Aluminium triflate as catalyst for epoxide ring-opening and esterification reactions - Mechanistic aspects

Al(CF3SO3)(3) is a highly effective catalyst for the ring opening of epoxides with methanol, as well as for the esterification of carboxylic acids with alcohols. Factors that influence the rate of the ring opening of butene oxide with methanol and the esterification of acetic acid with n-propanol and ethanol were investigated. It was found that low concentrations (e.g., similar to 5 ppm) of Al(CF3SO3)(3) catalyze the ring-opening reactions, whereas considerably higher concentrations are required for esterification reactions. Molecular modeling studies suggest that these differences can be rationalized in terms of the formation energies of the active intermediates of these reactions.