Copper(I)-Catalyzed Enantioselective Synthesis of α‑Chiral Linear or Carbocyclic (E)‑(γ-Alkoxyallyl)boronates

A new method has been developed for the catalytic asymmetric synthesis of α-chiral linear or carbocyclic (γ-alkoxyallyl)­boronates via the copper­(I)-catalyzed γ-boryl substitution of allyl acetals. This reaction afforded the products in high yields with excellent E:Z selectivities and enantioselectivities [only (E)-product, 91–98% ee] and also exhibited high functional group compatibility. Subsequent allylation of aldehydes with the α-chiral (γ-alkoxyallyl)­boronates provided the anti-1,2-diol derivatives in a highly stereospecific manner, and the utility of the α-chiral (γ-alkoxyallyl)­boronates was further demonstrated by a convergent coupling of a complex polyol derivative using a (γ-alkoxyallyl)­boronate and a chiral α-oxyaldehyde. The stereoselective modular construction of a complex 3,3-disubstituted cyclopentene containing three consecutive stereocenters including a quaternary chiral carbon was also reported. Useful transformations of the α-chiral linear (γ-alkoxyallyl)­boronates were also demonstrated.