| Autor: |
SAKURABA, HIDETAKE, ISHIZAKI, HIROKAZU, NAKAI, TOSHIMORI, TANAKA, YOSHIO |
| Zdroj: |
Journal of Inclusion Phenomena & Molecular Recognition in Chemistry; Apr1997, Vol. 27 Issue 4, p341-348, 8p |
| Abstrakt: |
Asymmetric solid–gas hydrohalogenation of styrene, β-methylstyrene,allylbenzene, and 2-norbornene as unfunctionalized olefins was carried out by using theirchiral crystalline α- and β-cyclodextrin complexes by exposing them to gaseous HCl and HBrin the dark at room temperature. The optical purities of the Markovnikov products obtainedfrom the ionic addition of HCl to the included olefins appear considerably higher than thosefrom the reaction with HBr. The highest enantioselectivities of 58% and 62% enantiomericexcess (ee) were obtained for the hydrochlorination of 3-phenyl-1-propene (allylbenzene) inthe crystalline α- and β-cyclodextrin complexes, respectively, and both reactions, which hadlittle danger of racemization, gave (S)-(+)-2-chloro-1-phenylpropane as the same predominantproduct in moderate chemical yields. A much lower enantioselectivity (<10% ee) wasobserved in the hydrobromination of the same olefin in the solid α- and β-cyclodextrincomplexes involving a racemization reaction. The enantiofacial selection provided the (S)-enantiomer similarly during hydrochlorination. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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