- Palladium nanoparticles immobilized on a magnetic chitosan-anchored Schiff base: Applications in Suzuki-Miyaura and Heck-Mizoroki coupling reactions
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A palladium nanocatalyst Fe3O4@CS-SB-Pd has been synthesized and characterized by FT-IR, XRD, XPS, FESEM, EDX, TEM, TGA, and ICP-AES analysis. The nanocatalyst has been found to be an efficient and magnetically separable heterogeneous catalyst for Suzuki-Miyaura and Heck-Mizoroki coupling reactions at a low concentration (0.02 mol% of Pd). The nanocatalyst afforded arylated products with high TON (4950) and TOF (9900 h-1) in the Suzuki-Miyaura coupling reactions. However, for the Heck-Mizoroki coupling reaction, the values of TON and TOF were found to be 4900 and 7350 h-1, respectively. The nanocatalyst could be easily recovered from the reaction mixture by using an external magnet and recycled up to five times without significant decrease in its catalytic activity. All isolated products were obtained as white to off-white crystalline solids and brown oils and fully characterized by 1H and 13C NMR spectroscopy.
- Anuradha,Kumari, Shweta,Layek, Samaresh,Pathak, Devendra D.
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p. 5595 - 5604
(2017/07/11)
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- Synthesis and characterization of a new Pd(II)-Schiff base complex [Pd(APD)2]: An efficient and recyclable catalyst for Heck-Mizoroki and Suzuki-Miyaura reactions
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The synthesis of a new Schiff base ligand “4-((Z)-((Z)-3-hydroxy-1,3-diphenylallylidene)amino) -1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (APD)” and its palladium complex [Pd(APD)2] is described. The ligand and complex are characterized by FTIR, FESEM, EDX, Elemental analyses and Mass spectrometry. The structure of the ligand is also confirmed by single crystal X-ray determination and 1H NMR data. The complex is insoluble in almost all common organic solvents. It has been used as an efficient catalyst in a series of Heck-Mizoroki and Suzuki-Miyaura coupling reactions giving good TON and TOF. The ease of synthesis, air-stability and recyclability are some of the important characteristics of the synthesized catalyst.
- Layek, Samaresh,Anuradha,Agrahari, Bhumika,Pathak, Devendra D.
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p. 105 - 112
(2017/06/19)
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- Synthesis, dual fluorescence, and fluoroionophoric behavior of dipyridylaminomethylstilbenes
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The synthesis, dual fluorescence, and fluoroionophoric behavior of two donor-σ spacer-acceptor (D-s-A) compounds, trans-4-(N,N-bis(2-pyridyl) amino)methylstilbene (1H) and trans-4-(N,N-bis(2-pyridyl)amino)methyl-4′- cyanostilbene (1CN), are reported and compared to that of trans-4-(N,N-bis(2- pyridyl)amino)methyl-4′-(N,N-dimethylammo)stilbene (1DPA). To gain insights into the dual fluorescence properties for 1H and 1CN in polar but not in nonpolar solvents, model compounds resulting from a replacement of the stilbene group by alkyl (2R) or xylyl (2X) groups or from a replacement of the dipyridylamino (dpa) group by dianisoleamino (3AA), diethylamino (SEE), methylanilino (3MP), or diphenylamino (3PP) groups also have been investigated. In addition to 1H and 1CN, all four compounds of 3 display dual fluorescence. The locally excited (LE) fluorescence mainly results from the stilbene group and the ICT fluorescence from the through-bond interactions between the amino donor and the stilbene acceptors. In the presence of transition metal ions such as Zn(II), Ni(II), Cu(II), and Cd(II), the ICT processes are switched from dpa → stilbene (A) in 1H and 1CN to stilbene (D) → dpa/metal ion (A) in their complexes. Whereas the ICT states for the complexes are generally nonfluorescent, an exception was found for the case of 1H/Zn(II). As a result, substituent-dependent fluoroionophoric behavior has been demonstrated by 1H, 1CN, and 1DPA in response to Zn(II).
- Yang, Jye-Shane,Lin, Yan-Duo,Chang, Ya-Ho,Wang, Shin-Shin
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p. 6066 - 6073
(2007/10/03)
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- Preparation of stilbene-tethered nonnatural nucleosides for use with blue-fluorescent antibodies
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The synthesis of the first examples of stilbene-tethered hydrophobic C-nucleosides is described. Compounds of this type are targeted for use with our recently reported "blue-fluorescent antibodies with the aim of probing native and nonnatural DNA. The nucleophilic addition of aryl Grignard reagents to either a protected 2′-deoxy-1′-chloro-ribofuranose or a protected 2′-deoxy-ribonolactone was the key synthetic step and afforded C-nucleosides in good yields. Both routes resulted in a final product that was ≥ 90% of the β-anomer. Amide- and ether-based linkers for attachment of trans-stilbene to the nucleobase were assessed for utility during synthesis and in binding of the ligands to a blue-fluorescent monoclonal antibody. X-ray structures of each complex were obtained and serve as a guideline for second-generation stilbene-tethered C-nucleosides. The development of these hydrophobic nucleosides will be useful in current native and nonnatural DNA studies and invaluable for investigations regarding novel, nonnatural genomes in the future.
- Chen,Beuscher IV,Stevens,Wirsching,Lerner,Janda
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p. 1725 - 1732
(2007/10/03)
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- Esterification of carboxylic acid salts
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Mono- or polycarboxylic acid esters are prepared by reacting a salt of such carboxylic acid with an organic halocompound, e.g., a (cyclo)alkyl, (cyclo)alkenyl, aryl or aralkyl halide, in an aqueous reaction medium, in the presence of a catalytically effective amount of a phase transfer catalyst, for example an onium salt.
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