I. The β- pentapluorophemylethyl anion II. reactions of perfluoro-3,4-dimethyl-3-hexene and related compounds

Abstract

Part I.A study has been carried out on the effect of a pentafluorophenyl substituent in promoting carbanion rearrangements in a simple ethyl system. Analogous non-fluorinated systems are reported to have produced rearrangement only with caesium or alkali metal alloys. The reactions of 1-bromo-2-pentafluorophenylethane with magnesium and lithium have been studied under various conditions. The major product in the case of lithium was the corresponding ethene, formed by decomposition of the lithium compound. With magnesium the expected ethane was formed on hydrolysis. Isotopic labelling studies indicated that no rearrangement occurred in this system. The evidence suggests that a single pentafluoro- phenyl group is insufficiently activating to cause rearrangement to occur with the less active alkali metals. Part II. The reactions of an "internal" fluoroalkene (perfluoro-3,4-dimethyl- 3-hexene) with various carbon and nitrogen nucleophiles have been investigated. Unusually, a terminal elkene has been produced as the major product with a carbon nucleophile, rather than the more highly substituted Isomer. The reactions with nitrogen nucleophiles have resulted in products being formed from each of the three isomers of perfluoro-3,4-dime thyl-3-hexene.An interesting series of fluorinated furans has been prepared, with a variety of substituents at the 2-position. These are related to the internal fluoroalkene discussed above. This series has provided a useful probe for the investigation of the photochemistry of fluorinated furans. The expected products (cyclopropenylketones) were obtained in all cases except where the substituent was perfluoro-1-H-T-H-propyl, where the only observed products resulted from loss of HP from the side chain. Specificity in ring opening was only observed for one furan - perfluoro-3,4,5-triraethylfuran.Perfluorotetramethylfuran has proved to be largely inert to nucleophilic attack and reaction with addition reagents.