Synthesis
General procedure for the synthesis of 4-bromo-2-acetylthiophene from 2-acetylthiophene: In a 250 mL single-necked round-bottomed flask, 2-acetylthiophene (3.00 g, 23.81 mmol), anhydrous aluminum chloride (9.53 g, 71.43 mmol), and carbon tetrachloride (80 mL) were added, and the mixture was cooled to -40 °C. After 10 min, a slow dropwise addition of bromine ( 3.81 g, 23.81 mmol) in carbon tetrachloride (20 mL) was added slowly and stirred at room temperature for 0.5 h after completion of the addition. After 12 hours of reaction, TLC monitoring showed complete consumption of the feedstock. The reaction mixture was carefully poured into a mixture of saturated sodium hydroxide solution and crushed ice and extracted with ethyl acetate (75 mL x 3). The organic phases were combined, washed twice with saturated brine and dried over anhydrous magnesium sulfate. Purification by column chromatography (petroleum ether:ethyl acetate = 500:1) gave a pale yellow oily liquid product (2.74 g) in 72.6% yield.
References
[1] Bioorganic and Medicinal Chemistry Letters, 2004, vol. 14, # 15, p. 4037 - 4043
[2] Journal of Heterocyclic Chemistry, 1982, vol. 19, p. 713 - 716
[3] Patent: CN103408540, 2016, B. Location in patent: Paragraph 0096; 0126; 0127
[4] Chemistry of Heterocyclic Compounds, 2013, vol. 49, # 3, p. 386 - 391
[5] Khim. Geterotsikl. Soedin., 2013, # 3, p. 416 - 422
