* All experimental methods are cited from the reference, please refer to the original source for details. We do not guarantee the accuracy of the content in the reference.
With hydrogen bromide; copper(I) bromide; sodium nitrite In water at 70℃; for 0.5 h;
S2. 1.9 g of 3-amino-5-methylpyrazole (2),15mL concentrated hydrobromic acid,2.8g cuprous bromide mixed into 100mL three-necked flask,Heated to 70 ;Take about 1.5g sodium nitrite dissolved in 5mL water,Using a constant pressure funnel slowly dropping into a three-necked flask;After the addition is completed,The reaction solution was stirred at 70 for 30min,After cooling to room temperature, 20 mL THF was added,20mL water;The mixture was extracted three times with 30 mL of ether, the organic layer was washed with sodium thiosulfate solution, dried over magnesium sulfate, filtered through silica gel,The solvent was distilled off under reduced pressure to give 3-methyl-5-bromopyrazole (3) in a yield of 62percent;
52%
at 70℃; for 0.5 h;
1.9 g of 3-amino-5-methylpyrazole (19), 15 mL of concentrated hydrobromic acid, and 2.8 g of cuprous bromide were placed in a 100 mL three-necked flask and heated to 70 °C.Approximately 1.5 g of sodium nitrite was dissolved in 5 mL of water and slowly added dropwise to a three-necked flask using a constant pressure funnel.After the completion of the addition, the reaction solution was stirred at 70 ° C for 30 min, then cooled to room temperature, and 20 mL of THF (tetrahydrofuran) and 20 mL of water were added.It was extracted three times with 30 mL of diethyl ether. The organic layer was washed with sodium thiosulfate solution and dried over magnesium sulfate.After filtration with silica gel, the solvent was evaporated under reduced pressure to give 1.7 g of 3-methyl-5-bromopyrazole (20) in a yield of 52percent.
Reference：
[1] Patent: CN104844567, 2017, B, . Location in patent: Paragraph 0031; 0035; 0040; 0045
[2] Patent: CN108191822, 2018, A, . Location in patent: Paragraph 0059; 0060; 0061
2
[ 112422-59-0 ]
[ 57097-81-1 ]
Reference：
[1] Journal of the American Chemical Society, 1988, vol. 110, # 5, p. 1356 - 1366
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