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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:555537 |
| Date | January 2012 |
| Creators | Collins, Karl Daniel |
| Contributors | avid |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/the-development-and-application-of-radical-and-anionic-cyclisations-mediated-by-samariumii-diodide-and-protic-cosolvents(0e807a8c-d40f-45bb-8d83-26e79ebe9388).html |
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