Hydrophobic/hydrophilic effects on the titanium(IV)-catalyzed epoxidation of cyclohexene by tert-alkyl hydroperoxides: 2-methyl-1-phenyl-2-propyl hydroperoxide (MPPH) versus tert-butyl hydroperoxide (TBHP)

The epoxidation of cyclohexene in acetonitrile under argon at room temperature on a titanium(IV)-containing MCM41 silica catalyst is faster and gives a greater final yield of cyclohexene oxide when the oxygen atom donor is 2-methyl-1-phenyl-2-propyl hydroperoxide (MPPH) than when it is tert-butyl hydroperoxide. This is shown to be due to stronger retardation of the oxidation by tert-butyl alcohol (TBA) than by the alcohol derived from MPPH. The difference in retardation between these two alcohols is attributed to the greater hydrophilicity of TBA. Acetonitrile is a better solvent for this reaction than isooctane, pyridine and a variety of alcohols. These solvent effects are attributed to the hydrophilic nature of the catalyst.