Coupling homogeneous catalysts to dendrimers with rigid nuclei is one possible strategy to recycle
these compounds in an industrial environment. During this study attempts were made to attach the
well-defined ruthenium carbene complex 2 to the alicyclic compound 1A. To achieve this goal
attempts were made to functionalise 1A with anime groups to facilitate the attachment of
phosphine groups. The catalyst 2 would then be attached through a phosphine exchange reaction.
Oximes were used as precursors in attempts to prepare cage amines from 1A. For this purpose,
the dioxime 28 was prepared from 1A. Reduction of 28 was unsuccessful. Molecular modelling
showed that the lobes of the LUMOs of the oxime carbon atoms of 28 do not protrude from the
total electron density of this molecule. This observation indicates that 28 would probably not react
with nucleophiles, such as the hydride ion. Molecular modelling was used to probe the unreactive
nature of oxime 28. The probe revealed that the imide ring deactivates the oxime groups in this
compound.
Based on these results, attempts were made to change the carbon framework of 1A to eliminate
unwanted interaction between the carbonyl groups. Clemmensen reduction of 1A did not yield the
expected ketol 40, but gave a mixture of 62 and 63. Extended reaction times yielded 63 only.
Reduction of 1A with zinc and acetic acid produced a mixture of 62 and 40 that could not be
separated. Consequently, the applicability of 62 as a possible dendrimer nucleus was investigated.
Compound 62 was obtained by oxidisation of the diol 63 with sodium periodate. Attempts to
synthesise the dioxime 69 from 62 failed and only the mono oxime 71 was obtained.
Reduction of 71 with lithium aluminium hydride was unsuccessful. Molecular modelling revealed
that the oxime carbon atom does not have a LUMO and that the carbonyl carbon atom would
probably be unreactive towards nucleophiles. Several other attempts were made at reducing the
oxime 71 to an amine. None of these attempts met with any success. The reason for the
unreactive nature of 71 is less clear than in the case of 28.
Failure to produce a cage amine from 1A or derivatives of 1A meant failure in functionalising the
cage system with phosphine groups and coupling the Grubbs-I catalyst. It seems that cage compounds based on 1A are generally not suitable as starting materials for amine-functionalised
dendrimer nuclei. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011.
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/4393 |
| Date | January 2010 |
| Creators | Liebenberg, Deseré |
| Publisher | North-West University |
| Source Sets | North-West University |
| Detected Language | English |
| Type | Thesis |
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