Vol 65, No 12 (2016)

The Pd, Mn, La, and Rh complexes with the heterocyclic azo compounds were studied by the laser-induced electron transfer desorption/ionization (LETDI) method. The optimum parameters of laser irradiation were found, and the compositions of the complexes were determined. The quantum chemical simulation of the compositions of the complexes was performed on the basis of the data of mass spectrometry. It is shown that laser-induced electron transfer desorption/ionization is an effective tool for the high-sensitive determination and identification of metal complexes.

The surfaces of the alloy based on Zr₂Ni doped by silicon (3 at.%) in the amorphous and crystalline states and of the Zr and Ni foils were electrochemically modified for the first time. The modification was carried out in the ionic liquid in the galvanostatic regime. The much more uniform distribution of the nanosized fragments can be obtained and stability of their geometric shapes can be retained in the absence of intergrain boundaries and texture in the amorphous materials.

Two novel binuclear nickel(II) complexes [Ni₂(O₂CR)₄(2,3-lut)₂] (O₂CR is anion of 3,5-di(tert-butyl)benzoic acid (bzo, 1) and 4-hydroxy-3,5-di(tert-butyl)benzoic acid (hbzo, 2); 2,3-lut is 2,3-lutidine) with four carboxylate bridges were synthesized. The structure of complex 1 was determined by X-ray diffraction. Both dimers 1 and 2 were characterized by elemental analysis, IR spectroscopy, and magnetic measurements. The presence of the α-substituent in the apical lutidine ligand leads to a distortion of the geometry of the metal carboxylate core in complex 1 as a result of short steric contacts Me(Lut)…O(OOCR) (3.134(7) Å). This is apparently responsible for a considerable decrease in the exchange parameters of complexes 1 and 2 (J =–30.0 and–23.6 cm^–1, respectively) as compared to known analogues. Density functional calculations of the structure and magnetic properties of 1 and 2 were carried out by the UB3LYP/6-31G(d,p) method.

The interaction kinetics of the cationic and anionic polymethine dyes with radicals has been studied. Azoinitiator AAPH, as well as tert-butyl hydroperoxide, and hydrogen peroxide were used as radical initiators in water and buffer solutions at 37 °C. It is shown that the dyes are active scavengers of peroxyl radicals. It is found that reactivity and behavior of dyes in relation to the peroxides are strongly dependent on the structure of lateral substituents in polymethine chains.

The activity and selectivity of the Ni/SiO₂ catalyst, as well as the mono- and bimetallic Ni(Cu)—S/SiO₂ systems were investigated in the selective hydrogenation of 1,3-pentadiene to pentenes. The presulfiding of the catalysts in a hydrogen sulfide flow substantially increases the selectivity to olefins in gas mixtures with a range of H₂/diene molar ratio of 2.5–10. The samples activated in hydrogen at elevated temperatures turned out to be more active. The effect of modification of the nickel—sulfide catalysts with copper, resulting in an increase in the activity and selectivity to olefins, was found. The weight ratio Ni/Cu = 4 was shown to be optimum for achieving the maximum conversion and selectivity on the surface.

Monometallic and bimetallic copper-containing catalysts supported on silica gel KSKG were synthesized. The bimetallic Cu—Zn catalysts were most active and selective in the hydro-genation of p-dinitrobenzene (DNB) to p-phenylenediamine (PDA) (99% at 100% conversion of DNB). The highest activity and 99% selectivity to PDA at 100% DNB conversion were demonstrated by the monometallic catalysts with a Cu content of 9%. Unlike hydrogenation on the conventional catalysts, molecular H₂ is the hydrogenating agent in the presence of the copper-containing catalysts under relatively mild conditions (110–140 °C, 1.3 MPa).

A reaction of 3,5-di-tert-butyl-o-benzoquinone with 1,2- and 1,6-dithiols was used to obtain the corresponding bis-pyrocatechol thioethers; a comparative evaluation of their antioxidant activity was carried out. The synthesized thioethers, 2-(4,6-di-tert-butyl-2,3-dihydroxyphenylsulfanyl)acetic acid, and 3,5-di-tert-butylpyrocatechol were studied in the reaction with diphenylpicrylhydrazyl radical. The influence of these compounds on the autooxidation process of oleic (cis-octadec-9-enoic) acid was studied. The antioxidant activity of bis-pyrocatechol thioethers was manifested in the reaction with diphenylpicrylhydrazyl radical in the process of autooxidation of oleic acid, which was confirmed by the experimental EC₅₀ values, the data on the number of transformed molecules of stable radical (ⁿDPPH), and the relative content of oleic acid hydroperoxides. Bis-pyrocatechol thioethers were found to exhibit the inhibitory activity in the course of oxidation of glutathione induced by 2,2’-azobis(2-amidinopropane) dihydrochloride.

Synthetic procedures to access new potential NO donors that can generate NO in living systems, 3,3-bis(2-hydroxyethyl) and 3,3,3’-tris(2-hydroxyethyl) derivatives of 1,1’-[methylenebis(oxy)]bis(3,3-dialkyltriaz-1-ene 2-oxides), were elaborated. 3,3-Bis(2-acetoxyethyl)-1(chloromethoxy)triaz-1-ene 2-oxide reacts with 1-hydroxytriaz-1-ene 2-oxide sodium salts to give a series of alkylated 3,3-bis(2-acetoxyethyl) derivatives. Deacetylation of the latter produces 3-(2-hydroxyethyl)-11,11-dialkyl-6,8-dioxa-3,4,5,9,10,11-hexaazaundeca-4,9-dien-1-ol 4,10-dioxides and 11-alkyl-3-(2-hydroxyethyl)-6,8-dioxa-3,4,5,9,10,11-hexaazatrideca-4,9-diene-1,13-diol 4,10-dioxides.

The complexes (dpp-bian)Mg(thf)₃, (dpp-bian)Ca(thf)₄ and (dpp-bian)Mg(pyr)₃ (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion; pyr is the pyrrolidine) catalyze the addition of pyrrolidine to 2-vinylpyridine at room temperature. The compound (dppbian)Mg[N(SiMe₃)₂] containing a dpp-bian radical anion catalyzes the addition of pyrrolidine to styrene at 60 °C. The dpp-bian radical anion lithium-sodium salt [(dpp-bian)Li{N-(SiMe₃)₂}][Na(C₇H₈)] is an active catalyst of the addition of pyrrolidine to styrene and isoprene at 60 °C. In all the case, the content of the catalyst was from 1 to 2 mol.%. For styrene and 2-vinylpyridine, the reactions proceeded with the formation of anti-Markovnikov addition product, while 1,4-addition product was obtained in the case of isoprene.

A versatile one-pot synthesis of 4-substituted 3-(nitrooxyalkyl)furoxans by the reaction of 3-alkylfuroxans with a mixture of nitric and sulfuric acids was developed. A plausible mechanism of this unusual transformation was explained in terms of a new Grob-type fragmentation.

1,4-Bis(imidazol-1-yl)butane was synthesized from imidazole and 1,4-dibromobutane in an alkaline medium. A variation of the molar ratio of reagents in the system copper(II) chloride dihydrate and 1,4-bis(imidazol-1-yl)butane (bImB) upon heating in N,N-dimethylformamide resulted in the synthesis of two new coordination polymers [Cu(bImB)Cl₂] (1) and [Cu(bImB)₂Cl₂] (2), which were structurally characterized. Product 1 was found to possess a chain structure, while structure 2 is built of neutral layers, with the dimensionality of the extended coordination structures being determined by the reaction conditions. The new compounds were characterized by IR spectroscopy, elemental analysis, and powder X-ray diffraction data.

The nitration of sulfate lignin by nitric acid in an aqueous-dioxane medium under homogeneous conditions was studied. The method proposed makes it possible to synthesize nitrated lignin with the content of one nitro group per 1.5–2 phenylpropane units. At low consumptions of nitric acid, the nitration starts after an induction period, the duration of which decreases with increasing temperature. The presence of the induction period is related to redox transformations forming nitrous acid that nitrosates lignin.

Hydrogenation over Pd(OH)₂/C in a methanol—water—acetic acid mixture allows one to carry out the efficient simultaneous reduction of the azido group and remove the benzyl groups in 2-azidoethyl glycosides of benzylated chitooligosaccharides. The obtained 2-aminoethyl glycosides of free chitooligosaccharides were converted to the corresponding biotinylated conjugates serving as tools for glycobiological investigations.

Pentapeptide analogs of somatostatin containing an (R)-1,3-thiazolidine fragment (Thz) of the general formula X—Thz—Phe—D-Trp—Lys(Y)—Thr—Z were synthesized for the first time. The synthesized compounds were tested for cytotoxic activity against three cancer cell lines (MCF-7, PC3, and HCT-116) and against human embryo fibroblasts.

Esters of bile acids and avermectin B₁ were obtained for the first time by the reaction of avermectin B₁ with bile acid anhydrides.

The screening of the library containing 320 drugs and biologically active compounds was carried out. The library was created for testing potent agents on Rett syndrome models (SMART library) using new-generation luciferase reporters to identify stabilizers of transcription factors triggering genetic programs for defense against hypoxia and oxidative stress (HIF1 and Nrf2, respectively). Nine compounds proved to be activators of HIF1, and 18 compounds were shown to activate Nrf2. A histone deacetylase inhibitor (oxamflatin) and a carbonic anhydrase inhibitor (ethamide) were found to be the most powerful Nrf2 activators, which are equipotent or superior to sulforaphane and quercetin. Oxamflatin was also shown to activate HIF with potency comparable or superior to the commercial HIF activators developed by Fibrogen (USA) and GlaxoSmithKline (UK), but it was a significantly weaker activator than branched tail oxyquinolines, developed in our previous studies. The structural motif identified in oxamflatin can be used in the future design of branched oxyquinolines having higher activity and/or more specific against individual isoforms of HIF prolyl hydroxylase.

The nature of the chalcogen atom has a decisive effect on the direction of the nucleophilic substitution reaction between 2-pyridylchalcogenolate anions and propargyl halides. 2-Pyridylchalcogenolate anions react with sodium pyridyl tellurolate following 1,3-nucleophilic substitution mechanism to give selectively allenyl 2-pyridyl telluride. Under similar conditions, sodium 2-pyridyl selenolate and 2-pyridyl thiolate produce propargyl 2-pyridyl selenide and propargyl 2-pyridyl sulfide, respectively.