Chin Wei Ooi

Structural Correlation of Some Heterocyclic Chalcone Analogues and Evaluation of Their Antioxidant Potential

A series of six novel heterocyclic chalcone analogues 4(a–f) has been synthesized by condensing 2-acetyl-5-chlorothiophene with benzaldehyde derivatives in methanol at room temperature using a catalytic amount of sodium hydroxide. The newly synthesized compounds are characterized by IR, mass spectra, elemental analysis and melting point. Subsequently; the structures of these compounds were determined using single crystal X-ray diffraction. All the synthesized compounds were screened for their antioxidant potential by employing various in vitro models such as DPPH free radical scavenging assay, ABTS radical scavenging assay, ferric reducing antioxidant power and cupric ion reducing antioxidant capacity. Results reflect the structural impact on the antioxidant ability of the compounds. The IC50 values illustrate the mild to good antioxidant activities of the reported compounds. Among them, 4f with a p-methoxy substituent was found to be more potent as antioxidant agent.

Heteroaryl Chalcones: Design, Synthesis, X-ray Crystal Structures and Biological Evaluation

Chalcone derivatives have attracted increasing attention due to their numerous pharmacological activities. Changes in their structures have displayed high degree of diversity that has proven to result in a broad spectrum of biological activities. The present study highlights the synthesis of some halogen substituted chalcones 3(a–i) containing the 5-chlorothiophene moiety, their X-ray crystal structures and the evaluation of possible biological activities such as antibacterial, antifungal and reducing power abilities. The results indicate the tested compounds show a varied range of inhibition values against all the tested microbial strains. Compound 3c with a p-fluoro substituent on the phenyl ring exhibits elevated antimicrobial activity, whereas the compounds 3e and 3f displayed the least antimicrobial activities. The compounds 3d, 3e, 3f and 3i showed good ferric and cupric reducing abilities, and the compounds 3b and 3c showed the weakest reducing power in the series.

FT-IR, molecular structure, first order hyperpolarizability, HOMO and LUMO analysis, MEP and NBO analysis of 2-(4-chlorophenyl)-2-oxoethyl 3-nitrobenzoate

2-(4-Chlorophenyl)-2-oxoethyl 3-nitrobenzoate is synthesized by reacting 4-chlorophenacyl bromide with 3-nitrobenzoic acid using a slight excess of potassium or sodium carbonate in DMF medium at room temperature. The structure of the compound was confirmed by IR and single-crystal X-ray diffraction studies. FT-IR spectrum of 2-(4-chlorophenyl)-2-oxoethyl 3-nitrobenzoate was recorded and analyzed. The crystal structure is also described. The vibrational wavenumbers were computed using HF and DFT methods and are assigned with the help of potential energy distribution method. The first hyperpolarizability and infrared intensities are also reported. The geometrical parameters of the title compound obtained from XRD studies are in agreement with the calculated (DFT) values. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. MEP was performed by the DFT method.

Molecular structure, FT-IR, first order hyperpolarizability, NBO analysis, HOMO and LUMO analysis of 2-(4-chlorophenyl)-2-oxoethyl 3-methylbenzoate by HF and density functional methods.

2-(4-Chlorophenyl)-2-oxoethyl 3-methylbenzoate is synthesized by reacting 4-chlorophenacyl bromide with 2-methylbenzoic acid using a slight excess of potassium or sodium carbonate in DMF medium at room temperature. The structure of the compound was confirmed by IR and single-crystal X-ray diffraction studies. FT-IR spectrum of 2-(4-chlorophenyl)-2-oxoethyl-3-nitrobenzoate was recorded and analyzed. The crystal structure is also described. The vibrational wavenumbers were computed using HF and DFT methods and are assigned with the help of potential energy distribution method. The first hyperpolarizability and infrared intensities are also reported. The geometrical parameters of the title compound obtained from XRD studies are in agreement with the calculated (DFT) values. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The HOMO and LUMO analysis are used to determine the charge transfer within the molecule. MEP was performed by the DFT method.

Synthesis, molecular structure, FT-IR and XRD investigations of 2-(4-chlorophenyl)-2-oxoethyl 2-chlorobenzoate: a comparative DFT study

2-(4-Chlorophenyl)-2-oxoethyl 2-chlorobenzoate has been synthesized, its structural and vibrational properties have been reported using FT-IR and single-crystal X-ray diffraction (XRD) studies. The conformational analysis, optimized geometric parameters, normal mode frequencies and corresponding vibrational assignments of the synthesized compound (C15H10Cl2O3) have been examined by means of Becke-3-Lee-Yang-Parr (B3LYP) density functional theory (DFT) method together with 6-31++G(d,p) basis set. Furthermore, reliable conformational investigation and vibrational assignments have been made by the potential energy surface (PES) and potential energy distribution (PED) analyses, respectively. Calculations are performed with two possible conformations. The title compound crystallizes in orthorhombic space group Pbca with the unit cell dimensions a=12.312(5) Å, b=8.103(3) Å, c=27.565(11) Å, V=2750.0(19) Å(3). B3LYP method provides satisfactory evidence for the prediction of vibrational wavenumbers and structural parameters.

Conformational studies of 2-(4-bromophenyl)-2-oxoethyl benzoates

Abstract Phenacyl benzoates possess commercial importance due to their various applications in the fields of synthetic and photochemistry, such as photosensitive blocking groups owing to their ease of cleavage under mild conditions. In the present study, a series of ten new 2-(4-bromophenyl)-2-oxoethyl benzoates 2(a–j), with the general formula Br(C6H4)COCH2OCO(C6H5–nXn), X = Cl, NO2 or NH2, and n = 1 or 2, have been synthesized by reacting 4-bromophenacyl bromide with various substituted benzoic acids using potassium carbonate in DMF medium at room temperature. These reactions proceeded with ease under mild conditions producing high purity products in good yield. Each product was characterized by mass spectra, elemental analysis and melting points, its 3D structure was confirmed by single-crystal X-ray diffraction studies. The X-ray 3D structures showed the flexibility of the C(=O)–O–C–C(=O) connecting bridge in which 7 out of 10 compounds tend to form a torsion angle in the range of 70 to 91°, whereas the rest are slightly twisted with a torsion angles of –160, 163, 176 and 178°. Their molecular conformations are in good agreement with another 22 related structures. These synthesized compounds were screened for their abilities for DPPH radical scavenging and ferric reducing anti-oxidant power. The results indicate that these compounds displayed mild anti-oxidant ability when compared to the standard anti-oxidant BHT.

2,2-Diphenyl-N-(1,3-thia­zol-2-yl)acetamide

In the title molecule, C17H14N2OS, the mean plane of the acetamide group forms dihedral angles of 75.79 (5), 81.85 (6) and 12.32 (5)° with the two phenyl rings and the thiazole ring, respectively. In the crystal, N—H⋯N hydrogen bonds link pairs of molecules into inversion dimers with R 2 2(8) ring motifs. The crystal packing is further stabilized by C—H⋯π interactions and by π–π interactions with a centroid–centroid distance of 3.6977 (5) Å.

2-[(E)-4-Diethyl-amino-2-hy-droxy-benzyl-idene]hydrazinecarboxamide.

Two molecules make up the asymmetric unit of the title compound, C12H18N4O2, and both feature an intramolecular O—H⋯N hydrogen bond, which generates an S(6) ring. The diethylamino group of one of the molecules is disordered over two sets of sites in a 0.59 (2):0.41 (2) ratio. In the crystal, N—H⋯O hydrogen bonds link the molecules into sheets lying parallel to the ac plane and C—H⋯π interactions are also observed.

[2,6-Bis(biphenyl-4-yl)-4-hy­droxy-4-(pyridin-2-yl)cyclo­hexane-1,3-di­yl]bis­[(pyridin-2-yl)methanone]–butan-2-one (1/1)

In the title solvate, C47H37N3O3·C4H8O, the cyclohexane ring adopts a chair conformation and the plane through its near coplanar atoms forms dihedral angles of 82.58 (7), 89.27 (7), 60.30 (8), 54.54 (7) and 72.03 (7)°, respectively, with the three pyridine rings and the two attached benzene rings. The rings of the biphenyl units are twisted from each other, making dihedral angles of 35.27 (7) and 45.41 (7)°. All the rings are in equatorial orientations in the cyclohexane ring, except for the C=O-bonded pyridine ring in position 1, which is axial. Intramolecular O—H⋯N and C—H⋯O hydrogen bonds form one S(5) and three S(6) ring motifs. In the crystal, molecules are linked via C—H⋯O hydrogen bonds into a chain along the c axis. The crystal structure also features weak C—H⋯π interactions and aromatic π–π stacking [centroid–centroid distances = 3.5856 (10) and 3.7090 (9) Å].

N-(3,4-Difluoro­phen­yl)-2,2-diphenyl­acetamide

In the title compound, C20H15F2NO, the mean plane of the acetamide group makes dihedral angles of 88.26 (6), 78.30 (7) and 9.83 (6)° with the two terminal benzene rings and difluoro-substituted benzene ring, respectively. One F atom is disordered over two orientations rotated by 180°, with a site-occupancy ratio of 0.557 (2):0.443 (2). An intramolecular C—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked via N—H⋯O hydrogen bonds into chains along the c axis. The crystal structure is further consolidated by C—H⋯π interactions.