A mild, general, and convenient palladium-catalyzed direct arylation of the 5-position of azoles with aryl bromides, efficiently promoted by tetrabutylammonium acetate, is described. 1-Methylpyrazole, oxazole, and thiazole reacted at 70 degrees C in N,N-dimethylacetamide by using Pd(OAc)(2) as the catalyst precursor. Electron-poor and -rich functional groups, including the free hydroxy group, are well tolerated in the electrophilic partner. A variety of 5-aryl-1-methylimidazoles were also very efficiently obtained simply by raising the reaction temperature to 110 degrees C. This ligand-free protocol was successfully applied to the one-pot synthesis of two bioactive natural compounds, balsoxin and texaline, starting from oxazole by sequential direct arylation of the 5- and 2-positions.
Autori interni: | |
Autori: | Bellina, Fabio; Lessi, Marco; Manzini, Chiara |
Titolo: | Mild Palladium-Catalyzed Regioselective Direct Arylation of Azoles Promoted by Tetrabutylammonium Acetate |
Anno del prodotto: | 2013 |
Abstract: | A mild, general, and convenient palladium-catalyzed direct arylation of the 5-position of azoles with aryl bromides, efficiently promoted by tetrabutylammonium acetate, is described. 1-Methylpyrazole, oxazole, and thiazole reacted at 70 degrees C in N,N-dimethylacetamide by using Pd(OAc)(2) as the catalyst precursor. Electron-poor and -rich functional groups, including the free hydroxy group, are well tolerated in the electrophilic partner. A variety of 5-aryl-1-methylimidazoles were also very efficiently obtained simply by raising the reaction temperature to 110 degrees C. This ligand-free protocol was successfully applied to the one-pot synthesis of two bioactive natural compounds, balsoxin and texaline, starting from oxazole by sequential direct arylation of the 5- and 2-positions. |
Digital Object Identifier (DOI): | 10.1002/ejoc.201300704 |
Appare nelle tipologie: | 1.1 Articolo in rivista |