Ruthenium-Catalyzed Regioselective Migratory Hydroacylation of Nonactivated Allenes with Alcohols Enabled by 1,4-Ru/H Migration

1,4-Metal/hydrogen migration is a flexible strategy that not only activates remote C–H bonds but also mediates regioselective coupling reactions. We describe here an intermolecular coupling between allenes and alcohols to access β,γ-unsaturated ketones via tandem ruthenium catalysis. The reaction occurs via migratory hydroacylation of allenes with an in situ-generated aldehyde through the dehydrogenation of the alcohols. This formal dual C–H functionalization reaction enables one-step efficient synthesis of β,γ-unsaturated ketones from nonchelating alcohols using a commercially available catalyst and reagent. Unusual β-regioselectivity has been achieved with C–C coupling at the central sp-hybridized carbon of allenes. Moreover, β-regioselective migratory hydroacylation of allenes with nonchelating aldehydes has also been disclosed. The detailed mechanism has been proposed based on the control experimental and computational studies involving hydrogen transfer catalysis and key 1,4-ruthenium hydrogen migration.