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排序方式: 共有1247条查询结果,搜索用时 15 毫秒
1.
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
2.
Back Cover: Selective Aromatic Hydroxylation with Dioxygen and Simple Copper Imine Complexes (Chem. Eur. J. 33/2015) 下载免费PDF全文
3.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
4.
Lars J. Wesenberg Erika Diehl Till J. B. Zähringer Carolin Dörr Dr. Dieter Schollmeyer Dr. Akihiro Shimizu Prof. Dr. Jun-ichi Yoshida Prof. Dr. Ute A. Hellmich Prof. Dr. Siegfried R. Waldvogel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17574-17580
The efficient production of many medicinally or synthetically important starting materials suffers from wasteful or toxic precursors for the synthesis. In particular, the aromatic non-protected primary amine function represents a versatile synthetic precursor, but its synthesis typically requires toxic oxidizing agents and transition metal catalysts. The twofold electrochemical amination of activated benzene derivatives via Zincke intermediates provides an alternative sustainable strategy for the formation of new C−N bonds of high synthetic value. As a proof of concept, we use our approach to generate a benzoxazinone scaffold that gained attention as a starting structure against castrate-resistant prostate cancer. Further improvement of the structure led to significantly increased cancer cell line toxicity. Thus, exploiting environmentally benign electrooxidation, we present a new versatile and powerful method based on direct C−H activation that is applicable for example the production of medicinally relevant compounds. 相似文献
5.
Philipp Rietsch Dr. Sebastian Sobottka Dr. Katrin Hoffmann Dr. Alexey A. Popov Pascal Hildebrandt Prof. Dr. Biprajit Sarkar Dr. Ute Resch-Genger Prof. Dr. Siegfried Eigler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(72):17361-17365
Reversibly switching the light absorption of organic molecules by redox processes is of interest for applications in sensors, light harvesting, smart materials, and medical diagnostics. This work presents a symmetrical benzothiadiazole (BTD) derivative with a high fluorescence quantum yield in solution and in the crystalline state and shows by spectroelectrochemical analysis that reversible switching of UV absorption in the neutral state, to broadband Vis/NIR absorption in the 1st oxidized state, to sharp band Vis absorption in the 2nd oxidized state, is possible. For the one-electron oxidized species, formation of a delocalized radical is confirmed by electron paramagnetic resonance spectroelectrochemistry. Furthermore, our results reveal an increasing quinoidal distortion upon the 1st and 2nd oxidation, which can be used as the leitmotif for the development of BTD based redox switches. 相似文献
6.
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
7.
Michael Berger Marola S. Lenhard Prof. Dr. Siegfried R. Waldvogel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(41):e202201029
The para-selective fluorination reaction of anilides using electrochemically generated hypervalent ArIF2 is reported, with Et3N ⋅ 5HF serving as fluoride source and as supporting electrolyte. This electrochemical reaction is characterized by a simple set-up, easy scalability and affords a broad variety of fluorinated anilides from easily accessible anilides in good yields up to 86 %. 相似文献
8.
在材料研制中的连续介质细观力学有限元建模现状评论(译文) 总被引:5,自引:1,他引:5
评述了机械载荷下材料力学行为有限元模拟的先进技术.分析
了考虑材料微观及细观结构情况下,对材料变形、损伤、断裂进行模
拟时各种方法的优缺点及发展前景.阐述了对材料行为模拟方法的发
展,包括基本的及先进的方法,如体胞方法、真实结构模拟、粘结区
模型等.分析了在先进新材料的开发中运用有限元方法的可能性 相似文献
9.
Zusammenfassung Die Rotationsumwandlung der n-Paraffine wird als Übergang eines Paraffinkristalls mit 2gl-Kinken als Baufehler in einen Kinkblockkristall theoretisch behandelt. Die dabei mit zwei Methoden diskutierten Näherungen — für kurze und für sehr lange Ketten — liefern Aussagen über Umwandlungstemperatur, Umwandlungswärme und Volumensprung, die den experimentellen Werten entsprechen, die Kettenlängenabhängigkeit annähernd beschreiben und die Konzentrationsabhängigkeit der Umwandlungstemperatur sowie der Umwandlungswärme in Paraffinmischungen richtig wiedergeben.Vorgetragen auf der Jahrestagung der Deutschen Rheologen in Berlin-Dahlem vom 7.–10. Juni 1966.Herrn Prof.H. O. Kneser danken wir für die Förderung dieser Arbeit, der Deutschen Forschungsgemeinschaft für finanzielle Unterstützung. 相似文献
10.
Dr. Patrick Feicht Dr. Johannes Biskupek Dr. Tatiana E. Gorelik Julian Renner Dr. Christian E. Halbig Maria Maranska Florian Puchtler Prof. Dr. Ute Kaiser Prof. Dr. Siegfried Eigler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(38):8955-8959
Synthesis and studies of graphite oxide started more than 150 years ago and turned into a boom by the measurements of the outstanding physical properties of graphene. A series of preparation protocols emanated trying to optimize the synthesis of graphene oxide in order to obtain a less defective material, as source for graphene. However, over-oxidation of the carbon framework hampered establishing structure-property relationships. Here, the fact that two different synthetic methods for graphene oxide preparation lead to very similar types of graphene oxide with a preserved graphene lattice is demonstrated. Either sodium chlorate in nitric acid (similar to Brodie's method) or potassium permanganate in sulfuric acid (similar to Hummers’ method) treatment are possible; however, reaction conditions must be controlled. With a preserved carbon lattice analytical differences between the samples relate to the altered on-plane functionality. Consequently, terming preparation protocols “according to Brodie's/Hummers’ method” is not sufficient. 相似文献