Substituted oligo-or polythiophenes

A process for the preparation of a substituted 2,2'-dithiophene is described, which process comprises the steps (a), (c) and optional steps (b) and (d): a reaction of a compound of the formula: with a suitable lithium organic compound, preferably Li-alkyl or Li-alkylamide; b) optional exchange of lithium against another metal selected from Mg1 Zn and Cu; c) reaction of the metallated intermediate obtained in step (a) or (b) with a suitable electrophil, which is CO2 or an aldehyde (addition reaction), or a compound Y'-R17 or Y'-R18-Z (substitution reaction), where R17 and R18 are as defined in claim 1; and optionally d) modification of the product obtained in step (c), e.g. by introducing one or more conjugating moieties Y ring closure between suitable monovalent residues R17, exchange or extension of functional groups or substituents such as addition to carbonyl or substitution of carbonyl in R17 or R18. The products, including or corresponding polymers, are excellent conducting materials