Direct CH Bond Activation of Benzoxazole and Benzothiazole with Aryl Bromides Catalyzed by Palladium(II)-N-heterocyclic Carbene Complexes

Herein, we report that a series of novel palladium(II)-NHC complexes (NHC=N-heterocyclic carbene) were synthesized. The structures of all novel complexes were characterized by H-1 NMR, C-13 NMR, FT-IR spectroscopy and elemental analysis techniques. These palladium(II)-NHC complexes were tested as efficient catalysts in the direct CH bond activation of benzoxazole and benzothiazole with aryl bromides in the presence of 1 mol% catalyst loading at 150 degrees C for 4 h. Under the given conditions, various aryl bromides were successfully applied as the arylating reagents to achieve the 2-arylbenzoxazoles and 2-arylbenzothiazoles in acceptable to high yields.