Highly efficient and mild copper-catalyzed N- and C-arylations with aryl bromides and iodides |
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Authors: | Cristau Henri-Jean Cellier Pascal P Spindler Jean-Francis Taillefer Marc |
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Institution: | Laboratoire de Chimie Organique, UMR CNRS 5076 et Ecole Nationale Supérieure de Chimie de Montpellier, 8 rue de L'Ecole Normale, 34296 Montpellier 5, France. cristau@cit.enscm.fr |
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Abstract: | 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 degrees 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 degrees C). The new method reported here is the most successful to date with regard to Ullmann-type arylation of some of these nucleophiles. |
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Keywords: | arylation copper homogeneous catalysis N O ligands nucleophilic substitution |
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