The photochemistry of thiophene S-oxides

Abstract

Thiophene S-oxides have been prepared and their photoreactivity has been studied. In many cases, the sulfur moiety of the thiophene S-oxides is deoxygenated. Here, the corresponding thiophenes or hydroxylated thiophenes are isolated. In the case of the photoirradiation of tert-butyl substituted thiophene S-oxides, the oxygen of the sulfoxy unit is incorporated into the heterocyclic ring system and the corresponding furans have been isolated. Also, structures with two thiophene cores have been oxidized to the respective thiophene S-oxides. These molecules undergo photodeoxygenation, a reaction, which is catalysed by (non-oxidized) thiophenes.

Photochemistry of thiophene‐S‐oxide derivatives

“…However, Thiemann has proposed a mechanism passing through the cyclic oxathiin isomer (Scheme 1, illustrated for 2,5-di-t-butylthiophene-Soxide). [20] The first step, a-cleavage, is a mechanism that is well established in sulfoxide photochemistry. [3,4] There is ample precedent for analogous dithiins photochemically desulfurizing to produce thiophene.…”

“…Thiemann has recently reviewed his group's work in this area, [20] but a short synopsis is useful here.…”

The sonoelectrooxidation of thiophene S-oxides

“…Added structural information on thiophene S-oxides has come from X-ray crystal structural analyses [22,23], which clearly show that in the crystal the S@O bond is out of the plane defined by the four carbons that make up the heterocyclic unit. While it is known that the sulphur can invert, an intermediate state with planar geometry at the thienyl S-oxide does not possess great energetic stability [24,25].…”

Photochemical and Electrochemical Oxygenation of Thiophenes, Benzo[b]Thiophenes and Dibenzothiophenes; Photochemical and Electrochemical Behaviour of Their Oxygenated Intermediates and Products

“…64 Upon photoirradiation, 2,5-di-tert-butylthiophene S-oxide 65b leads mainly to 2,5-di-tert-butylfuran 66b with bis(2,5-di-tert-butyl-3-furyl) disulfide (68, R 1 = R 4 = Bu t , R 2 = H) as a side product (Scheme 20). 2,3,4,5-Tetraphenylthiophene S-oxide 65a is transformed into 2,3,4,5tetraphenylfuran 66a with 2,3,4,5-tetraphenylthiophene 67a as a by product.…”

“…Thus, photoirradiation of thiophene S-oxides in the presence of amines yields thiophenes directly, 64 where the fate of the amines could not be determined. Thus, photoirradiation of thiophene S-oxides in the presence of amines yields thiophenes directly, 64 where the fate of the amines could not be determined.…”