Silver® trifluoroacetate

The silver fluorocomplexes, ie, silver hexafluoroantimonate [26042-64-8], AgSbF silver hexafluorophosphate [26042-63-7], AgPF silver tetrafluoroborate [14104-20-2], AgBF and other salts such as silver trifluoromethane sulfonate [2923-28-6], CF SO Ag, and silver trifluoroacetate [2966-50-9], CF COOAg, play an important role in the synthesis of organic compounds and have gained potential industrial importance. 

A. Silver trifluoroacetate. To a suspension of 187 g. (0.81 mole) of silver oxide (Note 1) in 200 ml. of water is added 177 g. (1.55 moles) of trifluoroacetic acid (Note 2). The resulting solution is filtered, and the filtrate is evaporated to dryness under reduced pressure. The dry silver trifluoroacetate thus obtained is purified by placing it in a Soxhlet thimble and extracting with ether, or by dissolving the salt in 1.2 1. of ether, filtering through a thin layer of activated carbon, and evaporating the filtered ether solution to dryness. The yield of colorless crystalline salt obtained after removal of the ether is 300 g. (88%). 

Commercially available silver acetate may be used in place of the silver trifluoroacetate, but the yield is somewhat lower (75-80%). 

Fluorinated olefins, such as chlorotritluoroethylene, hexafluoropropene, per-fluoroisobutylene, and hexafluorocyclobutene, react with silver trifluoroacetate in the presence of alkali metal fluondes to give perfluoroalkylsilver compounds [270] (equation 186)... 

Tfifluorovinyl- and ( 0-pentafluaropropenylsilver compounds can be prepared via the exchange reaction of the corresponding cadmium compound with silver trifluoroacetate [144] (equation 189) The 2-pentafluoropropenyl silver compound can be synthesized via a similar exchange reaction of silver tnfluo-roacetate with 2-pentafluoropropenyllithium [279]... 

Silver trifluoroacetate is a suitable catalyst for various cationic rearrangements involving multiple carbon-carbon bonds [49 5(1] In the presence of silver trifluoroacetate, 2 propynyl acetates rearrange to the butadienyl acetates to give dienes that are useful in Diels-Alder reactions [49] (equation 22)... 

Silver trifluoroacetate is used in a one step synthesis of bicyclo[3 2 2]nona-6,8-diene-3-one from 2-methoxyallyl bromide and benzene [50] (equation 23) Analogous reactions of toluene, p-xylene, and mesitylene yield the corre spending substituted bicyclo[3 2 2]noiia-6,8-diene-3-ones [50]... 

Figure 4.6 The dimeric structure adopted by some silver carboxylates such as silver trifluoroacetate.

To a solution of 4-t-butylcyclohexanone (lmmol), tris(triphenylphos-phine)ruthenium(n) chloride (0.05 mmol) and silver trifluoroacetate (0.05 mmol) in toluene (5 ml) was added triethylsilane (1.5 mmol). The mixture was heated under reflux for 20 h, and concentrated under reduced pressure. The residue was diluted with hexane (3 ml), filtered and distilled to give a mixture of triethylsilyl ethers (0.96mmol, 96%), b.p. 70°CI 0.1 mmHg. G.l.c. analysis shows an axial (cis) equatorial (trans) ratio of 5 95—a result comparable to the best LAH results. 

Recently Kernaghan and Hoffmann (175a) have investigated the stereochemistry of reaction of cis and trans 1-phenylethenyl bromide, 180. Upon stirring of 180a or 180b with silver trifluoroacetate in isopentane at room... 

Peroxide ring closures were effected by stirring the 2,3-dibromocycloalkyl hydroperoxides with silver trifluoroacetate, and the bromo-substituted bicyclic peroxides were isolated by silica chromatography at —25 °C. Yields (based on 2-cycloalkenyl hydroperoxide) of 56 and 38% were achieved respectively for the [3.2.1]- and [4.2.11-compounds, but only 16% of the [2.2.1]- and 13% of the [5.2.1]-peroxide was obtained. The main reason for the low yield of the [2.2.1]-peroxide was that substitution by trifluoroacetate, which competes with the desired dioxabicyclization, is particularly prevalent with the 5-membered ring. 

Thus, as expected from earlier work 36,37), the dioxabicyclization proceeds with inversion of configuration at the 3-position of the m-2-frans-3-dibromide 30, the stereochemistry at the 2-position being unaffected. However, experiments with individual diastereoisomers unexpectedly showed that the franj-2-m-3-dibromide 31, also reacts with silver trifluoroacetate, albeit less efficiently, to give the same bicyclic peroxide. We feel that this probably proceeds via an isomerisation (Eq. 25). 

We developed a convenient synthesis of 3-cyclopentenyl hydroperoxide via hydro-boration and autoxidation of cyclopentadiene, and bromination proceeded smoothly to afford 32 40). Ring closure with silver trifluoroacetate (Eq. 26) afforded a 5-bromo-2,3-dioxabicyclo[2.2.1]heptane 34 (6%) and a 5-trifluoroacetoxy-2,3-dioxabicyclo-[2.2.1]heptane 35 (14%), and it was shown independently that 34 is rapidly converted into 35 by reaction with Ag02CCF3. To avoid the trifluoroacetate bromide substitution that accompanies and competes with the dioxabicyclization, 32 was treated with silver oxide and this slowly yielded an isomeric 5-bromo-peroxide 33 (42 %) (Eq. 26). 

Bromination afforded a mixture of /rans-3-cw-4-dibromide 38 (65 %) and cis-3-trans-4-dibromide 39, and the reaction of each of these with silver oxide and with silver trifluoroacetate was carried out (Eq. 30). 

The behaviour of the tram-3-bromide 38 closely resembled that of its cyclopentyl analogue 32. Thus with silver oxide only the cis-2-bromo-[3.2.1]peroxide 40 expected for a SN2 ring closure was obtained, and although some 40 was also formed in the reaction of 38 with silver trifluoroacetate, the predominant (90 %) bicyclic peroxide obtained was 41, i.e. the [3.2.1]peroxide available via a bromonium ion mechanism. The behaviour of the tran.v-4-bromide 39 was very revealing, for it did not react with silver oxide and 41 was the only bicyclic peroxide formed with silver trifluoroacetate. 

Since hydrogen peroxide, like alkyl hydroperoxides, can be alkylated by alkyl bromide plus silver trifluoroacetate (Eq. 19, R = H),35) an attractive variation of the silver-salt-induced dioxabicyclization uses cis- 1,3-dibromocycloalkane 43 as starting material. Thus Porter and Gilmore obtained 2,3-dioxabicyclo[2.2.1]heptane 9 in 30-40% yield from c s-l,3-dibromocyclopentane, which was itself obtained from the corresponding c/s-diol by reaction with triphenylphosphine dibromide (Eq. 31 R = R = H)36). 

When colloidal selenium was heated with mercuric trifluoroacetate or silver trifluoroacetate, bis(trifluoromethyl)diselenide was formed (43). Later work with selenium/silver carboxylate, RC02Ag (R = CF3, C2F5, or C3F7), mixtures at 280° C in a vacuum produced a mixture of the bis(perfluoroalkyl)selenide and the bis(perfluoroalkyl)diselenide (44). Formation of a polyselenium trifluoroacetate, which decarboxylates to produce the trifluoromethylselenides, was the proposed mechanism for R = CF3 (44). However, silver trifluoroacetate is a source of trifluoromethyl radicals when heated above 260° C (21), hence the trifluoromethylselenides may be formed by reaction of trifluoromethyl radicals with selenium, as in the reaction of CF3I with selenium [Eq. (34)] (45). 

The five-membered ring can also be formed by intramolecular nucleophilic attack of an alkoxide on a carbamate such as for the formation of 196 from 195 <1997T9553>, by dehydration of fV-carbamate-pipecolic acid derivatives <2002EJO3936>, by treatment of amino-amides under Eschweiler-Clarke conditions <1999TA3371>, or by treatment of hydroxyl aminonitriles with silver trifluoroacetate <2002JA2951> (Scheme 57). 

Butenolides.1 When activated by silver trifluoroacetate, this furan is alkylated by primary alkyl iodides or ethyl a-iodoacetate to give 4-alkyl-2-butenolides (2) in 60-80% yield. 

Silver ions (as silver trifluoroacetate or trifluoromethanesulfonate), Cu", and other transition metal ions in their 1h- oxidation state [99,100] are frequently employed to obtain [M-rmetal] ions from non-functionalized or at least nonpolar hydrocarbons, [101] polyethylene, [102,103] or polystyrene (for an example see Chap. 10.5.1). [99,100,104-106]... 

Synthesis of l,3-dihydro-2,2-bis(trifluoroacetoxy)-benzo[c]tellurophenef A mixture of 2,2-diiodo-l,3-dihydrobenzo[c]tellurophene (4.86 g, 10 mmol) and silver trifluoroacetate (4.42 g, 20 mmol) in benzene (200 mL) was stirred at room temperature for 2 h. After filtration, the fdtrate was concentrated to give l,3-dihydro-2,2-bis(trifluoroacetoxy)-benzo[c]tellnrophene (4.17 g, 91%), m. p. 160°C (dec.). 

The reaction of sulfenyl chlorides, CFwCl3 m SCI (n = 1, 2, 3) with silver trifluoroacetate furnishes stable halogenated sulfenyl carboxylates of the general formula... 

Fluorocarbonylsulfenyl chloride reacts in the following manner with silver trifluoroacetate ... 

Filimonov et al. reported a synthesis of 3,6-diiodocarbazole (387) by iodination of carbazole (1). For the iodination, the required electrophilic iodine was generated by reacting iodine monochloride (ICl) with silver trifluoroacetate (CFsCOOAg) in acetonitrile. Following this procedure, 3,6-diiodocarbazole (387) was obtained in almost quantitative yield (871) (Scheme 5.270). 

Silver trifluoroacetate was obtained from Ruka Chemika or Aldrich Chemical Company, Inc., and used as received. 

Silver trifluoroacetate Acetic acid, trifluoro-, silver(l-t-) salt (8,9) (2966-50-9)... 

Unsymmetrical dialkyl peroxides can be prepared by several methods. Some of them are summarized in Scheme 31. Primary " , secondary or tertiary"" " alkyl hydroperoxides can serve as substrates and are converted to the dialkyl peroxides by acid- or base-catalyzed nucleophilic substitution with alkylating agents like dialkyl sulfate " , diazomethane " , dialkyl sulfites, alcohols " or alkyl halides (e.g. in the presence of silver trifluoroacetate) "". An overview of the results obtained utilizing the method mentioned above is given in Table 7. 

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