Synthetic Attempts towards Polymers with Pentafulvene Structural Units

Abstract

Pentafulvenes with weakly electron-donating substituents at C(6) (X = SMe) may be submitted to cationic polymerization which had been reported before only for 6-alkyl-, 6-aryl-, and 6,6-dialkylpentafulvenes. This procedure does not work for pentafulvenes like 1c with strong electron-releasing substituents at C(6) (X = Me₂N). Based on bromination-elimination experiments with model compound 6, it has been shown that direct bromination of polyfulvene 2a → 10a is very efficient. This result is important in view of the synthesis of polymers 3a with pentafulvene structural elements. So far, only partial HBr elimination of polymer 10a has been achieved, while I₂ treatment of 10a gives a insoluble charcoal-like black polymer absorbing in the whole UV/VIS range.