502764-52-5

The general procedure for the synthesis of ethyl dithieno[3,2-b:2',3'-d]thiophene-2,5-dicarboxylate from 3,4-dibromothiophene-2,5-dicarboxaldehyde and ethyl thioglycolate was as follows: 187.6 g (0.630 mol) of 3,4-dibromothiophene-2,5-dicarboxaldehyde and 5.8 L of N,N-dimethylformamide were added to a 10 L round-bottom flask, followed by the addition of 226.3 g (1.637 mol) ethyl mercaptoacetate and 155.2 g (1.291 mol) potassium carbonate. The mixture was stirred at room temperature for 3 days. After completion of the reaction, the reaction mixture was poured into water and extracted with dichloromethane. The organic layer was separated, concentrated under reduced pressure and dried to give 152.0 g (70.9% yield) of the target product ethyl dithieno[3,2-b:2',3'-d]thiophene-2,5-dicarboxylate.

[1] Chemical Communications, 2002, # 20, p. 2424 - 2425
[2] Patent: KR101791161, 2017, B1. Location in patent: Paragraph 0204; 0217-0222
[3] Organic Syntheses, 2006, vol. 83, p. 209 - 216
[4] New Journal of Chemistry, 2018, vol. 42, # 14, p. 11458 - 11464