Perfluoro-1,4-dioxane

Originality Perfluoro-1,4-dioxane copolymers are not reported in the patent literature. 

The reaction of enamines with perfluoro olefins has also been reported (62). Dienamines have been reported to react with ethyl acrylate at C2 to give the alkylated a,j8-unsaturated ketone derivative. Thus the dienamine (44) gave 71 in 50 % yield on reaction with ethyl acrylate in dioxane for 40 hr (63). 

Perfluoro(l, 2,3,4,5,6,7.8-octahydronaphthalene) (7 10 g, 23.6 mmol) and activated zinc powder (6g, 91.7 mmol) were placed in solvent (60 mL either dioxane, MeCN or DMF) and stirred under the conditions given in the scheme. Then, the mixture was poured into ice water (50 mL) and acidified with dil HC1. The organic layer was separated and the aqueous solution extracted with Et20. All organic extracts were combined, dried and distilled to yield ... 

The reaction of perfluoro-3,4-dimethylhexa-2,4-diene with calcium hypochlorite leads to the formation of a diepoxide, rearranging at 200 °C into the corresponding derivative of 1,4-dioxane (96RCI703). 

The reaction of perfluoro-4-methyl-2-pentene with ethylene glycol also leads to 2-fluoro-2-trifluoromethyl-3-(2,2,2-trifluoro-1 -trifluoromethylethy-lidene)-l,4-dioxane 106 (96ZOB1995). The formation of the six-membered heterocycle occurs via generation of the intermediate carbanion and fluoride ion elimination from the y-position. Subsequent intramolecular nucleophilic cyclization involving the O-nucleophilic center and the internal double bond leads to a 1,4-dioxane derivative (route e). 

Only perfluoro-tert-butyl copper has been prepared by this method. The compound was isolated in 72% yield from the reaction of m-(tri-fluoromethyl)phenylcopper with perfluoro-fert-butyl bromide in ether-dioxane at 0°C(34). Exchange and cross-coupling reactions occur simultaneously in many reactions between organocopper reagents and various organic halides (69, 97, 174, 217, 220, 266, 297). However, the method is only of limited use as the new reagent [R Cu in Eq. (16)] and its precursor are capable of reacting with both species of halide, RX and R X, present in the mixture. 

Less work had been done with zinc compounds, but enough to indicate a contrast with lithium and magnesium derivatives. For example, perfluoro-n-propyl zinc iodides [50, 51] and perfluoroisopropyl zinc iodides [22] can be obtained, and the n-propyl derivative is even stable in dioxane at reflux. It should be noted that these compounds are stable largely because they are solvated and it has not been possible to remove the solvent completely. Zinc under these circumstances appears to be a very strong acceptor and therefore the compounds decompose much more readily when formed in the free state [52] (Figure 10.12). 

Yokoyama, Y, Hanamoto, T, Jin, X L, Jin, Y Z, Inanaga, J, Perchloric acid in 1,4-dioxane and perfluoro-octanesulfonic acid as practical catalysts for the stereoselective glycosylation of 1-0-acetyl-glycosides. Heterocycles, 52, 1203-1206, 2000. 

---