Direct C‐H Bond Arylation of C2‐Blocked Pyrrole with Aryl Halides Using Palladium(II)‐N‐Heterocyclic Carbene Catalysts

Abstract

AbstractHerein we report synthesis of seven new palladium(II)‐NHC complexes with the general formula [PdX2(NHC)2], (NHC=1,3‐dialkylbenzimidazol‐2‐ylidene, X=Cl or Br). The structures of all the new compounds were characterized by 1H NMR, 13C NMR, FT‐IR spectroscopy and elemental analysis techniques. The catalytic activities of palladium(II)‐NHC complexes were tested in the direct C−H bond arylation of C2‐blocked pyrrole with various aryl halides in presence of 1 mol% catalyst loading at 120 °C for 1–16 h. Under the given conditions, palladium(II)‐NHC complexes showed the good catalytic performance for the direct C−H bond arylation of C2‐blocked pyrrole with aryl bromides, and with readily available and inexpensive aryl chlorides. In all cases, the C−H bond arylation regioselectively produced C5‐arylated products in moderate to high yields.