5-Nitrobenzimidazole containing Pd(II) catalyzed C[sbnd]C cross-coupling reactions: The effect of the N-substituent of the benzimidazole structure on catalyst activity

Abstract

A series of Pd(II) complexes (1a-e) were successfully synthesized by reaction of N-substituted 5-nitrobenzimidazole with [PdCl2(CNCH3)2] in toluene under argon reflux condition. Their catalytic activity in the Suzuki-Miyaura and Mizoroki-Heck coupling reactions were investigated. All these complexes were characterized by elemental analysis, 1H NMR, 13C NMR and IR spectroscopy. The catalytic activities of N-substituted 5-nitrobenzimidazole palladium (II) complexes were screened in Mizoroki-Heck and Suzuki-Miyaura coupling reactions. The reactions were optimized for the most suitable temperature, solvent and base system. The Pd(II) complexes exhibited good catalytic activity at the Mizoroki-Heck reaction. Additionally, the Suzuki-Miyaura showed relatively excellent activity at the coupling reaction.