Negishi偶联反应的研究进展

对有机锌试剂参与的Negishi偶联反应机理进行了简要概述,并详细综述了Negishi偶联反应的研究进展,主要介绍了Pd、Ni催化剂以及新型Fe、Co催化剂参与的Negishi偶联反应。展望了新型催化剂的发展趋势。     

Frontispiz: Mild and Versatile Nitrate‐Promoted C?H Bond Fluorination

A novel and facile C H bond fluorination proceeds under remarkably mild conditions (close to room temperature in most cases). Both aromatic and olefinic C(sp²) H bonds with a wide range of electronic properties are selectively fluorinated in the presence of a catalytic amount of simple, cheap, and nontoxic nitrate as the promoter. A Pd^II/Pd^IV catalytic cycle that is initiated by an in situ generated cationic [Pd(NO₃)]⁺ species was proposed based on preliminary mechanistic studies.     

Interface structure and misfit relaxation in YBa2Cu3O7‐δ/PrBa2Cu3O7‐δ heterostructures on SrTiO3(001) substrates

Structural properties of YBa₂Cu₃O_7‐δ/PrBa₂Cu₃O_7‐δ heterointerfaces have been investigated by aberration‐corrected electron microscopy. Experimental evidence shows that c‐axis‐oriented YBa₂Cu₃O_7‐δ/PrBa₂Cu₃O_7‐δ heterostructures with atomically sharp interface epitaxially grow on SrTiO₃(001) substrates. In terms of the contrast analysis, no apparent interdiffusion between YBa₂Cu₃O_7‐δ and PrBa₂Cu₃O_7‐δ occurs at the interface. In addition, stand‐off misfit dislocations and planar faults appear within PrBa₂Cu₃O_7‐δ layer near the interface. Both misfit dislocations and interfacial dislocations resulting from the termination of planar faults contribute to misfit relaxation at the YBa₂Cu₃O_7‐δ/PrBa₂Cu₃O_7‐δ interface. The defect configuration of planar faults and stand‐off misfit dislocations is explored. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of six polyynes in Oplopanax horridus and Oplopanax elatus using polyethylene glycol modified reversed migration microemulsion electrokinetic chromatography

A PEG‐modified reversed migration MEEKC method was developed for simultaneous determination of six polyynes, including oplopandiol, falcarindiol, oplopandiol acetate, (11S, 16S, 9Z)‐9,17‐octadecadiene‐12,14‐diyne‐1,11,16‐triol,1‐acetate, oplopantriol B, and oplopantriol A, in Oplopanax horridus and Oplopanax elatus. The running buffer containing 0.8% v/v ethyl acetate, 3.8% w/v SDS, 6.6% v/v n‐butanol in 20 mM phosphate buffer (pH 2.5), followed by mixing with propan‐2‐ol at 30% v/v and PEG‐1000 at 15% w/v, was applied in the analysis. The proposed method was successfully applied to determine the six polyynes in five samples of Oplopanax horridus and one of O. elatus. The result showed that the types and amounts of polyynes present were obviously different when comparing the two herbs. Besides, the developed PEG‐modified reversed MEEKC method might be suitable for the analysis of hydrophobic analytes in herbal medicines.     

Thermal-Induced Dimerization Cyclization of Ethyl N-(Styrylcarbamoyl)acetates: Formation of 4-Hydroxy-2(1H)-pyridone-3- carboxamide Derivatives

Thermal-induced dimerization cyclization of ethyl N-(styrylcarbamoyl)acetate derivatives has been investigated, leading to 4-hydroxy-2(1H)-pyridone-3-carboxamide derivatives with good yields in diphenyl ether on 200–210 °C. Ethyl N-(styrylcarbamoyl)acetate derivatives readily provided the intermolecular cyclization products 4-hydroxy-2(1H)-pyridone-3-carboxylates on reflux in xylene. In addition, several related 3-acetyl-4-hydroxy-5-phenylpyridin-2(1H)-ones have been prepared. It provided an efficient preparation of 4-hydroxy-2(1H)-pyridone-3-carboxamide derivatives.     

Synthesis and characterization of π-extended thienoacenes with up to 13 fused aromatic rings

π-Extended thienoacenes that comprise alternatively arranged anthracene and thieno[3,2-b]thiophene moieties and have 8 or 13 aromatic rings were synthesized. The delocalization of their HOMO and LUMO orbitals is over the entire molecules, and low-lying HOMO levels endow them good stability.     

Rapid analysis of phthalic acid esters in environmental water using fast elution gas chromatography with mass spectrometry and adaptive library spectra

A method for the fast determination of the components in a complex sample by using gas chromatography with mass spectrometry was developed and used for the quantitative analysis of phthalic acid esters in environmental water. In the method, the adaptively corrected mass spectra were used to compensate for the differences between the library spectra and the measured ones in the experiment. The correction was obtained by the iterative transformation of the library spectra using iterative target transformation factor analysis, and the resolution was performed by non‐negative immune algorithm using the corrected spectra. Rapid analysis of 16 phthalic acid esters in water samples was achieved using fast elution gas chromatography with mass spectrometry measurements. The results show that the mass spectra and chromatographic profiles of the phthalic acid esters can be obtained from the overlapping signal of 13 min elution, and accurate quantitative analysis can be obtained. The recoveries of the phthalic acid esters obtained by standard addition are between 90.3 and 107.4%, and the relative standard deviations obtained in repeated measurements are less than 9%.     

Nitrogen-doped graphene as an excellent candidate for selective gas sensing

The toxic gases,such as CO and NO,are highly dangerous to human health and even cause the death of person and animals in a tiny amount.Therefore,it is very necessary to develop the toxic gas sensors that can instantly monitor these gases.In this work,we have used the first-principles calculations to investigate adsorption of gases on defective graphene nanosheets to seek a suitable material for CO sensing.Result indicates that the vancancy graphene can not selectivly sense CO from air,because O2 in air would disturb the sensing signals of graphene for CO,while the nitrogen-doped graphene is an excellent candidate for selectivly sensing CO from air,because only CO can be chemisorbed on the pyridinic-like N-doped graphene accompanying with a large charge transfer,which can serve as a useful electronic signal for CO sensing.Even in the environment with NO,the N-doped graphene can also detect CO selectively.Therefore,the N-doped graphene is an excellent material for selectively sensing CO,which provides useful information for the design and fabrication of the CO sensors.     

Simultaneous removal of uranium and humic acid by cyclodextrin modified graphene oxide nanosheets

Cyclodextrin-modified graphene oxide nanosheets (denoted as CD/GO) were synthesized by an in-situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and potentiometric acid-base titration. The characterization results indicated that CD was successfully grafted onto GO surfaces by forming a chemical bond. Mutual effects on the simultaneous removal of hexavalent uranium and humic acid by CD/GO from aqueous solution were investigated. The results indicated that U(VI) and humic acid (HA) sorption on CD/GO were greatly affected by pH and ionic strength. The presence of HA enhanced U(VI) sorption at low pH and reduced U(VI) sorption at high pH, whereas the presence of U(VI) enhanced HA sorption. The surface adsorbed HA acted as a “bridge” between U(VI) and CD/GO, and formed strong inner-sphere surface complexes with U(VI). Sorption isotherms of U(VI) or HA on CD/GO could be well fitted by the Langmuir model. This work highlights that CD/GO can be used as a promising material in the enrichment of U(VI) and HA from wastewater in U(VI) and humic substances obtained by environmental pollution cleanup.