To a solution of 4,8-bis(2-ethylhexyl)benzo[1,2-b:4,5-b′]dithiophene (237 mg, 0.57 mmol) in dry tetrahydrofuran (11 mL) was added n-butyllithium (2.5 M in hexane, 0.5 mL, 1.25 mmol) at −78° C. After 1 hour, trimethyltin chloride (264 mg, 1.32 mmol) was added in one portion. The mixture was stirred at room temperature for 2 hours, poured into water (20 mL) and extracted with ether three times. The organic layer was washed with brine and dried over anhydrous MgSO4. Upon evaporating the solvent, a pale yellow oil was obtained (437 mg, yield 100%). Upon standing in a freezer for 2 days, pale yellow crystals emerged and were collected (326 mg, yield 77%). 1H NMR (CDCl3, 500 MHz) δ=7.51 (s, 2H), 3.07-3.23 (m, 4H), 1.96-2.07 (m, 2H), 1.21-1.50 (m, 16H), 0.94 (t, J=7.0 Hz, 6H), 0.89 (t, J=7.0 Hz, 6H), 0.46 (s, 18H).
