Catalytic Asymmetric Coupling of Borylallene and Ketones: Rapid Access to Enantioenriched ( Z )- or ( E )-δ-Boryl-Substituted Tertiary Homoallylic Alcohols

Abstract Enantioselective synthesis of (Z)- and (E)-δ-boryl tertiary homoallylic alcohols is developed. Cu-catalyzed asymmetric reductive coupling between borylallene and ketones gave enantioenriched (Z)-δ-boryl-substituted tertiary homoallylic alcohols. By using a Pd-catalyzed alkene isomerization approach, (E)-δ-boryl-substituted tertiary homoallylic alcohols were also obtained from the corresponding Z-isomers.