Efficient Palladium-catalyzed Suzuki-Miyaura reactions using phenolic Schiff base ligands under ambient conditions in aqueous media

The palladium complexes of a series of simple Schiff base ligands with or without phenolic hydroxyl groups have been found to be the excellent catalysts for the Suzuki-Miyaura reactions of aryl iodides, aryl bromides and activated aryl chlorides under ambient conditions in aqueous ethanol media. The introduction of phenolic hydroxyl and/or pyridine groups to the ligands increased the catalytic activity. Under optimal reaction conditions, satisfactory to excellent yields of biaryls were obtained with a wide range of substrates for relatively low loadings of catalyst. Phenolic hydroxyl group and N-4-type Schiff base ligands (L1-2) have been proven to be the excellent catalysts for the Suzuki-Miyaura reactions of aryl iodides, aryl bromides and activated aryl chlorides in aqueous ethanol under ambient. Furthermore, a diverse choice of functionalized arylboronic acids bearing difluoro, trifluoro and trifluoromethyl substituents were successfully coupled (> 97 %).