- Copper powder-catalyzed N-arylation of imidazoles in water using 2-(hydrazinecarbonyl)pyridine N-oxides as the new ligands
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2-(2-Hydrazinecarbonyl)pyridine N-oxides, which were derived from pyrrole-2-carbohydrazides and pyridine N-oxides, were synthesized and utilized as the ligands for copper powder-catalyzed N-arylation of imidazoles with aryl halides in water. Imidazoles could be arylated smoothly with various aryl halides to provide the title products in preferable yields without the need of an inert atmosphere.
- Wu, Feng-Tian,Yan, Nan-Nan,Liu, Ping,Xie, Jian-Wei,Liu, Yan,Dai, Bin
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supporting information
p. 3249 - 3251
(2014/06/09)
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- Synthesis of unsymmetrically substituted bipyridines by palladium-catalyzed direct C-H arylation of pyridine N -oxides
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Chemical equations presented. Substituted bipyridines were efficiently prepared by direct coupling between pyridine N-oxides and halopyridines using a palladium catalyst. Pyridine N-oxides with electron-withdrawing substitutents gave the best yields. This method allows the convenient preparation of 2,2′-, 2,3′-, and 2,4′-bipyridines which are useful as functionalized ligands for metal complexes or as building blocks for supramolecular architectures.
- Duric, Sasa,Tzschucke, C. Christoph
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supporting information; experimental part
p. 2310 - 2313
(2011/06/28)
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- Syntheses and Fe(II)/Fe(III) equilibria of the new multidentate ligands pyridine-2-phosphonic-6-carboxylic acid and 2,6-pyridinediphosphonic acid for the use of their iron chelates as catalysts for the oxidation of H2S to S8 by air
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The syntheses of two terdentate chelating agents, pyridine-2-phosphonic-6-carboxylic acid (2PP6C) and 2,6-pyridinediphosphonic acid (2,6PDPA), are described. The stepwise stability constants for the ferric complexes at 25.0°C and μ = 0.100 M (KNO3) are log KML = 15.97 and log KML2 = 9.50 for 2PP6C, and log KML = 20.87 and log KML2 = 7.81 for 2,6PDPA. Under the same conditions the stepwise formation constants for the ferrous chelates are log KML = 8.70 and log KML2 = 5.10 for 2PP6C, and log KML = 10.12 and log KML2 = 5.33 for 2,6PDPA. The stabilities of the Fe(III) and Fe(II) chelates are high enough to prevent precipitation of Fe(OH)3 and FeS, respectively, from solutions having pH as high as 10.0. The rates of oxidative degradation of these ligands are very slow when the iron chelates are used as redox catalysts for the oxidation of H2S to S8 by air. The rates of oxidative degradation are immeasurably slow when the iron chelates are used with sodium thiosulfate as a radical scavenger.
- Chen, Dian,Martell, Arthur E.,Motekaitis, Ramunas J.,McManus, Derek
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p. 445 - 451
(2007/10/03)
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