Acetic Anhydride → N-(3-chloro-1H-pyrazol-4-yl)acetamide

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

A 100-mL 3-neck round bottom flask was charged with 3-chloro-1H-pyrazol-4-amine.hydrochloride (5.00 g, 32.5 mmol) and water (25 mL). Sodium bicarbonate (10.9 g, 130 mmol) was added slowly over 10 minutes (off-gassing during addition), followed by tetrahydrofuran (25 mL). The mixture was cooled to 5° C. and acetic anhydride (3.48 g, 34.1 mmol) was added over 30 minutes while maintaining the internal temperature at <10° C. The reaction was stirred at 5° C. for 1 hour, at which point thin layer chromatography (TLC) analysis [Eluent: ethyl acetate (EtOAc)] indicated that the starting material had disappeared and a major product was exclusively formed. The reaction mixture was diluted with ethyl acetate (25 mL) and water (25 mL). The layers were separated and the aqueous layer was extracted with ethyl acetate (3×25 mL). The combined organic layers were concentrated to afford an off-white solid, which was suspended in methyl tert-butylether (MTBE, 20 mL), stirred for 1 hour, and filtered. The solid was rinsed with methyl tert-butylether (20 mL) and further dried under vacuum at room temperature (about 22° C.) for 4 hours to give a white solid (4.28 g, 83%): mp 162-164° C.; 1H NMR (400 MHz, DMSO-d6) δ 12.90 (bs, 1 H), 9.49 (s, 1 H), 7.97 (s, 1 H), 2.02 (s, 3 H); 13C NMR (101 MHz, DMSO-d6) δ 167.81, 130.07, 123.72, 116.73, 22.58; EIMS m/z 159 ([M]+).

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