Aromatic compounds sulfonated

Similarity searches, 6 7-8 Simple aromatic compounds, sulfonation of, 23 524-525... 

Sulfonation (Section 12 4) Sulfonic acids are formed when aromatic compounds are treated with sources of sulfur trioxide These sources can be concentrated sulfuric acid (for very reactive arenes) or solutions of sulfur trioxide in sulfuric acid (for ben zene and arenes less reactive than ben zene)... 

Nitrations can be performed in homogeneous media, using tetramethylene sulfone or nitromethane (nitroethane) as solvent. A large variety of aromatic compounds have been nitrated with nitronium salts in excellent yields in nonaqueous media. Sensitive compounds, otherwise easily hydroly2ed or oxidized by nitric acid, can be nitrated without secondary effects. Nitration of aromatic compounds is considered an irreversible reaction. However, the reversibihty of the reaction has been demonstrated in some cases, eg, 9-nitroanthracene, as well as pentamethylnitrobenzene transnitrate benzene, toluene, and mesitylene in the presence of superacids (158) (see Nitration). 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaHy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphoms [7723-14-0] produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-Hthiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has Httie commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

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. 

Other Applications. Hydroxylamine-O-sulfonic acid [2950-43-8] h.2is many applications in the area of organic synthesis. The use of this material for organic transformations has been thoroughly reviewed (125,126). The preparation of the acid involves the reaction of hydroxjlamine [5470-11-1] with oleum in the presence of ammonium sulfate [7783-20-2] (127). The acid has found appHcation in the preparation of hydra2ines from amines, aUphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. It is also an important reagent in reductive deamination and specialty nitrile production. 

Miscellaneous Dyes. Other classes of dyes that stiU have some importance are the stilbene dyes and the forma2an dyes. Stilbene ( es are in most cases mixtures of dyes of indeterminate constitution that are formed from the condensation of sulfonated nitroaromatic compounds ia aqueous caustic alkah either alone or with other aromatic compounds, typically arylarnines (5). The sulfonated nitrostilbene [128-42-7] (79) is the most important nitroaromatic, and the aminoa2oben2enes are the most important arylarnines. Cl Direct Orange 34 [2222-37-6] (Cl 40215-40220), the condensation product(s) of (79) and the aminoa2oben2ene [104-23-4] (80), is a typical stilbene dye. 

Acidic Hydrolysis. Hydrolysis of esters by use of water and a mineral acid leads to an equiUbrium mixture of ester, alcohol, and free carboxyHc acid. Complete reaction can only be achieved by removal of alcohol or acid from the equiUbrium. Because esters have poor solubiUty in water, the reaction rate in dilute acids is fairly low. Therefore, emulsifiers such as sulfonated oleic acid or sulfonated aromatic compounds (TwitcheU reagent) are added to facihtate the reaction. 

Like other aromatic compounds, aromatic ethers can undergo substitution in the aromatic ring with electrophilic reagents, eg, nitration, halogenation, and sulfonation. They also undergo Eriedel-Crafts (qv) alkylation and acylation. 

Tnfluoroacetic anhydnde in a mixture with sulfuric acid is an efficient reagent for the sulfonylation of aromatic compounds [44] The reaction of benzene with this system in nitromethane at room temperature gives diphenyl sulfone in 61% yield Alkyl and alkoxy benzenes under similar conditions form the corresponding diaryl sulfones in almost quantitative yield, whereas yields of sulfones from deactivated arenes such as chlorobenzene are substantially lower [44] The same reagent (tnfluoroacetic anhydride-sulfunc acid) reacts with adamantane and its derivatives with formation of isomeric adamantanols, adamantanones, and cyclic sultones [45]... 

Pyridine lies near one extreme in being far less reactive than benzene toward substitution by electrophilic reagents. In this respect it resembles strongly deactivated aromatic compounds such as nitrobenzene. It is incapable of being acylated or alkylated under Friedel-Crafts conditions, but can be sulfonated at high temperature. Electrophilic substitution in pyridine, when it does occur, takes place at C-3. 

Nitration and sulfonation of aromatic compounds probably occur via the formation of the nitryl and sulfonyl cations ... 

Recently, Dutta and Maiti [21] reported nitro displacement polymerization of the bisphenol dianion with the sulfone activated dinitro aromatic compounds. In addition, there have been recent reports of the development of functionalized PEEK [22] and polyether sulfone ketone (PESK) [23] that are comparable to commercially available high performance polymers. 

A. Radical Anions of Sulfoxide- and Sulfone-containing Aromatic Compounds... 

Further lowering the dielectric constants has been achieved by preparing highly fluorinated polyethers without any sulfone, ketone, or other polarizable groups.239 241 Typically, the /jara-lluorinc atoms on highly fluorinated aromatic compounds, such as hexafluorobenzene and decafluorobiphenyl, are activated and thus can go through aromatic nucleophilic substitution with HFBPA under typical reaction conditions (Scheme 6.31).217... 

Diaryl sulfones can be formed by treatment of aromatic compounds with aryl sulfonyl chlorides and a Friedel-Crafts catalyst. This reaction is analogous to Friedel-Crafts acylation with carboxylic acid halides (11-14). In a better procedure, the aromatic compound is treated with an aryl sulfonic acid and P2O5 in polypho-sphoric acid. Still another method uses an arylsulfonic trifluoromethanesulfonic anhydride (ArS020S02CF3) (generated in situ from ArS02Br and CF3S03Ag) without a catalyst. ... 

For many years phenol was made on a large industrial scale from the substitution reaction of benzene sulfonic acid with sodium hydroxide. This produced sodium sulfite as a by-product. Production and disposal of this material, contaminated with aromatic compounds, on a large scale contributed to the poor economics of the process, which has now been replaced by the much more atom economic cumene route (see Chapter 2, Schemes 2.2 and 2.3). 

Directed lithiation of aromatic compounds is a reaction of broad scope and considerable synthetic utility. The metalation of arenesulfonyl systems was first observed by Gilman and Webb and by Truce and Amos who reported that diphenyl sulfone is easily metalated at an orf/io-position by butyllithium. Subsequently, in 1958, Truce and coworkers discovered that metalation of mesityl phenyl sulfone (110) occurred entirely at an orf/io-methyl group and not at a ring carbon, as expected. Furthermore, refluxing an ether solution of the lithiated species resulted in a novel and unusual variation of the Smiles rearrangement and formation of 2-benzyl-4,6-dimethyl-benzenesulfinic acid (111) in almost quatitative yield (equation 78). Several other o-methyl diaryl sulfones have also been shown to rearrange to o-benzylbenzenesulfinic acids when heated in ether solution with... 

Silica sol-gel inunobihzed La(OTf)3 (Scheme 48.2B) previously used in the acylation of a series of alcohols and activated aromatic compounds using acetic anhydride as acylating agent, showed a poor activity compared with other various sihca sol-gel inunobihzed triflate derivatives (tert-butyl-dimethylsilyl-trifluoromethane-sulfonate (BDMST), or trifhc acid (HOTf)). Acylation at the aromatic ring occurred over the BDMST and HOTf catalysts, while the La(OTl)3 catalysts only led to O-acetylated products [22]. Such behavior is characteristic... 

Synthetically important substitutions of aromatic compounds can also be done by nucleophilic reagents. There are several general mechanism for substitution by nucleophiles. Unlike nucleophilic substitution at saturated carbon, aromatic nucleophilic substitution does not occur by a single-step mechanism. The broad mechanistic classes that can be recognized include addition-elimination, elimination-addition, and metal-catalyzed processes. (See Section 9.5 of Part A to review these mechanisms.) We first discuss diazonium ions, which can react by several mechanisms. Depending on the substitution pattern, aryl halides can react by either addition-elimination or elimination-addition. Aryl halides and sulfonates also react with nucleophiles by metal-catalyzed mechanisms and these are discussed in Section 11.3. 

The first step involved the reaction of PPO with chlorosulfonic acid according to a literature method (H). The sulfonated PPO was hygroscopic and unstable. We succeeded (12) in converting the sulfonate groups into stable sulfone groups by reacting them with aromatic compounds at elevated temperatures (120 0. The final dark solution was washed with dilute sodium bicarbonate, and the product precipitated in methanol, filtered and dried. 

Sulfonvlated PPO. The sulfonylation is achieved by sulfonation reaction on PPO, followed by the reaction with aromatic compounds as outlined in Scheme 1. 

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