Synthesis of Chromone-Related Pyrazole Compounds

Chromones, six-membered oxygen heterocycles, and pyrazoles, five-membered two-adjacent-nitrogen-containing heterocycles, represent two important classes of biologically active compounds. Certain derivatives of these scaffolds play an important role in medicinal chemistry and have been extensively used as versatile building blocks in organic synthesis. In this context, we will discuss the most relevant advances on the chemistry that involves both chromone and pyrazole rings. The methods reviewed include the synthesis of chromone-pyrazole dyads, synthesis of chromone-pyrazole-fused compounds, and chromones as starting materials in the synthesis of 3(5)-(2-hydroxyaryl)pyrazoles, among others. This review will cover the literature on the chromone and pyrazole dual chemistry and their outcomes in the 21st century.

New synthesis on the basis 2-allyloxy chalcone and NMR studies its some derivatives

Synthesis and NMR investigations of cyclohexenone, flavanone, isoxazol and indazole derivatives of (2E)-3-[2-(allyloxy)-5-bromophenyl]-1-(2-hydroxy-5-methylphenyl)-2-propen-1-one (I, chalcone) have been carried out. The results confirm the formation of O-H•••O type intramolecular hydrogen bond and intramolecular cyclization in the (2E)-3-[2-(allyloxy)-5-bromophenyl]-1-(2-hydroxy-5-methylphenyl)-2-propen-1-one (I), the presence of conformational and keto-enol tautomeric transitions in the 6-acetyl-5-[2-(allyloxy)-5-bromophenyl]-3-(2-hydroxy-5-methylphenyl)-2-cyclohexen-1-one (II), conformational transitions in the 2-{4-[2-(allyloxy)-5-bromophenyl]-3-methyl-4.5-dihydro-1.2-benzisoxazol-6-yl}-4-methylphenol (III) and 2-{4-[2-(allyloxy)-5-bromophenyl]-3-methyl-4.5-dihydro-1H-indazol-6-yl}-4-methylphenol (IV). The conformational and keto-enol tautomerism in the investigated compounds have been also confirmed by chemical methods.

Crystal structure of ethyl 2-({[(4Z)-3,5-dioxo-1-phenyl-pyrazolidin-4-yl-idene]meth-yl}amino)-acetate

The title compound, C14H15N3O4, is nearly planar, the dihedral angle between the planes of the phenyl and pyrazolidine rings being 1.13 (7) Å, and that between the plane of the pyrazolidine ring and the mean plane of the side chain [C-N-C-C(=O)-O; r.m.s. deviation = 0.024 Å] being 2.52 (7)°. This is due in large part to the presence of the intra-molecular N-H⋯O and C-H⋯O hydrogen bonds. In the crystal, pairwise N-H⋯O hydrogen bonds form inversion dimers, which are further associated into layers, lying very close to plane (-120), via pairwise C-H⋯O hydrogen bonds. The layers are then weakly connected through C-H⋯O hydrogen bonds, forming a three-dimensional structure.

Molecular dynamics of (E)-6-acetyl-3-(2-hydroxy-5-methylphenyl)-5-styryl cyclohex-2-en-1-one and (E)-6-ethylcarboxylate-3-(2-hydroxy-5-methylphenyl)-5-styryl cyclohex-2-en-1-one in a solution studied by NMR spectroscopy

Molecular dynamics of cyclohexenone derivatives of (2E,4E)-1-(2-hydroxy-5-methylphenyl)-5-phenyl-2,4-pentadiene-1-one (chalcone) has been investigated in solutions using NMR. The results confirm the formation of O-H···O intramolecular hydrogen bond and the presence of keto-enol tautomeric transitions in the (E)-6-acetyl-3-(2-hydroxy-5-methylphenyl)-5-styryl cyclohex-2-en-1-one. The free energy of activation for the keto-enol tautomeric transitions has been calculated. The keto-enol tautomerism in the investigated compound has been also confirmed by chemical method.

(4E)-4-[(2-Hy-droxy-anilino)methyl-idene]-1-phenyl-pyrazolidine-3,5-dione dimethyl sulfoxide hemisolvate

The asymmetric unit of the title compound, C16H13N3O3·0.5C2H6OS, is composed of two independent pyrazolidine-3,5-dione mol-ecules and one dimethyl sulfoxide solvent mol-ecule. In each pyrazolidine-3,5-dione mol-ecule, an intra-molecular N-H⋯O hydrogen bond forms an S(5)S(6) motif. In the crystal, pairs of each independent pyrazolidine-3,5-dione mol-ecule are linked by N-H⋯O hydrogen bonds, forming dimers with R 2 (2)(8) motifs. These dimers are connected with the other mol-ecules through the solvent mol-ecules via O-H⋯O hydrogen bonds, forming ribbons along the b-axis direction. C-H⋯π inter-actions connect the ribbons. C-H⋯O interactions also occur.

Molecular dynamics of 6-methyl-2-phenyl-2,3-dihydro-4H-chromen-4-one and 6-methyl-2-(4-nitrophenyl)-2,3-dihydro-4H-chromen-4-one (flavanone) derivatives in a solution studied by NMR spectroscopy

Molecular dynamics of benzoxazepin, oxime, pyrazole, and thiosemicarbazone derivatives of some flavanones have been investigated in a solution using NMR. The results confirm the formation of different O-H···O, O-H···N, N···H-N type intramolecular hydrogen bonds in the pyrazole and oxime molecules. The rotational barrier energy and energy of intramolecular hydrogen bonds have been determined.

Infrared and Raman spectroscopic analyses and theoretical computation of 4-butyl-1-(4-hydroxyphenyl)-2-phenyl-3,5-pyrazolidinedione

Infrared and Raman spectroscopic analyses were carried out on 4-butyl-1-(4-hydroxyphenyl)-2-phenyl-3,5-pyrazolidinedione. The interpretation of the spectra was aided by DFT calculation of the molecule. The vibrational wavenumbers were examined theoretically using the Gaussian03 set of quantum chemistry codes and the normal modes were assigned by potential energy distribution calculations. A computation of the first hyperpolarizability of the compound indicates that the compound may be a good candidate as a NLO material. Optimized geometrical parameters are in agreement with the reported XRD results. The RMS error of the observed Raman bands and IR bands are found to be 35.09 and 39.57 for HF method and 14.31 and 17.17 for DFT method. The predicted infrared intensities and Raman activities are reported.