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New and efficient strategies in stereoselective heterocycle synthesis.

Sandon, Nicolas (2009) New and efficient strategies in stereoselective heterocycle synthesis. PhD thesis, University of Sheffield.

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This thesis describes the development and the application of three different [3+3] annelation strategies for the formation of functionalised piperidines. Initially, the scope of the [3+3] cycloaddition reaction of Pd-trimethylenemethane and aziridines towards functionalised piperidines was investigated for its application to silyl ether substituted aziridines. These substrates appeared to be very challenging, undergoing the cycloaddition only under very rigorous conditions. Since this methodology was not trivial to repeat, a two-step strategy was explored that involved the addition of a Grignard reagent to the aziridines followed by ringclosure to the corresponding piperidines. These two procedures were found to be enantiospecific, providing good routes for the synthesis of enantiopure piperidines. The functionalisation of the exo-alkene group of these piperidines was also investigated with particular regard to the reaction diastereoselectivity. A third [3+3] annelation reaction towards the synthesis of the piperidine core has also been employed, which invoked the addition of the Bilchi Grignard reagent to the enantiopure silyl ether substituted aziridine (R)-139 to provide the corresponding acetal 263 in good yield. Acid catalysed cyclisation of the acetal produced the corresponding enantiopure tetrahydropyridine 264. The last section of this work focused on the applicability of these methods for the synthesis of natural products and highlights our attempts towards the synthesis of quinolizidine alkaloid (-)217A.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Chemistry (Sheffield)
Identification Number/EthosID: uk.bl.ethos.500173
Depositing User: EThOS Import Sheffield
Date Deposited: 02 Dec 2016 15:16
Last Modified: 02 Dec 2016 15:16
URI: http://etheses.whiterose.ac.uk/id/eprint/15106

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