Phosphine-Free Palladium Catalytic System for the Selective Direct Arylation of Furans or Thiophenes bearing Alkenes and Inhibition of Heck-Type Reaction
Résumé
Palladium acetate associated to potassium carbonate as catalytic system has been found to efficiently catalyse the direct 5-arylation of furans or thiophenes bearing enal, enone or acrylate functions at carbon C-2, and to inhibit the Heck-type reaction. The nature of the base is crucial to control the selectivity of the arylation. In the presence of electron-deficient aryl bromides and potassium carbonate as the base, the direct arylation is favoured, whereas the use of potassium fluoride gave selectively the Heck-type product, and tri-n-butylamine the reductive addition product.