BippyPhos: A Highly Versatile Ligand for Pd-Catalyzed C−N,C−O and C−C Couplings

Numerous ligands have been designed for the Buchwald-Hartwig Amination (BHA). Among the ligands developed is BippyPhos. This ligand was originally designed to enable a coupling of primary amines with aryl halides. Further studies showed that the ligand has fairly broad utility for Pd-catalyzed C−N, C−O and C−C couplings. This review describes the various Pd-catalyzed applications involving BippyPhos as a supporting ligand. While BippyPhos may not often be the most optimal ligand for various Pd-catalyzed couplings, it typically will provide adequate results as a starting point prior to screening for optimization.     

Recent Advances in Electrochemical,Ni-Catalyzed C−C Bond Formation

Nickel-catalyzed cross-electrophile coupling (XEC) is an efficient method to form carbon-carbon bonds and has become an important tool for building complex molecules. While XEC has most often used stoichiometric metal reductants, these transformations can also be driven electrochemically. Electrochemical XEC (eXEC) is attractive because it can increase the greenness of XEC and this potential has resulted in numerous advances in recent years. The focus of this review is on electrochemical, Ni-catalyzed carbon-carbon bond forming reactions reported since 2010 and is categorized by the type of anodic half reaction: sacrificial anode, sacrificial reductant, and convergent paired electrolysis. The key developments are highlighted and the need for more scalable options is discussed.     

Iron-Catalyzed C−C Bond Formation via Chelation-Assisted C−H Activation

This review provides a brief overview of iron-catalyzed C−C bond forming reactions via heteroatom-assisted C−H bond activation, which have been extensively developed in the last decade. Three major types of reactions are discussed, namely, (1) C−H activation/C−C coupling using organometallic reagents under oxidative conditions, (2) C−H activation/C−C coupling using organic electrophiles under redox-neutral conditions, and (3) C−H activation/C−C coupling using unsaturated hydrocarbons under redox-neutral or oxidative conditions.     

Fatty acids,the immune response,and autoimmunity: A question of n−6 essentiality and the balance between n−6 and n−3

The essentiality of n−6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20∶4n−6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (18∶2n−6, LA) for membrane phospholipids. Low n−6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n−6 PUFA produced by γ-linolenic acid (18∶3n−6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n−6 PUFA, GLA, dihomo-γ-linolenic acid (20∶3n−6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (IGF)-β-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-α production. Low intakes of long-chain n−3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n−3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n−3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n−3 PUFA augment disease, whereas n−6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n−6 and n−3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n−6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.     

Microstructure and mechanical properties of carbon-precursor-added B4C and B4C−SiC ceramics subjected to pressureless sintering

Organic-carbon-precursor-added B₄C and B₄C–SiC ceramics were subjected to pressureless sintering at various temperatures. The carbon precursor increased the densification of the B₄C and B₄C–SiC ceramics sintered at 2200 °C to 95.6 % and 99.1 % theoretical density (T.D.), respectively. The pyrolytic carbon content of the B₄C–SiC composite decreased with increasing SiC content. The graphitization degree of pyrolytic carbon decreased slightly with the amount of carbon precursor and content of SiC. The 95 wt. % B₄C–5 wt. % SiC composite added with 7.5 wt. % carbon precursor and sintered at 2200 °C outperformed the other B₄C–SiC composites, and its sintered density, flexural strength, Young’s modulus, and microhardness were 98.6 % T.D., 879 MPa, 415 GPa, and 28.5 GPa, respectively. These values were higher than those of composites prepared via pressureless sintering and comparable to those of composites fabricated via hot pressing and/or using metal or oxide additives.     

Site-Selective Pyridination of Benzylic and Allylic C−H bonds via Radical-Radical Cross-Coupling

Herein, we report a modular photocatalytic platform for the site-selective pyridination of saturated hydrocarbon compounds employing organic photoredox catalysis to forge new carbon-carbon bonds. The site-selective C−H pyridination could couple benzylic/allylic C−H bonds with pyridylphosphonium salts, which installed directly and regioselectively from C−H heteroarenes through a radical-radical cross coupling mechanism. This synthetic methodology could tolerate a variety of functional groups, complex heteroarenes, even late-stage functionalization of pharmaceuticals selectively.     

Induction of apoptosis and apoptotic mediators in balb/C splenic lymphocytes by dietary n−3 and n−6 fatty acids

The present study was designed to investigate the effect of diatery n−6 and n−3 polyunsaturated fatty acids (PUFA) on anti-CD3 and anti-Fas antibody-induced apoptosis and its mediators in mouse spleen cells. Nutritionally adequate semipurified diets containing either 5% w/w corn oil (n−6 PUFA) or fish oil (n−3 PUFA) were fed to weanling female Balb/C mice, and 24 wk later mice were sacrificed. In n−3 PUFA-fed mice, serum and splenocyte lipid peroxides were increased by 20 and 28.3% respectively, compared to n−6 PUFA-fed mice. Further, serum vitamin F levels were decreased by 50% in the n−3 PUFA-fed group, whereas higher anti0Fas- and anti-CD3-induced apoptosis (65 and 66%) and necrosis (17 and 25%), compared to the n−6 PUFA-fed group, were found when measured with Annexin V and propidium iodide staining, respectively. In addition, decreased Bcl-2 and increased Fas-ligand (Fas-L) also were observed in the n−3 PUFA-fed group compared to the n−6 PUFA-fed group. No difference in the ratio of splenocyte subsets nor their Fas expression was observed between the n−3 PUFA-fed and n−6 PUFA-fed groups, whereas decreased proliferation of splenocytes was found in n−3 PUFA-fed mice compared to n−6 PUFA-fed mice. In conclusion, our results indicate that dietary n−3 PUFA induces higher apoptosis by increasing the generation of lipid peroxides and elevating Fas-L expression along with decreasing Bcl-2 expression. A reduced proliferative response of immune cells also was observed in n−3 PUFA-fed mice.     

Synthesis,characterization and catalytic properties of La2−x Sr x NiO4−δ

Various compositionsx in the catalyst system La_2–x Sr _x NiO_4– have been prepared by conventional techniques and characterized by X-ray powder diffraction, electron microscopy and BET surface measurements. The catalytic properties of these catalysts have been tested in the propylene oxidation reaction. The catalytic activity can be correlated with the oxygen content and with the strontium substitution.     

Growth,doping and characterization of epitaxial thin films and patterned structures of AlN,GaN, and AlxGa1−xN

Advancements in the doping of GaN and Al_xGa_1−xN thin films, and the growth of GaN and Al_xGa_1−xN structures on patterned heterostructure substrates via metalorganic vapor phase epitaxy are reported. The acceptor-type behavior of Mg-doped GaN films grown in N₂ diluents is presented. Net ionized impurity concentrations up to 8×10¹⁸ cm⁻³ and Hall mobilities up to ≈14 cm² V⁻¹ s⁻¹ were measured for Mg-doped films grown in N₂ in the as-grown condition. Donor and acceptor doping of Al_xGa_1−xN alloys was performed. Acceptor doping of Al_xGa_1−xN for x≤0.13 and donor doping for x≤0.58 were achieved for films deposited at 1100 °C. Lateral epitaxial overgrowth of GaN and Al_xGa_1−xN layers was investigated. The growth and coalescence of GaN and Al_xGa_1−xN stripes patterned in SiO₂ and/or SiN_x masks deposited on GaN, including aligned second lateral epitaxial overgrowth on initial laterally overgrown GaN layers, are discussed.     

Effect of 18∶1n−9, 20∶5n−3, and 22∶6n−3 on lipid accumulation and secretion by atlantic salmon hepatocytes

We have studied the effects of dietary FA on the accumulation and secretion of [³H]glycerolipids by salmon hepatocytes in culture. Atlantic salmon were fed diets supplemented with either 100% soybean oil (SO) or 100% fish oil (FO), and grew from an initial weight of 113±5 g to a final weight of 338 ±19 g. Hepatocytes were isolated from both dietary groups and incubated with [³H]glycerol in an FA-free medium; a medium supplemented with 0.75 mM of one of three FA—18∶1n−9, 20∶5n−3, or 22∶6n−3—or a medium supplemented with 0.75 mM of the sulfur-substituted FA analog tetradecylthioacetic acid (TTA), which cannot undergo β-oxidation. Incubations were allowed to proceed for 1,2,6, or 24 h. The rate of the secretion of radioactive glycerolipids with no FA added was 36% lower from hepatocytes isolated from fish fed the FO diet than it was from hepatocytes isolated from fish fed the SO diet. Hepatocytes incubated with 18∶1n−9 secreted more [³H]TAG than when incubated with no FA, whereas hepatocytes incubated with 20∶5n−3 or TTA secreted less labeled TAG than when incubated with no FA. This observation was independent of the feeding group. Hepatocytes incubated with 22∶6n−3 secreted the highest amounts of total [³H]glycerolipids compared with the other treatments, owing to increased secretion of phospholipids and mono- and diacylglycerols (MDG). In contrast, the same amounts of [³H]TAG were secreted from these cells as from cells incubated in an FA-free medium. The lipid-lowering effect of FO is thus independent of 22∶6n−3, showing that 20∶5n−3 is the FA that is responsible for the lipid-lowering effect. The ratio of TAG to MDG in lipids secreted from hepatocytes to which 20∶5n−3 or TTA had been added was lower than that in lipids secreted from hepatocytes incubated with 18∶1n−9 or 22∶6n−3, suggesting that the last step in TAG synthesis was inhibited. Morphometric measurements revealed that hepatocytes incubated with 20∶5n−3 accumulated significantly more cellular lipid than cells treated with 18∶1n−9, 22∶6n−3, TTA, or no treatment. The area occupied by mitochondria was also greater in these cells. The present study shows that dietary FO reduces TAG secretion from salmon hepatocytes and that 20∶5n−3 mediates this effect.     

Synthesis,Characterization, and Spectroscopic Analysis of NdxY1−xTiNbO6 Microwave Ceramics

Solid solutions of Nd_xY_1−xTiNbO₆ ceramics were prepared through the solid-state ceramic route. The materials were calcined at 1250°C and sintered in the range 1400–1550°C. The structure of the system was analyzed using the X-ray diffraction and vibrational spectroscopic analysis. The morphology and the sintering behavior of the samples were analyzed using scanning electron microscopy. The dielectric constant (ɛ_r), temperature coefficient of resonant frequency (τ_f), and the unloaded quality factor (Q_u) were measured in the microwave frequency region using the cavity resonator method. The ɛ_r and τ_f increased with an increase in the concentration of Nd in the solid solutions. Nearly zero temperature coefficient of resonant frequency was obtained for the Nd_0.6Y_0.4TiNbO₆ ceramic. Samples are of high quality factor and are useful for microwave applications.     

Shock-wave synthesis of diamonds from fullerenes C60−C100

Shock-wave synthesis of diamond from C₆₀–C₁₀₀-fullerene powder was first accomplished by using the explosive compaction technique with plane wave loading in the pressure range of 24–40 GPa. The compacts of various initial composition comprised diamond, FCC C₆₀-fullerite, graphite, and amorphous carbon. The largest diamonds of 0.1–1.0 m were obtained under shock loading of pellets consisting of copper powder with 5 wt. % fullerite at 24 and 38 GPa, and pellets consisting of copper powder with 10 wt. % fullerite at 40 GPa. The end product consists of diamond without intermediate diamondlike phases such as n-diamond and hexagonal diamond (lonsdaleite).Central Machine-Building Technology Research Institute, 109088 Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 2, pp. 131–138, March–April, 1995.     

Comparison of Mg–Al layered double hydroxides intercalated with OH− and CO32− for the removal of HCl,SO2, and NO2

Journal of Porous Materials - Two different Mg–Al layered double hydroxides (LDHs), OH?Mg–Al LDH and CO3?Mg–Al LDH, are prepared and utilized for the efficient removal...     

Synthesis,structure, optical and magnetic properties of Nd1−xAxMn0.5Co0.5O3−δ (A = Ba,Sr and Ca; x = 0 and 0.25)

The structural, optical, and magnetic properties of polycrystalline Nd_1-xA_xMn_0.5Co_0.5O_3−δ (A = Ba, Sr and Ca; x = 0 and 0.25) perovskite oxides were investigated. The powder XRD pattern demonstrates that the unit cell volume decreases with the changing A-site dopant type. The estimated bandgap energy (Eg) from UV–vis spectroscopic for NdMn_0.5Co_0.5O_3−δ, Nd_0.75Ba_0.25Mn_0.5Co_0.5O_3−δ, Nd_0.75Sr_0.25Mn_0.5Co_0.5O_3−δ and Nd_0.75Ca_0.25Mn_0.5Co_0.5O_3−δ are 3.27, 3.82, 3.79 and 3.53 eV respectively. The substitution of divalent element alters the absorption spectrum, while the redshift optical transition was observed with an increasing ionic radius of dopant. Temperature-dependent magnetization exposes that the Curie temperature (TC) gradually decreases with the decreasing size of alkaline earth metals, and glassy nature was observed at a lower applied magnetic field. The observation of TC can be well explained by the considering of the cationic size disorder parameter in A-site than the random distribution of B-site ions.     

Chemical synthesis,compositional, morphological,structural, optical and magnetic properties of Zn1−xDyxS nanoparticles

Zn_1−xDy_xS (x=0, 0.02 and 0.04) nanoparticles (NPs) were synthesized by chemical refluxing technique at 100 °C. The prepared samples were analyzed by studying their compositional, morphological, structural, optical and magnetic properties. EDS analysis confirmed the presence of zinc, dysprosium and sulfur in the samples in near stoichiometric ratio. The X-ray diffraction patterns do not show any Dy related peaks for the as-synthesized ZnS nanoparticles. The average diameter of the particles confirmed by TEM studies, was in the range 2–4 nm. Raman studies revealed that all the samples are single phase and exhibit cubic structure. From DRS studies, the band-gap was found to be in the range of 3.85–3.70 eV. All the doped ZnS nanoparticles exhibit ferromagnetic behavior with the Curie temperature higher than room temperature and the magnetic properties of doped ZnS nanoparticles depend on the concentration of Dy ions.     

Dietary intakes and food sources of n−6 and n−3 PUFA in french adult men and women

The intake of individual n−6 and n−3 PUFA has been estimated in 4,884 adult subjects (2,099 men and 2,785 women), volunteers from the French SU.VI.MAX intervention trial. The food intakes of each subject were recorded in at least ten 24-h record questionnaires completed over a period of 2.5 yr, allowing the estimation of the daily intake of energy; total fat; and linoleic, α-linolenic, arachidonic, eicosapentaenoic (EPA), n−3 docosapentaenoic (DPA), and docosahexaenoic (DHA) acids. The mean total fat intake corresponded to 94.1 g/d (36.3% of total energy intake) in men and 73.4 g/d (38.1% of energy) in women. The intake of linoleic acid was 10.6 g/d in men and 8.1 g/d in women, representing 4.2% of energy intake; that of α-linolenic acid was 0.94 g/d in men and 0.74 g/d in women, representing 0.37% of energy intake, with a mean linoleic/α-linolenic acid ratio of 11.3. The mean intakes of long-chain PUFA were: arachidonic acid, 204 mg/d in men and 152 mg/d in women; EPA, 150 mg/d in men and 118 mg/d in women; DPA, 75 mg/d in men and 56 mg/d in women; DHA, 273 mg/d in men and 226 mg/d in women; long-chain n−3 PUFA, 497 mg/d in men and 400 mg/d in women. Ninety-five percent of the sample consumed less than 0.5% of energy as α-linolenic acid, which is well below the current French recommendation for adults (0.8% of energy). In contrast, the mean intakes of long-chain n−6 and n−3 PUFA appear fairly high and fit the current French recommendations (total long-chain PUFA: 500 mg/d in men and 400 mg/d in women; DHA: 120 mg/d in men and 100 mg/d in women). The intakes of α-linolenic acid, and to a lesser extent of linoleic acid, were highly correlated with that of lipids. Whereas the main source of linoleic acid was vegetable oils, all food types contributed to α-linolenic acid intake, the main ones being animal products (meat, poultry, and dairy products). The main source of EPA and DHA (and of total long-chain n−3 PUFA) was fish and seafood, but the major source of DPA was meat, poultry, and eggs. Fish and seafood consumption showed very large interindividual variations, the low consumers being at risk of insufficient n−3 PUFA intake.     

Novel epoxy/expandable graphite halogen-free flame retardant composites−preparation, characterization, and properties

In this work, expandable graphite (EG) was grafted using a coupling agent, 3-isocyanatopropyltriethoxysilane (IPTS). EG has a -O-C₂H₅ (-OEt) functional group which reacts with a polymer matrix through the sol-gel reaction. EG was functionalized by the coupling agent to form a covalent bonding between organic and inorganic phases, increasing the compatibility between the fillers and polymer, and thereby enhancing the thermal stability of the composites. FT-IR and X-ray photoelectron spectroscopy (XPS) were adopted to characterize the grafting reaction between IPTS and EG. Thermogravimetric analysis (TGA), the derivative of thermogravimetric weight (DTG) and the difference between the thermogravimetric weights (TG△) were employed to calculate the thermal stability of the composites. The limiting oxygen index (LOI) was utilized to classify the composites by flame retardancy. A scanning electron microscope (SEM) was applied to observe their morphology, and the behavior of expansion was discussed after the materials were burnt. TGA/MS was used to analyze the gas products during thermal degradation. The results demonstrate that functionalized EG can improve the thermal stability of composites and increase the flame retardancy.     

Preparation and ionic conduction of CaZr1−xScxO3−α ceramics

A series of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) perovskite oxide ceramics were successfully fabricated at 1400 °C for 10 h and then further sintered at 1650 °C for 10 h via a solid-state reaction sintering process. Conductivities of the ceramics were measured under the atmosphere that contains 1% H₂/Ar and 5.63 kPa H₂O/Ar by the electrochemical impedance spectra technique. It was found that the conductivities of CaZr_1−xSc_xO_3−α (x=0, 0.05, 0.10, 0.15) ceramics increased with the increase of the measuring temperature, and the conductivity achieved its maximum value of 2.03×10⁻⁵–6.5×10⁻³ S cm⁻¹ when the doping amount of Sc (x) was 0.10. Additionally, element doping can increase the conductivities and decrease the conductivity activation energies of CaZr_1−xSc_xO_3−α ceramics. The results of transport number measurement indicated that the CaZr_0.9Sc_0.1O_3−α is almost a pure protonic conductor at 500–750 °C, while it is a mixed protonic-oxygen ionic-electronic conductor at 750–1300 °C.     

A-site strontium doping effects on structure,magnetic, and photovoltaic properties of (Bi1−xSrx)FeO3−δ multiferroic ceramics

Raman spectroscopy, X-ray diffraction (XRD), magnetization hysteresis loop, synchrotron X-ray absorption spectroscopy, and photovoltaic effects have been measured in (Bi_1−xSr_x)FeO_3−δ (BFO100xSr) ceramics for x=0.0, 0.05, 0.10, and 0.15. Raman spectra and XRD reveal a rhombohedral R3c structure in all compounds. A-site Sr²⁺ doping increases fluctuations in cation-site occupancy and causes broadening in Raman modes. BFO15Sr exhibits a strong ferromagnetic feature due to reduction of FeOFe bond angle evidenced by the extended synchrotron X-ray absorption fine structure. The heterostructure of indium tin oxide (ITO) film/(Bi_1−xSr_x)FeO_3−δ ceramic/Au film exhibit clear photovoltaic (PV) responses under blue illumination of λ=405 nm. The maximal power-conversion efficiency and external quantum efficiency in ITO/BFO5Sr/Au are about 0.004% and 0.2%, respectively. A model based on optically excited charges in the depletion region between ITO and (Bi_1−xSr_x)FeO_3−δ can well describe open-circuit voltage and short-circuit current as a function of illumination intensity.