Ammonium Chloride → 5-Fluoropyridine-2-carboxamide

Beteiligte Stoffe

Reaktionsschritte

Take up 5-Fluoropyridine-2-carboxylic acid (3.82 g, 27.1 mmol) in THF (67.7 mL). Add N-hydroxysuccinimide (3.43 g, 29.8 mmol) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (5.71 g, 29.8 mmol). Add DMF (15 mL) to dissolve the gum formed. Stir for 3 hours at room temperature before adding ammonium chloride (2.17 g, 40.6 mmol). Bubble in ammonia gas for five minutes. Seal the reaction vessel and stir the reaction mixture overnight before concentrating. Take the solid up in water (150 mL) and extract with ethyl acetate (4×225 mL). Dry the organic layer over Na2SO4, filter and concentrate. Purify by flash chromatography, eluting with 25% ethyl acetate, 1% (2.0 M NH3 in methanol) and 74% dichloromethane to give the title compound (3.06 g, 80.7%): TOF MS EI+ 140.0 (M)+, TOF MS EI+ 97.0 (M+B—CONH2), HRMS calcd for C6H5N2OF 140.0386, found 140.0394, time 3.4 min; HPLC [YMC-Pack Pro C-18 (150×4.6 mm, S-5 microm), 0.1% TFA/acetonitrile in 0.1% TFA/water at 1.0 mL/min, 5-95% over 19 min], tR=7.1 min, 100% purity.

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