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201.
Maurice Dörr Sebastian Lips Prof. Dr. Carlos Alberto Martínez-Huitle Dr. Dieter Schollmeyer Prof. Dr. Robert Franke Prof. Dr. Siegfried R. Waldvogel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7835-7838
We report an innovative, sustainable and straightforward protocol for the synthesis of N,N-diarylamides equipped with nonprotected hydroxyl groups by using electrosynthesis. The concept allows the application of various substrates furnishing diarylamides with yields up to 57 % within a single and direct electrolytic protocol. The method is thereby easy to conduct in an undivided cell with constant current conditions offering a versatile and short-cut alternative to conventional pathways. 相似文献
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203.
Sebastian B. Beil Timo Müller Sydney B. Sillart Peter Franzmann Alexander Bomm Michael Holtkamp Prof. Dr. Uwe Karst Prof. Dr. Wolfgang Schade Prof. Dr. Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2018,57(9):2450-2454
A new and powerful active anode system that can be operated in 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) has been discovered. In HFIP the molybdenum anode forms a compact, conductive, and electroactive layer of higher‐valent molybdenum species. This system can replace powerful but stoichiometrically required MoV reagents for the dehydrogenative coupling of aryls. This electrolytic reaction is more sustainable and allows the conversion of a broad scope of activated arenes. 相似文献
204.
Anton Wiebe Tile Gieshoff Sabine Möhle Dr. Eduardo Rodrigo Michael Zirbes Prof. Dr. Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2018,57(20):5594-5619
The direct synthetic organic use of electricity is currently experiencing a renaissance. More synthetically oriented laboratories working in this area are exploiting both novel and more traditional concepts, paving the way to broader applications of this niche technology. As only electrons serve as reagents, the generation of reagent waste is efficiently avoided. Moreover, stoichiometric reagents can be regenerated and allow a transformation to be conducted in an electrocatalytic fashion. However, the application of electroorganic transformations is more than minimizing the waste footprint, it rather gives rise to inherently safe processes, reduces the number of steps of many syntheses, allows for milder reaction conditions, provides alternative means to access desired structural entities, and creates intellectual property (IP) space. When the electricity originates from renewable resources, this surplus might be directly employed as a terminal oxidizing or reducing agent, providing an ultra‐sustainable and therefore highly attractive technique. This Review surveys recent developments in electrochemical synthesis that will influence the future of this area. 相似文献
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206.
We prove the existence of multiple constant-sign and sign-changing solutions for a nonlinear elliptic eigenvalue problem under Dirichlet boundary condition involving the p-Laplacian. More precisely, we establish the existence of a positive solution, of a negative solution, and of a nontrivial sign-changing solution when the eigenvalue parameter λ is greater than the second eigenvalue λ2 of the negative p-Laplacian, extending results by Ambrosetti–Lupo, Ambrosetti–Mancini, and Struwe. Our approach relies on a combined use of variational and topological tools (such as, e.g., critical points, Mountain-Pass theorem, second deformation lemma, variational characterization of the first and second eigenvalue of the p-Laplacian) and comparison arguments for nonlinear differential inequalities. In particular, the existence of extremal nontrivial constant-sign solutions plays an important role in the proof of sign-changing solutions. 相似文献
207.
Dochnahl M Löhnwitz K Pissarek JW Roesky PW Blechert S 《Dalton transactions (Cambridge, England : 2003)》2008,(21):2844-2848
The electronically modified zinc complex 5-phenylsulfanyl-N-isopropyl-2-(isopropylamino)troponiminate zinc methyl, [(PhS-ATI(iPr)2)ZnMe], was synthesized. It showed an increased reactivity in the intramolecular hydroamination reaction of non-activated alkenes compared to a previously-reported, non-substituted complex. 相似文献
208.
Michael Zirbes Dr. Tobias Graßl Rieke Neuber Prof. Dr. Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2023,62(14):e202219217
Lignin, the world's largest resource of renewable aromatics, with annually roughly 50 million tons of accruing technical lignin, mainly Kraft lignin, is highly underdeveloped regarding the production of monoaromatics. We demonstrate the oxidative depolymerization of Kraft lignin at 180 °C to produce vanillin 1 in yields up to 6.2 wt % and 92 % referred to the maximum yield gained from the quantification reaction utilizing nitrobenzene. Using peroxodicarbonate (C2O62−) as “green” oxidizer for the degradation, toxic and/or harmful reagents are prevented. Also, the formed waste can serve as makeup chemical in the pulping process. Na2C2O6 is synthesized in an ex-cell electrolysis of aqueous Na2CO3 at BDD anodes, achieving a yield of Na2C2O6 with 41 %. At least, the oxidation and degradation of Kraft lignin is analysis via UV/Vis and NMR spectroscopy. 相似文献
209.
210.
E.?V.?AltynbaevEmail author A.?S.?Sukhanov S.-A.?Siegfried V.?A.?Dyadkin E.?V.?Moskvin D.?Menzel A.?Heinemann A.?Schreyer L.?N.?Fomicheva A.?V.?Tsvyashenko S.?V.?Grigoriev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2016,10(4):777-782
The helicoidal magnetic structure of a MnGe compound doped with 25% Fe is studied by means of small-angle neutron scattering in a wide temperature range of 10–300 K. Analysis of the scattering-function profile demonstrates that magnetic structures inherent to both pure MnGe and its doped compounds are unstable. The doping of manganese monogermanide is revealed to lead to higher destabilization of the magnetic system. In passing from MnGe to Mn0.75Fe0.25Ge, the magnetic-ordering temperature T N decreases from 130 to 95 K, respectively. It is demonstrated that, at temperatures close to 0 K, the intensity of the contribution to scattering from stable spin helices decreases and the intensity of scattering by spin helix fluctuations increases with increasing impurity-metal concentration. An increased intensity of anomalous scattering caused by spin excitations existing in the system is observed. Helicoidal fluctuations and spin excitations corresponding to low temperatures indicate the quantum nature of the instability in the doped compound. However, MnGe doping with Fe atoms has no influence on the compound’s magnetic properties at temperatures of higher than T N. The temperature range of short-range ferromagnetic correlations is independent of concentrations and is restricted by temperatures T ranging from 175 to 300 K. 相似文献