2,2',2'',2'''-(3,6-bis(dodecyloxy)benzene-1,2,4,5-tetrayl)tetrathiophene

Acetic acid, glacial

Chloroform, Supelco

A three-necked round-bottomed flask was fitted with a stir bar and a condenser. Chloroform (4mL) and acetic acid (4mL), 2,2',2'',2'''-(3,6-bis(dodecyloxy)benzene-1,2,4,5-tetrayl)tetrathiophene (0.250 g, 0.322 mmol, 1 eq.) and N-bromosuccinimide (0.252 g, 1.417 mmol, 4.4 eq.) were added to the three-necked flask and the reaction was heated in an oil bath at 75° Celsius. The reaction was monitored with ¹H NMR to check for reaction completion. Upon completion, the reaction was cooled and diluted with chloroform, washed with saturated sodium thiosulfate (75mL, 3x) and saturated sodium chloride (75mL, 3x). The organic layer was dried over magnesium sulfate and filtered, concentrated in vacuo, and taken up in hot methanol. Upon cooling, the product was separated by filtration. The product was confirmed by thin layer chromatography (hexanes, Rf = 0.17) and was collected as a brown powder (0.263 g, 0.241 mmol, 75% yield).

Acetic acid greatly accelerates this reaction. Brominating in chloroform yielded little to no product. The reaction was generally done in five hours, but was capable of over-bromination!

Please note: NBS must be recrystallized from water before being used in order to receive the best results. 

¹H NMR (400 MHz, CDCl₃): δ 6.887 (d, 4H, J = 4.0 Hz), 6.618 (d, 4H, J = 3.6 Hz), 3.231 (t, 4H, J = 6.4 Hz), 1.220 (m, 32H), 0.992 (m, 8H), 0.880 (t, 6H, J = 6.8 Hz)