New methods and reagents for carbon-fluorine bond formation

Pfeifer, L

Abstract:: After a general introduction about the properties and preparation of organofluorine compounds (Chapter 1), this thesis is divided into two parts focussing on the development of new methods for C–F bond formation (Part A) as well as studies towards the development of novel fluorinating reagents (Part B).

Part A: New Methods for Carbon–Fluorine Bond Formation

Part A consists of two chapters outlining the development of a Pd-catalysed hydrofluorination of alkenylarenes (Ch...
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APA Style

Pfeifer, L. (2016). New methods and reagents for carbon-fluorine bond formation [PhD thesis]. University of Oxford.

MLA Style

Pfeifer, L. New Methods and Reagents for Carbon-Fluorine Bond Formation. 2016. University of Oxford, PhD thesis.

Chicago Style

Pfeifer, L. 2016. “New Methods and Reagents for Carbon-Fluorine Bond Formation.” PhD thesis, University of Oxford.
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Files:: Thesis-Lukas-Pfeifer.pdf

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Authors

+ Pfeifer, L More by this author

Division:: MPLS
Department:: Chemistry
Sub department:: Organic Chemistry
Department:: Department of Chemistry
Role:: Author

Contributors

+ Gouverneur, V

Department:: Department of Chemistry
Role:: Supervisor

+ European Union More from this funder

Grant:: FP7-PEOPLE-2012-ITN-RADIOMI-316882

DOI:: 10.5287/ora-2zaed2r0k
Type of award:: DPhil
Level of award:: Doctoral
Awarding institution:: University of Oxford

Language:: English
Keywords:: Electrophilic Fluorination

Hydrogen Bonding

Nucleophilic Fluorination

Transition Metal Catalysis
Subjects:: Chemistry, Organic
UUID:: uuid:fe082120-eae7-4299-a349-0d42401ff501
Deposit date:: 2017-03-14
ARK identifier:: ark:/29072/ora_fe082120eae74299a3490d42401ff501

Related item:: Hydrogen-Bonded Homoleptic Fluoride–Diarylurea Complexes: Structure, Reactivity, and Coordinating Power
Description:: Hydrogen bonding with fluoride is a key interaction encountered when analyzing the mode of action of 5′-fluoro-5′-deoxyadenosine synthase, the only known enzyme capable of catalyzing the formation of a C–F bond from F–. Further understanding of the effect of hydrogen bonding on the structure and reactivity of complexed fluoride is therefore important for catalysis and numerous other applications, such as anion supramolecular chemistry. Herein we disclose a detailed study examining the structure of 18 novel urea–fluoride complexes in the solid state, by X-ray and neutron diffraction, and in solution phase and explore the reactivity of these complexes as a fluoride source in SN2 chemistry. Experimental data show that the structure, coordination strength, and reactivity of the urea–fluoride complexes are tunable by modifying substituents on the urea receptor. Hammett analysis of aryl groups on the urea indicates that fluoride binding is dependent on σp and σm parameters with stronger binding being observed for electron-deficient urea ligands. For the first time, defined urea–fluoride complexes are used as fluoride-binding reagents for the nucleophilic substitution of a model alkyl bromide. The reaction is slower in comparison with known alcohol–fluoride complexes, but SN2 is largely favored over E2, at a ratio surpassing all hydrogen-bonded complexes documented in the literature for the model alkyl bromide employed. Increased second-order rate constants at higher dilution support the hypothesis that the reactive species is a 1:1 urea–fluoride complex of type [UF]− (U = urea) resulting from partial dissociation of the parent compound [U2F]−. The dissociation processes can be quantified through a combination of UV and NMR assays, including DOSY and HOESY analyses that illuminate the complexation state and H-bonding in solution.
Related item:: Coordination diversity in hydrogen-bonded homoleptic fluoride–alcohol complexes modulates reactivity
Description:: The nucleophilic reactivity of fluoride ion is altered in the presence of hydrogen-bond donors, including alcohols. Relatively little is known about the coordination involved; to rectify this, the X-ray structures of fourteen novel fluoride–alcohol complexes with tetrabutylammonium as the counterion have been determined. The coordination number varies from two to four depending on the steric bulk of the alcohol and is closely linked to trends in reactivity. This diversity in coordination stoichiometry is unprecedented but significant, as it implies differences in the ability of the fluoride–alcohol complexes to dissociate in solution with release of a more active and/or selective fluoride source.
Related item:: cis-Specific Hydrofluorination of Alkenylarenes under Palladium Catalysis through an Ionic Pathway
Description:: This paper describes the hydrofluorination of alkenes through sequential H− and F+ addition under palladium catalysis. The reaction is cis specific, thus providing access to benzylic fluorides. The mechanism of this reaction involves an ionic pathway and is distinct from known hydrofluorinations involving radical intermediates. The first catalytic enantioselective hydrofluorination is also disclosed.

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Copyright holder:: Pfeifer, L

Licence:: Terms and Conditions of Use for Oxford University Research Archive

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Thesis

New methods and reagents for carbon-fluorine bond formation

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New methods and reagents for carbon-fluorine bond formation

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