Regio‐ and Diastereoselective Copper(I)‐Catalyzed Allylic Substitution of δ‐Hydroxy Allylic Chlorides by a Silicon Nucleophile

A perfectly γ‐selective copper(I)‐catalyzed allylic substitution of protected δ‐hydroxy allylic chlorides with a silicon nucleophile generated by Si–B bond activation provides diastereoselective access to β‐hydroxy α‐chiral allylic silanes with an anti relative configuration. The high levels of diastereocontrol of this rare allylic displacement are interpreted according to a model suggested by Nakamura where diastereofacial selectivity originates from steric control rather than an oxygen‐directing effect in the Felkin–Anh transition state.