Perfluoro olefins

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). 

The alkylation of enamines with nitroolefins, which gives intermediates for reductive cyclization (6S2), also provided an example of a stable cycliza-tion product derived from attack of the intermediate imonium function by the nitro anion (683). A previously claimed tetrasubstituted enamine, which was obtained from addition of a vinylsulfone to morpholinocyclohexene (314), was shown to be the corresponding cyclobutane (684). Perfluoro-olefins also gave alkylation products with enamines (685). Reactions of enamines with diazodicarboxylate (683,686) have been used diagnostically for 6-substituted cyclohexenamines. In a reaction of 2-penten-4-one with a substituted vinylogous amide, stereochemical direction was seen to depend on solvent polarity (687). 

Measurements of the enthalpy of thermal decomposition of five co-ordinate perfluoro-olefin and -acetylene-iridium(I) complexes according to the equation... 

Complexes of cyclic perfluoroolefins are also quite common. For example, the iron and platinum complexes of perfluorocyclobutene, 20 (62) and 21 (56), have been prepared. Recently the chemistry of the smallest cyclic perfluoro-olefin, perfluorocyclopropene, has been explored, and initial results indicate... 

Perfluoro olefins combine with azides more slowly than their hydrocarbon counterparts.145 Thus benzyl azide adds slowly to perfluoropropene and -butene to give the corresponding triazolines (Scheme 29), which exhibit unusual thermal stability.145... 

The reversible fluoride ion-catalysed rearrangements of perfluoro-olefins (Miller et al., 1960) may also cause vinylic fluorine—fluorine exchange by a similar mechanism. 

In the presence of alkaline metal fluorides or tertiary amines, perfluoro-olefins react with fluorine-containing keteneimines to form azetidines 25 in mild conditions (76IZV1813). The role of the catalyst seems to be the transformation of the electrophilic keteneimine into the nucleophilic mesomeric anion capable of adding at the multiple bond of the perfluoro-olefin. The addition is accompanied by cyclization generating a catalyst. 

This methodology yields various heterocyclic compounds in reactions using internal perfluoroolefins or systems with conjugated multiple bonds as precursors. Hopefully, this approach will find wide use and new information will permit more profound generalizations. On thermolysis or photolysis aziridines are converted into azomethine ylides, reacting with perfluoro olefins (for example, hexafluoropropylene and perfluorobut-2-ene) to give pyrrole derivatives (autoclave, 160 °C) (76CJC218). 

The preparation of several substituted perfluorocyclopropanes by heating difluorodiazirine with substituted perfluoro olefins has been reported. These compounds are not formed (or only in poor yield) in the corresponding photochemical systems, again because of the relatively high energy of activation of the addition reaction. 

Since the ionization potentials of perfluoro-olefins such as perfluoropropene, C,Felectron-oxidized by Ag sJ,. The observed quantitative oxidation of CjFs to QFg therefore probably involves two sequences of electron oxidation followed by F attack on the radical cations, as follows ... 

The reaction of silver salts with perfluoro-olefins in the presence of fluoride ion gives rise to perfluoroalkyl derivatives of silver [333] to... 

Scheme 2.28 Reductive defluorination-aromatization under milder reaction conditions suitable for laboratory-scale synthesis of perfluoro-olefins and related products (Hg = photochemically excited mercury) Cp = pentamethylcyclopentadienyl [75. 76].

Later we developed higher homologs in the series of RfCOOF using the same synthetic pathway and used them as unique initiators for polymerization of perfluoro olefins in a way that no undesirable "end groups" were formed (12) (figure 3). 

Rujimethabhas and Jones [136] have compiled a list of relative reactivities for some perfluoro-olefins with nitrogen atoms (see Table 39). The uncertainty in the initial step of the reaction forbids assigning any absolute rate coefficients, and, indeed, a rather different series of average overall rates and relative rates are obtained depending on... 

Enamines react as nucleophiles with perfluoro-olefins, hexafluoropropene forming, for example, rearranged enamine (46), and after hydrolysis ketone (47) as a mixture of two stereoisomers, when allowed to react with enamine (48). The... 

Sitroxides, Hydroxylamines, arui Nitroso- and Nitro-con unds. Detailed accounts of the synthesis of perfluoro-2,5-diazahexane-2,5-dioxyl, -O NCCFsi CFs CFs -N(CF3) 0", and of its reactions with hydrogen bromide [— CF3 N-(OH) CF2 CFz N(OH) CFs), nitiic oxide K CFa NfO-NO CFa-CFa N(0-N0)-CF3], perfluoro-olefins [CFaiCFRp (Rp = F or CFa)->alternating... 

Oxygen.—Alcohols, Alkoxides, Esters, and Ethers. Information culled from the patent literature is presented at the end of this chapter (p. 303). The ether chemistry associated with perfluoro-olefins, etc., is noted in Chapter 2 except that which is connected with polymers derived from vinyl ethers (see p. 280). Fluoronitro-alcohols, -esters, and -ethers are dealt with in the nitrogen section of this Chapter (p. 246). 

Also available are papers that deal with (i) the chemistry of 1,2-dichIorovinyl trifluoromethyl sulphone [dHCl CHCl + CFa SCI-Av-i-CFa S-CHCl CHQs- -(with CFs COsH) CF3 SO CHCI CHCI2 -> (with EtsN) CFrSO-CCl CHa (with CFs-COsH) CFs SOs-CChCHCl (with p-ClCaH -SH) CFs-SOa-CCl -CH-S-C6H4CI-P (with CFs-COsH) CF3SO2CCI CH-SOa-C0H4CI-p CFs SOa-CChCHCl + NaaS (CF3 S02-CCl CH)aS (with CFa-COsH) (CF3-SOa CCI CH)aSOa CFs SOa-CChCHCl + RH CFs-SOa-CCliCHR (R = piperidine)] (ii) yet more information on the conversion of perfluoro-olefins into /3-sultones and related compounds(iii) analysis of the F n.m.r. 

A number of reports concern the attack of nucleophiles on perfluoro-olefins to give cumulenes or heterocumulenes, which in turn imdergo nucleophilic attack to give heterocyclic compounds with perfluoroalkyi substituents. o-Phenylenedi-amine reacts with hexafluoropropene to give 2-(o j8j8>tetrafluoroethyl)benzimidazole (301) ketenimine intermediates have also been utilized in the formation of quinolines (302) (see p. lll) 89.59o j,y intramolecular cyclization, and (303) (see p. 112) by intermolecular cyclization, naphthyridines (304), pyridopyrimidines (305), and isoquinolines (306). The pyran derivative (307) is formed via isomerization of an allene intermediate (see p. 100). 3-Fluoro-2-isopropyl-l,2,4-thiadiazolin-... 

Treatment of perfluoro-t-butylmercuric chloride with perfluoropropene in the presence of potassium fluoride (in DMF at 50 °Q yields bis(perfluoro-isopropyl)mercury via displacement of perfluoro-t-butyl anion. Potassium fluoride-initiated reaction of the mercurials (RF)jHg [Rf = (CFgljCF or (CFg)3C] with sulphur in hot DMF gives the corresponding mercaptides [(RFS)aHg]. Displacement of Rf from these mercurials with sodium iodide in a dipolar aprotic solvent occurs readily and, in the absence of electrophilic traps, perfluoro-olefin formation (CFg-CXiCFg X = F or CF3) occurs via j3-elimination of fluoride ion. ... 

The synthesis of azo-compounds via condensation of perfluorinated w-nitrosoalkanecarboxylic acids or esters with amines was mentioned earlier [item (vi), p. 231]. An alternative method to the AtNHj-RfNO condensation for the preparation of azo-compounds of the type AtNiNRf (Rf = perfluoro-alkyl or -cycloalkyl) has now been discovered, viz. trapping of peifluoro-carbanions (from perfluoro-olefins + caesium or potassium fluoride) with arenediazonium salts (see Scheme 36). ... 

The nitration of hexafluoropropene, Cp3-CF=CF2 and octafluoroisobutene (CF3)3C=CF3 has been described, and it was found that the reactivity of perfluoro olefins toward NO falls from tetrafluoroethylene to hexafluoropropene, and further to octafluoroisobutene [66]. Whereas tetrafluoroethylene reacts explosively with NO and nitration must be conducted in a solvent, hexafluoropropene reacts gently in the absence of solvents over 7 days at room temperature or 4-6 hours at 100 "C, and octafluoroisobutene reacts only at 170-180 °C. The nitration of hexafluoropropene is in accordance with the scheme ... 

Recently, some halogenated materials have been found which can be reacted with synthesis gas. These are compounds which have the halogen relatively tightly bound chlorinated aromatics [289], perfluoro olefins [290] or vinylic chloride compounds [291, 292] (table 22). 

Chambers RD, Findley AA, Philpot PD, Fielding HC, Hutchinson J, Whittaker G (1978) Perfluorinated derivatives of furan via novel cyclisation reactions of perfluoro-olefins. J Chem Soc Chem Commun 431 32... 

As with other perfluoro olefins, it is found that certain pentafluorothio olefins will form perfluoro carbanions. This is either deduced from the isolation of products which are formed through their intermediacy or through direct observation. One general feature of such SF5-anionic species in solution seems to be a yellow color, as well as the substantial low-field n.m.r. shift of all sulfur bonded fluorine resonances (they appear at 80-110 ppm, instead of 50-80 ppm in the neutral species). With the olefin SF5(CF3)C=CF2 and metal fluorides the following reactions are observed ... 

Reactions of perfluoro olefinic compounds with iron carbonyls are also found to be somewhat unusual due undoubtedly to the high electronegativity of the fluorine atom. Tetrafluoroethylene was found to react with Fe3(CO)i2 to give a complex, first thought to be (LXV) 81) but subsequently shown to be the o-bonded Fe(CO)4 complex (LXVI) 82, 83). The formation of (LXVI) in this manner is related to the fact that whereas Fe-alkyl bonds are very unstable, Fe-perfluoroalkyl bonds, as in the complex (CF3—CF2)2—Fe (CO)4, are found to be quite stable 84). 

Studies on the quenching of electronically excited hexafluoroacetone by perfluoropropene, and the effect of c r-piperylene on oxetan production, have provided strong evidence that the ketone-olefin cycloaddition results primarily from molecular addition of the excited hexafluoroacetone triplet to the electron-deficient double bond of the perfluoro-olefin. ... 

Mercury.—A new convenient method of synthesis of perfluoroalkyl derivatives of mercury has been developed, viz. reaction of mercuric chloride with perfluoroalkylpotassium compounds prepared in situ from potassium fluoride and perfluoro-olefins, e.g. 

Perfluoroalkylsilver compounds may be readily prepared by the addition of silver fluoride to perfluoro-olefins in acetonitrile, e.g. 

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