The Sulfone Group

The examples reported in this section provide clear evidence that free radical intramolecular addition to polar bonds occurs. These reactions may have genuine synthetic utility even when cyclization is followed by -scission of the (Cy ) radical. As most of the examples have been reported only recently, little is known concerning the scope of these reactions or of the origin of the selectivity of addition to one or the other terminus of the polar bond. It may be expected that features such as the nucleophilic or electrophilic character of the cyclizing radical must be taken into consideration along with the factors which govern intramolecular addition to C=C double bonds. 

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A polysulfone is characterized by the presence of the sulfone group as part of its repeating unit. Polysulfones may be aUphatic or aromatic. AUphatic polysulfones (R and are alkyl groups) were synthesized by radical-induced copolymerization of olefins and sulfur dioxide and characterized many years ago. However, they never demonstrated significant practical utiUty due to their relatively unattractive physical properties, not withstanding the low cost of their raw materials (1,2). The polysulfones discussed in this article are those based on an aromatic backbone stmcture. The term polysulfones is used almost exclusively to denote aromatic polysulfones. 

As a variation on the base-catalyzed nucleopbilic displacement chemistry described, polysulfones and other polyarylethers have been prepared by cuprous chloride-catalyzed polycondensation of aromatic dihydroxy compounds with aromatic dibromo compounds. The advantage of this route is that it does not require that the aromatic dibromo compound be activated by an electron-withdrawing group such as the sulfone group. Details of this polymerization method, known as the Ullmaim synthesis, have been described (8). 

The apphcation of bimolecular, nucleophilic substitution (S ) reactions to sucrose sulfonates has led to a number of deoxhalogeno derivatives. Selective displacement reactions of tosyl (79,85), mesyl (86), and tripsyl (84,87) derivatives of sucrose with different nucleophiles have been reported. The order of reactivity of the sulfonate groups in sucrose toward reaction has been found to be 6 > 6 > 4 > 1. ... 

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. 

An example of a sulfite ester made from thionyl chloride is the commercial iasecticide endosulfan [115-29-7]. A stepwise reaction of thionyl chloride with two different alcohols yields the commercial miticide, propaigite [2312-35-8] (189). Thionyl chloride also has appHcations as a co-reactant ia sulfonations and chlorosulfonations. A patent describes the use of thionyl chloride ia the preparation of a key iatermediate, bis(4-chlorophenyl) sulfone [80-07-9] which is used to make a commercial polysulfone engineering thermoplastic (see Polymers CONTAINING SULFUR, POLYSULFONe) (190). The sulfone group is derived from chlorosulfonic acid the thionyl chloride may be considered a co-reactant which removes water (see Sulfolanes and sulfones). 

Sulfonates. The sulfonate group, -SO M, attached to an alkyl, aryl, or alkylaryl hydrophobe, is a highly effective solubilising group. Sulfonic acid... 

Insoluble sulfonated pigments are made from colorants that contain a sulfonic acid group that is easily converted into an insoluble metal salt. In most cases, the sulfonic acid group is ortho to the diazo further reducing the solubilizing characteristics of the sulfonic grouping. The shade of these products is affected by the metal incorporated into the molecule and the physical characteristics of the colorants. D C Red Nos. 7 (19b) and 34 (26) are insoluble sulfonated pigments. 

The flask is then heated in an oil bath maintained at a temperature of 190-210° and the mixture subjected to steam distillation. The sulfonate groups are hydrolyzed in this process and the bromophenol passes over as a heavy, colorless or pale yellow oil. In about one hour the distillate is clear. The product is extracted with ether, the ether is removed by distillation from the steam bath, and the residue is distilled at atmospheric pressure (Note 3). The fraction boiling at 194-200° represents practically pure o-bromophenol. The yield is 70-75 g. (40-44 per cent of the theoretical amount) (Note 4). t -Bromophenol is a colorless liquid with a very characteristic odor. It is rather unstable and decomposes on standing, becoming brown or red in color. 

It was not until 1940 that the sulfonation of alkylisoxazoles by heating them with chlorosulfonic acid was reported. This gave a mixture of isoxazole-4-sulfonic acids (58) and their acid chlorides (59). The position of the sulfonic group in derivatives of monomethyl isoxazoles has been proved by nucleophilic cleavage of the isoxazole ring (60 61). Recently it proved possible to sulfonate isoxazole... 

Sulfo-. sulfo-, thio-. (Preferably, sulfo- is used to designate the sulfonic group, and thio to denote that sulfur replaces oxygen.) -azetat,... 

As in the acyclic series, there is a lengthening of the sulfur-oxygen bond as the sulfur is oxidized from the sulfoxide to the sulfone in both the thiirane (i.e. 16a - 17a) and the thiirene (i.e. 18a - 19b) series. Unexpected, however, is the substantial decrease in the OSO angle of the sulfone group in thiirenes compared with that of the thiiranes (e.g. dimethyl sulfone. There appears to be no simple explanation for this trend. 

Finally, the reaction of 19b with potassium fluoride in the presence of a crown-ether phase-transfer agent118 to yield the sulfonyl fluoride 67 and diphenylacetylene119 belongs to the same category in which a nucleophile (F in this case) attacks the electrophilic sulfur of the sulfone group (equation 19). 

The existence or nonexistence of conjugative effects involving the sulfone group in thiophene dioxides (a problem analogous to that in thiirene oxide and dioxide systems2,1 ) has been the subject of many studies resulting, nonetheless, in no unequivocal conclusion280. 

It has long been known that a, / -unsaturated sulfones resemble a, /i-unsaturated ketones and aldehydes in undergoing addition reactions with nucleophilic reagents43. These reactions are initiated by nucleophilic attack at the carbon to the sulfone group ... 

The stabilization of the carbanionic center on the a carbon atom by the sulfone group is no doubt an important factor promoting such reactions. Sulfoxides are capable of undergoing such reactions but are rather less prone to do so than sulfones. 

A cyclization of / -keto sulfone 17 in the presence of a Lewis acid gives a spirocycles via a pinacol-type rearrangement in which the sulfone group serves as a leaving group (equation 10)9. 

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