New methodology for nucleophilic fluorination
This work describes the development of three methods for the fluorination of electrophilic substrates:1.) The reaction of caesium fluoride with perfluoro(2-methylpent-2-ene) leads to the formation of perfluoro(2-methylpentan-2-yl)caesium. This perfluoroalkyl carbanion has been shown to undergo significant fluoride ion exchange at temperatures above 60 C. Thus, reaction of a solution of the carbanion with a suitable electrophile resulted in the selective formation of a carbon-fluorine bond or perfluoroalkylation of the electrophile.2.) Caesium fluoride has been developed as a moderately effective nucleophilicfluorinating agent in the Room Temperature Ionic Liquid (RTIL) solvent [BMIM][PF(_6)]. The fluorination of a range of volatile substrates was studied, and fluorination in the absence of a conventional organic solvent was demonstrated. Recycling of the solvent has been investigated, as has the decomposition of [BMLM] [PF(_6)] in the presence of caesium or potassium fluoride at elevated temperatures.3.) Reaction of a highly fluorinated azaheterocycle with DMAP leads to the formation of a fluoride salt. This salt, formed in situ, was used as a source of nucleophilic fluoride ion for the fluorination of a range of electrophiles. Several of the fluoride salts were converted to their more stable tetrafluoroborate or triflate analogues and characterised.