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Title: Synthesis and fluorination of diaryliodonium salts
Author: Abudken, Ahmed M.
ISNI:       0000 0004 7964 1264
Awarding Body: University of Leicester
Current Institution: University of Leicester
Date of Award: 2019
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The introduction of a fluorine atom into pharmaceutical compounds helps to change pharmacokinetic properties such as lipophilicity, pKa/pKb, metabolic stability and conformation. Many pharmaceutical molecules contain aromatic rings, so finding ways to fluorinate aryl moieties is crucial. Recently, hypervalent iodine(III) compounds showed great promise in a variety of transformations. More specifically, diaryliodonium salts are used widely in the fluorination of aromatic compounds because they are excellent leaving groups with high electrophilic properties which facilitate the fluorination of aryl moieties. In chapter two a series of novel unsymmetrical diaryliodonium salts are reported which were synthesized in high yields under mild reaction conditions. The protocol was achieved through reaction of fluoroiodane 1.22 with an activated aromatic under acidic conditions. Generally, the new salts contain a sidearm with a hydroxyl group and two methyl groups. The fluoroiodane 1.22, which has two methyl groups, used in this chapter was prepared via a multi-stage reaction pathway which gave high yields in each step following Stuart's protocol. In chapter three, a new cyclic hypervalent iodine(III) reagent 3.5 is reported which was prepared by a five step synthesis. The new reagent 3.5 contained a methyl and phenyl group in the sidearm instead of two methyl groups which are in the orginal fluoriodane reagent 1.22. The fluoroiodane 3.5 was also reacted with a series of activated aromatics under the same conditions as in chapter 2 in order to prepare a new class of unsymmetrical diaryliodonium salts. Generally, it was found that 3.5 was more reactive than 1.22 in terms of yields. In addition, when 3.5 was used, the diaryliodonium salt dehydrated easily in the presence of triflic acid to form an alkene sidearm. In chapter four the new salts were fluorinated with KF in DMF in the presence or absence of a copper catalyst. Interestingly, the fluorination of diaryliodonium salts having a hydroxy group in the sidearm was unsuccessful due to the strong interaction between the oxygen atom of the hydroxyl group with the iodine(III) centre. However, moderate to high yields of the desired fluorinated products were obtained in the fluorination of the diaryliodonium salt which contained an alkene sidearm.
Supervisor: Hope, Eric G. ; Stuart, Alison M. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available