I. M. Andreeva

Structure and ring-chain tautomerism of 3-(1-hydroxy-4-bromo-2-naphthyl)propenal

The previously undescribed 3-(1-hydroxy-4-bromo-2-naphthyl)propenal was synthesized. This aldehyde exists primarily in the form of the cyclic 2H-chromene tautomer in the crystalline state, in solutions in nonpolar solvents, and in acetonitrile, ethanol, and acetone. Ring-chain tautomeric equilibrium between the 2H-chromene and quinoid structures is observed in dimethyl sulfoxide.

Ring-chain tautomerism and thermo- and photochromism of 3-(1-hydroxy-4-methyl-2-naphthyl)propenal imines

A series of previously undescribed 3-(1-hydroxy-4-methyl-2-naphthyl)propenal imines was synthesized. In the crystalline state all of the imines, except the N-(p-nitrophenyl)imine, have an open o-quinoid structure, whereas in solutions in nonpolar solvents they exist in the cyclic 2H-chromene form. In polar solvents the imines display ring-chain tautomeric equilibrium of the 2H-chromene and o-quinoid forms, the relative percentages of which are determined by the character of the substituent in the amino component of the molecule and by the polarity of the solvent. The N-(p-nitrophenyl)imine has-the 2H-chromene structure in the solid phase and in solvents.

Structure and ring-chain tautomerism of 2-hydroxy-5-methyl-3,4-benzocinnamaldehyde

The previously undescribed 2-hydroxy-5-methyl-3,4-benzocinnamaldehyde was synthesized. A cyclic 2-hydroxy-2H-chromene structure in the crystalline state and in nonpolar solvents was established for it by IR, UV, and PMR spectroscopy. It is shown that transition to a polar solvent leads to the establishment of a tautomeric ring-chain equilibrium, the position of which is determined by the type of solvent.

Reactions of heterocyclic cations with nitrogen-containing nucleophiles. 10. Synthesis of 3,5,7-triaryl-1,2-oxazepinium perchlorates by the reaction of 2,4,6-triarylpyrylium salts with nitrones and substituted hydroxylamines

Abstract2-Substituted 3,5,7-triaryl-1,2-oxazepinium perchlorates were obtained by the reaction of 2,4,6-triarylpyrylium salts in dimethylformamide with nitrones and N-arylhydroxylamines. The products are the first representatives of seven-membered cations with eight π electrons.

Photo- and thermochromic 2-amino-2H-chromenes

A number of N-aryl- and N-alkylimines of 2-hydroxy-5,6-benzocinnamaldehyde were synthesized. The cyclic 2-amino-2H-chromene structure in nonpolar solvents was established for them by IR, UV, and PMR spectroscopy. It is shown that the transition to polar solvents leads to the establishment of a tautomeric ring-chain equilibrium. The equilibrium thermal transformations and phototransformations of some N-aryl- and N-alkylimines were studied.