The general procedure for the synthesis of 2-acetyl-5-bromothiophene from 2-acetylthiophene was as follows: 2-acetylthiophene (1.08 mL, 10 mmol), N-bromosuccinimide (NBS) (1.78 g, 30 mmol), and acetic anhydride (3.78 mL, 40 mmol) were added sequentially to a dry, 25 mL round-bottomed flask, which was equipped with a protective tube. Acetic acid (0.40 mL) was subsequently added to the mixture. The reaction mixture was stirred at 50 °C for 1 h protected from light and the color of the solution was observed to change from colorless to light yellow. Upon completion of the reaction, the mixture was cooled to room temperature and poured into 100 mL of water with continuous stirring until the acetic anhydride was completely hydrolyzed. At this point, 2-acetyl-5-bromothiophene precipitated as white crystals. The product was collected by filtration and washed in batches with 50 mL of water to give a final yield of 82%. The melting point of the product was 92-94 °C (acetone).1H NMR (300 MHz, CDCl3) data were as follows: δ 7.40 (d, J=3.9 Hz, 1H), 7.08 (d, J=3.9 Hz, 1H), 2.48 (s, 3H).
