Palladium(ii)/N-heterocyclic carbene (NHC) catalyzed direct C–H arylation of heteroarenes with different aryl bromides and chlorides

Abstract

The growing interest of industry in the field of bi(hetero)arene compounds motivated us to synthesize these compounds via a homogeneous catalytic route using Pd PEPPSI-type complexes through direct arylation. In this study, new Pd PEPPSI-type complexes bearing NHC spectator ligands were synthesized and characterized using spectroscopic techniques, such as ¹HNMR, ¹³C NMR, MS spectrometry, FTIR spectroscopy and elemental analysis (PEPPSI = pyridine enhanced precatalyst preparation stabilization and initiation). All the synthesized Pd(II) complexes were stable. The catalytic properties of these complexes were evaluated in the direct C₅ mono-arylation of furan, 2-acetylthiophene and N-methylpyrrole-2-carboxaldehyde derivatives with a wide variety of (hetero)aryl halides. This environmentally attractive procedure was found to be tolerant of a wide variety of functional groups on the aryl halides and good yields were obtained in the presence of 1 mol% catalyst loading at 150 °C for 2 hours. In addition, the conversions for substrates containing electron-withdrawing groups were higher than those for substituents containing electron-donating groups.