Asymmetric Diels-Alder reactions of chiral (E)-2-cyanocinnamates with cyclopentadiene
作者:Carlos Cativiela、Jose A. Mayoral、Alberto Avenoza、Jesus M. Peregrina、Fernando J. Lahoz、Sergio Gimeno
DOI:10.1021/jo00043a025
日期:1992.8
Several chiral derivatives of (E)-2-cyanocinnamic acid are used as trisubstituted dienophiles, and their asymmetric Diels-Alder reactions with cyclopentadiene are studied. The reactions of (E)-2-cyanocinnamates of (S)-ethyl lactate and (R)-pantolactone with cyclopentadiene, catalyzed by TiCl4, allow the synthesis of enantiomerically pure cycloadducts whose absolute configurations are assigned by an X-ray diffraction study of enantiomerically pure (1S,2S,3R,4R,5R,6R)-iodolactone. The results obtained show that the alpha-cyano group influences asymmetric induction, probably through an influence on the s-cis/s-trans equilibrium of the enoate moiety of the chiral dienophile.