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41.
Optimization of o‐phtaldialdehyde/2‐mercaptoethanol postcolumn reaction for the hydrophilic interaction liquid chromatography determination of memantine utilizing a silica hydride stationary phase 下载免费PDF全文
A rapid procedure for the determination of memantine based on hydrophilic interaction chromatography with fluorescence detection was developed. Fluorescence detection after postcolumn derivatization with o‐phtaldialdehyde/2‐mercaptoethanol was performed at excitation and emission wavelengths of 345 and 450 nm, respectively. The postcolumn reaction conditions such as reaction temperature, derivatization reagent flow rate, and reagents concentration were studied due to steric hindrance of amino group of memantine. The derivatization reaction was applied for the hydrophilic interaction liquid chromatography method which was based on Cogent Silica‐C stationary phase with a mobile phase consisting of a mixture of 10 mmol/L citric acid and 10 mmol/L o‐phosphoric acid (pH 6.0) with acetonitrile using an isocratic composition of 2:8 v/v. The benefit of the reported approach consists in a simple sample pretreatment and a quick and sensitive hydrophilic interaction chromatography method. The developed method was validated in terms of linearity, accuracy, precision, and selectivity according to the International Conference on Harmonisation guidelines. The developed method was successfully applied for the analysis of commercial memantine tablets. 相似文献
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Bahare Sadeghi Far Gholamhossein Grivani Aliakbar Dehno Khalaji Mahdi Khorshidi Václav Eigner Michal Dušek 《Journal of Cluster Science》2017,28(6):3217-3227
New centrosymmetric trinuclear zinc(II) complex {[Zn(μ-ONN)(μ2-O)(μ-OO)]2Zn} has been synthesized by the reaction of a potentially ONN tridentate Schiff base ligand, and N,N-dimethylethylendiamin, with Zn(OAc)2·2H2O in methanol, in the refluxed conditions and characterized by elemental analysis, FT-IR and UV–Vis spectroscopy. Single crystal X-ray structure analysis reveals a trinuclear complex {[Zn(μ-ONN)(μ2-O)(μ-OO)]2Zn} with zinc(II) ions connected by three different bridges, (μ-ONN) of the Schiff base ligand, μ2-O and μ-OO of the acetate. The complex is centrosymmetric, with one of the Zn atoms located at the inversion center. While the central Zn(II) ion is six-coordinated, the coordination number of the other Zn(II) ions is five. Finally, the {[Zn(μ-ONN)(μ2-O)(μ-OO)]2Zn} complex was thermally decomposed in air at 700 °C resulted in ZnO nano crystalites with the average size of 42 nm. The antibacterial activity of ligand and its zinc(II) complex were tested against gram-positive and gram-negative bacteria. The ligand showed higher activity than its zinc(II) complex. 相似文献
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Shicheng Shi Prof. Dr. Michal Szostak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(30):10420-10424
The first Negishi cross‐coupling of amides for the synthesis of versatile diaryl ketones by selective C?N bond activation under exceedingly mild conditions is reported. The cross‐coupling was accomplished with bench‐stable, inexpensive precatalyst [Ni(PPh3)2Cl2] that shows high functional‐group tolerance and enables the synthesis of highly functionalized diaryl ketone motifs. The coupling occurred with excellent chemoselectivity favoring the ketone (cf. biaryl) products. Notably, this process represents the mildest conditions for amide N?C bond activation accomplished to date (room temperature, <10 min). Considering the versatile role of polyfunctional biaryl ketone linchpins in modern organic synthesis, availability, and excellent functional‐group tolerance of organozinc reagents, this strategy provides a new platform for amide N?C bond/organozinc cross‐coupling under mild conditions. 相似文献
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Shicheng Shi Prof. Dr. Roger Lalancette D.Sc. Roman Szostak Prof. Dr. Michal Szostak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):11949-11953
Samarium(II) iodide enables a wide range of highly chemoselective umpolung radical transformations proceeding by electron transfer to carbonyl groups; however, cyclizations of important nitrogen‐containing precursors have proven limited due to their prohibitive redox potential. Herein, we report the first reductive cyclizations of unactivated cyclic imides onto N‐tethered olefins using SmI2/H2O. This new umpolung protocol leads to the rapid synthesis of nitrogen‐containing heterocycles that are of particular significance as precursors to pharmaceutical pharmacophores and numerous classes of alkaloids. The reaction conditions tolerate a wide range of functional groups. Excellent chemoselectivity is observed in the cyclization over amide and ester functional groups. Such unconventional reactivity has important implications for the design and optimization of new bond‐forming reactions by umpolung radical processes. The reaction advances the SmI2 cyclization platform to the challenging unactivated N‐tethered acyl‐type radical precursors to access nitrogen‐containing architectures. 相似文献
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Dr. Vittorio Pace Prof. Dr. Wolfgang Holzer Guangrong Meng Shicheng Shi Prof. Dr. Roger Lalancette D.Sc. Roman Szostak Prof. Dr. Michal Szostak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14494-14498
Herein, we show that acyclic amides that have recently enabled a series of elusive transition‐metal‐catalyzed N?C activation/cross‐coupling reactions are highly twisted around the N?C(O) axis by a new destabilization mechanism of the amide bond. A unique effect of the N‐glutarimide substituent, leading to uniformly high twist (ca. 90°) irrespective of the steric effect at the carbon side of the amide bond has been found. This represents the first example of a twisted amide that does not bear significant steric hindrance at the α‐carbon atom. The 15N NMR data show linear correlations between electron density at nitrogen and amide bond twist. This study strongly supports the concept of amide bond ground‐state twist as a blueprint for activation of amides toward N?C bond cleavage. The new mechanism offers considerable opportunities for organic synthesis and biological processes involving non‐planar amide bonds. 相似文献
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McKeown BA Gonzalez HE Friedfeld MR Gunnoe TB Cundari TR Sabat M 《Journal of the American Chemical Society》2011,133(47):19131-19152
Cationic platinum(II) complexes [((t)bpy)Pt(Ph)(L)](+) [(t)bpy =4,4'-di-tert-butyl-2,2'-bipyridyl; L = THF, NC(5)F(5), or NCMe] catalyze the hydrophenylation of ethylene to generate ethylbenzene and isomers of diethylbenzene. Using ethylene as the limiting reagent, an 89% yield of alkyl arene products is achieved after 4 h at 120 °C. Catalyst efficiency for ethylene hydrophenylation is diminished only slightly under aerobic conditions. Mechanistic studies support a reaction pathway that involves ethylene coordination to Pt(II), insertion of ethylene into the Pt-phenyl bond, and subsequent metal-mediated benzene C-H activation. Studies of stoichiometric benzene (C(6)H(6) or C(6)D(6)) C-H/C-D activation by [((t)bpy)Pt(Ph-d(n))(THF)](+) (n = 0 or 5) indicate a k(H)/k(D) = 1.4(1), while comparative rates of ethylene hydrophenylation using C(6)H(6) and C(6)D(6) reveal k(H)/k(D) = 1.8(4) for the overall catalytic reaction. DFT calculations suggest that the transition state for benzene C-H activation is the highest energy species along the catalytic cycle. In CD(2)Cl(2), [((t)bpy)Pt(Ph)(THF)][BAr'(4)] [Ar' = 3,5-bis(trifluoromethyl)phenyl] reacts with ethylene to generate [((t)bpy)Pt(CH(2)CH(2)Ph)(η(2)-C(2)H(4))][BAr'(4)] with k(obs) = 1.05(4) × 10(-3) s(-1) (23 °C, [C(2)H(4)] = 0.10(1) M). In the catalytic hydrophenylation of ethylene, substantial amounts of diethylbenzenes are produced, and experimental studies suggest that the selectivity for the monoalkylated arene is diminished due to a second aromatic C-H activation competing with ethylbenzene dissociation. 相似文献
50.
Michaela Mačková Michal Himl Jan Budka Michaela Pojarová Ivana Císařová Václav Eigner Petra Cuřínová Hana Dvořáková Pavel Lhoták 《Tetrahedron》2013,69(4):1397-1402
Methylation of 5,11,17,23-tetranitrothiacalix[4]arene with diazomethane leads to the tetramethoxy derivative, which was studied using single-crystal X-ray crystallography. It revealed that this compound, albeit in the 1,3-alternate conformation, can form the inclusion complexes with various solvent molecules possessing acidic methyl groups (ethyl acetate, nitromethane, acetone, acetonitrile) and creates interesting infinite channels filled with solvent molecules. The subsequent transformation of nitro groups into the ureido moieties gave receptors capable of anion recognition even in a highly HB-competitive solvent like DMSO. 相似文献