V. Ph. Anufriev

Synthesis and structure elucidation of oxidative coupling products of 2-hydroxy-1,4-naphthoquinones

Abstract2,3-Dihydro-3-O-(1,4-naphthoquinon-2-yl)-2-oxo-1,4-naphthoquinones are the products of oxidative coupling of substituted 2-hydroxy-1,4-naphthoquinones (regardless of the presence of peri-hydroxy groups in their structures) under the action of lead dioxide.

Chemistry of naphthazarin derivatives. 8. Determination of structures of substituted 2-hydroxy-6(7)-methoxynaphthazarins and 7(8)-hydroxypyranonaphthazarins by IR spectroscopy

A set of substituted 2-hydroxy-6(7)-methoxynaphthazarins and 7(8)-hydroxypyranonaphthazarins were synthesized. The IR spectra of 2-hydroxy-6-methoxynaphthazarins and 7-hydroxypyranonaphthazarins, on the one hand, and of 2-hydroxy-7-methoxynaphthazarins and 8-hydroxypyranonaphthazarins, on the other hand, have the characteristic nonoverlapping intervals of stretching vibration frequencies of the β-hydroxy groups. These regularities confirm the structures of cristazarin and 6-methylcristazarin, which are metabolites of lichen Cladonia cristatella.

Cytotoxic activity of intermediates and side products of echinochrome synthesis

The cytotoxic activity of the principal intermediates and side products of echinochrome synthesis toward gametes of the sea urchin Strogylocentrotus intermedius was studied. Di-and trichloro naphthazarin derivatives with two vicinal Cl atoms were the most active.

Chemistry of naphthazarin derivatives. 11. Trisubstituted hydroquinone derivatives in the preparative synthesis of naphthazarins

The Friedel—Crafts acylation of trimethylhydroquinone, 3,5-diethyl-2-hydroxyhydroquinone, and 3,5-diethyl-1,2,4-trimethoxybenzene with dichloromaleic or citraconic anhydride in an AlCl3—NaCl melt is accompanied by o-C-dealkylation to afford functionally substituted naphthazarins.

Chemistry of naphthazarin derivatives. 9. Direct observation of prototropic tautomerism of (poly)hydroxynaphthazarins by IR spectroscopy

A series of substituted (poly)hydroxylated naphthazarins (5,8-dihydroxy-1,4-naphthoquinones) were synthesized. In general, (poly)hydroxynaphthazarins exist in organic aprotic solvents as mixtures of tautomeric 1,4-naphthoquinonoid forms (IR data). The ratio of tautomers was determined for the first time. The effects of the nature of substituents and the solvent polarity on the tautomeric equilibrium were qualitatively estimated.

Cycloacylation of chloro-substituted hydroquinone dimethyl ethers with dichloromaleic anhydride

Under the drastic conditions of Zahn—Ochwat cycloacylation of 2-chloroand 2,3-dichlorohydroquinones with dichloromaleic anhydride (a melt of anhydrous AlCl3 and NaCl, 185—195 °C), the substrates undergo various degrees of disproportionation, which reduces the yields of the target triand tetrachloronaphthazarins. Quantum chemical calculations showed that the cycloacylation in question proceeds as a double aromatic electrophilic substitution of the vicinal protons with the corresponding oxocarbenium ions (acylium cations).

Chemistry of naphthazarin derivatives. 12. Synthesis and investigation of prototropic tautomerism of 3-(alk-1-enyl)-2-hydroxynaphthazarins

Substituted 3-(alk-1-enyl)-2-hydroxynaphthazarins were synthesized. According to data from IR spectroscopy, these compounds exist in organic aprotic solvents as mixtures of tautomeric 1,4-naphthoquinonoid forms. The compositions of tautomeric mixtures were quantitatively determined. The effects of the structure of the alkenyl substituent and the polarity of the solvent on the tautomeric equilibrium were qualitatively estimated.

THE CHEMISTRY OF NAPHTHAZARINE DERIVATIVES. 5. THE STRUCTURE OF DEHYDROECHINOCHROME MONOHYDRATE

Based on IR and1H and13C NMR spectroscopic studies, the oxidation product of echinochrome with Ag2O was assigned the structure of 2,3-epoxy-7-ethyl-2,3-dihydro-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone.Based on IR and1H and13C NMR spectroscopic studies, the oxidation product of echinochrome with Ag2O was assigned the structure of 2,3-epoxy-7-ethyl-2,3-dihydro-2,3,5,6,8-pentahydroxy-1,4-naphthoquinone.

Synthesis and study on oxidative coupling products of 3-alkyl-2-hydroxynaphthazarins

The resulting products of oxidative coupling of substituted 3-alkyl-2-hydroxynaphthazarins in the presence of lead dioxide are the compounds with 7,14-dibenzo[a,i]oxanthrene skeleton.