Sulfur trioxide -dioxane complex

Sulfonation of the aromatic ring of l, 2, 2 -trifluorostyrene below 0 C does not give satisfactory yields with chlorosulfonic acid or a sulfur trioxide-dioxane complex Tar forms on heating In contrast, under similar conditions ipso substitution IS facile at the position of a trialkylsilyl or -stannyl group Thus, 4-trimethyl-silyl-T 2, 2 D-trifluorostyrene affords the corresponding trimethylsilyl sulfonate [20] (equation 9)... 

A reaction closely related to the [2 + 2] cycloaddition of thiocarbonyl S.S-dioxides is the addition of sulfur trioxide-dioxane complex to alkenes. This occurs stereoselectively and from (Z)- and (E)-2-butene the corresponding cis- and /ra .s -3,4-dimethyl-1,2-oxathietane 1,1-dioxides 11 are obtained121. 

The highly reactive sulfur trioxide-dioxan complex is effective for the terminal sulfonation of alkyl aryl ketones, for instance the reagent converts acetophenone (42) into the w-sulfonic acid (43) (Scheme 22) (see Chapter 2, p. 24). 

Aliphatic y-sultones and 8-sultones may be synthesised by the sulfonation of alkenes by reaction with the sulfur trioxide-dioxan complex or gaseous sulfur trioxide (Scheme 66). 

Sydnones contain the 1,2,3-oxadiazole ring they can be represented by a mesomeric betaine structure and 3-substituted sydnones may be sulfonated in the 4-position by treatment with sulfur trioxide-dioxan complex in dichloromethane at 20-40... 

Furan is resinified by sulfuric acid but it can be sulfonated with the complex of sulfur trioxide with pyridine or dioxane. Depending on conditions the 2-sulfonic or the 2,5-disulfonic acid may be obtained. Furan-2-carboxylic acid can be sulfonated with oleum. Benzo[6]furan is polymerized by sulfuric acid. The 2-sulfonic acid has been obtained by oxidation of the sulfinic acid available in turn by treatment of the lithio derivative with sulfur dioxide. Benzo[6]furan with the sulfur trioxide-pyridine complex allegedly affords the 3-sulfonic acid. 

The dioxane-sulfur trioxide complex reacts with 2,3-dimethylbutadiene to give the sultone... 

The complexes of sulfur trioxide with various nucleophiles (dioxane, pyridine etc.) are mild sulfonating reagents. Unlike other complexes of sulfur trioxide, dimethyl sulfide-sulfur trioxide readily adds to conjugated multiple bonds. Consequently, not only the sulfo group but also the dimethyl sulfide group add at the multiple bond. The reactions of dimethyl sulfide-sulfur trioxide complex with butadiene, isoprene and 2,3-dimethylbutadiene take place as conjugated l,4- -additions of dimethyl sulfide and sulfonate groups at the double bonds of the diene (equation 103).124... 

Air. Like all other ethers, dioxane forms explosive peroxides on exposure to air and these may be hazardous if the dioxane is distilled. Since dioxane is miscible with water, peroxides should be removed by passing the liquid through a column of activated alumina. The alumina should be washed with water or methanol before being discarded.4 Nickel. Dioxane reacts almost explosively with Raney nickel above 210°C.5 Sulfur Trioxide. The addition complex with sulfur trioxide decomposes violently on storage.6... 

Sulfonation at C-4 can be accomplished with sulfur trioxide complexed with dioxane. Chlorosulfonic acid introduces the sulfonyl chloride group into the ring from which esters and sulfonamides can be made (79AP977,81AP470, 503). 

The reaction of alkenes with sulfur trioxide is an important synthesis of 1,2-oxathiolane 2,2-dioxides. The best conditions involve the use of a dioxane-sulfur trioxide complex at low temperature. The initial addition involves formation of the most stable cation followed by ring closure, as shown in Scheme 31 (74JOC2459). 

Using sulfur trioxide complexes with pyridine, dioxane, iV,iV-dimethyl-aniline, or bis(2-chloroethyl) ether, sulfated chitins have also been prepared for use as thickeners in pastes, adhesives, and drilling muds. ... 

Related to, but quite distinct in purpose from, the usual notions of masking is the use of coordination to moderate the action of a very vigorous Lewis acid. An example of this may be seen in the use of the pyridine and dioxane complexes of sulfur trioxide in place of the parent compound 19), Because the complexes used here must release sulfur trioxide to other reactants, it is imperative that no reaction beyond coordination occurs. Thus, pyridine reacts only to give the adduct below. 

Sulfur trioxide as the dioxan complex will also sulfonate aldehydes and ketones containing reactive a-methylene hydrogen atoms (Scheme 25). 

Sulfonic acids. Complexes of sulfur trioxide have been used to introduce the SO3H group to organic molecules. For example, organolithium reagents are converted to sulfonic acids by the trimethylamine complex and the dioxane complex is useful for replacing a silyl... 

Preparation. Rondestvedt and BordwelF cooled 800 g. of ethylene dichloride and distilled in sulfur trioxide from 60% fuming sulfuric acid or Sulfan B to a gain in weight of 300 g. The sulfur trioxide solution was cooled below —5°, and dioxane equivalent to the sulfur trioxide was added dropwise with stirring, when the complex separated as fine granules. This complex is much more reactive than sulfur trioxide-pyridine it is hydrolyzed by cold water. 

Sulfur trioxide, SOj. Mol. wt 80.07, m.p. 17°, b.p. about 45°. This reagent is available from the General Chemical Division, Allied Chemical and Dye Corp., under the name Sulfan B, a -y-form stabilized with an inhibitor to prevent polymerization. It is used in organic work chiefly in the form of complexes with dioxane, dimethylformamide, and pyridine. 

A-Phosphorylated imidazoles and benzimidazoles can be made by direct phosphorylation by halides, esters, amides, amidoesters, isocyanates, and thiocyanates of phosphorus-containing acids, or from reaction of phosphonic or phosphinic imidazolides with a sulfonic acid or anhydride <82CB1636>. Stable charge transfer complexes are produced when a 1 1 or 1 2 ratio of imidazole (or benzimidazole) and sulfur trioxide are refluxed in ether, dioxane, THE, or 1,2-dichloroethane. These complexes are stable on storage in the absence of water and have sharp melting points. Indeed, the benzimidazole SO3 complex must be boiled for five hours in water to decompose it. On fusion, the complexes form the C-sulfonic acids (see Section 3.02.5.3.3) <87CHE1084>. Sulfonyl chlorides readily A-sulfonate imidazoles <94JMC332>. 

Aromatic hydrocarbons such as toluene, xylenes, mesitylene, and methyl-naphthalenes can be sulfonated in dichloroethane almost quantitatively by the dioxan-sulfur trioxide complex under very mild conditions (2 h at 20°).179... 

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-... 

Generally, sulfur trioxide reacts with hydrocarbon olefins quite vigorously and has to be either diluted or used in complexes with pyridine or dioxane to moderate its reactivity. The corresponding cycloadducts, p-sultones, easily undergo ring opening and have not yet been isolated. In sharp contrast, fluorinated p-sultones are relatively stable materials and over 50 compounds of this type have been prepared and isolated. Synthesis and chemistry of this class of heterocycles is well documented and has been previously reviewed. ... 

When polystyrene is sulfonated in chlorinated hydrocarbons with a complex of dioxane-SOs, the polymer precipitates from solution at low concentrations. Complexes of ketones with SO3 can also be used to sulfonate polystyrene in halogenated solvents. The ratio of sulfonation is more favorable for poly(vinyl toluene) than it is for polystyrene at the same conditions. Also, sulfur dioxide swells polystyrene. The polymer can be sulfonated in this medium with sulfur trioxide or with chlorosulfonic acid. Polystyrene, sulfonated in CS2 with aluminum chloride catalyst, is water insoluble in a free acid form. ... 

Different sulfonating agents have been used for the a sulfonation of fatty acids and their esters stabilized liquid SO3, sulfur trioxide vapor, chlorosul-fonic acid, and dioxane-sulfur trioxide complex. Stirton tried all of them and preferred liquid SO3. The other agents are used for special applications [29]. 

The reaction of olefins with SO3 is exothermic, and often only secondary reaction products are isolated. Attempts to control the cycloaddition reaction involve the use of dioxane- or pyridine-S03 complexes. However, to generate the monomer from the cyclic trimer, freshly distilled SO3 at low temperatures is more effective. Also, oleum seem to have an advantage over the pure sulfur trioxide in [2+2] cycloaddition reactions. ... 

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