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