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- ItemAmbient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core-Shell Catalyst(Weinheim : Wiley-VCH, 2021) Gao, Jie; Ma, Rui; Feng, Lu; Liu, Yuefeng; Jackstell, Ralf; Jagadeesh, Rajenahally V.; Beller, MatthiasA general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
- ItemLigand-Controlled Palladium-Catalyzed Carbonylation of Alkynols : Highly Selective Synthesis of α-Methylene-β-Lactones(Weinheim : Wiley-VCH, 2020) Ge, Yao; Ye, Fei; Liu, Jiawang; Yang, Ji; Spannenberg, Anke; Jiao, Haijun; Jackstell, Ralf; Beller, MatthiasThe first general and regioselective Pd-catalyzed cyclocarbonylation to give α-methylene-β-lactones is reported. Key to the success for this process is the use of a specific sterically demanding phosphine ligand based on N-arylated imidazole (L11) in the presence of Pd(MeCN)2Cl2 as pre-catalyst. A variety of easily available alkynols provide under additive-free conditions the corresponding α-methylene-β-lactones in moderate to good yields with excellent regio- and diastereoselectivity. The applicability of this novel methodology is showcased by the direct carbonylation of biologically active molecules including natural products. © 2020 The Authors. Published by Wiley-VCH GmbH
- ItemSynthesis of 3,4-Dihydro-2H-Pyrroles from Ketones, Aldehydes, and Nitro Alkanes via Hydrogenative Cyclization(Weinheim : Wiley-VCH, 2022) Klausfelder, Barbara; Blach, Patricia; de Jonge, Niels; Kempe, RhettSyntheses of N-heterocyclic compounds that permit a flexible introduction of various substitution patterns by using inexpensive and diversely available starting materials are highly desirable. Easy to handle and reusable catalysts based on earth-abundant metals are especially attractive for these syntheses. We report here on the synthesis of 3,4-dihydro-2H-pyrroles via the hydrogenation and cyclization of nitro ketones. The latter are easily accessible from three components: a ketone, an aldehyde and a nitroalkane. Our reaction has a broad scope and 23 of the 33 products synthesized are compounds which have not yet been reported. The key to the general hydrogenation/cyclization reaction is a highly active, selective and reusable nickel catalyst, which was identified from a library of 24 earth-abundant metal catalysts.
- ItemSteering carbon dioxide reduction toward C–C coupling using copper electrodes modified with porous molecular films([London] : Nature Publishing Group UK, 2023) Zhao, Siqi; Christensen, Oliver; Sun, Zhaozong; Liang, Hongqing; Bagger, Alexander; Torbensen, Kristian; Nazari, Pegah; Lauritsen, Jeppe Vang; Pedersen, Steen Uttrup; Rossmeisl, Jan; Daasbjerg, KimCopper offers unique capability as catalyst for multicarbon compounds production in the electrochemical carbon dioxide reduction reaction. In lieu of conventional catalysis alloying with other elements, copper can be modified with organic molecules to regulate product distribution. Here, we systematically study to which extent the carbon dioxide reduction is affected by film thickness and porosity. On a polycrystalline copper electrode, immobilization of porous bipyridine-based films of varying thicknesses is shown to result in almost an order of magnitude enhancement of the intrinsic current density pertaining to ethylene formation while multicarbon products selectivity increases from 9.7 to 61.9%. In contrast, the total current density remains mostly unaffected by the modification once it is normalized with respect to the electrochemical active surface area. Supported by a microkinetic model, we propose that porous and thick films increase both local carbon monoxide partial pressure and the carbon monoxide surface coverage by retaining in situ generated carbon monoxide. This reroutes the reaction pathway toward multicarbon products by enhancing carbon–carbon coupling. Our study highlights the significance of customizing the molecular film structure to improve the selectivity of copper catalysts for carbon dioxide reduction reaction.
- ItemLayered Nano‐Mosaic of Niobium Disulfide Heterostructures by Direct Sulfidation of Niobium Carbide MXenes for Hydrogen Evolution(Weinheim : Wiley-VCH, 2022) Husmann, Samantha; Torkamanzadeh, Mohammad; Liang, Kun; Majed, Ahmad; Dun, Chaochao; Urban, Jeffrey J.; Naguib, Michael; Presser, VolkerMXene-transition metal dichalcogenide (TMD) heterostructures are synthesized through a one-step heat treatment of Nb2C and Nb4C3. These MXenes are used without delamination or any pre-treatment. Heat treatments accomplish the sacrificial transformation of these MXenes into TMD (NbS2) at 700 and 900 °C under H2S. This work investigates, for the first time, the role of starting MXene phase in the derivative morphology. It is shown that while treatment of Nb2C at 700 °C leads to the formation of pillar-like structures on the parent MXene, Nb4C3 produces nano-mosaic layered NbS2. At 900 °C, both MXene phases, of the same transition metal, fully convert into nano-mosaic layered NbS2 preserving the parent MXene's layered morphology. When tested as electrodes for hydrogen evolution reaction, Nb4C3-derived hybrids show better performance than Nb2C derivatives. The Nb4C3-derived heterostructure exhibits a low overpotential of 198 mV at 10 mA cm−2 and a Tafel slope of 122 mV dec−1, with good cycling stability in an acidic electrolyte.
- Item2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2021) Tka, Najeh; Ayed, Mohamed Adnene Hadj; Braiek, Mourad Ben; Jabli, Mahjoub; Chaaben, Noureddine; Alimi, Kamel; Jopp, Stefan; Langer, PeterAcridine derivatives have attracted considerable interest in numerous areas owing to their attractive physical and chemical properties. Herein, starting from readily available anthranilic acid, an efficient synthesis of 2,4-bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridine derivatives was accomplished via a one-pot double Sonogashira cross-coupling method. The UV-visible absorption and emission properties of the synthesized molecules have been examined. Additionally, theoretical studies based on density functional theory (DFT/B3LYP/6-31G(d)) were carried out.