Sulfonyl fluorides, from sulfonamides

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

The ECF process has been used by the 3M Company since around 1947 [4]. Primarily, ECF was used to produce PFOA and a line of perfluorooctane sulfonyl fluoride (PFOSF)-based products including PFOS andperfluorooctyl sulfonamides. However, in 2000, the 3M Company announced that it would be phasing out its line of perfluorooctyl products from 2001 to 2003 [10]. These products have since been replaced by analogous butyl-based substances [11], including the perfluorobutyl sulfonamides produced using the ECF process. 

A good measure of past and continuing interest in ionomer membranes issued from the development of perfluorinated ionomers, the first-announced being Nafion(44). These materials are characterized by remarkable chemical resistance, thermal stability and mechanical strength, and they have a very strong acid strength, even in the carboxylic acid form. The functionalities that have been considered include carboxylate, sulfonate, and sulfonamide, the latter resulting from the reactions of amines with the sulfonyl fluoride precursor. 

The N-SES group can be incorporated by treating an aldehyde with iV-sulfinyl-/3-trimethylsilylethanesulfonamide (SESNSO) (13), which can be made by treating the sulfonamide (12) with thionyl chloride and a catalytic amount of M,fV-dichloro-/7-toluenesulfonamide (eq 7) (see also fV-sulfinyl-/7-toluenesulfon-amide. The iV-sulfonyl imine can be used in situ in a number of reactions. For example, the fV-sulfonyl imine from aldehyde (14) reacts with 2,3-dimethylbutadiene (eq 8) to give the Diels-Alder adduct (15). Treatment of (15) with fluoride ion affords the bicycUc lactam (16). Also, the fV-sulfonyl imine derived from isobutyraldehyde and (13) reacts with vinylmagnesium bromide to provide the allylic SES-sutfonamide (17) in 65% yield (eq 9). ... 

An example of fluoride induced conversion is of a hetaryl 2-(trimethylsilyl)ethyl sulfone to the sulfinic acid via protonation of the sulfinate anion. The treatment of a collection of arenesulfinate anions, obtained from the corresponding 2-(trimethylsilyl)ethyl sulfones, with H2NOSO3H gave aryl sulfonamides in 50-85% yield (eq 13). In this case and elsewhere, the aryl 2-(trimethylsilyl)ethyl sulfones are prepared through the deprotonation of aryl methyl sulfones and quenching of the a-sulfonyl carbanion with trimethylsilylmethyl iodide, or the less expensive trimethylsilylmethyl chloride. Such a protocol is complementary to the oxidation of 2-(trimethylsilyl)ethyl thioethers. 

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