Structural Variations in Allylic Esters

Samarium iodide promotes this addition reaction. " " In a related reaction, simple alkene units add to esters in the presence of sodium and liquid ammonia to give an alcohol.Structural variations in the alkene lead to different products. Homo-allylic alcohols react with aldehydes in the presence of Montmorillonite KSF clay to give 4-hydroxytetrahydropyrans. " A variation of this reaction converts an aryl aldehyde and a homoallylic alcohol to a 4-chlorotetrahydropyran in the presence of Homoallylic alcohols, protected as —O(CHMeOAc) react with... 

Ester enolates. Oppolzer showed in 1983 that the Z(Gj-dienolate shown in Scheme 5.30a adds to cyclopentenone with 63% diastereoselectivity [160]. Additionally, the enolate adduct can be allylated selectively, thereby affording (after purification) a single stereoisomer having three contiguous stereocenters in 48% yield. The transition structure illustrated is not analogous to any of those illustrated in Scheme 5.29 because cyclopentenone is an s-trans-Z-enone, whereas the enones in Scheme 5.29 are s-cis-E. In 1985, Corey reported the asymmetric Michael addition of the EfOj-enolate of phenylmenthone propionate to -methyl crotonate as shown in Scheme 5.30b [161]. The product mixture was 90% syn, and the syn adducts were produced in a 95 5 ratio, for an overall selectivity of 86% for the illustrated isomer. The transition structure proposed by the authors to account for the observed selectivity is similar to that shown in Scheme 5.29c, but with the enone illustrated in an s-trans conformation. Intramolecular variations of these reactions were reported by Stork in 1986, as illustrated in Scheme 5.30c and 5.29d [162]. Two features of... 

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