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.

Mild Palladium-Catalyzed Regioselective Direct Arylation of Azoles Promoted by Tetrabutylammonium Acetate

BELLINA, FABIO;LESSI, MARCO;MANZINI, CHIARA
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.
Bellina, Fabio; Lessi, Marco; Manzini, Chiara
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/309867
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