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Stereoselective Synthesis of Functionalized Cyclopentane Frameworks Using Anthracene Templates

El Farsi, Najwa (2020) Stereoselective Synthesis of Functionalized Cyclopentane Frameworks Using Anthracene Templates. PhD thesis, University of Sheffield.

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Stereoselective Synthesis of Functionalized Cyclopentane Frameworks Using Anthracene Templates.docx
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Enantiopure allylic alcohols are very powerful synthons for the synthesis of a variety of natural products, agrochemicals and pharmaceuticals; therefore, the synthesis of these compounds has received considerable attention. For this purpose, several strategies involving asymmetric Diels-Alder reaction with 9-methylanthracene 202 have been used to generate the Diels-Alder adduct 203 in high enantioselectivity and acceptable yield, which would be used as a key starting material towards enantiopure allylic alcohols. Among these approaches are: catalytic enantioselective reactions via chiral Lewis acids and organocatalysts, as well as chiral dienes. Unsuccessful attempts to perform asymmetric Diels-Alder reactions highlighted the use of a chiral dienophile strategy. Thus, a modified dienophile protocol by the addition of electron-withdrawing groups was considered. Despite the failure of a sulfone dienophile 272 to perform an asymmetric Diels-Alder reaction in an enantioselective manner, the utilisation of a chiral sulfoxide dienophile 302 was successful in providing (after desulfinylation) an optically pure cycloadduct 203 in 68% yield. An enantiomeric adduct 203 underwent different asymmetric transformations, including dehydrogenation–conjugate addition reaction and reduction, furnishing alkylated alcohols 322-325 with complete conversion and high levels of diastereoselectivity (> 99:1 dr) which was controlled by anthracene system ring. Subsequent retro Diels-Alder reactions via flash vacuum pyrolysis (FVP) demonstrated a valuable method for the synthesis of functionalised allylic alcohols 330-3332 in high enantiomeric excess (67-100% ee).

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Science (Sheffield) > Chemistry (Sheffield)
Depositing User: Miss Najwa El Farsi
Date Deposited: 10 Jun 2020 10:21
Last Modified: 10 Jun 2020 10:21
URI: http://etheses.whiterose.ac.uk/id/eprint/26584

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