Asymmetric halogenation and hydrohalogenation of styrene in crystalline cyclodextrin complexes |
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Authors: | Hidetake Sakuraba Hirokazu Ishizaki Yoshio Tanaka Toshimi Shimizu |
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Affiliation: | (1) Department of Industrial Chemistry, Faculty of Engineering, Kanto Gakuin University, 4834 Kanazawa-Mutsuura, 236 Yokohama, Kanagawa, Japan;(2) Research Institute for Polymers & Textiles, 1-1-4 Yatabe-Higashi, 305 Tsukuba, Ibaraki, Japan |
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Abstract: | Asymmetric halogenation and hydrohalogenation of styrene in microcrystalline cyclodextrin complexes were studied in the gas-solid state, and compared with the homogenous reactions in aqueous or dimethyl sulfoxide solutions. The gas-solid brominations in the - and -cyclodextrin complexes produced predominantly (–)-1,2-dibromo-l-phenylethane. The chiral induction for the reaction of the -cyclodextrin complex rose to 9 times that of the -cyclodextrin complex. Brominations in the homogenous solutions containing the - or -cyclodextrin complexes gave no dibromide but racemic bromohydrin. In the gas-solid chlorination, the -cyclodextrin complex gave (–)-dichloride,S-(+)-2-chloro-l-phenylethanol (14% ee) and (+)-1,2,2-trichloro-l-phenylethane, and the -cyclodextrin complex produced (+)-dichloride,S-(+)-chlorohydrin (8% ee) and (+)-trichloride. The chiral induction of the gas-solid halogenation using the solid cyclodextrin complexes is attributed to the ability to hold rigidly a chiral conformation of the crystalline state. However, the gas-solid hydrohalogenation all gave racemic products.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986. |
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Keywords: | Asymmetric halogenation hydrohalogenation styrene cyclodextrincomplex |
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