Suzuki reaction of aryl chlorides using saturated N‐heterocarbene ligands

From readily available starting materials, six 1,3‐dialkyl‐imidazolinium bromides ( 2a–f ) have been prepared and characterized by conventional spectroscopic methods and elemental analyses. The incorporation of saturated N‐heterocyclic carbenes into palladium precatalysts gives high catalyst activity in the Suzuki coupling of deactivated aryl chloride substrates in aqueous media. The complexes were generated in the presence of Pd(OAc)₂ by in situ deprotonation of 2a–f . © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:557–561, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20140     

Determination of nucleation kinetics of potassium tetraborate tetrahydrate

In this study, the metastable zone width of potassium tetraborate tetrahydrate was determined for four different temperatures and cooling rates. The induction period of potassium tetraborate tetrahydrate in aqueous solution was examined according to polythermal method by using visual observation. The induction period, which changes inversely proportional to the nucleation rate has been used to determine the interfacial tension between the potassium tetraborate tetrahydrate and aqueous solution. By using interfacial tension, the nucleation parameters such as Gibbs free energy change for the formation of critical nucleus, ΔG*, free energy of formation, ΔG, radius of critical nucleus, r and number of molecules in the critical nucleus, i* has been calculated. The effect of Li⁺ and Ca²⁺ impurities on metastable zone width has been studied. The metastable zone width of aqueous solution of potassium tetraborate tetrahydrate decreases with increasing impurity concentrations. The equilibrium saturation concentration change is high in the presence of Ca²⁺ ions while it is low in the presence of Li⁺ ions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phytochemical Profiling and Evaluation of the Hepatoprotective Effect of Cuscuta Campestris by High-Performance Liquid Chromatography with Diode Array Detection

Plant-derived antioxidant compounds have the potential to prevent cell damage caused by free radicals. As a holoparasitic plant, Cuscuta campestris Yuncker is being valorized for treatment of liver injury and cancer prevention in traditional medicine. The main purpose of this present study is to elucidate the antioxidant- and anticancer-associated contents of C. campestris by spectroscopic and chromatographic methods. Diethyl ether, ethyl acetate, methanol, n-butanol, and water were used as extraction solvents to reach a wide range of secondary metabolites synthesized by this plant. Antioxidant potentials of these extracts were characterized by (2,2-diphenyl-1-picrylhydrazyl)-free radical scavenging activity. Their anticancer activities were evaluated on SNU-398 hepatocellular carcinoma cells and controlled on the normal adult human dermal fibroblasts (hDFs) cells. Their phenolic compounds were analyzed by high-performance liquid chromatography with diode array detector to illuminate the responsible anticancer agent(s). The ethyl acetate extract revealed the most significant antioxidant effect. Methanol and ethyl acetate extracts were found to be cytotoxic on the SNU-398 cell lines with CC₅₀ values of 18.7 and 19.6?µg?mL^?1, respectively, whereas these extracts were not cytotoxic to the adult hDFs cells. Due to their abundance in the extracts, isorhamnetin, kaempferol, and quercetin may have caused this anticancer activity. Methanol extract has the highest concentration of phenolic compounds. Based on chromatographic analyses, we propose that these anticancer effects were positively correlated with plant phenolic compounds. The results showed that this plant is worth further study for its therapeutic uses.     

Transition Metal Ion-binding Properties of a 14-Membered N2O2S2- Macrobicyclic Ligand

The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N₂O₂S₂-macrobicycle. Metal picrates such as Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺,Cu²⁺ and Cd²⁺ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb²⁺ only among the other metals. The extraction constant (log K _ex) was determined to be 13.8 for Pb²⁺ complex.     

Quantum chemical studies on some potentially tautomeric oxazolidin-4-one derivatives and their thio and azo anologs

The basicities and nucleophilicities along with prototautomerism of biologically active oxazolidin-4-one and its thio and azo analogs were investigated by semi-empirical methods. The oxo and thion protonation were found to be easier than that of azo protonation for 4-oxo and 4-thion derivatives whereas amino protonation was found to be easier than imino and azo protonation in 4-imino derivative. The preferred tautomeric form for 4-oxo and 4-thion derivatives were found to be the keto and thion forms, respectively, whereas the amino form was found to be preferred in 4-imino derivatives. An acceptable correlation between gas phase proton affinities and aqueous phase acidity constants as well as the correlation between nucleophilicity and acidity constants was observed.     

Liquid crystalline mesophases of pluronics (L64, P65, and P123) and transition metal nitrate salts ([M(H2O)6](NO3)2)

The triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymers, Pluronics (L64, P65, and P123), form liquid crystalline (LC) mesophases with transition metal nitrate salts (TMS), [M(H(2)O)(n)](NO(3))(2), in the presence and absence of free water in the media. In this assembly process, M-OH(2) plays an important role as observed in a TMS:C(n)EO(m) (C(n)EO(m) is oligo(ethylene oxide) nonionic surfactants) system. The structure of the LC mesophases and interactions of the metal ion-nitrate ion and metal ion-Pluronic were investigated using microscopy (POM), diffraction (XRD), and spectroscopy (FTIR and micro-Raman) techniques. The TMS:L64 system requires a shear force for mesophase ordering to be observed using X-ray diffraction. However, TMS:P65 and TMS:P123 form well structured LC mesophases. Depending on the salt/Pluronic mole ratio, hexagonal LC mesophases are observed in the TMS:P65 systems and cubic and tetragonal LC mesophases in the TMS:P123 systems. The LC mesophase in the water/salt/Pluronic system is sensitive to the concentration of free (H(2)O) and coordinated water (M-OH(2)) molecules and demonstrates structural changes. As the free water is evaporated from the H(2)O:TMS:Pluronic LC mesophase (ternary mixture), the nitrate ion remains free in the media. However, complete evaporation of the free water molecules enforces the coordination of the nitrate ion to the metal ion in all TMS:Pluronic systems.     

New and clean synthesis of N-substituted pyrroles under microwave irradiation

N-Substituted homochiral pyrrole derivatives were synthesized by the ring-closure reaction of cis-1,4-dichloro-2-butene with various amine compounds on a silica surface under microwave irradiation.     

Measurement of angular dependencies of M X-ray differential cross sections and production cross sections using 5.96 keV photons

The differential cross sections of the emission of M-shell fluorescence X-rays from Tl and Pb have been measured by 5.96 keV photons at seven angles ranging from 50° to 110°. The differential cross section is found to decrease with the increasing emission angle, showing an anisotropic spatial distribution of M-shell fluorescence X-rays. Furthermore, M-shell fluorescence cross sections and the average fluorescence yields were measured for Pt, Au, Hg, Tl, Pb, Bi, Th, and U at an excitation energy of 5.96 keV using a Si(Li) detector. The experimental results of the total M X-ray fluorescence cross sections and M-shell fluorescence yields were compared with the theoretical values.This revised version was published online in November 2005 with corrections to the Cover Date.