Bifunctional NHC-Promoted C2-Alkylation of Pyridine via Ni–Al Bimetallic-Catalyzed Hydroarylation of Unactivated Alkenes

Abstract

Achieving site-selective alkylation with pyridine under transition metal catalysis has remained a long-standing challenge, especially when using unactivated alkene as an alkylating reagent. We herein describe a site-selective C2-alkylation of pyridine under Ni–Al bimetallic catalysis and directing bifunctional N-heterocyclic carbene (NHC) as ligand through hydroarylation of unactivated alkenes. A broad range of C2-alkylated pyridines with various functionalities could be prepared in high efficiency (up to 99% yield) and high C2-selectivity, and the scope of heterocycles is not limited to pyridines but can be expanded to other azines like pyrazines and pyrimidines. Mechanistic studies suggest that a bifunctional NHC–Ni–Al–pyridine complex is responsible for high site selectivity control and that reductive elimination might be the rate-determining step.