Vol 68, No 1 (2019)

The possibilities of using chitosan and its composites with transition metal oxides for arsenic removal from solutions with low concentrations are discussed. Methods for the formation of composite sorbents based on chitosan and molybdenum in a composition with a carbon fiber providing improved physical and chemical properties with respect to the recovered component are considered. The sorption properties of the obtained materials under dynamic conditions for the purification of solutions from arsenic are compared. It is shown that the preliminary modification of the carbon fiber with chitosan by ionic gelation using sulfate ion and then by adsorption with molybdate ion leads to the production of an efficient sorption material that provides the purification of 1600 column volumes of an arsenic solution at an initial concentration of 105 μg L^–1 to a maximum permissible concentration of 50 μg L^–1. The calculation methods show that the gel ability of sulfate and molybdate ions is approximately the same.

The complexes [Et₂H₂N]⁺₂[ZrCl₆]^2– (1), [Me₃NCH₂Ph]⁺₂[ZrCl₆]^2–•MeCN (2), [Ph₃PC₆H₄(CHPh₂-4)]⁺₂[ZrCl₆]^2–•2 MeCN (3), and [Ph₄Sb]⁺₂[ZrCl₆]^2– (4) were synthesized by the reaction of zirconium tetrachloride with tetraorganylammonium, -phosphonium, and -stibonium chlorides in acetonitrile and structurally characterized. The nitrogen, phosphorus, and antimony atoms in the cations have a distorted tetrahedral geometry. The Zr–Cl distances in the centrosymmetric octahedral [ZrCl₆]²⁻ anions of complexes 1–4 have similar values, the longest bonds being observed in the anion of complex 4. Acetonitrile molecules are involved in the structural organization of the crystals of complex 3via weak hydrogen bonding with phenyl hydrogen atoms of the organylphosphonium cations. In the crystal of 2, no hydrogen bonds between the cations and solvent molecules are observed; acetonitrile molecules fill the cavities formed by cations and anions.

The double ionic-polymer complex ([Au(S₂CNPr₂)₂][AgCl₂])_n (1) was prepared as an individual fixation form of gold(III) from NaCl solutions with silver(I) dipropyldithiocarbamate and was characterized by single-crystal X-ray diffraction and ¹³C magic-angle spinning (MAS) NMR spectroscopy. The structure of 1 comprises two nonequivalent centrosymmetric complex cations [Au(S₂CNPr₂)₂]⁺ (A and B) and the discrete linear anion [AgCl₂]^–. Gold(III) cations are linked by pairs of unsymmetrical secondary Au…S bonds to form linear supramolecular chains (…A…B…)n. Neighboring cations are additionally linked by [AgCl₂]^– anions via secondary Ag…S and Cl…S bonds, the anions being involved in the overall stabilization of the supramolecular structure. The cation–anion interactions lead to a distortion of the linear configuration of the [AgCl₂]^– anion. The character of thermolysis of 1 accompanied by quantitative regeneration of bound Au and Ag was established by simultaneous thermal analysis.

Trimethyl orthoacetate was found to be a convenient reagent for methylation of the β-OH groups of (poly)hydroxynaphthazarins. The substrates bearing one β-OH group react with MeC(OMe)₃ to give the corresponding methoxy derivatives in 79–89% yields. Depending on the reaction conditions, methylation of substrates with two β-OH groups on the different and the same rings affords either the corresponding mono-O-methylated (43–70%) or di-Omethylated (71–78%) derivatives. Trimethyl orthoacetate offers a good alternative to CH₂N₂ in the preparative synthesis of O-methylated (poly)hydroxynaphthazarin derivatives.

A heterogeneous system Fe(CrO₂)₂–TiO₂/X (where X is promoter NiO, CuO, ZnO, Cr₂O₃, Fe₂O₃, PrOCl, TbOCl, LaOCl, or EuOCl) was prepared. The photocatalytic activity of the system was tested in the tandem reaction of primary alcohols (BnOH, EtOH) with arylamines aimed at synthesizing benzamides and substituted 2-methylquinolines under aerobic conditions at room temperature.

A series of N- and O-containing derivatives based on 2-hydroxy-3-isobornyl-5-methylbenzaldehyde was synthesized. A comparative evaluation of their radical scavenging activity tested with diphenylpicrylhydrazyl, antioxidant activity estimated on a substrate containing animal lipids, Fe²⁺-chelating ability using the FerroZine™ Iron Reagent, cytotoxicity, and also antioxidant and membrane-protective properties towards mammalian red blood cells was performed. The listed properties of the synthesized derivatives are essentially determined by the structure of the substituent introduced at the ortho-position. Compounds exhibiting a high activity in both cellular and non-cellular models were revealed.

A series of donor-acceptor dyes based on polyfluoro-substituted triarylpyrazolines (as a donor block) and a dicyanoisophorone group (as an acceptor) were synthesized using the Knoevenagel condensation. The dyes have an absorption in the region of 509–514 nm and intense luminescence at 648–663 nm in chloroform with a large Stokes shift (up to 4410 cm^–1). Based on the synthesized dyes, chromophore–polymer (guest–host) films were obtained in a polycarbonate matrix with a chromophore content up to 27 wt.%. Poling of chromophore–polymer films was carried out in an electric field of a corona discharge and the coefficient of nonlinear optical response d₃₃ was measured by the second-harmonic generation method of the fundamental frequency of a Nd-YAG laser (1064 nm). The obtained films have a high initial thermal stability and a nonlinear optical response up to 80 pm V^–1, which persists up to 115 °С.

A new method for the synthesis of 2-unsubstituted and 2-substituted 3-(N-arylcarbamoyl)-chromones by the reaction of 3-dimethylamino-1-(2-hydroxyaryl)prop-2-en-1-ones with arylisocyanates has been proposed.

The use of the T₂ filter in NMR studies allowed us to separate carbon atoms by their mobility in different fragments of the macromolecular chain of polyisoprene synthesized by cationic polymerization. The NMR signals of terminal units with conjugated double bonds were identified for the first time for the “cationic” polyisoprene, which experimentally confirmed the transfer of the growing chain to the monomer in the process of cationic polymerization of isoprene.

The hydrolytic copolycondensation (HPC) of trifunctional monomers RSiX₃ (R = Ph, Me; X are hydrolyzable RO or Cl groups) in nonaqueous organic solvents (toluene, dioxane) was studied. The in situ generation of water necessary for hydrolysis occurred via the reaction of carbamide with acetone or acetylacetone. The cascade synthesis of silsesquioxanes was carried out under the conditions of in situ water generation in nonaqueous media with the quantitative yield of organochloro- and alkoxysilanes from the reaction mixtures. The influence of the conditions of cascade HPC on the compositions, structures, and molecular weight characteristics of the obtained products was studied by GPC, ¹H and ²⁹Si NMR, and GC coupled with mass spectrometry.

Derivatives of the amino acids sarcosine and proline – triflates TsN(Me)CH₂C(O)N(Me)-CH₂SiMe₂OTf and Ns–Pro–N(Me)CH2SiMe2OTf (Ns is 4-NO₂C₆H₄SO₂) – were synthesized by the reaction of trimethylsilyl triflate with halosilanes prepared previously. Bromide NsNHCH(Me)C(O)N(Me)CH2SiMe2Br was synthesized by the cleavage of the Si–O–Si moiety of the appropriate disiloxane with excess acetyl bromide. The X-ray diffraction study of these compounds and of the previously characterized bromide TsN(Ac)CH₂C(O)N(Me) CH₂SiMe₂Br showed that the Si–O coordination bond lengths in the triflates are 1.7692(14)– 1.8623(14) Å. The interatomic distances between the bromine and silicon atoms are 2.7095(8) and 2.9704(7) Å, which indicates that these bonds are weak. To elucidate the nature of Si…X bonding (X = OTf, Br), the topological analysis of electron density was performed and ²⁹Si NMR chemical shifts were calculated. The interatomic Si…X interaction in triflate TsN(Me)CH₂C(O)- N(Me)CH₂SiMe₂OTf and bromide TsN(Ac)CH₂C(O)N(Me)CH₂SiMe₂Br is weak. In triflate Ns–Pro–N(Me)CH₂SiMe₂OTf and bromide NsNHCH(Me)C(O)N(Me) CH₂ SiMe₂Br, the Si…X interaction is significantly stronger and corresponds to a weak coordination bond. Hence, the tosylates can be considered as salts, whereas the para-nitrobenzenesulfonyl derivatives are monochelated five-coordinate silicon complexes.

Hetarylfuroxans (4-(2-methylpyridin-5-yloxy)-3-phenylfuroxan (1), bis(1,2,4-oxadiazol- 3-yl)furoxan (2), and 4-amino-3-(indenotriazin-3-yl)furoxan (3)) exhibit in vitro cytotoxic activity against chronic myeloid leukemia K562 cells. All studied furoxans induce apoptosis in K562 cells. The experiments with activation of caspases-3 and -7 showed that furoxan 3 possessed the highest apoptosis-inducing capacity. The studied hetarylfuroxans were found to be the promising drug candidates for the treatment of chronic myeloid leukemia K562.

The structural optimization of adaptaquin, viz., 7-(4-chlorophenyl)[(3-hydroxypyridin-2-yl)amino]methylquinolin-8-ol, a HIF (hypoxia inducible factor) prolyl hydroxylase inhibitor, was carried out. This was done by cell-based screening using cell lines stably expressing a reporter construct consisting of the fusion protein of HIF oxygen-dependent domain and firefly luciferase (HIF1 ODD-luc). More than 100 structural analogs of adaptaquin were screened and the structures active in the submicromolar range were selected. The highest activity was found for analogs containing isobutyl, isopropyl, trifluoromethyl, and nitro group or halogen atom in the para-position of the benzene ring, but not a dimethylamino group or more bulky substituents. The lack of dependence on the donor-acceptor properties of substituents attests to predominance of the steric effect. The presence of methyl group in positions 3 and 5 of the pyridine ring provides additional activation. The 2-methyl group present in the hydroxyquinoline scaffold (50 compounds in the set) prevents coordination of the inhibitor in the active site and significantly reduces the activation. According to the real-time PCR results, the newly improved adaptaquin analog induces HIF target genes 15-times more efficiently than the FG-4592 inhibitor developed by Fibrogen.

Two new compounds from the class of bis(3-halopropionyl)amides were synthesized by the reaction of 3-halopropionyl chloride with N,N′-dimethylethylenediamine. These structural analogs of prodimin, a water insoluble anticancer drug, are soluble in water, which significantly expands methods for their administration into a body. The compounds obtained and prodimin (as a reference substance) were studied on P388 murine leukemia and some of its drug-resistant strains. The data obtained suggest a high efficacy of one synthesized compound against drug-resistant tumors.

The reaction of 2-[(2-azidophenyl)hydrazono]-2-(tert-butyl-NNO-azoxy)-N′-hydr oxyethanimidamide with sodium acetate in DMF aff ords 2-(2-aminophenyl)-5-(tert-butyl-NNO-azoxy)-2H-1,2,3-triazol-4-amine 3-oxide rather than the anticipated 2-(2-azidophenyl)-5- (tert-butyl-NNO-azoxy)-2H-1,2,3-triazol-4-amine. The formation of this product can be explained by intramolecular reduction of azido to amino group and cyclization of an inter mediate vicinal (azo)nitrosoethylene into a triazole 3-oxide ring. The structure of aminotriazole 3-oxide 10 was confirmed by X-ray diff raction and NMR spectroscopy.