124638-53-5

251-41-2

124638-53-5

S1. Thieno[3,2-b]thiophene (5 g, 35.7 mmol) was dissolved in a solvent mixture of glacial acetic acid (36 ml) and chloroform (10 ml). Bromine (28.5 g, 180.56 mmol) was added slowly dropwise at room temperature and stirring was continued for 30 min after completion of the dropwise addition. The reaction mixture was then heated to 78°C refluxing overnight. After completion of the reaction, it was cooled to room temperature and the reaction mixture was washed with water to precipitate a white solid product. The product was washed sequentially three times each with water and methanol and finally dried under vacuum at room temperature to afford tetrabromothieno[3,2-b]thiophene (Compound 1) as a white solid with mass spectrometry detection [M+] = 455.0 in 95% yield.