Three new heterocyclic parent compounds, 2, 3-dihydrothieno [2, 3-b][1, 4] dithiine (TDT), 2, 3-dihydrothieno [3, 2-b][1, 4] oxathiine (TOT), and 2, 3-dihydrothieno [2, 3-b][1, 4] oxathiine, have been synthesized by acid-catalyzed transformations starting from 3-methoxythiophene. Two of the new compounds have been transformed to the corresponding end-capped dimeric, trimeric and tetrameric oligothiophenes. These oligomers show very stable cationic and dicationic states as judged by cyclic voltammetry, and their UV-Vis spectra are considerably red-shifted compared to previously synthesized end-capped oligomers.