NOVELTY - Preparing a substituted 2,2'-dithiophene compound (I) comprises: (a) reacting a 2,2'-dithiophene compound (II) with a suitable lithium (Li) organic compound, preferably Li-alkyl or Li-alkylamide; (b) optionally exchanging Li against another metal comprising magnesium, zinc or copper by reaction with a suitable metal salt or metal organic compound; followed by (c) reacting the metallated intermediate obtained in step (a) or (b) with a suitable electrophile e.g. carbon dioxide or an aldehyde (addition reaction); and optionally (d) modifying the product obtained in step (c).    USE - The process is useful for preparing (I), which is useful to prepare the oligomer or polymer. (I) and/or the oligomer or polymer is useful: in the semiconductor device, preferably a diode, a photodiode, an organic field effect transistor and/or a solar cell, or a device containing a diode and/or a photodiode and/or an organic field effect transistor, and/or a solar cell; in the preparation of the organic semiconductor device; and as a charge-transport material, semiconducting material, electrically conducting material, photoconducting material, light emitting material, surface-modifying material, electrode material in a battery, alignment layer, or in an organic field effect transistor, integrated circuit, thin film transistor, display, radio frequency identification tag, electro- or photoluminescent device, backlight of a display, photovoltaic or sensor device, charge injection layer, Schottky diode, memory device (e.g. ferroelectric field-effect transistor), planarizing layer, antistatics, conductive substrate or pattern, photoconductor, and electrophotographic application or recording material (all claimed).    ADVANTAGE - (I) and/or the oligomer or polymer are excellent conducting materials. (I) has excellent self-organizing properties for electric or electronic applications.    DETAILED DESCRIPTION - Preparing a substituted 2,2'-dithiophene compound (I) comprises: (a) reacting a 2,2'-dithiophene compound of formula (II) with a suitable lithium (Li) organic compound, preferably Li-alkyl or Li-alkylamide; (b) optionally exchanging Li against another metal comprising magnesium, zinc or copper by reaction with a suitable metal salt or metal organic compound; followed by (c) reacting the metallated intermediate obtained in step (a) or (b) with a suitable electrophile, which is carbon dioxide or an aldehyde (addition reaction), or a hydrocarbon compound of formula (Y1a-R17) or (Y1a-R18-Z) (substitution reaction); and optionally (d) modifying the product obtained in step (c), e.g. by introducing one or more conjugating moieties (Y1), 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).    Hal = H or halo, preferably Br;    R1a, R1b = H or substituent;    Y1 = if present, phenylene, thiene, 1,2-ethylene or 1,2-ethynylene (all optionally substituted);    R2a, R2b = 1-25C alkyl, 3-12C cycloalkyl, 4-25C aryl, 5-25C alkylaryl, or 5-25C arakyl (all optionally substituted), H or halo;    R17 = hydrocarbon, or acyl or silyl residue;    R18 = CO, CO-CO, -Si(R4)(R5)-, -Ge(R4)(R5)-, -B(R10)-, -P(R10)-, or -P(R10)(=O)-;    R4, R5, R10 = 1-25C alkyl, 3-12C cycloalkyl, 4-25C aryl, 5-25C alkylaryl, or 5-25C arakyl (all optionally substituted);    Y1a, Z = leaving groups allowing for reaction with the metal thienyl intermediate formed in step (a) or (b); and    n = 0-6, preferably 0.    INDEPENDENT CLAIMS are included for:    (1) the substituted 2,2'-dithiophene compound (I) of formula (Ia) or (Ib);    (2) oligomer or polymer of formula (A), comprising at least 2 structural units of (I);    (3) a semiconductor device comprising (I); and    (4) process for the preparation of an organic semiconductor device, comprising applying a solution and/or dispersion of (I), and/or the oligomer or polymer, in an organic solvent to a suitable substrate and removing the solvent.    R1, R11 = e.g. H or Si(R6a)(R4a)-R5a (when n is not 0);    R2, R22 = e.g. 1-25C alkyl ( optionally substituted);    R6a, R6b = e.g. 1-25C alkyl or 3-12C cycloalkyl; either    R3a, R3b = R7a, or R7b; or    R3a+R3b = -C(=N-R9)-C(=N-R99)-; either    R7a, R7b = e.g. 1-25C alkyl or 5-25C aralkyl (both optionally substituted); or    R7a+R7b = e.g. -C(=O)- or -C(=N-R11a)-;    M = e.g. Si;    Y2 = e.g. -C?=C-;    R8, R88 = e.g. H;    R9+R99 = e.g. phenyl group;    R10 = e.g. 1-25C alkyl or 5-25C arakyl (both optionally substituted);    R11a = R8 or OR8; either    one of R12, R13 = H; and    the other or both of R12, R13 = substituents; or    R12+R13 = 2-25C divalent hydrocarbon residue (optionally substituted and/or interrupted); either    R14 = substituent; or    2, or 3 neighboring residues of R14 = 4-25C divalent or trivalent hydrocarbon residue (optionally substituted and/or interrupted);    R2g, R3g = e.g. 1-25C (halo)alkyl, or 5-10C aryl;    R1g = e.g. H, or 1-25C (halo)alkyl;    p = 0-6; and    m = 0-4.    Full Definitions are given in the DEFINITIONS (Full Definitions) Field. With provisos.