Acetic Acid → 1-(2-Benzoyl-4-chlorophenyl)-3,5-pyrazole dicarboxylic acid, dimethyl ester

Participants

Reaction Steps

To a solution of 13.1 g. (34.5 mmol) of the final product of Example 2 in 50 ml. HOAc and 75 ml. of 3 N HCl, stirred at 3°, was added dropwise so as to maintain a temperature of 3°-6°, a solution of 2.50 g. (36.3 mmol) of sodium nitrite in 25 ml. H2O. When the addition was complete, the reaction was stirred at 3° for 20 minutes. A fresh solution of cuprous chloride in concentrated hydrochloric acid (prepared from 27 g. cupric sulfate pentahydrate*) was mixed with an equal volume of water and cooled to 3°. The diazotized solution, which had to be kept cold (<5°) at all times, was slowly poured into the vigorously stirred 5° cuprous chloride solution in several portions, in order to control foaming.

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