Four 1-aryl-1H-pyrazole-3,4-dicarboxylate derivatives: synthesis, molecular conformation and hydrogen bonding

Abstract

Four 1-aryl-1H-pyrazole-3,4-dicarboxylate derivatives, one acid, two esters and a dicarbohydrazide have been synthesized starting from 3-aryl sydnones, and structurally characterized. There is an intramolecular O—H...O hydrogen bond in 1-phenyl-1H-pyrazole-3,4-dicarboxylic acid, C11H8N2O4, (I), and the molecules are linked into a three-dimensional framework structure by a combination of O—H...O, O—H...N, C—H...O and C—H...π(arene) hydrogen bonds. In each of the two esters dimethyl 1-phenyl-1H-pyrazole-3,4-dicarboxylate, C13H12N2O4, (II), and dimethyl 1-(4-methylphenyl)-1H-pyrazole-3,4-dicarboxylate, C14H14N2O4, (III), C—H...O hydrogen bonds lead to the formation of cyclic centrosymmetric dimers: in (III), one of the methoxycarbonyl groups is disordered over two sets of atomic sites having occupancies 0.71 (2) and 0.29 (2). An intramolecular N—H...O hydrogen bond is present in the structure of 1-(4-methoxyphenyl)-1H-pyrazole-3,4-dicarbohydrazide, C12H14N6O3, (IV), and the molecules are linked into a three-dimensional framework structure by a combination of N—H...O, N—H...N, N—H...π(arene) and C—H...O hydrogen bonds. Comparisons are made with the structures of a number of related compounds.