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With hydrogenchloride; tin(II) chloride dihdyrate; In methanol; at 20℃; for 6.0h;
Tin (II) chloride (12.8 g, 68 mmol) was added in portions to a solution of 3-chloro-5-nitro- lH-pyrazole (2.0 g, 13.6 mmol) in methanol (200 mL) and cone. HCl (10 mL) at 0 C. The reaction mixture was stirred at room temperature for 6 hours, and the organic solvent was removed under reduced pressure. The residue was diluted with water (20 mL), neutralized to pH 7 with Na2C03, then extracted with EtOAc (3 x 50 mL). The combined organic phases were washed with brine, dried over anhydrous sodium sulfate, filtered and concentrated to give the title compound (1.4 g, 87%), which was used without further purification. 1H NMR (400 MHz, DMSO-d6): delta 11.55 (bs, 1H), 5.26 (s, 2H), 5.21 (s, 1H).