Sultones rearrangement

Sulfur tnoxide adds to 2,2 difluoroethylenesulfonyl fluoride to afford the P sultone and its rearrangement product, bis(fluorosulfonyl)acetyl fluoride Potassium fluoride acts as a base and reacts with the acetyl fluoride to eliminate the elements of hydrogen fluoride and produce bis(fluorosulfonyl)ketene [IS] (equation 6)... 

Molecular rearrangements such as that of Stevens248,265 or the sulfoxide - sulfinic acid, Ramberg-Backlund15 or sultone -> sultine rearrangements, are quite common in these classes of compounds. 

The actual sulfonation reaction consists largely of a concerted 2+2 cyclo addition of S03 and a-olefin yielding a highly reactive, unstable p or 1,2-sultone that can (1) react further to give alkenesulfonic acid and (2) rearrange itself to form y- or 1,3-sultone (a fast reaction), and 8- or 1,4-sultone (a slow reaction). Possible side reactions have been identified by Bakker and Cerfontain [28]. At molar ratios of S03/olefin below 1.0 the major sulfonation product is 1,3-sultone but larger proportions of alkenesulfonic acids will be formed for ratios... 

From a process point of view, the direct neutralization is clearly preferred moreover, the product quality (color) and free oil content deteriorates with aging (Table lb). The fact that the free oil and the inorganic sulfate level increase simultaneously upon aging is due to the fact that the formation of p-sultones from olefins is a reversible reaction [28], in competition with thermal rearrangement to alkenesulfonic acid and y- and 8-sultone. The effects of the reverse reaction of p-sultones are less with AOS because the rearrangement rates of AO-derived sultones are higher [29,35]. 

A novel thermal rearrangement with loss of sulfur dioxide leading to the stilbene or styrene derivatives 169 and 170 in highly stereospecific manner was carried out by heating (in dioxane, DMSO, dioxane-water or THF) the sulfene-tropone adducts (y-sultones) 167 or 168 (equations 51 and 52)68. 

An interesting seleno derivative in 42% yield can be obtained by treating 3-trichloromethyl 9-sultone with selenoethylurea in triethylamine (283). At 25 °C the compound 284 undergoes rearrangement to the open structure 285." ... 

A fascinating rearrangement ending into chromenes is the thermally allowed disrotatory (4n + 2)n closure of the sultone (59) to a non-... 

The /J-sultones 3 are readily formed by the addition of sulfur trioxide to polyfluorinated al-kenes.45,46 They are the building blocks of DuPont s Nation membranes.52 Possible mechanisms for the rearrangement have been proposed,45,46,53,54 which all involve initial attack of the nucleophile at the sulfur atom with ring opening at the S-O bond. 

The interaction of sulfur trioxide with polyfluorinated vinyl ethers proceeds without a catalyst at low temperature to give /f-sultones. At higher temperature, sultones readily rearrange into the more stable acyl fluoride 91 or alkyl F-alkyl-/3-ketosulfonates. 92,93a-b [181] ... 

A limited number of rearrangements/isomerizations were reported in the previous version of this chapter. Again little has been done in this area of research over the past decade. The most common isomerization involves the ring expansion of /3-sultoncs into 7-sultones and is illustrated by the example below (Scheme 6) <1999TL7417>. Thus, treatment of 1-hexene with sulfur trioxide produced the 7-sultone 33 in 68% yield after isomerization of the unstable /3-sultone 34. 

Oxathietane 2,2-dioxides (-sultones) are prepared by [2 + 2] cycloaddition of sulfur trioxide to alkenes (e.g., Scheme 27) . Likewise, acid-catalyzed rearrangement of l,l-diphenyl-2,2-dimethylpropanol in the presence of sulfur trioxide forms a stable 1,2-oxathietane 2,2-dioxide (Scheme 28) < 1977J (Pl)247>. 

CH2OH and the sultone F5S d)FCF20 02 265). Mechanistically, the sodium fluoride, the alcohol, or both serve as a catalyst for the rearrangement of the sultone (265,266). The esters formed in this fashion are stable in the presence of F ion at ambient or higher temperatures. The spectral data (IR H, 19F, and 13C NMR and mass) for these... 

The formation of the sultone (160) probably involves addition of the complex across the alkene double bond, a 1,2-hydride shift and an intramolecular nucleophilic substitution reaction. The sultone (161) is formed by addition of sulfur trioxide to give the unstable p-sultone which rearranges to the more stable y-isomer (161). Another useful route to sultones is by metallation of alkanesulfonate esters for example, butane-1,3-dimethylsulfonate (162), prepared from butanel,3-diol, yields the 8-sultone, namely 6-methyl-l,2-oxathiin-2,2-dioxide (163) (Scheme 67). 

The hydrolysis of the tropolone methyl ether 360 with concentrated HCl in boiling EtOH results in the hydroxyfluorenone 361 (equation 172) °. Thermal rearrangement with loss of sulfur dioxide occurs on heating the y-sultones 362 in dioxane, DMSO, dioxane-water or THE at 90 °C for 6-10 h to give 90% of the styrene derivatives 363 in a highly stereospecific manner (equation 173). ... 

Sulfur trioxide reacts with bicyclopropylidene at — 60°C the initial [2 + 2] cycloadduct 25, however, rearranges rapidly to the sultone 26, which can be isolated in virtually quantitative yield. ... 

Olefins react with SO3 under free-radical conditions to afford cyclic sulfonate esters, i.e., sultones.The initially formed products are believed to be the highly strained 1,2-adducts, which then rearrange to the 1,3-adducts. This is the commercial route to propanesultone. 

Tetrafluorethylene reacts with SO3 to form a cyclic sultone. After rearrangement, the sultone can then be reacted with hexa-fluoropropylene epoxide to produce sulfonyl fluoride adducts, where... 

Cava and Sehlessinger have reported the synthesis of 1,2,3-triphenyl-isoindole (65) in 78% yield from 1,3-diphenylisobenzofuran (68) by reaction with thionylaniline (69) and boron trifluoride.61 The mechanism proposed for this remarkable transformation involves rearrangement of the adduct (70) derived from thionylaniline and the isobenzofuran, to the tricyclic intermediate (71). This presumably collapses to the S-sultam (72), which yields the isoindole (65) upon extrusion of sulfur dioxide. Loss of sulfur dioxide, both from S-sultones and unsaturated S-sultams, is well documented.62 63... 

A wide range of amines and their derivatives have been shown to react with both saturated and unsaturated aliphatic sultones to produce the corresponding aminosulph-onic acids (equation 109)166. Amines and their derivatives react rapidly with fluorinated / -sultones to form rearrangement products (equation 110)86. 

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