排序方式: 共有12条查询结果,搜索用时 31 毫秒
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Nicholas D. C. Tappin Weronika Michalska Simon Rohrbach Philippe Renaud 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14378-14382
An operationally simple method to affect an atom‐transfer radical addition of commercially available ICH2Bpin to terminal alkenes has been developed. The intermediate iodide can be transformed in a one‐pot process into the corresponding cyclopropane upon treatment with a fluoride source. This method is highly selective for the cyclopropanation of unactivated terminal alkenes over non‐terminal alkenes and electron‐deficient alkenes. Due to the mildness of the procedure, a wide range of functional groups such as esters, amides, alcohols, ketones, and vinylic cyclopropanes are well tolerated. 相似文献
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Beaumont S Ilardi EA Tappin ND Zakarian A 《European journal of organic chemistry》2010,2010(30):5743-5765
This microreview provides a compilation of synthetic approaches and total syntheses of pinnatoxin A in a survey of the literature up to early 2010. Pinnatoxin A is the first discovered and representative member of a fascinating group of potent marine toxins that share a spiroimine subunit as a unifying structural element. 相似文献
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Analysis of a TE011 mode composite sapphire-rutile dielectric resonator has been carried out to study the temperature variation of resonance
frequency, close to the Cs atomic clock hyperfine frequency of 9.192 GHz. The complementary behavior of dielectric permittivity
with temperature of the composite has been exploited to obtain the desired turning point in the resonant frequency. The frequency
of the composite structure is found to be independent of the shield diameter beyond four times the puck diameter. 相似文献
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Emy Andr‐Joyaux Andrey Kuzovlev Nicholas D. C. Tappin Philippe Renaud 《Angewandte Chemie (International ed. in English)》2020,59(33):13859-13864
The generation of carbon‐centered radicals from air‐sensitive organoboron compounds through nucleohomolytic substitution at boron is a general method to generate non‐functionalized and functionalized radicals. Due to their reduced Lewis acidity, alkylboronic pinacol esters are not suitable substrates. We report their in situ conversion into alkylboronic catechol esters by boron‐transesterification with a substoichiometric amount of catechol methyl borate combined with an array of radical chain processes. This simple one‐pot radical‐chain deboronative method enables the conversion of pinacol boronic esters into iodides, bromides, chlorides, and thioethers. The process is also suitable the formation of nitriles and allylated compounds through C?C bond formation using sulfonyl radical traps. The power of combining radical and classical boron chemistry is illustrated with a modular 5‐membered ring formation using a combination of three‐component coupling and protodeboronative cyclization. 相似文献
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Howell KA Achterberg EP Braungardt CB Tappin AD Turner DR Worsfold PJ 《The Analyst》2003,128(6):734-741
This work presents the optimisation, validation and field deployment of a voltammetric in situ profiling (VIP) system for the simultaneous determinations of dynamic Cd(II), Cu(II) and Pb(II) in estuarine and coastal waters. Systematic studies in NaNO3 (as a supporting electrolyte) and seawater, indicated that variations in ionic strength, pH and dissolved oxygen did not affect the response of the instrument, whereas an Arrhenius type temperature response was observed. The VIP instrument allows the determination of 2-3 samples h(-1), and has a detection limit (defined as 3sigma) in seawater for Cd(II): 23 pM, Cu(II): 1.13 nM, and Pb(II): 23 pM. The VIP system accurately measured the total dissolved concentrations of Cd(II), Cu(II) and Pb(II) in two certified reference materials; SLRS-3, a river water, and SLEW-2, an estuarine water. Field evaluation of the instrumentation and analytical methods was achieved through a series of surveys in the Plym Estuary (Devon, UK), from which environmental data are presented. 相似文献
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L. C. Norte E. M. de Carvalho M. R. R. Tappin P. P. Borges 《Journal of Solid State Electrochemistry》2018,22(5):1413-1419
The use of pure materials in chemical analysis is currently in high demand due to the need to provide reliable measurement results. Phytotherapics are natural products that contain substances of secondary vegetal metabolism. Perillic acid, a monoterpenic acid with anti-inflammatory and anticancer properties, was the phytotherapic chosen to be analyzed in this work for purity by coulometry. Due to the low availability of perillic acid on the market and its high cost, the miniaturization of the coulometric technique was fundamental for characterizing such a substance. The volume of the supporting electrolyte and the mass of the analyte were the main parameters scaled. The coulometric measurement results were obtained by small-scale coulometry by using 3.0 mg of perillic acid (scale reduction of ×100). A mean purity of (94.2 ± 0.8)% (k = 2.13, for an approximately 95% confidence level) was obtained from five replicates. These studies aim in the future to develop the production of certified reference materials from natural products. 相似文献