Sulfonylation of aromatic

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]... 

Simple ways to catalyze nitrations and sulfonylations of aromatic compounds are of great interest since these reactions are carried out industrially on large scale. Clays and zeolites with defined pore structures and channels as acidic catalysts have been utilized in nitrations [109] and Friedel-Crafts sulfonylations [110]. 

Lanthanide(III) triflates catalyze the nitration of a range of simple aromatic compounds (benzene, toluene, biphenyl, m- and p-xylene, naphthalene) in good to excellent yield using stoichiometric quantities of 69% nitric acid.276 Bismuth(III) triflate was found to catalyze sulfonylation of aromatics with aromatic sulfonyl chlorides with similar high efficiency.277... 

Sulfonylation of aromatic hydrocarbons in the presence of a Lewis acid and the reaction of sodium benzenesulfinate with alkyl halides proved to be particularly easy and useful to prepare starting materials for the Julia olefination procedure (see Section 4.3.2). 

Friedel-Crafts-type intermolecular sulfonylation of aromatics can also be conveniently carried out over Nafion-H by reacting aromatics with arenesulfonic acids at reflux temperature with azeotropic water removal465 [Eq. (5.168)]. Methanesulfonic acid also reacts with para-xylene to yield 2-methanesulfonyl-1,4-dimethylbenzene in much lower yield (30%). 

Cation B is first deprotonated to give the hydroxycamphene derivative C. C reacts with an electrophile of unknown structure that is generated from sulfuric acid under these conditions. In the discussion of the sulfonylation of aromatic compounds (Figure 5.17), we mentioned protonated sulfuric acid H3S04 and its dehydrated derivative HS03 as potential electrophiles, which might assume the same role here. In any case, the reaction results in the formation of carbenium ion E. 

The Friedel-Crafts sulfonylation of aromatics with alkane- and arenesulfonyl halides and anhydrides has been studied (Eq. 9) [23]. In the reaction of pentafluorobenzenesul-fonyl fluoride with pentafluorobenzene, decafluorodiphenyl sulfone is formed with deca-fluorodiphenyl [23c]. Certain phenylacetylenes react with SO2 and benzene in the presence of SbFs to form benzothiophene 5-oxide [24]. (Eq. 10). Sulfinyl fluoride reacts similarly with arenes under SbFs catalysis to give sulfoxides (Eq. 11) [25]. 

Under these conditions, the sulfonyl chloride appears directly in the rate equations and for benzenesulfonylation in nitrobenzene solvent, the greater polarity of the solvent should enhance ionization of the sulfonyl chloride-catalyst complex (Equation 24). Studies of the sulfonylation of aromatic substrates with aluminium chloride catalyst in nitrobenzene showed that with more reactive substrates, e.g. 1,3,5-trimethylbenzene (mesitylene), the reaction exhibits overall second order kinetics rate = ki [AICI3] [PhS02Cl], the rate was independent of the concentration of the aromatic compound. 

Fig. 2. Diels-Alder-type reactions of aromatic and sulfonyl isocyanates.

The much-used sulfonylation by aromatic sulfonyl chlorides is illustrated by the conversion of quinazolin-4-amine into the sulfonamide (247) using p- nitrobenzenesulfonyl chloride at 60 °C (56JCS3509). 

Amino groups bound to sulfur can be replaced by fluorine via diazotization. In contrast to carboxylic acid amides, fluorodediazoniation of aromatic sulfonamides IS readily accomplished to give sulfonyl fluorides in high yields [52, 7S (equation 16) Tetrazotization-fluorination of sulfanilamide can also be effected to give a 38% yield of p-fluorobenzenesulfonyl fluoride [52],... 

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

Sulfonyl nitrenes react with benzene to produce appreciable yields of aromatic substitution products. The nitrene thermally generated in benzene from 229 gives a monosubstitution product. When the reaction is carried out in mesitylene as a solvent, the two sulfonylnitrenes react with mesitylene to afford 230 (equation 140)135. 

Aromatic sulfonyl chlorides can be prepared directly, by treatment of aromatic rings with chlorosulfuric acid. ° Since sulfonic acids can also be prepared by the same reagent (11-7), it is likely that they are intermediates, being converted to the halides by excess chlorosulfuric acid. The reaction has also been effected with bromo-and fluorosulfuric acids. 

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. ... 

A long series of studies of aromatic nucleophilic substitution included the kinetics of reactions of l-chloro-2,4-bis(trifluoromethylsulfonyl)benzene, 3-nitro-4-chlorophenyl trifluoromethyl sulfone and 2-chlorophenyl trifluoromethyl sulfone with sodium methox-ide or ammonia in methanol . The SO2CF3 group was found to have an enormous accelerating effect, in accord with the value of 1.65, based on the dissociation of anilinium ion. Further examples of the promotion of nucleophilic aromatic substitution by fluoro-substituted sulfonyl groups are given by Yagupol skii and coworkers . 

Photoproduct of Dl in solid state. Major photoproduct from Dl in the solid state was isolated by silica gel column chromatography and analyzed by IR and NMR spectroscopy (Figures 2 and 3). NMR spectrum shows that a photoproduct of Dl has the absorption band of the N, N-dimethylamino group (2.86 ppm) and the symmetric absorption band of aromatic protons (6.57-7. 10 ppm). The strong IR absorption of the sulfonyl group (12.10 and 1420 cm-1) can be seen in Figure 3. From NMR and TR spectra, the main photoproduct of the Dl was identified as trifluoromethanesulfonic acid 4-N, N-dimethylaminophenyl ester. 

Fig. 11.9. Mechanisms and products of hydrolysis of aromatic N-sulfonyl imidates (11.66) as potential prodrugs of drugs containing sulfonamide or ester moieties [101] [102]...

More abundant are reductions with sodium sulfite which is applied in aqueous solutions (solubility 24%). Its specialties are reduction of peroxides to alcohols [257], of sulfonyl chlorides to sulfinic acids [252], of aromatic diazonium compounds to hydrazines [253], and partial reduction of geminal polyhalides [254] Procedure 43, p. 216). 

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