This thesis deals with the development of new fluorination reactions and their application to fluorine-18 labelling. Fluorine-18 labelled compounds are employed as tracers in Positron Emission Tomography (PET), which is a powerful non-invasive imaging method in medical diagnostics.

The first part of this thesis focuses on the development of a late-stage halogen exchange-based fluorination method for the synthesis of trifluoromethylated molecules. The first project in this area relies on the application of a copper(I)-based fluorinating reagent to furnish trifluoroacetates, trifluorotoluenes and trifluoroacetamides. The second project involves the translation of this methodology into the fluorine-18 labelling of tertiary and secondary trifluoroacetamides. The targeted substrates were labelled in high radiochemical yield and high molar activity using [¹⁸F]Bu₄NF as fluorine source in the presence of an organic activator.

In the second part, the development of electrophilic fluorination reactions using a hypervalent iodine-based reagent is discussed. The first project in this area addresses the development of an electrophilic fluorine-18 fluorination reagent: [¹⁸F]fluoro-benziodoxole. The utility of this reagent was demonstrated in the labelling of [¹⁸F]fluoro-benzoxazepines. In the second project, the same [¹⁸F]fluoro-benziodoxole reagent was used in the rhodium-mediated synthesis of α-[¹⁸F]fluoroethers. High molar activities were obtained in these electrophilic labelling processes. In the third project, the fluorine-19 analog fluoro-benziodoxole was used in the palladium-catalyzed iodofluorination of allyl benzenes, styrenes and cycloalkenes. Both iodine and fluorine atoms in the product arise from the same reagent.

This work is focused on two areas: the chemistry of organofluorine and organoboron compounds. In the first chapter, a copper-catalysed synthesis of tri- and tetrasubstituted allenylboronic acids is presented. Extension of the same method leads to allenylboronic esters. The very reactive and moisture-sensitive allenylboronic acids are further applied to the reaction with aldehydes, ketones and imines to form homopropargyl alcohols and amines. In addition, an enantioselective reaction catalysed by a BINOL organocatalyst was developed to form tertiary alcohols with adjacent quaternary carbon stereocenters.

The second chapter specialises in the functionalisation of 2,2-difluoro enol silyl ethers with electrophilic reagents under mild reaction conditions. This allowed for the formation of perfluoroethyl ketones, 2-aryl-2,2-difluoro ketones as well as the novel -COCF₂SCF₃-moiety. 

The third chapter continues with electrophilic fluorination. A synthesis of an electrophilic, ¹⁸F-labelled hypervalent iodine reagent from nucleophilic ¹⁸F-labelled tetrabutylammonium fluoride was devised. Then, the ¹⁸F-labelling of o-styryl benzamides using the developed reagent afforded [¹⁸F]benzoxazepines in good radiochemical yields and molar activity.

The objective of the final chapter was the development of a method for the nucleophilic ¹⁸F-labelling of 2-halo-2,2-difluoro ketones derived from the corresponding 2,2-difluoro enol silyl ethers. The radiochemical utility of this method was demonstrated by fluorine-18 labelling of a potential neutrophil elastase ligand followed by successful preclinical studies.