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[reaction: see text] The first examples of free radical-mediated vinyl amination are described by nonconventional vinyl radical addition to azomethine nitrogen. This new vinyl amination protocol is mild and provides convenient synthetic access to nonstabilized N,N-dialkyl enamines and tandem bond-forming processes. 相似文献
23.
Handley LL Johnston AM Hallett PD Scrimgeour CM Wheatley RE 《Rapid communications in mass spectrometry : RCM》2001,15(15):1274-1278
New evidence, obtained using a robust method for measuring the delta(15)N of NO(3)(-)-N in soil, is consistent with denitrification being the major determinant in the vertical distribution of NO(3)(-)-delta(15)N in soil profiles. These data also suggest that varying moisture regimes result in different effects of soil NO(3)(-)-N leaching on residual whole soil delta(15)N. 相似文献
24.
A straightforward synthesis of aziridines is reported from an electron-rich azide (alkyl or aryl azide), electron-deficient olefin, and triflic acid in cold acetonitrile. The only coproduct of the reaction is dinitrogen (N2). Active ester substrates bearing a nucleophilic carbonyl engage the putative protonated aziridine intermediate to produce the product of olefin aminohydroxylation in which the nitrogen is benzyl protected and the oxygen is acylated. The possibility that a triazoline need not be an intermediate in aziridine production is advanced. 相似文献
25.
George J. Ellames David Johnston David I. Smith 《Journal of heterocyclic chemistry》1990,27(4):1091-1093
Pyrrolosteroids such as 17β-hydroxy-1′-H-5α-androst-2-eno[3,2-b]pyrrole ( 1 ) and the novel 17β-hydroxy-1′-H-5α-androst-3-eno[3,4-b]pyrrole ( 12 ) can be synthesized from the corresponding O-(2-hydroxyethyl)ketoxime precursors. In the case of 1 , yields compare favourably with previously reported literature methods. 相似文献
26.
Battersby BJ Lawrie GA Johnston AP Trau M 《Chemical communications (Cambridge, England)》2002,(14):1435-1441
The enormous amount of information generated through sequencing of the human genome has increased demands for more economical and flexible alternatives in genomics, proteomics and drug discovery. Many companies and institutions have recognised the potential of increasing the size and complexity of chemical libraries by producing large chemical libraries on colloidal support beads. Since colloid-based compounds in a suspension are randomly located, an encoding system such as optical barcoding is required to permit rapid elucidation of the compound structures. We describe in this article innovative methods for optical barcoding of colloids for use as support beads in both combinatorial and non-combinatorial libraries. We focus in particular on the difficult problem of barcoding extremely large libraries, which if solved, will transform the manner in which genomics, proteomics and drug discovery research is currently performed. 相似文献
27.
Johnston AM Scrimgeour CM Kennedy H Handley LL 《Rapid communications in mass spectrometry : RCM》2003,17(11):1099-1106
The conversion of ammonium (NH(4) (+)) to 1-sulfonato-iso-indole has been examined as a method for natural abundance measurement of delta(15)N of NH(4) (+). The reaction is complete within 2 h and is based on the derivatisation of NH(4) (+) by o-phthaldialdehyde and sodium sulfite at a high pH, 11.2. The product is readily concentrated from dilute solutions by reverse-phase solid-phase extraction (SPE). The method is compound-specific despite partial derivatisation of potentially interfering amino acids, as their derivatives are not extracted by SPE. delta(15)N values of NH(4) (+) in KCL soil extracts can be measured within 48 h by automated continuous-flow IRMS with a precision of 0.23 per thousand (1 SD). Parallel measurements of NH(4) (+) standards of known delta(15)N are made to allow correction for the isotopic dilution by non-sample NH(4) (+). The practicality of this method is demonstrated by measuring the changes in NH(4) (+) concentration and delta(15)N following the addition of urea as a nitrogen source to inorganic N-depleted soil. 相似文献
28.
Yeung LK Lee CT Johnston KP Crooks RM 《Chemical communications (Cambridge, England)》2001,(21):2290-2291
Dendrimer-encapsulated nanoparticles are shown to be versatile catalysts for both the hydrogenation of styrene and Heck heterocoupling of iodobenzene and methacrylate in supercritical CO2 (scCO2). 相似文献
29.
Dickson JL Binks BP Johnston KP 《Langmuir : the ACS journal of surfaces and colloids》2004,20(19):7976-7983
Stable carbon dioxide-in-water emulsions were formed with silica nanoparticles adsorbed at the interface. The emulsion stability and droplet size were characterized with optical microscopy, turbidimetry, and measurements of creaming rates. The increase in the emulsion stability as the silica particle hydrophilicity was decreased from 100% SiOH to 76% SiOH is described in terms of the contact angles and the resulting energies of attachment for the silica particles at the water-CO(2) interface. The emulsion stability also increased with an increase in the particle concentration, CO(2) density, and shear rate. The dominant destabilization mechanism was creaming, whereas flocculation, coalescence, and Ostwald ripening played only a minor role over the CO(2) densities investigated. The ability to stabilize these emulsions with solid particles at CO(2) densities as low as 0.739 g/mL is particularly relevant in practical applications, given the difficulty in stabilizing these emulsions with surfactants, because of the unusually weak solvation of the surfactant tails by CO(2). 相似文献
30.