An efficient protocol of iridium-catalyzed allylic substitution reaction and its application to polymer synthesis: complementary regio- and stereoselective allylation polycondensation via Ir and Pd catalyses

An efficient protocol of the Ir-catalyzed allylic substitution reaction is reported using N,O-bis(trimethylsilyl)acetamide as a base in the presence of nBu4NF as a cocatalyst. The reaction completely proceeded under very mild conditions, and a branched allylated compound that is not easy to access via the Tsuji-Trost reaction can be synthesized. The reaction system is practical enough to be applicable for polymer syntheses. The Ir- and Pd-catalyzed allylation polycondensations generally show complementary regio- and stereoselectivities. The Ir-catalyzed reaction is versatile, and a mixed dual regioselectivity such as a branched-linear selectivity on each electrophile can also be achieved.     

Complexation study of Schiff base ligand: pyridin-2-ylimino methyl naphthanol with Co+2, Mn+2 and Ni+2 ions in solid and solution phase

Schiff base pyridin-2-ylimino methyl naphthanol (HL) was synthesized and characterized by spectroscopic (FTIR, ESIMS, and NMR) techniques. The ligand was reacted with perchlorate salts of Mn⁺², Co⁺², and Ni⁺². ESIMS mass spectra indicate the formation of mononuclear complex ML₂ for all three complexes. CoL₂ crystallizes in P₂1/n space group, adopting a distorted tetrahedral geometry where Co is in a N₂O₂ donor environment. Structure of the Co complex was optimized by DFT calculation. Solution-phase complexation between the ligand and the three metals ions: Mn⁺², Co⁺², and Ni⁺² (pH 7.2 in tris buffer), in CH₃CN–H₂O was performed spectrophotometrically by UV–vis spectral study. Job’s plot from each titration suggests a 1 : 2 metal to ligand combination. The association constants for the formation of ML₂ are as follows: Mn (19.80 × 10³ M^?1), Co (14.54 × 10³ M^?1) and Ni (19.04 × 10³ M^?1).     

Regioselective,Solvent‐ and Metal‐Free Chalcogenation of Imidazo[1,2‐a]pyridines by Employing I2/DMSO as the Catalytic Oxidation System

Highly efficient molecular‐iodine‐catalyzed chalcogenations (S and Se) of imidazo[1,2‐a]pyridines were achieved by using diorganoyl dichalcogenides under solvent‐free conditions. This approach afforded the desired products that had been chalcogenated regioselectively at the C3 position in up to 96 % yield by using DMSO as an oxidant, in the absence of a metal catalyst, and under an inert atmosphere. This mild, green approach allowed the preparation of different types of chalcogenated imidazo[1,2‐a]pyridines with structural diversity. Furthermore, the current protocol was also extended to other N‐heterocyclic cores.     

Synthesis of a new scaffold: the 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione nucleus

This paper describes a modified method of preparation of a number of alpha-aryl-alpha-(pyridazin-3-yl)-acetonitriles via the C-arylation reaction of the corresponding carbanionsof phenylacetonitriles using 3-chloropyridazine derivatives. KOH and DMSO were used inthe deprotonation process, which made the reaction very simple and safe to perform.Nitriles were obtained in the hydrolysis reaction to the corresponding alpha-aryl-alpha-(pyridazin-3-yl)-acetamide derivatives, which were next subjected to cyclization to afford the finalproducts. A number of new derivatives of 7H,8H-pyrimido[1,6-b]pyridazin-6,8-dione weresynthesized in the cyclocondensation reaction of respective alpha-aryl-alpha-(pyridazin-3-yl)-acetamides with diethyl carbonate in the presence of EtONa. The structure andcomposition of the new compounds were confirmed by IR, (1)H- and (13)C- NMR analysesand by elemental C, H and N analysis.     

New ceramic-carbon composites for electrodes for electrochemical capacitors

A new class of composite materials is introduced. Fine powders of silica, titania, Y-modified zirconia, and three types of alumina were pressed and sintered to form porous monoliths with relatively uniform pore structure. Carbon was then deposited in the pores of such monoliths by thermal decomposition of dichloromethane, cyclohexene, and glucose. The structure of the carbon deposit was studied by low-temperature nitrogen adsorption and by thermal analysis. The composite materials were used as electrodes in electrochemical capacitors with 1-ethyl-3-methylimidazolium trifluoromethylsulfonate (a low-temperature ionic liquid) as the electrolyte. High capacitances were observed for glucose-derived materials, which had high specific surface areas.     

The Structural Determinants for α1-Adrenergic/Serotonin Receptors Activity among Phenylpiperazine-Hydantoin Derivatives

Several studies confirmed the reciprocal interactions between adrenergic and serotoninergic systems and the influence of these phenomena on the pathogenesis of anxiety. Hence, searching for chemical agents with a multifunctional pharmacodynamic profile may bring highly effective therapy for CNS disorders. This study presents a deep structural insight into the hydantoin-arylpiperazine group and their serotonin/α-adrenergic activity. The newly synthesized compounds were tested in the radioligand binding assay and the intrinsic activity was evaluated for the selected derivatives. The computer-aided SAR analysis enabled us to answer questions about the influence of particular structural fragments on selective vs. multifunctional activity. As a result of the performed investigations, there were two leading structures: (a) compound 12 with multifunctional adrenergic-serotonin activity, which is a promising candidate to be an effective anxiolytic agent; (b) compound 14 with high α_1A/α_1D affinity and selectivity towards α_1B, which is recommended due to the elimination of probable cardiotoxic effect. The structural conclusions of this work provide significant support for future lead optimization in order to achieve the desired pharmacodynamic profile in searching for new CNS-modulating agents.     

Current advances in molecularly imprinted polymers and their release mechanisms in drug delivery systems

Molecularly imprinted polymer (MIP) has gained wide interest among researchers due to its unique molecular recognition of the template that is suitable as a drug carrier. Therefore, the preparation and formulation of the MIP are significant to suit the needs of the intended use. Due to its significance in drug delivery, this review aims to highlight various methods in the preparation of MIP, the composition for both controlled and stimuli-responsive drug delivery systems, and the release mechanism of the drugs. In drug delivery systems, MIP should have a sustained release performance as well as flexibility in surface modification for targeted delivery via a range of stimuli-responses, including  external stimuli (magnetic, light) and internal stimuli (pH, temperature, redox, biological). The properties of sustained release and targeted delivery of the MIP can improve the drug's therapeutic efficacy as well as the breakthrough for the tumor targeting application.     

Modes and Fields of Two Stacked Dielectric Resonators in a Cavity of an Electron Paramagnetic Resonance Probe

An electron paramagnetic resonance (EPR) probe consisting of two dielectric resonators (DRs) and a cavity (CV) is ideal for EPR experiments where both signal enhancement and tuning capabilities are required. The coupling of two DRs, resonating in their \({\text{TE}}_{01\delta }\) mode and a CV resonating in its \({\text{TE}}_{011}\) mode, is studied using energy-coupled mode theory (ECMT). The frequencies and eigenvectors of the three coupled modes are analytically derived. As predicted numerically, ECMT confirms that the \({\text{TE}}^{ + + - }\) and \({\text{TE}}^{ + - - }\) modes are indeed found to be degenerate at a specific distance between the two DRs \(d_{12}\). Additionally, the condition at which degeneracy occurs is specified. For a considerable range, the calculated frequency of the \({\text{TE}}^{ + + + }\) mode changes linearly with respect to \(d_{12}\). The \({\text{TE}}^{ + + + }\) mode showed a 500 MHz frequency change over a distance of 2 cm, when the resonance frequency is around 9.7 GHz. This enables the experimentalist to linearly tune the probe over this large frequency range. Finally the asymmetric configuration, where one of the resonators (DR2) is kept at the cavity center and the other one is allowed to move along the cavity axis, is studied. It is estimated that the frequency changes by 600 MHz over a distance of 1.5 cm. A formula for the magnitude of the magnetic field along the cavity axis, where the EPR samples are usually placed, is developed. This is crucial in determining the magnetic field in the vicinity of the sample and the probe’s filling factor.     

Structural and electrical study of Ce-substituted bismuth vanadate

Samples of Ce^IV-substituted bismuth vanadate, formulated as Bi₄Ce_xV_2−xO_{11−(x/2)−δ}; 0≤x≤0.30, were synthesized by solid-state reactions. The phase structure and electrical conductivity were investigated using X-ray powder diffraction, FT-IR, differential thermal analysis and AC impedance spectroscopy. For a low composition range, two phase transitions, α↔β and β↔γ, were exhibited in which the system mimics in most events the parent compound. Impedance analysis evidenced no relationship between the blocking effect of charge carriers and structural changes at ambient temperatures. However, the temperature dependence of conductivity was correlated with the stability region of various phases within the system.     

The study of cyclooctene oxidation with molecular oxygen catalyzed by VSi2

The catalytic effect of VSi₂ on initial stages of the liquid-phase oxidation of cyclooctene by molecular oxygen was studied. The vanadium disilicide influences on the oxidation process in the presence of hydroperoxide. VSi₂ takes part in a radical formation stage by catalysis of hydroperoxide decomposition reaction. The catalyst was investigated before and after reaction using FTIR spectroscopy. From the data obtained, the kinetic model of the catalytic oxidation process was proposed and the equation for the reaction rate was derived. The equation has described all observed dependences of reaction rate on the concentration of reactants and content of catalyst.