An efficient approach based on pyrone ring opening in 3-arylisocoumarins in the presence of cyclic secondary amines was developed in order to prepare amides of deoxybenzoin-2'-carboxylic acids, ...diverse functionalized structures useful for the synthesis of polyfunctional compounds.
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•Efficient approach to enaminoketones of 2′-carboxamidodeoxybenzoins in good yields.•Efficient approach to otherwise not readily obtainable 3-aryl-4-formylisocoumarins.•Readily ...available reagents, simple procedures, and short reaction times.•N,N-Dimethylformamide dimethyl acetal serves both as a carbon source and solvent.
The efficient synthesis of enaminoketones of 2′-carboxamidodeoxybenzoins and subsequent transformation into 1-oxo-3-aryl-1H-isochromene-4-carbaldehydes via an intermolecular cyclization under weakly acidic conditions has been demonstrated. Mild reaction conditions, a simple work-up procedure, short reaction times and high yields are the advantages of the presented method.
The effect of exogenous melatonin (MT) on the expression of LYVE-1 receptor (lymphatic vessel endothelial hyaluronan receptor 1) in endothelial cells (ECs) of liver sinusoids of female db/db mice ...with obesity and type 2 diabetes mellitus was studied. LYVE-1 immunohistochemical staining was performed using the indirect avidin-biotin peroxidase method. A morphometric analysis of the relative area and brightness (this parameter is inversely proportional to the marker concentration) of the receptor staining was carried out. Control and placebo db/db mice at 16 weeks of age, revealed insignificant LYVE-1 staining of the network of blood sinusoid capillaries in the periportal regions and especially in the intermediate zones of the hepatic lobules. Long-term MT administration to animals (intragastrically at a dose of 1 mg / kg of body weight in 200\ \mu\mathrm{l} of distilled water from the 8th to the 16th week of life) contributed to an increase in the relative area of LYVE-1 expression in the liver sinusoidal cells. At the same time, the antioxidant properties of MT can play an important protective role. This hormone exerts antioxidant effects not only directly on the extracellular matrix, but also indirectly, maintaining the membrane organization and intracellular structures in the EC of sinusoids. As a result, MT can reduce the hypoxic state of ECs in liver sinusoidal capillaries and, as a consequence, reduce the degradation of high-molecular-weight hyaluronan and promote an increase in the expression area of the "free", i.e. non-HA-bound LYVE receptor. This, in turn, may indicate the strengthening of the endothelial barrier of the organ.
The paper presents a comparative study of the activity of magnetite (Fe3O4) and copper and cobalt ferrites with the structure of a cubic spinel synthesized by combustion of glycine-nitrate precursors ...in the reactions of ammonia borane (NH3BH3) hydrolysis and hydrothermolysis. It was shown that the use of copper ferrite in the studied reactions of NH3BH3 dehydrogenation has the advantages of a high catalytic activity and the absence of an induction period in the H2 generation curve due to the activating action of copper on the reduction of iron. Two methods have been proposed to improve catalytic activity of Fe3O4-based systems: (1) replacement of a portion of Fe2+ cations in the spinel by active cations including Cu2+ and (2) preparation of highly dispersed multiphase oxide systems, involving oxide of copper.
The effect of different regimes of combustion of glycine–nitrate precursors on the formation of perovskite phases (LaMnO3 and LaCrO3) without additional heat treatment was studied. The following ...three combustion regimes were compared: the traditional solution combustion synthesis (SCS), volume combustion synthesis (VCS) using a powdered precursor, and self-propagating high-temperature synthesis (SHS) using a precursor pellet. The products of combustion were studied using a series of physicochemical methods (attenuated total reflection infrared spectroscopy (ATR FTIR), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and thermal analysis). SHS was found to be the most productive regime for the formation of perovskite because of its ability to develop high temperatures in the reaction zone, which led to a reduced content of the thermally stable lanthanum carbonate impurities and to an increased yield and crystallite size of the perovskite phase. The reasons for the better crystallinity and purity of LaCrO3 as compared with LaMnO3 is also discussed, namely the low temperatures of the onset of the thermolysis, the fast rate of combustion, and the favorable thermodynamics for the achievement of high temperatures in the reaction zone.
The results obtained in this study show that Sb-containing catalysts MoVSbNbGdOx/SiO2 are highly active in ethane oxidative dehydrogenation to produce ethylene. The ethylene yield of 72% (79.3% ...ethylene selectivity and 91.1% ethane conversion) was obtained at 400 °C on one of the best catalyst. The effect of Gd additives on the catalytic properties of MoVSbNbGdOx/SiO2 catalysts was investigated. The catalysts with Gd/Mo = 0.010 – 0.015 demonstrated relatively high catalytic activity coupled with high selectivity to ethylene and excellent stability in ODE reaction, but further growth of the gadolinium content (Gd/Mo = 0.02) was accompanied by the decrease in the activity and ethylene selectivity. XRD, HRTEM, SEM, XPS and adsorption methods were used to reveal the phase composition, morphology and the structure of the obtained catalysts.
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•The catalysts MoVSbNbGdOx/SiO2 with different gadolinium content were synthesized.•The effect of Gd on the catalytic and physicochemical properties were investigated.•The ethylene yield of 72% was obtained at 4000 C on one of the best catalyst.•The active mass of catalyst contains two main phases, M1 (80%) and M2 (20%).•Phase M1is stabilized as needle-like morphology particles inside the SiO2 particles.
In our study, we have obtained a multicomponent MoVSbNbCeOx/SiO2 catalyst with high catalytic activity for oxidative dehydrogenation of ethane (ODE) to ethylene. To date, multicomponent MoVTe(Sb)NbOx ...catalysts, which have been intensively studied during the last years, were found as very promising for the ODE to produce ethylene. It was generally agreed that the MoVTeNbOx catalyst was more efficient than MoVSbNbOx. The major drawback of using Te‐containing catalysts is the presence of environmentally harmful, toxic tellurium, and its volatility during the catalyst preparation and catalytic reaction conditions. In our work, the Mo1V0.24Sb0.23Nb0.08Ce0.01Ox/50 wt. % SiO2 catalyst was prepared via the spray‐dry method of aqueous solutions of the starting components, followed by heat‐treatment in He at 350 and 600 °C. For comparative purpose, one of the best Te‐containing catalysts Mo1V0.3Te0.23Nb0.12Ox was also tested in this reaction under the similar reaction conditions. A comparison of the catalytic properties of Sb− and Te− containing catalysts at the reaction temperature of 400–450 °C illustrates for both catalysts relatively high catalytic properties for ODE. The yield of ethylene of ca. 74 % was obtained for these catalysts, which exceeds the best yield reported in literature for Sb‐containing catalysts. The two main phases – M1 and M2 were revealed by XRD in the Sb‐containing catalyst. Intergrowth between the crystals of M1 and M2 phases with the formation of the interphase boundary in the highly active and selective Sb‐containing catalyst can be proposed from HRTEM results. The nature of the active state in this catalyst is discussed.
From ane to ene: For MoVSbNbCeOx/SiO2 catalyst the yield of ethylene in the ODE 74 % was obtained which exceeds the best yield reported in literature for Sb‐containing catalysts. Intergrowth between the crystals of M1 and M2 phases with the formation of the interphase boundary in the highly active and selective Sb‐containing catalyst can be proposed from HRTEM analysis.
Catalytic hydrolysis of NaBH
4 and NH
3BH
3 has been studied. It was shown that the nature of the support and the active component of the catalyst affect the H
2 generation rate. Despite similar ...sizes of rhodium particles formed on the surface of different supports (γ-Al
2O
3, TiO
2, carbon), their reactivity is different. Rh/TiO
2 with low rhodium concentration (1
wt.%) is the most active catalyst both in the hydrolysis of NaBH
4 and NH
3BH
3. The obtained results show that the rhodium chloride interaction with titania determines the reactivity of rhodium particles formed under action of NaBH
4 medium. TEM, DRS UV–vis and XPS were used to characterize the catalysts.
Abstract
In our study, we have obtained a multicomponent MoVSbNbCeO
x
/SiO
2
catalyst with high catalytic activity for oxidative dehydrogenation of ethane (ODE) to ethylene. To date, multicomponent ...MoVTe(Sb)NbO
x
catalysts, which have been intensively studied during the last years, were found as very promising for the ODE to produce ethylene. It was generally agreed that the MoVTeNbO
x
catalyst was more efficient than MoVSbNbO
x
. The major drawback of using Te‐containing catalysts is the presence of environmentally harmful, toxic tellurium, and its volatility during the catalyst preparation and catalytic reaction conditions. In our work, the Mo
1
V
0.24
Sb
0.23
Nb
0.08
Ce
0.01
O
x
/50 wt. % SiO
2
catalyst was prepared via the spray‐dry method of aqueous solutions of the starting components, followed by heat‐treatment in He at 350 and 600 °C. For comparative purpose, one of the best Te‐containing catalysts Mo
1
V
0.3
Te
0.23
Nb
0.12
O
x
was also tested in this reaction under the similar reaction conditions. A comparison of the catalytic properties of Sb− and Te− containing catalysts at the reaction temperature of 400–450 °C illustrates for both catalysts relatively high catalytic properties for ODE. The yield of ethylene of ca. 74 % was obtained for these catalysts, which exceeds the best yield reported in literature for Sb‐containing catalysts. The two main phases – M1 and M2 were revealed by XRD in the Sb‐containing catalyst. Intergrowth between the crystals of M1 and M2 phases with the formation of the interphase boundary in the highly active and selective Sb‐containing catalyst can be proposed from HRTEM results. The nature of the active state in this catalyst is discussed.
The association of the cationic dye indoheptamethine cyanine with various anionic dyes (four sulfonephthaleins and five xanthenes) in aqueous solutions was detected using the Vis-spectroscopic ...method. The values of the association constants are within the range (10(4) to 7×10(7) mol-1 L). In all the cases a substantial hypochromic effect is observed for the Vis absorption band of the cation (lambdamax = 737 nm). The interaction of indotrimethinium cation (lambdamax = 540 nm) with anionic species manifests itself in analogous manner. Electrostatic, Van der Waals, and hydrophobic interactions are regarded as driving forces of the association. Addition of ionic surfactants destroys the dye associates, primarily due to interactions with the oppositely charged dye ions. This process is accompanied by the restoration of the initial Vis absorption bands of both the cationic and the anionic dye.
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