Intramolecular cyclization of nerol and the related (z)-allylic alcohols by means of TiCl4-PhNHMe complex. Synthesis of nezukone

Nerol is cyclized to terpinyl chloride or bromide in the presence of TiX₄-PhNHMe (1:1) complex in dichloromethane at ?23 °C, while cyclization of ($\text{Z}$)-allylic alcohols CH₂=CR-CH₂CH₂CMe=CHCH₂OH (R = H, Me, Cl) produces seven-membered ring products in fair yields.     

Determination of serum cortisol by reversed-phase liquid chromatography using precolumn sulphuric acid-ethanol fluorescence derivatization and column switching.

An assay method for serum cortisol, using precolumn sulphuric acid-ethanol fluorescence derivatization and reversed-phase liquid chromatography with a column-switching technique, has been developed. The crude precolumn fluorescence cortisol derivative was prepared by the addition of sulphuric acid to serum deproteinized with ethanol, and directly injected onto an octadecylsilane-bonded silica gel (ODS) precolumn for concentration and purification. After switching columns the samples were separated using an ODS analytical column and monitored fluorimetrically. When the pH of the mobile phase in the analytical separator decreased to 1.85, the emission wavelength of the cortisol derivative changed to 520 nm (excitation of 365 nm) and the fluorescence intensity increased. Among the sulphuric acid-ethanol derivatives of various steroids, cortisol, corticosterone and testosterone emitted fluorescence. However, their retention times differed from those of the cortisol derivatives (12.5 min). The detection limit of cortisol was 0.3 micrograms/dl (signal-to-noise ratio of 3). Use of the fully automated column-switching system contributed to good reproducibility and recovery.     

Aldol reaction of aluminium enolate resulting from 1,4-addition of Me2AlSPh to α,β-unsaturated carbonyl compound. A 1-acylethenyl anion equivalent

Me₂AlSPh or Me₂AlSeMe adds to α,β-unsaturated carbonyl compounds in 1,4-fashion. The resulting aluminium enolates react with aldehydes effectively to afford the adducts of the title anion after formal PhSH (or MeSeH)-elimination.     

Nondestructive neutron activation analysis of rare earth elements in hot spring water samples in Kusatsu-shirane area,Japan

Hot spring water samples have been analyzed for their rare earth elements (REE's) determination by the nondestructive neutron activation method. Five REE's, La, Ce, Sm, Eu and Yb, have consequently been detected and determined with satisfactory precision. The method has been found to be simple and suited for the simultaneous analyses of several samples. To determine all the REE's, however, some pretreatment of the samples will be necessary.     

Reaction of trialkylboranes with 2-bromo-6-lithiopyridine: Stereospecific alkylative cleavage of pyridine ring

Reaction of 2-bromo-6-lithiopyridine with trialkylboranes affords 5-alkyl-5-dialkylboryl-2-(Z), 4(E)- pentadienenitriles by stereospecific alkylative cleavage of the pyridine ring. These intermediary vinylboranes are versatile reagents for the preparation of 5-alkyl-2(Z), 4(E)-pentadienenitriles, 5,5-dialkyl-4-pentenenitriles and 5,5-dialkyl-2,4-pentadienenitriles.     

Catalytic reaction of methane with carbon dioxide

High activities and selectivities of Ni on SiO₂ catalysts producing CO in the reaction of CH₄ with CO₂, have been obtained at relatively low temperatures. These aspects are considerably different from the activities or selectivities of other catalysts, and have been explained by assuming that the Ni on SiO₂ catalyst markedly suppresses carbon deposition.

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CO Ni SiO₂ CH₄ CO₂. , Ni SiO₂.

     

Catalytic reactions of hydrocarbon with carbon dioxide over metallic catalysts

The catalytic reaction between hydrocarbons and carbon dioxide, e.g. CH₄+ +CO₂2CO+2H₂ and C₆H₆CH₃+CO₂C₆H₆+2CO+H₂, has been investigated over various metallic catalysts under atmospheric pressure. In general, Rh–Al₂O₃ catalyst was found to be excellent in activity and selectivity. The reaction rates were moderately dependent on the pressure of carbon dioxide, whereas it was little influenced by the pressure of hydrocarbon.

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, ., CH₄+CO₂2CO+2H₂ C₆H₅CH₃+CO₂C₆H₆+2CO+X₂, . , Rh–Al₂O₃ . , .

     

Biomethylation of Arsenic in an Arsenic-rich Freshwater Environment

Arsenic circulation in an arsenic-rich freshwater ecosystem was elucidated to detect arsenic species in the river water and in biological samples living in the freshwater environment. Water-soluble arsenic compounds in biological samples were extracted with 70% methanol. Samples containing arsenic compounds in the extracts were treated with 2 mol dm³ of sodium hydroxide and reduced with sodium borohydride. The detection of arsenic species was accomplished using a hydride generation/cold trap/cryofocus/gas chromatography-mass spectrometry (HG/CT/CF/GC-MS) system. The major arsenic species in the river water, freshwater algae and fish are inorganic arsenic, dimethylarsenic and trimethylarsenic compounds, respectively. Trimethylarsenic compounds are also detected in aquatic macro-invertebrates. The freshwater unicellular alga Chlorella vulgaris, in a growth medium containing arsenate, accumulated arsenic and converted it to a dimethylarsenic compound. The water flea Daphnia magna, which was fed on arsenic-containing algae, converted it to a trimethylarsenic species. © 1997 by John Wiley & Sons, Ltd.     

Comparison of catalytic activity and efficiency of hydrogen peroxide utilization for di-iron-containing silicotungstate with those for iron containing complexes and the oxidation of methane and ethane

The Keggin-type di-iron-substituted γ-SiW₁₀{Fe(OH₂)}₂O₃₈ ^6- showed high efficiency of hydrogen peroxide utilization for the oxidation of cyclohexane. The efficiency and catalytic activity greatly depended on the structures of the iron centers. Such a structure dependency of the catalysis is significant and the remarkable catalytic performance of di-iron-substituted polyoxometalate may be related to the catalysis by methane monooxygenase. Not only cyclohexane but also cyclooctane, n-hexane, n-pentane, and adamantane were catalytically oxygenated with high efficiency of hydrogen peroxide utilization. Even methane and ethane were oxidized. It was also demonstrated that the potassium salt of γ-SiW₁₀{Fe(OH₂)}₂O₃₈ ^6- oxidized methane in water.     

Effective reduction of critical current for current-induced magnetization switching by a Ru layer insertion in an exchange-biased spin valve

Recently, it has been predicted that a spin-polarized electrical current perpendicular to plane directly flowing through a magnetic element can induce magnetization switching through spin-momentum transfer. In this Letter, the first observation of current-induced magnetization switching (CIMS) in exchange-biased spin valves (ESPVs) at room temperature is reported. The ESPVs show the CIMS behavior under a sweeping dc current with a very high critical current density. It is demonstrated that a thin ruthenium (Ru) layer inserted between a free layer and a top electrode effectively reduces the critical current densities for the CIMS. An "inverse" CIMS behavior is also observed when the thickness of the free layer increases.