Hydrochloric Acid → 4-nitro-1H-pyrazole-3-carbonitrile

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Reaction Steps

A suspension of 4-nitro-1H-5-pyrazolecarboxamide (7.80 g, 50 mmol) in dichloromethane (300 mL) and pyridine (30 mL) was treated with a solution of phosgene in toluene (20%, 50 mL). The mixture was stirred for 16 hours at ambient temperature then water (20 mL) was slowly added to the mixture, followed by 6 N aqueous hydrochloric acid (50 mL) and brine (15 mL). The mixture was extracted with dichloromethane (5×50 mL) and ethyl acetate (3×50 mL). The organic solutions were combined and dried over magnesium sulfate, filtered and the filtrate concentrated to a volume of about 150 mL then it was extracted with 1N aqueous hydrochloric acid (25 mL) and then brine (15 mL). The organic layer was dried over magnesium sulfate then filtered and the filtrate concentrated under reduced pressure to yield the title compound as a tan solid (6.36 g, 92%): 1H NMR (DMSO-d6, 400 MHz) δ 14.99 bs, 1H), 9.15 (s, 1H); RP-HPLC (Hypersil HS C18, 5 μm, 100 A, 250×4.6 mm; 5%-100% acetonitrile-0.05 M ammonium acetate over 25 min, 1 mL/min) tr 12.05 min; MS: MH+ 137.0

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