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 alpha-chiral linear or carbocyclic (gamma-alkoxyallyl)boronates via the copper(I)-catalyzed gamma-boryl substitution of allyl acetals. This reaction afforded the products in high yields with excellent E:Z selectivities and enantioselectivities [only (E)-product, 9198% ee] and also exhibited high functional group compatibility. Subsequent allylation of aldehydes with the alpha-chiral (gamma-alkoxyallyl)boronates provided the anti-1,2-diol derivatives in a highly stereospecific manner, and the utility of the alpha-chiral (gamma-alkoxyallyl)boronates was further demonstrated by a convergent coupling of a complex polyol derivative using a (gamma-alkoxyallyl)boronate and a chiral alpha-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 alpha-chiral linear (gamma-alkoxyallyl)boronates were also demonstrated.