Benzimidazolium Salts Containing Trifluoromethoxybenzyl: Synthesis, Characterization, Crystal Structure, Molecular Docking Studies and Enzymes Inhibitory Properties.

The method for producing 4-trifluoromethoxybenzyl substituted benzimidazolium salts is described in this article. The method is based on the reaction of 4-trifluoromethoxybenzyl substituent alkylating agent with 1-alkylbenzimidazole. This method yielded 1-(4-trifluoromethoxybenzyl)-3-alkylbenzimidazolium bromide salts. These benzimidazolium salts were characterized by using 1 H-NMR, 13 C-NMR, FT-IR spectroscopy, and elemental analysis techniques. The crystal structure of 1f was enlightened by single crystal X-ray diffraction studies. Also, the enzyme inhibition effects of the synthesised compounds were investigated. They demonstrated highly potent inhibition effect on acetylcholinesterase (AChE) and carbonic anhydrases (hCAs) (Ki values are in the range of 7.24±0.99 to 39.12±5.66 nM, 5.57±0.96 to 43.07±11.76 nM, and 4.38±0.43 to 18.68±3.60 nM for AChE, hCA I, and hCA II, respectively). In molecular docking study, the interactions of active compounds showing activity against AChE and hCAs enzymes were examined. The most active compound 1f has -10.90 kcal/mol binding energy value against AChE enzyme, and the potential structure compound 1e, which has activity against hCA I and hCA II enzymes, was -7.51 and -8.93 kcal/mol, respectively.

Benzimidazolium salts bearing the trifluoromethyl group as organofluorine compounds: Synthesis, characterization, crystal structure, in silico study, and inhibitory profiles against acetylcholinesterase and α-glycosidase.

Here, we report the synthesis, characterization, and biological activities of a series of benzimidazolium salts bearing the trifluoromethylbenzyl group. All benzimidazolium salts were characterized by using nuclear magnetic resonance (NMR) (1 H NMR and 13 C NMR), Fourier transform-infrared spectroscopy, and elemental analysis techniques. The crystal structures of some of these compounds were obtained by the single-crystal X-ray diffraction method. Furthermore, the acetylcholinesterase (AChE) and α-glycosidase (α-Gly) enzyme inhibition activities of these compounds were investigated. The obtained results revealed that 2e, with Ki value of 1.36 ± 0.34 µM against AChE and 3d with Ki value of 91.37 ± 10.38 µM against α-Gly, were the most potent compounds against both assigned enzymes. It should be noted that most of the synthesized compounds were more potent than standard inhibitor tacrine (TAC) against AChE. In silico studies, we focused on compound 2e, 3d, 3e, and 3f as potent inhibitors of AChE and α-Gly, the compound 2e showed good binding energy (-10.23 kcal/mol), among the three selected compounds and positive control (-10.18, -10.08, and -7.37 kcal/mol for 3d, 3f, and TAC, respectively). Likewise, as a result of the same compounds against the α-Gly enzyme, the compound 3d had the highest binding affinity (-8.39 kcal/mol) between the four selected compounds and the positive control (-8.27, -8.10, -8.06, and -7.53 kcal/mol for 3f, 3e, 2e, and acarbose, respectively). From the absorption, distribution, metabolism, excretion, and toxicity analyses, it can be concluded that the compounds under consideration exhibited more drug-likeness properties in the prediction studies compared to positive controls.

Cytotoxic and apoptotic effects of 1,2-diborolanes with strong donor substitutes on human cancer cells.

In recent years, boron compounds have become more common as chemotherapy agents against certain types of cancers. Along with the development of boron-based therapeutic agents have come investigations into the various cancers and biochemical and molecular mechanisms affected by boron compounds and the relationships between boron compounds and chemical protection against cancer. In this preliminary study, the effects of new 1,2-N-substituted-1,2-diborolane derivatives on types of breast and liver cancers were examined for the first time. Four were found to significantly affect the cell viabilities and mitochondrial membrane potential changes in MCF-7, HepG2 and Hep3B cancer cells. Each was prepared in n-hexane at various concentrations (5, 10, 25, 50, 75 and 100 µg/mL). Human peripheral blood lymphocytes were used as control cells. Compounds 1, 2, 3a, and 3b 1,2-diborolane derivatives selectively killed cancer cells, but compound 1 was cytotoxic in a concentration-dependent manner on HepG2 and Hep3B and only at concentrations of at least 75 µg/mL on MCF-7 cells. Compound 3a exhibited cytotoxic effect on lymphocytes at 75 and 100 µgmL-1 concentrations, but compounds 1, 2 and 3b, 3c and 3d have not possessed significant cytotoxic effect on lymphocytes. Compounds 3c and 3d have not possessed significant cytotoxic effects. Mitochondrial membrane potential assay results supported these findings. Our results reveal that 1,2-diborolane derivates have high cytotoxic and apoptotic activities on human hepatocarcinoma cells and are therefore potential candidates in the development of new drugs against liver cancer.

1,2-Diborolanes with strong donor substituents: Synthesis and high antimicrobial activity.

1,2-diborolanes with strong and without strong donor substituents have been described, and are also referred to as 1,2-diboracyclopentane. The 1,2-diaryl/alkyl-amino-1,2-diboracyclopentanes 2, 3, and 4 were obtained in good yield after the reaction of 1,2-dichloro-1,2-diboracyclopentane 1 with ArNHLi and Me3Si-NR2. The structures of these new derivatives were characterized by nuclear magnetic resonance spectroscopy. The molecular structures of 2b, 2c, 2e, 4, and 5f were also determined by single-crystal X-ray diffraction. The newly synthesized 1,2-borolanes are stable in air and showed particularly high activity against some Gram-positive bacteria.

Neutral cyclic sp2-sp3 and sp3-sp3 diboranes from N,N'-dicyclohexylcarbodiimide insertion into 1,2-dichlorodiboranes(4).

We report the synthesis and structural characterization of new neutral cyclic sp2-sp3 and sp3-sp3 diboranes from the reaction of N,N'-dicyclohexylcarbodiimide with 1,2-dichlorodiboranes(4) at room temperature. The present study is the first example of an insertion reaction of carbodiimide into diborane(4).

Substituent position effect on the crystal structures of N-phenyl-2-phthalimidoethanesulfonamide derivatives.

In order to determine the impact of different substituents and their positions on intermolecular interactions and ultimately on the crystal packing, unsubstituted N-phenyl-2-phthalimidoethanesulfonamide, C16H14N2O4S, (I), and the N-(4-nitrophenyl)-, C16H13N3O6S, (II), N-(4-methoxyphenyl)-, C16H16N3O6S, (III), and N-(2-ethylphenyl)-, as the monohydrate, C18H18N2O4S·H2O, (IV), derivatives have been characterized by single-crystal X-ray crystallography. Sulfonamides (I) and (II) have triclinic crystal systems, while (III) and (IV) are monoclinic. Although the molecules differ from each other only with respect to small substituents and their positions, they crystallized in different space groups as a result of differing intra- and intermolecular hydrogen-bond interactions. The structures of (I), (II) and (III) are stabilized by intermolecular N-H...O and C-H...O hydrogen bonds, while that of (IV) is stabilized by intermolecular O-H...O and C-H...O hydrogen bonds. All four structures are of interest with respect to their biological activities and have been studied as part of a program to develop anticonvulsant drugs for the treatment of epilepsy.

Positional isomeric effect on the crystallization of chlorine-substituted N-phenyl-2-phthalimidoethanesulfonamide derivatives.

The ortho-, para- and meta-chloro-substituted N-chlorophenyl-2-phthalimidoethanesulfonamide derivatives, C16H13ClN2O4S, have been structurally characterized by single-crystal X-ray crystallography. N-(2-Chlorophenyl)-2-phthalimidoethanesulfonamide, (I), has orthorhombic (P2(1)2(1)2(1)) symmetry, N-(4-chlorophenyl)-2-phthalimidoethanesulfonamide, (II), has triclinic (P1¯) symmetry and N-(3-chlorophenyl)-2-phthalimidoethanesulfonamide, (III), has monoclinic (P2(1)/c) symmetry. The molecules of (I)-(III) are regioisomers which have crystallized in different space groups as a result of the differing intra- and intermolecular hydrogen-bond interactions which are present in each structure. Compounds (I) and (II) are stabilized by N-H···O and C-H···O hydrogen bonds, while (III) is stabilized by N-H···O, C-H···O and C-H···Cl hydrogen-bond interactions. The structure of (II) also displays π-π stacking interactions between the isoindole and benzene rings. All three structures are of interest with respect to their biological activities and have been studied as part of a programme to develop anticonvulsant drugs for the treatment of epilepsy.

π-Cooperativity effect on the base stacking interactions in DNA: is there a novel stabilization factor coupled with base pairing H-bonds?

The results from absolutely localized molecular orbital (ALMO)-energy decomposition analysis (EDA) and ALMO-charge transfer analysis (CTA) at M06-2X/cc-pVTZ level reveal that double-proton transfer (DPT) reactions through base pairing H-bonds have nonignorable effects on the stacking energies of dinucleotide steps, which introduces us to a novel stabilization (or destabilization) factor in the DNA duplex. Thus, intra- and inter-strand base stacking interactions are coalesced with each other mediated by H-bridged quasirings between base pairs. Changes in stacking energies of dinucleotide steps depending on the positions of H atoms are due to variations in local aromaticities of individual nucleobases, manifesting π-cooperativity effects. CT analyses show that dispersion forces in dinucleotide steps can lead to radical changes in the redox properties of nucleobases, in particular those of adenine and guanine stacked dimers in a strand. Besides Watson-Crick rules, novel base pairing rules were propounded by considering CT results. According to these, additional base pairing through π-stacks of nucleobases in dinucleotide steps does not cause any intrinsic oxidative damage to the associated nucleobases throughout DPT.

Changes in ligating abilities of the singlet and triplet states of normal, abnormal and remote N-heterocyclic carbenes depending on their aromaticities.

Quantum chemical calculations at B3LYP/aug-cc-pVTZ level about singlet N-heterocyclic carbene (NHC) ligands, imidazol-2-ylidene, imidazol-4-ylidene, pyrazol-3-ylidene and pyrazol-4-ylidene, and their protonated analogues show that they are considerably aromatic except for pyrazol-3-ylidene. This result is experimentally verified by approximately five thousand NHC transition metal complexes retrieved from the Cambridge Structural Database (CSD). CSD search discloses that NHCs can participate in π-stacking interactions, albeit scarce. Geometry-based HOMA and electronic aromaticity index FLU rather than NICS provide a satisfactory description of the bonding situations in NHC ligands. Singlet state of the normal NHC has electron-deficient aromaticity as compared to those of the abnormal and remote NHCs. Depending on the transition from the singlet to triplet state, NHCs become electron-deficient ligands except for remote NHC. Computational studies regarding electronic nature of free NHC ligands show that the π-electronic population of the formally vacant pπ orbital on the carbene atoms in abnormal and remote NHC is occurred as a result of the aromaticity of NHCs, not as a result of the direct electron donation from LP-orbitals of N atoms to carbene atom according to putative push-pull effect used in understanding the electronic stabilization of normal NHC. Increase in the aromaticity raises σ-donating ability of both imidazol- and pyrazol-based NHC ligands. Free abnormal and remote NHC ligands have higher σ-donation ability than normal NHC ligands. The lack of σ-donating ability of normal NHC is compensated by its relatively high π-accepting ability, whereas π-back donation abilities of abnormal and remote NHCs are prohibited by their almost fully occupied π-orbitals. Aromaticities of the triplet NHC ligands are higher than that of the lowest-lying triplet state of benzene. Increase in the aromaticity of NHC ligands decreases van der Waals shortening in TM-NHC bonds mainly due to diminishing dative character of these bonds.

Aromaticity balance, π-electron cooperativity and H-bonding properties in tautomerism of salicylideneaniline: the quantum theory of atoms in molecules (QTAIM) approach.

Topological analysis based on DFT calculations regarding proton transfer reaction in salicylideneaniline (SA) was performed to scrutinize possible changes in the intramolecular H-bond, π-electron delocalization and aromaticity levels of certain fragments. Quantum chemical calculations and natural bond orbital (NBO) analyses were carried out over a tautomeric ensemble whose members correspond to the molecules at different stages in tautomeric interconversion of SA. The elaboration of intramolecular hydrogen bonding in terms of the relevant topological parameters and the interpretation of certain dependencies regarding its strength were examined. The results show that delocalization index (DI) between donor and acceptor atom δ(O,N) is a useful topological parameter for describing H-bond strength, which is influenced by π-delocalization level within quasiaromatic chelate ring, indicating its resonance-assisted character. NBO analyses reveal that lone-pair (LP) population on N center also affects the strength of intramolecular H-bond in SA. Furthermore, π-electron transfer accompanying intramolecular proton migration in SA is brought into being through formally vacant non-Lewis type LP* orbital on the tautomeric proton. As a result of this, tautomeric protons in molecular entities near TS have hypovalent character due to the lack of electron population in the bonding orbital relative to that in LP* orbital. While H-bonds in the tautomeric ensemble of SA are predominantly partial covalent, molecular entities close to transition state have the strongest covalent H-bonds. The most important result is also that there are linear correlations between the orders of bonds (hydroxyl and amine) involving intramolecular H-bond and electron density values at the relevant BCPs due to partially covalent character of these bonds, contrary to exponential behavior as for purely covalent bonds. Quasiaromatic chelate ring formation is established not only to compel a reduced aromaticity of salicylidene ring but also to decrease in LP-population on N.

2,5-Dihexyl-3,6-diphenyl-pyrrolo-[3,4-c]pyrrole-1,4(2H,5H)-dione.

The asymmetric unit of the title compound, C(30)H(36)N(2)O(2), contains one half-mol-ecule, the other half being generated by a crystallographic inversion centre. The crystal structure is devoid of any classical hydrogen bonds however, non-classical C-H⋯O inter-actions link the mol-ecules into chains propagating in [001] and a C-H⋯π inter-action leads to the formation of a two-dimensional network in (011).

trans-[1,3-Bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene]dichlorido(triphenylphosphine-kappaP)palladium(II).

The title complex, [PdCl(2)(C(21)H(26)N(2))(C(18)H(15)P)], shows slightly distorted square-planar coordination around the Pd(II) metal centre. The Pd-C bond distance between the N-heterocyclic ligand and the metal atom is 2.028 (5) A. The dihedral angle between the two trimethylphenyl ring planes is 36.9 (2) degrees.