Gas-phase kinetics of elimination reactions of pentane-2,4-dione derivatives. Part ii [1]. Thermolysis of derivatives and analogues of 3-phenylhydrazonopentane-2,4-dione

Six analogues and derivatives (1–6) of 3-phenylhydrazonopentane-2,4-dione (7) were subjected to gas-phase thermolysis. The Arrhenius log A (s⁻¹) and Ea (kJ mol⁻¹) of the analogues (1–5) are, respectively: 10.42 and 140.8 for 1-cyano-1-phenyl-hydrazonopropanone (1) , 11.19 and 135.4 for 1-cyano-1-( -nitrophenylhydrazono)-propanone (2) , 10.68 and 144.9 for 1-cyano-1-( -methoxyphenylhydrazono)propanone (3) , 11.76 and 137.8 for 1-cyano-3-phenyl-1-phenylhydrazonopropanone (4) , and 11.29 and 145.9 for 1-cyano-1-phenylhydrazonobutanone (5) . The corresponding values for ethyl 3-oxo-2-phenylhydrazonobutanoate (6) are 11.90 s⁻¹ and 143.3 kJ mol⁻¹. The rates of reaction at 600 K are compared with those of the title diketone (7) and of pentane-2,4-dione (8) and rationalized in terms of a plausible elimination pathway involving a semiconcerted six-membered transition state. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 457–462, 1998     

Evaluation of Substituted Pyrazole-Based Kinase Inhibitors in One Decade (2011–2020): Current Status and Future Prospects

Pyrazole has been recognized as a pharmacologically important privileged scaffold whose derivatives produce almost all types of pharmacological activities and have attracted much attention in the last decades. Of the various pyrazole derivatives reported as potential therapeutic agents, this article focuses on pyrazole-based kinase inhibitors. Pyrazole-possessing kinase inhibitors play a crucial role in various disease areas, especially in many cancer types such as lymphoma, breast cancer, melanoma, cervical cancer, and others in addition to inflammation and neurodegenerative disorders. In this article, we reviewed the structural and biological characteristics of the pyrazole derivatives recently reported as kinase inhibitors and classified them according to their target kinases in a chronological order. We reviewed the reports including pyrazole derivatives as kinase inhibitors published during the past decade (2011–2020).     

A novel method for the synthesis of 1-aryltetrahydroisoquinolines

Carbenium ions generated from substituted benzhydryls using acid catalysis undergo smooth intramolecular trapping by pendant sulfonamide groups to provide excellent yields of 1-aryltetrahydroisoquinolines.     

Mg–Al layered double hydroxide intercalated with sodium lauryl sulfate as a sorbent for <Superscript>152+154</Superscript>Eu from aqueous solutions

In the present study, Mg–Al layered double hydroxide intercalated with nitrate anions (LDH-NO₃) was synthesized, modified with the anionic surfactant, sodium lauryl sulfate, and applied for the removal of ^152+154Eu from aqueous solutions. Modification of the as-synthesized Mg–Al layered double hydroxide was carried out at surfactant concentration of 0.01 M (the organo-LDH produced denoted LDH-NaLS). The as-synthesized and surfactant-intercalated LDHs were characterized by FT-IR and energy-dispersive X-ray spectroscopy techniques. The effect of some variables such as solution pH, contact time and sorbate concentration on removal of ^152+154Eu was investigated. The kinetic data obtained were well fitted by the pseudo-second-order kinetic model rather than the pseudo-first-order model. Intraparticle diffusion model showed that sorption of ^152+154Eu proceed by intraparticle diffusion together with boundary layer diffusion. Experimental isotherm data were well described by Langmuir model. Organo-LDH was found to have higher capacity (156.45 mg g⁻¹) for europium than the as-synthesized LDH-NO₃ (119.56 mg g⁻¹). Comparing LDHs capacities obtained for Eu(III) in the present work with other sorbents reported in literature indicated that LDHs have the highest capacities. Application of the developed process for removal of ^152+154Eu(III) from radioactive process wastewaters was also studied and the obtained results revealed that these LDHs are promising materials for treatment of radioactive wastewaters.     

New Adenosine Derivatives from Aizoon canariense L.: In Vitro Anticholinesterase,Antimicrobial, and Cytotoxic Evaluation of Its Extracts

Aizoaceae is a large succulent family characterized by many psychoactive species. Aizoon canariense L., a wild neglected plant traditionally used in gastrointestinal ailments, has been the subject of a limited number of phytochemical and biological studies. Therefore, herein, we investigated the in vitro cytotoxic, antimicrobial, and anticholinesteraseactivity of the aerial parts of A. canariense L. and analyzed the phytochemical compositions of the lipoidal and alkaloidal fractions. Petroleum ether extract showed the presence of behenic and tricosylic acid, while an in-depth investigation of the alkaloidal fraction revealed the identification of new adenine based alkaloids (1–5), which were isolated and identified for the first time from Aizoon canariense L. Their structures were elucidated based on extensive spectroscopic analyses. The alkaloidal extract showed a powerful cytotoxic effect (IC₅₀ 14–28 μg/mL), with the best effect against colon carcinoma, followed by liver and breast carcinomas. The alkaloidal extract also had a potent effect against Candida albicans and Escherichia coli, with minimum inhibitory concentrations (MIC) values of 312.5 and 625 µg/mL. The in vitro anticholinesterase activity was potent, with IC₅₀ < 200 ng/mL for the tested extracts compared with 27.29 ± 0.49 ng/mL for tacrine.     

Improved Sensitivity for Imaging Spin Trapped Hydroxyl Radical at 250 MHz

Radicals, including hydroxyl, superoxide, and nitric oxide, play key signaling roles in vivo. Reaction of these free radicals with a spin trap affords more stable paramagnetic nitroxides, but concentrations in vivo still are so low that detection by electron paramagnetic resonance (EPR) is challenging. Three innovative enabling technologies have been combined to substantially improve sensitivity for imaging spin‐trapped radicals at 250 MHz. 1) Spin‐trapped adducts of BMPO have lifetimes that are long enough to make imaging by EPR at 250 MHz feasible. 2) The signal‐to‐noise ratio of rapid‐scan EPR is substantially higher than for conventional continuous‐wave EPR. 3) An improved algorithm permits image reconstruction with a spectral dimension that encompasses the full 50 G spectrum of the BMPO–OH spin adduct without requiring the wide sweeps that would be needed for filtered backprojection. A 2D spectral–spatial image is shown for a phantom containing ca. 5 μM BMPO–OH.     

Exploiting stored TiO2 electrons for multi-electron reduction of an azo dye methyl orange in aqueous suspension

The mechanism of multi-electron reduction of methyl orange (MO) azo dye on TiO₂ nanoparticles has been studied performing stopped flow technique. A multi-electron reduction of azo dye has been investigated. It was found that a multistep reduction of the dye takes place: the stored electrons reduce the conjugative system of the azo group resulting in the decolorization of the dye and leading to the formation of hydrazine derivative followed by further 2 electron transfer step leading to the cleavage of the N–N bond and the formation of aromatic amines. The FTIR analysis of the products confirms the proposed mechanism of the dye reduction. The kinetic parameters and of the multi-electrons reduction of the MO have been determined. The rate of MO reduction was found to be dependent on both the TiO₂ electrons and the dye concentrations.     

Non-covalent polymerisation in the solid state: halogen-halogen vs. methyl-methyl interactions in the complexes of 2,4-di(2-pyridyl)-1,3,5-triazine ligands

Fe(II), Co(II), Ni(II) and Cu(II) complexes based on the triazine ligand 2,4-di(2'-pyridyl)-6-(p-bromo-phenyl)-1,3,5-triazine have been synthesised and characterised. The electrochemical, magnetic and spectroscopic properties of the complexes have also been investigated, and the electron deficient triazine ligand has been shown to affect each of these properties. Further investigation of solid state structures of the ligand and its Fe(II), Co(II) and Cu(II) complexes has established that stabilising Br-Br interactions exist which link neighbouring molecules to form one-dimensional tapes. A slight modification of the ligand, i.e., using 2,4-di(2'-pyridyl)-6-(p-methylphenyl)-1,3,5-triazine, in which the phenyl substituent has changed from a bromine to a methyl group, eliminates the one-dimensional tape and gives rise to significant pi-stacking interactions in the solid state.     

Tuning the excited-state energy of the organic chromophore in bichromophoric systems based on the Ru(II) complexes of tridentate ligands

A series of new heteroleptic and homoleptic Ru(II) complexes containing variously substituted bis(pyridyl)triazine ligands has been prepared and their absorption spectra, redox behaviour and luminescence properties (both in fluid solution at room temperature and in a rigid matrix at 77 K) have been investigated. For some compounds, X-ray structures have also been determined. The new bis(pyridyl)triazines incorporate additional chromophores, such as biphenyl, phenanthrene, anthracene and bromoanthracene derivatives, so the Ru(II) species can be considered as multichromophoric species. The absorption spectra and redox properties of all the metal complexes have been assigned to features belonging to specific subunits, thus suggesting that these species can be regarded as multicomponent, supramolecular assemblies from an electronic coupling point of view. Whereas most of the complexes exhibit luminescence properties that can be attributed to metal-to-ligand charge-transfer (MLCT) states involving the metal-based subunit(s), the species containing the anthryl and, even more, the brominated anthryl chromophores exhibit complicated luminescence behaviour. For example, 2 d (the anthryl-containing heteroleptic metal compound) exhibits MLCT emission at room temperature and emission from the anthracene triplet at 77 K; 2 e (the bromo-substituted anthryl-containing heteroleptic metal compound) exhibits anthryl-based emission at 77 K and MLCT emission at room temperature, but with a prolonged lifetime, thus suggesting equilibration between two triplet states that belong to different chromophores. The equilibration regime between MLCT and aromatic hydrocarbon triplet states is therefore reached by suitable substitution on the organic chromophore.