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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
- ItemTailored Palladium Catalysts for Selective Synthesis of Conjugated Enynes by Monocarbonylation of 1,3-Diynes(Weinheim : Wiley-VCH, 2020) Liu, Jiawang; Yang, Ji; Schneider, Carolin; Franke, Robert; Jackstell, Ralf; Beller, MatthiasFor the first time, the monoalkoxycarbonylation of easily available 1,3-diynes to give synthetically useful conjugated enynes has been realized. Key to success was the design and utilization of the new ligand 2,2′-bis(tert-butyl(pyridin-2-yl)phosphanyl)-1,1′-binaphthalene (Neolephos), which permits the palladium-catalyzed selective carbonylation under mild conditions, providing a general preparation of functionalized 1,3-enynes in good-to-high yields with excellent chemoselectivities. Synthetic applications that showcase the possibilities of this novel methodology include an efficient one-pot synthesis of 4-aryl-4H-pyrans as well as the rapid construction of various heterocyclic, bicyclic, and polycyclic compounds. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemSynthesis of Molybdenum Pincer Complexes and Their Application in the Catalytic Hydrogenation of Nitriles(Weinheim : Wiley-VCH Verlag, 2020) Leischner, Thomas; Spannenberg, Anke; Junge, Kathrin; Beller, MatthiasA series of molybdenum(0), (I) and (II) complexes ligated by different PNP and NNN pincer ligands were synthesized and structurally characterized. Along with previously described Mo−PNP complexes Mo-1 and Mo-2, all prepared compounds were tested in the catalytic hydrogenation of aromatic nitriles to primary amines. Among the applied catalysts, Mo-1 is particularly well suited for the hydrogenation of electron-rich benzonitriles. Additionally, two aliphatic nitriles were transformed into the desired products in 80 and 86 %, respectively. Moreover, catalytic intermediate Mo-1a was isolated and its role in the catalytic cycle was subsequently demonstrated. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemHydrogen production from formic acid catalyzed by a phosphine free manganese complex: Investigation and mechanistic insights(Cambridge : RSC, 2020) Léval, Alexander; Agapova, Anastasiya; Steinlechner, Christoph; Alberico, Elisabetta; Junge, Henrik; Beller, MatthiasFormic acid dehydrogenation (FAD) is considered as a promising process in the context of hydrogen storage. Its low toxicity, availability and convenient handling make FA attractive as a potential hydrogen carrier. To date, most promising catalysts have been based on noble metals, such as ruthenium and iridium. Efficient non-noble metal systems like iron were designed but manganese remains relatively unexplored for this transformation. In this work, we present a panel of phosphine free manganese catalysts which showed activity and stability in formic acid dehydrogenation. The most promising results were obtained with Mn(pyridine-imidazoline)(CO)3Br yielding >14 l of the H2/CO2 mixture and proved to be stable for more than 3 days. Additionally, this study provides insights into the mechanism of formic acid dehydrogenation. Kinetic experiments, Kinetic Isotopic Effect (KIE), in situ observations, NMR labeling experiments and pH monitoring allow us to propose a catalytic cycle for this transformation.
- ItemPDA Indolylmaleimides Induce Anti-Tumor Effects in Prostate Carcinoma Cell Lines Through Mitotic Death(Lausanne : Frontiers Research Foundation, 2021) Schille, Jan Torben; Nolte, Ingo; Beck, Julia; Jilani, Daria; Roolf, Catrin; Pews-Davtyan, Anahit; Rolfs, Arndt; Henze, Larissa; Beller, Matthias; Brenig, Bertram; Junghanss, Christian; Schütz, Ekkehard; Murua Escobar, HugoCastrate resistant prostate cancer in men shares several characteristics with canine prostate cancer (PCa). Due to current insufficient therapies, evaluating novel therapeutic agents for late-stage PCa is of considerable interest for both species. PDA indolylmaleimides showed anticancer effects in several neoplastic cell lines. Herein, a comparative characterization of PDA-66 and PDA-377 mediated effects was performed in human and canine PCa cell lines, which is also the first detailed characterization of these agents on cells derived from solid tumors in general. While PDA-377 showed only weak growth inhibition on human PCa cell lines, PDA-66 inhibited proliferation and induced apoptosis in human and canine cell lines with concentrations in the low micromolar range. Morphological characterization and whole transcriptome sequencing revealed that PDA-66 induces mitotic death through its microtubule-depolymerizing ability. PDA-66 appears to be a worthwhile anti-mitotic agent for further evaluation. The similarities in cellular and molecular response observed in the cell lines of both origins form a solid basis for the use of canine PCa in vivo models to gain valuable interchangeable data to the advantage of both species.
- ItemRuthenium-Catalyzed Deuteration of Aromatic Carbonyl Compounds with a Catalytic Transient Directing Group(Weinheim : Wiley-VCH, 2021) Kopf, Sara; Ye, Fei; Neumann, Helfried; Beller, MatthiasA novel ruthenium-catalyzed C−H activation methodology for hydrogen isotope exchange of aromatic carbonyl compounds is presented. In the presence of catalytic amounts of specific amine additives, a transient directing group is formed in situ, which directs selective deuteration. A high degree of deuteration is achieved for α-carbonyl and aromatic ortho-positions. In addition, appropriate choice of conditions allows for exclusive labeling of the α-carbonyl position while a procedure for the preparation of merely ortho-deuterated compounds is also reported. This methodology proceeds with good functional group tolerance and can be also applied for deuteration of pharmaceutical drugs. Mechanistic studies reveal a kinetic isotope effect of 2.2, showing that the C−H activation is likely the rate-determining step of the catalytic cycle. Using deuterium oxide as a cheap and convenient source of deuterium, the methodology presents a cost-efficient alternative to state-of-the-art iridium-catalyzed procedures. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
- ItemCobalt Single-Atom Catalysts with High Stability for Selective Dehydrogenation of Formic Acid(Weinheim : Wiley-VCH, 2020) Li, Xiang; Surkus, Annette-Enrica; Rabeah, Jabor; Anwar, Muhammad; Dastigir, Sarim; Junge, Henrik; Brückner, Angelika; Beller, MatthiasMetal–organic framework (MOF)-derived Co-N-C catalysts with isolated single cobalt atoms have been synthesized and compared with cobalt nanoparticles for formic acid dehydrogenation. The atomically dispersed Co-N-C catalyst achieves superior activity, better acid resistance, and improved long-term stability compared with nanoparticles synthesized by a similar route. High-angle annular dark-field–scanning transmission electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and X-ray absorption fine structure characterizations reveal the formation of CoIINx centers as active sites. The optimal low-cost catalyst is a promising candidate for liquid H2 generation. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- Item3,3-Difluoroallyl ammonium salts: highly versatile, stable and selective gem-difluoroallylation reagents([London] : Nature Publishing Group UK, 2021) Ye, Fei; Ge, Yao; Spannenberg, Anke; Neumann, Helfried; Xu, Li-Wen; Beller, MatthiasThe selective synthesis of fluorinated organic molecules continues to be of major importance for the development of bioactive compounds (agrochemicals and pharmaceuticals) as well as unique materials. Among the established synthetic toolbox for incorporation of fluorine-containing units, efficient and general reagents for introducing -CF2- groups have been largely neglected. Here, we present the synthesis of 3,3-difluoropropen-1-yl ammonium salts (DFPAs) as stable, and scalable gem-difluoromethylation reagents, which allow for the direct reaction with a wide range of fascinating nucleophiles. DFPAs smoothly react with N-, O-, S-, Se-, and C-nucleophiles under mild conditions without necessity of metal catalysts with exclusive regioselectivity. In this way, the presented reagents also permit the straightforward preparation of many analogues of existing pharmaceuticals.
- ItemGeneral and selective synthesis of primary amines using Ni-based homogeneous catalysts(Cambridge : RSC, 2020) Murugesan, Kathiravan; Wei, Zhihong; Chandrashekhar, Vishwas G.; Jiao, Haijun; Beller, Matthias; Jagadeesh, Rajenahally V.The development of base metal catalysts for industrially relevant amination and hydrogenation reactions by applying abundant and atom economical reagents continues to be important for the cost-effective and sustainable synthesis of amines which represent highly essential chemicals. In particular, the synthesis of primary amines is of central importance because these compounds serve as key precursors and central intermediates to produce value-added fine and bulk chemicals as well as pharmaceuticals, agrochemicals and materials. Here we report a Ni-triphos complex as the first Ni-based homogeneous catalyst for both reductive amination of carbonyl compounds with ammonia and hydrogenation of nitroarenes to prepare all kinds of primary amines. Remarkably, this Ni-complex enabled the synthesis of functionalized and structurally diverse benzylic, heterocyclic and aliphatic linear and branched primary amines as well as aromatic primary amines starting from inexpensive and easily accessible carbonyl compounds (aldehydes and ketones) and nitroarenes using ammonia and molecular hydrogen. This Ni-catalyzed reductive amination methodology has been applied for the amination of more complex pharmaceuticals and steroid derivatives. Detailed DFT computations have been performed for the Ni-triphos based reductive amination reaction, and they revealed that the overall reaction has an inner-sphere mechanism with H2metathesis as the rate-determining step. © The Royal Society of Chemistry 2020.
- ItemA General and Highly Selective Palladium-Catalyzed Hydroamidation of 1,3-Diynes(Weinheim : Wiley-VCH, 2021) Liu, Jiawang; Schneider, Carolin; Yang, Ji; Wei, Zhihong; Jiao, Haijun; Franke, Robert; Jackstell, Ralf; Beller, MatthiasA chemo-, regio-, and stereoselective mono-hydroamidation of (un)symmetrical 1,3-diynes is described. Key for the success of this novel transformation is the utilization of an advanced palladium catalyst system with the specific ligand Neolephos. The synthetic value of this general approach to synthetically useful α-alkynyl-α, β-unsaturated amides is showcased by diversification of several structurally complex molecules and marketed drugs. Control experiments and density-functional theory (M06L-SMD) computations also suggest the crucial role of the substrate in controlling the regioselectivity of unsymmetrical 1,3-diynes. © 2020 The Authors. Published by Wiley-VCH GmbH