Mild and ligand-free palladium-catalyzed cross-couplings between aryl halides and arylboronic acids for the synthesis of biaryls and heterocycle-containing biaryls

Ligand-free palladium-catalyzed Suzuki-Miyaura cross-couplings between aryl halides and arylboronic acids performed at room temperature are presented. It was found that both solvent and base had a fundamental influence on the reaction, and the most effective system in terms of yield and rate was observed to be the combination of Pd(OAc)(2) with MeONa and alcohols. In the presence of Pd(OAc)(2) and MeONa, a variety of aryl halides reacted very rapidly with arylboronic acids in good to excellent yields at room temperature in EtOH as the solvent. Moreover, the Pd(OAc)(2)/ MeONa catalytic system could also be applied in couplings between heteroaryl halides and arylboronic acids to provide satisfactory results in MeOH as the solvent after prolonged reaction times. It is noteworthy that the reactions were conducted under mild, aerobic, and ligand-free conditions. ((c) Wiley-VCH Verlag GmbH & Co.