Asymmetric Synthesis of γ-Hydroxy Pinacolboronates through Copper-Catalyzed Enantioselective Hydroboration of α,β-Unsaturated Aldehydes.

We report a copper-catalyzed enantioselective hydroboration of α,β-unsaturated aldehydes with pinacolborane. α,β-Unsaturated aldehydes were converted to the corresponding γ-pinacolboronate alcohols in good yields and enantioselectivities through consecutive hydroboration of the C═O and C═C bonds. This process provides simple access to the hydroborated product of allylic alcohols, and the resulting γ-pinacolboronate alcohols could be utilized in various transformations.