Olefin metathesis is a powerful tool for assembly of carbon-carbon bonds. Amines and related N-donors are problematic functional groups in Ru-catalyzed olefin metathesis - a well- documented, but poorly understood problem.
The first part of this thesis focuses on amine-induced deactivation pathways; two of which are described in depth. Alkylidene abstraction, a previously unknown reaction for nitrogen nucleophiles, was observed for smaller and less Bronsted-basic amines. Deprotonation of the metallacyclobutane intermediate formed during catalysis is prominent for highly Bronsted basic or sterically bulky N-donors. Monosubstituted (and, by extension unsubstituted) metallacyclobutanes are particularly vulnerable to deprotonation.
For each pathway, the fate of the alkylidene Ru=CHR functional group proved key in determining the nature of deactivation. Both pathways have been detected during catalysis, as evidenced by formation of diagnostic amine (RCH2NR2’) or substituted propene products. A combination of quantitative NMR and GC-MS analysis was used to identify these species on loss of the Ru-alkylidene functional group.
The second part of this thesis focuses on incorporating amines into catalyst design – an under-utilized strategy in the context of Ru-catalyzed olefin metathesis. A modified Grubbs-type catalyst was developed featuring a bulky, relatively non-basic biaryldiamine ligand. Metathesis activity for this catalyst was comparable, and in some cases superior to the most widely-used homogeneous catalysts currently available. Several new, related Ru-benzylidenes were also prepared and fully characterized in conjunction with the mechanistic studies described above.
Progress toward development of N-anion-containing metathesis catalysts is also discussed. Synthesis of Ru-hydride complexes originally intended for this purpose allowed for a fundamental study of the coordination chemistry and reductive elimination chemistry of the NPh2– anion.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/34342 |
| Date | January 2016 |
| Creators | Ireland, Benjamin |
| Contributors | Fogg, Deryn E. |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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