Sulfur trioxide insertion reaction

This peculiar reaction seems to be an insertion of sulfur trioxide between the carbon and fluorine atoms in the trifluoromethyl group. The product is perfluorobenzyl fluorosulfate [48, 49J. 

The reaction of terminal fluoro olefins with SO3 at low temperatures affords the [2+2] cycloadducts in good yields. Examples of this type of reaction are listed in Table 7.4. However, insertion of sulfur trioxide into allylic C-F bonds often occurs simultaneously . ... 

The reaction involves initial insertion of sulfur trioxide into the nitrogen-silicon bond of anilinotrimethylsilane 466 the sulfamic acid 467 was, however, contaminated with small amounts of anilinium salts. It was discovered that the reaction of anilinotrimethylsilane 466 with trimethylsilyl chlorosulfonate 459 gave improved yields of the pure sulfamic acid 467. Trimethylsilyl chlorosulfonate 459 will effect the sulfosilation of aromatic hydrocarbons to give the trimethylsilyl arenesulfonates 468 (Equation 148). 

Methyl polyfluoro-1-cyclobutenyl ethers react with sulfur trioxide to form fluoride and polyfluorocyclobutenones, but coproducts are their fluorosulfonyloxy derivatives resulting from sulfur trioxide insertion [5] (equation 5) The nonsul-fonyloxylated polyfluorocyclopentenones are favored when starting with methyl polyfluoro-1-cyclopentenyl ethers (equation 6). Ring insertion of sulfur tnoxide occurs during the reaction of 1-methoxytnfluorocyclopropene (equation 7)... 

In the first step an S03 molecule is inserted into the ester binding and a mixed anhydride of the sulfuric acid (I) is formed. The anhydride is in a very fast equilibrium with its cyclic enol form (II), whose double bonding is attacked by a second molecule of sulfur trioxide in a fast electrophilic addition (III and IV). In the second slower step, the a-sulfonated anhydride is rearranged into the ester sulfonate and releases one molecule of S03, which in turn sulfonates a new molecule of the fatty acid ester. The real sulfonation agent of the acid ester is not the sulfur trioxide but the initially formed sulfonated anhydride. In their detailed analysis of the different steps and intermediates of the sulfonation reaction, Schmid et al. showed that the mechanism presented by Smith and Stirton [31] is the correct one. 

Sulfur trioxide, at —10°C in OFCI3 solution, undergoes an insertion reaction to yield the orange solid (mp = 27°C) CIO2OSO2F (254). The same compound was also obtained (296) in the absence of a solvent ... 

Insertions of carbon dioxide, sulfur dioxide, and sulfur trioxide yield aluminum carboxylates, sulfinates, and sulfonates, respectively. Treatment of the resulting complexes with aqueous acid yields the corresponding aUcylcarboxylic, alkylsulphinic, and aUcylsulphonic acids. High pressure and temperatures of 220-240 °C are required for multiple insertions of CO2 to yield more than one equivalent of carboxyhc acid per aluminum. Excess aluminum trialkyl must be avoided or the initially formed carboxylate is completely alkylated to a trialkylcarbinol. Reaction of Ets A1 with CO2, for example, gives a 90% yield of triethylcarbinol. 

Topics of this section include 1,2-insertion reactions of acetylenes (b), olefins (c), allenes (d), oxygen (e), carbon dioxide (f), sulfur dioxide (g), sulfur trioxide (h), and nitric oxide (i). 

Insertion Reactions of Carbon Dioxide, Sulfur Dioxide, and Sulfur TrIoxide... 

Sulfur trioxide is a strong Lewis acid and an oxidant. Insertions into element-carbon bonds to yield alkylsulfonates [reaction (k)] are known for E = Li , AH , Si , Hg °, Sn i and Ge ... 

Insertion Reactions into Element Oxygen and Heavier Group VIB Bonds 11.5.5. Sulfur Dioxide, Sulfur Trioxide, Sulfodiimides, and Sulfinylamines... 

Insertion reaction with silyl azides. Sulfur trioxide (as the 1 1 complex with dioxane) undergoes insertion with silyl azides and with compounds having a tri-... 

The addition of catalytic amount of a Lewis acid, such as BF3, completely changes the course of the reaction of hexafluoropropene and sulfur trioxide. Allyl fluorosulfate 30 (rather than sultone 23) is the major product of the reaction in this case. The proposed mechanism of this reaction involves the formation of fluor-osulfated boron fluoride intermediate by abstracting an allylic fluorine from hexafluoropropene to form the perfluoroallyl cation, which is further stabilized by addition of -OSO2F group affording 30 (Scheme 2.15). It should be pointed out, however, that the concerted mechanism of SO3 insertion into allylic C-F bond of CF3 group also cannot be ruled out. 

Reaction of an alkene with an excess of SO3 gives a cyclic sulfonate-sulfate anhydride, also referred to as carbyl sulfate or pyrosulfate (eq 5). This carbyl sulfate is formed by a slow insertion of SO3 into the intermediate -sultone. The complex of sulfur trioxIde with dimethyl sulfide reacts with alkenes and alkynes to afford sulfobetaines in good yields (eq 6). These sulfobetaines are produced by nucleophilic attack of the dimethyl sulfide on the initially formed -sultones. 

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