1 Department of Chemistry and Biochemistry, Concordia University, 7141 rue Sherbrooke O., Montréal, QC, H4B 1R6, Canada.
2 Department of Physics, Concordia University, 7141 rue Sherbrooke O., Montréal, QC, H4B 1R6, Canada.
3 Centre for Research in Molecular Modeling (CERMM), Centre for NanoScience Research (CeNSR), Concordia University, 7141 rue Sherbrooke O., Montreal, QC, H4B 1R6, Canada.
4 Center for Green Chemistry and Catalysis, McGill University, 801 rue Sherbrooke O., Montréal, QC, H3A 0B8, Canada.

A library of symmetrical linear oligothiophene was prepared employing decarboxylative cross-coupling reaction as the key transformation. Thiophene potassium carboxylate salts were used as cross-coupling partners without the need of co-catalyst, base, or additives. This method demonstrates complete chemoselectivity and is a comprehensive greener approach compared to the existing methods. The modularity of this approach is demonstrated with the preparation of discreet oligothiophenes with up to 10 thiophene repeat units. Symmetrical oligothiophenes are prototypical organic semiconductors where their molecular electrical doping as a function of the chain length can be assessed spectroscopically. An oligothiophene critical length for integer charge transfer was observed to be 10 thiophene units, highlighting the potential use of discrete oligothiophenes as doped conduction or injection layers in organic electronics applications.