PdCl2-2,6-bis(1,5-diphenyl-1H-pyrazol-3-yl)pyridine catalyzed Suzuki–Miyaura cross-coupling

Six multidentate nitrogen ligands, 2,6-bis(1,5-diphenyl-1H-pyrazol-3-yl)pyridine (L1), 2,6-bis(1-methyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L2), 2,6-bis(1,5-dimethyl-1H-pyrazol-3-yl)pyridine (L3), 2,6-bis(5-phenyl-1H-pyrazol-3-yl)pyridine (L4), 2,6-bis(1-p-triflurophenyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L5), and 2,6-bis(1-m-methylphenyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L6) were synthesized and characterized. Their palladium complexes catalyzed Suzuki–Miyaura cross-coupling revealed that the catalytic activities of these complexes were in the order of PdCl2-L5 > PdCl2-L1 > PdCl2-L6 > PdCl2-L2 > PdCl2-L3 > PdCl2-L4. With a low Pd loading of 10− 5 mol%, PdCl2-L1 showed a high activity. The turnover numbers (TONs) were up to 58,000,000 for 4-bromobenzotrifluoride.

► A family of nitrogen ligand is synthesized and characterized.
► The effect of ligands structure on Suzuki reaction is investigated.
► PdCl2-L1 system shows the high activity to aryl halides under aerobic condition and gives a maximum TON of 58,000,000.