Nickel-Catalyzed Heteroaromatic C–H Alkylation via Ligand-to-Ligand Hydrogen Transfer

Regio- and enantioselective functionalization of heteroarene C–H bonds in the absence of directing groups is a long-standing challenge in the field of C–H activation. Herein, we present an approach involving nickel-catalyzed intermolecular enantioselective C–H alkylation of heteroarenes. The process can be carried out under mild conditions using nickel(0) catalysts with N-heterocyclic carbene (NHC) ligands in the absence of Lewis acid co-catalysts. A series of NHC nickel complexes stabilized with 1,5-hexadiene were synthesized via an operationally simple approach, resulting in improved functional group tolerance and a wide substrate scope. Mechanistic investigations indicate that the transformation involves a ligand-to-ligand hydrogen transfer (LLHT) pathway where the C–H bond activation precedes a rate-determining reductive elimination step.