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121.
E. N. Popova A. L. Didenko V. M. Svetlichnyi V. E. Yudin E. A. Kaidash E. S. Vasil’eva O. V. Tolochko D. W. Li D. Kim 《Russian Journal of Applied Chemistry》2006,79(8):1321-1324
Film-forming polyimide nanocomposites containing 5 to 20 wt % nanoparticles were prepared from ferromagnetic Fe/Fe3O4 nanoparticles and a polyimide derived from 4,4′-bis(4-aminophenoxy)diphenyl sulfone and 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride. The mechanical properties and magnetization of the nanocomposite samples were studied in relation to the nanoparticle concentration. 相似文献
122.
An electrochemical strategy for running nitrogen-transfer reactions on chemically inert anode surfaces has been developed. The generation and trapping of highly reactive nitrene-transfer reagents can be accomplished under mild conditions on platinum electrodes. The key factor that accounts for the high levels of chemoselectivity in this process is the phenomenon of overpotential. We have found that molecules that are similar in terms of propensity toward oxidation can be differentiated on the basis of their affinity to a given electrode surface. Thereby, reactive species can be selectively generated in the presence of acceptor molecules of interest. Specifically, a wide range of structurally dissimilar olefins can be transformed into the corresponding aziridines in the presence of N-aminophthalimide. Likewise, nitrene generation in the presence of sulfoxides leads to their chemoselective transformation into the corresponding sulfoximines. In this paper we discuss the underlying mechanistic foundation of these reactions. 相似文献
123.
A comparative investigation into palladium-catalyzed allylic amination of unsubstituted aziridines and secondary amines has been carried out. The use of NH aziridines as nucleophiles favors formation of valuable branched products in the case of aliphatic allyl acetates. The regioselectivity of this reaction is opposite to that observed when other amines are used as nucleophiles. Our study provides evidence for the palladium-catalyzed isomerization of the branched (kinetic) product formed with common secondary amines into the thermodynamic (linear) product. In contrast, the branched allyl products obtained from unsubstituted aziridines do not undergo the isomerization process. Crossover experiments indicate that the isomerization of branched allylamines is bimolecular and is catalyzed by Pd(0). The reaction has significant solvent effect, giving the highest branched-to-linear ratios in THF. This finding can be explained by invoking the intermediacy of sigma-complexes, which is consistent with NMR data. The apparent stability of branched allyl aziridines towards palladium-catalyzed isomerization is attributed to a combination of factors that stem from a higher degree of s-character of the aziridine nitrogen compared to other amines. The reaction allows for regio- and enantioselective incorporation of aziridine rings into appropriately functionalized building blocks. The resulting methodology addresses an important issue of forming quaternary carbon centers next to nitrogen. The new insights into the mechanism of palladium-catalyzed allylic amination obtained in this study should facilitate synthesis of complex heterocycles, design of new ligands to control branched-to-linear ratio, as well as absolute stereochemistry of allylamines. 相似文献
124.
A. N. Kost L. G. Yudin V. A. Budylin N. G. Yaryshev 《Chemistry of Heterocyclic Compounds》1966,1(4):426-427
In bromination of indoles, the bromine atom will most probably enter at position 2 or 3. For example, indole and 2-methylindole [1] brominate at position 3, while some 3-substituted indoles [2] brominate at position 2. In the case of 2, 3-dimethylindole it was shown [3], that bromine does not enter the benzene ring, as would have been expected, but adds to the active 2, 3 (double) bond of the indole. 相似文献
125.
The kinetics and mechanism of 2,4-dihydro-1,2,4-triazol-3-one nitration in nitric acid have been studied. The role of 2-nitro-2,4-dihydro-1,2,4-triazol-3-one as an intermediate has been determined. 相似文献
126.
T. A. Kostereva Yu. N. Panov A. L. Didenko I. G. Silinskaya V. M. Svetlichnyi V. E. Yudin V. V. Kudryavtsev 《Russian Journal of Applied Chemistry》2004,77(8):1355-1358
The influence exerted by the molecular weight of partially crystalline polyimide derived from 4,4-bis(4-aminophenoxy)diphenyl and 1,3-bis(3,4-dicarboxyphenoxy)benzene on the viscosity of its melt was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 8, 2004, pp. 1370–1373.Original Russian Text Copyright © 2004 by Kostereva, Panov, Didenko, Silinskaya, Svetlichnyi, Yudin, Kudryavtsev. 相似文献
127.
Highly reactive [5,3] and [6,3] bicyclic aziridines can be readily prepared from the corresponding NH aziridines and N-bromosuccinimide by intramolecular oxidative cycloamination of olefins. These compounds, including surprisingly stable exo-methylene bicyclic aziridines, provide versatile synthetic entries into a wide range of pyrrolidine- and piperidine-containing heterocycles. 相似文献
128.
N. P. Yudin A. V. Pavlitchenkov V. G. Neudatchin 《Zeitschrift für Physik A Hadrons and Nuclei》1985,320(4):565-573
The cross sectionsd 3 σ/dE 1 d n 1 d n 2 for the Ar (γ, 2e) Ar++ process are calculated on the basis of the diagram approach within the energy intervalω=400–650 eV as functions of the angleθ 12 between final electrons with equal energiesE 1=E 2 for several levels of the final Ar++ ion. It has been elucidated that the interference of amplitudes corresponding to the interaction in the final and initial states is of prime importance. The angular distributions over the angleθ 12 are very sensitive to the term of the final ion. There are numerous data for the experimental verification of the theory, in particular, for the selection of leading diagrams. The (e, 3e) experiment is also desirable. 相似文献
129.
130.
I. P. Dobrovol’skaya N. S. Tsarev O. M. Osmolovskaya I. A. Kasatkin E. M. Ivan’kova E. N. Popova G. A. Pankova V. E. Yudin 《Russian Journal of Applied Chemistry》2018,91(3):368-374
X-ray diffraction analysis and transmission electron microscopy were used to demonstrate that hydroxyapatite produced by the precipitation method is a powder composed of anisometric particles with longitudinal size of 70–100 nm and transverse size of 7–9 nm. The particles are constituted by crystallites with longitudinal sizes of 22–24 nm and transverse sizes of 8–10 nm. At a temperature of 600°C, the crystallite sizes grow, and the volume porosity and specific surface area decrease. Synthetic hydroxyapatite has a low thermal stability as compared with hydroxyapatite of biological origin. 相似文献