共查询到20条相似文献,搜索用时 156 毫秒
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Chemical derivatization is often used to enhance the detectability of the target compounds and to improve the separation efficiency in high-performance liquid chromatography (HPLC). In this review, we describe the recent progress in the development of derivatization reagents having a benzofurazan structure, namely, the fluorogenic reagents, water-soluble reagents, reagents for the analysis of peptides and proteins, and reagents for mass spectrometric detection. The application of these reagents to bio-samples is also briefly described. 相似文献
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本文综述由离子交换树脂为原料制备的聚合物离子型试剂.绝大多数的聚合物离子型试剂是用强碱性阴离子交换树脂制备的,它包括氧化剂、还原剂、20余种亲核试剂以及卤化剂等.约有40多种聚合物试剂可全由强碱性阴离子交换树脂制备.由强酸性阳离子交换树脂所制成的试剂只有数种.弱酸性阳离子交换树脂所制成的试剂,只是刚刚开始.弱碱性阴离子交换树脂可制成的试剂几乎没有. 相似文献
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本文综述有机磷试剂在肽合成中的应用情况,介绍了各种用作氨基保护试剂的磷(膦)酰氯及硫代膦酰氯和四价鏻盐;并着重介绍了不同价态的有机磷试剂用于羧基活化的发展状况。 . t 相似文献
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Eliott Le Du Thibaut Duhail Dr. Matthew D. Wodrich Dr. Rosario Scopelliti Dr. Farzaneh Fadaei-Tirani Dr. Elsa Anselmi Dr. Emmanuel Magnier Prof. Dr. Jerome Waser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(42):10979-10986
Ethynylbenziodoxol(on)e (EBX) cyclic hypervalent iodine reagents have become popular reagents for the alkynylation of radicals and nucleophiles, but only offer limited possibilities for further structure and reactivity fine-tuning. Herein, the synthesis of new N-heterocyclic hypervalent iodine reagents with increased structural flexibility based on amide, amidine and sulfoximine scaffolds is reported. Solid-state structures of the reagents are reported and the analysis of the I−Calkyne bond lengths allowed assessing the trans-effect of the different substituents. Molecular electrostatic potential (MEP) maps of the reagents, derived from DFT computations, revealed less pronounced σ-hole regions for sulfonamide-based compounds. Most reagents reacted well in the alkynylation of β-ketoesters. The alkynylation of thiols afforded more variable yields, with compounds with a stronger σ-hole reacting better. In metal-mediated transformations, the N-heterocyclic hypervalent iodine reagents gave inferior results when compared to the O-based EBX reagents. 相似文献
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Demet Astley 《Tetrahedron letters》2004,45(39):7315-7317
Substitution of the chloro group in 2-(2-chlorophenyl)-4,4-dimethyl-2-oxazoline to afford biaryls occurs upon reaction with either aryllithium reagents or aryl Grignard reagents. The reactions with Grignard reagents occur under similar conditions to a previously reported manganese-catalysed procedure. The reactions with lithium reagents, whilst not always affording greater yields of product than the Grignard reagents, involve much shorter reaction times and afford yields, which are comparable with those obtained from the corresponding fluoro derivative. 相似文献
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Thiol esters and organoindium reagents undergo palladium-catalyzed cross-coupling under mild conditions to give ketones in moderate to excellent yields. Aryl and primary/secondary alkyl organoindium reagents can be used as coupling partners. This method has two advantages over the cross-coupling of thiol esters with boron and tin reagents: (1) no added copper reagent is required to mediate the reaction and (2) for the case of alkyl transfer, no added base is required to activate organoindium reagents for cross-coupling as is required for the coupling of alkyl boron reagents with thiol esters. 相似文献
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Patrícia Xavier Baliza 《Talanta》2009,79(1):2-377
Pyridylazo and thiazolylazo reagents are synthetic dyes widely used in analytical chemistry. These reagents are also very attractive for use in preconcentration systems. This paper covers the application of pyridylazo and thiazolylazo reagents in flow injection systems for the determination of metals. The article discusses flow injection preconcentration systems with solid-phase extraction, precipitation and cloud point extraction. The use of pyridylazo and thiazolylazo reagents in flow injection detection systems is also presented. The relative advantages and drawbacks of these systems are discussed. The application of pyridylazo and thiazolylazo reagents in new systems is presented in the concluding part of this review article. 相似文献
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Diorganocadmium reagents cannot react with ketoxime at room temperature. CuCN catalysis allows diarylcadmium reagents to react with ketoxime and to give corresponding arylamines in good to high yields at room temperature. According to the electronic effects of the substituent attached to the aromatic ring, functionalized diarylcadmium reagents show meta-para selectivity in their amination reactions. Also compared to diarylzinc reagents, diarylcadmium reagents react with O-substituted ketoxime under milder reaction conditions and they form corresponding arylamines in higher yields. CuCN cannot help dialkyl-, dicycloalky-, and dibenzylcadmium reagents to react with ketoxime. Our Aryl C-N bond formation method does not include cadmium excretion into the environment. 相似文献
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Mohamed Elsherbini Bethan Winterson Haifa Alharbi Ana A. Folgueiras‐Amador Clina Gnot Thomas Wirth 《Angewandte Chemie (International ed. in English)》2019,58(29):9811-9815
An efficient and reliable electrochemical generator of hypervalent iodine reagents has been developed. In the anodic oxidation of iodoarenes to hypervalent iodine reagents under flow conditions, the use of electricity replaces hazardous and costly chemical oxidants. Unstable hypervalent iodine reagents can be prepared easily and coupled with different substrates to achieve oxidative transformations in high yields. The unstable, electrochemically generated reagents can also easily be transformed into classic bench‐stable hypervalent iodine reagents through ligand exchange. The combination of electrochemical and flow‐chemistry advantages largely improves the ecological footprint of the overall process compared to conventional approaches. 相似文献
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[reaction: see text] The reaction of imidazo[2,1-b]thiazolines with various organometallic reagents is described. Nucleophilic attack of organolithium reagents on sulfur occurs with extrusion of ethylene to produce 2-thioalkyl- or 2-thioarylimidazoles. The outcome with Grignard reagents, however, is less predictable, with some reagents adding at sulfur and others reacting at C-2 or not at all. 相似文献
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Brazier JN 《Talanta》1969,16(7):949-966
The uses of metal complex compounds in the various fields of analytical chemistry are reviewed with particular reference to newer reagents and fresh applications of established reagents. The topics covered include precipitants, volumetric reagents, indicators and solvent extraction reagents. A new method for the gravimetric determination of gold with trans-dichlorobis(ethylenediamine) cobalt(III) chloride is included. 相似文献
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Stephen T. HellerRichmond Sarpong 《Tetrahedron》2011,67(46):8851-8859
The optimization, substrate scope, and mechanism of esterification and amidation of carboxylic acids mediated by imidazole-based reagents are discussed. The innate reactivity of carbonylimidazole reagents with a range of nucleophiles is also explored. New reagents developed for the synthesis of α,β-unsaturated esters are described, as are reagents for the preparation of tertiary amides directly from carboxylic acids. 相似文献
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Dr. Kilian Colas A. Catarina V. D. dos Santos Dr. Stefanie V. Kohlhepp Dr. Abraham Mendoza 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(9):e202104053
The synthesis of ketones through addition of organometallic reagents to aliphatic carboxylic acids is a straightforward strategy that is limited to organolithium reagents. More desirable Grignard reagents can be activated and controlled with a bulky aniline-derived turbo-Hauser base. This operationally simple procedure allows the straightforward preparation of a variety of aliphatic and perfluoroalkyl ketones alike from functionalized alkyl, aryl and heteroaryl Grignard reagents. 相似文献
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Single‐Electron‐Transfer‐Induced Coupling of Arylzinc Reagents with Aryl and Alkenyl Halides
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Prof. Eiji Shirakawa Fumiko Tamakuni Eugene Kusano Nanase Uchiyama Wataru Konagaya Ryo Watabe Prof. Tamio Hayashi 《Angewandte Chemie (International ed. in English)》2014,53(2):521-525
Arylzinc reagents, prepared from aryl halides/zinc powder or aryl Grignard reagents/zinc chloride, were found to undergo coupling with aryl and alkenyl halides without the aid of transition‐metal catalysis to give biaryls and styrene derivatives, respectively. In this context, we have already reported the corresponding reaction using aryl Grignard reagents instead of arylzinc reagents. Compared with the Grignard cross‐coupling, the present reaction features high functional‐group tolerance, whereby electrophilic groups such as alkoxycarbonyl and cyano groups are compatible as substituents on both the arylzinc reagents and the aryl halides. Aryl halides receive a single electron and thereby become activated as the corresponding anion radicals, which react with arylzinc reagents, thus leading to the cross‐coupling products. 相似文献