Thiophene-2-sulfinic acid

Thiophene-2-sulfonic acid is a strong acid, similar to benzenesulfonic acid. It forms a sulfonyl chloride with phosphoryl chloride which on reduction with zinc yields thiophene-2-sulfinic acid. 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

Benzo[h]thiophene-3-sulfonyl chloride is reduced to the sulfinic acid by Na2S03-NaHC03.101... 

Aluminum chlorideIthionyI chloride Thiophene S-oxide ring from sulfinic acids with C-de-/crf-butylation... 

Rhodococcus sp. Strain T09 A Rhodococcus strain T09 was isolated by enrichment on media-containing BT. The desulfurization mechanism of this organism was reported to be similar to Gordonia sp. 213E due to the observation of similar intermediates however, the substrate specificity was different. The strain T09 could use 2-methyl, 3-methyl and 5-methyl BT apart from BT as sole source of sulfur for growth, but not 7-methyl or ethyl derivatives. Additionally, it could also use methyl thiobenzothiazole, marcaptobenzothiazole, as well as benzene sulfide, benzene sulfonate, biphenyl sulfinate, dimethyl sulfate, dimethyl sulfone, dimethyl sulfide, methane sulfonic acid, thiophene, and taurine as sole sulfur sources. However, it could not grow on DBT or DBT sulfone. 

In the previous examples, the sulfur atom acted as a nucleophile. Electron-deficient sulfur species such as sulfenyl ion and its equivalents (e.g. disulfide/Lewis acid complexes, sulfenic acids, sulfenyl halides, sulfonium ions, sulfines, etc.), can also serve as an electrophile. Oxidative ring closure of enethiols (a-thioketocarboxylic acid) (124), which proceeds via disulfides, produces thiophenes (125) in good yields (86EUP158380, 88JHC367). 

In contrast, azuleno[l,8-fcc]thiophene 179c is generated by the acid-catalyzed cyclodehydration of sulfine 179a and demethylation of the resulting sulfenium salt 179b (71JA2196). 

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