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

Abstract

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 N4-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 %) .