Spiro oligothiophenes.

ABSTRACT

Linear oligothiophenes, containing annelated dithieno[2,3-b3',2'-d]thiophene units, undergo unexpected spirocyclizations upon treatment with trifluoroacetic acid. The resultant spiro oligothiophenes possess novel structures in which the spiro or dispiro skeleton is within an all-thiophene/dihydrothiophene framework. Racemic dispiro octathiophene is obtained with high diastereoselectivity and in high yield.