pi-Bond Directed C-2 Amination of Indoles: Catalysis Development, Mechanistic Investigation, and Substrate Scope

Cooperative functionalization of N-heterocycles, common motifs present in pharmaceuticals, agrochemicals, functional mate-rials, and natural products, is attractive but a challenging task. In this work, we report a bond directed C2-H functionaliza-tion/amination of indoles with N-heteroarenes in the presence of NiCl2, alternative to Pd-catalysis. Mechanistic studies did not support an oxidative dearomatization, norbornene type C–H functionalization, or allylic C–H activation as likely path-ways and suggest the involvement of Friedel-Crafts type pi-bond directed C–H bond activation as the likely pathway. The methodology is operationally simple, scalable, high yielding and offers a broad scope with high functional group tolerance.