Vol 65, No 3 (2016)

The supermolecule method was used to describe the mechanism of liquid-phase processes taking the reaction of ethylene carbonate with methylamine as an example. Specific features of the approach are considered. The problem of choosing the reference point for calculating the relative energies of individual reaction steps was solved by introducing the idea of the structure of noninteracting solvated reactants. In this case, no basis set superposition error (BSSE) correction is required because the solvated reactants, the pre-reaction complex, and the transition state have the same atomic composition and are calculated in the same basis set. To calculate the title reaction in dioxane by the supermolecule method with acceptable accuracy, it is sufficient to consider one solvent molecule.

The geometric, charge, and electronic characteristics of 7-substituted pyrido[1,2-a]benzimidazoles and their cations were calculated using the DFT method with the B3LYP functional in the 6-31G** basis set. High regioselectivity of the reactions between the condensed imidazole derivatives and electrophilic agents was explained by the results of quantum chemical simulation. It was concluded that the S_EAr reaction was orbitally controlled. According to Fukuís concept, the reaction center of the electrophilic attack was the C(8) atom of the heterocyclic system, which agreed well with the experimental data.

Quantum chemical calculations of the energies, electronic structures, and molecular geometries of 5-methyl-, 2,5-dimethyl-, 3,5-dimethyl-, and 2,3,5-trimethyl-4-oxothieno[2,3-d]pyrimidine-6-carboxylic acids; 5-methyland 3,5-dimethyl-2,4-dioxothieno[2,3-d]pyrimidine6-carboxylic acids; 5-methyland 3,5-dimethyl-4-oxo-2-thiothieno[2,3-d]pyrimidine-6-carboxylic acids; and their ethyl esters were performed in terms of the HF and DFT (B3LYP) approximations in the 3-21G basis set. The reactions routes with nitrating agents were examined, and the factors governing the direction of the reactions, the probability of their occurrence were determined. Selective ipso-substitution of the 5-methyl group by the nitro group at the C(5) atom of the thiophene fragment is hindered for all compounds studied. The reasons for the unfavorable ipso-substitution were discussed taking into account effects of solvents and substituents in positions 2, 3, and 6 of 6-carboxyand 6-ethoxycarbonyl-substituted thieno[2,3-d]pyrimidin-4-ones.

5-Formylpyrrolyl-substituted nitronyl and imino nitroxide radicals HL¹ and HL² were synthesized. Their solid phases are formed by packing pairs of the molecules. In the {HL¹...HL¹} pairs, the dominant interaction is the ferromagnetic exchange with J/kB = 8.8 K (Hamiltonian \(H = 2J\left( {\overrightarrow {{s_1}} \overrightarrow {{s_2}} } \right)\)). The ferromagnetic exchange occurs also in the heterospin molecules [Ni(L¹)₂], [Cu(L¹)₂], and [Ni(L²)₂(MeOH)₂]. In the complexes [Ni(L¹)₂] and [Cu(L¹)₂], a small change in the mutual orientation of the coordinated ligands has a considerable effect on the value and the sign of the energy of exchange interactions between the unpaired electrons of the metal ion and paramagnetic ligands.

Diamidophosphite ligand bearing (1R,2R)-1,2-bis(3-hydroxybenzamido)cyclohexane fragment and stereogenic phosphorus atoms in the 1,3,2-diazaphopholidine cycles was synthesized. Catalytic performance of this ligand was evaluated in asymmetric allylic substitution. In the reactions involving (E)-1,3-diphenyl allyl acetate as a substrate, up to 94% ee in alkylation with dimethyl malonate and up to 68% ee in amination with pyrrolidine was achieved in the presence of this ligand.

It was proved thermodynamically that He and Ne form the respective gas phases in water and that the thermodynamic parameters of the transfer of He and Ne from their phases to the bulk of the liquid are independent of the latter.

Peculiarities of electrochemical behavior of the Fe₃O₄ magnetic nanoparticles immobilized on the surface of a platinum electrode in aprotic organic media were investigated. Possible scheme of electrochemical behavior of nanoparticles depending on pre-electrolysis potential (–1.3,–2.5 V) was suggested. The effect of pre-electrolysis time, potential scan rate and nature of supporting electrolyte on the processes investigated was determined. A linear dependence of electrochemical oxidation signal versus the concentration of nanoparticles in modifying suspension in the concentration range of 0.05—0.5 g L^–1 was observed. The results of the performed research allow using magnetite nanoparticles as a direct signal-generating label in electrochemical immunoassay.

Reactions of 3-hydroxyalkan-2-ones with (hetero)aromatic aldehydes under basic conditions lead to 4-aryl-1,7-dihydroxyalkane-2,6-diones. These products were also synthesized by dismutation of 4-aryl-1-hydroxyalk-3-ene-2-ones. The reactions proceed as tandem retro aldol reactions and the Michael addition.

Heating of an equimolar mixture of 3,5-di-tert-butyl-1,2-benzoquinone with thiosalicylic acid led to 2-[(4,6-di-tert-butyl-2,3-dihydroxyphenyl)thio]benzoic acid. In the case of β-mercaptopropionic acid, 2-[(4,6-di-tert-butyl-2,3-dihydroxyphenyl)thio]propionic acid was formed, which upon reflux in Ac2O was converted to 6,8-di-tert-butyl-9-hydroxy-3,4-dihydro-2H-1,5benzoxathiepin-2-one.

Aryl(hetaryl)pyrazolines are effective photogenerators of acid providing an irreversible photochemical activation of fluorescence of rhodamine group dyes. The effect of solvent on two consecutive reactions, photodehydrogenation of pyrazoline and lactone ring opening of the dye was studied. An increase in solvent polarity leads to an increase in the rate of both reactions by different degrees. The systems under study are believed to be promising for the formation of recording media for multilayer optical file type disks of ultrahigh data storage capacity with fluorescent readout.

Synthetic procedures towards a series of new high energy N-(2,2,2-trinitroethyl) derivatives of polynitrohexaazaisowurtzitanes were elaborated; the properties of the synthesized compounds were studied.

Ordered structures of polymer microspheres of various diameters (6–200 μm) were prepared on a water surface followed by transposition and fixation on a solid surface (glass). A formation mechanism of hexagonal packing from polymer microspheres on a water surface was proposed. Processes of defect occurrence in formation of the ordered structures both on a water surface and on a solid glass surface have been analyzed.

Нydrolytic polycondensation of organochlorosilanes (OCS) RR´SiCl₂, where R,R´= Me, Et, C₂H₃, and H, in an acetone—carbamide non-aqueous system was studied. It was found by GLC, GPC, ²⁹Si NMR spectroscopy, mass spectrometry, and elemental analysis that linear and cyclic oligoorganosiloxanes were formed in a quantitative yield as a result of hydrolysis. The mechanism of the process includes conjugate mutually dependent reactions: (i) generation of water via dehydrocondensation of acetone and carbamide involving HCl and (ii) hydrolysis of OCS to form HCl. This determines the cascade character of the overall process. The hydrolysis of OCS in the system studied develops with autoacceleration like branched cascade processes because of peculiarities of stoichiometry of the dehydrocondensation of acetone and carbamide.

The kinetic regularities of nitric oxide donation in the presence of erythrocytes by representatives of a new class of synthetic nitric oxide donors, binuclear tetranitrosyl iron complexes (B-TNIC) [Fe₂(SR)₂(NO)₄] with thiol-containing ligands, where R is pyrimidin-2-yl, 1-methylimidazol-2-yl, benzothiazol-2-yl, and penicillamine residue, were established. The NO-donating ability of B-TNIC was estimated from the apparent rate constants of the first order for the formation of intraerythrocyte methemoglobin with the variation of the initial concentration of the complex. During the standard experimental time (15—17 min), three of the four complexes released in the solution no more than a quarter of available NO groups. Their NO-donating ability turned out to be variable increasing with an increase in the initial concentration of the complex. At the same time, the complex bearing penicillamine residues as ligands donated almost all NO groups within approximately 1 min. Features of NO donation by the B-TNIC in the presence of erythrocytes are related to the formation in the system of an additional equilibrium pool of the membrane-associated complex, which is characterized by a reduced rate of hydrolytic dissociation with NO releasing to the solution. The NO-donating ability of the B-TNIC in the presence of erythrocytes is determined by the ratio of volumes of the free and membrane-associated pools of the complex.

The method of immobilization of chymotrypsin based on the reduction reaction of silver nitrate with sodium borohydride in an aqueous medium in the presence of the enzyme was developed. Chymotrypsin was simultaneously a stabilizer of silver nanoparticles in solution. The dimensional characteristics, as well as proteolytic and bactericidal activity of the synthesized nanocomposites were studied. It is shown that the hybrid organic-inorganic nanocomposites based on chymotrypsin and silver nanoparticles are able to perform an increased proteolytic activity in comparison with the native enzyme in the pH range corresponding to wound surface, and suppress pathogenic flora of various microorganisms.

Monoand disubstituted N-hydroxyamides of dicarboxylic acids were prepared by reaction of dicarboxylic acids or acid anhydrides with hydroxylamine. The use of these compounds in combinatorial cytostatic therapy of implanted tumors with cisplatin or cyclophosphamide totally inhibits metastasis formation in B16 melanoma and Lewis lung carcinoma, and resulted in 100% survival of leukemic animals.

The crystal and molecular structure of the reaction product of imidazolidine-2-thione and molecular iodine of the composition (C₃H₆N₂S)2•3I₂ was established by X-ray diffraction. The crystal structure is composed of strongly connected five-component associates consisting of three I₂ molecules and two heterocyclic molecules. Quantum chemical calculations followed by the topological analysis of the electron density function provided an estimate of the strongest intermolecular interactions in the crystal structure of the molecular adduct.

An approach to the synthesis of earlier unknown androstano[17,16-d]pyrazoles containing a monothiooxamide fragment at the nitrogen atom of the pyrazole ring has been suggested. The method is based on the reaction of NH-unsubstituted androstano[17,16-d]pyrazole with chloroacetyl chloride with subsequent involvement of the obtained N-chloroacetylpyrazole into the reaction with elementary sulfur in the presence of aromatic amines. The synthesized androstano[17,16-d]pyrazoles containing a monothiooxamide fragment at the nitrogen atom of the pyrazole ring exhibit high antiparasitic activity.

New potentially pharmacologically active tris(2-hydroxyethyl)hydroxyammonium salts were synthesized by the reaction of triethanolamine N-oxide with biologically active acetic acid derivatives RYCH₂CO₂H (R = Ar, 3-indolyl; Y = O, S, SO₂).

Cotarnine chloride reacts with terminal acetylenes with short-time heating in acetonitrile in the presence of the catalytic system CuI—morpholine to form cotarnine 1-alkynyl derivatives.

Tin(II) alcoholates Sn(OR)₂ are formed upon the anodic galvanostatic dissolution of tin in alcohols in an undivided cell in the presence of minimum amounts of NaOAc as an electrolyte. Tin(II) alcoholates are easily hydrolyzed in air to form oxyhydroxide Sn₃O₂(OН)₂ used as an anode or its composite component in lithium cells.