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- ItemCobalt pincer complexes for catalytic reduction of nitriles to primary amines(London : RSC Publ., 2019) Schneekönig, Jacob; Tannert, Bianca; Hornke, Helen; Beller, Matthias; Junge, KathrinVarious cobalt pincer type complexes 1-6 were applied for the catalytic hydrogenation of nitriles to amines. Among these, catalyst 4 is the most efficient, allowing the reduction of aromatic as well as aliphatic nitriles in moderate to excellent yields. © 2019 The Royal Society of Chemistry.
- ItemAddressing the Reproducibility of Photocatalytic Carbon Dioxide Reduction(Weinheim : Wiley-VCH Verlag, 2019) Marx, Maximilian; Mele, Andrea; Spannenberg, Anke; Steinlechner, Christoph; Junge, Henrik; Schollhammer, Philippe; Beller, MatthiasReproducibility of photocatalytic reactions, especially when conducted on small scale for improved turnover numbers with in situ formed catalysts can prove challenging. Herein, we showcase the problematic reproducibility on the example of attractive photocatalytic CO2 reduction utilizing [FeFe] hydrogenase mimics. These Fe complexes, well-known for their application in proton reduction reactions, were combined with a heteroleptic Cu photosensitizer and produced CO/H2/HCO2H mixtures of variable constitution. However, the reactions indicated a poor reproducibility, even when conducted with well-defined complexes. Based on our experience, we make suggestions for scientists working in the field of photocatalysis on how to address and report the reproducibility of novel photocatalytic reaction protocols. In addition, we would like to highlight the importance of studying reproducibility of novel reaction protocols, especially in the fields of photocatalytic water splitting and CO2 reduction, where TONs are widely used as the comparable measure for catalytic activity. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemCobalt-Catalyzed Aqueous Dehydrogenation of Formic Acid(Weinheim : Wiley-VCH, 2019) Zhou, Wei; Wei, Zhihong; Spannenberg, Anke; Jiao, Haijun; Junge, Kathrin; Junge, Henrik; Beller, MatthiasAmong the known liquid organic hydrogen carriers, formic acid attracts increasing interest in the context of safe and reversible storage of hydrogen. Here, the first molecularly defined cobalt pincer complex is disclosed for the dehydrogenation of formic acid in aqueous medium under mild conditions. Crucial for catalytic activity is the use of the specific complex 3. Compared to related ruthenium and manganese complexes 7 and 8, this optimal cobalt complex showed improved performance. DFT computations support an innocent non-classical bifunctional outer-sphere mechanism on the triplet state potential energy surface. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemHighly selective hydrogenation of amides catalysed by a molybdenum pincer complex : Scope and mechanism(Cambridge : RSC, 2019) Leischner, Thomas; Suarez, Lluis Artús; Spannenberg, Anke; Nova, Ainara; Junge, Kathrin; Nova, Ainara; Beller, MatthiasA series of molybdenum pincer complexes has been shown for the first time to be active in the catalytic hydrogenation of amides. Among the tested catalysts, Mo-1a proved to be particularly well suited for the selective C-N hydrogenolysis of N-methylated formanilides. Notably, high chemoselectivity was observed in the presence of certain reducible groups including even other amides. The general catalytic performance as well as selectivity issues could be rationalized taking an anionic Mo(0) as the active species. The interplay between the amide CO reduction and the catalyst poisoning by primary amides accounts for the selective hydrogenation of N-methylated formanilides. The catalyst resting state was found to be a Mo-alkoxo complex formed by reaction with the alcohol product. This species plays two opposed roles-it facilitates the protolytic cleavage of the C-N bond but it encumbers the activation of hydrogen. This journal is © The Royal Society of Chemistry.
- ItemIsoquinolinamine FX-9 Exhibits Anti-Mitotic Activity in Human and Canine Prostate Carcinoma Cell Lines(Basel : Molecular Diversity Preservation International, 2019) Schille, Jan Torben; Nolte, Ingo; Packeiser, Eva-Maria; Wiesner, Laura; Hein, Jens Ingo; Weiner, Franziska; Wu, Xiao-Feng; Beller, Matthias; Junghanss, Christian; Escobar, Hugo MuruaCurrent therapies are insufficient for metastatic prostate cancer (PCa) in men and dogs. As human castrate-resistant PCa shares several characteristics with the canine disease, comparative evaluation of novel therapeutic agents is of considerable value for both species. Novel isoquinolinamine FX-9 exhibits antiproliferative activity in acute lymphoblastic leukemia cell lines but has not been tested yet on any solid neoplasia type. In this study, FX-9's mediated effects were characterized on two human (PC-3, LNCaP) and two canine (CT1258, 0846) PCa cell lines, as well as benign solid tissue cells. FX-9 significantly inhibited cell viability and induced apoptosis with concentrations in the low micromolar range. Mediated effects were highly comparable between the PCa cell lines of both species, but less pronounced on non-malignant chondrocytes and fibroblasts. Interestingly, FX-9 exposure also leads to the formation and survival of enlarged multinucleated cells through mitotic slippage. Based on the results, FX-9 acts as an anti-mitotic agent with reduced cytotoxic activity in benign cells. The characterization of FX-9-induced effects on PCa cells provides a basis for in vivo studies with the potential of valuable transferable findings to the benefit of men and dogs. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
- ItemMonodisperse nickel-nanoparticles for stereo- and chemoselective hydrogenation of alkynes to alkenes(Amsterdam [u.a.] : Elsevier, 2019) Murugesan, Kathiravan; Alshammari, Ahmad S.; Sohail, Manzar; Beller, Matthias; Jagadeesh, Rajenahally V.Here, we report the use of monosaccharides for the preparation of novel nickel nanoparticles (NP), which constitute selective hydrogenation catalysts. For example, immobilization of fructose and Ni(OAc)2 on silica and subsequent pyrolysis under inert atmosphere produced graphitic shells encapsulated Ni-NP with uniform size and distribution. Interestingly, fructose acts as structure controlling compound to generate specific graphitic layers and the formation of monodisperse NP. The resulting stable and reusable catalysts allow for stereo- and chemoselective semihydrogenation of functionalized and structurally diverse alkynes in high yields and selectivity. © 2019 The Author(s)
- ItemTetraÂcarbonÂyl[4,4-dimethyl-2-(pyridin-2-yl)-2-oxazoline-κ2N,N′]molybdenum(0)(Chester : IUCr, 2019) Steinlechner, Christoph; Spannenberg, Anke; Junge, Henrik; Beller, MatthiasIn the title compound, [Mo(C10H12N2O)(CO)4], the molybdenum(0) center is surrounded by a bidentate diÂimine [4,4-dimethyl-2-(pyridin-2-yl)-2-oxazoline] and four carbonyl ligands in a distorted octaÂhedral coordination geometry. The diÂimine ligand coordinates via the two nitroÂgen atoms.
- ItemPractical Catalytic Cleavage of C(sp3)−C(sp3) Bonds in Amines(Weinheim : Wiley-VCH, 2019) Li, Wu; Liu, Weiping; Leonard, David K.; Rabeah, Jabor; Junge, Kathrin; Brgckner, Angelika; Beller, MatthiasThe selective cleavage of thermodynamically stable C(sp3)−C(sp3) single bonds is rare compared to their ubiquitous formation. Herein, we describe a general methodology for such transformations using homogeneous copper-based catalysts in the presence of air. The utility of this novel methodology is demonstrated for Cα−Cβ bond scission in >70 amines with excellent functional group tolerance. This transformation establishes tertiary amines as a general synthon for amides and provides valuable possibilities for their scalable functionalization in, for example, natural products and bioactive molecules. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemNickel-Catalyzed Stereodivergent Synthesis of E- and Z-Alkenes by Hydrogenation of Alkynes(Weinheim : Wiley-VCH, 2019) Murugesan, Kathiravan; Bheeter, Charles Beromeo; Linnebank, Pim R.; Spannenberg, Anke; Reek, Joost N.H.; Jagadeesh, Rajenahally V.; Beller, MatthiasA convenient protocol for stereodivergent hydrogenation of alkynes to E- and Z-alkenes by using nickel catalysts was developed. Simple Ni(NO3)2⋅6 H2O as a catalyst precursor formed active nanoparticles, which were effective for the semihydrogenation of several alkynes with high selectivity for the Z-alkene (Z/E>99:1). Upon addition of specific multidentate ligands (triphos, tetraphos), the resulting molecular catalysts were highly selective for the E-alkene products (E/Z>99:1). Mechanistic studies revealed that the Z-alkene-selective catalyst was heterogeneous whereas the E-alkene-selective catalyst was homogeneous. In the latter case, the alkyne was first hydrogenated to a Z-alkene, which was subsequently isomerized to the E-alkene. This proposal was supported by density functional theory calculations. This synthetic methodology was shown to be generally applicable in >40 examples and scalable to multigram-scale experiments. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.