David J. Willock

Designing templates for the synthesis of microporous solids using de novo molecular design methods

De novo design techniques are used to grow (computationally) candidate template molecules for specific microporous materials. Detailed studies are reported for both EU-1 and chabazite where our simulations are able to rationalise known templates and suggest new templating molecules for the synthesis of such structures.

Heterogeneous enantioselective dehydration of butan-2-ol

Abstract Zeolite Y modified with chiral sulfoxides has been found catalytically to dehydrate racemic butan-2-ol enantioselectively depending on the chiral modifier used. Zeolite Y modified with R -1,3-dithiane-1-oxide shows a higher selectivity towards conversion of S -butan-2-ol and the zeolite modified with S -2-phenyl-3-dithiane-1-oxide reacts preferentially with R -butan-2-ol. Zeolite Y modified with dithiane oxide demonstrates a significantly higher catalytic activity when compared to the unmodified zeolite. Computational simulations are described and a model for the catalytic site is discussed.

Enantioselection using modified zeolite catalysts

Abstract The proton form of zeolite Y was modified with R -1,3-dithiane-1-oxide at a loading 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 − and that for the R -enantiomer is 48.3 kJ mol − . This difference in the adsorption of the two enantiomers is considered to be the origin of the enhanced reactivity of the S -enantiomer.

Creating chiral centres 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 enantioner. Thus a heterogeneous enantioselective catalyst has been produced by the introduction of a chiral modifier into an achiral zeolite. The modifier remains stable at temperatures of up to at least 180°C. In this paper we present results of computer simulation work on this system which suggest that the observed stability of the R-1,3-dithiane 1-oxide in the zeolite is due to proton transfer between the zeolite and the molecule. We suggest that the molecule is present as a counter cation to the framework. A combination of energy minimisation, Monte Carlo and molecular dynamics techniques are used to study the zeolite Y and R-1,3-dithiane 1-oxide system. Consistent force field potentials are used to describe both the zeolite framework and the adsorbed molecule.

Gas-phase catalytic asymmetric reaction using chirally modified microporous catalysts

The first example of an enantioselective gas-phase reaction heterogeneously catalysed by a zeolite is demonstrated using as catalyst a zeolito modified with a non-racemic chiral mediator.