- Cu-catalyzed N- and O-arylation of 2-,3-, and 4-hydroxypyridines and hydroxyquinolines
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With use of Cu-based catalysts, 2- and 4-hydroxypyridines were N-arylated in modest to excellent yields. In the case of 2-hydroxypyridine, the use of 4,7-dimethoxy-1,10-phenanthroline, 3, expanded the scope of previous literature reports to include the use of N-containing heteroaryl halides, and 2-substituted aryl halides. In addition, by using a copper catalyst based on 2,2,6,6-tetramethylheptane-3,5-dione, 4, the first N-arylations of 4-hydroxypyridines and O-arylations of 3-hydroxypyridines with aryl bromides and iodides have been accomplished.
- Altman, Ryan A.,Buchwald, Stephen L.
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p. 643 - 646
(2008/02/03)
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- Highly efficient and mild copper-catalyzed N- and C-arylations with aryl bromides and iodides
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Mild, efficient, copper-catalyzed N-arylation procedures for nitrogen heterocycles, amides, carbamates, and C-arylation procedures for malonic acid derivatives have been developed that afford high yields of arylated products with excellent selectivity. The N-arylation of imidazole with aryl bromides or iodides was found to be greatly accelerated by inexpensive, air-stable catalyst systems, combining catalytic copper salts or oxides with a set of structurally simple chelating ligands. The reaction was shown to be compatible with a broad range of aryl halides, encompassing sterically hindered, electron-poor, and electron-rich ones, providing the arylated products under particularly mild conditions (50-82°C). The lower limit in ligand and catalyst loading and the scope of Ullmann-type condensations catalyzed by complexes bearing those ligands with respect to the nucleophile class have also been investigated. Chelating Schiff base Chxn-Py-Al (1c) generates a remarkably general copper catalyst for N-arylation of pyrrole, indole, 1,2,4-triazole, amides, and carbamates; and C-arylation of diethyl malonate, ethyl cyanoacetate, and malononitrile with aryl iodides under mild conditions (50-82°C). The new method reported here is the most successful to date with regard to Ullmann-type arylation of some of these nucleophiles.
- Cristau, Henri-Jean,Cellier, Pascal P.,Spindler, Jean-Francis,Taillefer, Marc
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p. 5607 - 5622
(2007/10/03)
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