Reactions of saturated perfluorinated

PREPRATION AND REACTIONS OF SATURATED PERFLUORINATED HETEROCYCLES CONTAINING OXYGEN, NITROGEN, SULFUR, SELENIUM, AND PHOSPHOROUS... 

Reactions of Saturated Perfluorinated Heterocycles Due to the strong electron withdrawing effect of perfluorinated framework, saturated ethers or amines are extremely week bases and they do not form stable compounds as a result of protonation or alkylation of heteroatom. Unshared electron pair(s) of heteroatom, however, manifests itself in different manner—through the activation of a-fluorine substituents. 

Simons process — Electrochemical polyfluorination reactions of organic compounds are the only efficient way to industrial production of perfluorinated compounds. The reaction proceeds in the solution of KF in liquid HF (b.p. 19.5 °C), where the starting substances as alcohols, amines, ethers, esters, aliphatic hydrocarbons and halo-hydrocarbons, aromatic and heterocyclic compounds, sulfo- or carboxylic acids are dissolved. During anodic oxidation, splitting of the C-H bonds and saturation of the C=C bonds occur and fluorine atoms are introduced. 

Perfluorinated olefins have been found to give both vinyl azides and the saturated fluoroazides on reaction with triethylammonium azide apparently the intermediate carbanion tends to abstract a proton in this case. Reaction of hexafluoropropene (28) with sodium azide in DMF leads stereospecifically to the trans azide 29. 

In the Liquid-Phase Photofluorination [39,44] process the reactant is injected at a very slow constant rate into an inert fluorocarbon solvent which is saturated by fluorine and under U.V. irradiation. Conditions are chosen to ensure that the concentration of fluorine and fluorine radicals is always much higher than the concentration of the substrate. This method is only suitable for the perfluorination of substrates, such as partially fluorinated ethers (see Section 2.5) and amines (see Section 2.7), that are both soluble in perfluorocarbon solvents and can withstand such vigorous reaction conditions. 

The products of the electrochemical perfluorination of aromatic and heteroaromatic compounds are the corresponding perfluorinated cyclic and heterocyclic alkanes.28 and also per-fluorinated derivatives of the heteroaromatic compounds. Perfluorocyclohexane is the principal product from the electrochemical fluorination of benzene and fluorobenzene. Chloro derivatives of perfluorocyclohexane are produced from chlorobenzenes. Anisoles give fully saturated per-fluoro ethers, together with cleavage products. Extensive cleavage is observed in the fluorination of benzenethiols. Chloropyridines, fluorocarbons and sulfur hexafluoride or nitrogen trifluoride are characteristic byproducts from the above scries of reactions. 

Examples of replacement of fluorine in saturated aliphatic perfluorinated compounds by alkoxy and aryloxy groups are relatively scarce since such fluorine atoms are generally inert toward nucleophiles in SN2 reactions. 

Preparation of the corresponding perfluoropolyethers requires a subsequent fluorination step to saturate double bonds and replace hydrogens in the "spacer" groups with fluorine. We have found that the partially fluorinated vinyl ethers produced in the polycondensation reaction undergo reaction with elemental fluorine to give the desired perfluorinated polyethers. Ultraviolet irradiation is required to replace the least reactive hydrogensl ]. 

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