General procedure for the synthesis of 2-bromo-3-hexylthiophene from 3-hexylthiophene: A 1 M solution of 3-hexylthiophene (8a) in DMF was cooled to 0 °C under light-avoidance conditions, followed by the addition of N-bromosuccinimide (NBS, 1.0 equiv). The reaction mixture was slowly warmed to room temperature with continuous stirring overnight. After completion of the reaction, the reaction solution was diluted with dichloromethane (DCM). The organic phase was washed sequentially with water and brine, the aqueous phase was combined and back-extracted with DCM. All organic phases were combined, dried with anhydrous magnesium sulfate (MgSO4) and concentrated under reduced pressure to remove the solvent. The crude product was purified by silica gel column chromatography (eluent: petroleum ether) to afford 2-bromo-3-hexylthiophene (7a) as a colorless oil in 99% yield.1H NMR (300.13 MHz, CDCl3) δ (ppm): 7.18 (d, 3J = 5.5 Hz, 1H, H-9), 6.79 (d, 3J = 5.5 Hz, 1H, H-8). 2.56 (t, 3J = 7.7 Hz, 2H, H-6), 1.63-1.51 (m, 2H, H-5), 1.40-1.24 (m, 6H, H-4 to H-2), 0.89 (t, 3J = 6.8 Hz, 3H, H-1).
