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Title: Samarium(II) mediated radical cascades of keto esters for the generation of molecular complexity
Author: Plesniak, Mateusz
ISNI:       0000 0004 7429 7513
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2018
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A highly regio- and diastereoselective approach towards complex 6-membered lactones was developed using allyl/propargyl benzyl ethers and delta keto esters. Crucially, the classical ET reagent SmI2 gave unsatisfactory results and it was necessary to develop and screen new Sm(II) cyclopentadienyl complexes to deliver high selectivity in the transformation. The methodology was extended to a one-pot approach to complex cycloheptanols using SmI2-H2O in a second stage of the process. Samarium(II) folding cascades were developed where simple, linear starting materials are converted to complex polycyclic architectures bearing multiple stereocentres. It was found that, depending on the sidechain in the starting material, it was possible to achieve four different pathways from the common radical intermediate. Crucially, transannular 1,5-HAT from tertiary and benzylic positions was observed to give diverse products. A proposed 1,5-HAT facilitated SmI2-mediated 6-membered lactone radical cyclisations for the first time without an activating proton donor additive. Enantioselective samarium(II) mediated cyclisation cascades were achieved, where simple beta keto esters are converted to complex polycyclic architectures bearing up to five contiguous stereocentres with high diastereo- and enantiocontrol. In the process, a simple and easy to prepare chiral aminodiol was employed which could be recycled after the reaction. Unprecedented, enantioselective transannular radical cascades allowed access to unique 3- dimensional scaffolds inaccessible by other synthetic methods.
Supervisor: Procter, David ; Mills, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: 6-membered lactones ; ketyl radicals ; keto esters ; 1,5-HAT ; hydrogen atom transfer ; enantioselective cascades ; radical cascades ; smi2 ; Samarium diiodide ; one-pot