Arenesulfonic anhydrides

Arenesulfonic anhydrides can be obtained by removal of water from the sulfonic acids by thionyl chloride according to directions given by Meyer et al129 Phosphorus pentaoxide,730 di-/ -tolylcarbodiimide,731 or aryl cya-nates732 may also be used for this purpose. 

General Reactions. Arenesulfonic anhydrides have been used as precursors for a variety of substituted sulfones, sulfonate esters, and sulfonamides. The Friedel-Crafts reaction of benzenesulfonic anhydride and benzene in the presence of AICI3 provided diphenyl sulfone in 99% yield (eq 1). This has proved to be milder and more efficient than the similar reaction using benzenesulfonyl chloride. ... 

Azoxybenzene is known to rearrange in concentrated sulfuric acid to />-hydroxyazobenzene. This acid-catalyzed Wallach rearrangement has been extended by using arenesulfonic anhydrides to furnish the corresponding /rarenesulfonyl-oxyazobenzenes in reasonable yields (eq 2). ... 

Solvolysis of Benzenesulfonic Anhydride. Solvolysis of various arenesulfonic anhydrides in aqueous acetone revealed the reaction mechanism to be Sn2 in accord with established results for similar systems. ... 

Tetrabutylammonium iodide in trifluoroacetic anhydride is an effective reducing reagent [dS] This system can be used for direct reduction of arenesulfonic acids to the corresponding thiols or disulfides m moderate yields under mild conditions (equation 18) Alkanesulfonic acids are reduced by this system to disulfides with 30-57% yields [dfi]... 

An important role must be attributed to intermediate mixed anhydrides of sulfonic acids and mineral acids sulfonic acid anhydrides are reported to need Friedel-Crafts conditions to generate sulfones327,476. Instead of arenesulfonic acids, their methyl esters may undergo insertion of sulfur trioxide477,478 yielding mixed anhydrides, which in turn furnish... 

It is reasonable to relate the values of k+fk at least qualitatively to the extents of bond making and breaking in the transition state. Bond making is all important in hydrolyses of carboxylic anhydrides, diaryl carbonates and methyl arenesulfonates. Bond breaking will be important in hydrolyses of alkyl halides and sulfonates, except for methyl derivatives, and especially so in water which can effectively solvate the leaving anion. 

Conversion of alcohols to sulfonate esters is a way of labilising them to nucleophilic substitution and elimination. The common leaving groups are arenesulfonates, particularly p-toluenesulfonate (tosylate), methanesulfonates (mesylate) and trifluromethanesulfonate (triflate) they are introduced by reaction of the acid chlorides (or, in the case of the trifluoromethanesulfonates, acid anhydrides) in a basic solvent such as pyridine. Traditionally, the reactions are carried out in pyridine as solvent, but both this solvent and the liberated... 

Aromatic Sulfonation. Reaction of an arene (ArH) with SO3 leads to sulfonation with formation of arenesulfonic acids (ArSOsH). Mechanistically two different stages can be recognized, viz. primary and secondary sulfonation. In the primary stage, arenepyrosulfonic acids (ArS206H) are formed. A pyrosulfonic acid is a mixed anhydride, liable to disproportionate... 

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