preparation | dissolve 1.7g 3-methyl -5-bromopyrazole in 20ml 0.1M hydrochloric acid, place in a 100mL three-mouth flask, and heat to 50 ℃; Dissolve about 1.5g of potassium permanganate in 5mL of water, and slowly drop it into the three-mouth flask using a constant pressure funnel. After the feeding is completed, the reaction liquid is stirred at 70 ℃ for 30min, after cooling to room temperature, the pH of the solution is adjusted to acidic, 20mL EtOAc is added, extraction is carried out three times, the pH of the organic layer is adjusted to alkaline, and water is added to wash to obtain 5-bromo-1H-3-pyrazoloic acid with a yield of 85% |