Ligand-less Pd(OAc)₂ provides a very efficient catalyst for the direct 5-arylation of thiophene derivatives. With this catalyst, a low palladium concentration (0.1–0.001 mol%) should be employed in order to obtain high yields of coupling products. At higher concentrations a fast formation of inactive “Pd black” generally occurs. Substrates/catalysts ratios up to 100000 can be employed with the most reactive aryl bromides. A very wide variety of functional groups is tolerated on both coupling partners. The major waste of this reaction is HBr associated with KOAc. Therefore this procedure is more economically and environmentally attractive than the traditional cross-coupling procedures employing organometallic derivatives.

The palladium-catalysed direct 2-, 4- or 5-arylation of a wide range of heteroaromatics with aryl halides proceed in moderate to good yields using the eco-friendly solvents carbonates. The best yields were obtained using benzoxazole or thiazole derivatives. The arylation of furan, thiophene, pyrrole, imidazole or isoxazole derivatives was found to require a more elevated reaction temperature.