O. V. Fedotova

Oxygen-containing Heterocyclic Compounds from 1,5-Diketones. (Review)

Literature and characteristic experimental data correlated in the review concern the intramolecular cyclization by various means of substituted 1,5-diketones of the acyclic, semi-, and bicyclic series, proceeding to the formation of oxygen-containing heterocycles, such as pyrans, pyrylium salts, di- and tetrahydrofurans, and their condensed analogs, aroylfurans etc.

Modified Biginelli reaction in the synthesis of chromenopyrimidobenzimidazolones

Biginelli reaction of 4-hydroxychromen-2-one with aromatic aldehydes and biazanucleophiles was investigated. The character of the substituent in the aromatic aldehyde and the reaction conditions affect its direction. The possibility to separate two probable regio isomers and the preparation of the chromenopyrimidobenzimidazolone with angular junction was demonstrated. The use of nuclear Overhauser effect (NOE 1D) made it possible to establish the spatial interaction between ortho-protons of chromene and benzimidazole fragments additionally confirming the structure of the obtained compound. The identification of the possible intermediates in the case of reacting 3-methyl-1H-pyrazol-5-amine as the azabinucleophile confirms the assumed scheme of 2H-chromen-2-ones formation under the applied conditions.

Antioxidant properties of 2,4-diphenyl-7,8-benzo-5,6-dihydro(4H)selenochromene and 2-para-chlorophenyl-4-phenyl-7,8-benzo-5,6-dihydro(4H)selenochromene

The antioxidant properties of 2,4-diphenyl-7,8-benzo-5,6-dihydro(4H)selenochromene and 2-para-chlorophenyl-4-phenyl-7,8-benzo-5,6-dihydro(4H)selenochromene were studied using the initiated oxidation of ethylbenzene and propan-2-ol as model reactions. The antioxidant activity of these compounds was quantitatively characterized by the apparent rate constant of inhibition, fkin. Addition of 2,4-diphenyl-7,8-benzo-5,6-dihydro(4H)selenochromene to ethylbenzene being oxidized increases the chemiluminescence intensity.

Chemistry of 1,5-diketones: I. Halogenation of aryl-substituted pent-2-ene-1,5-diones, pentane-1,5-diones, and their fused analogs

Halogenation of 3-(4-methoxyphenyl)-1,5-diphenylpent-2-ene-1,5-dione, 3-(4-methoxyphenyl)-1,5-diphenylpentane-1,5-dione, and 2-[1-(4-methoxyphenyl)-3-oxo-3-phenylpropyl)-1,2,3,4-tetrahydroaphthalen-one with bromine, chlorine, and dichloro(phenyl)-λ3-iodane leads to formation of the corresponding monobromo-, dichloro-, or trichloro-substituted 1,5-diketones, depending on the conditions. Halogenation of the aliphatic chain and methoxyphenyl substituent can be accompanied by heterocyclization to give pyrylium salts.

Carbonyl-containing spiro-dihydrofurans in reactions with ammonium acetate and hydrazine hydrate

It has been shown that 2-spiro(3-R-6,6-dimethyl-4-oxo-2,3,4,5,6,7-hexahydrobenzofuran)-2′-(5′, 5′-dimethylcyclohexane-1′,3′-diones) undergo conversions in reactions with ammonium acetate and hydrazine hydrate into substituted dihydropyridin-2-ones and tetrahydro-1,2-diazepin-7-ones respectively as a result of ring-opening of the spirodimedonyl fragment through the corresponding amides and hydrazides of δ-keto acids.

Structure and stabilization factors of the 2-aminobenzimidazolium–3,3′-(phenylmethylene)- bis(4-hydroxy-2H-chromen-2-one) anion associate in the system 4-hydroxy-2H-chromen-2-one–benzimidazol-2-amine–benzaldehyde

The molecular and crystal structures of the ionic associate formed by 2-aminobenzimidazolium cation solvated by one dimethyl sulfoxide molecule and 3,3′-(phenylmethylene)bis(4-hydroxy-2H-chromen-2- one) anion were determined by X-ray analysis. This associate was isolated in the acid-catalyzed three-component reaction of 4-hydroxy-2H-chromen-2-one with benzimidazol-2-amine and benzaldehyde together with regioisomeric dihydrochromenopyrimidobenzimidazolones resulting from the classical Biginelli condensation. The steric and electronic structures of the cation and anion were calculated at the B3LYP/6-311++G(d,p) level of theory in combination with NBO analysis. Factors stabilizing the ion pair and crystal field effects on the stability of the associate and its constituents were considered. The formation of 3-[(2,4-dioxo-3H-chromen-3-yl)(phenyl)methyl]-2-oxo-2H-chromen-4-olate anion in the one-pot reaction was shown to be irreversible.

Chemistry of 1,5-diketones: IV. New aspects of the chemistry of 1,5-Dioxo compounds of the 2H-pyran-2-one series

Reactions of 3,3′-(phenylmethanediyl)bis(4-hydroxy-6-methyl-2H-pyran-2-one) with electrophilic (PCl5, CF3COOH, BF3 · Et2O) and nucleophilic reagents (P2S5) in different solvents were studied. The reactions with boron trifluoride-diethyl ether complex in acetic acid and with trifluoroacetic acid gave 4a-hydroxy-3,7-dimethyl-10-phenyl-10,10a-dihydro-1H,4aH,9H-dipyrano[4,3-b: 3′,4′-e]pyran-1,9-dione, while 3,7-dimethyl-10-phenyl-1,9-dioxo-1H,9H-dipyrano[4,3-b: 3′,4′-e]pyran-5-ium tetrafluoroborate was obtained in the reaction with BF3 · Et2O in diethyl ether. Conditions were found for the synthesis of 4-hydroxy-6-methyl-3-[(6-methyl-2-oxo-4-sulfanyl-2H-pyran-3-yl)(phenyl)methyl]-2H-pyran-2-one by reaction of 3,3′-(phenylmethanediyl)bis-(4-hydroxy-6-methyl-2H-pyran-2-one) with diphosphorus pentasulfide.

Chemistry of 1,5-diketones: II. Specificity of transformations of polycyclic 1,5-diketones in acid media

Abstract2-(1,3-Diaryl-3-oxopropyl)cyclohexan-1-ones underwent carbo-and heterocyclization in a mixture of acetic acid with acetic anhydride in the presence of perchloric acid. The transformation of 2-(1,3-diaryl-3-oxopropyl)cyclohexan-1-ones into 2,4-diaryl-5,6,7,8-tetrahydrochromenylium salts was shown to involve intermediate 2,4-diarylbicyclo[3.3.1]non-2-en-9-ones. The structure of 2,4-diaryl-substituted bicyclo[3.3.1]non-2-en-9-ones and products of their reactions with halogens and hydroxylamine hydrochloride was confirmed by 1H and 13C NMR spectroscopy.

Hydroamination of pyrylium salts

The catalytic reductive amination of pyrylium salts proceeded stereoselectively to give piperidine bases with a cis-structure. The reaction involved the formation of a pyridine intermediate; the course of the reaction depended on the structure of both the substrate and the aminating agent.

New pathway for the disproportionation of hydrothiochromenes and structural studies of the resulting compounds

A new pathway for the disproportionation of hydrothiochromenes under the influence of protic acids, which consists in intermolecular hydride transfer of a hydrogen from the alicycle and leads to the development of a hydrothiochroman, was developed. Correlation results that confirm the structures and conformational peculiarities of the resulting compounds were obtained by PMR spectroscopy and x-ray diffraction analysis.