Thiophene S-oxides: convenient preparation, first complete structural characterization and unexpected dimerization of one of them, 2,5-diphenylthiophene-1-oxide

Abstract

Oxidation of 2,5-disubstituted thiophenes and benzothiophenes by H₂O₂ in CF₃CO₂H–CH₂Cl₂ appears a convenient method to access the corresponding reactive sulfoxides; it is used to prepare 2,5-diphenylthiophene-1-oxide, which is the first thiophene oxide to be fully structurally characterised crystallographically and the nonplanar structure of the thiophene ring is established; formation of an unexpected dehydrogenated dimer of this sulfoxide is also observed.