Ligand-free palladium-catalyzed direct arylation of thiazoles at low catalyst loadings.

Ligand-free Pd(OAc)2 was found to catalyze very efficiently the direct arylation of thiazole derivatives under very low catalyst concentration. By using activated aryl bromides, the reaction can be performed employing as little as 0.1-0.001 mol % catalyst. With such substrates, this procedure is economically and environmentally attractive. On the other hand, in the presence of more challenging substrates, such as some strongly deactivated or highly congested aryl bromides, in some cases, disappointing results were obtained.