posted on 1999-12-29, 00:00authored byChristoph A. Briehn, Thomas Kirschbaum, Peter Bäuerle
The solid-phase synthesis of regioregular head-to-tail-coupled oligo(3-arylthiophene)s has been
achieved in high yield and purity by using a traceless silyl ether linkage. In the first step, the
solution-phase synthesis of this class of conjugated oligomers was investigated. Benzyl alcohol was
chosen to serve as a mimic for the anchoring group of the hydroxymethyl-substituted polystyrene
matrix. The development of a novel regioselective iodination process for silyl-protected thiophenes
faciliates the successful application of the solution-phase protocol to the solid phase. Satisfactory
loading was obtained by reaction of chlorosilyl-functionalized 3-arylthiophene with hydroxymethyl
polystyrene in the presence of imidazole. The suitability of the following iterative halogenation
and Suzuki cross-coupling sequence is illustrated by the preparation of a quater(3-arylthiophene),
the first regioregular head-to-tail-coupled oligothiophene that is synthesized on solid support.
Removal of the conjugated oligomers from the solid support could be effectively achieved by
treatment with tetrabutylammonium fluoride.