Journal of the American Chemical Society, Vol.122, No.7, 1310-1313, 2000
New and stereoselective synthesis of 1,4-disubstituted buten-4-ols (homoallylic alcohol alpha-adducts) from the corresponding gamma-isomers (3,4-disubstituted buten-4-ols) via an acid-catalyzed allyl-transfer reaction with aldehydes
The gamma-adducts of homoallylic alcohols 3, derived from aldehydes via the usual reaction with common allylic metals I. were convened to the corresponding alpha-adducts 6 by an acid-catalyzed allyl-transfer reaction. In the allyl-transfer reaction, anti- and syn-gamma-adducts 3 gave E- and Z-alpha-adducts 6, respectively, and the optical purity of the gamma-adducts 3 was transferred to the alpha-adducts 6 with >98%ee. This suggests that the allyl-transfer reaction proceeds stereoselectively via six-membered cyclic transition states [T]. The reaction was catalyzed by various metal triflates as well as Lewis acids and Bronsted acids.