Synthesis of Unsymmetrically Substituted Bipyridines by Palladium-Catalyzed Direct C−H Arylation of Pyridine <i>N</i>-Oxides
作者:Sasa Duric、C. Christoph Tzschucke
DOI:10.1021/ol200565u
日期:2011.5.6
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
Palladium-Catalyzed Directed Halogenation of Bipyridine <i>N</i>-Oxides
作者:Sina P. Zucker、Friedrich Wossidlo、Manuela Weber、Dieter Lentz、C. Christoph Tzschucke
DOI:10.1021/acs.joc.7b00444
日期:2017.6.2
The palladium-catalyzed directed C–H halogenation of bipyridine N-oxides was investigated. Using NCS or NBS (N-chloro- or N-bromosuccinimide) and 5 mol % Pd(OAc)2 in chlorobenzene (0.10 molar) at 110 °C, pyridine-directed functionalization took place and 3-chloro- or 3-bromobipyridine N-oxides were obtained in high yields. The reaction is sensitive to steric hindrance by 4- and 6′-substituents. Only
Copper powder-catalyzed N-arylation of imidazoles in water using 2-(hydrazinecarbonyl)pyridine N-oxides as the new ligands
作者:Feng-Tian Wu、Nan-Nan Yan、Ping Liu、Jian-Wei Xie、Yan Liu、Bin Dai
DOI:10.1016/j.tetlet.2014.04.039
日期:2014.5
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.
Quaternary <i>N</i>-(2-Pyridyl)-DABCO Salts: One-Pot in Situ Formation from Pyridine-<i>N</i>-oxides and Reactions with Nucleophiles: A Mild and Selective Route to Substituted <i>N</i>-(2-Pyridyl)-<i>N</i>′-ethylpiperazines
作者:Dmitry I. Bugaenko、Marina A. Yurovskaya、Alexander V. Karchava
DOI:10.1021/acs.joc.6b02952
日期:2017.2.17
simple, metal-free, one-pot synthetic procedure involves the initial reaction of activated heterocyclic N-oxides with DABCO, followed by in situ treatment of the resultant quaternary N-(2-pyridyl)-DABCO salts with nucleophiles, resulting in ring-opening. The method features mild reaction conditions, high positional selectivity, and excellent functional-group tolerance. The utility of our approach is demonstrated
Facile Route to 2-Fluoropyridines via 2-Pyridyltrialkylammonium Salts Prepared from Pyridine <i>N</i>-Oxides and Application to <sup>18</sup>F-Labeling
作者:Hui Xiong、Adam T. Hoye、Kuo-Hsien Fan、Ximin Li、Jennifer Clemens、Carey L. Horchler、Nathaniel C. Lim、Giorgio Attardo
DOI:10.1021/acs.orglett.5b01703
日期:2015.8.7
Among known precursors for 2-[18F]fluoropyridines, pyridyltrialkylammonium salts have shown excellent reactivity; however, their broader utility has been limited because synthetic methods for their preparation suffer from poor functional group compatibility. In this paper, we demonstrate the regioselective conversion of readily available pyridine N-oxides into 2-pyridyltrialkylammonium salts under mild