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排序方式: 共有163条查询结果,搜索用时 78 毫秒
71.
Dr. Tomáš Čarný Dr. Tibor Peňaška Samuel Andrejčák Prof. Dr. Radovan Šebesta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(58):e202202040
Cross-coupling reactions are essential tools in target molecule synthesis. However, the use of highly reactive organometallic reagents limits their applicability. Here, we present a mechanochemical Pd-catalyzed cross-coupling reaction between aryl halides and organozinc pivalates that can be carried out under ambient temperature and atmosphere. This operationally simple procedure affords a wide range of biaryl and aryl-heteroaryl derivatives in high yields and short times. The reaction tolerates various functional groups and can be realized on a synthetically useful scale. Its practical value was demonstrated in the short synthesis of the pharmaceutical diflunisal. 相似文献
72.
Cell‐based studies of the first‐in‐class half‐sandwich Ir(III) complex containing histone deacetylase inhibitor 4‐phenylbutyrate
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We report on a cytotoxic half‐sandwich iridium(III) complex [Ir(η5‐Cpph)(phen)(PB)]PF6 ( 1‐PB ), containing a monodentate coordinated O‐donor 4‐phenylbutyrato ligand (PB) belonging to the family of histone deacetylase inhibitors (HDACi); HCpph = (2,3,4,5‐tetramethylcyclopenta‐2,4‐dien‐1‐yl)benzene, phen = 1,?10‐phenanthroline. The solution behaviour studies indicated that complex 1‐PB partially hydrolysed in the mixture of methanol and water (1:4, v/v), resulting in the release of the PB ligand. The extent of the PB ligand release increased in the presence of 2 molar equiv. of the reduced glutathione (GSH). Complex 1‐PB exhibited comparable in vitro cytotoxicity against the cisplatin‐sensitive (IC50 = 15.8 μM) and ‐resistant (IC50 = 13.0 μM) variants of the A2780 human ovarian carcinoma cells, while its potency against the MRC‐5 human normal fibroblast cells was markedly lower (IC50 = 124.1 μM). The cytotoxicity studies revealed an ability of complex 1‐PB to overcome the acquired resistance against cisplatin, with the resistance factor (RF = 0.8) being markedly lower than for complex 1‐Cl (RF = 1.8) and cisplatin (RF = 2.9). The A2780 cell‐based flow cytometry experiments showed different cell cycle modification induced by complex 1‐PB and cisplatin, induction of production of reactive oxygen species, and higher mitochondria membrane potential depleted cell populations after the treatment by complex 1‐PB as compared with cisplatin. In the cell‐free assay, complex 1‐PB inhibited the HDAC activity to ca 66% as compared to ca 74% valid for NaPB. The [Ir(η5‐Cpph)(phen)(H2O)]2+ species ( 1‐OH 2 ), representing the hydrolysis product of both complexes 1‐PB and 1‐Cl , induced hydroxyl radical from the hydrogen peroxide, as proved by the EPR spin trapping studies with the 5‐(diethoxyphosphoryl)‐5‐methyl‐1‐pyrroline‐N‐oxide (DEPMPO) spin trap. 相似文献
73.
The addition of aliphatic aldehydes to β-nitrostyrene, catalyzed by proline-derived organocatalysts, proceeded well in various ionic liquids. Products were obtained in high yields and syn/anti diastereoselectivity. However, the enantioselectivity was only mediocre, even though some analogous reactions in organic solvents were highly enantioselective. We also evaluated the temperature effect on the diastereoselectivity as well as on the enantioselectivity of the Michael addition. 相似文献
74.
Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development. 相似文献
75.
Zdeněk Trávní?ek Radovan Herchel Radek Zbo?il 《Journal of solid state chemistry》2010,183(5):1046-9412
Three heterobimetallic cyanido-bridged copper(II) nitroprusside-based complexes of the compositions [Cu(tet)Fe(CN)5NO]·H2O (1), where tet=N,N′‐bis(3-aminopropyl)ethylenediamine, [Cu(hto)Fe(CN)5NO]·2H2O (2), where hto=1,3,6,9,11,14-hexaazatricyclo[12.2.1.16,9]octadecane and [Cu(nme)2Fe(CN)5NO]·H2O (3), where nme=N-methylethylenediamine, were synthesized and characterized by elemental analyses, 57Fe Mössbauer and FTIR spectroscopies, thermal analysis, magnetic measurements and single-crystal X-ray analysis. The products of thermal degradation processes of 2 and 3 were studied by XRD, 57Fe Mössbauer spectroscopy, SEM and EDS, and they were identified as mixtures of CuFe2O4 and CuO. 相似文献
76.
Simultaneous electrochemical determination of nitrate and nitrite in aqueous solution using Ag-doped zeolite-expanded graphite-epoxy electrode 总被引:2,自引:0,他引:2
In this work a new electrochemical sensor based on an Ag-doped zeolite-expanded graphite-epoxy composite electrode (AgZEGE) was evaluated as a novel alternative for the simultaneous quantitative determination of nitrate and nitrite in aqueous solutions. Cyclic voltammetry was used to characterize the electrochemical behavior of the electrode in the presence of individual or mixtures of nitrate and nitrite anions in 0.1 M Na2SO4 supporting electrolyte. Linear dependences of current versus nitrate and nitrite concentrations were obtained for the concentration ranges of 1-10 mM for nitrate and 0.1-1 mM for nitrite using cyclic voltammetry (CV), chronoamperometry (CA), and multiple-pulsed amperometry (MPA) procedures. The comparative assessment of the electrochemical behavior of the individual anions and mixtures of anions on this modified electrode allowed determining the working conditions for the simultaneous detection of the nitrite and nitrate anions. Applying MPA allowed enhancement of the sensitivity for direct and indirect nitrate detection and also for nitrite detection. The proposed sensor was applied in tap water samples spiked with known nitrate and nitrite concentrations and the results were in agreement with those obtained by a comparative spectrophotometric method. This work demonstrates that using multiple-pulse amperometry with the Ag-doped zeolite-expanded graphite-epoxy composite electrode provides a real opportunity for the simultaneous detection of nitrite and nitrate in aqueous solutions. 相似文献
77.
Petra Snevajsova Lukas Tison Iveta Brozkova Jarmila Vytrasova Radovan Metelka Karel Vytras 《Electrochemistry communications》2010,12(1):106-109
An electrochemical biosensor for specific detection of DNA sequences from Aspergillus, a potentially aflatoxigenic fungus is reported. The detection technique was optimized using short DNA sequences, then applied for a 92-mer from the Aspergillus gene aflR that codes a biochemical pathway of aflatoxin B1 production.Voltammetric detection of the specific Aspergillus DNA sequence is based on hybridization of adsorbed target DNA with a biotinylated probe and subsequent binding with streptavidin alkaline phosphatase conjugate. Such modified electrode surface of carbon paste electrode (CPE) is incubated in a buffer with an electrochemically inactive substrate (1-naphthyl phosphate). Alkaline phosphatase converts 1-naphthyl phosphate into 1-naphthol, which is determined by the selected voltammetric technique. The optimized procedure provided good differentiation between complementary and noncomplementary probes and also between potentially aflatoxigenic and non-aflatoxigenic fungi of the genus Aspergillus. 相似文献
78.
A Alimmari DA Mijin R Vuki Evi B Bo I NA Valenti V Vitnik E Vitnik G U Umli 《Chemistry Central journal》2012,6(1):71
ABSTRACT: BACKGROUND: A series of some novel arylazo pyridone dyes was synthesized from the corresponding diazonium salt and 6-hydroxy-4-phenyl-3-cyano-2-pyridone using classical reaction for the synthesis of the azo compounds. RESULTS: The structure of the dyes was confirmed by UV-vis, FT-IR, 1H NMR, 13C NMR spectroscopic technique and elemental analysis. The solvatochromic behaviour of the dyes was evaluated with respect to visible absorption properties in various solvents. CONCLUSIONS: The azo-hydrazone tautomeric equilibration is found to depend upon substituents as well as on solvents. The geometry data of the investigated dyes were obtained using DFT quantum-chemical calculations. The obtained calculational results are in very good agreement with the experimental data. 相似文献
79.
Fanrong Kong Junjie Ma Blair Carlson Radovan Kovacevic 《Optics & Laser Technology》2012,44(7):2186-2196
Two different cases regarding the zinc coating at the lap joint faying surface are selected for studying the influence of zinc vapor on the keyhole dynamics of the weld pool and the final welding quality. One case has the zinc coating fully removed at the faying surface; while the other case retains the zinc coating on the faying surface. It is found that removal of the zinc coating at the faying surface produces a significantly better weld quality as exemplified by a lack of spatters whereas intense spatters are present when the zinc coating is present at the faying surface. Spectroscopy is used to detect the optical spectra emitted from a laser generated plasma plume during the laser welding of galvanized high strength DP980 steel in a lap-joint configuration. A correlation between the electron temperature and defects within the weld bead is identified by using the Boltzmann plot method. The laser weld pool keyhole dynamic behavior affected by a high-pressure zinc vapor generated at the faying surface of galvanized steel lap-joint is monitored in real-time by a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source. 相似文献
80.
We argue that given the experimental constraints on the Higgs boson mass the least fine-tuned parameter space of the minimal supersymmetric standard model is with negative top-squark masses squared at the grand unification scale. While the top-squark mass squared is typically driven to positive values at the weak scale, the contribution to the Higgs boson mass squared parameter from the running can be arbitrarily small, which reduces the fine-tuning of electroweak symmetry breaking. At the same time the top-squark mixing is necessarily enhanced and the maximal mixing scenario for the Higgs boson mass can be generated radiatively even when starting with negligible mixing at the unification scale. This highly alleviates constraints on possible models for supersymmetry breaking in which fine-tuning is absent. 相似文献