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Title: Stereocontrolled synthesis and rearrangement of epoxides
Author: Chung, Hunsuk
ISNI:       0000 0004 2672 0081
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2007
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This thesis describes two related bodies of work, namely the epoxidation of alkoxydihydropyrans and the synthesis of epoxidation catalysts. For clarity, separate chapters comprising an introduction, results and discussion and conclusion and future work are presented for each. In Chapter 1, the diastereoselective formation of 4,5-c/s'-tetrahydrofuranones via the oxidative rearrangement/Jones oxidation of 2-alkoxy-3,4-dihydro-2//-pyrans is described. High levels of stereocontrol were observed with sterically demanding and branched substituents. Furthermore, this oxidative rearrangement method was applied to the synthesis of y-lactone-containing natural products such as a whisky lactone and a cognac lactone. Additionally, in line with the rearrangement of the heterocycle series, we also investigated an equally rapid route to carbocycles (cyclopentanes) by the cyclopropanation of 2-alkoxy-3,4-dihydro-2//-pyrans using diazomalonate and a copper-based catalyst and a mixture of insertion product and rearrangement product was obtained. The enantioselective formation of tetrahydrofuranones from aryl-substituted alkoxydihydropyrans using an asymmetric epoxidation catalyst (chiral manganese salen catalyst) is presented in Chapter 2. Higher levels of stereocontrol were observed with more sterically demanding and branched alkyl groups, or more electron-donating aryl groups. In Chapter 3, we describe the synthesis of novel chiral ketone catalysts for the asymmetric epoxidation of alkenes. An oxabicyclic ketone catalyst and an azabicyclic ketone catalyst were synthesised and their reactivity and selectivity of epoxidation were investigated. Finally, full experimental details and spectra are presented for all novel compounds synthesised in the course of this work in Chapter 4.
Supervisor: Armstrong, Alan Sponsor: Dongbang FTL
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral