The Interaction of Aroylpyruvic Acids with 3- and 4-Nitrobenzohydrazides. Synthesis of Pyrazoline-5-Carboxylic Acids

4-Aryl-2,4-dioxobutanoic acids react with 3-nitro- and 4-nitrobenzohydrazides in a 1:2 ratio to form the corresponding 3-aryl-1-(3-nitrobenzoyl)-5-(2-(3-nitrobenzoyl)hydrazinyl)-4,5-dihydro-1-pyrazole-5-carboxylic acids and 3-aryl-1-(4-nitrobenzoyl)-5-(2-(4-nitrobenzoyl)hydrazinyl)-4,5-dihydro-1-pyrazole-5-carboxylic acids, the structure of which is confirmed by X-ray diffraction analysis. The reaction proceeds under mild conditions with high yields without the use of catalysts and additives, and the isolation process does not require column chromatography. The obtained compounds are promising in terms of the manifestation of various types of biological activity.