Benzo thiophene sulfonic acids

Benzo[6]thiophene sulfonic acids (isolated as the potassium salts) may be converted into the sulfonyl chloride, and then into the corresponding sulfonamide,660 sulfanilide,660 sulfonate ester,86 or thiol.84 Sulfonyl chlorides are hydrolyzed by boiling water to the corresponding sulfonic acid.660... 

Indole is sulfonated under similar conditions to pyrrole though in this case the 3-sulfonic acid is formed. Benzo[Z>]thiophene is also sulfonated in the 3-position (71AHC(13)235). 

The reaction of butadiene with the sulfone of 3-benzo[6]thiophene-carboxylic acid under Diels-Alder conditions gives the adduct (32). Catalytic reduction over platinum oxide removes the 2,3-double bond. 

Sulfonation of benzo[6]thiophene seems to give the 3-sulfonic acid as the major monosulfonated product, with minor amounts of the 2-isomer (70AHQ11)177). Sulfonation or chlorosulfonation of 2- or 3-methylbenzo[6]thiophene takes place in the free thiophene position. 

Sulfonic acid and sulfone derivatives of thiophenes and benzo[b]thiophenes 932... 

Sulfonation of benzo[6 ]thiophene with concentrated sulfuric acid in acetic anhydride at 20 °C gives a mixture which is chiefly the 3-sulfonic acid, with some 2-isomer and 3-acetylbenzo[6 Jthiophene (70AHC(i)l77). Chlorosulfonation of 2- or 3-methyl-benzo[6 Jthiophene gives the corresponding 3- or 2-sulfonyl chloride in satisfactory yield. The various available 4-, 5-, 6- and 7-mercaptobenzothiophenes or sulfides (Section 3.15.9.5.2) can be oxidized to sulfonic acids or sulfones by conventional means. 

The 4H NMR spectra of some methyl-,79-83 halo-,81 mercapto-,84 nitro-,84 and methoxybenzo[6]thiophenes,85 and of some sulfonic acids, sulfonyl chlorides, and sulfonate esters86 have been recorded. Two groups of workers87,88 have independently studied the 4H NMR spectra of a range of benzo[6]thiophene derivatives in an attempt to correlate the chemical shifts of the protons with the substituents. Such a correlation helps to assign structures to new benzo[6]thiophene derivatives, and it also throws light on the influence of substituents on the NMR parameters of heteroaromatic systems in general. 

The IR spectra of cis- and nms-octahydrobenzo[6]thiophene have been recorded.27 IR data have been given for several benzo[6]thio-phene sulfonic acids and their derivatives.86... 

Dihydrobenzo[6]thiophene 426 and its 2-methyl derivative182 are readily dehydrogenated with sulfur to the corresponding benzo[ ]-thiophene. 2,3-Dihydrobenzo[6]thiophenes are oxidized by peracetic acid to the corresponding sulfones (Section VI, P, 2), and give crystalline complexes with mercuric chloride. 

There is surprisingly little reliable information on the sulfonation of benzo[6]thiophene or its derivatives. Benzo[6]thiophene is more readily sulfonated than naphthalene.699 Reaction with concentrated sulfuric acid at 80° gives a mixture of mono-, di-, and trisulfonic acids, reaction with 70% sulfuric acid at 80° gives a monosulfonic acid,699 and reaction with 18% oleum gives a disulfonic acid 86 in each case the orientation of the products is unknown. Treatment of benzo[6]thiophene with concentrated sulfuric acid in acetic anhydride at 20° gives 3-acetylbenzo[6]thiophene (ca. 10%) and a sulfonation product (isolated as the potassium salt), which was believed to be the 3-sulfonic acid.660 Recently, the sulfonation product has been shown to contain the 2- (8%) and 3-isomer (92%), by conversion into the sulfonyl chlorides and reduction to a separable mixture of 2- and 3-mercaptobenzo[6]thiophene.84... 

Oxidation of benzo[b] thiophene 1,1-dioxide with KMn04 affords the sulfonic acid 172 [189], while oxidation with alkaline H202 yields the ketone 173 (Scheme 97) [244]. Oxidation of 3-substituted benzo[ ]thiophene 1,1-dioxides 174 with alkaline H202 affords the alcohols 175 as the principal product (Scheme 98) [244]. Compounds 173 and 175 are presumably formed through Michael addition of HOO to the 3-position of the substrates. Indeed, the reaction of 3,4-di-ferf-butylthiophene 1,1-dioxide 83 with H202 under alkaline conditions at room temperature afforded the Michael adduct 177 in 91 % yield, while the reaction carried out at 50-60 °C gave the ring-opened product 178 in 15% yield in addi-... 

Benzo[Z ]thiophene (thionaphthene) reacts with concentrated sulfuric acid in acetic anhydride at 10 °C to give an excellent yield of the monosulfonic acid, probably mainly the 3-sulfonic acid with a little of the 2-isomer. In benzo[Z>]thiophene, the calculated /r-electron density pattern would predict the relative order of reactivity for electrophilic substitution to be 3 > 2 > 6 5." In agreement, 2-and 3-methylbenzothiophene (139, 141) react with excess chlorosulfonic acid to give the 3- and 2- sulfonyl chlorides (140, 142) respectively (Equations 36 and 37) 2,110 However, more recent attempts to chlorosulfonate benzo[6]thiophene by treatment with chlorosulfonic acid (one equivalent) in excess thionyl chloride at RT failed to give a pure product. ... 

D. ci - -Thiabicyclo[4 .. Q]nonan S,S-Dioxide [Benzo[c]thiophene 2,2-dioxide, cis-octahydro-]. A solution of the sulfide (43.0 g., 0.303 mole) in 11. of ether is cooled to 0° and treated dropwise while magnetically stirred with 1.01. of 0.65iV ethereal monoperphthalic acid (0.65 mole). The mixture is kept overnight at 0°, after which time the precipitated phthalic acid is separated by filtration and the filtrate concentrated with a rotary evaporator. Bulb-to-bulb distillation of the residual oil at 0.05-0.1 mm. affords the sulfone as a eolorless liquid (48.5-50 g., 92-95%) (Note 11). This product is crystallized from ether-hexane to give a colorless solid, m.p. 39-41° (Note 12). 

The 4a,9b double bond in 1,2,3,4-tetrahydrodibenzothiophene 5,5-dioxide (68) and similar compounds, is essentially nonaromatic and in this respect resembles the 2,3 bond in benzo[6]thiophene 1,1-dioxide. Catalytic reduction of 68 results in the formation of l,2,3,4,4a,9b-hexahydrodibenzothiophene 5,5-dioxide (92 /o). Subsequent reduction of the sulfone with LAH yields 1,2,3,4,4a,9b-hexahydrodibenzothiophene (69) as an oil (78 /o). Oxidation of 4-keto-l,2,3,4-tetrahydrodi-benzothiophene (44a) to its sulfone with peracetic acid (63 /o) followed by... 

The presence of benzo[6]thiophene in commercial naphthalene, its possible contamination with isomeric thienothiophenes 1 and 2, and their ability to poison aromatic hydrogenation catalysts led Maxted and Walker to develop detoxification by a preliminary short hydrogenation, in which thienothiophenes 1 and 2, and benzo[6]-thiophene are adsorbed on the catalyst. This is followed by their hydrogenation products that can easUy be oxidized with hydrogen peroxide or permolybdic acid to nontoxic sulfones subsequent hydrogenation of the aromatic hydrocarbons is then performed as usual. 

Crude naphthalene obtained from coal tar may contain up to 5% benzo[6]thiophene which is only partially removed by selective sulfonation.43-45 Several improvements45-51 make this process more efficient. Other chemical methods of separation include oxidation with peracetic acid, which converts benzo[6]thiophene into its readily separated 1,1-dioxide,52 and treatment with ozone, which selectively... 

Potassium benzo[6]thiophene-4-sulfonate may be prepared by treating 4-mercaptobenzo[6]thiophene in dimethylformamide with oxygen in the presence of potassium hydroxide. It gives a disulfonic acid of undetermined structure on further sulfonation.86... 

Dihydrobenzo[c]thiophene may be oxidized to its sulfone (Table VII) with peracetic acid,28,69,87,88 aqueous hydrogen peroxide,9 or potassium permanganate,21 and when benzocyclobutene and 1,2-diphenylbenzocyclobutene are heated with sulfur dioxide, they give l,3-dihydrobenzo[c]thiophene 2,2-dioxide89 and its cis-1,3-diphenyl derivative (83),69,90 respectively [Eq. (5)]. 1,3-Dihydro-benzo[c]thiophene 2,2-dioxide also arises when the thiadiazepine (17b) is heated just above its melting point (175°-180°).34a When sulfur dioxide is passed into a solution of diphenyldiazo-... 

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