G. V. Gavrilova

Synthesis, structure, electrochemistry, and photophysics of 2,5-dibenzylidenecyclopentanones containing in benzene rings substituents different in polarity

A series of cross-conjugated dienones was synthesized to study the dependence of physicochemical characteristics on the nature of substituents in the aromatic groups of symmetric cyclopentanone dibenzylidene derivatives. The structure of compounds was established by electronic, IR, and NMR spectroscopy and X-ray diffraction study. All the compounds obtained possess the E,E-geometry. In the crystalline state, the arrangement of the dienone molecules is unfavorable for the intermolecular [2+2] photocycloaddition to take place. The low-temperature phases transition for unsubstituted diphenyl derivative of cyclopentanone was detected using variable-temperature X-ray diffraction and differential scanning calorimetry. Oxidation and reduction potentials of the dienones were measured by cyclic voltammetry. Their dependence on the nature and placement of substituents in the benzene rings was demonstrated. A linear correlation (R = 0.9343) between the difference of electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum was found, that allows us to recommend the use of the data obtained in the correlation analysis of other compounds of this class.

1,7-Dimethyl-1,7-dichloromethyl-5,8-ethenodecalin-3-ene-2,6-dione. Structure, bromination, electrochemistry

The structures of 1,7-dimethyl-1,7-bis(dichloromethyl)-5,8-ethenodecalin-3-ene-2,6-dione, the dimer of 6-methyl-6-dichloromethyl-cyclohexa-2,4-dien-1-one, and of products of its bromination were established by XRD analysis. The dependence of composition of the products of bromination on the ratio of reactants was established. Electrochemical reduction of the dione and its bromine-containing derivatives was studied.

Electrochemically induced transformation of 4-halomethyl-4-methylcyclohexa-2,5-dien-1-ones into 3,4-dimethylphenol

Electrochemical behavior of 4-halomethyl-4-methylcyclohexa-2,5-dien-1-ones and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one was studied. Reductive dehalogenation of cyclohexa-2,5-dien-1-ones having a halogen atom at the neopentyl-like carbon atom gives the corresponding carbanion which undergoes anionic cyclopropyl-allyl rearrangement with subsequent addition of proton to form 3,4-dimethylphenol.

Bromination of 6-Dibromomethyl-6-methylcyclohexyl-2,4-dien-1-one

Bromination of 6-dibromomethyl-6-methylcyclohexyl-2,4-dien-1-one (I) with molecular bromine was studied at different ratios of reactants and varied reaction time. A number of tri-, tetra-, penta-, and hexabromo derivatives was obtained, which were characterized by 1H, 13C, IR, UV spectroscopy and elemental analysis. The molecular structure of (2R,3R,4S,5S,6R)-2-dibromomethyl-2-methyl-3,4,5,6-tetrabromocyclohexan-1-one (V) was revealed using XRD. It was shown that 2-bromo-6-dibromomethyl-6-methylcyclohexyl-2,4-dien-1-one (III) upon standing for six months at room temperature dimerized quantitatively via Diels-Alder reaction to form IX. Dimer IX was investigated by the methods of cyclic voltammetry (CVA) and rotating disk electrode (RDE) in a solution of DMF on glassy carbon electrode.

Electrochemically induced transformation of 4(6)-dihalomethyl-4(6)-methylcyclohexa-2,5(2,4)-dien-1-ones into 4(2)-methyltropones

Electrochemical investigation of 4(6)-dihalomethyl-4(6)-methylcyclohexa-2,5(2,4)-dien-1-ones using cyclic voltammetry (CVA) and rotating disc electrode (RDE) methods has been performed. The reductive dehalogenation of cyclohexa-2,5(2,4)-dien-1-ones having a dihalomethyl substituent at the tertiary carbon atom was shown to proceed as a two-electron reductive elimination of the geminal halogen atoms with the intermediate formation of carbene and subsequent rearrangement of cyclohexadienone with the ring expansion to the corresponding 4- or 2-methylcyclohepta-2,4,6-trien-1-one.

Redox troponization of 4-methyl-4-dibromomethyl-2,5-cyclohexadien-1-one by the action of Pd(PPh3)4

ConclusionsThe feasibility of using gem-dihalomethyl-substituted cyclohexadienones in redox troponization reactions was shown in the case of the reaction of 4-methyl-4-dibromomethyl-2,5-cyclohexadien-1-one with Pd(PPh3)4, leading to the formation of 4-methy1-2,4,6-cycloheptatrien-1-one.

Effect of substituents on spectral, luminescent and time-resolved characteristics of 2,5-diarylidene derivatives of cyclopentanone

Spectral, luminescent and time-resolved characteristics of 2,5-dibenzylidenecyclopentanone and its symmetrical derivatives (bis(N,N-diethylamino-), dimethoxy-, tetramethoxy-, dimethylthio-, and bis-18- crown-6 derivative) have been studied in media of different polarity (cyclohexane, toluene, acetonitrile, DMSO, and methanol) at room temperature. The absorption maximum of dibenzylidenecyclopentanone shifts bathochromically by 15 nm with an increase in polarity of the medium (cyclohexane–methanol). The introduction of electron-donating substituents in the aromatic rings of dibenzylidenecyclopentanone also results in a bathochromic shift of the absorption maximum by 100–130 nm in the media of different polarity and shifts the fluorescence maximum by 130 nm relative to the maximum of the dimethoxy derivative. Upon laser irradiation of oxygen-free solutions of dibenzylidenecyclopentanone and its tetramethoxy- and bis-18-crown-6 derivatives in acetonitrile, the triplet state with a half-life time of 0.3–1 μs is generated. For dimethoxy-, dimethylthio-, tetramethoxy-, and bis-18-crown-6 derivatives of dibenzylidenecyclopentanone, the isomers with a lifetime of ~50 ms are formed.

Electrochemical reduction of 4-methyl-4-(trichloromethyl)cyclohexa-2,5-dien-1-one

The properties of 4-methyl-4-(trichloromethyl)cyclohexa-2,5-dien-1-one which contains the trichloromethyl substituent at a quaternary carbon atom have been studied by cyclic voltammetry, rotating disk electrode voltammetry, and preparative electrolysis. Reductive dehalogenation involves initial two-electron reductive elimination of one of the geminal chlorine atoms followed by consecutive addition of proton, simultaneous elimination of the two residual halogen atoms to form carbene, and rearrangement of cyclohexadienone into the corresponding 4-methylcyclohepta-2,4,6-trien-1-one.

Aromatized protonation of exo-element-substituted semiquinoid systems

We recently showed that trienes of the exo-methylenedihydroarene type (I) can be aromatized by electrophilic agents E + (E = HgCI) with the formation of heteroorganic benzyl compounds (path A), and we advanced the hypothesis that this rearrangement takes place through an intermediate a-complex (II) [i]. However, similar o-complexes can also be generated in principle by a different path, namely, protonation of the corresponding exo-element-substituted alkylidenedihydroarenes such as (III), opening up the possibility of one more new path to the synthesis of heteroorganic benzyl compounds (path B):

Transfer of the reaction center during deuterodemetallization of substituted benzylmercury chlorides

1. The distribution of deuterium in the products of deuterometallization of o-, m-, and p-methyl-, 3,5-dimethyl-, and 2,4,6-trimethylbenzylmercury chloride by reaction with deuterium chloride was investigated. 2. The presence of deuterium in the benzene nucleus of the products of deuterodemetallization of o-,m-, and p-methyl-and 3,5-demethylbenzylmercury chloride is due mainly to the transfer of the reaction center from theα-carbon atom to the nucleus.