Reactions desulfonation

As in the nitration of naphthalene, sulfonation gives the 1-substituted naphthalene. However, because the reverse reaction (desulfonation) is appreciably fast at higher temperatures, the thermodynamically controlled product, naphthalene-2-sulfonic acid, can also be obtained. Thus it is possible to obtain either of the two possible isomers of naphthalene sulfonic acid. Under kineticaHy controlled conditions naphthalene-l-sulfonic acid [85-47-2] (82) is obtained thermodynamic control gives naphthalene-2-sulfonic acid [120-18-3] (83). 

The synthesis of 2,4-dihydroxyacetophenone [89-84-9] (21) by acylation reactions of resorcinol has been extensively studied. The reaction is performed using acetic anhydride (104), acetyl chloride (105), or acetic acid (106). The esterification of resorcinol by acetic anhydride followed by the isomerization of the diacetate intermediate has also been described in the presence of zinc chloride (107). Alkylation of resorcinol can be carried out using ethers (108), olefins (109), or alcohols (110). The catalysts which are generally used include sulfuric acid, phosphoric and polyphosphoric acids, acidic resins, or aluminum and iron derivatives. 2-Chlororesorcinol [6201-65-1] (22) is obtained by a sulfonation—chloration—desulfonation technique (111). 1,2,4-Trihydroxybenzene [533-73-3] (23) is obtained by hydroxylation of resorcinol using hydrogen peroxide (112) or peracids (113). 

Naphthalenesulfonic Acid. The standard manufacture of 2-naphthalenesulfonic acid involves the batch reaction of naphthalene with 96 wt % sulfuric acid at ca 160°C for ca 2 h (13). The product contains the 1- and 2-isomers in a ratio of ca 15 85. Because of its faster rate of desulfonation,... 

Naphthalenedisulfonic acid (Ebert-Merz a-acid) is partially isomerized in sulfuric acid at 160°C to 2,6-naphthalenedisulfonic acid. The reaction takes place by a desulfonation—resulfonation mechanism. 

Sulfonic acids may be hydrolytically cleaved, using high temperatures and pressures, to drive the reaction to completion. As would be expected, each sulfonic acid has its own unique hydrolytic desulfonation temperature. Lower alkane sulfonic acids possess excellent hydrolytic stability, as compared to aromatic sulfonic acids which ate readily hydrolyzed. Flydrolytic desulfonation finds use in the separation of isomers of xylene sulfonic acids and other substituted mono-, di-, and polysulfonic acids. 

Desulfonation reaction (reductive and oxidative desulfonation, nucleophilic substitution, elimination, and SO2 extrusion) in synthesis and transformations of heterocycles 99T10547. 

A review article is an intensive survey of a rather narrow field for example, the titles of some recent reviews are Desulfonation Reactions Recent Developments , Pyrrolizidine and Indolizidine Syntheses Involving 1,3-Dipolar Cycloaddtion , and From Corrin Chemistry to Asymmetry Catalysis—A Personal Account. A good review article is of enormous value, because it is a thorough survey of all the work done in the field under discussion. Review articles are printed in review journals and in certain books. The most important review journals in organic chemistry (though most are not exclusively devoted to organic chemistry) are shown in Table A.3. Some of the journals listed in Table A.l, for example, the Bull Soc. Chim. Fr. and J. Organomet. Chem. also publish occasional review articles. 

The nitro groups in Eqs. 7.88-7.90 are readily replaced by hydrogen with tin hydride under radical conditions as discussed already. However, the nitro groups in the a-nitrosulfides or (3-nitrosulfides are not replaced by hydrogen on treatment with tin hydride but the reaction affords desulfonated products (Eq. 7.51) and alkenes (Eq. 7.97) such radical elimination reactions are discussed in Section 7.3.1. (see Eqs. 7.91 and 7.92).138... 

Azacanthines, 374, like their deaza analogues (cf. Equation 128), can be prepared by inverse electron demand aza-Diels-Alder reactions of the appropriately tethered amidoalkyl-l,2,4-triazinylindoles 373 (Equation 135) <1995TL6591>. The sulfonyl-substituted derivatives 375 can be prepared similarly in high yield, although the conditions for each individual reaction are important, since an appreciable amount of the desulfonated product 376 may also be formed (Equation 136) <1998TL2487>. 

Both enzymatic and whole cell-mediated transformation of sulfonamides has been described, usually with high removal efficiencies and relatively short treatments. Although different metabolites have been elucidated, no clear pathways have been defined however, the desulfonated metabolites have been widely identified (with LAC and fungal cells) along with the products of hydroxylation, formylation, and deamination reactions, and combinations of them. 

Except for these studies of their protonation behavior, almost the only other aspect of the chemistry of sulfonic acids that has been investigated to any extent from a mechanistic point of view is the desulfonation of aromatic sulfonic acids or sulfonates. Since this subject has been well reviewed by Cerfontain (1968), and since the reaction is really more of interest as a type of electrophilic aromatic substitution than as sulfur chemistry, we shall not deal with it here. One should note that the mechanism of formation of aromatic sulfonic acids by sulfonation of aromatic hydrocarbons has also been intensively investigated, particularly by Cerfontain and his associates, and several... 

Kurz and Frieden in 1977 and 1980 determined -secondary kinetic isotope effects for the unusual desulfonation reaction shown in Table 1, both in free solution and with enzyme catalysis by glutamate dehydrogenase. The isotope effects (H/D) were in the range of 1.14-1.20. At the time, the correct equilibrium isotope effect had not been reported and their measurements yielded an erroneous value... 

A historically important method, first used about 1900, is sulfonation of benzene followed by desulfonation with caustic. This is classic aromatic chemistry. In 1924 a chlorination route was discovered. Both the sulfonation and chlorination reactions are good examples of electrophilic aromatic substitution on an aromatic ring. Know the mechanism of these reactions. These routes are no longer used commercially. 

Groups other than H can be displaced during electrophilic aromatic attack. The acid-catalyzed reversal of sulfonation (desulfonation) exemplifies such a reaction here, displaces SOjH as SOj and H". 

Phenol was prepared before World War I through the distillation of coal tar. The first synthetic process involved the sulfonation of benzene followed by desulfonation with a base. In this process, benzene sulfonic acid is prepared from the reaction of benzene and sulfuric acid ... 

A new preparation of the C g ketone, an important synthon for the synthesis of vitamin A had also been published by Valla et al. [71]. Hence p-ionone and acetonitrile were condensed in the presence of KOH, to afford the nitrile (80%, E/Z isomers 80/20). A Reformatsky reaction of ethyl bromoacetate with the nitrile provided the ethyl P-ionylideneacetoacetate in 70% yield. Subsequent reduction with NaBH4, followed by esterification (MeSC Cl) and desulfonation of the unstable... 

Direct conversions of sulfones to carbonyl compounds have been realized by oxidative desulfonation of the a-carbanions. Molybdenum peroxide (Mo05-Py-HMPA) [266], or bis(trimethylsilyl)peroxide (Mc3SiOOSiMej, BTSP, Table 3.3) [267] were used as oxidants. Hwu s method with BTSP is attractive and was found useful for the preparation of 180-Iahelled compounds [267] in this one-pot reaction Me3SiO behaves as a leaving group and a back-attacking species. 

Readily available allylic and benzylic hichloromethyl sulfoxides undergo an unusual base-induced /(-elimination of chloroform, with formation of the corresponding a,/ -unsaturated sulfine, under mild conditions at room temperature die procedure has been applied to form vinylthioaldehyde 5-oxides and vinylthioketone 5-oxides. 89 N-Sulfinylamines (115) have likewise been prepared by /(-elimination of chloroform from trich Ioromcthanesulfinamidcs (114).90 The reaction is promoted rapidly at room temperature by pyrrolidine and Ht N and the sulfinylamines (115) can be trapped by o-phenylenediamme (116), to give benzothiadiazole, before desulfonative hydrolysis occurs. 

By analogy with the above reactions that use 0- and IV-nucleophiles, it has been shown that ring opening of Af-Boc p-lactams can be achieved by reaction with metallated carbon nucleophiles. For instance, Baldwin developed the reaction of a-lithiated sulfones, Scheme 30, with p-lactams, such as 89, to provide access to y-keto a-amino esters 90, after desulfonation of the resulting intermediates. In particular, the angiotensin converting enzyme inhibitor WF-10129 91 has been synthesized by this route [97]. 

Desulfonation of LAS under sulfate limiting conditions appears to proceed fastest for shorter alkyl chain lengths and faster for isomers in which the benzenesulfonate moiety is attached to a central position on the alkyl chain (Kertesz et al., 1994). Since in wastewater treatment sulfate is not limiting, this reaction is not relevant in the perspective of the fate of the bulk of LAS. However, the reaction shows that the trend of increasing rate of G)-p-oxidation with increasing alkyl chain length is an exception, not the rule. 

---