The general procedure for the synthesis of 5-bromothiazole-2-carboxylic acid from thiazole-2-carboxylic acid was as follows: thiazole-2-carboxylic acid (1.60 g, 12.4 mmol) was slowly added to dry tetrahydrofuran (THF, 100 mL) in a lithium diisopropylammonium (LDA, 1 M solution of THF/heptane/ethylbenzene, 26.0 mmol, 26 mL) solution. The reaction mixture was stirred at this temperature for 30 min. Subsequently, carbon tetrabromide (CBr4, 4.52 g, 13.6 mmol) was added and the reaction continued to be stirred for 2 hours. Upon completion of the reaction, the reaction was quenched by the addition of water (30 mL). After the mixture was brought to room temperature, it was diluted with saturated sodium bicarbonate (NaHCO3) aqueous solution (50 mL). The mixture was filtered through a diatomaceous earth pad and extracted with ethyl acetate (EtOAc, 50 mL). The organic layer was discarded and the aqueous layer was acidified with 1 M hydrochloric acid (HCl) to an acidic pH. The acidified aqueous solution was extracted with ethyl acetate (3 x 30 mL). The organic layers were combined, dried over anhydrous sodium sulfate (Na2SO4), and concentrated in vacuum to give 5-bromothiazole-2-carboxylic acid (0.42 g, 2.0 mmol, 16% yield).LCMS analysis: [M + H]+ = 207.90, measured value 208.0.
