Dinuclear versus trinuclear complex formation in zinc(II) benzoate/pyridyl oxime chemistry depending on the position of the oxime group

The initial employment of pyridine-3-carbaldehyde oxime, (3-py)C(H)NOH, and pyridine-4-carbaldehyde oxime, (4-py)C(H)NOH, in zinc(II) carboxylate chemistry is reported. The syntheses, crystal structures and IR characterization are described for [Zn₃(O₂CPh)₆{(3-py)C(H)NOH}₂] (1) and [Zn₂(O₂CPh)₄{(4-py)C(H)NOH}₂] (2). The trinuclear molecule of 1 has a linear structure, with one monoatomically bridging η¹:η²:μ and two syn, syn-η¹:η¹:μ benzoate groups spanning each pair of Zn^II ions; the terminal metal ions are each capped by one (3-py)C(H)NOH ligand coordinating through its pyridyl nitrogen. Complex 2 exhibits a dinuclear paddle–wheel structure with a Zn···Zn distance of 2.990(2) Å; each Zn^II ion has a square pyramidal geometry with four carboxylate oxygens in the basal plane and the pyridyl nitrogen of one monodentate (4-py)C(H)NOH ligand at the apex. Both complexes form 1D architectures by virtue of hydrogen bonding interactions involving the free oxime group as donor and the oxime nitrogen (1) or carboxylate oxygens (2) as acceptors. IR data are discussed in terms of the known structures and coordination modes of the ligands.     

Synthesis of N‐alkoxybenzimidoyl azides and their reactions in electrophilic media

A new general route to N‐alkoxybenzimidoyl azides [ArC(N₃)=NOR] from a reaction of N‐alkoxybenzimidoyl bromide [ArC(Br)=NOR] with sodium azide in DMSO is described. These reactions result in the Z‐geometric configuration. These compounds show a moderate degree of thermal stability as assessed by differential scanning calorimetry, and lack reactivity in traditional 1,3‐dipolar cycloaddition ‘click’ reactions. Upon exposure to electrophilic compounds (trifluoroacetic acid or acetyl chloride), these azide compounds can react by two pathways: a Schmidt‐type rearrangement to form an N‐alkoxyurea or an isomerization–cyclization reaction pathway to form an N‐alkoxytetrazole. The route of the reaction has no dependence on solvent polarity and appears to depend upon the electrophile (H⁺ vs. CH₃CO⁺): reaction of the azide with trifluoroacetic acid results predominantly in the urea; reaction with acetyl chloride results solely in the tetrazole. Calculations indicate that the urea product is thermodynamically favored over the tetrazole product. They also indicate that both reaction conditions result in an equilibration between the starting azide and the tetrazole with the tetrazole being the major component in this equilibrium mixture. The fact that the azide also undergoes a Schmidt‐type rearrangement to form an N‐alkoxyurea when treated with trifluoroacetic acid appears to indicate that the barrier for aromatic ring migration is lower in the protonated azide produced on reaction with trifluoroacetic acid than in the acetylated azide produced on reaction with acetyl chloride. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of H3−2(x+y)MnxCoyPMo12O40 heteropolysalts. Application to adipic acid green synthesis from cyclohexanone oxidation with hydrogen peroxide

H_3−2(x+y)Mn_xCo_yPMo₁₂O₄₀ heteropolysalts (x + y ≤ 3/2 and x, y: 0–1.5) were prepared by a cationic exchange method based on barium sulfate precipitation. Structural and textural properties of salts were examined by several physicochemical techniques such as infrared, scanning electron microscopy-energy dispersive X-ray, and ³¹P nuclear magnetic resonance spectroscopies, X-ray diffraction diffraction, and thermogravimetric analysis, and their catalytic properties were evaluated in the cyclohexanone oxidation using hydrogen peroxide (30%). The reaction products, adipic, glutaric, succinic, hexanoic, 6-hydroxyhexanoic, 7,7-dimethoxy, and heptanoic acids and 1,1-dimethoxy octane were identified by gas chromatography–mass spectrometry analysis. Only adipic, glutaric, and succinic acids were quantified by chromatography (high-performance liquid chromatography), the other products were noted X. Adipic acid (AA) is the major product for all systems. The effects of molar ratios of catalyst/reactant and cyclohexanol/cyclohexanone, heteropolysalt composition, and reaction duration on AA yield were investigated. The stability of the catalytic system was also examined. H_3−2(x+y)Mn_xCo_yPMo₁₂O₄₀ catalysts were found to be efficient for the cyclohexanone oxidation with conversions >95%. Among them, H₁Mn_0.25Co_0.75 exhibits the highest AA yield (75%).     

氧气催化氧化环己烷

本文系统综述了O₂氧化剂用于环己烷催化氧化体系的研究进展,包括金属配合物催化、金属纳米粒子催化、金属氧化物粒子催化、分子筛催化、碳材料催化、光促进催化、杂多酸催化、金属-有机骨架材料催化等。本文认为研究、开发以O₂为氧化剂,高活性高选择性的非均相环己烷催化氧化体系将成为今后环己烷催化氧化研究的主要方向,尤其是多金属甚至多元素复合体系。本综述不仅对开发高催化活性高选择性的环己烷催化氧化体系,改进目前工业上的环己醇环己酮制备工艺具有重要的参考价值,而且还对其他烃类C-H键和C-C键高效催化氧化体系甚至其他氧化体系的研究与开发也具有重要的参考价值。     

1-[3’-(6’-苯甲酰基-N-烯丙基咔唑)]-1-丁酮肟-O-乙酸酯的合成和光引发性能

以N－烯丙基咔唑为原料,经Fridel-Crafts酰化反应、成肟和酯化,得到目标化合物。通过正交试验研究了关键步骤Fridel-Crafts酰化,得到最佳反应条件：N-烯丙基咔唑用量为0.020mol,催化剂与原料摩尔比1.10,反应物摩尔比1.15, 25℃下反应4h,产率可达94.2%。目标产物的结构通过IR,UV, 1H NMR和元素分析进行表征。并初步测试其光引发性能。     

Quantum chemical study on enantioselective reduction of keto oxime ether with borane catalyzed by oxazaborolidine. Part 1. Structures of catalyst–borane–keto oxime ether adducts

In the present work, quantum chemical computations of the enantioselective reduction of keto oxime ether with borane catalyzed by chiral oxazaborolidine are performed by means of the Hartree–Fock and the density functional methods. The structures of oxazaborolidine, oxazaborolidine–borane adduct, and oxazaborolidine–borane–keto oxime ether adducts are optimized completely at the HF/6‐31g* and B3LYP/6‐31g* levels and their properties studied in detail. The oxazaborolidine catalyst is a twisted chair structure and reacts with borane at the nitrogen site of the catalyst to form the catalyst–borane adduct whose formation reaction is exothermic. The catalyst–borane adduct reacts easily with keto oxime ether to form catalyst–borane–keto oxime ether adducts that have eight stable structures. The coordination of the carbonyl oxygen in keto oxime ether at the boron site of the catalyst is of more advantage to the enantioselective reduction of keto oxime ether than the coordination of the oxime nitrogen in the keto oxime ether at the boron site is. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 291–304, 2001     

壳聚糖硫酸盐催化合成环己酮缩乙二醇

由酮（醛）和醇合成缩酮（缩醛）,传统的催化剂是强质子酸（如浓硫酸、盐酸或磷酸）,其特点是催化剂价廉易得,催化活性高,但设备腐蚀严重,产物的后处理中存在大量的废酸废水造成环境污染。一些其它的酸性物质如NH2-SO3H、NaHSO4、SnCl4、Bi（NO3）3、维生素C等也是催化合成缩酮（缩醛）的良好催化剂,但催化剂难以回收利用。新型固体酸如分子筛、铌酸、SO4^2- -TiO2、TiSiW12O40／TiO2等由于其良好的催化活性和稳定性,与产物分离简便,     

柱后光化学衍生荧光检测高效液相色谱法测定2种新型肟醚类农药

建立了柱后光化学衍生荧光检测高效液相色谱法测定2种新型肟醚类农药(硫肟醚、HNPC-A2005)的方法。在优化的流动相配比(V甲醇∶V水=80∶20)及流速(1.0mL/min)条件下,用配备ZORBAXSB-C18色谱柱、自制的光化学反应器及荧光检测器的高效液相色谱仪对待测组分进行分离和测定。在最佳条件下,方法的检出限分别为0.056mg/L(硫肟醚)、0.036mg/L(HNPC-A2005);线性范围为0.090~5.0mg/L;相对标准偏差(0.1mg/L,n=8)分别为3.5%(硫肟醚)、0.8%(HNPC-A2005)。     

Diastereoselective cobalt-assisted Ferrier-type rearrangement to construct chiral alkynyl cyclohexanones

Functionalized 1-C-alkynyl sugars are prepared from 2-acetoxy-glucal triacetate. Dicobalt complexes of these sugar acetylenes can stabilize the anomeric carbenium cations, which promote the Ferrier-type rearrangement through the 5,6-dehydro precursors to afford alkynyl cyclohexanones after decomplexation. High stereoselectivity resulted from suitable steric interaction between the C-2 O-protecting group and the alkynyl substituents. Molecular mechanism is discussed.