Synthesis of novel palladium(II) N-heterocyclic carbene complexes and their catalytic activities in the direct C5 arylation reactions

Abstract

New palladium(II) N-heterocyclic carbene complexes have been easily obtained in good yields from the carbene transfer reaction of silver-NHC complexes with PdCl2(PhCN)(2) and characterized by elemental analysis, H-1 NMR and C-13 NMR spectroscopy. These complexes were used as catalysts in the direct C5 arylation of 2-n-butylfuran, 2-n-butylthiophene and 2-n-propylthiazole with various aryl bromides at 130 degrees C in N,N-dimethylacetamide (DMAc) for 1 h. The arylation reactions were regioselective, and in all cases, only the C5-arylated products were formed. The corresponding arylation products were obtained in moderate to good yields by using 0.5 mol% of palladium-NHC complexes. (C) 2016 Elsevier B.V. All rights reserved.