Enantioselection using modified zeolite catalysts

The proton form of zeolite Y was modified with R-1,3-dithiane-1-oxide at a lending of one molecule per supercage to create a chiral acid catalyst. The enantiomeric discrimination of this catalyst was demonstrated using the dehydration of the separate enantiomers of butan-2-ol and over the temperature range investigated the S-enantiomer was always more reactive. This catalyst system was then studied using computational simulation methods. The lowest energy structures for the enantiomers of butan-2-ol docked into a model of the modified zeolite were calculated and it was found that the binding energy for the S-enantiomer is 64.7 kJ mol(-1) and that for the R-enantiomer is 48.3 kJ mol(-1). This difference in the adsorption of the two enantiomers is considered to be the origin of the enhanced reactivity of the S-enantiomer.