Bond Dissociation Energy-Controlled Regioselectivity in Hydrofunctionalization

The bond dissociation energy (BDE) in reactants was found to be critical for determining the tunable pathways of low-valent tungsten-catalyzed chain-walking hydroboration and hydrogermylation of β,γ-unsaturated amides, which is considered to be the key factor in the regioselective determination. Computational results revealed that the higher BDE of the H–B bond hampers the oxidative hydrogen migration, leading to borane reacting with tungsten later than alkenes. Thus, the generation of a β-borylated product was found to be favorable through H–Cβ bond oxidative addition, H–Cδ bond reductive elimination, H–B bond oxidative hydrogen migration, and B–Cβ bond reductive elimination. As a comparison, the lower BDE of H–Ge leads to a facile oxidative hydrogen migration of the H–Ge bond, which finally results in the formation of an α-germylated product after germyl-assisted olefin walking. Further distortion–interaction analysis confirmed that the weak H–Ge bond was easier to distort for its reactions.