Modification of chemical reactivity upon cyclodextrin encapsulation:
摘要:
Asymmetric bromination of chalcone and benzylideneacetone (trans-isomers) in crystalline beta-cyclodextrin complex was studied. While bromination of chalcone in the absence of beta-cyclodextrin yields erythro-dibromide, bromination of beta-cyclodextrin-chalcone complex results in the formation of a mixture of erythro- and threo-dibromides respectively in the ratio 80:20. Complexation does not induce any variation in the bromination pattern in the case of trans-benzylideneacetone. These observations have been accounted for in terms of different conformations of the enones in the beta-cyclodextrin-enone complexes. Complex formation between the substrate and cyclodextrin has been confirmed by various physical methods.