D. A. Evans [2, 3-Sigmatropic Rearrangements: Olefin Geometry Chem 206 a Trisubstituted olefins via [ 2, 3-rearrangemen An elegant squalene synthesis Ollis, Chem. Commun 1969, 99 日)pah R For study on this [2, 3]rxn See [2, 3 heat Baldwin (Z)-path One might project that the(E) path will be moderately favored with selectivity depending on size difference between rl& RM n-BuLi Li Rautenstrauch. Helv. Chim Acta 1971. 54. 739 This nxn is probably not as [2, 3 For related 2,3 rxns stereoselective as advertised Baldwin JACS 1969. 91. 3646 (E(z)=32 Me sP 140° NMe2 rave one major product in high yield OM Buchi JACS 1974. 96 5563 NMe2 poorly selectiveMe Me Me Me Me Me Me Me Me Me Me Me Me Me Me Me SPh X Y: RM RL Me Me Me OH S Me Me Me Me Me H OMe OMe NMe2 n-BuLi H X Y RM H RL H RL Y X RM H O Me Me Me C: NMe2 Me Me Me Me S Me Li Me Me Me Me Me SLi O Me Me NMe2 Me RM RL :X Y Y :X RL RM Me S Me Me Me Ph Me Me Me Me Me Me Me Me Me Me S Me Me S Me Me Me Me S Me Me Me Me S Me Me Me Me S Me Me Me Me F MgBr This rxn is probably not as stereoselective as advertised poorly selective 140 °C Buchi, JACS 1974, 96, 5563 Rautenstrauch, Helv. Chim Acta 1971, 54, 739 (E):(Z) = 3:2 For related [2,3] rxns See Baldwin JACS 1968, 90, 4758 Baldwin JACS 1969, 91, 3646 For study on this [2,3] rxn See Baldwin JACS 1971, 93, 6307 Squalene Li/NH3 "gave one major product in high yield" [2,3] – + benzyne heat PPh3 ® S=PPh3 An elegant squalene synthesis Ollis, Chem. Commun 1969, 99 [2,3] (RL = large) ■ Trisubstituted olefins via [2,3]-rearrangement: One might project that the (E) path will be moderately favored with selectivity depending on size difference between RL & RM (Z)-path (E)-path ‡ ‡ D. A. Evans [2,3]-Sigmatropic Rearrangements: Olefin Geometry Chem 206