Fluorosulfonates

Triflates are used for the reaction[470]. The 5-phenyltropone 609 is prepared by coupling of the triflate with phenylzinc chloride[471]. Instead of the expensive triflale, phenyl fluoroalkanesulfonate as a triflate equivalent is used for coupling[472]. Phenyl fluorosulfonate (610) is another reagent used for cou-pling[473]. 

For coupling, the cheaper aryl fluorosulfonate 713 is used as an alternative to the expensive aryl triflates to give the same results[473]. The arenesulfonates 714 are active for the reaction with vinylstannanes when dppp and LiCI are used in DMSO[583], The bromide 715 attacks the arylstannane moiety selectively without reacting with the organoboron moiety in 716 in the absence of a base[584]. 

Arsenic pentafluoride can be prepared by reaction of fluorine and arsenic trifluoride or arsenic from the reaction of NF O and As (16) from the reaction of Ca(FS02)2 and H AsO (17) or by reaction of alkaH metal or alkaline-earth metal fluorides or fluorosulfonates with H AsO or H2ASO2F (18). 

Hexafluoroarsenic acid [17068-85-8] can be prepared by the reaction of arsenic acid with hydrofluoric acid or calcium fluorosulfate (29) and with alkaH or alkaline-earth metal fluorides or fluorosulfonates (18). The hexafluoroarsenates can be prepared directly from arsenates and hydrofluoric acid, or by neutrali2ation of HAsF. The reaction of 48% HF with potassium dihydrogen arsenate(V), KH2ASO4, gives potassium hydroxypentafluoroarsenate(V)... 

In another process fluorosulfonic acid is treated with boric acid ... 

The stmcture of the ketones produced from unsymmetrical internal perfluoroepoxides has been reported (5). The epoxide ring may also be opened by strong protic acids such as fluorosulfonic acid or hydrogen fluoride at elevated temperatures (23—25). The ring opening of HFPO by sulfur trioxide at 150°C has been interpreted as an example of an electrophilic reaction (26) (eq. 3). 

The first member of the series, CF SO H, has been extensively studied. Trifluoromethanesulfonic acid [1493-13-6] is a stable, hydroscopic Hquid which fumes in air. Addition of an equimolar amount of water to the acid results in a stable, distillable monohydrate, mp 34°C, bp 96°C at 0.13 kPa (1 mm Hg) (18). Measurement of conductivity of strong acids in acetic acid has shown the acid to be one of the strongest protic acids known, similar to fluorosulfonic and perchloric acid (19). 

THE can be polymerized by many strongly acidic catalysts, but not all of them produce the requked bitimctional polyether glycol with a minimum of by-products. Several large-scale commercial polymerization processes are based on fluorosulfonic acid, HESO, catalysis, which meets all these requkements. The catalyst is added to THE at low temperatures and an exothermic polymerization occurs readily. The polymerization products are poly(tetramethylene ether) chains with sulfate ester groups (8). 

Sulfur dichloride reacts with hexafluoropropene ia the presence of fluorosulfonic acid at 30—60°C to give the foUowiag (161) ... 

Arsenic trifluoride (arsenic(III) fluoride), AsF, can be prepared by reaction of arsenic trioxide with a mixture of sulfuric acid and calcium fluoride or even better with fluorosulfonic acid. Chlorine reacts with ice-cold arsenic trifluoride to produce a hygroscopic soHd compound, arsenic dichloride trifluoride [14933-43-8] ASCI2F35 consisting of AsQ. and AsF ions (21). Arsenic trifluoride forms a stable adduct, 2AsF2 SSO, with sulfur trioxide and reacts with nitrosyl fluoride to give nitrosonium hexafluoroarsenate(V) [18535-07-4] [NO][AsFg]. 

The principal electrophiles to attack ring sulfur are either oxidants or alkylating reagents. Thiophene sulfoxide and sulfone formation is discussed in Section 3.02.2.6. Alkylating agents capable of forming thiophenium salts include trimethyloxonium tetrafluoroborate (MeaO BF ) and alkyl fluorosulfonates (ROSO2F). The salts e.g. 87) are conveniently isolated as hexafluorophosphates (88). 

For both azole and benzazole rings the introduction of further heteroatoms into the ring affects the ease of quaternization. In series with the same number and orientation of heteroatoms, rate constants increase in the order X = 0requires stronger reagents and conditions methyl fluorosulfonate is sometimes used (78AHC(22)71). The 1-or 2-substituted 1,2,3-triazoles are difficult to alkylate, but methyl fluorosulfonate succeeds (7IACS2087). 

Acids are poor catalysts for ring cleavage of thiirane 1,1-dioxides but are good catalysts for reactions of thiirane 1-oxides with nucleophiles. These reactions of episulfoxides are believed to proceed by protonation of the oxygen atom (but see the NMR evidence cited above for 5-protonation in fluorosulfonic acid) and will be treated in the section on nucleophilic reactions. 

Halide ions may attack 5-substituted thiiranium ions at three sites the sulfur atom (Section 5.06.3.4.5), a ring carbon atom or an 5-alkyl carbon atom. In the highly sterically hindered salt (46) attack occurs only on sulfur (Scheme 62) or the S-methyl group (Scheme 89). The demethylation of (46) by bromide and chloride ion is the only example of attack on the carbon atom of the sulfur substituent in any thiiranium salt (78CC630). Iodide and fluoride ion (the latter in the presence of a crown ether) prefer to attack the sulfur atom of (46). cis-l-Methyl-2,3-di-t-butylthiiranium fluorosulfonate, despite being somewhat hindered, nevertheless is attacked at a ring carbon atom by chloride and bromide ions. The trans isomer could not be prepared its behavior to nucleophiles is therefore unknown (74JA3146). 

Thiophenium fluorosulfonate, 1,2,3,4,5-tetramethy 1-ylide, 4, 724 Thiophenium salts aromaticity, 4, 724 proton abstraction, 4, 766 pyramidal inversion barrier, 4, 724 structure, 4, 715 synthesis, 4, 723-724 Thiophenium salts, 1-alkyl-solvolysis, 4, 766 UV spectra, 4, 766 Thiophenium salts, aryl-synthesis, 4, 726... 

When the alcohol 1 is dissolved in fluorosulfonic acid at — 136°C and then allowed to warm to — 110°C, it gives rise to a cation having a C-NMR spectmm consisting of five lines in the intensity ratio 2 1 2 2 2. Suggest possible stmctures for this cation, and discuss any stabilizing features which might favor a particular stmcture. 

Chemical Designations - Synonyms Fluorosuliiiric acid, Fluorosulfonic acid Chemical Formula FSO3H. 

Most frequent are oxidations of alkenes that can be converted to a series of compounds such as epoxides, halohydnns and their esters, ozonides (1,2,4 tri-oxolanes), a-hydroxyketones, a-hydroxyketone fluorosulfonates, ot-diketones, and carboxylic acids and their denvatives... 

The monofluoromethylene group and difluoromethyl group m 1H perfluoro-alkanes and -cycloalkanes are oxidized at the C-H bond to perfluoroalkyl and perfluorocycloalkyl fluorosulfates by anodic oxidation m fluorosulfonic acid [J, 4] Two modifications of the method are used ox idation by fluorosulfonyl peroxide generated pnor to the reaction [J] (equation 2A) and direct electrolysis m the acid [i, 4] (equabons 2B and 3)... 

Hexafluoropropene is converted to its 1,2-epoxide in 55% yield by bubbling through a solution of chromium tnoxide in fluorosulfonic acid [8], the analogous reaction with a mixture of chromium trioxide and dichromium tnoxide gives pentafluoroacetonyl fluorosulfate [.5] (equation 6)... 

Electrochemical oxidation of oi-hydrogenperfluoro- and perfluorocarboxyhc acids in fluorosulfonic acid gives fluoroalkylfiuorosulfates [i] (equation 71). 

Perfluoroallyl fluorosulfonate is converted to perfluoroallyl bromide or iodide in 56 or 75% yield, respectively, by reaction with the potassium halide in mono-glyme at room temperature [S5]... 

Nitronium fluorosulfate in fluorosulfonic acid adds electrophilically across the double bond offluoroolefins in a nonspecific manner. Tnfluorochloroethylene reacts accordingly with nitronium fluorosulfate to give a 2.1 mixture of regio-isomers [7] (equation 7). Under these reaction conditions perfluoropropylene is unreactive even after extended heating at 80 C 2-Nitroperfluoropropyl fluorosulfate is obtained on treatment of the perfluoropropylene with nitronium fluorosulfate in antimony pentafluoride [5] (equation 8). 

Octafluoroisobtttylene, whose double bond has reduced electron density and limited accessibility, reacts with sulfur tnoxidg under vigorous conditions The reaction mixture contains various components including bis-oi-tnfluorometh-yldifluoroethane-P-sultone, bis(a-trifluoromethyldifluoroethane)-(i-pyrosultone, the heptafluoroisobutenyl ester of fluorosulfonic acid, and the heptafluoroiso-butenyl ester of fluoropyrosulfomc acid [73] (equation 4)... 

The preparation of trifluoromethyl trifluoromethanesulfonate was reported by Olah and Ohyama [29]. In this safe and practical method, trifluoromethanesulfonic acid and fluorosulfonic acid are used [29] (equation 27). 

In general, fluorinated sulfonic acids can be used as eatalysts for various cationic cyclizations Typical examples are the triflic acid catalysis in the double cyclization of A,VV-dibenzylpropynylamine [82] (equation 30) and the fluorosulfonic acid catalyzed condensation of phenylacetaldehyde [<5J] (equation 31)... 

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