The direct C(sp(2))-H functionalization and coupling of aromatic N-heterocycles with (hetero)aryl bromides by [PdX2(imidazolidin-2-ylidene)(Py)] catalysts

In this study, a series of air- and moisture-stable imidazolidin-2-ylidene-based new palladium complexes with the general formula [PdX2(NHC)(Py)] were synthesized (NHC = N-heterocyclic carbene, Py = pyridine, X = Cl or I). The structures of the palladium complexes were characterized by different techniques such as H-1 NMR, C-13 NMR, FT-IR spectroscopy and elemental analysis. The more detailed structural characterization of one of the palladium complex was determined by single-crystal X-ray diffraction study. The catalytic activities of all palladium complexes were tested in the direct arylation of five-membered aromatic N-heterocycles such as 3,5-dimethylisoxazole and 1-methyl-1H-pyrrole-2-carboxaldehyde with (hetero)aryl bromides in presence of 1 mol% catalyst loading at 120 degrees C. Desired products were obtained in moderate to good yields. (C) 2021 Elsevier B.V. All rights reserved.