Water-acetic acid mediated an efficient one-pot eco-friendly synthesis of novel bis-isoxazolopyrroloquinoline derivatives

An efficient, cost-effective and environmentally benign synthesis of novel tetracyclic bis-isoxazolopyrroloquinoline derivatives has been developed via one-pot four-component reaction of 4-amino-3-methyl-5-styrylisoxazoles, dimedone, aryl glyoxal monohydrates and 5-amino-3-methylisoxazole by employing water as a reaction medium and acetic acid (AcOH) as a green promoter. The advantages of this protocol are environmentally friendly, metal-free, less reaction time, operational simplicity, high yields, broad substrate scope and easy purification. Most significant of all, this method is green.     

纯水中检测汞离子与银离子的菲啰啉类荧光探针

合成了菲啰啉类化合物探针1,并通过核磁共振波谱(NMR)、质谱(MS)、红外光谱(IR)对其结构进行了表征。利用荧光发射光谱考察了探针1对Hg~(2+)及Ag~+的识别性能。结果表明,探针1在纯水介质中以荧光猝灭的方式识别Hg~(2+)和Ag~+,其结合比分别为1∶1和2∶1,检测的线性范围分别为9.0×10~(-7)～1.1×10~(-5)和8.0×10~(-7)～7.0×10~(-6) mol/L,相关系数(r~2)均大于0.99,检出限均低至10~(-8)mol/L。根据探针1识别前后荧光强度的剧烈变化,建立了裸眼检测Hg~(2+)和Ag~+的可视化分析方法。通过等温量热滴定与~1H NMR滴定考察了识别过程的热力学参数和作用机理。该研究对生物体及环境领域中Hg~(2+)和Ag~+的实时监测具有潜在的应用价值。     

Solubility of 1-Butene in Water and in a Medium for Cultivation of a Bacterial Strain

Solubility measurements of 1-butene in water, from 20 to 50°C and at atmospheric pressure, were carried out using a Ben-Naim/Baer-type apparatus. The experimental results have a precision of about ±0.3%. Using accurate thermodynamic relations, the Ostwald coefficients at the experimental conditions and at infinite dilution, the mole fractions of the dissolved gas at the gas partial pressure of 101.325 kPa and the Henry coefficients at the water vapor pressure were calculated. The mole fraction of dissolved gas were fitted to the Clarke, Glew, and Weiss equation and thermodynamic quantities, standard molar Gibbs energy, entropy, and enthalpy changes, for the process of transferring the 1-butene molecules from the gaseous to the water phase, were computed. Moreover, solubility measurements of 1-butene in an aqueous medium for the cultivation of Xanthobacter Py2 in the same temperature range were also performed at atmospheric pressure. These solubility data are approximately 2.6% lower than those observed in pure water.     

Kinetic spectrophotometric determination of trace manganese (II) with dahlia violet in nonionic microemulsion medium

A new catalytic kinetic spectrophotometric method has been developed for the determination of trace amount of manganese (II) in nonionic microemulsion medium. The method is based on the catalytic effect of manganese (II) on the oxidation of dahlia violet by potassium periodate with nitrilotriacetic acid as an activitor in the presence of nonionic microemulsion. Under the optimum conditions, the calibration graph is linear in the range of 0.0004-0.0056 μg ml⁻¹ of manganese (II) at 580 nm. The detection limit achieved is 3.75×10⁻⁵ μg ml⁻¹. Manganese (II) in foodstuff samples was determined with satisfactory results.     

附加试剂及反应介质对TPPFeCl催化环己烷仿生氧化反应性能的影响

研究了某些附加试剂及反应介质对四苯基卟吩合铁(Ⅲ)[TPPFeCl或(TPPFe)₂O]模拟细胞色素P-450催化PhIO羟化环己烷反应的影响。发现适量的异丙醇、吡啶及NaOH能促进反应,加入盐酸及增大介质的极性对反应不利。证明了副产物环己酮主要是由PhIO直接氧化主产物环己醇生成的,TPPFeCl的存在不利于酮的生成,醇的存在能延长催化剂的寿命。     

One-Pot Oxidation of Alanine and Its Ethyl Ester with a Mild Oxidant 4′-Methylazobenzene-2-sulfenyl Bromide

One-pot oxidation of alanine and its ethyl ester with a mild oxidant 4′-methylazobenzene-2-sulfenyl bromide is described. Using a nonreactively water-soluble electrophilic species, 4′-methylazobenzene-2-sulfenyl bromide, with L-alanine and its ethyl ester (in 3:1 molar proportions) in aqueous solution at room temperature, the corresponding sulfenimines are prepared. On hydrolysis in acidic medium at room temperature, these sulfenimines give ethanal and pyruvic acid respectively.

高频燃烧红外吸收法测定氧化钴粉中的硫高频燃烧红外吸收法测定氧化钴粉中的硫高频燃烧红外吸收法测定氧化钴粉中的硫

采用高频红外吸收法测定了氧化钴粉中硫的含量,并对样品作测定前的预处理（物理处理）,在测定上选用复合型助熔剂,解决了高频感应炉中因顶吹氧气流的作用而导致的样品喷溅问题。并将镍作为辅助助熔剂应用于碳硫测定。该方法可准确测定硫含量为 0.001％～0.1％ 的氧化钴粉中的硫,回收率为 95.6％～104.8%。RSD 为2.2％～4.9％。     

Polyethylene Glycol as Support and Phase Transfer Catalyst in Aqueous Palladium-catalyzed Liquid-phase Synthesis

Recently, the liquid-phase synthesis of small organic compounds has been a preferable strategy due to its combination with the advantage of solution-phase and solid-phase methods1. Among the various soluble polymers, polyethylene glycol (PEG) is the most useful as support. It has been reported that PEG bound substrates could also play the role of phase-transfer catalyst (PTC) in some reactions2. Herein we reported that palladium-catalyzed coupling reactions could be taken place smoothly…     

Asymmetric Synthesis of Densely Functionalized Medium‐Ring Carbocycles and Lactones through Modular Assembly and Ring‐Closing Metathesis of Sulfoximine‐Substituted Trienes and Dienynes

An asymmetric synthesis of densely functionalized 7–11‐membered carbocycles and 9–11‐membered lactones has been developed. Its key steps are a modular assembly of sulfoximine‐substituted C‐ and O‐tethered trienes and C‐tethered dienynes and their Ru‐catalyzed ring‐closing diene and enyne metathesis (RCDEM and RCEYM). The synthesis of the C‐tethered trienes and dienynes includes the following steps: 1) hydroxyalkylation of enantiomerically pure titanated allylic sulfoximines with unsaturated aldehydes, 2) α‐lithiation of alkenylsulfoximines, 3) alkylation, hydroxy‐alkylation, formylation, and acylation of α‐lithioalkenylsulfoximines, and 4) addition of Grignard reagents to α‐formyl(acyl)alkenylsulfoximines. The sulfoximine group provided for high asymmetric induction in steps 1) and 4). RCDEM of the sulfoximine‐substituted trienes with the second‐generation Ru catalyst stereoselectively afforded the corresponding functionalized 7–11‐membered carbocyles. RCDEM of diastereomeric silyloxy‐substituted 1,6,12‐trienes revealed an interesting difference in reactivity. While the (R)‐diastereomer gave the 11‐membered carbocyle, the (S)‐diastereomer delivered in a cascade of cross metathesis and RCDEM 22‐membered macrocycles. RCDEM of cyclic trienes furnished bicyclic carbocycles with a bicyclo[7.4.0]tridecane and bicyclo[9.4.0]pentadecane skeleton. Selective transformations of the sulfoximine‐ and bissilyloxy‐substituted carbocycles were performed including deprotection, cross‐coupling reaction and reduction of the sulfoximine moiety. Esterification of a sulfoximine‐substituted homoallylic alcohol with unsaturated carboxylic acids gave the O‐tethered trienes, RCDEM of which yielded the sulfoximine‐substituted 9–11‐membered lactones. RCEYM of a sulfoximine‐substituted 1,7‐dien‐10‐yne showed an unprecedented dichotomy in ring formation depending on the Ru catalyst. While the second‐generation Ru catalyst gave the 9‐membered exo 1,3‐dienyl carbocycle, the first‐generation Ru catalyst furnished a truncated 9‐membered 1,3‐dieny carbocycle having one CH₂ unit less than the dienyne.     

H-shaped liquid crystals inducing nematic order in the isotropic liquid

ABSTRACT

We prepared a homologous series of H-shaped liquid crystals I-n and investigated their phase transition properties using optical microscopy and differential scanning calorimetry. All the compounds exhibited a nematic phase at room temperature. The phase transition behaviour is explained in terms of molecular shape anisotropy. Furthermore, those compounds were found to exhibit electro-optical switching in the isotropic liquid in the vicinity of the nematic–isotropic liquid transition, indicating that the microscopic nematic order with a certain coherence length of the molecules exists in the optically isotropic temperature range.