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21.
Grigorieva N. Ya. Popovsky V. A. Stepanov A. V. Kolotyrkina N. G. 《Russian Chemical Bulletin》2010,59(4):848-851
(2E,4E)-5-Aryl-2-(2-benzyloxyethyl)penta-2,4-dien-1-als (aryl is phenyl and 4-methox-yphenyl) were reduced with NaBH4 quantitatively and stereospecifically to the corresponding penta-2(E),4(E)-dien-1-ols. The hydroxymethyl group in the latter was transformed into a methyl one with a stereoselectivity of 92–97%.
Debenzylation of the resulting (1E,3Z)-1-aryl-6-benzyloxy-4-methylhexa-1,3-dienes with AlCl3 in the presence of PhNMe2 afforded the target (3Z,5E)-6-aryl-3-methylhexa-3,5-dien-1-ols; the configuration of the C=C bonds in the conjugated aryl diene systems was retained
at 95%. 相似文献
22.
N. Ya. Grigorieva V. A. Popovsky A. V. Stepanov E. D. Lubuzh 《Russian Chemical Bulletin》2010,59(11):2086-2093
Known synthetic precursors of strobilurins A and X, i.e., methyl (3Z,5E)-6-aryl-3-methylhexa-3,5-dienoates (aryl is phenyl, 4-methoxyphenyl), were synthesized by highly stereospecific reactions
from 2-(2-tert-butyldimethylsilyloxyethyl)- and 2-[2-(4-methoxybenzyloxy)-ethyl]-5-arylpenta-2E,4E-dien-1-ols. These dienols were efficiently dehydroxylated to (1E,3Z)-4-methyl-6-(4-methoxybenzyloxy)hexa-1,3-dienylarenes with their subsequent demethoxyben-zylation to (3Z,5E)-6-aryl-3-methylhexa-3,5-dien-1-ols. The latter through the step of corresponding aryldienals and aryldienoic acids were
transformed to the target methyl (3Z,5E)-6-aryl-3-methylhexa-3,5-dienoates, which completes a formal synthesis of strobilurins A and X. Configuration of the C=C
bonds of the conjugated aryldiene system is preserved in the considered transformations by 95–97%. 相似文献
23.
Experiments on long-range propagation of low-frequency sound that were conducted starting from the mid-1980s indicate a complex
character of propagation in an underwater sound channel, in which a source and a receiver are located close to the channel
axis. A burst of energy propagating along the axis follows early arrivals, which are well described by the formulas of geometrical
acoustics, in plots of acoustic intensity as a function of propagation time and hydrophone depth. This energy burst cannot
be described using geometrical acoustics because of caustics with caustic beaks located near the channel axis. Very complex
interference processes occur near these caustics. As the distance from the source grows, the dimensions of the interference
vicinity increase and start to overlap producing a peculiar “axial wave.” For an arbitrary two-dimensional underwater sound
channel, the axial wave can be represented as a sum of the first normal modes and a residue. This conclusion is based on the
use of two representations for an acoustic field. The first of them includes the sum of ray components and an axial wave.
The second representation consists of ray addends, the sum of the first normal modes, and a residue. Numerical results are
obtained for a canonical profile of sound velocity at the frequency of 200 Hz for the distances of 1600–1650 km. 相似文献
24.
A remarkable effect of circular dichroism, i.e., a difference in photoelectron spectra produced by right and left circularly polarized light in two-color multiphoton ionization of atoms, is predicted for the case when the atom is ionized by an extreme ultraviolet or x-ray femtosecond pulse in the field of a strong infrared laser pulse, both pulses being circularly polarized. We show that the sidebands formed in the spectra exhibit different circular dichroism often of different signs both in angle-resolved and angle-integrated experimental conditions. The effect can be used for detecting and measuring circular polarization of x rays in a spectral range where other methods are not effective. 相似文献
25.
Reversible Modulation of Surface Plasmons in Gold Nanoparticles Enabled by Surface Redox Chemistry 下载免费PDF全文
Dr. Zheng Li Dr. Jonathan J. Foley IV Dr. Sheng Peng Dr. Cheng‐Jun Sun Dr. Yang Ren Dr. Gary P. Wiederrecht Dr. Stephen K. Gray Dr. Yugang Sun 《Angewandte Chemie (International ed. in English)》2015,54(31):8948-8951
Switchable surface redox chemistry is demonstrated in gold@iron/iron oxide core–shell nanoparticles with ambient oxidation and plasmon‐mediated reduction to modulate the oxidation state of shell layers. The iron shell can be oxidized to iron oxide through ambient oxidation, leading to an enhancement and red‐shift of the gold surface plasmon resonance (SPR). This enhanced gold SPR can drive reduction of the iron oxide shell under broadband illumination to reversibly blue‐shift and significantly dampen gold SPR absorption. The observed phenomena provide a unique mechanism for controlling the plasmonic properties and surface chemistry of small metal nanoparticles. 相似文献
26.
N. A. Palchik T. N. Moroz T. N. Grigorieva L. V. Miroshnichenko 《Russian Journal of Inorganic Chemistry》2014,59(5):511-518
The mineral, chemical, and trace element composition and the microstructures of manganese minerals in bottom nodules and crusts collected from the Bolshoe Miassovo freshwater lake (South Urals) were studied. Freshwater manganese species were shown to have more diversified mineral compositions than in marine species. In addition to (9.6- and 7.2 Å) layered manganese mineral structures, various manganese-containing carbonates were frequently present in lacustrine samples. As opposed to marine samples, lacustrine samples were poor in trace elements, in particular rare-earth elements, but have higher contents of Sr, As, Ti, and V. A structural analysis of lacustrine manganese species showed their biomorphic nature, which manifested itself as organic bacterial species ranging from spherulitic to filamentary ones. 相似文献
27.
28.
29.
Doklady Mathematics - The local dynamics of a well-known model of an optoelectronic oscillator with delayed feedback is studied. In a neighborhood of zero equilibrium, normalized equations are... 相似文献
30.
Leonid N. Bochkarev Vladislav I. Scherbakov Irina P. Malysheva Galina V. Basova Natalia E. Stolyarova Irina K. Grigorieva Andrey L. Bochkarev Georgii K. Fukin Yurii A. Kurskii Gleb A. Abakumov 《Journal of organometallic chemistry》2006,691(5):983-986
The novel silicon-, germanium- and tin-containing imido alkyl complexes of tungsten of the type (ArN)2W(CH2EMe3)2 (; E = Si (1), Ge (2), Sn (3)) have been prepared by the reactions of (ArN)2WCl2(dme) (dme = 1,2-dimethoxyethane) with heteroelement-containing alkyllithium or Grignard reagents Me3ECH2Li (E = Si, Ge), Me3ECH2MgCl (E = Ge, Sn). The title compounds were isolated in high yields as crystalline solids and characterized by elemental analysis, IR, 1H, 13C, 29Si and 119Sn NMR spectroscopy and X-ray diffraction studies. The geometry of the W atoms in the compounds can be described as a distorted tetrahedron. 相似文献