Palladium-Catalyzed C–H Arylation of Indoles at the C7 Position

In the past decade, direct C–H arylation of indoles has been developed with high selectivity at the C2 and C3 positions via transition-metal-catalyzed cross-coupling reactions. Here we show that C–H activation can be directed to the C7 position with high selectivity in Pd-catalyzed coupling of indoles with arylboronic acids. The key to this high regioselectivity is the appropriate choice of a phosphinoyl directing group and a pyridine-type ligand in the presence of Pd(OAc)2 catalyst. This previously elusive transformation should provide insight for the design of other cross-couplings as well.