Perfluoroketones

Aerosol-Based Direct Fluorination. A technology that works on Hter and half-Hter quantities has been introduced (40—42). This new aerosol technique, which functions on principles similar to LaMar direct fluorination (Fig. 5), uses fine aerosol particle surfaces rather than copper filings to maintain a high surface area for direct fluorination. The aerosol direct fluorination technique has been shown to be effective for the synthesis of bicycHc perfluorocarbon such as perfluoroadamantane, perfluoroketones, perfluoroethers, and highly branched perfluorocarbons. 

Aromatic aldehydes and cyclic perfluoroketones are oxidized to a-hydroxy hydroperoxides or bis(a-hydroxy) peroxides, aliphatic ketones are converted to esters, and ketenes are converted to a-lactones... 

AMcycUc perfluoroketones undergo similar oxidation reactions as aromaUc fluoroaldehydes (equation 61). a lower concentration of hydrogen peroride oxidizes the ketones to a-hydroxy hydroperoxides [72], whereas concentrated hydrogen peroxide converts them to I,l -dihydroxydi(petfluorocycloalkyl) peroxides [16, 73] (equation 64). 

Fluorinated heterodienophiles and heterodienes Diels-Alder reactions in which the dienophiles have perfluoroalkyl-substituted multiple bonds between carbon and a heteroatom are quite common Reported earlier were reactions of perfluoroketones, thiones, ketimines, thioesters, nitroso compounds, and nitriles [9] Examples of a-fluoroimines [107], co-hydroperfluorothioaldehydes [108], perfluorosulfines [109, IIO], and selenocarbonyidifluoride [III] (equations 89-92) have been reported recently... 

Compounds with fluorines bound directly to a carbon bearing a hydroxy group are generally very unstable, although there are exceptions. Hexafluoroacetone and hexafluorocyclobutanone both add HF to form stable a-fluoroalcohols, which release HF quickly in water to form the respective hydrates. The stability of these alcohols derives simply from the relative instability of the respective perfluoroketones. Fluorine NMR data for the one example available are provided in Scheme 3.19. Its chemical shift is obviously also influenced significantly by the six P-fluorines. 

Acyclic [87, 88], cyclic, cage [89-91] and poly [91, 92]-perfluoroketones have been successfully synthesised by direct perfluorination (Figs. 29 and 30). 

The addition of chlorine monofluoridc across the C = 0 bonds in difluorophosgene, per-fluoroacyl fluorides, and perfluoroketones with the formation of hypochlorites occurs only in the presence of the catalysts potassium fluoride, rubidium fluoride, cesium fluoride80,81 or the strong Lewis acids hydrogen fluoride, boron trifluoride, or arsenic(V) fluoride.82 The cesium fluoride catalyzed reactions are carried out in an autoclave for 2-3 hours at — 20"C or left overnight.80... 

Because of the very strong /7-C-F bonds of perfluoroalkyl radicals, such species do not disproportionate. Thus the only combinatorial reaction of perfluoroalkyl radicals is that of coupling.When two RF- radicals are generated within a solvent cage, as is the case with perfluoroazoalkane and perfluoroketone photolyses,... 

The formation of polyfluoroalkoxyanions from perfluoroketones was discussed, along with other addition reactions of perfluoroketones, in Section IB, Subsection 2 similar anions can also be generated from acid fluorides and epoxides (oxiranes), as represented in Figure 8.46. 

Hexafluoroacetone has been a popular compound for further photochemical study" " Majer et al. have reported on the photolysis of alicyclic perfluoroketones and of chloropentafluoroacetone other work on fluorinated ketones has been reported by Pritchard et a/. - , by Phillips and Trotman-Dickenson , and by Schuster and Patel . Intramolecular elimination reactions in the photolysis of fluoroaldehydes have been discussed by Morris and Thynne and by Pritchard and Perona . Photolytic studies on other oxygen-containing halogen compounds have included chloroacetic acids , acetyl chloride , perfluoroacyl fluorides , CF3OF and CF3OOCF3 . 

Ketones and aldehydes insert into B-X bonds, and the products vary with the substituents on the substrateU Thus, with BX3 either mono-, bis-, or tn s-inserted products may be obtained in which B-0 bonds are formed. Electron-withdrawing substituents favor insertion. Reactions with ketenes lead to insertion into both the C=C and C=0 bonds . 1,3-Addition of PhBCU occurs with a-diazoethylacetates to form PhClBOC(OEt)=CRCl under mild conditions. Cyclic perfluoroketones react with... 

Other synthetic routes (especially when the parent alcohol is unstable) include the reaction of a metal hydride (or fluoride) and a perfluoroketone, the reaction of a fluoroacyl chloride with a metal chloride or a metal, and the reactions of fluorinated epoxides with cesium fluoride. 

The reactions take place readily in a pressure vessel, at 100-150 C, using an excess of COFj in the presence of a fluoride ion source in an aprotic solvent, such as KF, K[HFj], CsF or [NEt ]F in CHjCN [632]. Under similar conditions, COFj reacts with two molar equivalents of hexafluoropropene to give the perfluoroketone according to [628,1908] ... 

Perfluoroketones are able to abstract hydrogen on irradiation in solution, producing the corresponding ketyl radicals which are detected by e.s.r. spectroscopy.11 Abstraction occurs from trifluoroacetaldehyde [reaction (11)] and from cyclopropane as hydrogen donors. E.s.r. studies also show that photoexcited... 

The quartet is formed in Nafion/Cu(II) by the transformation of the quintet radical, with fliso = 22.5 G. A similar quintet (fliso = 24 G) was detected during the photolysis of perfluoroketones and assigned to radical 1 below. By analogy, radical 2 was proposed as responsible for the quintet detected in Nafion. Structure 2 implies that the unpaired electron is located on the carbon atom in the Nafion backbone that is linked to the pendant chain by loss of a fluorine atom. This structure is in agreement with the detection of fluorine anions during fuel cell operation. ... 

---