Efficient N-heterocyclic carbene palladium(II) catalysts for carbonylative Suzuki-Miyaura coupling reactions leading to aryl ketones and diketones

摘要

New N, N′-substituted imidazolium salts (L1andL2) and their corresponding diiodopyridinepalladium(II) complexes (C1andC2) were successfully synthesized and characterized. Reactions of palladium iodide with the newly synthesized N, N′-substituted imidazolium iodides in pyridine afforded the corresponding new palladium-N-heterocyclic carbene pyridine complexes in high yields. The new palladium(II) complexC1was characterized by single crystal X-ray diffraction analysis. The Pd(II) ion is bonded to the nitrogen atom of the pyridine, the carbon atom of the NHC carbene ligand and two trans iodides resulting in distorted square planar geometry. The two Pd-NHC-Py complexesC1andC2displayed higher catalytic activity in the carbonylative Suzuki-Miyaura coupling reactions with much lower catalyst loading as compared to the catalytic systems reported in the literature.