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21.
Radical reactions mediated by Schwartz reagent and zirconocene(alkene) complex are firstly described. Schwartz reagent is a promising alternative to tributyltin hydride and the first transition metal hydrido complex used as a radical mediator in organic synthesis. A zirconocene(alkene) complex effects single electron transfer to alkyl halide to generate the corresponding alkyl radical. Secondly, serendipitous allylic C-H bond activation of the coordinating alkene of zirconocene(alkene) complex and its application to organic synthesis are summarized. By utilizing equilibrium between zirconocene(alkene) and zirconocene 2-alkenyl hydride, reaction of acid chloride with zirconocene(alkene) provides the corresponding homoallylic alcohol by sequential attacks of the hydride and 2-alkenyl moieties. A set of hydride and 2-alkenyl attacks on 1,4-diketone yields 6-heptene-1,4-diol derivative in high yield with high stereoselectivity. Selective capture of the hydride with diisopropyl ketone gives zirconocene 2-alkenyl alkoxide, which is a useful reagent for stereoselective allylation of aldehyde and imine. alpha-Halo carbonyl compounds undergo radical allylation with the zirconocene 2-alkenyl alkoxide which serves as a substitute for allyltin. 相似文献
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The design, construction and validation of a compact, portable flow injection analysis (FIA) instrument for underway analysis of phosphate in marine waters is described. This portable system employs gas pressure for reagent propulsion and computer controlled miniature solenoid valves for precise injection of multiple reagents into a flowing stream of filtered sample. A multi-reflection flow cell with a solid state LED photometer is used to detect filterable reactive phosphate (0.2 mum) as phosphomolybdenum blue. All the components are computer controlled using software developed using the Labviewtrade mark graphical programming language. The system has the capacity for sample throughput of up to 380 phosphate analyses per hour, but in the mode described here was operated at 225 analyses per hour. Under these conditions, the system exhibited a detection limit of 0.15 muM, reproducibility of 1.95 % RSD (n=9) and a linear response (r(2)=0.9992) when calibrated in the field with standards in the range 0.81-3.23 muM. The system was evaluated for the mapping of phosphate concentrations in Port Phillip Bay, south eastern Australia, and during the course of a 150 km cruise, 542 analyses were performed automatically. In general, good agreement was observed between analyses obtained using the portable FIA system and those obtained from manual sampling and laboratory analysis. 相似文献
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A reagent tablet for determination of fluoride ion has been prepared using ethylenediamine-N,N,N′,N′-tetraacetate complex of zirconium (Zr-EDTA), 3-hydroxy-2′-flavone (FS) and an appropriate pH buffer. Dissolving of the tablet into water exhibits an intense blue fluorescence (λmax = 460 nm) upon excitation at 377 nm and the fluorescence intensity decreases with the presence of fluoride ion. Hence, a simple fluorescent detection procedure for fluoride ion in aqueous media was successfully constructed with this tablet. The principle of this detection system is the ligand exchange reaction of FS bound to Zr-EDTA with fluoride ion. The present system provides an easy, rapid and selective determination method of fluoride ion ranging from 5 × 10−6 to 1 × 10−3 mol dm−3. The measurement of real samples with this tablet showed the similar results as those by the common method with the Alfusone reagent. 相似文献
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本文研究了华东师大新合成的显色剂 4- BPA- TB(俗称三溴偶氮膦 )与 Bi3+的显色反应。在 HCl O4和乙醇介质中试剂与 Bi3+生成蓝色的络合物 ,其最大吸收波长位于 6 4 4 nm。新显剂的最大吸收波长位于5 47nm,摩尔吸收系数 4.4× 1 0 4 L· mol- 1 · cm- 1 。Bi3+的含量在 5— 40 μg/2 5 m L 范围内符合比耳定律。用新显色剂测定了钢铁中的铋、结果令人满意。 相似文献
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Field measurement of nitrate in marine and estuarine waters with a flow analysis system utilizing on-line zinc reduction 总被引:1,自引:0,他引:1
A sensitive reagent-injection flow analysis method for the spectrophotometric determination of nitrate in marine, estuarine and fresh water samples is described. The method is based on the reduction of nitrate in a micro column containing zinc granules at pH 6.5. The nitrite formed is reacted with sulfanilamide and N-(1-naphthyl)ethylene diamine (Griess reagent), and the resulting azo compound is quantified spectrophotometrically at 520 nm. Water samples in the range of 3-700 μg L−1 NO3−-N can be processed with a throughput of up to 40 samples per hour, a detection limit of 1.3 μg L−1 and reproducibility of 1.2% RSD (50 μg L−1 NO3−-N, n = 10). The proposed method was successfully applied for the determination of nitrate in estuarine waters and the reliability was assessed by the analyses of certified reference materials and recovery experiments. The method is suitable for waters with a wide range of salinities, and was successfully used for more than 3200 underway nitrate measurements aboard SV Pelican1 in the “Two Bays” cruise in January 2010. 相似文献
26.
Shuo Wang Prof. Igor Larrosa Prof. Dr. Hideki Yorimitsu Dr. Gregory J. P. Perry 《Angewandte Chemie (International ed. in English)》2023,62(14):e202218371
The potassium salts of carboxylic acids are developed as efficient carboxylating agents through CO2 exchange. We describe these carboxylates as dual-function reagents because they function as a combined source of CO2 and base/metalating agent. By using the salt of a commercially available carboxylic acid, this protocol overcomes difficulties when using CO2 gas or organometallic reagents, such as pressurized containers or strictly inert conditions. The reaction proceeds under mild conditions, does not require transition metals or other additives, and shows broad substrate scope. Through the preparation of several biologically important molecules, we show how this strategy provides an opportunity for isotope labeling with low equivalents of labeled CO2. 相似文献
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Arghadip Ghosh Koneti Kondalarao Arijit Saha Vincent Gandon Akhila K. Sahoo 《Angewandte Chemie (International ed. in English)》2023,62(51):e202314395
A tandem three-component C−H bond addition involving the activation of an inert C(sp3)−H bond is reported. The process enables the direct regioselective synthesis of 1,2-difunctionalized arenes with the formation of C(sp3)− and C(sp2)−C(arene) bonds. 2-Iodobenzoic acid derivatives behave as masked bifunctional reagent (BFR) and react with 2-pyridyl-methyl sulfoximine (MPyS) protected aliphatic acids bearing α,α-disubstituted groups, and alkenes to produce β-aryl-δ-alkenyl amide derivatives in a single operation. The transformation involves Pd(II)/Pd(IV) and Pd(II)/Pd(0) catalytic systems. Detailed mechanistic studies, including density functional theory (DFT) calculations, reveal the formation of large T-shaped palladacycles and the onset of a 1,2-palladium migration via decarboxylation. 相似文献
28.
Jagadeesh Varma Nallaparaju Tatsiana Nikonovich Tatsiana Jarg Danylo Merzhyievskyi Prof. Dr. Riina Aav Dr. Dzmitry G. Kananovich 《Angewandte Chemie (International ed. in English)》2023,62(39):e202305775
Organomagnesium halides (Grignard reagents) are essential carbanionic building blocks widely used in carbon-carbon and carbon-heteroatom bond-forming reactions with various electrophiles. In the Barbier variant of the Grignard synthesis, the generation of air- and moisture-sensitive Grignard reagents occurs concurrently with their reaction with an electrophile. Although operationally simpler, the classic Barbier approach suffers from low yields due to multiple side reactions, thereby limiting the scope of its application. Here, we report a mechanochemical adaptation of the Mg-mediated Barbier reaction, which overcomes these limitations and facilitates the coupling of versatile organic halides (e.g., allylic, vinylic, aromatic, aliphatic) with a diverse range of electrophilic substrates (e.g., aromatic aldehydes, ketones, esters, amides, O-benzoyl hydroxylamine, chlorosilane, borate ester) to assemble C−C, C−N, C−Si, and C−B bonds. The mechanochemical approach has the advantage of being essentially solvent-free, operationally simple, immune to air, and surprisingly tolerant to water and some weak Brønsted acids. Notably, solid ammonium chloride was found to improve yields in the reactions of ketones. Mechanistic studies have clarified the role of mechanochemistry in the process, indicating the generation of transient organometallics facilitated by improved mass transfer and activation of the surface of magnesium metal. 相似文献
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M. Muñoz-Ortuño A. Argente-GarcíaY. Moliner-Martínez C. Molins-Legua P. Campíns-Falcó 《Analytica chimica acta》2015
A unique dispositive to determine casein which is the most abundant protein in dairy sewages has been proposed. In this sensing technology, the derivatization reagent 1,2-naphtoquininone 4-sulphonate (NQS) is embedded into a polydimethylsiloxane-tetraethylortosilicate-SiO2 nanoparticles composite (PDMS-TEOS-SiO2NPs). When the composite is immersed into the samples, casein is extracted from the solution and derivatized inside the PDMS matrix after 10 min at 100 °C. The sensing support changes its color from yellow to orange depending on the casein concentration. Quantitative analysis can be carried out by measuring the absorbance with a reflection probe or by image-processing tool (GIMP). This sensor provides good sensitivity and precision (RSD% <12%). The method validation has been done by applying the biocinchoninic acid method (BCA). Moreover, semiquatitative analysis of casein can be performed by visual observation. Taking into account the advantages of small size, rapidity, simplicity, good stability and high compatibility in aqueous solution, this sensor is expected to have potential practical applications for in-situ determination of casein. Finally the method has been applied to analyze effluents from dairy industries. 相似文献