(E)-2-Benzylidenebenzocyclanones: part XIII—(E)/(Z)-Isomerization of some cyclic chalcone analogues. Effect of ring size on lipophilicity of geometric isomers

Reaction of Chalcones with Cellular Thiols. The Effect of the 4-Substitution of Chalcones and Protonation State of the Thiols on the Addition Process. Diastereoselective Thiol Addition

Several biological effects of chalcones have been reported to be associated with their thiol reactivity. In vivo, the reactions can result in the formation of small-molecule or protein thiol adducts. Both types of reactions can play a role in the biological effects of this class of compounds. Progress of the reaction of 4-methyl- and 4-methoxychalcone with glutathione and N-acetylcysteine was studied by the HPLC-UV-VIS method. The reactions were conducted under three different pH conditions. HPLC-MS measurements confirmed the structure of the formed adducts. The chalcones reacted with both thiols under all incubation conditions. The initial rate and composition of the equilibrium mixtures depended on the ratio of the deprotonated form of the thiols. In the reaction of 4-methoxychalcone with N-acetylcysteine under strongly basic conditions, transformation of the kinetic adduct into the thermodynamically more stable one was observed. Addition of S-protonated N-acetylcysteine onto the polar double bonds of the chalcones showed different degrees of diastereoselectivity. Both chalcones showed a Michael-type addition reaction with the ionized and non-ionized forms of the investigated thiols. The initial reactivity of the chalcones and the equilibrium composition of the incubates showed a positive correlation with the degree of ionization of the thiols. Conversions showed systematic differences under each set of conditions. The observed differences can hint at the difference in reported biological actions of 4-methyl- and 4-methoxy-substituted chalcones.

Insights on a new sulfonamide chalcone with potential antineoplastic application

Chalcones (E)-1,3-diphenyl-2-propene-1-ones, a class of biosynthetic precursor molecules of flavonoids, have a wide variety of biological applications. Besides the natural products, many synthetic derivatives and analogs became an object of continued interest in academia and industry. In this work, a synthesis and an extensive structural study were performed on a sulfonamide chalcone 1-Benzenesulfonyl-3-(4-bromobenzylidene)-2-(2-chlorophenyl)-2,3-dihydro-1H-quinolin-4-one with potential antineoplastic application. In addition, in silico experiments have shown that the sulfonamide chalcone fits well in the ligand-binding site of EGFR with seven μ-alkyl binding energy interactions on the ligand-binding site. Finally, the kinetic stability and the pharmacophoric analysis for EGFR indicated the necessary spatial characteristics for potential activity of sulfonamide chalcone as an antagonist.

2H-Indazole Tautomers Stabilized by Intra- and Intermolecular Hydrogen Bonds

2-[(2H-Indazol-3-yl)methylene]-1H-indene-1,3(2H)-dione 6 and (E)-2-[(2H-indazol-3-yl)methylene]-2,3-dihydro-1H-inden-1-one 7 have been synthesized. In the crystal, the NH hydrogen atom of 6 is disordered between the N(1) and N(2) atoms with the population ratio of 0.69:0.31. Molecule 7 crystallizes in two tautomeric polymorphs: 7-1H tautomer (yellow) and 7-2H tautomer (red). Both 6 and 7 form centrosymmetric dimers in the crystal with the monomeric units linked by C═O···H···N bifurcated hydrogen bonds in 6 and N-H···N hydrogen bonds in 7. According to ¹H and ¹³C NMR data, in DMSO-d₆ solution, the 6-1H tautomer predominates, whereas in less polar CDCl₃ or CD₂Cl₂, the 6-2H tautomer is stabilized by a strong N-H···O═C intramolecular hydrogen bond. Compound 7 in dimethyl sulfoxide (DMSO) or ethanol solutions exists in the form of 7-1H and 7-2H tautomers. On the example of the 7-2H tautomer, it was shown for the first time that the 2H tautomers of 3-substituted indazoles can be stabilized by an intermolecular hydrogen bond and may remain in aprotic solvents almost indefinitely. However, in the open air or in water, fast 2H → 1H tautomerization occurs. As follows from density functional theory calculations, the high stability of the 2H form in solution is due to the formation of centrosymmetric dimers, which are more stable than the corresponding dimers of the 1H tautomer.

Structural studies of (E)-2-(benzylidene)-1-tetralone derivatives: crystal structures and Hirshfeld surface analysis

Crystal structures are reported from data collected at 100 K of (E)-2-(X-benzylidene)-1-tetralone (2: X=3-O2N; 3: X=4-O2N; 5: X=4-HO; 6: X=4-Me2N; 7: 4-NC), (E)-2-(X-benzylidene)-6-MeO-1-tetralone, 8, and (E)-2-(X-benzylidene)-5-MeO-1-tetralone 9. Also reported herein are the Hirshfeld surface calculations for these compounds as well as those of (E)-2-(X-benzylidene)-1-tetralone (1: X=H; 4: X=4-MeO), whose structures were previously reported. The molecules are not planar as shown by the dihedral angles of 45.66(5)–69.78(5)° between the phenyl groups and by the puckered cyclohexenyl rings. A common feature of the molecular conformations is the C–H···O1(carbonyl) intramolecular hydrogen bond. The carbonyl oxygen atom plays significant roles in the interactions in all compounds baring compound 8. However, there is no consistent set of intermolecular interaction in this group of compounds. Intermolecular interactions present in each compound are some of the O–H···O, C–H···A (A=O, N or π), A–O···π (A=C or N) and π···π interactions. The only compound exhibiting a classical O–H···O hydrogen bond is compound 5. C–H···π interactions are found in all compounds, and while π···π interactions are present in compounds 2, 3, 7 and 9, no consistent type of stacking arrangement is shown. The Hirshfeld surface calculations, while generally concurring with the intermolecular interactions indicated by PLATON analyses, also reveal short interactions, which fall below the PLATON cut-off parameters.

Structural studies of (E)-2-(benzylidene)- 2,3-dihydro-1H-inden-1-one derivatives: crystal structures and Hirshfeld surface analysis

Crystal structures are reported of (E)-2-(4-hydroxybenzylidene)-2,3-dihydro-1H-inden-1-one, 1, (E)-2-(4-dimethylaminobenzylidene)-2,3- dihydro-1H-inden-1-one, 2, (E)-2-(4-cyanobenzylidene)-2,3-dihydro-1H-inden-1-one, 3, and monoclinic-(E)- 2-(3-nitrobenzylidene)-2,3-dihydro-1H-inden-1-one, monoclinic-4, all from data collected at 100 K and (E)-2-(4-hydroxy-3,5-dimethylbenzylidene)-2,3-dihydro-1H-indan-1-one, 6, from data collected at 299 K. An earlier triclinic form of 4 has been reported. Also reported herein are the Hirshfeld suface calculations for these five compounds, as well as that of 2-(4-methoxybenzylidene)-2,3-dihydro-1H-inden-1-one, 5,whose crystal structure has been previously reported. The three rings in each of the compounds, 1–4 and 6, are essentially planar, including the five-membered ring containing a formally hydridized sp3 atom. The molecules exhibit slight deviations from overall planarity as shown by the dihedral angles, >8.15(6)° between the 2,3-dihydro-1H-inden-1-one fragments and the phenyl fragments. The main intermolecular interactions in compounds 1 and are classical O–H···O1(carbonyl) hydrogen bonds. The carbonyl oxygen atom in compounds 1–4 are involved in non-classical C–H···O intermolecular hydrogen bonds. Intermolecular C–H---π interactions are present in 2, 3 and 6, while π···π are present in 2–4 and 6. As noted in the structure determinations of these compounds, different π···π motifs are possible. The Hirshfeld surface calculations, while generally concurring with the intermolecular interactions indicated by PLATON analyses, also reveal significant interactions, which fall below the PLATON radar.

Arylidene indanone scaffold: medicinal chemistry and structure–activity relationship view

Arylidene indanone (AI) scaffolds are considered as the rigid cousins of chalcones, incorporating the α,β-unsaturated ketone system of chalcones forming a cyclic 5 membered ring.

Molecular Structure and Photoinduced Intramolecular Hydrogen Bonding in 2-Pyrrolylmethylidene Cycloalkanones

The structures of pyrrolylmethylidene derivatives of 2,3-dihydro-1H-inden-1-one (3), 3,4-dihydro-naphthalen-1(2H)-one (4), and cycloalkanones (5-7) were studied for the first time in the solid state and solution by NMR, IR, and UV spectroscopies supported by DFT quantum mechanical calculations. It was shown that all studied compounds except cycloheptanone derivative 7 both in crystal and in solution exist in the form of dimers where single E or E,E configuration with respect to the exocyclic C═C bond is stabilized by intermolecular hydrogen bonds N-H···O═C. UV irradiation at a wavelength of 365 nm of MeCN or DMSO solutions of 3-6 results, depending on the exposition time and solvent, partial to complete isomerization to the Z or Z,E isomers (in the case of 6, also the Z,Z isomer). The NMR and IR spectroscopy data show the existence of a strong intramolecular hydrogen bond N-H···O═C in the Z moieties of isomerized compounds. The studied compounds are protonated by trifluoroacetic acid at the carbonyl oxygen, in spite of the reverse order of basicity and nucleophilicity of the carbonyl group and the pyrrole ring. Investigation of the behavior of compound 6 with respect to acetate and fluoride anions allows one to consider it as a potential fluoride sensor.