Hydrochloric Acid → 3-Methyl-1-(2,4,6-trichlorophenyl)-1H-pyrazol-5-amine

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Reaction Steps

To a solution of 0.51 g (22.0 mmol) of sodium in methanol was added 1.66 g (20.0 mmol) of 5-methylisoxazole. The reaction mixture as refluxed for 8 hours and then stirred overnight at room temperature. Then 4.23 g (20.0 mmol) of 2,4,6-trichlorophenylhydrazine was added and the reaction mixture was again refluxed for 4 hours. A second portion of sodium in methanol was added and reflux was continued for 24 hours. The reaction mixture was taken up with ether and dilute hydrogen chloride. The organic extracts were washed with dilute hydrogen chloride and brine, and then dried with magnesium sulfate and evaporated to give crystals, m.p. 132-134° C. Analysis of this material, particularly two CN bands in the IR spectrum at 2190 cm−1 and 2250 cm−1, revealed it to be a mixture of the cis- and trans-isomers of 1-cyanoacetone-2,4,6-trichlorophenylhydrazone. This material was suspended in methanol and treated with 10.0 mmol of sodium methoxide in 5 mL of methanol. After 5 minutes at room temperature, water was added to crystallize the product which was filtered off and washed well with water. After air drying, the product weighed 2.21 g (40%) and melted at 134.0-135.5° C. Despite the similarity in melting points, the latter material was distinctly different from the former, having an Rf of 0.67 vs. 0.78 for the intermediate on silica gel TLC plates developed with 1:1 hexane ethyl acetate and a distinctly different 300 MHz proton NMR spectrum.

Provenance & Evidence