CREATING CHIRAL CENTERS IN ZEOLITE-Y BY THE INTRODUCTION OF R-1,3-DITHIANE 1-OXIDE AS A MODIFIER - COMPUTER-SIMULATION OF THE MODIFIER STABILITY

In an earlier paper we have shown that R-1,3-dithiane 1-oxide adsorbed in zeolite Y is able to dehydrate the S enantiomer of butan-2-ol at a rate of up to 19 times greater than the R enantiomer. Thus a heteroge neous enantioselective catalyst has been produced by the introduction of a chiral modifier into an achiral zeolite. The modifier remains sta ble at temperatures of up to at least 180 degrees C. In this paper we present results of computer simulation work on this system which sugge st that the observed stability of the R-1,3-dithiane 1-oxide in the ze olite is due to proton transfer between the zeolite and the molecule. We suggest that the molecule is present as a counter cation to the fra mework. A combination of energy minimisation, Monte Carlo and molecula r dynamics techniques are used to study the zeolite Y and R-1,3-dithia ne 1-oxide system. Consistent force field potentials are used to descr ibe both the zeolite framework and the adsorbed molecule.