The first use of [PdBr2(imidazolidin-2-ylidene)(pyridine)] catalysts in the direct C-H bond arylation of C2-substituted furan and thiophene

N-Heterocyclic carbene (NHC)-linked PEPPSI-type palladium complexes have recently been used in the direct C-H bond arylation of heteroarenes. However, in most of the published works, NHC ligands containing benzimidazole and imidazole ring have been used, but using NHC ligands containing saturated imidazoline ring is quite rare. Therefore, in this study, four new 1,3-disubstituted imidazolinium salts as NHC ligand precursors, and their four new PEPPSI-type palladium complexes were synthesized. The structures of all new compounds were fully characterized by different spectroscopic and analytical techniques. The more detailed structural characterization of one of the palladium complexes was determined by single-crystal X-ray diffraction study. The catalytic activities of all palladium complexes were evaluated in the direct C-H bond arylation of the 2-acetylfuran and 2-acetylthiophene with (hetero) aryl bromides and readily available and inexpensive aryl chlorides in presence of 1 mol% catalyst loading at 120 degrees C. Under the given conditions, (hetero)aryl halides were successfully applied as the arylating reagents to achieve the C5-arylated furans and thiophenes in acceptable to high yields.