2-Hydroxythiophene sulfoxide

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). 

Oxidation of thiophene with Fenton-like reagents produces 2-hydroxythiophene of which the 2(570 One isomer is the most stable (Eq. 1) <96JCR(S)242>. In contrast, methyltrioxorhenium (Vn) catalyzed hydrogen peroxide oxidation of thiophene and its derivatives forms first the sulfoxide and ultimately the sulfone derivatives <96107211>. Anodic oxidation of aminated dibenzothiophene produces stable radical cation salts <96BSF597>. Reduction of dihalothiophene at carbon cathodes produces the first example of an electrochemical halogen dance reaction (Eq. 2) <96JOC8074>. 

Thiophene-1-oxides Thiophene-1,1 -dioxides. 2.1 Reaction with nucleophiles. 2.2 Cycloaddition reactions. 2.3 Other reactions Thiophene S,N-ylides and S,C-ylides. 3.1 Cycloaddition reactions of S,N-ylides and S,C-ylides. 3.2 Cyclopropanation reactions of S,C-ylides. 3.3 Thermal transformations of thiophene S,N- and S,C-ylides Oxothiophenes Tautomeric with Hydroxythiophenes. 4.1 Tautomerism. 4.2 Alkylation and acylation. 4.3 Condensation reactions at the methylene group. 4.4 Halogenation. 4.5 Oxidative coupling. 4.6 Cycloaddition. 4.7 2,3-Diones 4 Sulfoxides and sulfones. 4.9 Photochemistry. 4.10 Macrocyclic polyethers... 

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