A Novel Task-Specific Ionic liquid Supported on Magnetic Nanoparticles as a Highly Water-Dispersible Catalyst for Aqueous Phase Suzuki Reaction

Palladium-catalyzed Suzuki cross-coupling reaction is one of the most important and versatile transformations in biaryl synthesis from both academic and industrial viewpoints [1]. Despite the considerable success achieved in the field of magnetically separable nanocatalysts [2], the application of these systems in water as a green solvent has still remained a great challenge in the Suzuki reaction in which water-soluble boronic acids fall off to the homocoupling reaction or hydrolytic deboronation as side reactions. Therefore, it seems that there is still much room to make novel magnetically recyclable catalysts displaying improved catalytic performance in pure water. Here, a novel ionic liquid functionalized magnetic nanoparticle was prepared by anchoring an imidazolium ionic liquid bearing triethylene glycol moieties on the surface of silica-coated iron oxide nanoparticles. The material proved to be an effective host for the immobilization of a Pd catalyst through a subsequent simple ion-exchange process giving a highly water dispersible, active and yet magnetically recoverable Pd catalyst in the Suzuki coupling reaction of challenging substrates such as heteroaryl halides and ortho-substituted aryl halides as well as aryl chlorides in water. Since the catalyst exhibited extremely low solubility in organic solvent, the recovered aqueous phase containing the catalyst can be simply and efficiently used in ten consecutive runs without significant decrease in activity and at the end of the process can be easily separated from the aqueous phase by applying an external magnetic field. This novel double-separation strategy with negligible leaching makes the material an eco-friendly and economical catalyst to perform this transformation.