V. E. Zavodnik

Studies of 4H-3,1-benzoxazines: 13. Bromination of 1,2-dihydro-4H-3,1-benzoxazines

Bromination of 2,4-substituted 1,2-dihydro-4H-benzoxazines with bromine in acetic acid was conducted. It was shown that either the corresponding 6,8-dibromo-1,2-hydrobenzoxazines or the products of their dehydrogenation — 6,8-dibromobenzoxazines, are primarily formed as a function of the structure of the dihydrobenzoxazine and the concentration of bromine in the reaction mixture. The structure of 6,8-dibromo-2-(5-nitrofuryl-2)-4, 4-diphenyl-1,2-dihydro-4H-3,1-benzoxazine was investigated by XSA. A stacking interaction between the nitrofuran fragment of one molecule and the condensed benzene ring of the other was detected in the crystal.

2(5H)-furanone in the vilsmeier—haak reaction. Synthesis of β-substituted furans. Molecular structures of 3-dimethylaminomethylene-5-formyl-2(3H)-furanone and dimethylammonium 3,5-di(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidenemethyl)-2-furanolate

The reaction of 2(5H)-furanone with the Vilsmeier-Haak-Arnold reagent and subsequent addition of concentrated aqueous HClO4 to the reaction mixture give (3-dimethylaminomethylen-2-oxo-3H-5-furanyl)methylenimmonium perchlorate, whose hydrolysis under various conditions leads to 3-dimethylaminomethylene-5-formyl-2(3H)-furanone or to the potassium salt of 5-hydroxy-2,4-furandicarbaldehyde. The reaction of these products with CH-acids was studied. The structures of the key compounds of this work have been proved by the method of X-ray diffraction analysis.

Polyfuryl(aryl)alkanes and their derivatives

The reduction of 2-nitrophenyldifurylmethane with SnCl2 leads to an indolenyl ketone as a result of intramolecular heterocycloaddition of the intermediately formed nitroso derivative. During the reduction of 2-nitroaryldifurylmethanes in the Zn+HCl or NH2NH2·H2O+Pd/C systems, 2-aminoaryldifurylmethanes are formed; when treated with trityl perchlorate, their acetyl derivatives are converted into indolo[2,3-h]-1-oxazulenium perchlorates.

Polyfuryl(aryl)alkanes and their derivatives. 7. New recyclization and cyclization reactions in the 2-hydroxyaryldifurylmethane series

Reaction of 2-hydroxybenzaldehydes with α-methylfuran (sylvan) under acid-catalysis conditions was investigated. It is shown that the reaction does not stop at the step involving formation of 2-hydroxyarylfuryl-methanes but proceeds further with opening of one of furan rings and recyclization to 3-furylbenzo-furan derivatives. The latter in turn undergo transformations that lead to new heterocyclic systems — 5,6-dihydro-2,4-dimethyl-4-(5-methyl-2-furyl)-4H-benzo[b]furo[2,3-h]cyclopenta[b]furans. Data from the IR, PMR, and mass spectra, alternative synthesis, and x-ray diffraction analysis were used to confirm structures of the synthesized compounds.

Furylcyclohexenones. Conversion of 6-ethoxycarbonylcyclohexenones into 4,5-dihydroindazoles. Molecular and crystal structure of 4-phenyl-6-(5-methyl-2-furyl)-4,5-dihydroindazol-3-one

Abstract4,5-Dihydrodiazoles containing furyl substituents in positions 4 or 6 were obtained by condensation of hydrazine hydrate and 6-ethoxycarbonylcyclohexenones. XSA showed that in the crystalline state, the pyrazolone fragment of the dihydroindazole molecules has a betaine structure.

Thiuronium salts in the synthesis of thiazole derivatives. Synthesis of benzimidazolylthiazoles. Molecular and crystal structure of 2-acetylamino-5-(2-benzimidazolyl)-4-methylthiazole

Abstract5-(2-Benzimidazolyl)thiazoles were obtained by the reaction of benzimidazolylmethylthiuronium salts with carboxylic acid anhydrides. The three-dimensional structure of 2-acetylamino-5-(2-benzimidazolyl)-4-methylthiazole monohydrate was investigated by x-ray diffraction analysis (XDA).

Studies on quinazoline chemistry. 4. Unexpected route of acylation of alkyl 2-(4,4-diphenyl-1,2,3,4-tetrahydro-2-quinazolinylidene)acetates. molecular structure of methyl 2-(4,4-diphenyl)-1,2,3,4-tetrahydro-2 -quinazolinylidene )-3-oxobutanoate

A study of the reaction of quinazoline derivatives with acid chlorides in the absence of acids has shown that alkyl 2-(4,4-diphenyl-1,2,3,4-tetrahydro-2-quinazolinylidene)acetates undergo C-acylation. The molecular structure of methyl 2-(4,4-diphenyl-1,2,3,4-tetrahydro-2-quinazolinylidene)-3-oxobutanoate has been investigated by X-ray analysis.

Synthesis and properties of (thieno[2,3-b]pyridin-3-yl)iminotriphenylphosphoranes. Molecular structure of (2-benzoyl-4-methoxymethyl-6-methylthieno[2,3-b]pyridin-3-yl)iminotriphenylphosphorane

Iminophosphoranes containing a thieno[2,3-b]pyridine fragment were obtained through a sequence of reactions: 1) alkylation of 3-cyano-2(1H)-pyridinethiones in alkaline medium by an α-halocarbonyl compound with subsequent Thorpe-Ziegler cyclization of the resultant 2-thioalkylpyridines to give 3-aminothieno[2,3-b]pyridines, 2) diazotization of the amino group and nucleophilic substitution of the diazonium group by an azido group without isolation of the diazonium salts, and 3) reaction of the 3-azidothieno[2,3-b]pyridines with triphenylphosphine.

Synthesis of Conjugated Systems Based on 3-(5-Methylfur-2-yl)-2-(3-oxobutyl)benzofurans

Methods were developed for the synthesis of 3-butyl-2-(3-oxobutenyl)benzofurans and 3-(3-furylbenzofuran-2-yl)acrylic acids on the basis of 3-furyl-2-(3-oxobutyl)benzofurans.

Sterically strained conjugated systems containing a trisubstituted furan ring. Molecular structure of 5-dimethylamino-2,4-bis[2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)methyl]furan

We have synthesized sterically strained conjugated systems containing a trisubstituted furan ring. We have used X-ray diffraction to study the three-dimensional structure of 5-dimethylamino-2,4-bis[(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-ylidene)methyl]furan. We have shown that such sterically strained systems undergo nonclassical deformations with distortion of mainly bond angles, but without loss of planarity.