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Type: Text × Publisher: Weinheim : Wiley-VCH × Subject: cobalt × Subject: hydrogenation ×

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Now showing 1 - 3 of 3
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    A Highly Active Cobalt Catalyst for the General and Selective Hydrogenation of Aromatic Heterocycles
    (Weinheim : Wiley-VCH, 2023) Bauer, Christof; Müller, Felix; Keskin, Sercan; Zobel, Mirijam; Kempe, Rhett
    Nanostructured earth abundant metal catalysts that mediate important chemical reactions with high efficiency and selectivity are of great interest. This study introduces a synthesis protocol for nanostructured earth abundant metal catalysts. Three components, an inexpensive metal precursor, an easy to synthesize N/C precursor, and a porous support material undergo pyrolysis to give the catalyst material in a simple, single synthesis step. By applying this catalyst synthesis, a highly active cobalt catalyst for the general and selective hydrogenation of aromatic heterocycles could be generated. The reaction is important with regard to organic synthesis and hydrogen storage. The mild reaction conditions observed for quinolines permit the selective hydrogenation of numerous classes of N-, O- and S-heterocyclic compounds such as: quinoxalines, pyridines, pyrroles, indoles, isoquinoline, aciridine amine, phenanthroline, benzofuranes, and benzothiophenes.
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    Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst
    (Weinheim : Wiley-VCH, 2020) Ryabchuk, Pavel; Leischner, Thomas; Kreyenschulte, Carsten; Spannenberg, Anke; Junge, Kathrin; Beller, Matthias
    A bifunctional 3d-metal catalyst for the cascade synthesis of diverse pyrroles from nitroarenes is presented. The optimal catalytic system Co/NGr-C@SiO2-L is obtained by pyrolysis of a cobalt-impregnated composite followed by subsequent selective leaching. In the presence of this material, (transfer) hydrogenation of easily available nitroarenes and subsequent Paal–Knorr/Clauson-Kass condensation provides >40 pyrroles in good to high yields using dihydrogen, formic acid, or a CO/H2O mixture (WGSR conditions) as reductant. In addition to the favorable step economy, this straightforward domino process does not require any solvents or external co-catalysts. The general synthetic utility of this methodology was demonstrated on a variety of functionalized substrates including the preparation of biologically active and pharmaceutically relevant compounds, for example, (+)-Isamoltane. © 2020 The Authors. Published by Wiley-VCH GmbH
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    A General Regioselective Synthesis of Alcohols by Cobalt-Catalyzed Hydrogenation of Epoxides
    (Weinheim : Wiley-VCH, 2020) Liu, Weiping; Leischner, Thomas; Li, Wu; Junge, Kathrin; Beller, Matthias
    A straightforward methodology for the synthesis of anti-Markovnikov-type alcohols is presented. By using a specific cobalt triphos complex in the presence of Zn(OTf)2 as an additive, the hydrogenation of epoxides proceeds with high yields and selectivities. The described protocol shows a broad substrate scope, including multi-substituted internal and terminal epoxides, as well as a good functional-group tolerance. Various natural-product derivatives, including steroids, terpenoids, and sesquiterpenoids, gave access to the corresponding alcohols in moderate-to-excellent yields. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.