Volume 66, Nº 3 (2017)

Principal synthetic approaches to the synthesis of indole-5,6- and carbazole-2,3-dicarboxylic acid functional derivatives are considered. The first of them consists in the construction of the indole ring from simpler aromatic compounds containing carboxy groups, cyano groups, or an imide fragment with subsequent reductive cyclization of the compounds formed. The second approach is based on the modification of a pyrrole or an indole fragment by the introduction of different functional groups with subsequent intramolecular cyclization to the corresponding heterocycles.

Modeling of the interaction of an H₂ molecule with the surface of the Pd₂₁ cluster in different spin states was performed using the DFT/PBE scalar relativistic approximation. The spin multiplicity of the system significantly affects the mechanism of adsorption, its parameters, and migration of hydrogen atoms. The H atoms can migrate over the cluster surface with low barriers (1.6 kcal mol^–1). The complex with C_2v symmetry, wherein the H atoms occupy adjacent fcc sites, is the most energetically stable.

Methods for synthesis and optimum conditions of the formation of stable water-soluble silica nanoparticles are presented. The silica nanoparticles were synthesized by the hydrolytic polycondensation of tetraethoxysilane using two methods: under alkaline conditions (Stöber´s method) or in an acetic acid medium followed by the modification by grafting triethylene oxide moieties on the particle surface. The structure of the modified silica nanoparticles was confirmed by the data of IR and NMR spectroscopy. Polydispersity was evaluated by gel permeation chromatography and dynamic light scattering. The formation and stability of Langmuir monolayers of the silica nanoparticles modified by triethylene oxide moieties were studied.

The compound [{Re₆S₈}(3,5-Me₂pzH)₆]₂[{Re₆S₈}Br₆]•9H₂O•4EtOH containing a cluster cation and a cluster anion in a 2: 1 ratio was synthesized by mixing an ethanol solution of the rhenium cluster complex [{Re₆S₈}(3,5-Me₂pzH)₆]Br₂•2(3,5-Me₂pzH) (pzH is pyrazole) with an aqueous solution of Cs₄[{Re₆S₈}Br₆]•2H₂O. The resulting compound was characterized by a combination of physicochemical methods. In particular, luminescence properties were studied and compared with those of the parent cluster complexes. A crystal suitable for single-crystal X-ray diffraction was obtained by layering these solutions. According to single-crystal X-ray diffraction analysis, this compound is composed of a cluster cation and a cluster anion (in a ratio of 1: 1) and also of Zundel cations (H₅O₂⁺) and solvate water molecules and is described by the formula (H₅O₂)₂[{Re₆S₈}(3,5-Me₂pzH)₆][{Re₆S₈}Br₆]•4H₂O.

The theoretical investigation of phase formation processes in systems Са(NO₃)₂—(NH₄)₂НРО₄—Na₂SiO₃—H₂О was carried out at the varied concentration of phosphate ions, Si/P molar ratio, and pH taking into account the absorption of CO₂ from air. The formation of hydroxyapatite is most probable in aqueous solutions as it was established by the results of calculation of the change in the Gibbs energy of crystallization. The supersaturation of the systems with respect to calcium silicate and calcite and thermodynamic probability of their precipitation together with basic calcium phosphate increase with an increase in the alkalinity of the reaction medium. The formation of mixtures of poorly crystallized nonstoichiometric calcium phosphate and calcium silicate was experimentally detected in the studied media. The method of precipitation from aqueous solutions can be used to produce composites based on these salts for biomedical purposes.

A model experiment was conducted in order to determine an interplay between inherent strains and electrochemical corrosion rate in nitrogen-doped iron thin films. 150 and 300 nm thick films, used in the experiment, were obtained by means of DC magnetron sputtering. In order to study the influence of substrate on inherent strains in metal, these films were deposited onto flexible polymer and rigid glass substrates. It was found, that the rigidity of the substrate increased the corrosion rate of thin iron films in a neutral electrolytic solution. It was proven using X-ray diffraction, that the greater rigidity was, the stronger were the internal strains within the films. That effect was especially pronounced in thinner films, where the increase in the rate of dissolution was accompanied by a localization of corrosion. Characteristics of electrochemical processes were measured using a three-electrode cell. The comparison of the films free surface energy was performed by measuring water contact angle.

The kinetics of radiation telomerization of tetrafluoroethylene (TFE) in trifluoroethanol and hexafluoropropan-2-ol (HFIP) has been investigated by method of kinetic calorimetry. The nature of active centers initiating the process of telomerization of tetrafluoroethylene in hexafluoroisopropanol in the temperature range of 77—300 K was investigated by ESR spectroscopy. The molecular structure and properties of the obtained telomeres were studied by IR spectroscopy and TGA.

The electroreduction of N-(3-nitrophenyl)hydroxylamine in DMF was studied using cyclic voltammetry, chronoamperometry, and numerical simulation. It is shown that the stability of formed radical anion is significantly higher than that of the radical anion of the 4-nitrophenyl derivative. In the range of low concentrations and high potential scan rates, the electroreduction of N-(3-nitrophenyl)hydroxylamine is complicated only by the formation of complexes between the depolarizer molecules, most likely, due to hydrogen bonds, as well as between the depolarizer and its radical anion. The thermodynamic and kinetic parameters of these processes were evaluated.

Aldol condensation of acetone was studied over solid base CaO—SnO₂ catalyst in the 300—450 °C temperature range and at 15—75 atm pressure in a fixed-bed reactor. The main products are mesityl oxide and isophorone. The high stability of CaO—SnO₂ catalyst performance was observed at pressure of 75 atm giving the acetone conversion of 36—41%. Increase in the temperature and pressure led to a simultaneous raise in acetone conversion. The maximum conversion of 41% was achieved at 400 °C, 75 atm and a flow rate of acetone of 8.1 g h^–1 (g catalyst)^–1.

The effects of substituents in lithium, magnesium, zinc, and cadmium organometallic compounds in their reactions with p-benzoquinone and 3,6-di-tert-butyl-o-benzoquinone on the ratio of addition and reduction products were considered. The reduction of quinones follows a homolytic mechanism of single electron transfer. The results of correlation analysis confirmed a suggestion that the addition to quinones followed a nucleophilic (heterolytic) mechanism.

A reaction of 3-allyl- and 3-phenylthiohydantoins with 1,5-diphenyl- and 1-phenyl-substituted 3-formyl-2-pyrazolines was used to obtain a series of 5-(pyrazolin-3-ylmethylidene)-2-thioxotetrahydro-4H-imidazol-4-ones, the subsequent alkylation of which with methyl iodide or ethyl chloroacetate gave the corresponding 2-alkylthio-5-(pyrazolin-3-ylmethylidene)-3,5-dihydro-4H-imidazol-4-ones in the yields from 30 to 77%. The oxidation of (5Z)-3-phenyl-5-[(1,5-diphenylpyrazolin-3-yl)methylidene]-2-methylsulfanyl-4,5-dihydroimidazol-4-one with lead tetraacetate led to the corresponding pyrazole in 48% yield.

A method for the synthesis of previously unknown pyrido[3´,2´:4,5]thieno[3,2-c]isoquinolin-5(6H)-ones was suggested, which includes a condensation reaction of substituted 3-cyanopyridine-2(1H)-thiones with methyl 2-(chloromethyl)benzoate and subsequent treatment of the condensation products with potassium tert-butoxide. The oxidation of the condensation products to sulfoxides or sulfones and subsequent treatment of these compounds with potassium tert-butoxide led to substituted pyrido[3´,2´:4,5]thieno[3,2-c]isoquinolin-5(6H)-one 11-oxides or substituted pyrido[3´,2´:4,5]thieno[3,2-c]isoquinolin-5(6H)-one 11,11-dioxides.

A protocol to access ferrocenecarboxylic acid via carboxylation of ferrocene with carbon dioxide in the presence of aluminum chloride was elaborated. An efficient microwave-assisted synthesis of ferrocenoyl hydrazones by condensation of ferrocene carbohydrazide with carbonyl compounds was developed. Structures of the synthesized compounds were examined by NMR spectroscopy and mass spectrometry. Structures of N´-(4-chlorobenzylidene)ferrocenecarbohydrazide, N´-(4-methoxybenzylidene)ferrocenecarbohydrazide, and N´-(2-hydroxybenzylidene)ferrocenecarbohydrazide were determined by X-ray diffraction analysis. Synthesized compounds were found to have no toxicity against P. aeruginosa, E. coli, S. aureus, B. subtilis, M. rubrum, and C. albicans.

An approach to modify biologically active carbazoles and tetrahydrocarbazoles with 2-trifluoromethyl and 2-methoxycarbonyl(imidazo[1,2-a]pyridin-3-yl)propionylamidic fragments by interaction of N-methyl-N-[2-trifluoromethylimidazo[1,2-a]pyridin-3-yl]prop-2-ene amides and N-methyl-N-[2-methoxycarbonylimidazo[1,2-a]pyridin-3-yl]prop-2-ene amides with carbazoles and tetrahydrocarbazoles in the presence of catalytic amounts of cesium fluoride was proposed. Effect of compounds synthesized on neuronal NMDA receptors using radioligand binding method was studied.

A method was proposed for the calculation of changes in the rate (k_P/k_P=0) and equilibrium constants (K_P/K_P=0) for chemical reactions under high hydrostatic pressure (10—20 kbar). The calculation based on the activation and reaction volume data makes it possible to select optimum conditions for slow and equilibrium chemical processes.

A reaction of bicyclic 2-sila-5-piperazinone, 2,2,4-trimethyl-1,4-diaza-2-silabicyclo-[4.3.0]nonan-5-one containing a proline moiety, and N-tosylglycine acyl chloride with subsequent hydrolysis of the primary unstable product to the intermediate disiloxane and its treatment with BF₃•OEt₂ furnished a first representative of pentacoordinate C,O-chelate halosilanes with a dipeptide fragment, namely, Ts—Gly—(S)-Pro—N(Me)CH₂SiMe₂F.