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1. N-bromosuccinimide (NBS, 2.63 kg, 14.79 mol) was added batchwise to a solution of 1-tert-butylpyrazole (1.75 kg, 14.09 mol) in dichloromethane (12.9 kg) in an ice bath at 0°C to 10°C. The reaction was carried out by gas chromatography (GC). 2. The reaction mixture was kept stirred at 0 °C until the content of 1-tert-butylpyrazole was below 30% as shown by gas chromatography (GC) analysis. 3. the reaction mixture was gradually warmed to room temperature with continued stirring until the GC analysis showed that the content of 1-tert-butylpyrazole was less than 1.0%. 4. Upon completion of the reaction, 10% aqueous sodium bisulfite was added to the reaction mixture until it no longer showed blue color when detected using KI-starch test paper. 5. The organic phase was washed sequentially with 5% sodium chloride solution and saturated brine. 6. Evaporate the organic phase under pressure to obtain 4-bromo-1-tert-butyl-1H-pyrazole as a brown liquid (2.67 kg, yield 93.4%; GC purity 99.1%).

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