Antimony V Fluoride

Related Reagents. Antimony(V) Fluoride Boron Trifluoride Etherate Diethylaluminum Chloride Dimethylaluminum Chloride Ethylaluminum Dichloride Methylaluminum Dichloride Tin(IV) Chloride Titanium(IV) Chloride Triethylaluminum Trimethylaluminum. 

(a) Thomas, C. A. Anhydrous Aluminum Chloride in Organic Chemistry, ACS Monograph Series Reinholdt New York, 1941. (b) Shine, H. J. Aromatic Rearrangements, Elsevier Amsterdam, 1967. (c) FF1967,1, 24. (d) Olah, G. A. Friedel-Crafts Chemistry, Wiley New York, 1973. (e) Roberts, R. M. Khalaf, A. A. Friedel-Crafts Alkylation Chemistry, Marcel Dekker New York, 1984. 

Paul Galatsis University of Guelph, Ontario, Canada 

Solubility SbFs reacts with most organic solvents, forming solids with ether, acetone, carbon disulfide, and petroleum ether. SbFs is soluble in SO2 and SO2CIF. 

Form Supplied in viscous liquid commercially available. Handling, Storage, and Precautions SbFs is extremely corrosive, toxic, and moisture sensitive. It can be purified by distillation. SbFj fumes when exposed to atmosphere. It should be stored under anhydrous conditions in a Teflon bottle and handled using proper gloves in a well ventilated hood. 

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Antimony Pentafluoride. Antimony(V) fluoride [7783-70-2], colorless, hygroscopic, viscous Hquid that has SbF units with... 

The role of Lewis acids in the formation of oxazoles from diazocarbonyl compounds and nitriles has primarily been studied independently by two groups. Doyle et al. first reported the use of aluminium(III) chloride as a catalyst for the decomposition of diazoketones.<78TL2247> In a more detailed study, a range of Lewis acids was screened for catalytic activity, using diazoacetophenone la and acetonitrile as the test reaction.<80JOC3657> Of the catalysts employed, boron trifluoride etherate was found to be the catalyst of choice, due to the low yield of the 1-halogenated side-product 17 (X = Cl or F) compared to 2-methyI-5-phenyloxazole 18. Unfortunately, it was found that in the case of boron trifluoride etherate, the nitrile had to be used in a ten-fold excess, however the use of antimony(V) fluoride allowed the use of the nitrile in only a three fold excess (Table 1). 

Sb2Fii] units are present in the compound XeF2(SbFs)2 which has a central fluoride ion coordinated to two antimony(V) fluoride molecules 38). 

The first long-lived fluorine-containing carbocation was discovered by Olah and coworkers.32 Thus, the fluorodimethylcarbcnium ion [Me2CF+] was obtained by protonation of 2-fluoropropene and also from 2,2-difluoropropane by reaction with antimony(V) fluoride. In the course of these investigations it was found that a-F stabilizes a cationic state, whereas fi-F is destabilizing. Attempts to prepare the simplest member of this class, the trifluoromethyl carbocation CF3+ failed. The ionization of trifluoromethyl halides with antimony(V) fluoride at — 80 C yielded only carbon tetrafluoride. 

In 1969, the first perfluorinated cation, pcrfluorocyclopropenium, was reported, generated from perfluorocyclopropene and antimony(V) fluoride.33 Using a similar reaction the allylic cation CF2—CF+—CF2 was made from hexafluoropropene.34 Despite the fact that fluorinated cations are not stable enough to be isolated, their lifetime is often long compared with the NMR timescale. This allows the identification of the cation by H and 19F NMR at low temperatures, although in equilibrium with the starting alkene. 

Kinetically controlled conditions favor the formation of mixed fluorinated compounds if per-halo derivatives are fluorinated with hydrogen fluoride. Therefore, catalysts or coreagents are used to overcome this problem. Thus, selective fluorination of l,3-bis(trichloromethyl)benzene cannot be achieved by hydrogen fluoride using variations in temperature, pressure or time.247 However, if antimony(V) fluoride is added to hydrogen fluoride the reaction produces l-(tri-chloromethyl)-3-(trifluoromethyl)benzene. Selective fluorination can also be performed in compounds with different substitution patterns.247,251 253... 

The first purely chemical synthesis of fluorine was accomplished in 1986 by Christe2 and is remarkable for its simplicity and elegance. The two starting materials, potassium hexa-fluoromanganate(IV) and antimony(V) fluoride, had been known4 5 for almost a century and can be readily prepared from hydrogen fluoride solutions according to ... 

The action of strong aprotic Lewis acids (antimony(V) fluoride, arsenic(V) fluoride etc.) provokes the ionization of xenon difluoride, leading to the formation of fluoroxenonium salts XcF + MFn or Xe2F3 MFn less strong acceptors of the fluoride ion (hydrogen fluoride, boron trifluoride, etc.) polarize the xenon difluoride molecule. 

Aluminum trichloride and boron trifluoride as additives have a similar effect on the fluorination of (trichloromethyl)benzene by antimony(III) fluoride. With the additives, the reaction starts even at O C but no exchange is observed in the absence of the catalysts.12 The relative exchange reactivity order of the antimony halides is as follows antimony(III) fluoride < anti-mony(III) fluoride + antimony/V) chloride < antimony(V) dichlorotrifluoride, antimony/V) di-bromotrifluoride < antimony/V) fluoride.3... 

Replacement of Halogens by Fluorine and Addition of Fluorine to C = C Bonds with Antimony(V) Fluoride and Fluoroantimonates... 

All the chlorine atoms in hexafluoro-2-(trichloromethyl)propan-2-ol (1) are substituted by fluorine with antimony(V) fluoride under mild conditions.91... 

The use of antimony(V) fluoride in combination with bromine makes possible the selective substitution of one or two bromine atoms by fluorine in 2,2-dibromo-l,l, 1-trifluoroethane (3) and l,2.2-tribromo-l,l-difluoroelhane (4).92... 

The trichloromethyl group in 4-chIoro-8-methyl-2-(trichloromethyl)quinoline is completely fluorinated with antimony(V) fluoride/antimony(V) chloride when the reaction is carried out in dichloromethane at — 5 to 0 C and then at room temperature for 48 hours to give 4-chloro-8-methyI-2-(trifluoromethyI)quinoIine in 68% yield.4,3... 

Antimony(V) fluoride reacts with almost all common solvents. For this reason the fluo-rination of hexachlorobenzene with antimony(V) fluoride is carried out using antimony(V) chloride as the solvent with heating at reflux for 1 hour. The mixture of products (49 % conversion) contains 33 compounds, mainly l,2-dichloro-3,3,4,4,5,5,6,6-octafluorocyclohcx-1-cne (56 %), 1,2,4,5-tetrachloro-3,3,6,6-tetrafluorocyclohexa-1,4-diene (16%), 1,2,4,5-tet rachloro-3,3,4,5.6,6-hexafluorocyclohex-1-ene (7%), and l,2,4-trichloro-3.3.4,5,5,6,6-hcptafluoro-cyclohex-l-ene (5%).94... 

The reaction of tetrachlorothiophene (5) with antimony(V) fluoride/antimony(V) chloride is accompanied by ring opening and desulfurization to (Z)- and ( )-2,3-dichIorohexafluorobut-2-ene (6).94... 

On gradual heating to 300 C with four equivalents of antimony(V) fluoride and simultaneous distillation of the reaction product, octafluoronaphthalene is transformed to perfluoro-1,2.3,4-tetrahydronaphthalene in 77% yield.94 Under similar conditions 2-substituted hepta-fluoronaphthalenes(R = H, Cl) give a mixture of octafluoronaphthalene and the corresponding 6-substituted undecafluoro-1,2,3,4-tetrahydronaphthalenes in about 40 % yield while the major fluorination product of the compound with R = CF3 is perfluoro(6-methyl-1,2,3,4-tetrahydro-naphthalene) (50%).97... 

The fluorination of polyfluorocyclohexenes with antimony(V) fluoride proceeds under much more severe temperature conditions ( 150 C) than with vanadium(V) fluoride (see Section 12.4.2). In these reactions antimony(V) fluoride effects both the oxidative addition of fluorine and the substitution of vinyl chlorine atoms by fluorine.48... 

Antimony(V) fluoride adds two fluorine atoms to tcrvalent phosphorus attached to electron-withdrawing fluorinated groups 44100 e.g. tetrafluoro(penlafluorophenyl)-/l5-phosphane (7) is obtained by this reaction in 57% yield."... 

Organogermanes R, GeX (X = H, MeO, Cl, Br) do not react with antimony(V) fluoride/carbon, but allyl —germanium bond breaking occurs under mild conditions (24 h at 25 C in diethyl ether), and in high yields (80-85%), leading to the corresponding fluorogermanes.101... 

Trifluorodi(phenyl)-A5-stibane is also prepared by treating fluorodi(phenyl)stibane with xenon difluoride (in 98 % yield)10 1 or (difluoroiodo)benzene (in 70% yield).107 The reaction of benzene and substituted benzenes with antimony(V) fluoride has been used to prepare the corresponding diaryltrifluoro-/5-stibane hydrates but in yields as low as 7-20%.108... 

The relative fluorination activity of the aromatic antimony(V) fluorides can be judged by comparing the products of their reaction with (trichloromethyl)benzene conducted in l-2mL of dichloromethane for 2 hours at a fluorinating agcnl/substrate ratio of 1 -1.2 1 (Table 4).104... 

Table 4. Fluorination Activity of Aromatic Antimony(V) Fluorides...

Arenediazonium hexafluoroantimonates were described as early as 1935,275 but their fluorodediazoniation was only studied much later.276 They deliver fluoroaromatics in better yields than other diazonium salts only when electron-withdrawing groups (N02, C02H) are present on the ring. Otherwise, antimony(V) fluoride formed in the reaction acts as a strong Lewis acid and catalyzes the formation of byproducts. The phenomenon is more pronounced with diazonium hexafluoroarsenates which deliver fluoro compounds in acceptable yields only from nitroanilines.276 With unsubstituted or electron-releasing substituted anilines, difluo-rinated arenearsonic acids are often the major product. 

A series of functionalized alkenes has been subjected to selective epoxidation reactions. Oxidation of perfluorinated vinyl polyethers by bubbling oxygen through the liquid that contains a catalytic amount of a Lewis acid, e.g. antimony(V) fluoride, results in the formation of acid fluorides together with a smaller amount of C = C bond cleavage.76 Perfluorinated pentaaIkyI-2.3-dihydrofuran 38, an example of an unsaturated cyclic ether that is quite stable owing to perfluoroalkylation. is epoxidized by hypochlorite to the product 39 at 45 C.62... 

Chloroheptafluorobut-l-ene (3) isomcrizes in the presence of antimony(V) fluoride to give an E Z mixture of but-2-ene 4.8 4-Chloroheptafluorobut-l-ene also gives the isomeric but-2-cne (see also Section 5.1.2.2.). 

The reaction of perfluoroalkenes with antimony(V) fluoride has been extensively studied by German and others from his group.3 Perfluoroalk-1-enes 1 react under mild conditions with antimony(V) fluoride to give ( )-perfluoroalk-2-enes 2.818... 

When w.//-perfluoroalk-l-enes longer than butene [CHF2(CF2)nCF = CF2, n = 2-7] are isomerized under conditions of thermodynamic control, however, mixtures of all possible positional isomers are obtained. Isomerization of these aik-1 -enes with antimony(V) fluoride under conditions of kinetic control yields the corresponding alk-2-enes as an EjZ mixture.20... 

The vapor-phase pyrolysis of pcrfluorohept-1-ene at 400 C in the presence of carbon results in complete conversion into the isomeric hept-2- and hept-3-enes in a ratio of 1 3.4.34 As noted above, mixtures are also obtained with cesium fluoride and letraelhylammonium fluoride. Only the antimony(V) fluoride reaction allows selective rearrangement to the alk-2-ene. 

Reactions of pcrfluoroalkadienes with antimony(V) fluoride are similar to those of per-fluoroalkenes. Terminal dienes 1 rearrange with antimony(V) fluoride at 0-20 C selectively to internal dienes 2, in which the terminal trifluoromethyl groups are predominantly in the configuration.3,37,38 Higher temperatures and a threefold excess of catalyst lead to cyclo-pentenes (see Section 5.3.3.1.). 

Perfluorotetrahydronaphthalene 5 is isomerized with antimony(V) fluoride to the corresponding 1.2,3,4-tetrahydronaphthalene 6 quantitatively and at low temperature, indicating that aromatization is favored,3,39... 

Perfluoropenta-1,4-diene (10) isomerizes in the presence of antimony(V) fluoride to an E jZ mixture of 1,3-diene 11.41 Heating 11 at 90 C with antimony(V) fluoride gives cyclodimer 12, presumably via allene intermediate 13. 

A fluoro-Beckmann rearrangement has been reported for perfluorinated /V-fluoro-subsliluted ketimines 6. which undergo a 1,2-perfluoroalkyl shift to give perfluorinated imidoyl fluorides 7 when heated with antimony(V) fluoride.2... 

T/-Octafluorohydrazobenzene (12) is converted into octafluorobenzidine (13) in the presence of hydrogen fluoride/antimony(V) fluoride (1 1) or fluorosulfonic acid/antimony(V) fluoride (1 1).12... 

Perfluoro(l -ethyl-1,2,3,4-tetrahydronaphthalene) (55) undergoes alkyl group migration to form perfluoro(5-ethyl-l,2,3,4-tetrahydronaphthalene) (56) and skeletal rearrangement to form per-fluoro(7-ethyl-l-methylindane) (57) when heated at 130 C in the presence of antimony(V) fluoride.48 At 170 -200 C, perfluoro(l,3.4-trimethylindane) (58) is formed. 

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