Applications of quinoxaline-bridged bis(benzimidazolium) salts as ligand sources for the palladium-catalyzed Suzuki and Heck cross-coupling reactions in an aqueous medium

Abstract

In the present work, quinoxaline-bridged bis(benzimidazolium) salts were prepared by the reaction of 2,3-bis(bromomethyl) quinoxaline and 1-substituted benzimidazole. The structures of the bis(benzimidazolium) salts were characterized by NMR, FT-IR, and elemental analysis techniques. Also, the photophysical properties of salts were investigated by UV-Vis absorption and fluorescence emission spectroscopy. Next, these quinoxaline bridged bis(benzimidazolium) salts were used as bidentate benzimidazol-2-ylidene ligand precursors in the palladium-catalyzed Suzuki-Miyaura and Mizoroki-Heck cross-couplings. These salts exhibited moderate-to-high activity in the palladium-catalyzed cross-coupling reactions.