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31.
Dr. Pavlo Nikolaienko Marc Jentsch Dr. Ajit P. Kale Dr. Yunfei Cai Prof. Dr. Magnus Rueping 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(29):7177-7184
A hydrogen atom transfer-directed electrochemical intramolecular C−H amination has been developed in which the N-radical species are generated at the anode, and the base required for the reaction is generated at the cathode. A broad range of valuable pyrrolidines were prepared in good yields and with high chemoselectivity. The reaction was easily scaled up in both batch and continuous flow systems. 相似文献
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Matthias Müller Dr. Magnus R. Buchner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):9915-9922
The first synthesis of BePh2 was accomplished almost a century ago. However, its structure has remained unknown so far, while the corresponding aryls of the elements adjacent to beryllium in the periodic table are well investigated. Herein, we present an improved synthesis for diphenylberyllium and show by X-ray diffraction that it forms a trinuclear complex in the solid state. NMR spectroscopy revealed that this structure is also retained in solution but exhibits dynamic behavior. Its stability against heat and coordinating solvents is discussed and the possible obstacles to the synthesis of BePh2 from BeCl2 are examined. In the process of this study two ether adducts, BePh2⋅Et2O and Be2Ph4⋅Et2O, have been characterized as well as the previously unknown triphenylberyllate anion. From the latter several single-crystal structures were obtained under various conditions, in which [BePh3]− is either isolated or acts as a ligand for Li+. Furthermore, the crown ether induced selfionization of BePh2 is described and the resulting [(12-crown-4)BePh]+ cation was isolated, which shows an unusual 4+1 coordination around the Be atom. 相似文献
34.
Path coupling is a useful technique for simplifying the analysis of a coupling of a Markov chain. Rather than defining and analysing the coupling on every pair in Ω×Ω, where Ω is the state space of the Markov chain, analysis is done on a smaller set SΩ×Ω. If the coefficient of contraction β is strictly less than one, no further analysis is needed in order to show rapid mixing. However, if β=1 then analysis (of the variance) is still required for all pairs in Ω×Ω. In this paper we present a new approach which shows rapid mixing in the case β=1 with a further condition which only needs to be checked for pairs in S, greatly simplifying the work involved. We also present a technique applicable when β=1 and our condition is not met. 相似文献
35.
Let f be a transcendental entire function for which the set of critical and asymptotic values is bounded. The Denjoy–Carleman–Ahlfors
theorem implies that if the set of all z for which |f(z)| > R has N components for some R > 0, then the order of f is at least N/2. More precisely, we have log log M(r, f) ≥ (N/2) log r − O(1), where M(r, f) denotes the maximum modulus of f. We show that if f does not grow much faster than this, then the escaping set and the Julia set of f have positive Lebesgue measure. However, as soon as the order of f exceeds N/2, this need not be true. The proof requires a sharpened form of an estimate of Carleman and Tsuji related to the Denjoy–Carleman–Ahlfors
theorem. 相似文献
36.
Theoretical stability,thin film synthesis and transport properties of the Mon +1GaCn MAX phase 下载免费PDF全文
Rahele Meshkian Arni Sigurdur Ingason Martin Dahlqvist Andrejs Petruhins Unnar B. Arnalds Fridrik Magnus Jun Lu Johanna Rosen 《固体物理学:研究快报》2015,9(3):197-201
The phase stability of Mon +1GaCn has been investigated using ab‐initio calculations. The results indicate stability for the Mo2GaC phase only, with a formation enthalpy of –0.4 meV per atom. Subsequent thin film synthesis of Mo2GaC was performed through magnetron sputtering from elemental targets onto Al2O3 [0001], 6H‐SiC [0001] and MgO [111] substrates within the temperature range of 500 °C and 750 °C. High structural quality films were obtained for synthesis on MgO [111] substrates at 590 ºC. Evaluation of transport properties showed a superconducting behavior with a critical temperature of approximately 7 K, reducing upon the application of an external magnetic field. The results point towards the first superconducting MAX phase in thin film form. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
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We describe the functions needed in the determination of the rate of convergence of best $L^\infty $ rational approximation to $\exp ( - x)$ on [0,∞) when the degree n of the approximation tends to ∞ (“1/9” problem). 相似文献
39.
Jan Sklyaruk Jannik C. Borghs Osama El‐Sepelgy Magnus Rueping 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(3):785-789
A metal‐catalyzed methylation process has been developed. By employing an air‐ and moisture‐stable manganese catalyst together with isotopically labeled methanol, a series of D‐, CD3‐, and 13C‐labeled products were obtained in good yields under mild reaction conditions with water as the only byproduct. 相似文献
40.
Marc Magre Bholanath Maity Alban Falconnet Luigi Cavallo Magnus Rueping 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(21):7099-7103
A magnesium‐catalyzed hydroboration of alkynes providing good yields and selectivities for a wide range of terminal and symmetrical and unsymmetrical internal alkynes has been developed. The compatibility with many functional groups makes this magnesium catalyzed procedure attractive for late stage functionalization. Experimental mechanistic investigations and DFT calculations reveal insights into the reaction mechanism of the magnesium catalyzed protocol. 相似文献