Chiral (Pyridine)-(Imidazoline) NCN? Pincer Palladium(II) Complexes: Convenient Synthesis via C-H Activation and Characterization

A series of aryl-based chiral NCN ' pincer palladium(II) complexes 4a-k were synthesized via C-H activation of the (pyridyl)-(imidazolinyl)benzene ligands, which proceeded smoothly with PdCl2 as the palladium source in the presence of Et3N or NaHCO3 base in toluene under reflux. All of the complexes have been characterized by elemental analysis and H-1 and C-13{H-1} NMR spectroscopy. In addition, the molecular structures of complexes 4a, 4c, and 4f have been determined by X-ray single-crystal diffraction analysis. The obtained chiral Pd pincers were applied to catalytic asymmetric reactions of acrylonitrile and dichloroacetonitrile with sulfonimines. With a catalyst loading of 5 mol % and the assistance of AgOAc, these complexes acted as active but moderately stereoselective catalysts for the aforementioned reactions.

Automated summary

A series of aryl-based chiral NCN ' pincer palladium(II) complexes were synthesized through C-H activation and were characterized and analyzed. These complexes showed moderate activity and stereoselectivity in catalytic asymmetric reactions.