Tetrafluorothiophene S,S-dioxide: a perfluorinated building block.

Tetrafluorothiophene S,S-dioxide, a highly reactive diene and dienophile, has been synthesized. A new route to 3,4-difluoro- and tetrafluorothiophene has been realized, and the previously unknown 2,3,4-trifluorothiophene has been obtained. The reactivity of tetrafluorothiophene S-oxide has been compared with that of the S,S-dioxide.