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41.
A series of acylated α-aminophosphine oxides were synthesized by the microwave-assisted Kabachnik–Fields reaction of a series of carboxylic acid amides, formaldehyde and secondary phosphine oxides. To compensate the lower reactivity of the –NH2 reagents, they had to be used in an excess. The solvolytic condensations furnished the α-aminophosphine oxides in yields of 58–93% after purification by chromatography. 相似文献
42.
We apply a PDE-based method to deduce the critical time and the size of the giant component of the “triangle percolation”
on the Erdős-Rényi random graph process investigated by Derényi, Palla and Vicsek in (Phys. Rev. Lett. 94:160202, [2005]; J. Stat. Phys. 128:219–227, [2007]). 相似文献
43.
Tamás Hergert Bálint Varga Angelika Thurner Ferenc Faigl Béla Mátravölgyi 《Tetrahedron》2018,74(16):2002-2008
5-Formyl-2-thiopheneboronic acid is a widely used building block for the synthesis of diverse structures, however, due to a significant instability its transformation to 5-arylthiophene-2-carboxaldehydes by CC couplings could be performed only in low yields. Herein, as a solution, a convenient technique is described for the preparation of 1,3-dioxolane-protected 5-arylthiophene-2-carboxaldehydes via a one-pot borylation–copper(I) chloride co-catalyzed Suzuki-Miyaura coupling reaction. The utilization of the in situ prepared 2-thiopheneboronic ester derivative is allowed by the method developed. Elimination of the crucial, acidic liberation step of boronic acid species resulted in improved yields and purities. In addition, comparison of various aryl bromides is shown to demonstrate the high tolerance of the transformation to functional groups. 相似文献
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45.
A new liquid chromatography-mass spectrometry (LC-MS)-based method coupled with pressurized liquid extraction (PLE) as an efficient sample preparation technique has been developed for the quantification and fingerprint analysis of Solanum xanthocarpum. Optimum separations of the samples were achieved on a Waters MSC-18 XTerra column, using 0.5% (v/v) formic acid in water (A) and acetonitrile (ACN):2-propanol:formic acid (94.5:5:0.5, v/v/v) (B) as mobile phase. The separation was carried out using linear gradient elution with a flow rate of 1.0mL/min. The gradient was: 0min, 20% B; 14min, 30% B; 20min, 30% B; 27min, 60% B and the column was re-equilibrated to the initial condition (20% B) for 10min prior to next injection. The steroidal glycoalkaloids (SGAs) which are the major active constituents were isolated as pure compounds from the crude methanolic extract of S. xanthocarpum by preparative LC-MS and after characterization were used as external standards for the development and validation of the method. Extracts prepared by conventional Soxhlet extraction, PLE and ultrasonication were used for analysis. The method was validated for repeatability, precision (intra- and inter-day variation), accuracy (recovery) and sensitivity (limit of detection and limit of quantitation). The purpose of the work was to develop a validated method, which can be used for the quantification of SGAs in commercialized S. xanthocarpum products and the fingerprint analysis for their routine quality control. 相似文献
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47.
Mukesh Kumar Biyala Krishna Sharma Monika Swami Nighat Fahmi Ran Vir Singh 《Transition Metal Chemistry》2008,33(3):377-381
The monobasic bidentate Schiff base complexes of palladium(II) and platinum(II) derived from 1H-indol-2,3-dione thiosemicarbazone
(L1H) and 1H-indol-2,3-dione semicarbazone (L2H) have been characterized on the basis of elemental analysis, molecular weight determinations, i.r., 1H n.m.r. and u.v. spectral studies. Based on these studies a square planar environment around the metal atoms has been proposed.
Antimicrobial effects of both the ligands and their complexes on different species of pathogenic fungi and bacteria have been
recorded and these are found to possess significant fungicidal and bactericidal properties. 相似文献
48.
Megyes T Bálint S Bakó I Grósz T Pálinkás G 《Journal of the American Chemical Society》2008,130(29):9206-9207
Wide-angle X-ray diffraction and molecular dynamics simulation has been used to perform complete structural characterization of nitromethane solution of a 16-membered gold(I) ring. The joint application of these two methods was an adequate tool to describe not only the structure of the complex but also the solvation properties of the complex in nitromethane and the effect of the solvation on the bulk structure. It has been found that a relatively diffuse slightly distorted solvation shell is formed around the complex, following the shape of the molecule. Nitromethane molecules in the solvation sphere are distributed randomly; no special orientation can be detected. The interaction energy of the complex with nitromethane molecules is attractive. In bulk, besides the antiparallel orientation of the nitromethane molecules, T-shape orientation and long-range order in antidipole orientation can also be detected. 相似文献
49.
Gyrgy Keglevich Helga Szelke gnes Blint Tímea Imre Krisztina Ludnyi Zoltn Nagy Mikls Hanusz Klmn Simon Veronika Harmat Lszl Tke 《Heteroatom Chemistry》2003,14(5):443-451
A series of new P‐methylphenyl P‐heterocycles are introduced. The para and ortho substituted 2,5‐dihydro‐1H‐phosphole oxides ( 1a and 1b ) were converted to the double‐bond isomers ( A and B ) of 1,2‐dihydrophosphinine oxides ( 3a and 3b ) via the corresponding phosphabicyclo[3.1.0]hexane oxides ( 2a or 2b ). Isomeric mixture ( A and B ) of the dihydrophosphinine oxides ( 3a and 3b ) gave, in turn, the isomers ( A and B ) of phosphabicyclo[2.2.2]oct‐5‐enes ( 4a and 4b ) or a phosphabicyclo[2.2.2]octa‐5,7‐diene ( 5 ) in Diels‐Alder reaction with dienophiles. The bridged P‐heterocycles ( 4 and 5 ) were useful in the photo‐ or thermoinduced fragmentation‐related phosphinylation of hydroxy compounds and amines. The new precursors ( 4a and 4b ) were applied in mechanistic investigations. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:443–451, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10176 相似文献
50.