Acetic Anhydride → HCID 58763934, compound

Participants

Reaction Steps

1-(2-Chlorophenyl)-5-(4-chlorophenyl)-4-hydroxy-1H-pyrazole-3-carboxylic acid I-6c (572.0 g, 1.64 mol) was combined with 8 liters of methylene chloride to give an off-white suspension. N,N-Diisopropylethylamine (427.9 g, 3.29 mol) was added over 15 minutes while keeping the temperature between 20–25° C. A clear yellow solution resulted. Acetic anhydride (334.5 g, 3.24 mol) was added over 5 minutes keeping the temperature between 20–25° C. The reaction was stirred at room temperature for 16 hours. The crude reaction solution was washed twice with 4 liters portions of 0.5 M citric acid and once with 4 liters of brine. The crude solution was concentrated in vacuo to a total volume of 1 liter. This milky suspension was then added to 4 liters of hexanes causing the desired product to precipitate instantly. The solids were granulated for 30 minutes and then collected by filtration. The filtercake was rinsed with 3 liters of hexanes and then air-dried for 16 hours. The isolated product was then further dried at 60° C. and 8 mm for 2 hours. 4-Acetoxy-1-(2-chlorophenyl)-5-(4-chlorophenyl)-1H-pyrazole-3-carboxylic acid I-6d (601.6 g, 94%) was isolated as a powdery, off-white solid.

Provenance & Evidence