Phosphorus tribromide → 5-(Bromomethyl)-1-methyl-3-nitro-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

A 25-mL round-bottomed flask equipped with a magnetic stirrer and reflux condenser was purged with nitrogen and charged with 156c (0.56 g, 3.6 mmol) and chloroform (10 mL). The reaction was cooled to 0° C. using an ice bath and phosphorous tribromide (0.98 g, 3.6 mmol) was added dropwise. The cooling bath was removed and the reaction stirred at reflux for 3 h. After this time, the reaction was cooled to 0° C. and diluted with methylene chloride (25 mL). Saturated aqueous sodium bicarbonate was added until a pH of 8.5 was reached. The layers were separated, and the aqueous layer was extracted with methylene chloride (3×25 mL). The combined organic layers were washed with brine (30 mL), dried over sodium sulfate and concentrated under reduced pressure to afford a quantitative yield (0.79 g) of 156d as an off-white solid: MS (ESI+) m/z 222.1 (M+H).

Provenance & Evidence