Antimony Fluoride rearrangement

Isomerization of fluoroolefins by a shift of a double bond is catalyzed by halide 10ns [7] The presence of crown ether makes this reaction more efficient [74] Prolonged reaction time favors the rearranged product with an internal double bond (equations 3-5) Isomerization of perfluoro-l-pentene with cesium fluoride yields perfluoro-2-pentenes in a Z ratio of 1 6 [75] Antimony pentafluoride also causes isomenzation of olefins leading to more substituted products [76]... 

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.). 

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... 

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. 

Perfluoro(2,2-dimethyloxirane) (1), which cannot rearrange to a ketone, gives the acyl fluoride 2 in the presence of antimony(V) fluoride.31... 

Trisubstituted perfluorooxirane 12 does not react with antimony(V) fluoride alone, even at 300 C. Reaction with the combination antimony(V) fluoride/perfluorotoluene, however, results in rearrangement to perfluorotetrahydrofuran 13 in good yield at only 100°C.48... 

Likewise, perfluoro(l-butyl-3-propyldiaziridine) (24) rearranges exothermically in the presence of antimony(V) fluoride to give perlluoro(dibutyldiazene) (25) in 84% yield.54... 

In the presence of antimony(V) fluoride, perfluorooxaziridines 30 rearrange by a completely different mode to form peril uoro(A/ -alkoxyimines) 32.57... 

Perfluoro ketones and perfluoro a-diketones, with a trifluoromethyl group in the -position to the carbonyl, cyclize in the presence of antimony(V) fluoride to give furan derivatives, as reviewed by Krcspan and Petrov.4 Perfluoro(4-methylpentan-2-one) (1) rearranges to per-fluoro(2,4-dimethyltetrahydrofuran) (2) in 84% yield, when heated in the presence of anti-mony(V) fluoride.5... 

In perfluoro a-diketone 7, which lacks a trifluoromethyl group /i to the carbonyl in the 2-position. it is the carbonyl in the 3-position that participates in the cyclization to form per-fluoro(2-acctyltetrahydrofuran) (8), when 7 is heated at 150 C in the presence of antimony(V) fluoride.5 Perfluoro(2-methyltetrahydropyran-3-one) also rearranges to furan derivative 8 in high yield when heated at 100 C in the presence of antimony(V) fluoride for 20 hours.5... 

Typical alkylation reactions are those of propane, isobutane, and n-butane by the ferf-butyl or sw-butyl ion. These systems are somewhat interconvertible by competing hydride transfer and rearrangement of the carbenium ions. The reactions were carried out using alkyl carbenium ion hexafluoroantimonate salts prepared from the corresponding halides and antimony pentafluoride in sulfuryl chloride fluoride solution and treating them in the same solvent with alkanes. The reagents were mixed at —78°C warmed up to — 20°C and quenched with ice water before analysis. The intermolecular hydride transfer between tertiary and secondary carbenium ions and alkanes is generally much faster than the alkylation reaction. Consequently, the alkylation products are also those derived from the new alkanes and carbenium ions formed in the hydride transfer reaction. 

Sulfides are selectively fluorinated a to the sulfur atom via a reaction similar to the Pummerer rearrangement (Table 2). The fluorination wa.s originally achieved by the direct fluorination of sulfides with xenon difluoride.This reaction is proposed to occur by initial oxidative fluorination of the sulfide to give an unstable sulfur(IV) difluoride of type 1, followed by loss of hydrogen fluoride to give intermediate 2, followed by fluorine transfer to give the a-fluoro sulfide. This fluorination has also been achieved with diethylaminosulfur trifluoride (DAST) in the absence or presence of catalytic amounts of antimony(III) chloride (see Vol. ElOa, pp 421-423). ... 

The reaction of several perhalogenated epoxides with antimony(V) fluoride gives ring-opened, rearranged products such as acid fluorides or perhalogenated ketones.117118... 

At lower temperatures in the presence of antimony pentafluoride, oxazrridine 334 rearranges to a different alkoxyimine, 337. A likely pathway for this transformation involves abstraction of a fluoride ion to form immonium ion 335 followed by or concerted with ring opening to carbocation 336, and then back donation of the fluoride. 

The reactions of perfluoroisobutene with sodium salts of malonic esters are difficult to control, owing to rearrangement and base catalysed cyclization, but when the complex BFs NEts is used as HF acceptor, condensation is readily controlled (see Scheme 15 and p. 99) and yields of up to 50% of allene (39) obtained. Antimony pentaliuoride catalyses the electrophilic addition of acid fluorides to 1,1-difluoro- and trifluoro-ethylene. Propiophenones, PhCO CHX-CFs (X = H or F), are obtained from benzoyl fluoride, but with acetyl fluoride, further condensation occurs, and trifluoroethylene yields the jS-diketone, CF3-CHF-CO-CH2Ac. ... 

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