6,6'-Dibromo-[3,3'-diindolinylidene]-2,2'-dione (1.0 g, 2.93 mmol) and freshly dried potassium carbonate (2.43 g, 17.59 mmol) were placed in a 100 mL three-neck flask under inert atmosphere. Anhydrous DMF (20 mL) was added to the suspension followed by 2-ethylhexyl bromide (1.70 g, 8.79 mmol). The reaction mixture was heated to 100 °C and stirred continuously for 15 hours. After completion of the reaction, the mixture was poured into water (500 mL) and the organic phase was extracted with dichloromethane. The organic layer was sequentially washed with brine, dried over anhydrous magnesium sulfate, and subsequently concentrated under reduced pressure to remove the solvent. The crude product was purified by silica gel column chromatography using dichloromethane and hexane (2:3, v/v) as eluent to afford 1.37 g of the brown solid product, 6,6'-dibromo-1,1'-bis(2-ethylhexyl)-[3,3'-bis(2-ethylhexylidene)-[3,3'-bianilidinylidene]-2,2'-dione, in 90% yield.
![(E)-6,6'-dibromo-[3,3'-biindolinylidene]-2,2'-dione](/CAS/20180703/GIF/1147124-21-7.gif)
