Palladium-Catalyzed Direct 2-Alkylation of Indoles by Norbornene-Mediated Regioselective Cascade C-H Activation

A palladium-catalyzed direct 2-alkylation reaction of free N-H indoles has been developed. This reaction relies on a norbornene-mediated cascade C-H activation process at the indole ring, which features high regioselectivity and excellent functional group, tolerance. The reaction represents the first example for a generally applicable, direct C-H alkylation of indole at the 2-position.