Catalytic activities in the direct C5 arylation of novel palladium N-heterocyclic carbene complexes containing benzimidazol-2-ylidene nucleus

Abstract

New palladium N-heterocyclic carbene (NHC) complexes (1a–e) were synthesized in very good yields by the reaction of 1-phenyl-3-alkylbenzimidazolium salts with Pd(OAc)2 in dimethyl sulfoxide. These synthesized complexes were fully characterized using elemental analyses, FT-IR, 1H NMR, 13C NMR and LC–MS (for 1a, 1c and 1e) spectroscopy data. Also, the molecular structure of the bis[1-phenyl-3-(2-methyl-1,4-benzodioxane)benzimidazol-2-ylidene]dibromopalladium(II) complex (1d) was structurally characterized by single crystal X-ray diffraction study. The new PdII complexes (1a–e) were tested as catalysts in the direct C5 arylation of 2-n-butylfuran, 2-n-butylthiophene and 2-n-propylthiazole with various aryl bromides at 130°C for 1h. Also, some experiments were carried out by using aryl chlorides in order to be used for comparison. The results are reported herein. These complexes exhibited quite high catalytic activities under the given conditions.