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2,6-Dibromo-4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b'']dithiophene is a solution-processed small molecule used in highly efficient organic solar cells.

General procedure for the synthesis of 2,6-dibromo-4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-B:4,5-B']dithiophene from 4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-B:4,5-B']dithiophene: 10 g of dichloromethane (DCM) was added to a round bottom flask, followed by 2.3 g of 4,8-bis[(2- ethylhexyl)oxy]benzo[1,2-B:4,5-B']dithiophene and allowed to dissolve completely. Another 4.6 g of liquid bromine was dissolved in 15 g of DCM to prepare a bromine solution. The bromine solution was slowly added dropwise to a round-bottomed flask containing the raw material under ice bath conditions. After the dropwise addition was completed, the ice bath was removed and the reaction was allowed to continue at 10 °C for 24 h until the color of the solution became significantly lighter. The progress of the reaction was monitored by thin layer chromatography (TLC) and the reaction was terminated after confirming complete consumption of the feedstock. Product refinement step: the solvent was first removed by reduced pressure distillation using a rotary evaporator, followed by dissolving the crude product in hexane and drying by adding anhydrous MgSO4. After filtration and concentration, the target product 2,6-dibromo-4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-B:4,5-B']dithiophene was obtained in 90% yield.

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