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11.
Jean-Christophe Zwick Pierre Voge Vladimir Mange Gervals Chapuis 《Helvetica chimica acta》1987,70(5):1231-1249
A stereoselective synthesis of tricarbonyl-[((1RS,2RS,4RS,5RS,6RS)-C-5,6,C-η-(5,6,7,8,-tetramethylidenbicyclo[2.2.2]octan-2-ol)]iron ( 11 ),and of its tosylate 12 and benzoate 13 is reported. The bulk of the ‘endo’-Fe(CO))3 moiety and of the ester groups in 13 renders its Diels-Alder additions to methyl propynoate ( 15 )), butynone ( 16 ), and 1-cyanovinyl acetate highly ‘para’ regioselective. The cycloadditions of diene-alcohol 11 are either ‘meta’- or ‘para’-regioselective depending on the nature of the dienophile. In the presence of BF 3. Et 2O, the addition of 11 to methyl vinyl ketone is highly stereo- (Alder mode) and ‘para’-regioselective, giving adduct 52 (tricarbonyl [((1 RS,4RS,8RS,9RS,10RS,12RS)-C,9,10,C-η-(12-hydroxy-9,10-dimethylidenetricyclo[6.2.2.02,7]dodec-2(7)-en-4 yl methyl ketone)]iron) whose structure has been established by single-crystal X-ray crystallography. 相似文献
12.
Bonhommeau S Bréfuel N Pálfi VK Molnár G Zwick A Salmon L Tuchagues JP Sanchez Costa J Létard JF Paulsen H Bousseksou A 《Physical chemistry chemical physics : PCCP》2005,7(15):2909-2914
A quasi-quantitative photo-induced low-spin (LS)-->high-spin (HS) conversion of FeII ions has been observed in the [Fe(TRIM)2]Cl2 complex by irradiating the sample with blue light (488 nm) at 10 K. The time dependence of the HS-->LS relaxation has been studied between 10 K and 44 K by means of magnetic susceptibility measurements. These relaxation curves could be satisfactorily fitted by mono-exponential decays including tunnelling effect except for temperatures below 30 K. The introduction of a distribution of vibrational frequencies into this model improved significantly the fits in the low-temperature range and gave a good agreement with the experimental data in the whole temperature range suggesting a multi-rate relaxation process in this complex. 相似文献
13.
A. Malki J. P. Coffin G. Guillaume F. Jundt K. Krishan F. Rami P. Wagner P. Fintz M. Zahar M. Gonin B. Heusch M. Ohta B. Rastegar D. Rebreyend F. Merchez J. Mistretta S. Kox 《Zeitschrift für Physik A Hadrons and Nuclei》1991,339(2):283-292
In an attempt to separate preequilibrium and thermalised emissions of light particles in low impact parameter heavy-ion collisions, the40Ar+24Mg reaction has been studied at 27.5 MeV/nucleon. Exclusive measurements have permitted us to examine, in some detail, heavy fragments and charged particles (p, d, t,-particle). The fragments recognized as evaporation residues have been selected and, due to inverse kinematic conditions, the related preequilibrium and statistical emissions of light particles resulting from incomplete fusion reaction appear to be distinguishable to a fair extent. This separation is fully supported by Monte Carlo calculations. Some experimental characteristics of the light particles have been examined and compared to the predictions of dynamical calculations. These calculations, associating a preequilibrium (interpreted as prompt emitted particles) model with a statistical-decay model, follow the evolution of the collision from the point of contact between the projectile and the target to the final evaporation-residue formation on an event by event basis. The predictions of these calculations have been compared to experimental data and satisfactory agreement is achieved for fragment-mass distribution, proton-energy spectra, and proton-angular distribution. 相似文献
14.
Results of ir and Raman investigations on trigonal layer-structured Si2Te3 single crystals are reported. The ir reflection spectrum withEc exhibits seven reststrahl-like bands, whereas the corresponding spectrum withEc shows only one very small bump. Values for
0 and
are given. The Raman spectra are very rich in structure and can only be interpreted qualitatively as being a mixture of single phonon lines and one- and two-phonon density-of-states contributions. One-phonon density-of-states effects are disorder-induced owing to the statistical occurrence of the Si atoms within the regular hexagonal Te sublattice. 相似文献
15.
Venkata Rami Reddy Vaka Jaswanth Kumar Inamadugu Nageswara Rao Pilli Mullangi Ramesh Hussain Reddy Katreddi 《Biomedical chromatography : BMC》2013,27(11):1406-1412
An improved, simple and highly sensitive LC‐MS/MS method has been developed and validated for quantification of febuxostat with 100 μL human plasma using febuxostat‐d7 as an internal standard (IS) according to regulatory guidelines. The analyte and IS were extracted from human plasma via liquid–liquid extraction using diethyl ether. The chromatographic separation was achieved on a Zorbax C18 column using a mixture of acetonitrile and 5 mm ammonium formate (60:40, v/v) as the mobile phase at a flow rate of 0.5 mL/min. The total run time was 5.0 min and the elution of febuxostat and IS occurred at 1.0 and 1.5 min, respectively. A linear response function was established for the range of concentrations 1–6000 ng/mL (r > 0.99). The precursor to product ion transitions monitored for febuxostat and IS were m/z 317.1 → 261.1 and 324.2 → 262.1, respectively. The intra‐ and inter‐day precisions (%RSD) were within 1.29–9.19 and 2.85–7.69%, respectively. The proposed method was successfully applied to pharmacokinetic studies in humans. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
16.
This paper is dedicated to the numerical simulation of nuclear components (cores and steam generators) by fictitious domain methods. The fictitious domain approach consists in immersing the physical domain under study in a Cartesian domain, called the fictitious domain, and in performing the numerical resolution on this fictitious domain. The calculation times are then efficiently reduced by the use of fast solvers. In counterpart, one has to handle with an immersed boundary, generally non‐aligned with the Cartesian mesh, which can be non‐trivial. The two fictitious domain methods compared here on industrial simulations and developed by Ramière et al. deal with an approximate immersed interface directly derived from the uniform Cartesian mesh. All the usual immersed boundary conditions (Dirichlet, Robin, Neumann), possibly mixed, are handled through a unique formulation of the fictitious problem. This kind of approximation leads to first‐order methods in space that exhibit a good ratio of the precision of the approximate solution over the CPU time, which is very important for industrial simulations. After a brief recall of the fictitious domain method with spread interface (Ramière et al., CMAME 2007) and the fictitious domain method with immersed jumps (Ramière et al., JCP 2008), we will focus on the numerical results provided by these methods applied to the energy balance equation in a steam generator. The advantages and drawbacks of each method will be pointed out. Generally speaking, the two methods confirm their very good efficiency in terms of precision, convergence, and calculation time in an industrial context. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
17.
18.
Simultaneous grafting of 2-hydroxyethyl methacrylate and methyl methacrylate (3:1 and 3:2 mole ratios) onto insoluble collagen with ceric ammonium nitrate as initiator was attempted with a view to optimizing conditions for the preparation of hydrogels. The influence of monomer and initiator concentrations on the grafting reactions was investigated. The grafting results are discussed in the light of grafting efficiency and percentage of grafting. They were found to be lower when the 3:1 mole ratio of monomers was used. 相似文献
19.
M. S. R. Murty Rayudu Venkateswara Rao Kesur R. Ram N. Rami Reddy J. S. Yadav B. Sridhar 《合成通讯》2013,43(19):2914-2921
Zinc-mediated facile and efficient chemoselective S-alkylation of 5-aryl 1,3,4-oxadiazole-2-thiols in the presence of a catalytic amount of tetra butyl ammonium iodide was described. The reaction was performed under neutral conditions. The chemoselectivity of the alkylation was confirmed by NMR spectroscopy and x-ray crystallography. 相似文献
20.
Sandeep G. Yenchalwar Rami Reddy Devarapalli Ashvini B. Deshmukh Dr. Manjusha V. Shelke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7402-7409
The visible‐light response of Au nanoparticles (AuNPs) assembled on rGO through different molecular bridges was investigated by transient photocurrent generation. We prepared rGO with two self‐assembled monolayers (SAMs), one linear and the other with aromatic triazoles through a click cycloaddition reaction. A fivefold photocurrent enhancement was observed for triazole linkers over the aminopropyltrimethoxysilane (APTMS) linker. Cyclic voltammetry (CV) and impedance measurements also suggest fast electron transfer on account of the low resistance offered by the click‐modified rGO surface whereby introduction of triazoles offers the efficient bridge between the donor AuNPs and acceptor rGO. 相似文献