Doklady Chemistry最新文献

Effect of temperature on the efficiency of deuterium introduction into a new biologically active compound salicylcarnosine (SC) has been studied. Gaseous deuterium and heavy water were used as deuterium sources. The synthesis of labelled SC by a solid-phase method at 190°C leads to formation of [D]SC in 53% yield and deuterium content about 4.8 atoms per molecule. It has been shown that isotope exchange between SC protons and deuterium water proceeds more efficiently after preliminary treatment of catalyst with gaseous deuterium at ambient temperature. [D]SC forms in 46% yield and contains about 7.3 deuterium atoms per molecule. The preparative synthesis of labelled SC by this procedure at 190°C results in [D]SC yield of 60–70% at deuterium content about 6.2 atoms per molecule. The new procedure for the activation of deuterium inclusion in peptides opens additional opportunities for preparing highly labelled compounds.

Permeable nickel metallic and nickel oxide ceramic materials with nanostructured surface and multilevel hierarchical porosity were created by cyclic redox post-treatment of biporous nickel(II) consolidated in the sintering–dissolution process. Additional levels of intraparticle porosity—Kirkendall pores and shrinkage nanopores—were formed during the stages of high-temperature oxidation in air and reduction in hydrogen, respectively.

A promising strategy in the synthesis of functional compounds with a cage structure is the use of 1,3-dehydroadamantane (tetracyclo[3.3.1.1.^3,7.0.^1,3]decane; 1,3-DHA; bridging [3.3.1]propellane) and its derivatives that are capable of restoring the adamantane structure in their reactions. The review provides information on the methods for the synthesis of 1,3-DHA, spectral characteristics, probable intermediates generated from propellanes, and the advantages of their using: low-stage syntheses of difficult-to synthesize adamantane derivatives, atomic precision, and “green chemistry.” The reactions of 1,3-DHA with a wide range of organic compounds are considered, and its reactivity with respect to CH-, NH-, OH-, and SH-acids, as well as arenes, hydantoins, and heterocyclic compounds, is compared. New chemo- and regioselective methods for the one-step introduction of a 1-adamantyl group into the molecules of various substrates are classified. Particular attention is paid to the reactions of 1,3-DHA with various C–H acids, which enable the easy formation of C–C_Ad bonds to give hard-to-synthesize adamantane derivatives. The influence of pK_a of the substrate on the selectivity of the reactions is demonstrated. Low-step methods for the synthesis of new adamantane derivatives, which have shown high activity as hsEH epoxide hydrolase inhibitors and antitumor agents, are described.

Cesium-promoted cobalt spinel is promising as a catalyst for the low-temperature decomposition of nitrous oxide for use in the second stage of a single-reactor unit for the combined removal of nitrogen oxides. This work studied the effect of the conditions for the preparation of granular and block bulk catalysts based on Co₃O₄ by extrusion molding.

The parameters of the synthesis of catalysts by the solution combustion method using oxalic acid as a reducing agent were investigated. The activity of the catalysts was determined in the production of hydrogen and carbon nanofibers by the catalytic decomposition of methane. The efficiency of oxalic acid was demonstrated in the preparation of a nickel catalyst (90% Ni/10% Al₂O₃), which does not require the preliminary reduction with hydrogen. Regression analysis identified that the yields of carbon and hydrogen are most strongly affected by temperature among other synthesis parameters.

Glassy chalcogenides A^VB^VI obtained by solidification of high-temperature melts inherit the polymolecular nature of the melt. The influence of this circumstance on the optical properties of glasses is important for the fabrication of optical fibers and has not been adequately studied. Bulk samples of high-purity As_40 – xS_60 + x glasses (0 < x < 5) containing less than (1–2) × 10^–5 wt % metal and silicon impurities and not more than (0.5–1) × 10^–4 wt % carbon, oxygen, and hydrogen compounds were manufactured, and optical fibers were fabricated from these materials. The IR spectra of 12 cm-long bulk samples and optical fibers of up to 15 m length were recorded in the 1000–2000 cm^–1 spectral range. The spectra of the bulk samples and the optical fibers showed absorption bands with maxima at 1950, 1805, 1460, and 1320 cm^–1, due to the presence of super-stoichiometric amount of sulfur in the glass. The corresponding extinction coefficients were determined. The results of the study indicate that the stoichiometry of As₂S₃ can be considered as a factor significantly affecting the optical characteristics of glass.

The study is aimed at the development of a non-catalytic process for removal of nitrogen oxides from flue gases of thermal generating units. The results of experimental studies of a modified two-stage selective non-catalytic reduction of nitrogen oxides with injection of a reducing agent (urea) below the stoichiometric amount in each stage are described. The possibility of attaining a higher and more stable reducing efficiency compared with the conventional one-stage process and minimization of the formation of ammonia as a secondary pollutant is demonstrated.

New 1,5,3,7-diazadiphosphacyclooctanes with N,O-, N,N-, N,S-, and N,N,S-heterocyclic substituents at the nitrogen atoms have been synthesized. The influence of the nature of amines containing sp²-hybridized nitrogen atom in the ortho-position of the heterocyclic substituent on the result of Mannich condensation in phosphine–paraformaldehyde–primary amine system has been revealed. The stabilization of intermediate acyclic products—aminomethyl(hydroxymethyl)arylphosphines and bis(aminomethyl)arylphosphines—due to amino–imine tautomerism is responsible for the low yield of the target cyclic diphosphines based on the above amines.

Dipinodiazafluorenes are hybrid nopinane-annelated heterocycles whose molecules include a heterocyclic core of 4,5-diazafluorene fused with fragments of terpene hydrocarbon; they can selectively extract palladium (88−100%), gold (42−96%), and ruthenium (8−19%) by single extraction from acidic aqueous solutions (pH 1.2) containing complex mixtures of 3d elements and noble metals.