This thesis describes investigations into the use of tandem Prins Friedel-Crafts reactions to prepare the tricyclic core of natural products such as epicalyxin J and calyxin J. Model studies revealed that reaction of homoallylic alcohol 155 with anisaldehyde in the presence of TMSOTf gave the required tandem Prins Friedel-Crafts product 168 in modest yield (25%) along with further products including 172 formed via an oxonia-Cope rearrangement. Efforts to optimise the reaction by varying temperature, solvent and Lewis acid always led to complex mixtures. We propose that the ether oxygen in substrates such as 155 may be linked to the formation of the plethora of products. This hypothesis is supported by results of cyclisation studies with homoallylic acetals 25 and 273; with the phenethyl containing substrate 25 the tricyclic product 26 was isolated in 56% yield whereas with the ether side-chain 273, triflate 274 was the major product. Interestingly reaction of enol ether 300 with TMSOTf gave the novel product 301 which was we propose was formed via a neighbouring group participation of the ester group and cleavage of the methylene carbon-oxygen bond of the ether.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:685153 |
| Date | January 2011 |
| Creators | Cameron, Helen |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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