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.