Novel chemistry of fluorinated carbanions

Abstract

The research described within this thesis may be divided into four main subject areas: I. The amine fluoride TDAE(^2+)2F- (10) has been used as a useful soluble source of fluoride ion in both C-F and C-C bond forming reactions. Methods of synthesis of (10) are described. This work Jed to the observation that TDAE (8), and other amines, could be used as agents for the in situ generation of fluoride, by nucleophilic attack on fluoro-alkenes. Its use allows the effective isolation of the products of dimerisation, co-dimerisation and the perfluoroalkylation reactions for the first time. II. Synthesis and reactions of perfluoro-3, 4-dimethylhexa-2, 4-diene (14) are described. Particular attention is paid to reactions with oxygen and carbon centred nucleophiles. The novel tetrakis(2,3,4,5-trifluoromethyl)benzodioxocin ring system (54) so produced was extensively studied. III. The synthetically useful cyclic diene hexakis(trifluoromethyl)cyclopentadiene (96) has been synthesised from diene (14), by fluoride ion induced reaction with pentafluoropropene (97). This diene can be reduced to the exceptionally stable pentakis(trifluoromethyl)cyclopentadienide anion (84) upon reaction with a range of alkali metal and tetralkylammonium iodides. The mechanism of this reaction appears to be a radical one and, indeed, electrochemical reduction is rapid. The intrinsic stability of (84) is borne out by the fact that concentrated sulphuric acid is required to synthesis its derived acid (109). IV. Diene (96) reacts with a variety of transition metal powders to give corresponding pentakis(trifluoromethyl)cyclopentadienide metal salts. The role of acetonitrile as a solvent in the reaction appears to be crucial to the formation and stabilisation of these species. The salt produced by reaction of (96) with copper powder, tetrakis(acetonitrile)copper (I) pentakis(trifluoromethyl)cyclopentadienide (118), is remarkably stable and an x-ray crystal structure was obtained.