Dichlorido(3-chloropyridine-N)[1,3-dialkylbenzimidazol-2-ylidene]palladium(II) complexes: Synthesis, characterization and catalytic activity in the arylation reaction

Abstract

Six novel Pyridine Enhanced Precatalyst Preparation, Stabilization and Initiation (PEPPSI) themed palladium N-heterocyclic carbene (Pd-NHC) complexes (2a–f) were synthesized in good yields from the reaction of 1,3-dialkylbenzimidazolium salts with PdCl2 in the presence of K2CO3 as base in 3-chloropyridine. These synthesized complexes were characterized by means of elemental analysis, FT-IR, 1H and 13C NMR spectroscopic methods. The fully characterized novel complexes (2a–f) were tested as catalysts in the direct arylation of 2-n-propylthiazole, 2-n-butylthiophene and 2-n-butylfuran with different aryl bromides at 130°C for 1h. The complexes exhibited fairly high catalytic activities under the given conditions. The highest conversions were achieved when complexes 2a, 2e and 2f were used as catalysts in direct arylation.