Fluorination of thiophenedicarboxylic acid with sulfurtetrafluoride in the presence of anhydrous hydrogen fluoride provided mono and bis(trifluoromethyl)thiophenes in moderate yields. Ethynylthiophenes and ethynylfurans containing trifluoromethyl groups were prepared via 2,2-dichloro-1-fluorovinyl compounds. In polymerizations using transition metal catalysts, 3-ethynylthiophenes gave polymers in