The formation of a series of barium tungsten bronzes

The phases occurring in samples of gross composition Ba_xWO₃ (0.01 < x < 0.33) heated at temperatures between 1073 and 1373°K have been determined using X-ray diffraction and electron microscopy. At all temperatures a tetragonal tungsten bronze phase with a narrow homogeneity range of x = 0.20?0.21 was observed to form. In addition, at temperatures up to 1273°K, a series of orthorhombic intergrowth bronzes forms within a restricted composition range around x = 0.04. The latter phases are unstable at higher temperatures and were not found in preparations made at 1323°K. Similarly a new type of bronze phase forms at x = 0.14?0.16 at temperatures up to 1323°K, but not at 1373°K. The structure of this phase is unknown. Aspects of the crystal chemistry of the barium bronzes and the relationships to other bronze phases are discussed.     

Synthesis and properties of bis(heteroazulen-3-yl)methyl cations and bis(heteroazulen-3-yl)ketones

The synthesis and properties of a novel type of bis(heteroazulen-3-yl)methyl cations, bis(2-oxo-2H-cyclohepta[b]furan-3-yl)methyl cation salt and nitrogen analogues, (9a-c·PF₆⁻) and (9a-c·BF₄⁻), as well as bis(heteroazulen-3-yl)ketones (12a-d) are studied. The synthetic method was based on a TFA-catalyzed electrophilic aromatic substitution on the heteroazulenes (6a-d) with paraformaldehyde to afford the corresponding disubstituted methane derivatives 7a-d, followed by oxidative hydrogen abstraction with DDQ, and subsequent exchange of the counter-anion by using aq. HPF₆ or aq. HBF₄. In addition, the reaction of 7a-d with 2.2 equiv. amounts of DDQ afforded carbonyl compounds 12a-d. The delocalization of the positive charge of 9a-c was evaluated by the ¹H and ¹³C NMR spectral data. The thermodynamic stability of cations 9a-c was evaluated to be in the order 9a<9b<9c on the basis of their reduction potentials measured by cyclic voltammetry (CV) and pK_R+ values (2.6-10.3) obtained spectrophotometrically. The reduction waves of cations 9a-c were irreversible, suggesting the dimerization of the radical species generated by one-electron reduction. This was demonstrated by the reduction of 9a·BF₄⁻ with Zn powder to give dimerized product 14a. In addition, the quenching of 9a·BF₄⁻ with MeOH/NaHCO₃ gives ether derivative 15a, which is proposed for the precursor for synthesizing tris(heteroazulene)-substituted methyl cations bearing two different heteroazulene-units.     

Infrared investigation of aluminum- and chromium-substituted magnetites and of the lacunar spinels resulting from their oxidation

When Fe³⁺ ions are substituted by aluminum or chromium on magnetite octahedral sites, the ir spectrum shows the conversion of an inverse spinel to a normal spinel. Both broad bands of magnetite are gradually replaced by the four characteristic bands of normal spinels II–III. They are also observed for solid solutions, FeCr₂O₄FeAl₂O₄, with, however, a further band at 780 cm^?1 which may be assigned to Al³⁺ ions on tetrahedral sites. Low-temperature (<400°C) oxidation of these compounds whose sizes are less than 2000 Å results in lacunar spinels III–III. The ir spectrum of these solids is characterized by two absorption bands (as for inverse spinels II–III) except for compounds close to pure γFe₂O₃ in which an order of vacancies could be put in evidence.     

Tautomerism in monothio-β-diketones studied by PMR and quantum chemical calculations

It is shown by proton NMR and quantum chemical PCILO calculations that monothio-β-ketones

in solution exist as different isomers depending on substituents, solvent and temperature. In solvents with low dielectric constants the hydrogen-bridged cis enol form predominates, and is in fast equilibrium (in the NMR scale) with nonchelated trans enol forms down to ?100°C at least. Transition enthalpies are of the order of 7–15 kJ mol^?1. In compounds with R₂ = Me the rotation of the Me -CS group around the neighbouring C-C- bond can be detected and the thermodynamic and kinetic parameters estimated. The reason for the slowing down of this rotation, inferred from the line broadening in NMR, is probably the stabilization of a trans isomer by interaction between the protons of the methyl group and the lone pairs of the oxygen atom. There are no indications for the presence of chelated and non-chelated enethiol isomers from the PMR studies and quantum chemical calculations performed.     

Constituents from Rubia Ustulata Diels and R. Yunnanensis Diels and Their Antiplatelet Aggregation Activity

A new anthraquinone glycoside, rubiayannone‐A ( 1 ), and a new coumarin, rubilatin‐A ( 2 ), together with twenty‐two known compounds were isolated and characterized from the roots of Rubia ustulata. A new anthraquinone, 2‐carbomethoxyanthraquinone ( 3 ), and rubiayannone‐A, 2‐formylanthraquinone were obtained from the roots of R. yunnanensis. The structures of those compounds were elucidated by spectroscopic methods. The antiplatelet aggregation activity of the isolated compounds 1, 4～6 were also discussed.     

POLYBINAPHTHYLS INCORPORATING (R)-2,2''''-BINAPHTHO-20-CROWN-6 AND NAPHTHYL MOITIES

Chiral polymer was synthesized by the polymerization of (R)-6,6'-bistributylstannyl-2,2'-binaphtho-20-crown-6 (M-1) with 1,4-dibromo-2,3-bisbutoxy-naphthyl (M-2) by Pd(PPh3)4 catalyzed Stille coupling reaction. Both monomer and polymer were analyzed by NMR, MS, FT-IR, UV, polarimetry, DSC-TGA, CD, fluorescent spectroscopy and GPC. The major difference between monomer and polymer is that a long wavelength Cotton Effect was observed for the polymer due to its more extended conjugation in the repeating unit and a highly rigid backbone in the polymer chain. Polymer has strong blue fluorescence due to the efficient energy migration from the extended n-electronic structure of the repeating unit of the polymer to the chiral binaphthyl core and is expected to have potential application in the materials of fluorescent sensors and chiral chromatographic packing for resolution of racemic amino acid.     

Asymmetric Reduction Using Lithium Aluminum Hydride Modified with Chiral Ligands Prepared from (1R)-(-)-β-Pinene

The reduction of prochiral ketones using chiral reducing reagents, prepared from lithium aluminum hydride and (-)-(1R, 2S, 3S, 5R)-10-anilinopinanediol (5) and (-)-(1R, 2S, 3S, 5R)-10-N-methylanilinopinanediol (6), affords chiral secondary alcohols in useful chemical yields (70 ～ 93%) but in low optical purity (8 ～ 33% ee). Modifiers 5 and 6 are synthesized from (lR)-(-)-β-pinene in three steps.     

(S)-和(R)-普萘洛尔的不对称合成

普萘洛尔是一种临床上广泛使用的β受体阻断剂, 介绍了一种不对称合成(S)-和(R)-普萘洛尔的方法. 以手性Salen-Co^III催化剂水解动力学拆分外消旋环氧氯丙烷得到高光学纯度的(S)-环氧氯丙烷和(R)-3-氯-1,2-丙二醇, 以(S)-环氧氯丙烷为手性原料先水解得(S)-3-氯-1,2-丙二醇, 其与1-萘酚反应得(S)-3-(1-萘基)-丙烷-1,2-二醇, 再与氯化亚砜反应得环状亚硫酸酯, 最后和异丙胺作用得(S)-普萘洛尔, 总收率80.9%, 光学纯度大于99%; 而同样以(S)-环氧氯丙烷为手性原料直接与1-萘酚反应得(2R)-3-(1-萘氧基)-1,2-环氧丙烷, 再与异丙胺作用得(R)-普萘洛尔, 总收率74.5%, 光学纯度大于99%.     

The circular chemistry conceptual framework: A way forward to sustainability in industry 4.0

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Rapid and sensitive determination of protein by light-scattering technique with Eriochrome Blue Black R

Based on the interaction between Eriochrome Blue Black R (EBBR) and proteins, which causes a strong light-scattering signal with the maximum scattering peak located at 398 nm, a simple, rapid, sensitive and selective method is developed for the determination of proteins by the light-scattering technique using a common spectrofluoremeter. Under proper experimental conditions, the protein determination can be performed in the range of 0.1-25, 0.1-20 and 0.25-25 μg ml⁻¹ for bovine serum albumin (BSA), human serum albumin (HSA) and human immunoglobulin G (IgG), respectively. The detection limit, calculated as 3 times the S.D. of nine blank measurements, are 33 μg l⁻¹ for BSA, 25 μg l⁻¹ for HSA and 38 μg l⁻¹ for IgG. Moreover, there is no significant difference among the scattering signals yielded by HSA, IgG and BSA, and almost no interference of many amino acids and metal ions. The method has been satisfactorily applied to the direct determination of the total protein in human serum, saliva and urine samples. The results obtained from the studies on the binding characteristics of EBBR to BSA indicated that an electrostatic force existed in the binding system, and the binding constant (K) and the number of the binding sites (n) at 25 °C are 1.69×10⁵ l mol⁻¹ and 0.946, respectively.