Sulfonic anhydrides

Sulfonic acids may be subjected to a variety of transformation conditions, as shown in Figure 2. Sulfonic acids can be used to produce sulfonic anhydrides by treatment with a dehydrating agent, such as thionyl chloride [7719-09-7J. This transformation is also accomphshed using phosphoms pentoxide [1314-56-3J. Sulfonic anhydrides, particulady aromatic sulfonic anhydrides, are often produced in situ during sulfonation with sulfur trioxide. Under dehydrating conditions, sulfonic acids react with substituted aromatic compounds to give sulfone derivatives. 

These authors suggest that the reaction may proceed through the formation of their mixed anhydrides , and illustrate a metal ion templated, mixed carboxylic-sulfonic anhydride. 

Sulfur compounds have also been widely studied as activating agents for polyesterification reactions. p-Toluenesulfonyl chloride (tosyl chloride) reacts with DMF in pyridine to form a Vilsmeir adduct which easily reacts with carboxylic acids at 100-120° C, giving highly reactive mixed carboxylic-sulfonic anhydrides.312 The reaction is efficient both for aromatic dicarboxylic acid-bisphenol312 and hydroxybenzoic acid314 polyesterifications (Scheme 2.31). The formation of phenyl tosylates as significant side products of this reaction has been reported.315... 

Carboxylic-sulfonic anhydrides, 80 Cardiovascular surgery, 27 Cardo diamines, 277, 278 Carothers, Wallace, 198 Carothers equation, 11, 59 Carothers group, 1 Carpet waste... 

In the first step an S03 molecule is inserted into the ester binding and a mixed anhydride of the sulfuric acid (I) is formed. The anhydride is in a very fast equilibrium with its cyclic enol form (II), whose double bonding is attacked by a second molecule of sulfur trioxide in a fast electrophilic addition (III and IV). In the second slower step, the a-sulfonated anhydride is rearranged into the ester sulfonate and releases one molecule of S03, which in turn sulfonates a new molecule of the fatty acid ester. The real sulfonation agent of the acid ester is not the sulfur trioxide but the initially formed sulfonated anhydride. In their detailed analysis of the different steps and intermediates of the sulfonation reaction, Schmid et al. showed that the mechanism presented by Smith and Stirton [31] is the correct one. 

Neutralization leads to the salt of the a-sulfo fatty acid ester, but only if the neutralization step is delayed. If the neutralization is immediate the a-sulfonated anhydride forms a disalt of the a-sulfo fatty acid as a byproduct [38]. The production of the disalt is also effected by the ratio between S03 and the ester. A high surplus of S03 would shorten the reaction time, but the amount of disalt in the end product would increase. For 90°C and 30 min an optimal S03/es-ter ratio is 1.2 1 [37]. 

Insufficient aging. Sulfonic anhydride is reacting with H2S04 and LAB, forming LAS (see before). Insufficient aging will leave this reaction incomplete. 

The imidazolides required for these reactions can be prepared from sulfonyl chlor-ides[1] or sulfonic anhydrides[2] and imidazole, or by treatment of the corresponding sulfonic acid with CDI,[1] ImSOIm,[3] or ImS02Im[3] (see Section 10.1.1). However, for the synthesis of sulfonamides it is more convenient to employ a one-pot reaction starting from the free sulfonic acid, CDI or ImSOIm, and the appropriate amine [1]... 

The condensation reactions are preferentially carried out in pyridine. As reactive species for phosphorylation of the nucleoside R OH (synthesis of a phosphortriester), the phosphoric acid azolide has been assumed. The mixed phosphoric sulfonic anhydride and a pyrophosphate tetraester have been suggested as intermediates leading to the phosphoric acid azolide. 

Method A permitted the synthesis of an optically active phosphinic-sulfonic anhydride via the optically active imidazolide 2051... 

Phosphoric-sulfonic anhydrides are of special interest because they are presumed to be intermediates in oligonucleotide coupling reactions involving phosphordiester activation by arenesulfonyl derivatives (see Section 12.7). 

However, this method is not suitable for the preparation of phosphonic- or phosphoric-sulfonic anhydrides. 1505... 

Sulfinyl sulfone (anhydride of a sulfinic acid) PhS(0)S02Ph + HjO - 2PhS02H 0 O II II -1.5... 

Christensen (1966, 1967) found that aromatic sulfonic anhydrides undergo rapid, uncatalyzed hydrolysis in either acetone or aqueous dioxan (t1/2= 17 s at 25°C for Ar =p-tolyl in 65% dioxan). Added strong acids (or added salts like NaCl or LiCl) have no effect on the rate at concentrations up to 0.01 M. The solvent isotope effect associated with this spontaneous hydro-... 

H NMR spectrum indicates that the crude product is comprised of a mixture of the sulfonyl chloride 2 and the sulfonic anhydride in an 11 1 ratio. Pure sulfonyl chloride 2 is obtained by distillation. Alternatively, the crude sulfonyl chloride can be chromatographed (60 g of silica gel per 1 g of sulfonyl chloride) eluting with hexane to provide pure 2 in equivalent yields. 

A reaction which is related to hydroxy-de-diazoniations is the formation of aryl trifluoromethylsulfonic esters (aryl triflates, ArOSC CFs) which became widely used reagents because of their leaving-group properties. The classical method of synthesis by esterification of phenols with trifluoromethane-sulfonic anhydride or -sulfonyl halide is, however, not applicable for the preparation of aryl triflates bearing a (free)... 

A number of aminobenzophenone derivatives possess nonsteroidal antiinflammatory activity. Illustrative is diflumidone (63). Its synthesis involves treatment of 3-aminobenzophenone (62) with difluoromethane-sulfonic anhydride in the presence of triethylamine. 

In the case of sulfonylation (Scheme 10) [56] and sulfinylation reactions [34], Bi salts proved again to be efficient catalysts. In contrast to the arylsulfonylation, which is under partial control of triflic acid, depending on the substrates, a complete synergistic effect between triflic acid and Bi chloride has been found in the alkanesulfonylation of arenes. In this case, the formation of mixed triflic/alkane-sulfonic anhydrides leads to the active electrophilic species. The formation of the latter exclusively requires the transient formation of a Bi chlorobistriflate species that acts as an intermediate shuttle for triflic acid, leading to the formation of the mixed anhydride precited (Scheme 11). Our experiments have shown that triflic... 

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