Well-Defined PEPPSI-Themed Palladium–NHC Complexes: Synthesis, and Catalytic Application in the Direct Arylation of Heteroarenes

Abstract

In this study, a series of benzimidazolium salts were synthesized as unsymmetrical N-heterocyclic carbene (NHC) precursors. Benzimidazolium salts were used for synthesis of the PEPPSI (pyridine enhanced precatalyst preparation stabilization and initiation)-themed, six new Pd-complexes with the general formula [PdX<inf>2</inf>(NHC)(pyridine)]. The structures of all compounds were characterized by various spectroscopic techniques such as 1H NMR, 13C NMR and FT-IR. The more detailed structural characterization of four of the complexes was determined by single-crystal X-ray diffraction study. The catalytic activities of all Pd-complexes were evaluated in the direct arylation of the 2-acetylfuran and 2-acetylthiophene with aryl bromides in the presence of 1 mol% catalyst loading. © 2019 John Wiley & Sons, Ltd.