the yields of the products are reported. Special attention is focused on biologically active derivatives.The bibliography includes 84 references.

Reactions of 2-(trifluoroacetyl)chromones with aromatic amines

Aromatic amines reacted with 2-(trifluoroacetyl)chromones as С- or N-nucleophiles, depending on the conditions. When the reaction was performed under solvent-free conditions at 100°С for 12–18 h, they acted as С-nucleophiles and gave bishetarylcarbinols in 21–67% yields, while in refluxing toluene the addition of primary arylamines occurred via the amino group, providing the corresponding hemiaminals (80–86%).

One-pot synthesis of functionalized benzo[c]coumarins and their precursors via the reaction of 2-(polyfluoroalkyl)chromones with 4-alkyl-3-cyanocoumarins

2-(Polyfluoroalkyl)chromones react with 4-alkyl-3-cyanocoumarins in dichloromethane in the presence of triethylamine to give a wide variety of functionalized benzo[c]coumarin derivatives in good yields. This new annulation reaction presumably proceeds by a tandem intermolecular Michael addition and subsequent intramolecular condensation between an intermediate enolate anion and cyano group. In the case of 3-cyano-4-methylcoumarin and 2-(trifluoromethyl)chromones activated by two electron-withdrawing substituents, three acyclic intermediates were isolated and the possible mechanism of the reaction was suggested.

Synthesis and reactivity of 8-aza-5,7-dimethyl-2-trifluoroacetylchromone

Claisen condensation of 3-acetyl-4,6-dimethyl-2-pyridone with methyl 2-methoxytetrafluoropropionate in the presence of LiH in refluxing dioxane gave the corresponding 1,3-diketone, further converted by treatment with conc. H2SO4 to 5,7-dimethyl-2-(1-methoxytetrafluoroethyl)-8-azachromone and 5,7-dimethyl-2-trifluoroacetyl-8-azachromone, which was isolated as hydrate. The first of these azachromones reacted with dinucleophiles at the С-2 atom and the pyrone carbonyl group, while the second reacted at the С-2 atom and trifluoroacetyl group. Based on these compounds, we obtained new trifluoromethylated heterocyclic systems containing a 2-pyridone ring, as well as (8-azachromon-2-yl)(indol-3-yl)carbinols.

Reaction of 2-trifluoromethylchromones with cyanoacetic and malonic esters. Synthesis of new benzo[ c ]coumarin derivatives

Reflux of 2-trifluoromethylchromones with ethyl cyanoacetate and diethyl malonate in ethanol in the presence of sodium ethoxide furnished a number of new benzo[c]coumarin derivatives, which were formed with involvement of two ester molecules.