Vinyl triflates derived from 1,3-dicarbonyl compounds and analogs: access and applications to organic synthesis

This review details the current methods used to prepare vinyl triflates derived from 1,3-dicarbonyl compounds and describes the reactivity of such functionalized vinyl triflates. α-Ketovinyl triflates can easily and stereoselectively be produced through three different ways. Enolization and triflation is the most common route, but direct triflation with triflic anhydride could also be used, each involving different mechanisms. Direct addition of triflic acid and related sulfonic acids to triple bond offers an alternative to the previous methods. With their peculiar set of functional groups, α-ketovinyl triflates can react in four different ways. The vinyl triflate part could be engaged in coupling reactions, while the carbonyl group as well as the enone motif could be subjected to nucleophilic additions. If a proton is available next to the triflate group, eliminations could occur under basic conditions. Upon addition, fragmentations could also be possible.     

生物质热解液化与美拉德反应

对生物质热解液化和美拉德反应进行了介绍,指出美拉德反应不仅存在于生物质热解液化过程中,而且通过引入适量氨等调控措施,可以促进美拉德反应有选择性地生成吡嗪类杂环化合物等高值化学品,然后再通过分级冷凝将生物油分为化工生物油和燃料生物油,前者用于分离提取高值化学品,后者用于锅炉和窑炉的燃料.引入美拉德反应后,生物质热解液化技术经济性将会得到根本性的改善.     

Surface Modification Based on Diselenide Dynamic Chemistry: Towards Liquid Motion and Surface Bioconjugation

Surface modification is an important technique in fields, such as, self‐cleaning, surface patterning, sensing, and detection. The diselenide bond was shown to be a dynamic covalent bond that can undergo a diselenide metathesis reaction simply under visible light irradiation. Herein we develop this diselenide dynamic chemistry into a versatile surface modification method with a fast response and reversibility. The diselenide bond could be modified onto various substrates, such as, PDMS, quartz, and ITO conductive film glass. Different functional diselenide molecules could then be immobilized onto the surface via diselenide metathesis reaction. We demonstrated that by using this modification method we could achieve liquid motion in a capillary tube under light illumination. We also show that this approach has the potential to serve as an efficient modification method for surface bioconjugation, which has practical applications in clinical usage.     

Effect of hydrophilic substances in spruce TMP resin on its physico-chemical characterization and deposition tendency

The viscosity, wettability and deposition tendency of spruce thermomechanical pulp resin extracted with hexane, acetone and hexane–acetone (9:1, v/v) were studied in this paper. Some hydrophilic substances such as sugars and lignans could be extracted by some hydrophilic solvents, and the effect of the hydrophilic substances on physico-chemical properties is still not well known. The results showed that hydrophilic substances such as lignans and sugars present in spruce thermomechanical pulp resin had a great effect on resin physico-chemical properties. About 19% sugars and 14% lignans were identified in the acetone extracts, which could increase resin viscosity greatly. Only a little of lignans and sugars could be extracted by hexane–acetone, but these sugars and lignans could increase resin hydrophilicity evidently, leading to the decrease in contact angles with water and the increase in the acid–base component of work of adhesion. During preparation of resin dispersions, however, these sugars and lignans dissolved in dispersions could pass through the pores of the dialysis tube into water system which would cause an unexpected deposition result of the acetone-extracted resin dispersion. Resin extracted with hexane can be regarded as a relative ideal resin model in evaluating resin deposition tendency.     

Reversible light-driven structural changes between the mono- and bilayer stacking alignments in 4-octadecyloxystilbazolium arylcarboxylate films

The present investigation deals with the light-driven morphological changes in multilamella films of N-methyl-4-octadecyloxystilbazolium arylcarboxylates (C18OStz+X-) cast on glass slides. The results of XRD analysis show a photostimulated layer expansion and shrinkage of the stacked thin films along the c-axis under alternative illumination at >350 and 254 nm, respectively. It was revealed that such lamellar changes could be switched either way by a reversible transformation between the mono- and bilayer units in these stacked multilamella films. Moreover, such controlled structural adjustments in the alignment could be initiated by the photocyclodimerization of the stilbazolium moieties of the arylcarboxylate salts; i.e., a monolayer-to-bilayer transformation could be induced at a stage of only 10% cyclodimer formation. The photoinduced patterning on the surface of the films was also analyzed by SEM and fluorescence microscopic investigations.     

Generally applicable and efficient oxidative Heck reaction of arylboronic acids with olefins catalyzed by cyclopalladated ferrocenylimine under base- and ligand-free conditions

A mild and efficient method for oxidative Heck-type reaction of arylboronic acids with olefins catalyzed by cyclopalladated ferrocenylimine was developed. The results represent the first examples involving the palladacycle as the catalyst for such couplings. Moreover, the catalytic system could tolerate various functional groups, such as F, Cl, Br, NO₂ and CH₃O, and the substrates could be extended to a wide range of olefins from acrylic esters, α,β-unsaturated ketones to alkenes. Furthermore, the olefination could proceed well under base- and ligand-free conditions and employ oxygen as the environmentally benign oxidant.     

纳米金属铜与纳米氧化锌之间相互作用的EPR和XPS研究

由于纳米材料独特的表面效应、电子效应及量子尺寸效应 ,已被广泛应用于各个领域 .有关纳米材料研究的报道很多 [1～ 7] ,大部分是关于纳米材料的制备[1～ 4 ] 及其特性研究 .对于纳米金属及纳米氧化物之间相互作用的研究迄今尚未见报道 .本文采用超声分散和机械研磨法物理混合纳米金属铜粉和纳米氧化锌 ,借助 EPR和 XPS技术对样品进行了表征 ,发现混合体系出现了 Cu2 + 的顺磁信号 ,Zn L3M4 5M4 5俄歇动能和 O1s的电子结合能亦发生了变化 ,表明纳米 Cu0 和纳米 Zn O之间存在相互作用 ,作用形式为 Cu— O—Zn.1　实验部分1 .1　样品…     

Reversing Chemoselectivity: Simultaneous Positive and Negative Catalysis by Chemically Equivalent Rims of a Cucurbit[7]uril Host

Enzyme catalysis has always been an inspiration and an unattainable goal for chemists due to features such as high specificity, selectivity, and efficiency. Here, we disclose a feature neither common in enzymes nor ever described for enzyme mimics, but one that could prove crucial for the catalytic performance of the latter, namely the ability to catalyze and inhibit two different reactions at the same time. Remarkably, this can be realized by two identical, spatially resolved catalytic sites. In the future, such a synchronized catalyst action could be used not only for controlling chemoselectivity, as in the present case, but also for regulating other types of chemical reactivity.     

Application of APCD/DIBK extraction system in strongly acidic media: Determination of traces of copper and nickel in titanium metals by extraction-flame atomic-absorption spectrometry

Extraction of nickel in strongly acidic solution (0.01 approximately 8M hydrochloric acid) with ammonium 1-pyrrolidinecarbodithioate (APCD) into di-isobutyl ketone (DIBK) has been studied, and the APCD/DIBK system has been applied to simultaneous extraction and flame atomic-absorption spectrometric determination of trace amounts of copper and nickel in titanium metal. Nickel could be extracted with copper from strongly acidic solution such as up to 5M hydrochloric acid with APCD/DIBK system. The extraction from such a strongly acidic media made it possible to extract nickel with copper, since it did not require the addition of a large amount of the masking agent which prevents the hydrolysis of the matrix titanium and also prevents the extraction of nickel. Thus, they could be extracted directly from the titanium metal sample digested by concentrated hydrochloric acid with a small amount of tetrafluorohydroboric acid. Effect of coexistence of a large amount (at least 0.2 g) of iron on the extraction of both elements could be prevented by keeping most of the matrix titanium as Ti(III). With the method described here, mug/g levels of copper and nickel in titanium metal could be rapidly determined with good precision and accuracy.     

Thermal analysis/mass spectrometry using soft photo-ionisation for the investigation of biomass and mineral oils

The combined analytical methods of thermal analysis and mass spectrometry have been applied in form of a newly developed prototype of a thermogravimetry — single photon ionisation time-of-flight mass spectrometer coupling (TG-SPI-TOFMS) to investigate the molecular patterns of evolved gases from several biomass samples as well as a crude oil sample. Single photon ionization (SPI) was conducted by means of a novel electron beam pumped argon excimer lamp (EBEL) as photon source. With SPI-TOFMS various lignin decomposition products such as guaiacol, syringol and coniferyl alcohol could be monitored. Furthermore, SPI allows the detection of aliphatic hydrocarbons, mainly alkenes, carbonylic compounds such as acetone, and furan derivatives such as furfuryl alcohol and hydroxymethylfurfural. More alkaline biomass such as coarse colza meal show intense signals from nitrogen containing substances such as (iso-)propylamine and pyrrole. Thermal degradation of crude oil takes place in two steps, evaporation of volatile components and pyrolysis of larger molecular structures at higher temperatures. Due to the soft ionisation, homologue rows of alkanes and alkenes could be detected on basis of their molecular ions. The obtained information from the thermal analysis/photo ionisation mass spectrometry experiments can be drawn on in comparison to the investigation of the primary products from flash pyrolysis of biomass for production of biofuels and chemicals.     

A Study on the Phosphorylation of Indole,Imidazole, Carbazole,and Phenothiazine Derivatives

Abstract

N-Heterocycles including indolecarbaldehyde, substituted benzimidazoles, and methylimidazole could be efficiently phosphorylated by diethyl chlorophosphate at room temperature in different solvents using alkali carbonate or triethylamine as the base. However, the phosphorylation of N-heterocycles with a lower reactivity at the NH function, such as carbazole and phenothiazine, could not be conducted to complete conversion under the conditions applied.     

High-performance liquid chromatography of oligosaccharide alditols and glycopeptides on a graphitized carbon column.

The chromatographic behaviour of oligosaccharide alditols and glycopeptides containing neutral and acetamido sugars and sialic acid has been investigated on a HyperCarb porous graphitised carbon column. The alditols were substantially retained and could be eluted in 0-25% acetonitrile-0.05% trifluoroacetic acid in 0.05% aqueous trifluoroacetic acid between 3-30 min for mono- to hexasaccharides. Elution patterns were based on both size, charge and linkage such that isomeric compounds could be separated from each other.     

Separation properties of high temperature reverse osmosis membranes for silica removal and boric acid recovery

The separation system containing thin-film polyamide reverse osmosis membrane (tf-PA RO) of high temperature was studied.In performed laboratory tests, RO silica rejection percentage was over 97%, and boron passage was about 60–65% (molecular weight cut off of 200 or 250 Da) of the solution which contained silica in the range of 1–90 ppm and boron in the range of 7500–15,000 ppm. The separation factor (SF) between boron and silica related to boron concentration could be expressed as the relation, SF = k[boron]^0.7. The separation process could be described by a mass balance model. The modeling calculation fitted the experimental results very well, within the acceptable parameters’ errors. It was proposed that the boric acid in a boric acid storage tank (BAST) of one studied pressurized water reactor (PWR) plant could be treated with such tf-PA RO. In the prediction, the silica concentration in it would be removed to about 1 ppm, and that the boron could be reused. The waste amount of boron after such treatment was predicted to be less than 1.5%.     

Formation and degradation of poly(D,L-lactide) nanoparticles and their potential application as controllable releasing devices

In the presence of surfactant, water-insoluble poly(D,L-lactide) (PLA) was dispersed into narrowly distributed nanoparticles stable in water via microphase inversion. The structure and degradation of such formed nanoparticles were investigated by a combination of static and dynamic laser light scattering. Our results revealed that the degradation rate increased with the temperature and pH so that the degradation could be regulated from minutes to days. Using anionic sodium dodecyl sulfate (SDS) as stabilizer resulted in a slower degradation than using cationic hexadecyltrimethylammonium bromide (HTAB). The phthalocyanine chromophores (PC) could be encapsulated inside these PLA nanoparticles. The degradation of individual PLA nanoparticles led to a controllable releasing of PC. The absorption and fluorescence studies revealed a correlation between the degradation and the releasing of PC. Our results showed that a higher PC/PLA ratio could lead to a faster degradation.     

Interfacial assemblies of cyanine dyes and gemini amphiphiles with rigid spacers: regulation and interconversion of the aggregates

A series of gemini amphiphiles with a pyridinium headgroup and rigid spacers were designed, and their interfacial assemblies with cyanine dyes, 3,3-disulfopropyl-9-methyl-selenacarbocyanine (SeCy) and 3,3-disulfopropyl-4,5,4',5'-dibenzo-9-methyl-thiocarbocyanine (MTC), through the air/water interface were investigated. Although the dyes have intrinsic tendencies to form J- or H-aggregates in aqueous solutions, their aggregation could be regulated in the complex films. Depending on the spacer, both J- and H-aggregates were formed for SeCy, whereas an H-aggregate with different absorption bands was obtained for MTC. Furthermore, the formed aggregates in the films could be reversibly switched by treating the complex films with HCl, NH3 gas, or water vapor. The J-aggregates of SeCy could be changed into H-aggregates and recovered through an alternative HCl/NH3 exposure in the films. The H-aggregate of the MTC film could be changed into J-aggregate upon exposure to HCl gas and subsequently put into air or NH 3 gas, and the thus-formed J-aggregate could be changed into H-aggregate under hot water vapor. In addition, such a reversible switch between different aggregates of MTC was only observed when the gemini amphiphiles with rigid spacers were applied. A possible explanation related to the protonation of the dye and the reorganizations in the film during the interconversion between different aggregates was proposed.     

Raman spectroscopic signature of blood and its potential application to forensic body fluid identification

Near-infrared (NIR) Raman spectroscopy was used to measure spectra of dried human blood samples from multiple donors. Two major questions addressed in this paper involve the influence of sample heterogeneity and potential Raman spectral variations that could arise between different donors of blood. Advanced statistical analysis of spectra obtained from multiple spots on dry samples showed that dry blood is chemically heterogeneous, and its Raman spectra could be presented very well as a linear combination of a fluorescent background and two Raman spectroscopic components that are dominated by hemoglobin and fibrin, respectively. Each sample Raman spectrum contains the same major peaks, but the relative contribution of the hemoglobin and fibrin components varies with the donor. Therefore, no single spectrum could adequately represent an experimental Raman spectrum of dry blood in a quantitative way, but rather the combination of hemoglobin and fibrin spectral components could be considered to be a spectroscopic signature for blood. This proof-of-concept approach shows the potential for Raman spectroscopy to be used in forensic analysis to identify an unknown substance such as blood.     

Promoting analytical quality control of trace-element data to be presented in international journals and reports

The analytical quality of published data on trace elements in food has previously been shown to be of a generally poor quality and, therefore, not always reliable. The responsibility for this problem is shared among authors, editors, reviewers, and publishers, and it is based on the lack of clear instructions, to all parties, on how quality should be safeguarded. This has been noted by CEN/TC 275/WG 10, which has started preliminary work on such a guideline. This paper describes the background and what such a guideline could be based on.     

Boronate‐Affinity Glycan‐Oriented Surface Imprinting: A New Strategy to Mimic Lectins for the Recognition of an Intact Glycoprotein and Its Characteristic Fragments

Lectins possess unique binding properties and are of particular value in molecular recognition. However, lectins suffer from several disadvantages, such as being hard to prepare and showing poor storage stability. Boronate‐affinity glycan‐oriented surface imprinting was developed as a new strategy for the preparation of lectin‐like molecularly imprinted polymers (MIPs). The prepared MIPs could specifically recognize an intact glycoprotein and its characteristic fragments, even within a complex sample matrix. Glycan‐imprinted MIPs could thus prove to be powerful tools for important applications such as proteomics, glycomics, and diagnostics.     

Simultaneous determination of oxygen and cadmium in cadmium and cadmium compounds

Cadmium and its compounds were analysed for oxygen and cadmium by a modification of the Schütze-Unterzaucher method. Oxygen in some compounds such as cadmium oxide, nitrate and sulphate could not be determined by the usual method. The method of adding carbon was employed for the determination of total oxygen. Total oxygen could be determined by the addition of 5 mg of carbon to a sample boat and heating at 950 degrees . The determination was also carried out by addition of naphthalene (2 mg). It was found that the cadmium powder and cadmium flake used contained ca. 1 and 0.15% oxygen, respectively. Oxygen and cadmium in cadmium and its compounds were simultaneously determined by the addition of 2 mg of naphthalene. Cadmium was determined colorimetrically by use of glyoxal-bis-(2-hydroxyanil). Oxygen and cadmium in the samples could be determined simultaneously with an average error of -0.02 and -0.22%, respectively.     

高分子负载贵金属类催化剂及其在有机反应中的最新应用

高分子负载金属催化剂与传统的均相催化剂相比,具有较高的催化活性、立体选择性、较好的稳定性和重复使用性能,并且后处理简单,在反应完成后可方便地借助固-液分离方法将高分子催化剂与反应体系中其他组分分离、再生和重复使用,可降低成本和减少环境污染。本文综述了近五年来高分子负载贵金属类催化剂在有机反应中的最新应用,根据金属不同将其分为钌、钯、银、金四大类,并分类介绍了其在不同固相反应中的应用。本文介绍的负载贵金属类催化剂中的负载物均为不溶性聚合物,但不包括二氧化硅、可溶性聚合物和树枝状大分子等。