Palladium-Catalyzed Regioselective Direct Arylation of Benzofurazans at the C-4 Position

The palladium-catalyzed direct arylation of benzofurazans with aryl bromides to access 4-ary-lbenzofurazans proceeds in moderate-to-high yields using phosphine-free palladium acetate as the catalyst and potassium acetate as an inexpensive base. A wide variety of (hetero) aryl bromides, including bromopyridine and bromothiophene derivatives has been successfully employed. Palladium-catalyzed one-pot C-4, C-7-diarylation of benzofurazan was also achieved using a larger amount of aryl bromide. Moreover, the derivatization of 4-arylbenzofurazans into 4-arylquinaxolines is also reported.