N. V. Pchelintseva

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.

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.

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.

Halogenation of 1,5-Diketones

Published and experimental data of authors on halogenation of 1,5-diketones from acyclic (among them chalcogen-containing), semicyclic and bicyclic series resulting in formation of mono-, di-, tri-, and tertahalosubstituted 1,5-dioxo compounds, pyrylium halides, and their fused analogs or aroylfurans are reviewed.