4282-29-5

190723-12-7

General procedure for the synthesis of 2,5-dibromothiophene-3,4-dicarboxylic acid from 3,4-thiophene dicarboxylic acid: 3,4-thiophene dicarboxylic acid (5 g, 29.04 mmol) and glacial acetic acid (40 mL) were added sequentially to a 100 mL single-necked round-bottom flask. Liquid bromine (8.9 mL, 174.24 mmol) was added to a 25 mL constant pressure dropping funnel at room temperature. The liquid bromine was slowly added dropwise to the reaction flask and the reaction continued to be stirred for 12 hours after the drop was completed. Upon completion of the reaction, the reaction solution was slowly poured into 500 mL of saturated sodium bisulfite solution and stirred until a beige solid precipitated. The solid product was collected by filtration under reduced pressure and washed with appropriate amount of cold water, and dried to obtain the beige solid product 2,5-dibromothiophene-3,4-dicarboxylic acid (8.2 g, 85.6% yield).