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Mild Palladium‐Catalyzed Regioselective Direct Arylation of Azoles Promoted by Tetrabutylammonium Acetate
Author(s) -
Bellina Fabio,
Lessi Marco,
Manzini Chiara
Publication year - 2013
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201300704
Subject(s) - chemistry , oxazole , regioselectivity , palladium , aryl , catalysis , thiazole , electrophile , combinatorial chemistry , ligand (biochemistry) , organic chemistry , medicinal chemistry , alkyl , receptor , biochemistry
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 °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 °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.