Thiophene sulfone

Oxidation of thiophene with peracid under carefully controlled conditions gives a mixture of thiophene sulfoxide and 2-hydroxythiophene sulfoxide. These compounds are trapped by addition to benzoquinone to give ultimately naphthoquinone (225) and its 5-hydroxy derivative (226) (76ACS(B)353). The further oxidation of the sulfoxide yields the sulfone, which may function as a diene or dienophile in the Diels-Alder reaction (Scheme 88). An azulene synthesis involves the addition of 6-(A,A-dimethylamino)fulvene (227) to a thiophene sulfone (77TL639, 77JA4199). 

Benzo[h]thiophene sulfone (229) reacts as a vinyl sulfone and forms adducts (228) and (230) when treated with mercury(II) acetate in methanol and with cyclopentadiene, respectively. 

Melles and Backer " found, from a study of the oxidation of substituted thiophenes with perbenzoic or peracetic acid, that sulfones could be obtained from polysubstituted methyl- and phenyl-thiophenes and that the presence of electron-attracting groups, such as nitro, hindered the oxidation. Oxidation of thiophene - led to a product which was formed through a Diels-Alder reaction between the intermediate thiophene sulfoxide (211) and thiophene sulfone (212) and for which two alternative structures, (213) or (214), were suggested. Similar sesquioxides were also obtained from 2- and 3-methylthiophene and 3-phenylthiophene. The structures were not proved. Bailey and Cummins synthesized thiophene-1,1-dioxide... 

PMR spectroscopy has found wide application in studies of unsubstituted tWenothiophenes, " enophenothiophenes (Table I), > 9 carboxy-, formyl-, bromo-, and adkyl- thienothiophenes, and carboxy- selenopheno-thiophenes. The PMR meAod has also been used to study alkylthieno-[3,2-h]thiophene sulfones and 4,6-dihydrothieno[3,4-h]tMophene (131)9 analyze the mixture of products of the thio-Claisen ... 

Before turning to the dihydro and tetrahydro derivatives of the fundamental ring systems, we deal with two special classes. The pyrrolenines and the thiophene sulfones both contain two double bonds in the heterocyclic ring, but in each case the conjugation does not include all the ring atoms. Finally we consider hydroxy derivatives, most of which exist predominantly as the non-aromatic carbonyl tautomers. 

Thiophene sulfones show no aromatic character, they behave as dienes and also show reactions of compounds containing a C = C bond conjugated with an electron-withdrawing group. Thiophene sulfone itself is highly unstable, but alkyl and aryl groups and fused benzene rings increase the stability. 

Thiophene sulfones undergo Diels-Alder reactions which are followed by spontaneous loss of sulfur dioxide from the products, e.g. Scheme 49. 

An azulene synthesis involves the addition of 6-(iV,iV-dimethylamino)fulvene (208) to a thiophene sulfone (77TL639, 77JA4199). 

Thiophene sulfoxides and thiophene sulfones can be prepared by direct oxidation of the corresponding sulfides (Section 3.15.9.5.1) with hydrogen peroxide. 2-Thiophene sulfones are also prepared by reaction of arylsulfonyl chlorides with thiophene under mild Friedel-Crafts conditions, or by condensation of 2-thiophenesulfonyl chlorides with aromatic compounds (Section 3.14.2.4). 

THTOPHENE. [CAS 110-02-1]. (CH C.H)2)S, formula weight 84.H, colorless liquid resembling benzene in odor, mp —30°C, bp 84°C. sp gr 1,070. Thiophene and its derivatives closely resemble benzene and its derivatives in physical ancl chemical properties. Thiophene is present in coal tar and is recovered in the benzene distillation fraction (up to about 0.5% of the benzene present). Its removal from benzene is accomplished by mixing with concentrated sulfuric acid, soluble thiophene sulfonic acid being formed. Thiophene gives a characteristic blue coloration with isatin in concentrated sulfuric add. 

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... 

Another limitation of the method is that the reduction of the sulfones with UAIH4 occasionally does not regenerate the starting thiophene, as mentioned above. For example, benzo[b]thiophene sulfone is reduced with LiAlIfy in ether to the corresponding 2,3-dihydro compound (38.39). However, when 2-n-butyl benzo[b] thiophene sulfone was reduced with UAIH4 in ether, the starting thiophene was regenerated. Dibenzothiophene sulfone was also reduced to dibenzothiophene under these conditions. 

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