Doklady Chemistry最新文献

An interaction of 6-aryl-1,2,4-triazine-5-carbonitriles with 2‑amino-4-aryl-substituted thiazoles and oxazoles has been studied. The difference in the reactivity of these aminoheterocycles depending on the presence of an oxygen or a sulfur atom in their composition has been demonstrated. Previously, the 4-aryl-3-hydroxy-2,2′-bipyridines were obtained as products of aza-Diels−Alder reaction between 6-aryl-3-(2-pyridyl)-1,2,4-triazine-5-carbonitriles and 2-amino-4-aryloxazoles. It was shown that the reaction of 6-aryl-1,2,4-triazine-5-carbonitriles with 2-aminothiazoles led to the products of ipso-substitution of cyano group. The aza-Diels−Alder reaction of these compounds with 2,5-norbornadiene gave (2,2′-bi)pyridines with the 2-aminothiazolyl at alpha-position.

The characteristics of lithium iron phosphate cathodes containing various types of commercially available carbon nanotubes—single-walled (SWCNTs), double-walled (DWCNTs), and multi-walled (MWCNTs)—have been compared. Electrochemical characteristics of the cathode materials have been studied by electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements. The cyclic stability at various current densities has been estimated. The best electrochemical characteristics are shown by the cathode materials containing SWCNTs (advantage over the DWCNT-based cathode materials at discharge rates higher than 10C) and DWCNTs (advantage over the SWCNT-based cathode materials during long-term cycling). During the long-term cycling at a current density of 1C, the greatest loss of capacity is observed for the MWCNT-based electrode. At the same time, the SWCNT- and DWCNT-based electrodes demonstrate satisfactory capacity retention after 50 charge/discharge cycles: over 94 and 98%, respectively.

Reaction of 5-hydrazinyl-substituted 1,2,4-triazines and 2,5-norbornadiene at elevated pressure and temperature (in autoclave) has been studied; the reaction yields 2-aminopyridines, 5-amino-1,2,4,-triazines, and 6-unsubstituted pyridines (formation of one of two latter products is dependent on the nature of substituent in the C3 position of triazine).

The study focuses on the development of a method of synthesis of a photosensitive mixture of controlled composition containing cationic water-soluble 5,10,15,20-tetrakis(N-Me-pyridin-3-yl)chlorin and 5,10,15,20-tetrakis(N-Me-pyridin-3-yl)bacteriochlorin. The diimide reduction of 5,10,15,20-tetrakis(pyridin-3-yl)porphine in pyridine and in the absence of a solvent has been studied. It has been shown that the reduction in the melt significantly decreases the reaction duration (from 12 to 1.5 h) and affords compositions in up to 90% yield.

A water-soluble monocationic chlorin photosensitizer for antimicrobial photodynamic therapy of superficial localized infections has been proposed. The antimicrobial activity of this compound against planktonic forms of nosocomial antibiotic-resistant gram-negative pathogens, Pseudomonas aeruginosa, Enterobacter cloacae, and Acinetobacter baumannii, has been studied in comparison with the activity of the photosensitizer Fotoran e₆, widely used in the clinical photodynamic therapy of tumors. It has been shown that both photosensitizers possess low dark toxicity; however, the light toxicity of the monocationic chlorin is higher by several orders of magnitude, and it can be proposed as a new agent for the antimicrobial photodynamic therapy.

The crystalline phase of Mg₃BPO₇ was obtained by gel combustion method and solid-phase synthesis with optimization of annealing temperatures. The effect of precursors and synthesis conditions on the formation of Mg₃BPO₇ was analyzed by X-ray powder diffraction and IR spectroscopy. It was shown that the formation of a mixture of kotoite Mg₃B₂O₆ and farringtonite Mg₃P₂O₈ prevents the formation of Mg₃BPO₇, whereas a significant excess of periclase MgO promotes the production of Mg₃BPO₇.

An active and selective catalyst 1%Pt/CeO₂–ZrO₂ for glycerol hydrodeoxygenation to 1,2-propanediol was synthesized. The reaction was carried out in water under relatively mild conditions: a temperature of 170°C and a hydrogen pressure of 10 atm for 6 h. The glycerol conversion reached 82% with a 74% selectivity to 1,2-propanediol. The high activity and selectivity of the catalyst are due to the high degree of dispersion of supported platinum nanoparticles with a size of less than 2 nm, the optimal Ce : Zr ratio in a mixed oxide support, high specific surface area, and the presence of weak Brønsted acid sites. The presence of zirconium in the mixed oxide support not only gives rise to additional defects in the cerium oxide structure, but also stabilizes the deposited platinum nanoparticles.

A stable diradical 2-{N-[(3s,5s,7s)-adamantyl-1]-N-oxylamino}-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl—a heteroatomic analogue of trimethylenemethane—has been synthesized by reacting lithiated 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl with 1-nitroso-adamantane, followed by oxidation of the intermediate hydroxylamine. According to X-ray diffraction data, the dihedral angle between the planes of paramagnetic moieties in the paramagnet is close to 60°. Magnetochemical measurements have shown that the energy gap between the triplet and singlet states (2J/k_B; H = –2JS_1/2S_1/2) in the diradical is 880 K. The EPR spectrum of the diradical was simulated using the parameters: S = 1, g_xx = 2.007, g_yy = 2.005, g_zz = 2.006, D = 825 MHz, E = 60 MHz. According to the data of cyclic voltammetry in the anodic region, the diradical undergoes electrochemical oxidation at potentials of 0.79, 1.63, 1.89, and 2.25 V, the first process being chemically and electrochemically reversible. In the cathodic region, the diradical is reduced quasi-reversibly at –1.18 and irreversibly at –2.59 V.

Phosphorus-containing compounds have a huge synthetic potential because of their wide application in pharmaceuticals, biology, agrochemistry, organic synthesis, and materials science. The search for new selective reactions for their preparation requires a deeper understanding of the properties and reactivity of key intermediates, which include phosphorus-centered radicals. Of particular interest are the ways to stabilize such radicals, which have unusual physical properties. This review analyzes and summarizes basic achievements and trends in both the generation of highly reactive phosphorus radicals and their involvement in practically significant synthesis reactions, primarily the formation of phosphorus–carbon bonds, and the pathways for the synthesis of stable radicals, their physicochemical properties, and magnetic resonance parameters. Despite the long historical development of research, important achievements in this area have been made over the past decade.

Acridine has been found to undergo readily concurrent N(1)- and С(9)-functionalization under the action of ethyl aryl-2-oxobut-3-ynoates and water to form pharmacologically promising previously unknown N-alkenylacridones in 80–84% yields.