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

Herein we report synthesis of seven new palladium(II)‐NHC complexes with the general formula [PdX 2 (NHC) 2 ], (NHC=1,3‐dialkylbenzimidazol‐2‐ylidene, X=Cl or Br). The structures of all the new compounds were characterized by 1 H NMR, 13 C 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.