HCID 178524578, compound → HCID 178526711, compound

Participants

Reaction Conditions

Reaction Steps

A 3-L three-neck round-bottomed flask equipped with a mechanical stirrer, addition funnel and nitrogen inlet was purged with nitrogen and charged with 3-nitropyrazole-5-carboxylic acid (28.0 g, 178 mmol) and THF (420 mL) and cooled to −5° C. using an ice/acetone bath. Borane-THF complex solution (1.0 M, 535 mL, 535 mmol) was added at a rate that maintained the internal reaction temperature below 5° C. After the addition was complete the cooling bath was removed and the reaction was stirred at room temperature for 18 h. After this time the reaction was cooled to −5° C. using an ice/acetone bath, water (70 mL) and 4N hydrochloric acid (70 mL) was added and the reaction was stirred at reflux for 1 h in order to destroy the borane complex with pyrazole. The reaction was cooled to room temperature and concentrated under reduced pressure to a volume of approximately 30 mL. Ethyl acetate (175 mL) was added and the mixture stirred for 15 min. The aqueous layer was separated and extracted with ethyl acetate (4×200 mL). The combined organic layers were washed with saturated aqueous sodium bicarbonate (2×50 mL), brine (50 mL) and dried over sodium sulfate, the drying agent was removed by filtration, and the filtrate concentrated under reduced pressure to afford 124a in a 94% yield (24.0 g) as a light yellow solid: 1H NMR (300 MHz, DMSO-d6) δ 13.90 (br s, 1H), 6.87 (s, 1H), 5.58 (t, 1H, J=5.4 Hz), 4.53 (d, 2H, J=5.1 Hz); MS (ESI+) m/z 144.0 (M+H)

Provenance & Evidence