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Title: Palladium-catalyzed [1,3] O→C rearrangement of pyrans towards functionalized cyclohexanones
Author: Barker, Thomas A.
ISNI:       0000 0004 2723 8078
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2012
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Functionalised cyclohexanones are prepared from cyclic enol ethers via a Pd-catalysed [1,3] O→C rearrangement reaction. A variety of α-arylketones are generated with excellent diastereocontrol and yield when basic phosphine ligands are used. In contrast, a Lewis acid is required to promote rearrangement of alkyl-substituted enol ether systems. These reactions proceed in excellent yield, but exhibit poor diastereocontrol. Attempts towards an asymmetric [1,3] O→C rearrangement reaction through the use of chiral phosphine ligands are also described. After screening a wide range of ligands only ^tBu-Phox has provided reasonable levels of enantiocontrol (84% yield, 49% ee). The preparation of enantiomerically enriched enol ethers is also described. Unfortunately, when applied to the rearrangement chemistry, two enantiopure enol ethers have each provided racemic cyclic ketones. Aspects of the reaction mechanism are described, which resulted in the development of a kinetic resolution protocol. This led to the preparation of enantiopure enol ethers (>95% ee) and cyclic ketones. Finally, initial chemistry into the development of a new rearrangement paradigm utilizing a cyclobutadieneiron tricarbonyl mofit is discussed. Although late stage intermediates are prepared, the desired enol ethers could not be prepared, potentially due to the lability of the substrates.
Supervisor: Harrity, Joseph P. A. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available