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161.
Denis N. Tomilin Maxim D. Gotsko Lyubov N. Sobenina Igor A. Ushakov Boris A. Trofimov 《Tetrahedron letters》2019,60(28):1864-1867
The cycloadducts of menthofuran with acylbromoacetylenes, (3-bromo-1,6-dimethyl-5,6,7,8-tetrahydro-2H-2,4a-epoxynaphthalen-4-yl)(aryl)methanones, rearrange (CHCl3, reflux, 1 h) to 2-(2-acylethyl)benzofurans (along with the expected 2-bromo-3-hydroxy-4,7-dimethyl-5,6,7,8-tetrahydronaphthalene-1-yl)(aryl)methanones) via 2-acylethynylmenthofurans, thus indicating the exceptionally mild and rapid transfer of four hydrogens from a cyclohexane ring to a triple bond through the furan moiety in the key intermediate 2-acylethynylmenthofuran. 相似文献
162.
V Snitka DO Naumenko L Ramanauskaite SA Kravchenko BA Snopok 《Journal of colloid and interface science》2012,386(1):99-106
The green synthesis of irregular-shaped nanomaterials used for various applications in nanoplasmonics, medicine, and biotechnology creates an economical and environmental challenge. We describe the rapid wet-chemical approach to synthesis of stable and water-soluble gold nanostructues at room temperature. In addition to spherical and road-like nanoparticles, gold decahedra and triangular plates were grown using the one-step synthesis process of HAuCl(4) in the presence of honey, in which main components act as reducing (glucose) and stabilizing (fructose) agents; the mechanism of the process is discussed in details. The requirements for anisotropic phase boundaries for generation of polyhedral gold nanocrystals in solutions are highlighted. The synthesis, morphology, and separation procedure of gold nanoparticles are examined using the techniques of optical spectroscopy, transmission electron microscopy, and atomic force microscopy. We demonstrate that centrifugation can be used for efficient separation of nanoparticles with different shapes from a mixture. It was found that while centrifuging, the spheres sediment at the bottom of the tube, segregating from rods that form a deposit on the side wall, whereas polygons remain in the solution. 相似文献
163.
Gas hydrates are crystalline structures comprising a guest molecule surrounded by a water cage, and are particularly relevant
due to their natural occurrence in the deep sea and in permafrost areas. Low molecular weight molecules such as methane and
carbon dioxide can be sequestered into that cage at suitable temperatures and pressures, facilitating the transition to the
solid phase. While the composition and structure of gas hydrates appear to be well understood, their formation and dissociation
mechanisms, along with the dynamics and kinetics associated with those processes, remain ambiguous. In order to take advantage
of gas hydrates as an energy resource (e.g., methane hydrate), as a sequestration matrix in (for example) CO2 storage, or for chemical energy conservation/storage, a more detailed molecular level understanding of their formation and
dissociation processes, as well as the chemical, physical, and biological parameters that affect these processes, is required.
Spectroscopic techniques appear to be most suitable for analyzing the structures of gas hydrates (sometimes in situ), thus
providing access to such information across the electromagnetic spectrum. A variety of spectroscopic methods are currently
used in gas hydrate research to determine the composition, structure, cage occupancy, guest molecule position, and binding/formation/dissociation
mechanisms of the hydrate. To date, the most commonly applied techniques are Raman spectroscopy and solid-state nuclear magnetic
resonance (NMR) spectroscopy. Diffraction methods such as neutron and X-ray diffraction are used to determine gas hydrate
structures, and to study lattice expansions. Furthermore, UV-vis spectroscopic techniques and scanning electron microscopy
(SEM) have assisted in structural studies of gas hydrates. Most recently, waveguide-coupled mid-infrared spectroscopy in the
3–20 μm spectral range has demonstrated its value for in situ studies on the formation and dissociation of gas hydrates. This
comprehensive review summarizes the importance of spectroscopic analytical techniques to our understanding of the structure
and dynamics of gas hydrate systems, and highlights selected examples that illustrate the utility of these individual methods. 相似文献
164.
Nina Gusarova Lambert Brandsma Svetlana Malysheva Svetlana Arbuzova Boris Trofimov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Nucleophilic addition of phosphide anions generated from phosphorus red or phosphine to ethenes and ethynes in the presence of super bases to afford organylphosphines and -oxides has been performed. 相似文献
165.
Vladimir A. Potapov Svetlana V. Amosova Boris V. Petrov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):587-590
Reactions of dicyanodiselenide, selenenyl chlorides and bromides with acetylenes and some further transformations of obtained products have been studied. 相似文献
166.
167.
Boris A. Kashemirov Mari Fujimoto-posner Charles E. McKenna 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract The (E-oxime of phosphonoglyoxylic acid, or (E-troika acid [(E)-l] undergoe: fragmentation leading to phosphorylation of the aqueous solvent at neutral pH and room temperature.[1] In contrast, the corresponding C-methyl ester (a-2 is stable under these mild conditions. Conversion of the unreactive (E)-2 to (E)-1 requires dewthylation a pH 13–14, generating the polyanion of (E-1, which becomes reactive on protonation.[1] 相似文献
168.
Boris I. Usachev Vyacheslav Ya. Sosnovskikh Mikhail A. Shafeev Gerd-Volker Röschenthaler 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1315-1319
Abstract Alkyl 2-mercaptophenyl ketones react with trifluoroacetic anhydride in the presence of triethylamine to give 2-(trifluoromethyl)-4H-thiochromen-4-ones, which are transformed into the corresponding pyrazoles by treatment with hydrazine hydrate and into 1,1-dioxides by oxidation with H2O2 in AcOH. 相似文献
169.
170.
Christelle Titier Jean-Pierre Pascault Mohamed Taha Boris Rozenberg 《Journal of polymer science. Part A, Polymer chemistry》1995,33(1):175-184
Epoxy-amine methacrylated prepolymers are prepared in a 1-step synthesis by the reaction of Bisphenol A diglycidyl ether, glycidyl methacrylate, and different diamines. The adaptation of these reactions to production processes with a reduced reaction time requires a kinetic control and the use of efficient catalysts. The comparative kinetic treatment of the epoxy-amine reaction in the frame of Horie's and Rozenberg's kinetic schemes have been made. Cases where an efficient acid catalyst is used are also examined. Structural studies of these reactions established the occurrence of a Michael amine/double bond addition, when some amines are used. © 1995 John Wiley & Sons, Inc. 相似文献