反应详情

To a stirring solution of 5-amino-3-(2-thienyl)pyrazole (500 mg, 3.03 mmol) in THF (10 mL) was added N-bromosuccinimide (592 mg, 3.33 mmol) in one portion. The reaction mixture was stirred at room temperature for 3 h, then the solvent was evaporated and the residue was taken up in ethyl acetate. The organic layer was washed successively with 1M aqueous sodium thiosulfate, twice with a saturated aqueous solution of sodium bicarbonate, and brine, then it was dried over sodium sulfate, filtered, and adsorbed on silica gel. Purification on silica gel with 0-10% MeOH in CH2Cl2 as eluent provided 686 mg (93%) of 4-bromo-5-thiophen-2-yl-2H-pyrazol-3-ylamine as a dark foam. 1H-NMR (d6-DMSO) δ: 11.9 and 12.4 (2 broad s, 1H, NH+tautomer), 7.4-7.65 (m, 2H), 7.05-7.2 (m, 1H), 4.8 and 5.3 (2 broad s, 2H, NH2+tautomer).

1. customthe solvent was evaporated
2. washThe organic layer was washed successively with 1M aqueous sodium thiosulfate, twice with a saturated aqueous solution of sodium bicarbonate, and brine
3. dry with materialit was dried over sodium sulfate
4. filtrationfiltered
5. customPurification on silica gel with 0-10% MeOH in CH2Cl2 as eluent