Abstract
Four 1-aryl-1H-pyrazole-3,4-di-carboxyl-ate derivatives, one acid, two esters and a dicarbohydrazide have been synthesized starting from 3-aryl sydnones, and structurally characterized. There is an intra-molecular O-H⋯O hydrogen bond in 1-phenyl-1H-pyrazole-3,4-di-carb-oxy-lic acid, C11H8N2O4, (I), and the mol-ecules 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-di-carboxyl-ate, C13H12N2O4, (II), and dimethyl 1-(4-methyl-phen-yl)-1H-pyrazole-3,4-di-carboxyl-ate, C14H14N2O4, (III), C-H⋯O hydrogen bonds lead to the formation of cyclic centrosymmetric dimers: in (III), one of the meth-oxy-carbonyl groups is disordered over two sets of atomic sites having occupancies 0.71 (2) and 0.29 (2). An intra-molecular N-H⋯O hydrogen bond is present in the structure of 1-(4-meth-oxy-phen-yl)-1H-pyrazole-3,4-dicarbohydrazide, C12H14N6O3, (IV), and the mol-ecules 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.
Highlights
Pyrazole derivatives have been shown to exhibit a wide range of biological activities including analgesic (Girisha et al, 2010), anticonvulsant (Owen et al, 1958), antimicrobial (Satheesha & Kalluraya, 2007; Asma et al, 2018), antitumour (Park et al, 2005), and insecticidal and larvicidal activity (Yang et al, 2018)
In compounds (I) and (III), where such intramolecular interactions are not possible, the carboxyl groups at C3 are by no means coplanar with the pyrazole ring (Table 1), and in compound (III) the 3-methoxycarbonyl substituent is disordered over two sets of atomic sites having occupancies 0.71 (2) and 0.29 (2) in the crystal selected for
In each of (I) and (II), the planes of the aryl and pyrazole rings make much larger dihedral angles than these planes do in (II) and (IV) (Table 1). This may be associated with the cooperative effect in (III) and (IV) of the C—HÁ Á ÁO hydrogen bonds involving atoms C5 and C12 as donors (Table 2), whereas no such cooperation is found in the structures of (I) and (II)
Summary
Pyrazole derivatives have been shown to exhibit a wide range of biological activities including analgesic (Girisha et al, 2010), anticonvulsant (Owen et al, 1958), antimicrobial (Satheesha & Kalluraya, 2007; Asma et al, 2018), antitumour (Park et al, 2005), and insecticidal and larvicidal activity (Yang et al, 2018). Pyrazole carboxylic acids and their derivatives are versatile precursors for the synthesis of numerous substituted analogues (Asma et al, 2018; Devi et al, 2018) and, with these considerations in mind, we have synthesized a series of new pyrazole carboxylate derivatives as intermediates for the synthesis of new pharmacologically active products. We report the syntheses, and the molecular and supramolecular structures of four such compounds, namely 1-phenyl-1Hpyrazole-3,4-dicarboxylic acid (I), dimethyl 1-phenyl-1Hpyrazole-3,4-dicarboxylate (II), dimethyl 1-(4-methylphenyl)1H-pyrazole-3,4-dicarboxylate (III) and 1-(4-methoxyphenyl)-1H-pyrazole-3,4-dicarbohydrazide (IV) The products (II) and (III) and the intermediate ester (B) (Fig. 5) used in the formation of compound (IV) were all prepared using the 1,3-dipolar addition reaction between dimethyl acetylenedicarboxylate and the 3-arylsyndones [3-aryl-1,2,3-oxadiazol-3-ium-5-olates] (A), with loss of carbon dioxide in entropy-driven reactions (Huisgen et al, 1962) (Fig. 5). The sydnone precursors (A) were all prepared from the corresponding anilines via the substituted N-aryl-Nnitrosoglycines (Greco et al, 1962; Fun et al, 2010)
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