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 2 (NHC)(pyridine)]. The structures of all compounds were characterized by various spectroscopic techniques such as 1 H NMR, 13 C 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.