Sulfonyl fluorides, reaction with aromatic

In 1927 Steinkopf reported the preparation of several aromatic sulfonyl fluorides (287). For example, he obtained benzene sulfonyl fluoride, C6H6S02F, by the slow addition of fluorosulfonic acid to benzene at about 20°. The crude product was poured over ice and was then extracted in ether. After evaporating the ether, the benzene sulfonyl fluoride was refined by steam distillation. Another method for preparing aromatic sulfonyl fluorides is by the reaction of an aromatic sulfonic acid, such as C6H6S03H, with fluorosulfonic acid (202). By boiling a mixture of an aromatic sulfonyl chloride with a concentrated solution of potassium fluoride in water, the chloride is converted to a fluoride (62). 

Sulfonylation. Under Friedel-Crafts reaction conditions, sulfonyl haUdes and sulfonic acid anhydrides sulfonylate aromatics (139), a reaction that can be considered the analogue of the related acylation with acyl haUdes and anhydrides. The products are sulfones. Sulfonyl chlorides are the most frequently used reagents, although the bromides and fluorides also react ... 

The Friedel-Crafts sulfonylation of aromatics with alkane- and arenesulfonyl halides and anhydrides has been studied (Eq. 9) [23]. In the reaction of pentafluorobenzenesul-fonyl fluoride with pentafluorobenzene, decafluorodiphenyl sulfone is formed with deca-fluorodiphenyl [23c]. Certain phenylacetylenes react with SO2 and benzene in the presence of SbFs to form benzothiophene 5-oxide [24]. (Eq. 10). Sulfinyl fluoride reacts similarly with arenes under SbFs catalysis to give sulfoxides (Eq. 11) [25]. 

We have begun examining Route A using a niline (19) as a model for 7 (Scheme 6). Reaction of 19 with commercially available 4-fluorobenzene-sulfonylchloride (6) gave 20 in 90% yield. Compound 20 results from selective reaction at the sulfonyl chloride in the presence of the aromatic fluoride. The temperature of the reaction was cmcial for success at 40°C, a mixture of 20 and 21 was obtained, but at 0°C, only 20 was formed. Compound 21 arises from a double addition of an iline. This latter reaction gives us reason to believe that the nucleophilic aromatic substitution needed to prepare our key model compound 22, representing 17 in Route A (Scheme 5), will be possible. 

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