To a solution of 4,8-dioctylbenzo[1,2-b:4,5-b′]dithiophene (782 mg, 1.89 mmol) in dry tetrahydrofuran (36 mL) was added n-butyllithium (2.5 M in hexane, 1.66 mL, 4.15 mmol) at −78° C. After 1 hour, trimethyltin chloride (877 mg, 4.40 mmol) was added in one portion. The mixture was stirred at room temperature for 2 hours, poured into water 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 (1.03 g, yield 74%). Upon standing for one week, yellow crystals emerged and were collected (413 mg, yield 29%). 1H NMR (CDCl3, 500 MHz) δ=7.51 (s, 2H), 3.22 (t, J=8.0 Hz, 4H), 1.76-1.89 (m, 4H), 1.45-1.54 (m, 4H), 1.22-1.45 (bs, 16H), 0.90 (t, J=7.0 Hz, 6H), 0.47 (s, 18H).
