A series of C 2 symmetric chiral ketones were designed and synthesized for catalytic asymmetric epoxidation of unfunctionalized olefins. Among those ketones screened, (R)-7, (R)-9, and (R)-10 were found to be highly efficient catalysts for epoxidation of trans-stilbenes with enantioselectivities in the range of 84−95%. Convincing evidence was provided for a spiro transition state of dioxirane epoxidation. Through the 18O-labeling experiment, chiral dioxiranes were found to be the intermediates in chiral ketone catalyzed epoxidation reactions.

Perfluoroalkylated heterocyclic phosphonates have been conveniently synthesized by 1,3-dipolar cycloaddition of aromatic nitrile oxides (or ethyl diazoacetate or tert-butyl azidoacetate) and perfluoroalkylated alkynylphosphonates in good to excellent yields with high regioselectivity.A large number of phosphonic acids and their derivatives have been shown to exhibit important biological properties, including antibiotic, antileukaemic and insecticidal activity, depending on the nature of substituent on the phosphonic group.' Introduction of a fluorine atom or perfluoroalkyl group into compounds with biological properties often leads to pronounced activity enhancement, and organofluorine compounds have been applied increasingly in pharmaceuticals, agrichemicals and other fields. Furthermore heterocyclic compounds, particularly fluorine-containing heterocyclic species, play important roles in the fields of medicinal and agricultural ~hemistry.~ Therefore, it is of interest to develop a convenient method for the synthesis of the title compounds since they may be expected to possess biological activity.

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