ISSN:
1573-1111
Keywords:
Asymmetric halogenation
;
hydrohalogenation
;
styrene
;
cyclodextrincomplex
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
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 α- and β-cyclodextrin complexes produced predominantly (−)-1,2-dibromo-l-phenylethane. The chiral induction for the reaction of the α-cyclodextrin complex rose to 9 times that of the β-cyclodextrin complex. Brominations in the homogenous solutions containing the α- or β-cyclodextrin complexes gave no dibromide but racemic bromohydrin. In the gas-solid chlorination, the α-cyclodextrin complex gave (−)-dichloride,S-(+)-2-chloro-l-phenylethanol (14% ee) and (+)-1,2,2-trichloro-l-phenylethane, and the β-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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00664102
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