Epoxidation of olefins was carried with an excellent yield by dioxiranes generated in situ by reaction of ketone with H 2O 2 in the presence of NaHCO 3 in mixed solvent of acetonitrile and water. The catalytic activity of various ketones on epoxidation was studied for the first time. It is found that the ketone with electron withdrawing group has an excellent catalytic activity and trifluromethyl ketone has the highest catalytic activity. Some bulky ketones with electron withdrawing group show a very low catalytic activity. For olefins, the electron withdrawing group decreased the reactivity of the olefin and the electron donating group increased the reactivity, but the steric factor has little effect on the reactivity of olefins.
Asymmetric epoxidation of olefins with oxone was first catalyzed by chiral iminium salts generated in situ from chiral amines and aldehydes. With 2S,5S-2,5-dicyclohexylaminocarbonylpyrolidine and t-butylacetaldehyde, trans-stilbene were epoxdized in 80% conversion, 93% yield and 65% e.e. at 0 ℃.
The polymerization of styrene was initiated by calixarene neodymium/di n butylmagnesium/hexamethylphosphoramide catalyst system. The average viscosity molecular weight of polystyrene increases as the concentration of di n butylmagnesium or the Mg/Al molar ratio in the di n butylmagnesium increases. This result was explained by the state of association of butylmagnesium. As the state of association of di n butylmagnesium increases, the average viscosity molecular weight of polystyrene increases. [WT5HZ]
