Synthesis of 6-aryl- and 5-aroylcomanic acids from 5-aroyl-2-carbethoxy-4-pyrones via a deformylative rearrangement and ring-opening/ring-closure sequence

The reaction of 1-aryl-2-(dimethylaminomethylene)butane-1,3-diones with diethyl oxalate in the presence of sodium hydride in THF gave ethyl 5-aroyl-4-oxo-4H-pyran-2-carboxylates, from which 4-oxo-6-aryl-4H-pyran-2-carboxylic acids (6-arylcomanic acids) were obtained in high yields via acid-catalyzed deformylative rearrangement. 5-Aroyl-4-oxo-4H-pyran-2-carboxylic acids (5-aroylcomanic acids) were prepared via а ring-opening/ring-closure sequence by the reaction of 5-aroyl-2-carbethoxy-4-pyrones with piperidine and subsequent basic hydrolysis and acidification.     

One-pot synthesis of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives using multi-component reactions

In this work, a new series of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives have been synthesized using an aromatic 1,2-diamine, Meldrum's acid, an isocyanide, and an arylidene malononitrile (or an aldehyde and malononitrile instead of an arylidene malononitrile) in CH₂Cl₂ at ambient temperature. Synthesis of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine proceeded via four- and five-component reactions; while the synthesis of malonamide derivatives was performed using five- and six-component reactions. In addition, a new series of the malonamide derivatives have been prepared using an aldehyde, malononitrile, Meldrum's acid, an isocyanide, and two molecules of 1,4-diamine via a six-component reaction. These procedures provide alternative methods to the synthesis of a new series of 1,2,4,5-tetrahydro-2,4-dioxobenzo[b][1,4]diazepine and malonamide derivatives.     

Synthesis of on resin poly(propylene imine) dendrimer and its use as organocatalyst

Solid phase synthesis of poly(propylene imine) dendrimer is described. An iterative synthesis including double Michael addition of acrylonitrile to the primary amino groups on crosslinked polystyrene support followed by reduction of nitrile groups to amino groups give poly(propylene imine) dendrimers up to third generation attached to the polystyrene support. The supported dendrimer is used as an organocatalyst to Knoevenagel condensations. The supported catalyst showed good selectivity and the product was obtained in excellent yield under green reaction conditions. Densely packed amino groups enhance catalysis by a co-operative effect. The catalyst is recoverable and reusable.     

富氮多孔有机聚合物催化制备α⁃氰基肉桂酸乙酯

α-氰基肉桂酸乙酯作为含多种官能团的缺电子烯烃, 是一种极具应用价值的有机合成反应底物, 主要通过催化Knoevenagel缩合反应获得. 本文以多聚甲醛和三聚氰胺为前驱体, 采用溶剂热法制备富氮多孔有机聚合物mPMF, 经K₂CO₃处理得到K₂CO₃-mPMF-X(X=1, 10, 50). 考察了mPMF在苯甲醛和氰乙酸乙酯Knoevenagel缩合反应中的催化性能, 通过mPMF与K₂CO₃-mPMF-X催化活性的比较, 探讨了碱性强弱对Knoevenagel缩合反应的影响, 并对催化反应机理进行了探索. 结果表明, 催化剂中丰富的氮物种为反应提供了碱性环境和大量的碱性活性位点, 催化剂碱性强弱的控制是催化合成α-氰基肉桂酸乙酯的关键因素. mPMF在甲醇溶剂中于60 ℃反应3 h后, 苯甲醛转化率为97%, 目标产物选择性在99.9%以上.     

滤膜冷凝收集-离子色谱法测定固液气溶胶中5种水溶性阴离子北大核心CSCD

水溶性离子是固、液气溶胶的重要组成部分,对于气溶胶的理化性质和空气质量具有重大影响,研究水溶性离子的含量对于大气环境的污染与防治具有深远意义。该研究建立了一种滤膜冷凝收集-离子色谱技术采集固体气溶胶和液体气溶胶并测定其中的5种水溶性阴离子(Cl^(-)、F^(-)、NO^(-)_(3)、NO2^(-)、SO4^(2-))含量的方法。首先,采用固体颗粒过滤器和冷凝收集法分别收集固体气溶胶和液体气溶胶,固体气溶胶以固体颗粒物的形式被收集在固体颗粒过滤器内,液体气溶胶以冷凝液的形式在冷阱中被收集。其次,以离子色谱法对固、液体气溶胶中的水溶性阴离子含量进行检测。在以Dionex IonPac AS11-HC-4μm作为分析柱,流速为1 mL/min,柱温为30℃,淋洗液氢氧化钾(KOH)浓度在0~40 min内由1 mol/L线性增至25 mol/L,进样量100μL的条件下,各离子在40 min内有效分离,5种阴离子在0.1~10 mg/L范围内线性关系良好(相关系数为0.9992~0.9997),检出限低(0.02~0.04 mg/L)。对样品采集条件(采样时间、采样温度和采样流量)进行了优化,结果表明,在采样时间2 h、采样温度-13℃、采样流量1.0 L/min的条件下,可获得较为满意的结果。在优化的条件下分别对实际样品的两类溶胶中的5种阴离子含量进行了检测,测得实际样品的液体气溶胶中5种阴离子含量分别为5.7402μg/m^(3)(F^(-))、1.1599μg/m^(3)(Cl^(-))、3.3233μg/m^(3)(NO^(-)_(2))、2.4861μg/m^(3)(NO^(-)_(3))和0.9745μg/m^(3)(SO^(2-)_(4)),固体气溶胶中5种阴离子含量分别为14.1037μg/m^(3)(F^(-))、5.0398μg/m^(3)(Cl^(-))、9.3052μg/m^(3)(NO^(-)_(2))、8.4528μg/m^(3)(NO^(-)_(3))和5.6314μg/m^(3)(SO^(2-)_(4))。该方法可应用于实际的大气检测中,也为其他离子的采集和分析条件的摸索提供了方法。     

高分子化学线型缩聚反应数均聚合度计算的教学体验和改进

对高分子化学课程本科教学中有关线型缩聚反应数均聚合度的计算,以及聚合度与官能团过量之间的定性及定量关系进行了讨论。针对现有教学方法易引发学生误解和混淆的情况,定义了新的参数和发展了相应改进的计算方程。新的计算方程的计算过程清晰、参数定义明确、易于学生理解掌握,在实践中取得了良好的教学效果。     

Metal- and Solvent-Free Transesterification and Aldol Condensation Reactions by a Homogenous Recyclable Basic Ionic Liquid Based on the 1,3,5-Triazine Framework

A new recyclable basic ionic liquid was introduced as an efficient catalyst for aldol condensation and transesterification reactions under environmentally friendly conditions. The catalyst was prepared based on methyl imidazolium moieties bearing hydroxide counter anions via the Hofmann elimination on a 1,3,5-triazine framework. The ionic liquid with two functionalities including anion stabilizer and high basicity, was used as an efficient catalyst for aldol condensation as well as transesterification reaction of a variety of alkyl benzoates. All reactions were performed in the absence of any external reagent, co-catalyst, or solvent, in line with environmental protection. The kinetics isotope effect (KIE) was conducted for the transesterification reaction to elucidate the mechanism and rate determining step (RDS). It worth noted that, the homogeneous catalyst could be recycled from the reaction mixture and reused for several consecutive runs with insignificant drop of basicity and conversion.     

On the Heterogeneous Nature of Cisplatin-1-Methyluracil Complexes: Coexistence of Different Aggregation Modes and Partial Loss of NH3 Ligands as Likely Explanation

The conversion of the 1 : 1-complex of Cisplatin with 1-methyluracil (1MeUH), cis-[Pt(NH₃)₂(1MeU-N3)Cl] ( 1 a ) to the aqua species cis-[Pt(NH₃)₂(1MeU-N3)(OH₂)]⁺ ( 1 b ), achieved by reaction of 1 a with AgNO₃ in water, affords a mixture of compounds, the composition of which strongly depends on sample history. The complexity stems from variations in condensation patterns and partial loss of NH₃ ligands. In dilute aqueous solution, 1 a , and dinuclear compounds cis-[(NH₃)₂(1MeU-N3)Pt(μ-OH)Pt(1MeU-N3)(NH₃)₂]⁺( 3 ) as well as head-tail cis-[Pt₂(NH₃)₄(μ-1MeU-N3,O4)₂]²⁺ ( 4 ) represent the major components. In addition, there are numerous other species present in minor quantities, which differ in metal nuclearity, stoichiometry, stereoisomerism, and Pt oxidation state, as revealed by a combination of ¹H NMR and ESI-MS spectroscopy. Their composition appears not to be the consequence of a unique and repeating coordination pattern of the 1MeU ligand in oligomers but rather the coexistence of distinctly different condensation patterns, which include μ-OH, μ-1MeU, and μ-NH₂ bridging and combinations thereof. Consequently, the products obtained should, in total, be defined as a heterogeneous mixture rather than a mixture of oligomers of different sizes. In addition, a N₂ complex, [Pt(NH₃)(1MeU)(N₂)]⁺ appears to be formed in gas phase during the ESI-MS experiment. In the presence of Na⁺ ions, multimers n of 1 a with n=2, 3, 4 are formed that represent analogues of non-metalated uracil quartets found in tetrastranded RNA.     

Structural characterization and X-ray analysis by Williamson–Hall method for Erbium doped Aluminum Nitride nanoparticles,synthesized using inert gas condensation technique

We have synthesized AlN nanoparticles (NPs) doped in-situ with Er (AlN:Er) using inert gas condensation technique. Using x-ray diffraction (XRD) peak broadening analysis with the Williamson–Hall (W–H) Uniform Deformation Model (UDM) the crystallite size of the NPs and the strain in NPs were found to be 80±38 nm and 3.07×10⁻³±0.9×10⁻³ respectively. In comparison, using the Debye–Scherrer's (DS) formula, we have inferred that the crystallite size of the NPs was 23±6 nm and the average strain was 4.3×10⁻³±0.4×10⁻³. The scanning electron microscopy images show that the NPs are spherical and have an average diameter of ∼300 nm. The crystallite size is smaller than the size of the NPs revealing their polycrystalline behavior. In addition, the NPs strain, stress and energy density were also calculated using W–H analysis combined with the Uniform Deformation Stress Model (UDSM) and the Uniform Deformation Energy Density Model (UDEDM). Suggested by the spherical geometry and polycrystalline nature of the AlN NPs, the strain computed from UDM, UDSM and UDEDM were in agreement confirming an isotropic mechanical nature of the particle. Luminescence measurements revealed the temperature dependence of the optical emission of the Er³⁺ ions, confirming the use of AlN:Er NPs for nano-scale temperature sensing.     

On-Surface Formation of Cyano-Vinylene Linked Chains by Knoevenagel Condensation

The rapid development of on-surface synthesis provides a unique approach toward the formation of carbon-based nanostructures with designed properties. Herein, we present the on-surface formation of CN-substituted phenylene vinylene chains on the Au(111) surface, thermally induced by annealing the substrate stepwise at temperatures between 220 °C and 240 °C. The reaction is investigated by scanning tunneling microscopy and density functional theory. Supported by the calculated reaction pathway, we assign the observed chain formation to a Knoevenagel condensation between an aldehyde and a methylene nitrile substituent.