a) Preparation of 1,2-diphenyl-4-n-butyl-3-hydroxy-methyl-3,5-
dioxopyrazolidine:
308 g (1 mole) of 1,2-diphenyl-4-n-butyl-3,5-dioxo-pyrazolidine are refluxed
during 2 hours in a mixture of 900 ml absolute ethanol and 100 ml of a
solution of formaldehyde 40% in water. The mixture is allowed to cool
overnight in a refrigerator and after filtration, washing with alcohol and
drying; crystals (305 g) are obtained. Melting point: 146-147°, yield 90%.
b) Preparation of para-chlorobenzoic ester of 1,2-di-phenyl-4-n-butyl-4-
hydroxymethyl-3,5-dioxopyrazolidine:
In a 2 liter 3-necked flask fitted with mechanical stirrer, dropping funnel and
entry for nitrogen circulation, 338 g (1 mole) of the 1,2-diphenyl-4-n-butyl-3-
hydroxy-methyl-3,5-dioxopyrazolidine are added. The resultant mixture is
dissolved in a mixture of 200 ml pyridine and 600 ml dimethylformamide.
When the temperature reaches 0°C, 175 g (1 mole) of p-chlorobenzyl chloride
previously subjected to a mild nitrogen flow are added dropwise under
stirring. Once the addition of all the amount of the acid chloride is completed,
the material is maintained under stirring during one hour and is then allowed
to stand during 24 hours in a refrigerator and finally 24 hours at room
temperature. The temperature is then raised to 30-40°C to dissolve the
precipitate which occurred. The mixture is then cooled and poured in ice-water
containing hydrogen chloride (1:1). Stand 24 hours, filter and wash several
times with water and once with cold alcohol. Following two recrystallisazions
from alcohol, there are obtained 380 g of perfect prismatic crystals melting at
90-91°C. Esterification yield: 80%.
