Triethylamine → Ethyl 1-(2,4-dichlorophenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate

Participants

Reaction Conditions

Reaction Steps

2,4-Dichlorophenylhydrazine hydrochloride salt (15.68 grams, 0.068 mole) was dissolved in a minimum amount of ethanol and the solution was cooled to -10° C. Triethylamine (9.44 ml, 0.068 mole) was added followed by ethyl(ethoxymethylene)trifluoroacetoacetate (16.27 grams, 0.068 mole). The addition of this last reactant was made over thirty minutes, keeping the reaction temperature below -10° C. The reaction mixture was allowed to rise to room temperature overnight (about 16 hours). The solvent was removed in vacuo and the residue was dissolved in equal parts of ethyl acetate and water. The organic phase was separated, washed with 1N HCl, water, saturated sodium bicarbonate solution, water, and brine. It was then dried and evaporated to 7.85 grams of an oil which slowly crystallized. The 5-(trifluoromethyl)-1-(2,4-dichlorophenyl)-1H-pyrazole-4-carboxylic acid, ethyl ester, was recrystallized from petroleum ether, mp=81°-83° C.

Provenance & Evidence