Derivatives of Sulfonic Acids

Sulfonic acids, R(Ar)S03H, form derivatives similar to those of carboxylic acids (see Table 16-3). These are sulfonyl chlorides, sulfonates (esters), and sulfonamides. The transsulfonylation reactions are similar to the transacylation reactions, except that the ester and amide cannot be made directly from the acid. See Problem 13.17 for preparation of sulfonyl chlorides and esters and Problem 13.18 for use of sulfonate esters as substrates in S l and S,42 reactions. 

Sulfonate esters can be prepared from optically active alcohols without inversion of configuration of the chiral carbinol C. The reason is that reaction involves cleavage of the H—O bond of the alcohol. 

Reduction of sulfonyl chlorides with Zn and acid yields first sulfinic acids and then thiophenols. C,H,SOXl C H,SO H C,H,SH 

CARBOXYLIC ACIDS AND THEIR DERIVATIVES Table 16-3. Comparison of Sulfonic and Carboxylic Acid Chemistry 

Preparation From ArSO,Cl From R COOH, R COCl or R —COC—R  

Hydrolysis with H2I80 ArS03H + Ri8OH R COl8OH + ROH  

Reaction with nucleophiles At alkyl C with inversion (like RX) At acyl C with retention or occasionally racemization of R. Intermediate is sp3 and has an octet 

Hydrolysis with H2 0 ArSOjH + R OH Cleavage of alkyl—oxygen bond R CO OH + ROH Cleavage of acyl—oxygen bond 

---

Alkyl sulfonates are derivatives of sulfonic acids m which the proton of the hydroxyl group is replaced by an alkyl group They are prepared by treating an alcohol with the appropriate sulfonyl chloride usually m the presence of pyridine... 

Normally, reactive derivatives of sulfonic acids serve to transfer electrophilic sulfonyl groups259. The most frequently applied compounds of this type are sulfonyl halides, though they show an ambiguous reaction behavior (cf. Section III.B). This ambiguity is additionally enhanced by the structure of sulfonyl halides and by the reaction conditions in the course of electrophilic sulfonyl transfers. On the one hand, sulfonyl halides can displace halides by an addition-elimination mechanism on the other hand, as a consequence of the possibility of the formation of a carbanion a to the sulfonyl halide function, sulfenes can arise after halide elimination and show electrophilic as well as dipolarophilic properties. 

Derivatives of sulfonic acids such as the IV-phenylbisimide of trifluoromethane-sulfonic acid (examples Figure 13.23, Side Note 13.3 and Figure 16.2). Note that alkenyl tri-flates are obtained in this way and these are the substrates of a variety of Pd-mediated C,C-coupling reactions (Chapter 16). 

DERIVATIVES OF SULFONIC ACIDS TABLE 116. DERIVATIVES OF SULFONIC AODS... 

The Bechamp method can also be used in reducing the nitro derivatives of sulfonic acids. A typical example being the manufacture of metanilic acid and related substances [11]. 

Sulfate esters are not, strictly speaking, derivatives of sulfonic acids but of sulfuric acid and so are not properly under the purview of this chapter. However, it should be possible to extend to sulfonates the recent achievements of Lowe and coworkers on the stereochemistry of sulfates, based on the use of oxygen isotopes16-22. 

TABLE XXII. ORGANIC DERIVATIVES OF SULFONIC ACIDS a) Listed in order of increasing m.p. of the corresponding sulfonamide ... 

Sulfonyl chlorides are highly reactive derivatives of sulfonic acid and possess similar properties and reactivity to acid chlorides of carbo Q lates. The reaction with nucleophiles such as amines requires alkaline conditions (pH 9-10) and proceeds through the formation of an unstable pentavalent transition state (Scheme 1.10). Hydrolysis is a major competing reaction in water therefore the reaction with amines proceeds with better yield when done in organic solvents. Sulfonyl chlorides have played an important role in bioconjugation chemistry, since sulfonic acids can be easily converted into sulfonyl chlorides using thionyl chloride or phosphorus pentachloride in non-aqueous conditions. ... 

The invention of Heath et al. relates to novel phosphonate allyl monomers, made from reaction of an unsaturated oxirane with amine- or hy-drojyl-functionalized phosphonic acids (Scheme 3.21). These monomers were copolymerized with other unsaturated species (acrylic acid, maleic acid, acrylamide, or monomer derivatives of sulfonic acid, etc), yielding phosphonate polymers or oligomers. Phosphorus-containing monomers were incorporated at a ratio of 0.1-30% and polymerized in aqueous media. The final polymers had a molecular weight of 800-30 000 g mol . With their phosphonic acids groups (free acid or salts forms), they are of particular use as oilfield scale inhibitors. 

Sulfonate ester (Section 11.10) A compound with the formula ROSO2R and considered to be derivatives of sulfonic acids, HOSO2R. Sulfonate esters are used in organic synthesis because of the excellent leaving group ability of the fragment OSO2R. ... 

---