UBC Theses and Dissertations
Catalyst and methodology development for regioselective C-N and C-C bond formation Lee, Alison Victoria
The related investigations of catalytic hydroamination as a key step in synthetic methodology development and the synthesis of new hydroamination catalysts are reported in this thesis. The first section focuses on methodology development for the application of a bis(amidate)bis(amido) titanium hydroamination precatalyst towards the synthesis of functionalized small molecules via a tandem C-N, C-C bond forming reaction sequence. The development of two tandem sequential reactions will be described, as well as their applications in the synthesis of α-cyanoamines, α-amino acid derivatives, β-amino alcohols, diamines, imidazolidinones, and β-amino acid derivatives. These tandem reactions show an expanded substrate scope and increase synthetic flexibility by allowing for alternative starting materials in the preparation of highly functionalized small molecules. The second section describes progress towards the development of an asymmetric tandem reaction sequence, including investigations into the mode of activation for the tandem reaction. It has been established that a nucleophilic activation mode is required to generate an active species for the C-C bond forming step. Furthermore, it is postulated that the coordination environment and steric congestion about the activator impacts reaction efficiency and stereoselectivity. This information will be valuable in the design of future generations of activators. The final section reports the development of two novel group 4 metal complexes for catalytic hydroamination. The synthesis and full characterization of these complexes will be described, as well as the results of the catalytic investigations. Through this investigation it has been postulated that while a change in the electronic nature of the metal complex does enhance catalytic reactivity, the degree of orbital overlap between the ligand and the metal center is also an important consideration in the design of electrophilic hydroamination precatalysts. Hydroamination catalysis is currently an attractive area of intense research. The work in this thesis has demonstrated the use of hydroamination catalysis in the synthesis of highly functionalized small molecules, and has furthered the fundamental understanding of the hydroamination reaction. This increase in understanding can then be applied towards the rational design of more powerful hydroamination catalysts and further their application in the synthesis of functionalized N-containing compounds.
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