Asymmetric nucleophilic epoxidation of chalcone and its derivatives was studied using chiral cyclic guanidine compounds.Pentacyclic guanidine la,which has a characteristic closed-type cavity,catalyzed the reaction to give epoxides with 39-60% ee.The newly developed tricyclic guanidine 4 drastically accelerated the reaction,and induced the asymmetric induction of chalcones with almost the same level of la.
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