Overlooked Ligand Role of Pyridine Substrate in Site Selectivity of Rare-Earth-Catalyzed C–H Alkylation with Alkenes

The rare-earth-catalyzed C-H alkylation of heteroatom-containing substrates with alkenes has been extensively studied over the past decade. Traditionally, those substrates have been regarded primarily as reactants in these reactions. In this study, the mechanism of rare-earth-catalyzed C-H alkylation of 2-ethylpyridine with styrene was investigated by DFT calculations, revealing the often-overlooked ligand effect of pyridine substrates. Our findings demonstrate that pyridine substrates, acting as ligands, play a pivotal role in modulating site selectivity during C-H activation. These results enhance our understanding of the rare-earth catalysis mechanism and provide valuable insights into its versatile reactivity, offering a novel perspective on the dual roles (both reactant and ligand) of heteroatom-containing substrates, which are widely used in C-H functionalization reactions.