Abstract
For a long time chiral silicates remained elusive due to the Berry pseudorotation. In order to
synthesize these silicates, the corresponding silanes have to be produced. Recently, a new
synthetic route for the asymmetrical synthesis of silanes was reported by Kuninobu et al.,
where a rhodium catalyst with a chiral ligand was used to obtain higher ee values. The
importance for obtaining higher ee values is because these pentaorganosilicates possess
chirality, making them prone to racemization because of the Berry pseudorotation. Previous
reports show that the Berry pseudorotation can be inhibited through steric hindrance and by
introducing a strong electronegative monodentate group, resulting in configurationally stable
chiral silicates. The synthesis for racemic spirosilanes already existed, but the synthesis is less
favorable than the one adapted by Kuninobu et al. because of asymmetric purposes. The first
aim of the research was to obtain three spirosilanes, all with different substituents, and to
observe if they are adequate to inhibit the berry pseudorotation. Unfortunately, there was not
enough time to synthesize two of these spirosilanes. However, the spirosilane with the
substituent 2-phenylbenzo[b]thiophene was successfully synthesized. A second aim of this
research was to investigate if it was possible to get a better separation of the successfully
synthesized spirosilane, by varying the concentration of the rhodium catalyst and chiral ligand
(R)-(-)-DTBM SEGPHOS. At the same time the ee value would be determined for various
concentrations and the best concentrations for a better separation would be determined.
Furthermore, a second chiral ligand (R)-(+)-SEGPHOS was used in a rhodium catalyzed reaction
with the concentration which had the best separation, in this case being the highest
concentration of rhodium catalyst and chiral ligand. For the reaction with the chiral ligand (R)(+)-SEGPHOS a lower %ee of 27 was observed compared to the chiral ligand (R)-(-)-DTBM
SEGPHOS which had an %ee of 55. However, a significantly higher isolated yield could be
obtained using (R)-(+)-SEGPHOS.