Oxygenative cleavage of catechols including protocatechuic acid with molecular oxygen in water catalysed by water-soluble non-heme iron(III) complexes in relevance to catechol dioxygenases

Catechol dioxygenase model oxygenations have been performed for the first time in water by using water-soluble nonheme iron(III) complexes, enabling the oxygenation of protocatechuic acid and other catechols.     

Reactions of zirconacyclopentadienes with C [double bond] ), C [double bond] N, and N [double bond] N moieties with electron-withdrawing groups: formation of six-membered heterocycles

Reactions of zirconacyclopentadienes with diethyl ketomalonate gave alpha-pyrans in excellent yields in the presence of BiCl3. In the absence of BiCl3, zirconacyclopentadienes did not react with diethyl ketomalonate. Tetraphenylzirconacyclopentadiene reacted with diethyl ketomalonate in the presence of BiCl3 to give a ring-opening product, dienolic ether, in 53% yield. The structures of the alpha-pyran prepared from diethyldiphenylzirconacyclopentadiene and the ring-opening product were determined by X-ray analysis. When oximinosulfonate was added to tetraethylzirconacyclopentadiene in THF at -78 degrees C, 3,4,5,6-tetraethylpyridine-2-carbonitrile was obtained in 95% yield within 10 min. The structure of the product was confirmed by X-ray analysis. When tetraethylzirconacyclopentadiene was treated with azodicarboxylate in the presence of 2 equiv of CuCl at -78 degrees C, 1,2-dialkoxycarbonyl-3,4,5,6-tetraethyl-1,2-dihydropyridazine derivatives were obtained. The structure of one of dihydropyridazine was also confirmed by X-ray analysis.     

One-pot isomerization of aldo-disaccharides to keto-disaccharides in deep sea water under sub-critical conditions

A novel and facile one-pot isomerization of aldo-disaccharides to keto-disaccharides is achieved by making use of deep sea water in sub-critical conditions. The resulting keto-disaccharides having pharmaceutical and food applications were obtained in modest yields of about 30–32% at the optimum reaction conditions (temperature: 180 °C, reaction time: 5 min). Detailed investigation of all major ions in deep sea water revealed that bicarbonate ions play a key role as a catalyst in this isomerization reaction.     

Finite‐field method with unbiased polarizable continuum model for evaluation of the second hyperpolarizability of an open‐shell singlet molecule in solvents

The static second hyperpolarizability γ of the complexes composed of open‐shell singlet 1,3‐dipole molecule involving a boron atom and a water molecule in aqueous phase are investigated by the finite‐field (FF) method combined with a standard polarized continuum model (PCM) and with a newly proposed unbiased PCM (UBPCM). On the basis of the comparison with the results calculated by the FF method using the full quantum and the quantum‐mechanical/molecular‐mechanical and molecular‐dynamics (QM/MM‐MD) treatments, the present FF‐UBPCM method is demonstrated to remedy the artificial overestimation of the γ caused by standard FF‐PCM calculations and to well reproduce the FF‐QM/MM‐MD and FF‐full‐QM results with much lower costs. © 2013 Wiley Periodicals, Inc.     

Synchrotron radiation studies of an expanded fluid alkali metal From the structure towards the electronic state

We have carried out x-ray diffraction and small-angle x-ray scattering measurements of expanded fluid alkali metal rubidium (Rb) and observed that the nearest neighbor distance decreases despite the fact that the average interatomic distance increases with volume expansion, indicating that the attractive force among ions is enhanced. Such structural change emerges in the density range where the fluid is still metallic. The density range also corresponds with the region where the instability of the electron gas has been theoretically predicted, suggesting the modulation in the charge fluctuations of the electron gas plays an essential role for such enhanced attraction among ions. Motivated by these unusual structural features, we have moved on investigating the electronic state in expanded fluid Rb through synchrotron-based high-resolution Compton scattering experiments. We have succeeded in measuring the Compton profile of fluid Rb using newly developed a high-pressure vessel for the Compton scattering experiments.     

Determination of arsenic by arsine generation with reducing tube followed by graphite furnace atomic absorption spectrometry

Summary A sensitive method for hydride generation and graphite tube furnace atomic absorption spectrometric measurements with a reducing tube has been developed for the determination of arsenic in tea and orchard leaves. Arsines were generated in a horizontal glass tube, in which a pellet of NaBH₄ was placed. 1.5–2.0 l/min of argon flow rate and 2,400° C of atomization temperature were the best experimental conditions. The strong supression of the arsenic signal by Ni and Co was effectively eliminated with 1,10-phenanthroline. A detection limit of 0.3 ng was obtained with a precision of 3–4%.Paper read at the Meeting of the Japan Society for Analytical Chemistry, June 1980     

Preparation of arsenic‐containing white rice grains as calibration standards for X‐ray fluorescence analysis of total arsenic in cereals

A preparation method of arsenic‐containing white rice grains as calibration standards was developed for the X‐ray fluorescence (XRF) analysis of arsenic in rice grains. Calibration standards were prepared by adding 10 g of white rice grains (from Japan) to 100 ml methanol‐containing dimethylarsinic acid corresponding to 2–100 µg arsenic. The mixture was heated, dried at 150 °C, cooled to room temperature, and then stored in a silica gel desiccator. A total of 5.0 g of each calibration standard was packed into a polyethylene cup (32 mm internal diameter and 23 mm height) covered with a 6‐µm‐thick polypropylene film and then analyzed by wavelength‐dispersive XRF spectrometry. The calibration curve for arsenic obtained from the white rice grains containing arsenic showed good linearity over a concentration range of 0.21–5.00 mg kg^?1 arsenic. The limit of detection of arsenic was 0.080 mg kg^?1. To check the reliability of the XRF method, the concentrations of arsenic in six samples of grain cereals and two samples of flour were compared with those obtained by atomic absorption spectrometry after acid decomposition. The values obtained by both analytical methods showed good agreement. Copyright © 2016 John Wiley & Sons, Ltd.