The present invention relates to a 'one-pot synthesis process' for preparing thiophenes from thiophene monomers with two leaving groups under metal catalysis. What is disclosed is a process for polymerizing at least one thiophene derivative with at least two leaving groups, the polymerization proceeding by means of an organometallic thiophene compound and of at least one catalyst, characterized inthat a mixture which comprises the at least one thiophene derivative and the at least one catalyst is admixed with at least one metal and/or at least one organometallic compound.