Palladium-Catalysed Regioselective Sequential C-5 and C-2 Direct Arylations of 3-Acetylpyrroles with Aryl Bromides
Résumé
The PdCl(C3H5)(dppb)/KOAc system was found to be effective for the direct regioselective C-5 arylation of 3-acetylpyrroles with ortho-substituted aryl bromides. This procedure has been found to be tolerant to a variety of functional groups at C-2 of the aryl bromide such as methyl, formyl, nitrile, nitro, hydroxymethyl, chloro, fluoro or trifluoromethyl. The sequential direct C-5 arylation followed by C-2 arylation of such 3-substituted pyrroles allows the synthesis of 2,5-diaryl-3-acetylpyrroles in high yields.