Vol 66, No 11 (2017)

Data on synthesis, reactivity and bioactivity of N-hydroxy(tetrahydrofuran-2-yl)amines were discussed in the present review. General approaches to chiral N-glycosylhydroxylamines based on reactions of hydroxylamine with cyclic five-membered hemiacetals or dihydrofurans as well as reactions of tetrahydrofuran-containing nitrones with nucleophiles were systematized. The application of N-hydroxy(tetrahydrofuran-2-yl)amines in the synthesis of chiral heterocycles, aminophosphonic acids, N-hydroxypropargylamines, as well as natural compounds (for example, sieboldin A), pharmaceuticals (Zileuton) and their analogs was demonstrated. It was found that depending on substituents, N-hydroxy(tetrahydrofuran-2-yl)-amines can act as lipoxygenase inhibitors, and show antioxidant, antitumor, antibacterial, and other types of activities.

The structures of nine ternary intermetallic compounds (IMCs) of the cerium—rhodium—gallium system containing 50 at.% rhodium were determined by single-crystal X-ray diffraction. The compounds are built up of alternating Ce₂Rh₃Ga fragments with the Mg₂Cu₃Si (MgZn₂ type) or Mg₂Ni₃Si (MgCu₂ type) structure and CeRh₃Ga₂ fragments with the CeCo₃B₂ (CaCu₅ type) structure and form a homologous series of the composition R_2+nT_3+3nM_1+2n (n = 0—5). These compounds can be classified into trigonal (R-3m) or hexagonal (P6₃/mmc) branches depending on the Laves phase-type fragment.

The exchange interaction parameters were calculated and the spin density distribution over the organic skeleton of the 1,3,5,7-tetramethyl-2,6-diazaadamantane N,N’-dioxyl biradical was studied based on the results of quantum chemical modeling of the biradical structure by the DFT method using various hybrid functionals (UB3LYP, LC-wPBE, UCAM-B3LYP, UHSEH1PBE) with the 6-311++G(2d,2p) basis set and by the UHF method with the same basis set. The characteristics of the direct orbital overlap between the N atoms of the two nitroxide groups were determined. The values of the J constant, obtained using different calculation methods, were found to be similar to each other. It was established that there is ferromagnetic exchange interaction between the radical sites in the system in question, which occurs predominantly according to the spin polarization mechanism in the 2,6-diazaadamantane core, and the various spin density transfer pathways through the C atoms of the organic skeleton were found to be nonequivalent. The direct overlap of the upper singly-occupied МОs with localization on the nitroxide groups led to a noticeable additional contribution of the antiferromagnetic exchange interaction. Despite the latter factor, the total contribution of these two mechanisms (spin polarization and direct through-space exchange) resulted in the triplet ground state in the biradical studied.

The electrochemical behavior of phthaloyl peroxide C₈H₄O₄ on an Au disk electrode in a 0.05 M aqueous solution of Na₂SO₄ was studied by cyclic voltammetry (CVA). It demonstrated a high activity in cathodic reduction with the formation of an irreversible peak on the CVA curve at E =–0.81 V. Additionally, during the anodic oxidation of C₈H₄O₄, the surface of the Au electrode became passivated by compounds which prevented its oxidation during the registration of repeated cycles. Apparently, these compounds are surface complexes of phthaloyl peroxide with a gold cation.

The synthesis of novel Cu^II complexes with a Schiff base obtained by condensation of salicylaldehyde and an l-aspartic acid ester are described. The physicochemical properties of the complexes were compared with those of related Cu^II complexes obtained earlier. All the complexes studied were characterized by elemental analysis as well as by IR, UV-Vis, and EPR spectroscopies. The activity of the complexes and their hybrid systems (HS) with TiO₂ in visible-light-driven photocatalysis in organic solvents was investigated. After irradiation with visible light, the complexes and corresponding HS reduce Cr⁶⁺ to Cr³⁺ more efficiently than bare TiO₂. To determine the molecular orbital compositions and energies and to explain the electronic spectra and redox properties of the systems studied, density functional calculations of the optimized structures of representative model complexes were performed.

MFI zeolite materials (ZSM-5) with crystal sizes in the range from 0.10 to 1.70 μm have been synthesized. Acidic and surface properties, phase and morphological composition of the prepared zeolites have been studied by the IR sprectroscopy, nitrogen porosimetry, XRD, and scanning electron microscopy. Increasing crystal size was shown to decrease the general acidity of the zeolite. Synthesized zeolites served as supports for molybden-containing catalysts for methane aromatization prepared by using the solid phase synthesis approach. Diffuse reflectance IR spectroscopy, thermoprogrammed desoption of ammonia and ²⁷Al NMR spectroscopy were used to characterize the physicochemical properties of the catalysts. An increase in the crystallite size of the zeolite favors a decrease in the acidity of the catalysts and inhibits the formation of alumina molybdate during the catalyst preparation. As a result, a tendency to coke formation is suppressed and the performance of the catalysts in methane aromatization improved: methane conversion and aromatic hydrocarbon yield increase.

pH-Potentiometric method in combination with mathematical modeling was used to study the system manganese(ii)—gadolinium(iii)—1-hydroxyethylidenediphosphonic acid (HEDP, H₄L). When both cations simultaneously are present in the solution, the accumulation of heteronuclear forms with the ratio of Gd: Mn: HEDP equal to 1: 1: 1, 1: 1: 2, and 1: 1: 3 was observed already in the strongly acidic pH region, while from homonuclear forms only five complexes were detected in the solution, namely, MnL₂^6–, GdH₄L₂^–, GdH₂L⁺, KGd₂HL₂↓, and K₃Gd₂L₂(OH)↓. It was concluded that heteronuclear complexes are much stronger and replace homonuclear forms in solution.

Synthetic procedures towards 3,3-bis(2-haloethyl) and 3,3,3′-tris(2-haloethyl) derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides) via halogenation of the corresponding 2-hydroxyethyl derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides) and iodination of the corresponding 2-bromoethyl derivatives were elaborated. The synthesized compounds are promising NO donors in the living organisms.

Physicochemical characteristics of microporous zeolites of various structural type (FAU, BEA, MTW), micro-meso-macroporous zeolite (H-Ymmm), and mesoporous aluminosilicate (ASM) were studied. Their catalytic activity in the reaction of aniline with acetone was examined. It was found that 2,2,4-trimethyl-1,2-dihydroquinoline was the main reaction product on the catalysts H-Ymmm and ASM (selectivity up to 68% at 100% conversion of aniline), while the reaction on zeolites with microporous structure mainly gave N-phenyl-2-propanimine (selectivity up to 91%).

N-Substituted imidazo[4,5-e]benzo[1,2-c;3,4-c’]difuroxans were synthesized by phase-transfer catalyzed alkylation of imidazo[4,5-e]benzo[1,2-c;3,4-c’]difuroxan salts with various alkylating agents. Acid hydrolysis of N-(ethoxycarbonylmethyl)imidazo[4,5-e]benzo-[1,2-c;3,4-c’]difuroxans gives the corresponding carboxylic acids. Structures of the synthesized compounds were confirmed by NMR spectroscopy, high resolution mass spectrometry, IR spectroscopy, and elemental anslysis.

The reaction of 4-chloro-2,7,8-trimethylquinoline with 4,6-di(tert-butyl)-3-(piperidin- 1-ylmethyl)-1,2-benzoquinone, which was prepared by the in situ oxidation of 4,6-di(tert- butyl)-3-(piperidin-1-ylmethyl)pyrocatechol with sodium nitrite, gave 4,6-di(tert-butyl)-2- (4-chloro-7,8-dimethylquinolin-2-yl)-7-(piperidin-1-ylmethyl)-1,3-tropolone. Its structure was determined by X-ray diffraction. The energy and structural characteristics of the tauto- mers of this compound in the gas phase and in a polar solution were calculated by quantum chemical methods (PBE0/6-311+G(d,p)).

The method of competing reactions was used to determine the rate constants of the reaction of resveratrol (RVT) with peroxyl radicals formed on decomposition of the azoinitiator ААРН in aqueous solutions at 37 °С. The polymethine dye A (3,3′-di-γ-sulfopropyl-9-metylthiacarbocyanine-betaine pyridinium salt) was used as a competing acceptor of radicals. It was found that resveratrol can be involved in the reaction with natural thiols, glutathione (GSH) and cysteine (CSH), in aqueous solutions at 37 °С. The reaction of RVT with thiols (thiol—еne reaction) follows a chain mechanism and accelerates in the presence of Н₂О₂. The results obtained can be useful for understanding the physiological role of thiols in oxidation processes.

Conjugates containing chlorine and isobornylphenolic fragments, which are connected by spacers of different lengths, were synthesized from methyl pheophorbide a. The toxicity and antioxidant activity of the obtained compounds were studied. Derivatives of pyropheophorbide a containing the most distant from the macrocycle terpenephenolic fragment combine a low toxicity with the high antioxidant activity, and are the most promising for further designing of new medicinal agents for the treatment of diseases associated with a disorder in oxidation-reduction processes in the body.

O-Sialylation of a substituted indolin-3-one under phase-transfer catalysis conditions, which does not occur when N-acetylsialyl chloride is used, proceeds with N,N-diacetylsialyl chloride as the glycosyl donor. A study using dynamic light scattering of solutions of both sialyl chlorides under conditions close to the conditions used for glycosylation showed a difference in the correlation radii of light scattering particles in such solutions. This suggests that the introduction of an additional N-acetyl group into the sialyl chloride significantly alters the structure of the supramers of glycosyl donor, which apparently have an increased accessibility of individual molecules for the attack by a nucleophile, which increases its reactivity.

low-temperature synthesis of saturated fatty acid esters with aliphatic alcohols by enzymatic esterification in the presence of heterogeneous biоcatalysts was suggested. The biоcatalysts were prepared by immobilization of recombinant rPichia/lip lipase on mesoporous silica. A comparison of the reaction rates was used to make up a matrix of biоcatalyst activities and determine a pair of acid/alcohol substrates, for which a maximum esterification rate was observed. A high activity of biоcatalysts was observed in the esterification of fatty acids with seven or more carbon atoms in the molecule. The rate of esterification of fatty acids with primary alcohols (n-C₃—C₁₆ or iso-С₅) was two orders of magnitude higher than that with secondary alcohols (sec-С₃—С₄). The silica-immobilized rPichia/lip lipase possessed a high operational stability; the biocatalyst operated without loss of activity for hun-dreds of hours at 18—22 °С in a non-traditional for enzymes medium of organic solvents.