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Chung, Hunsuk

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.Open Acces

Stereocontrolled synthesis and rearrangement of epoxides

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