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Title: The development and application of radical and anionic cyclisations mediated by samarium(II) diodide and protic co-solvents
Author: Collins, Karl Daniel
ISNI:       0000 0004 2723 5344
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2012
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The development of selective SmI2-H2O-mediated mono-reductions of cyclic-1,3-diesters to the corresponding 3-hydroxy acids is described. The reaction proceeds with complete selectivity for cyclic-1,3-diesters over acyclic esters. Sequential one-pot conjugate reduction-ester reduction of alkylidene cyclic-1,3-diesters is also reported. Furthermore, we describe the exploitation of the unusual ketyl radical intermediates formed via single electron reduction of the ester carbonyl in unprecedented 5-exo-trig cyclisations providing access to highly substituted, stereo-defined, cyclopentanols and cyclopentanones. Also described is the use of a silicon control element to direct the stereochemical outcome of the SmI2-MeOH-mediated conjugate reduction-intramolecular aldol cyclisations of α,β-unsaturated lactones. These cyclisations generate two contiguous quaternary centres with complete diastereocontrol; the utility of the silicon-directing group as a synthetic handle for derivatisation of the cyclisation products has also been demonstrated. These cyclisations have been applied in a model approach to the anti-mitotic natural product pseudolaric acid B.
Supervisor: avid. Sponsor: EPSRC ; AstraZeneca
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Samarium ; 5-exo-trir ; radicals ; SmI2 ; pseudolaric acid ; conjugate reduction ; aldol cyclisation ; lactone reduction ; Meldrum's acid