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Showing papers on "Reagent published in 1994"


Journal ArticleDOI
07 Oct 1994-Science
TL;DR: The ability to separate a catalyst or a reagent from the products completely at mild conditions could lead to industrial application of homogeneous catalysts or reagents and to the development of more environmentally benign processes.
Abstract: A novel concept for performing stoichiometric and catalytic chemical transformations has been developed that is based on the limited miscibility of partially or fully fluorinated compounds with nonfluorinated compounds. A fluorous biphase system (FBS) consists of a fluorous phase containing a dissolved reagent or catalyst and another phase, which could be any common organic or nonorganic solvent with limited or no solubility in the fluorous phase. The fluorous phase is defined as the fluorocarbon (mostly perfluorinated alkanes, ethers, and tertiary amines)-rich phase of a biphase system. An FBS compatible reagent or catalyst contains enough fluorous moieties that it will be soluble only or preferentially in the fluorous phase. The most effective fluorous moieties are linear or branched perfluoroalkyl chains with high carbon number; they may also contain heteroatoms. The chemical transformation may occur either in the fluorous phase or at the interface of the two phases. The application of FBS has been demonstrated for the extraction of rhodium from toluene and for the hydroformylation of olefins. The ability to separate a catalyst or a reagent from the products completely at mild conditions could lead to industrial application of homogeneous catalysts or reagents and to the development of more environmentally benign processes.

1,249 citations


Journal ArticleDOI
TL;DR: In this paper, the aziridination of olefins was evaluated and found to be both catalyst and substrate dependent, and it was concluded that the olefin selectivity profile for the reaction is independent of the oxidation state of the copper catalyst employed.
Abstract: Soluble Cu(1) and Cu(I1) triflate and perchlorate salts are efficient catalysts for the aziridination of olefins employing (N-@-tolylsulfonyl)imino)phenyliodinane, PhI=NTs, as the nitrene precursor. Electron-rich as well as electron-deficient olefins undergo aziridination with this reagent in 55-958 yields, at temperatures ranging from -20 OC to +25 OC. The catalyzed nitrogen atom-transfer reaction to enol silanes and silylketene acetals has also been developed to provide facile syntheses of a-amino ketones. Other metal complexes were found to be less effective at catalyzing the reaction, while PhI=NTs proved to be superior to other imido group donors as the nitrene precursor. Reaction rates and yields are enhanced in polar aprotic solvents such as MeCN and MeN02. Reaction stereospecificity in the aziridination of cis and trans disubstituted olefins was evaluated and found to be both catalyst and substrate dependent. Intermolecular competition experiments between pairs of monoand disubstituted olefins indicate that the olefin selectivity profile for the reaction is independent of the oxidation state of the copper catalyst employed. It is concluded that these reactions are proceeding through the 2+ catalyst oxidation state under the conditions employed

539 citations


Journal ArticleDOI
TL;DR: Iodoxy benzoic acid (IBX) smoothly oxidizes primary and secondary alcohols to aldehydes and ketones, respectively, without any oxidative cleavage of the glycol CC bond as discussed by the authors.

436 citations


Journal ArticleDOI
TL;DR: The Dess-Martin periodinane (DMP) was used in the synthesis of rapamycin this article, and the resulting DMP was crystalline and completely soluble in CH2Clz and CDC13.
Abstract: The Dess-Martin periodinane (DMP), l,l,l-triacetoxy-l,l-dihydro-l,2-benziodoxol-3(LH)-one (2),l is one of the mildest and most convenient reagents available for oxidation of alcohols (Figure 1). DMP enjoys increasing use despite suggestion that its behavior can be capricious.2 Recently, Ireland has addressed a problem of inconsistency in DMP batch quality by offering an improved procedure for synthesizing the reagenta2 Important as it is to have a reliable method of preparing pure DMP, we suspect that many D-M (Dess-Martin) oxidations in the literature have been effected not by DMP, but by an impurity commonly present in DMP samples. In our own laboratory, a crucial D-M oxidation in the total synthesis of rapamycin3 proceeded consistently only with a single 2-year old batch of the reagent, material that was largely insoluble in CDC13 and that exhibited a complex proton NMR spectrum. Several other samples of DMP, including relatively pure reagent prepared according to the Ireland method,2 failed to perform the desired transformation. Questions about the composition of the effective sample motivated the present Dess-Martin periodinane study. In attempts to obtain the impurities present in the effective DMP reagent, we explored Dess and Martin's preparation of the oxidant. However, pure, crystalline DMP was reproducibly obtained using their procedure by adhering to the following details: (1) In order to permit greater ease of stirring during oxidation of iodobenzoic acid, the initially viscous reaction mixture was more dilute than in the D-M preparation, which may ensure that oxidation proceeds to ~ompletion.~ (2) Iodinane oxide 1 was heated at 85 "C in Ac20 and AcOH at least 1 h beyond the time that dissolution was complete. (3) After acetylation, the mixture was allowed to stand for 1-2 days to permit crystallization of DMP.5 (4) During isolation of the product, exposure to atmosphere was strictly avoided. The resulting DMP was crystalline and completely soluble in CH2Clz and CDC13. The reagent contained a small amount of AcOH, but otherwise its NMR spectra showed no significant (>3%) extraneous peaks. When pure DMP prepared as above was used under inert conditions (flame-dried glassware, dry solvents,

403 citations


Journal ArticleDOI
TL;DR: A glass microchip with a postcolumn reactor was fabricated to conduct postseparation derivatization using o-phthaldialdehyde as a fluorescent "tag" for amino acids as mentioned in this paper.
Abstract: A glass microchip with a postcolumn reactor was fabricated to conduct postseparation derivatization using o-phthaldialdehyde as a fluorescent «tag» for amino acids. This miniaturized separation device was constructed using standard photolithographic, wet chemical etching, and bonding techniques. Effects of the reagent stream on separation efficiency were investigated. In addition, a novel gated injector was demonstrated which maintains the integrity of the analyte, buffer, and reagent streams

377 citations


Journal ArticleDOI
TL;DR: In this paper, a glass microchip was constructed to perform chemical reactions and capillary electrophoresis sequentially, and the microchip has a reaction chamber with a 1 nL reaction volume and a separation column with a 15.4 mm separation length.
Abstract: A glass microchip was constructed to perform chemical reactions and capillary electrophoresis sequentially. The channel manifold on the glass substrate was fabricated using standard photolithographic, etching, and deposition techniques. The microchip has a reaction chamber with a 1 nL reaction volume and a separation column with a 15.4 mm separation length. Electrical control of the buffer, analyte, and reagent streams made possible the precise manipulation of the fluids within the channel manifold. The microchip was operated under a continuous reaction mode with gated injections to introduce the reaction product onto the separation column with high reproducibility (<1.8% rsd in peak area). The reaction and separation performances were evaluated by reacting amino acids with o-phthaldialdehyde to generate a fluorescent product which was detected by laser-induced fluorescence. Control of the reaction and separation conditions was sufficient to measure reaction kinetics and variation of detection limits with reaction time. Half-times of reaction of 5.1 and 6.2 s and detection limits of 0.55 and 0.83 fmol were measured for arginine and glycine, respectively. 18 refs., 10 figs.

325 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of uniform gold sols produced by the citrate reduction of auric acid is explored as a function of temperature and reagent concentration, and a particle growth model incorporating colloidal stability is postulated.

272 citations


Patent
15 Sep 1994
TL;DR: In this paper, an analytical test device useful for example in pregnancy testing, consisting of a hollow casing (500) constructed of moisture-impervious solid material, such as plastics materials, containing a dry porous carrier (510) which communicates indirectly with the exterior of the casing via a bibulous sample receiving member (506) which protrudes from the casing such that a liquid test sample can be applied to the receiving member and permeate therefrom to the porous carrier, the carrier containing in a first zone a labelled specific binding reagent is freely mobile within the carrier when
Abstract: An analytical test device useful for example in pregnancy testing, comprises a hollow casing (500) constructed of moisture-impervious solid material, such as plastics materials, containing a dry porous carrier (510) which communicates indirectly with the exterior of the casing via a bibulous sample receiving member (506) which protrudes from the casing such that a liquid test sample can be applied to the receiving member and permeate therefrom to the porous carrier, the carrier containing in a first zone a labelled specific binding reagent is freely mobile within the porous carrier when in the moist state, wherein the mobility is facilitated by a material comprising a sugar, in an amount effective to reduce interaction between the test strip and the labelled reagent, and in a second zone spatially distinct from the first zone unlabelled specific binding reagent for the same analyte which unlabelled reagent is permanently immobilised on the carrier material and is therefore not mobile in the moist state, the two zones being arranged such that liquid sample applied to the porous carrier can permeate via the first zone into the second zone, and the device incorporating means, such as an aperture (508) in the casing, enabling the extent (if any) to which the labelled reagent becomes bound in the second zone to be observed. Preferably the device includes a removable cap for the protruding bibulous member.

218 citations


Book
01 Jan 1994
TL;DR: In this article, the future of supported reagents in their applications as genuine catalysts is mapped out in terms of their potential as catalysts in the field of supporting reagent catalysis.
Abstract: This text maps out the future of supported reagents in their applications as genuine catalysts. It uses examples of supported reagent catalysis to demonstrate the potential of this area of chemistry.

192 citations


Journal ArticleDOI
TL;DR: The number of epsilon-amino groups of lysine present in carrier proteins such as BSA, HSA, thyroglobulin and the enzyme, horseradish peroxidase, were analyzed by the present method and were found to be similar to the reported values.

190 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show that pure liquid water becomes a surprisingly effective medium for the reactions of organic compounds and may function simultaneously as a convenient solvent, catalyst, and reagent for reactions which are typically acid- or base-catalyzed.
Abstract: At high temperatures and pressures, pure liquid water becomes a surprisingly effective medium for the reactions of organic compounds. It may function simultaneously as a convenient solvent, catalyst, and reagent for reactions which are typically acid- or base-catalyzed. Rapid and highly selective conversions are observed for the majority of the compounds in this study

Patent
21 Jul 1994
TL;DR: A potentiometric biosensor, test strip, reagent, and a method for detection or measurement of an analyte from a fluid sample is described in this article. But the method is not suitable for the detection of drugs.
Abstract: A potentiometric biosensor, test strip, reagent, and a potentiometric method for detection or measurement of an analyte from a fluid sample. The biosensor includes indicating (3) and reference electrodes, (5), and a reagent (9), which overlays a portion of the surface of the indicating electrode (3). The reagent generally includes an enzyme and a redox mediator. When a fluid sample (e.g., blood) containing an analyte (e.g., glucose) is added to the reagent, the enzyme (e.g., glucose oxidase) catalyses a reaction involving enzyme, redox mediator (e.g., potassium ferricyanide), and analyze. This reaction may be monitored by monitoring the electrical potential at the indicating electrode surface. The inventive potentiometric biosensor measures the change in potential at the indicating electrode surface after the fluid sample containing the analyze is added to the reagent. The change in potential that occurs may be correlated to the detection or measurement of analyze in the fluid sample.

Book
01 Jan 1994
TL;DR: In this paper, the application of tellurium (Te) compounds as reducing reagents of organic substrates is discussed, where the authors focus on the use of Te reagents in several reduction processes, such as reduction of carbonyl compounds, nitro derivatives, epoxides, aryl alkenes, and aryalkynes.
Abstract: This chapter focuses on the application of tellurium (Te) compounds as reducing reagents of organic substrates Inorganic species—such as hydrogen telluride, sodium hydrogen telluride, sodium telluride—and organic derivatives—such as aryltellurols (and tellurolates) and diorganyl tellurides—are widely employed in several reduction processes—such as reduction of carbonyl compounds, nitro derivatives, epoxides, aryl alkenes, and arylalkynes—as well as in the reductive cleavage of several types of carbon–heteroatom bonds In several cases, the use of Te reagents is clearly advantageous compared to the usual methods because of the mildness of the experimental conditions and the great selectivity The first reported radical reaction promoted by Te reagent was probably the conversion of allylic halides into coupled 1,5-dienes by treatment with telluride anions The reaction, which gives the best results when employing the reagent prepared in situ from elemental Te and lithium triethylborohydride, proceeds through the intermediacy of the thermally unstable bis-allylic telluride, followed by the extrusion of Te and coupling of the formed allylic radicals Additional advantages are the possibility of generating the reducing agents in situ as well in catalytic amounts in the presence of an inexpensive coreductant and the recovery of the Te material

Journal ArticleDOI
Beat Weber1, Dieter Seebach1
TL;DR: In this article, aryl and alkyl triisopropoxy titanium reagents (free of Li, Mg, or Zn salts) are prepared from the corresponding Li or Grignard reagents and ClTi(OiPr)3, with careful removal of salts (centrifugation of LiCl or of dioxane·MgX2, and addition of 12crown-4).

Patent
25 Jul 1994
TL;DR: In this article, an involatile reagent source liquid is flash vaporized on a vaporization matrix structure at elevated temperature, and a carrier gas may be flowed past the flash vaporzation matrix structure to yield a mixture containing the flash-vaporized source reagent.
Abstract: A process and apparatus for delivering an involatile reagent in gaseous form, wherein an involatile reagent source liquid is flash vaporized on a vaporization matrix structure at elevated temperature. A carrier gas may be flowed past the flash vaporzation matrix structure to yield a carrier gas mixture containing the flash vaporized source reagent. The matrix structure preferably has a high surface-to-volume ratio, and may sutiably comprise a foraminous matrix element such as screen mesh onto which the reagent source liquid is distributed for flash vaporization. The invention is particularly useful for delivery of Group II reagents and compounds and complexes of early transition metals such as zirconium and hafnium, and may be usefully employed with Group II beta-diketonate source layers, e.g., of YBaCuO, BiSrCaCuO, and TlBaCaCuO types, as well as for forming interlayers of Group II metal fluorides between superconductor or gallium arsenide overlayers, and for depositing thin films of photonic and ferroelectric materials, e.g., BaTiO 3 , Ba x Sr 1-x Nb 2 O 6 , and PbZr 1-x Ti x O 3 .

Journal ArticleDOI
TL;DR: A mixture of hexafluoroisopropanol-dichloromethane (1:4 v/v) was used in this paper for peptide fragment cleaving.
Abstract: A mixture of hexafluoroisopropanol–dichloromethane (1:4 v/v) acts as a fast, effective and convenient reagent for cleaving protected peptide fragments with a minimal amount of racemization from 2-chlorotrityl chloride resin.



Journal ArticleDOI
01 Jan 1994-Langmuir
TL;DR: In this article, a two-step linker synthesis method was used for the preparation of oriented metalloprotein nanostructures through introduction of specific and complementary reactive groups on the solid and protein surfaces.
Abstract: The preparation of oriented metalloprotein nanostructures through introduction of specific and complementary reactive groups on the solid and protein surfaces is critically dependent on the reaction conditions used to prepare the solid surface. Key problems include the hydrolytic stability of the Si-O bond, the low reactivity of simple nucleophilic silane reagents, protein physisorption, and identification of conditions for producing monolayer protein coverages. These problems are largely circumvented by utilizing a two-step linker synthesis, in which the surface is first prepared with a monolayer of (3-aminopropyl)silane (3-APS), and the resulting structure is derivatized with the heterobifunctional reagent N-succinimidyl 6-maleimidocaproate (EMCS). The maleimide functionality is then presented to the protein, into which a single unique cysteine residue has been introduced by genetic engineering techniques. Hydrolytic stability is dramatically enhanced by including a postreaction curing step, in which the solid surface temperature is elevated to drive the alkoxylsilane condensation reaction to completion. Finally substituting a gas-phase chemical vapor deposition procedure for the liquid-phase reaction of the 3-APS produces dramatically better control over coverage and quality of the resulting films. 23 refs., 4 figs., 2 tabs.

Journal ArticleDOI
TL;DR: In this article, a variety of Hantzsch esters have been oxidized with potassium permanganate, and the structure of the final products dramatically depends on the nature of the 4-substituent and on the experimental conditions.

Patent
21 Jan 1994
TL;DR: In this article, methods for covalently modifying surfaces of various substrates are disclosed, along with various substrate surfaces having surfaces modified by such methods, including polymeric, siliceous, metallic, allotrophic forms of carbon, and semiconductor surfaces.
Abstract: Methods for covalently modifying surfaces of various substrates are disclosed, along with various substrates having surfaces modified by such methods. Candidate surfaces include various polymeric, siliceous, metallic, allotrophic forms of carbon, and semiconductor surfaces. The surfaces are exposed to a reagent, having molecules each comprising a nitrenogenic group and a functionalizing group, in the presence of energized charged particles such as electrons and ions, photons, or heat, which transform the nitrenogenic reagent to a nitrene intermediate. The nitrene covalently reacts with any of various chemical groups present on the substrate surface, thereby effecting nitrene addition of the functionalizing groups to the substrate surface. The functionalizing groups can then participate in downstream chemistry whereby any of a large variety of functional groups, including biological molecules, can be covalently bonded to the surface, thereby dramatically altering the chemical behavior of the surface. Such functionalizations of the surface can be done in a single reactive step or in multiple reactive steps.

Patent
08 Sep 1994
TL;DR: In this article, a dye coupled compound is provided for use in a test device containing a reagent system for detecting the presence or quantity of an analyte in a sample, which comprises one or more enzymes which, in the presence of the analyte, produce an oxidizing agent in quantities indicative of the quantity of analyte.
Abstract: A dye coupled compound is provided for use in a test device containing a reagent system for detecting the presence or quantity of an analyte in a sample. The reagent system comprises one or more enzymes which, in the presence of the analyte, produce an oxidizing agent in quantities indicative of the quantity of analyte in the sample. The compound of choice is meta[3-methyl 2-benzothiazolinone hydrozone]N-sulfonyl benzenesulfonate monosodium.

Journal ArticleDOI
TL;DR: The successful use of Fenton's reagent by a living organism requires a spatial separation between initiating enzyme(s) and the site of production of hydroxyl radicals, and the mobility of the extra electron on Fe(II) by intermolecular transfer may be important for achieving this separation.
Abstract: Many forms of Fe(II) react with H 2 0 2 to generate hydroxyl radicals (Fenton reaction). There is evidence that hydroxyl radicals are important in brown-rot, while they can be formed by secondary reactions during lignin breakdown by white-rot fungi. Their involvement in cellulose breakdown creates a range of oxidized sugars. The two reactants of Fenton's reagent can be generated by Fe(II) autoxidation, or by superoxide in reaction with Fe(III). A rapid autoxidation is not possible for complexes with a high Fe(III)/Fe(II) redox potential. Turning to specific pathways for formation of Fenton's reagent, decomposition of Fe(III)-oxalate is probably solely a photochemical process. Lignin peroxidases can act indirectly as a source of superoxide, either by reactions that lead to a peroxyradical, or by 1-electron oxidation of an aliphatic compound creating a strong reductant. Cellobiose dehydrogenase can provide a direct enzymic source for Fenton's reagent (S.M. Kremer and P.M. Wood (1992) Eur. J. Biochem. 208, 807–814). In the experiments as published, hydroxyl radical production was limited by the slow interaction of cellobiose dehydrogenase with O 2 . This limitation can be removed by the presence of an iron complex with an autoxidizable Fe(lI) state. The successful use of Fenton's reagent by a living organism requires a spatial separation between initiating enzyme(s) and the site of production of hydroxyl radicals. The mobility of the extra electron on Fe(II) by intermolecular transfer may be important for achieving this separation.

Journal ArticleDOI
Ákos Bartha1, Jan Ståhlberg1
TL;DR: In this paper, the theoretical foundation of the electrostatic theory of ion-pair chromatography derives from colloid and surface chemistry, and the basic concepts of the theory are discussed with emphasis on the physical principles.

Journal ArticleDOI
TL;DR: The usefulness of the TMAD reagent was demonstrated by the highly efficient two-step synthesis of benzylcrotylamine from N-benzyltrifluoroacetamide, when used in combination with tributylphosphine in benzene.
Abstract: N,N,N′,N′-Tetramethylazodicarboxamide, TMAD, was found to be more versatile in the Mitsunobu reaction than traditional diethyl azodicarboxylate or recently developed 1,1′-(azodicarbonyl)dipiperidine, when used in combination with tributylphosphine in benzene. The usefulness of the reagent was demonstrated by the highly efficient two-step synthesis of benzylcrotylamine from N-benzyltrifluoroacetamide.

Journal ArticleDOI
TL;DR: A number of geochemically relevant model compounds (alkenes, ketones, aldehydes, acids, alcohols and esters) have been subjected to a reaction with sodium hydrogen polysulphide either in one solvent or mediated by a phase transfer reagent as discussed by the authors.

Patent
18 May 1994
TL;DR: In this paper, a film for releasing at least one of an anti-microbial agent, oxygen, and a medicament includes a flexible, porous layer such as a woven, non-woven, or knitted cloth or a layer of open cell foam.
Abstract: A film for releasing at least one of an anti-microbial agent, oxygen, and a medicament includes a flexible, porous layer (18) such as a woven, non-woven, or knitted cloth or a layer of open cell foam. A first dry reagent (12) and a second dry reagent (14) which react in the presence of a dilutant to form the anti-microbial agent, oxygen, or medicament attached to the flexible, porous layer. In one preferred embodiment, the two dry reagents are disposed on opposite sides of the flexible, porous layer such that the flexible porous layer keeps the two apart and prevents a premature reaction. Porous outer layers (20, 22) prevent the powdered reagents from being wiped off while permitting dilutant access. In a preferred embodiment, the powdered reagents include acetylsalicylic acid and a perborate which react in the presence of water to generate peracetic acid (an antimicrobial agent which breaks down in a matter of minutes to hours into oxygen) and salicylic acid (a topical keratotic). The rate at which the reaction occurs and the peracetic acid breaks down into oxygen is controlled by buffering the pH of the powdered reagents, by selectively micro-encapsulating the powdered reagents, by controlling the porosity of the layers, or the like. Optionally, surfactants, detergents, emollients, gels, and the like can be added to the dry reagents. Alternately, a single reagent which releases oxygen or forms a strong oxidant may be used.

Patent
07 Nov 1994
TL;DR: In this article, an automated multi-test capability assay or reaction apparatus in modular form, comprising a reagent and an assay sample storage module (2,3), an incubation module (11), a reaction detection/measurement module (17), and a module (16) for independently and, as desired, both transporting an incubator container (58) between the incubation, and reaction detection, measuring, and transferring reagent(s) and/or assay sample (s) between different modules without reagent, intended for different tests or reactions.
Abstract: The invention provides an assay or reaction apparatus of modular construction permitting true random operation at the discretion of the user. The apparatus is an automated multi-test capability assay or reaction apparatus (1) in modular form, comprising a reagent and an assay sample storage module (2,3), an incubation module (11), a reaction detection/measurement module (17), and a module (16) for independently and, as desired, both transporting an incubation container (58) between the incubation module (11) and reaction detection/measurement module (17), and transferring reagent(s) and/or assay sample(s) between different modules without reagent(s) and/or assay sample(s) intended for different tests or reactions.

Journal ArticleDOI
TL;DR: Zerovalent Pd(Ar-BIAN) and divalent PdCl2(Ar)-BIAN are efficient catalysts for the cross coupling reaction of various organic halides (including acyl-, allyl-, aryl-, benzyl-, vinyl- and 1,2-dienylhalides) with organomagnesium, -zinc and -tin reagents as discussed by the authors.

PatentDOI
20 Oct 1994-Analyst
TL;DR: In this article, a method and apparatus for the detection of hydrazine, monomethylhydrazine and 1,1-dimethylhydrazines in air (or other gas medium) or in an aqueous solution is presented.
Abstract: A method and apparatus for the detection of hydrazine, monomethylhydrazine, 1,1-dimethylhydrazine in air (or other gas medium) or in an aqueous solution. The detection is accomplished by introducing a stream of air, or other gas medium, or aqueous solution suspected of containing hydrazine, monomethylhydrazine, 1,1-dimethylhydrazine or mixtures thereof into a pH controlled reagent solution containing an aromatic dicarboxaldehyde to react with the hydrazine, monomethylhydrazine, 1,1-dimethylhydrazine or mixtures thereof, respectively, and by exposing the reacted reagent solution to an excitation wavelength range and monitoring an emission from the exposed reagent solution at an emission wavelength range to detect the presence of a hydrazine derivative, monomethylhydrazine derivative, 1,1-dimethylhydrazine derivative, or mixtures thereof (i.e. a derivative formed by the reaction between hydrazine, monomethylhydrazine, 1,1-dimethylhydrazine and the aromatic dicarboxaldehyde) indicating the presence of hydrazine, monomethylhydrazine, 1,1-dimethylhydrazine or mixtures thereof within the stream of air or other gas medium or aqueous solution.