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Title: Ullmann etherification
Author: Cox, Robert John
ISNI:       0000 0004 6499 4948
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2015
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Formation of the diaryl ether moiety remains a challenging target for organic synthesis despite modern technologies, however, better understanding of older techniques often leads to improvements. The copper-catalysed Ullmann ether synthesis, whilst attractive in many ways, is frequently problematic due to the inherent irreproducibility of the reaction on scale up. Little is yet known about the mechanism of the reaction and conflicting views are rife within the scientific community. In a well-studied example, we show that the potassium iodide formed during the reaction slows catalysis. Additionally, the deprotonation of phenol is complicated by the insolubility of the inorganic base. This results in a beneficial outcome, providing a rate enhancement and reduction of by-products, which can be further exploited to provide lower stoichiometries, improved selectivity and greater functional group tolerance. The development of an improved, more reproducible procedure in combination with reaction calorimetry has allowed the mechanism to be studied in intricate detail. Excellent agreement with a mechanistic model has led to further insight into the enigmatic aryl halide activation and provides good evidence for a single electron transfer mechanism. In addition, evidence for a dynamic catalyst resting state has been observed which adds to the complexity of the mechanism. This, in turn, leads to a fine balance of concentration and electronic effects that prove vital to the rate of reaction.
Supervisor: Lloyd-Jones, Guy ; Campbell, Colin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: diaryl ether moiety ; organic synthesis ; Ullmann ether synthesis ; enigmatic aryl halide activation