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61.
N‐Heterocyclic Carbene Catalysis via Azolium Dienolates: An Efficient Strategy for Remote Enantioselective Functionalizations 下载免费PDF全文
Dr. Xiang‐Yu Chen Qiang Liu Dr. Pankaj Chauhan Prof. Dr. Dieter Enders 《Angewandte Chemie (International ed. in English)》2018,57(15):3862-3873
N‐heterocyclic carbene (NHC) catalysis has emerged as a powerful strategy in organic synthesis. In recent years a number of reviews have been published on NHC‐catalyzed transformations involving Breslow intermediates, acyl azoliums, α,β‐unsaturated acyl azoliums, homoenolate equivalents, and azolium enolates. However, the azolium dienolate intermediates generated by NHCs have been employed in asymmetric synthesis only very recently, especially in cycloadditions dealing with remote functionalization. This Minireview highlights all the developments and the new advances in NHC‐catalyzed asymmetric cycloaddition reactions involving azolium dienolate intermediates. 相似文献
62.
Recognizing the potential of combinatorial chemistry to accelerate drug discovery and development, most pharmaceutical and related industries are seriously looking toward combinatorial synthesis of compounds in order to facilitate the identification of 'lead' molecules. In particular, solid phase synthesis is the core technology for combinatorial chemistry and is widely used for generating libraries of structurally related compounds. Since many drugs contain the nitrogen heterocyclic component and since heterocycles possess a high order of structural diversity, a precise overview of recent progress in the combinatorial synthesis of nitrogen heterocycles using solid phase methodology would be useful. Since the progress in solid phase synthesis of organic molecules has been reviewed regularly from 1992 to 1998, only the development of solid phase combinatorial synthetic approaches of small nitrogen heterocycles since 1999 will be reviewed here. This review describes the solid phase synthesis of azepanes, benzodiazepines, benzimidazoles, benzothiazepines, cinnolines, indolizines, beta lactams, oxazepins, oxazoles including benzisooxazoles, hydantoins, piperidines, pyrimidines, pyrazolones, quinolones, trizolopyridazines and thiazoles. 相似文献
63.
Murugesan Dinesh Subramanyam Deepika Rajendran HarishKumar Chinnadurai Immanuel Selvaraj Selvaraj Mohana Roopan 《Applied biochemistry and biotechnology》2018,185(2):450-463
The current study indicates that octyl-β-D-glucopyranoside (OGP) as a detergent which has the ability to make the lipid layer stiff. OGP was subjected for toxicity studies and in vitro cytotoxicty assays on cancerous HeLa and non-cancerous myoblasts H9c2 cell lines. Test against aquatic organisms were carried out in Artemia salina and LC50 values were calculated. Hemolytic activity tested for blood bio-compalibity showed hemolysis rate of 10–16%, followed by thrombolytic activity to burst the clots in blood. Also, the samples showed good lysis when compared to the standard streptokinase. Furthermore, α-amylase activity has been carried out to check the inhibition of α-amylase by the OGP. Finally, antibacterial activity has been tested against four different pathogens and their MIC values have been calculated. 相似文献
64.
Summary New dioxomolybdenum(VI) complexes MoO2L · H2O (LH2=Schiff base) derived from Salicylhydrazide and salicylaldehyde, 5-chloro-, 5-bromo-, 5-nitro-, 3-methoxy, 3-ethoxy-, 3,5-dichlorosalicylaldehyde and 2-hydroxy-1-naphthaldehyde have been synthesized and characterized, together with the MoO2L · THF adducts. The complexes are monomers, nonelectrolytes and diamagnetic, and contain acis O=Mo=O 相似文献
65.
Ram Manohar Yadav Dinesh Pratap Singh T. Shripathi O. N. Srivastava 《Journal of nanoparticle research》2008,10(8):1349-1354
We report the observations made on the synthesis and characterization of C–N nanotube blocks and Y-junctions in bamboo-like
C–N nanotubes. The C–N nanotube Blocks have been synthesized by pyrolyzing the mixture of silver nitrate acetonitrile solution
and ferrocene benzene solution. The structural/microstructural characterization of the as-synthesized material has been done
using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopic (XPS)
analysis has been carried out to confirm the presence of nitrogen in nanotubes. These investigations reveal the formation
of blocks of bamboo-like nanotubes having the dimension 300 × 200 × 30 μm and the diameter is 20–50 nm. We also observe the
formation of Y-junctions in bamboo-like nanotubes as we spray the acetonitrile ferrocene and AgNO3 mixture. The length of the synthesized Y-junction nanotube bundles is ~2 μm. Some more complex Ψ-shaped junctions are also
found to be present. The diameters of the Y-junction nanotubes is ~80 nm at the junction and 25–50 nm at the branches. 相似文献
66.
A simple and reproducible high-performance thin-layer chromatographic method was developed for the simultaneous determination of bergenin and gallic acid in Bergenia ligulata. Water and methanol were used as the extracting solvents. The concentrations of bergenin and gallic acid in both of these solvents were found to be almost the same. The method involves separation of the components by thin-layer chromatography on a precoated Silica Gel 60 F254 plate with a solvent system of ethyl acetate-formic acid-acetic acid-water (100 + 11 + 11 + 27). The sensitivity of the method for bergenin was 0.30 microg, whereas for gallic acid it was 0.25 microg. The proposed method is precise and sensitive and can be used for the detection, monitoring, and simultaneous quantification of bergenin and gallic acid in B. ligulata. 相似文献
67.
Deoshree Baghmar Neeraj K. Gaur Dinesh C. Gupta Sadhana Singh 《Central European Journal of Physics》2008,6(3):445-449
The structural changes within the Silver iodide (AgI) and Copper iodide (CuI) induced by pressure have been investigated using
an effective interaction potential. CuI and AgI in their parent zinc blende (ZnS) to rock salt (NaCl) through an intermediate
structure have been reported. The calculated values for the phase transition pressures and associate volume collapses are
generally in good agreement with measured data.
相似文献
68.
Jitender M.?KhuranaEmail author Sushma?Chauhan Geeti?Bansal 《Monatshefte für Chemie / Chemical Monthly》2004,135(1):83-87
Summary. A simple, rapid, and efficient method is reported for the hydrolysis of a variety of mono- and diesters of aromatic, aliphatic, fatty, and heterocyclic acids with potassium hydroxide in methanol at ambient temperature (35°C). 相似文献
69.
Sarma DD Topwal D Manju U Krishnakumar SR Bertolo M La Rosa S Cautero G Koo TY Sharma PA Cheong SW Fujimori A 《Physical review letters》2004,93(9):097202
We use a spatially resolved, direct spectroscopic probe for electronic structure with an additional sensitivity to chemical compositions to investigate high-quality single crystal samples of La(1/4)Pr(3/8)Ca(3/8)MnO3, establishing the formation of distinct insulating domains embedded in the metallic host at low temperatures. These domains are found to be at least an order of magnitude larger in size compared to previous estimates and exhibit memory effects on temperature cycling in the absence of any perceptible chemical inhomogeneity, suggesting long-range strains as the probable origin. 相似文献
70.
The observed frequency dependent optical response of hole doped cuprate La1.85Sr0.15CuO4 superconductors, has been theoretically analysed. Starting from an effective two-dimensional (2D) interaction potential for superlattice of hole doped cuprates treated as a layered electron gas, the spectral function is formulated. Calculations of the optical conductivity σ(ω) have been made within the two-component scheme: one is the coherent Drude carriers responsible for superconductivity and the other is incoherent motion of carriers from one site to other leads to a pairing between Drude carriers. The approach accounts for the anomalies reported (frequency dependence of optical conductivity) in the optical measurements for the normal state. Estimating the effective mass from specific heat measurement and ε∞ from band structure calculations for the low-energy charge density waves, the model has only one free parameter, the relaxation rate. The frequency dependent relaxation rates are expressed in terms of memory functions, and the coherent Drude carriers from the effective interaction potential lead to a sharp peak at zero frequency and a long tail at higher frequencies, i.e. in the infrared (IR) region. However, the hopping of carriers from one site to other (incoherent motion of doped carriers) yields a peak value in the optical conductivity centred at mid-IR (MIR) region. We find that both the Drude and hopping carriers in the superlattice of cuprates will contribute to the optical process of conduction in the CuO2 planes and shows similar results on optical conductivity in the MIR as well as IR frequency regions as those revealed from experiments. 相似文献