Sulfamic Acid → Antipyric acid

Participants

Reaction Steps

To a stirred solution of the commercially available 1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carbaldehyde (CAS No. 950-81-2) (51.6 g) in tetrahydrofuran (THF) (1 L) at 0° C. was added a solution of sulfamic acid (48.5 g) in water (640 mL). A solution of sodium chlorite (43.7 g) in water (500 mL) was added slowly maintaining the temperature below 8° C. The reaction mixture was allowed to warm to room temperature. After 5 hours, the pH of the reaction was adjusted to 8 with a 6 N aqueous solution of sodium hydroxide (NaOH). The mixture was extracted with ethyl acetate (EtOAc). The aqueous layer was acidified to pH 4 with a 6N solution of hydrochloric acid (HCl) and extracted with dichloromethane (DCM). The combined DCM extracts were washed sequentially with 5% aqueous sodium sulfite and saturated brine, dried over sodium sulfate (Na2SO4) and concentrated under reduced pressure. The crude solid was triturated with methanol (MeOH) to give the title compound (17 g).

Provenance & Evidence