In our effort to search for Ca symmetric and conformationally rigid chiral
ketones as catalysts for asymmetric epoxidation, a series of cyclic ketones
4-10 were prepared from the corresponding diacids. Compared with acyclic k
etones for epoxidation of trans-stilbene, those 9-, 10-, and 11-membered-ri
ng cyclic ketones were found to have much higher catalytic activities, whic
h were attributed to steric effects, electronic effects, and ring strains.
By using the homogeneous acetonitrile-water solvent system, unfunctionalize
d olefins with various substitution patterns (with 5 mol % of ketone 9) and
strongly electron-deficient olefins (with a 1:1 ketone 9:substrate ratio)
were epoxidized with Oxone as terminal oxidant in 75-96% yield at room temp
erature and neutral pH. In addition, oxidation of alcohols (with 20 mol % o
f ketone 9) was carried out successfully with good isolated yields of aldeh
ydes or ketones (75-88%).