Novel cyclic ketones for catalytic oxidation reactions

Abstract

In our effort to search for C2 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 ketones for epoxidation of trans-stilbene, those 9-, 10-, and 11- membered-ring cyclic ketones were found to have much higher catalytic activities, which were attributed to steric effects, electronic effects, and ring strains. By using the homogeneous acetonitrile-water solvent system, unfunctionalized 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 temperature and neutral pH. In addition, oxidation of alcohols (with 20 mol % of ketone 9) was carried out successfully with good isolated yields of aldehydes or ketones (75-88%).