As key components of flexible organic electronics, the synthesis ofpolythiophenes via less toxic and more cost-effective routes is demanded. Anefficient synthetic route for the production of thienyl-containing homopolymers andcopolymers has been developed.The synthetic approach consists of: i) the synthesis in high yield and highpurity of thienyl borane monomers protected with N-methyliminodiacetic acid(MIDA) via C-H electrophilic borylation. This reaction uses a combination ofinexpensive reagents BCl3, AlCl3, and 2,6-dichloropyridine (Cl2Py) for theregioselective electrophilic aromatic substitution of thiophenes, followed by additionof a second aprotic amine pre-esterification to reduce the Brønsted acidity of thereaction mixture. In situ esterification provided the desired thienyl MIDA boronateester monomers in one-pot at room temperature. ii) Subsequent Suzuki-Miyaurapolymerisation of the synthesised monomers to produce well defined thienylcontainingpie-conjugated polymers in high molecular weight and high yields.Key reaction parameters for successful Suzuki-Miyaura polymerisation ofthienyl-derived MIDA boronate esters under mild temperatures (i.e., 55 °C in THF)were found: a) an optimal monomer:H2O:base ratio, which enables controlledhydrolysis of the BMIDA moiety into its corresponding boronic acid at appropriaterates for high fidelity polymerisation. b) Nature of the base, where K3PO4 providedthe best results for production of homopolymers (e.g., rr-P3HT), or KOH whichgave excellent results for the formation of copolymers across a range ofelectronically different comonomers (e.g., pCPDT-BT). Thus, it is demonstrated thatthe approach is a general strategy for the highly efficient production of thienylcontainingpie-conjugated regioregular, regiosymmetric and Donor-Acceptorpolymers.