Chiral SPINOL‐derived Boro‐phosphate‐Catalyzed Asymmetric 1,4‐Reduction of Exocyclic α,β‐Unsaturated Ketones

An asymmetric 1,4‐reduction of exocyclic α,β‐unsaturated ketones leading to the formation of diverse optically active α‐substituted tetralones has been realized by chiral SPINOL‐derived boro‐phosphate. The enantios‐elctivity‐determining step of the reaction is the protonation of a highly active boron enolates intermediate. The catalytic reduction system composed of chiral SPINOL‐derived boro‐phosphate and pinacolborane may be widely used in other asymmetric reduction reactions.