GENERAL STEPS: To a solution of commercially available 5-bromothiophene-2-carboxylic acid (10 g, 0.048 mol) and cesium carbonate (31.6 g, 0.096 mol) in N,N-dimethylformamide (100 mL) was slowly added ethyl iodide (11.3 g, 0.072 mol). The reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the reaction was quenched with water and extracted with ethyl acetate. The organic layer was washed with saturated saline, dried over anhydrous sodium sulfate, filtered and concentrated to give the crude product. The crude product was purified by silica gel column chromatography to afford pure ethyl 5-bromothiophene-2-carboxylate (9 g, 80% yield) as a light yellow oil.ESI-MS m/z: 234.1 [M + H]+ (calculated value: C7H7BrO2S).1H NMR (CDCl3, 400 MHz): δ 7.54-7.53 (d, J = 4 Hz, 1H, Harom), 7.07-7.53 (d, J = 4 Hz, 1H, Harom). Harom), 7.07-7.06 (d, J = 4 Hz, 1H, Harom), 4.35-4.30 (m, 2H, O-CH2-CH3), 1.38-1.34 (m, 3H, O-CH2-CH3).
