The synthesis of a precursor oligocene, particularly pentacene, is a two-step process. In the first step the Diels-Alder adduct of the a,b-dihydro-a,b-etheno-oligocene with a 1,1-dialkoxy-cyclopentadiene is formed. In the second step this Diels-Alder adduct is converted into the precursor oligocene, in that first the corresponding keto-compound is formed, which may be eliminated thereafter. The resulting precursor oligocene can be converted to the oligocene with a heat treatment, particularly after providing a solution hereof on a substrate. It is suitable for use as semiconductor material in a thin-film transistor. Formula (I). ##STR00001##