4-Hydroxy-2-quinolones 130. The reactivity of ethyl 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylates

The high reactivity of ethyl 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylates is governed by the simultaneous presence of the 4-OH and 2-C=O groups in the pyridine part of the molecule. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1503–1508, October, 2007.     

Importance of Inherent Substrate Reactivity in Enzyme‐Promoted Carbocation Cyclization/Rearrangements

The importance of inherent substrate reactivity for terpene synthase enzymes is discussed, with a focus on recent experimental tests of predictions derived from computations on gas‐phase reactivity of carbocations.     

电感耦合等离子体原子发射光谱（ICP-AES）法测定铁矿石中钒

建立了电感耦合等离子体原子发射光谱(ICP-AES)法测定铁矿石中钒含量的分析方法。采用盐酸、硝酸、氢氟酸、高氯酸分解试样,不溶物残渣碱熔融回收,稀盐酸溶解盐类的方式对样品进行分解。对仪器的主要工作参数和分析谱线进行了选择,讨论了基体和共存元素的干扰,以及溶解酸和熔剂等条件实验,确立了最佳分析条件。按实验方法对铁矿石标准样品和试样中钒量进行测定,测定值与标准值或其它方法的认定值基本一致,相对标准偏差RSD<6.5%。     

Modeling Heterogeneity in UO2 Nanoparticles Using X-ray Absorption Spectroscopy

EXAFS provides the capability to interrogate nanoparticle (NP) structure in atomistic detail without relying on long-range crystallinity. There is a limitation in that EXAFS provides averaged structural information, making it difficult to separate a small amount of heterogeneous structure from bulk. In this work, models were developed to extract surface-specific information from conventional EXAFS measurements collected on UO₂ NPs of varying size. Specifically, the surface terminating species of UO₂ NPs was determined from comparison of coordination numbers with geometric models while the origin of static disorder was interrogated from user-defined simulations. Results show that the degree of oxygenation on the NP surface does not significantly deviate from bulk surface and that static disorder is highly enhanced in NP surface layers but cannot be attributed to surface relaxation effects alone. The approach described herein has the potential to be adapted to a range of inorganic NP systems to interrogate surface structure.     

Stereoselective Synthesis of Alkyl Z -2-(2-Amino-4-oxo-1,3-thiazol-5(4 H )-yliden)Acetates in Solventless Conditions

Tiourea reacts with dialkyl acetylenedicarboxylates in solventless conditions to form 1:1 adducts, which undergo a cyclization reaction to produce alkyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetates in fairly good yields. The stereochemistry of the ethyl Z-2-(2-amino-4-oxo-1,3-thiazol-5(4H)-yliden)acetate was established by the use of X-ray single crystal structure analysis. The reaction is completely stereoselective.     

Physicochemical Properties of Plant Protection Substances: I Polymorphism and Binary Systems of Triadimenol

 The fungicide triadimenol consists of a mixture of two diastereoisomers. Diastereoisomer A (1RS,2SR) could be obtained from the mixture by fractionated crystallization from ethanol/water and toluene, successively, whereas diastereoisomer B (1RS,2RS) could be separated by column chromatography on a silica gel column using ethylacetate as eluent. Four different crystal forms of diastereoisomer A could be derived. The modifications were characterized by means of thermal analysis (thermomicroscopy, DSC), FTIR-spectroscopy, FT-Raman-spectroscopy and powder X-ray diffraction, as well as pycnometry. The thermodynamic relationships are illustrated in a semischematic energy/temperature-diagram which provides information about the relative thermodynamic stabilities and physical properties of the four crystal forms. Mod. II (m.p. 132 °C, ΔH_f 33.1±0.2 kJ mol⁻¹, density 1.271±0.001 g cm⁻³) was obtained from toluene after the separation of diastereoisomer A and is enantiotropically related to mod. I (m.p. 138 °C, ΔH_f 32.0 ± 0.2 kJ mol⁻¹, density 1.243±0.001 g cm⁻³). The transition point of mod. II with mod. I was determined between 30 and 40 °C, which means that mod. II is thermodynamically stable at ambient conditions. Mod. III (m.p. 112 °C, ΔH_f 25.1±0.5 kJ mol⁻¹) and mod. IV were obtained from the melt. Furthermore, the phase diagrams of the binary systems of diastereoisomer B and the four modifications of diastereoisomer A were calculated by means of the experimentally obtained thermodynamical data. Received September 30, 1999. Revision July 30, 2000.     

A NEW EFFICIENT SYNTHESIS OF TRIFLUOROACETYL HALIDES AND MIXED ANHYDRIDES OF PHOSPHORUS AND TRIFLUOROACETIC ACIDS

Abstract

Reaction of trifluoroacetic anhydride with chloroanhydrides of phosphorus acids R₂P(O)CI results in formation of mixed anhydrides R₂P(O) OCOCF₃ and trifluoroacetic acid halides CF₃COX (X=Cl, Br, I) in quantitative yield.     

Recent Developments in the Chemistry of Thiourea Oxides

Thiourea dioxide is one of the best known, important, and stable products of thiourea oxidation. This compound has long been considered as an effective reducing agent for many years. Traditional areas of its application include the textile and paper industries. In recent years, however, thiourea dioxides and trioxides have been widely used in new fields including organocatalytic, polymerization, and phase‐transfer reactions; reduction of graphene and graphite oxides; bitumen modifications; synthesis of guanidines and their derivatives; and studying nonlinear dynamical phenomena in chemical kinetics. The review gives a detailed survey of the latest developments and main trends in the chemistry and application of thiourea mon‐, di‐, and trioxides.     

Intramolecular 2H Group-Transfer (Dyotropic Rearrangements) in Alicyclic and Heterocyclic Bridged-Ring Systems

Examples of alicyclic frameworks containing a cyclohexa-1,3-diene ring as 2H donor held proximate to a variously-substituted acceptor Π-bond are compared for their reactivity in thermal 2H group-transfer reactions. Kinetic analysis reveals marked effects on rearrangement-rate as the acceptor Π-bond substieuents are varied. Attempted synthesis of exact structural analogues of these compounds but with a 2,3-diazacyclohexadiene component replacing the cyclohexadiene element [by (4 + 2)Π cycloadditions of 3,6-diaryl-1,2:4,5-tetrazines to dienophiles of the isodrin type] usually gives instead products of concomitant 2H group-transfer. These results are compared with the similar but generally slower 2H group-transfer rearrangement of pentacyclic 2-pyrazoline derivatives having relevant critical stereochemical features which result from 1,3-diarylnitrilioine (4 + 2)Π adductions with dipolarophiles of the isodrin type. Alkoxy and chlorine substitution of the acceptor Π-bond is rate-retarding for 2H group-transfer in both the alicyclic and heterocyclic representative systems examined, indicating truly pericyclic behaviour.     

Electronic effects in the reaction of diphenylcarbonyl oxide with aldehydes

The reactivity of 14 aldehydes with diphenylcarbonyl oxide Ph₂COO was characterized by thek ₃₃/k ₃₁ ratio. The values ofk ₃₃/k ₃₁ vary from 1.3·10⁻² (C₆F₅CHO) to 1.0 (p-Me₂N-PhCHO), 70 °C, acetonitrile as the solvent. A charge transfer complex (CTC) was suggested to be primarily formed during the reaction. The electronic effects of substituents in the reaction were analyzed using the published data. Carbonyl oxide reacts with aldehydes as a nucleophile (at the carbon atom of the −CHO fragment to form 1,2,4-trioxolane) and also as an electrophile (at the aromatic ring with the intermediate formation of CTC). The latter is transformed into either 1,2,4-trioxolane or the products of oxidation of the phenyl ring. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1090–1096, June, 1999.     

Electron Probe Microanalysis of HfO2 Thin Films on Conductive and Insulating Substrates

Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as low-voltage and/or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO₂ films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed. For comparison, Al₂O₃, Ta₂O₅ and TiO₂ films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized by atomic layer deposition method.     

Unknown thermal properties of ZnSb2O6 and Zn7Sb2O12 compounds

The investigations by XRD, DTA/TG and IR methods show that two compounds: ZnSb₂O₆ and Zn₇Sb₂O₁₂ are formed in the ZnO-α-Sb₂O₄ system in air. Oxygen contained in the air participates in the synthesis of these compounds. ZnSb₂O₆ was observed as an intermediate phase, during the Zn₇Sb₂O₁₂ synthesis. The temperature of the β→α-Zn₇Sb₂O₁₂ transition was fixed at 1225±10°C. The mechanisms of the reactions of ZnSb₂O₆ and Zn₇Sb₂O₁₂ thermal decomposition have been proposed. The IR studies of α and β-Zn₇Sb₂O₁₂ have initially indicated that the structures of both polymorphous forms differ in the reciprocal connection of the SbO₆ and ZnO₆ octahedra and the ZnO₄ tetrahedra.     

二氯二茂钛的二乙胺法合成、表征及其催化丁苯共聚物加氢的性能

在二乙胺的存在下,用混合溶剂合成,反应条件温和,合成操作安全可靠,收率达78.6%;洗涤产物滤饼时用甲醇代替盐酸,避免了酸性废水的产生与排放;用甲苯重结晶,晶形好、纯度高。并对二氯二茂钛进行加氢催化性能研究,确定反应温度为67-75℃,压力为2.0 MPa以上,催化剂用量为0.4 mmol/100 g聚合物时,反应2小时丁苯共聚物的加氢度达98%以上。     

Synthesis and structures of 1-[1-(4-R-benzoyl)-2-ethoxyvinyl]-2-dicyanomethylene-1,2-dihydropyridines

The reaction of (4-R-benzoyl)(2-bromopyridinitim) methylides with ethoxyrnethylene-rnalononitrile is stereoselective and affords Z-1-[1-(4-R-benzoyl)-2-ethoxyvinyl]-2-dicyationietliylene-1,2-dihydropyridines. The structure of 1-[1-(4-chlorobenzoyl)-2 ethoxyvinyll-2-dicyanomethylene-1,2-dihydropyridine has been established by X-ray structural study.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 434–436, February, 1996.     

基于ICP-MS及多元统计分析相结合的地黄酵素发酵前后无机元素特征

探讨地黄酵素制备前后无机元素的变化,分析发酵对地黄中无机元素的影响,为地黄酵素的制备开发提供数据支撑和理论依据。以四批不同来源的地黄为原料,利用乳酸菌和酵母菌发酵制备地黄酵素,采用微波消解-电感耦合等离子质谱(ICP-MS)法结合主成分分析、差异性分析和Pearson相关性分析等多元统计学方法对地黄酵素发酵前后样品中24种无机元素含量变化特征进行研究。结果表明,发酵对地黄原料中无机元素的种类没有影响,但对无机元素的含量影响较大,发酵前后24种无机元素的分类特征明显不同,其中发酵前后Na、P、Mn、Se、Sr和Cd 6种元素的含量差异在统计学上达到显著水平,而且地黄酵素发酵过程中各无机元素之间的代谢相互影响,其中Ca和Ti之间存在极显著的正相关关系,Pearson相关系数高达0.97;P和Mn, Ba和Pb存在显著的负相关关系,Pearson相关系数在-0.80以下。采用所建立的电感耦合等离子体质谱法测定中草药保健食品地黄酵素中的无机元素,并对地黄发酵制备地黄酵素前后的无机元素特征进行分析,可为地黄酵素在功能性食品添加剂方面的研究和地黄酵素的制备开发提供数据支撑,测定结果稳定可靠,能满足...     

Electrically Cooled SiLi Detectors for Application in X-Ray Equipment

The results of the development of electrically cooled SiLi detectors are presented for applications in X-ray equipment. The characteristics of such detectors compare well with those of the detectors cooled by liquid nitrogen, and to obtain these characteristics only 60 W of electric energy is needed instead of liquid nitrogen.     

Evaluation of Kinetic Data for Crystallization of Tio2 Prepared by Hydrolysis Method

The formation of TiO₂ prepared by hydrolysis method was presented. Thermodynamics and kinetics of anatase crystallization reaction were investigated. Differential method of kinetic data evaluation in non-isothermal conditions according toKissinger, Ozawa and Kazeev-Yerofeev was applied. Starting, crystallized and thermally treated powders were determined using X-ray powder diffraction analysis. The characteristic parameters (the activation energy, constant rate and formal kinetic order of reaction) of TiO₂ formation were calculated using DSC data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthese,Strukturen und Reaktivität von [(2,4,6-Ph3C6H2)Te(μ2-O)X]2 (X  Br und I)

Synthesis, Structures, and Reactivity of [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)X]₂ (X ? Br, I) [(2,4,6-Ph₃C₆H₂)Te]₂ reacts with iodine affording the aryltellurenic halide (2,4,6-Ph₃C₆H₂)TeI, which is oxidized by oxygen to yield [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂. It crystallizes with two molecules of dichloromethane in the monoclinic space group P2₁/c with a unit cell of the dimensions a = 911.3(4); b = 1153.3(2); c = 2244.1(9) pm; β = 93.53(2)°, Z = 2). The analogues bromo compound [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)Br]₂ is obtained by the reaction of [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂ with NH₄Br. It crystallizes with two molecules of xylene in the monoclinic space group P2₁/n (a = 1067.5(5); b = 1018.4(4); c = 2486.5(8) pm; β = 101.71(2)°; Z = 2). Both compounds are built up by two (2,4,6-Ph₃C₆H₂)TeX units (X ? Br, I) which are linked by two oxgen bridges to form centrosymmetric molecules. The Te? O? Te angles are 102°. Distinct Te? O bond lengths have been found (191.4(2) and 208.6(2) pm in [(2,4,6-Ph₃C₆H₂)Te(μ₂-O)I]₂ and 189.8(4)/208.4(5 pm in the bromo compound).     

Tetrakis(triphenylphosphine oxide) complexes of the lanthanide nitrates; synthesis, characterisation and crystal structures of [La(Ph3PO)4(NO3)3]·Me2CO and [Lu(Ph3PO)4(NO3)2]NO3

The reaction of Ln(NO₃)₃·6H₂O (Ln=La, Ce, Pr or Nd) with a sixfold excess of Ph₃PO in acetone formed [Ln(Ph₃PO)₄(NO₃)₃]·Me₂CO. The crystal structure of the La complex shows a nine-coordinate metal centre with four phosphine oxides, two bidentate and one monodentate nitrate groups, and PXRD studies show the same structure is present in the other three complexes. In CH₂Cl₂ or Me₂CO solutions, ³¹P NMR studies show that the complexes are essentially completely decomposed into [Ln(Ph₃PO)₃(NO₃)₃] and Ph₃PO. Similar reactions in ethanol gave [Ln(Ph₃PO)₃(NO₃)₃] only. In contrast for Ln=Sm, Eu or Gd, only the [Ln(Ph₃PO)₃(NO₃)₃] are formed from either acetone or ethanol solutions. For the later lanthanides Ln=Tb–Lu, acetone solutions of Ln(NO₃)₃·6H₂O and Ph₃PO gave [Ln(Ph₃PO)₃(NO₃)₃] only, even with a large excess of Ph₃PO, but from cold ethanol [Ln(Ph₃PO)₄(NO₃)₂]NO₃ (Ln=Tb, Ho–Lu) were obtained. The structure of [Lu(Ph₃PO)₄(NO₃)₂]NO₃ shows an eight-coordinate metal centre with four phosphine oxides and two bidentate nitrate groups. In solution in CH₂Cl₂ or Me₂CO the tetrakis-complexes show varying amounts of decomposition into mixtures of [Ln(Ph₃PO)₃(NO₃)₃], [Ln(Ph₃PO)₄(NO₃)₂]NO₃ and Ph₃PO as judged by ³¹P{¹H} NMR spectroscopy. The [Ln(Ph₃PO)₃(NO₃)₃] also partially decompose in solution for Ln=Dy–Lu, forming some tetrakis(phosphine oxide) species.