Palladium-Catalyzed Phosphine-Free Direct C-H Arylation of Benzothiophenes and Benzofurans Involving MIDA Boronates

With high regioselectivity, a series of benzoheterocyclic compounds were synthesized via palladiium-catalyzed phosphine-free C-H arylation of benzothiophenes/benzofurans with aryl MIDA boronates at 30-50 degrees C in moderate to excellent yields. MIDA boronates were used in C-H arylation of heterocycles for the first time. Under the optimal conditions, the benzothiophenes could be transformed into the beta-arylbenzothiophenes, and the benzofurans gave only alpha-aryl-substituted products.