Fluorinated aza-alkenes and dienes

Abstract

In this thesis the cobalt trifluoride fluorination of a series of perfluoroalkyl-pyridine, -pyrimidine, -pyrazine, -pyridazine, and -toluene derivatives is described. In general, these gave good yields of the corresponding cyclohexadiene andmonoene derivatives. The photochemistry of a number of the new dienes has been studied. Irradiations led to ring opening and fragmentation reactions which were analogous to those shown by corresponding hydrocarbon systems. Various reactions with fluoride ion have been investigated. Addition of fluoride to perfluoro-1-aza-4-isopropylcyclohexa-l,3-diene gave the stable perfluoro-l-aza-4-isopropylcyclohex-3-enyl anion. The reaction of N,N'-bis- 1,3-diazacyclohex-2-enyl led to an interesting rearrangement involving internal nucleophilic attack at a saturated position. Reactions of some of the new dienes with diazomethane are also described. These gave bicyclic products arising from 1,3-dipolar addition followed by elimination of either nitrogen or hydrogen fluoride. The chemistry of perfluoro-2,5-diazahexa-2,4-diene has also been studied. Reactions with fluoride ion in solution gave only dimers, but the reaction with caesium fluoride in the vapour phase provided a new and convenient route to perfluoro-1,3-diaza-l-methylcyclopent-2- and -3-enes. Defluorination over heated iron filings gave a new imidazole derivative, a reaction which represents the first synthetic route to a compound of this type. A series of similar reactions using iron, nickel, and platinum were only partially successful. Photochemical reactions were unsuccessful. A preliminary investigation into the chemistry of perfluoro-1,3-diaza-l- methylcyclopent-2- and -3-enes is described. Reactions with caesium fluoride led to dimerization but products arising from nucleophilic displacement of