Step 1: 4-Pyrazoleboronic acid pinacol ester (200 mg, 1.03 mmol), 2-bromoacetamide (213 mg, 1.54 mmol) and cesium carbonate (1.27 g, 3.92 mmol) were dissolved in acetonitrile (5.0 mL), and the reaction was stirred for 3 hours at 90°C. After the reaction was completed, it was cooled to room temperature, the reaction mixture was diluted with water and extracted twice with ethyl acetate. The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated in vacuum to afford pinacol ester of 1-acetamido-4-boronic acid (174 mg, 67% yield) as a white solid, which could be used in the next reaction without further purification.1H-NMR (400 MHz, CDCl3): δ 7.89 (s, 1H), 7.76 (s, 1H), 6.21 and 5.41 ( brs, 2H), 4.83 (s, 2H), 1.32 (s, 12H).
