The present invention relates to a process for preparing compounds of the formula (I), ##STR00001## where n is an integer from 2 to 5, R.sup.1 is H or a C.sub.1-C.sub.20-alkyl group which may be interrupted by one or more O or S atoms, silylene, phosphonoyl or phosphoryl groups and Ar is substituted or unsubstituted 1,4-phenylene, 2,7-fluorene or 2,5-thiophene, with Ar being able to be identical or different, semiconductive layers comprising these compounds and their use in semiconductor technology.