Catalyzed Asymmetric S_E′ Addition of Allylstannanes to Aldehydes

Abstract

Addition of achiral allylstannanes to achiral aldehydes in the presence of Yamamoto's chiral (acyloxy)borane catalyst (III) and trifluoroacetic anhydride affords homoallylic alcohols with high diastereo- and enantioselectivity. For example, crotonoaldehyde (1c) and (E)-tributyl(2-methyl-2-pentenyl)stannane (2) gave (3S,4S,5E)-3-ethyl-2-methyl-1,5-heptadien-4-ol (3c) in 85% yield and 95% enantiomeric excess.