Palladium-bis(oxazoline) complexes with inherent chirality: Synthesis, crystal structures and applications in Suzuki, Heck and Sonogashira coupling reactions

摘要

New palladium-bis(oxazoline) (Pd-BOX) complexes were synthesized and characterized. The X-ray crystal structures of the two complexes showed that the palladium ion is bound to the nitrogen atoms of the two heterocycles of the bidentate ligand and two chloride ions in a distorted square planar geometry. The coordination to the palladium ion allows these non C_2-symmetric bis(oxazoline) ligand-based complexes to acquire a rigid backbone curvature generating an inherent chirality. The catalytic activities were evaluated in Suzuki-Miyaura, Mizoroki-Heck and Sonogashira coupling reactions. The complexes showed high catalytic activities towards numerous C-C coupling reactions with various aryl halides, aryl boronic acids, alkenes and alkynes. The reactions were optimized for the most suitable temperature, solvent, and base system.