Five-membered 2,3-dioxo heterocycles: LXXXII. Recyclization of dimethyl 4,5-Dioxo-4,5-dihydro-1H-pyrrole-2,3-dicarboxylates in reaction with monosubstituted hydrazines. crystalline and molecular structure of dimethyl 1-benzyl-5-(4-methylphenylcarbamoyl)-1H-pyrazole-3,4-dicarboxylate

Dimethyl 1-aryl(benzyl)-4,5-dioxo-4,5-dihydro-1H-pyrrole-2,3-dicarboxylates reacted with phenylhydrazine and benzylhydrazine to give dimethyl 1-aryl(benzyl)-5-[(aryl or benzyl)carbamoyl]-1H-pyrazole-3,4-dicarboxylates.