The reaction of 5-(4-methoxyphenyl)furan-2,3-dione with urea in a 1:1 ratio when refluxed in a mixture of 1,2-dichloroethane-DMSO gives (Z)-N-carbamoyl-4-hydroxy-4-(4-methoxyphenyl)-2-oxobut-3-enamide in a good yield. This compound was fully characterized.

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-1H-pyrazole-5-carboxylic acids and 3-aryl-1-(4-nitrobenzoyl)-5-[2-(4-nitrobenzoyl)hydrazinyl]-4,5-dihydro-1H-pyrazole-5-carboxylic acids. The structure of the products was confirmed by X-ray diffraction analysis. The reaction proceeds under mild, catalyst-free conditions to give high yields, and the products were isolated without column chromatography. The synthesized compounds exhibit potential for diverse biological activities.

The reaction of 3-aroylpyrrolo[1,2-c][4,1]benzoxazepine-1,2,4-triones with urea and thiourea leads to the formation of 9-aroyl-8-hydroxy-6-[2-(hydroxymethyl)phenyl]-1,3,6-triazaspiro[4.4]-non-8-ene-2,4,7-triones and 9-aroyl-8-hydroxy-6-[2-(hydroxymethyl)phenyl]-2-thioxo-1,3,6-triazaspiro[4.4]non-8-ene-4,7-diones, respectively. The described reaction is a convenient method for the synthesis of the hardly accessible 1,3,6-triazaspiro[4.4]nonenone system (hydantoins spiro-annulated to the pyrrole ring).

The reaction of 4-(4-bromophenyl)-2,4-dioxobutanoic acid with thiosemicarbazide, in a ratio of 1:2, when boiled in ethanol gives 3-(4-bromophenyl)-1-carbamothioyl-5-(2-carbamothioylhydrazinyl)-4,5-dihydro-1H-pyrazole-5-carboxylic acid with a good yield. This compound was fully characterized.

Compounds based on the pyrazoloquinazoline scaffold are of significant interest in synthetic organic chemistry owing to their potential biological activity. In this work, we describe the synthesis of a new derivative with this scaffold, 9-oxo-2-(p-tolyl)-4,9-dihydropyrazolo[5,1-b]quinazoline-3a(3H)-carboxylic acid, obtained by reacting 2,4-dioxo-4-(p-tolyl)butanoic acid with 2-aminobenzohydrazide in a 1:1 ratio when mixed in ethanol. The compound was characterized by ¹H/¹³C NMR, IR, and X-ray diffraction analysis.

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.