Synthesis of [all]-S,S-dioxide oligothiophenes using HOF·CH ₃CN

(Chemical Equation Presented) Nonaromatic stable polyenes are obtained by dioxygenation of oligothiophenes using HOF·CH₃CN prepared in situ by passing F₂ through aqueous acetonitrile (see scheme). These fully S,S-dioxygenated derivatives have a considerably smaller HOMO-LUMO gap than the parent compounds; furthermore, in the solid state they tend to form favorable π-π stacking interactions, unlike most non-oxidized oligothiophenes which adopt the "herringbone" motif.