4,5-Dihydro-3-propylamino-5-oxo-1-(2,4,6-trichloro-phenyl)-1H-pyrazole (21.9 g, 68.3 mmol) was dissolved in a mixture of tetrahydrofuran (170 ml) and pyridine (34 ml) and the solution was cooled in an ice-bath. m-Nitrobenzoyl chloride (25.35 g, 136.7 mmol) was dissolved in tetrahydrofuran (40 ml) and the solution was added dropwise to the stirred, cooled mixture. Stirring was continued at room temperature for 19 hrs. A further quantity of m-nitrobenzoyl chloride (10%) was added and the mixture was stirred for 2 hrs to complete the reaction. The mixture was poured into dilute hydrochloric acid (31) and the oily solid was extracted with ethyl acetate. The extract was washed with water and dried (MgSO4). The solvent was removed by evaporation and replaced with ethanol (300 ml). A solution of sodium hydroxide (13.7 g, 324 mmol) in water (40 ml) was added dropwise and the mixture was stirred for 1 hr. The mixture was poured into dilute hydrochloric acid (21) and the resulting oil was extracted with ethyl acetate. The extract was washed with water and dried (MgSO4). The solvent was evaporated under reduced pressure to give a resin, 33.0 g, ca 100%. This was used in the next stage without purification.
