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- ItemHomogeneous cobalt-catalyzed reductive amination for synthesis of functionalized primary amines([London] : Nature Publishing Group UK, 2019) Murugesan, Kathiravan; Wei, Zhihong; Chandrashekhar, Vishwas G.; Neumann, Helfried; Spannenberg, Anke; Jiao, Haijun; Beller, Matthias; Jagadeesh, Rajenahally V.The development of earth abundant 3d metal-based catalysts continues to be an important goal of chemical research. In particular, the design of base metal complexes for reductive amination to produce primary amines remains as challenging. Here, we report the combination of cobalt and linear-triphos (bis(2-diphenylphosphinoethyl)phenylphosphine) as the molecularly-defined non-noble metal catalyst for the synthesis of linear and branched benzylic, heterocyclic and aliphatic primary amines from carbonyl compounds, gaseous ammonia and hydrogen in good to excellent yields. Noteworthy, this cobalt catalyst exhibits high selectivity and as a result the -NH2 moiety is introduced in functionalized and structurally diverse molecules. An inner-sphere mechanism on the basis of the mono-cationic [triphos-CoH]+ complex as active catalyst is proposed and supported with density functional theory computation on the doublet state potential free energy surface and H2 metathesis is found as the rate-determining step.
- ItemSimple ruthenium-catalyzed reductive amination enables the synthesis of a broad range of primary amines([London] : Nature Publishing Group UK, 2018) Senthamarai, Thirusangumurugan; Murugesan, Kathiravan; Schneidewind, Jacob; Kalevaru, Narayana V.; Baumann, Wolfgang; Neumann, Helfried; Kamer, Paul C. J.; Beller, Matthias; Jagadeesh, Rajenahally V.The production of primary benzylic and aliphatic amines, which represent essential feedstocks and key intermediates for valuable chemicals, life science molecules and materials, is of central importance. Here, we report the synthesis of this class of amines starting from carbonyl compounds and ammonia by Ru-catalyzed reductive amination using H2. Key to success for this synthesis is the use of a simple RuCl2(PPh3)3 catalyst that empowers the synthesis of >90 various linear and branched benzylic, heterocyclic, and aliphatic amines under industrially viable and scalable conditions. Applying this catalyst, −NH2 moiety has been introduced in functionalized and structurally diverse compounds, steroid derivatives and pharmaceuticals. Noteworthy, the synthetic utility of this Ru-catalyzed amination protocol has been demonstrated by upscaling the reactions up to 10 gram-scale syntheses. Furthermore, in situ NMR studies were performed for the identification of active catalytic species. Based on these studies a mechanism for Ru-catalyzed reductive amination is proposed.
- ItemHomogeneous and heterogeneous catalytic reduction of amides and related compounds using molecular hydrogen([London] : Nature Publishing Group UK, 2020) Cabrero-Antonino, Jose R.; Adam, Rosa; Papa, Veronica; Beller, MatthiasCatalytic hydrogenation of amides is of great interest for chemists working in organic synthesis, as the resulting amines are widely featured in natural products, drugs, agrochemicals, dyes, etc. Compared to traditional reduction of amides using (over)stoichiometric reductants, the direct hydrogenation of amides using molecular hydrogen represents a greener approach. Furthermore, amide hydrogenation is a highly versatile transformation, since not only higher amines (obtained by C–O cleavage), but also lower amines and alcohols, or amino alcohols (obtained by C–N cleavage) can be selectively accessed by fine tuning of reaction conditions. This review describes the most recent advances in the area of amide hydrogenation using H2 exclusively and molecularly defined homogeneous as well as nano-structured heterogeneous catalysts, with a special focus on catalyst development and synthetic applications.
- ItemThe role of allyl ammonium salts in palladium-catalyzed cascade reactions towards the synthesis of spiro-fused heterocycles([London] : Nature Publishing Group UK, 2020) Ye, Fei; Ge, Yao; Spannenberg, Anke; Neumann, Helfried; Beller, MatthiasThere is a continuous need for designing new and improved synthetic methods aiming at minimizing reaction steps while increasing molecular complexity. In this respect, catalytic, one-pot cascade methodologies constitute an ideal tool for the construction of complex molecules with high chemo-, regio-, and stereoselectivity. Herein, we describe two general and efficient cascade procedures for the synthesis of spiro-fused heterocylces. This transformation combines selective nucleophilic substitution (SN2′), palladium-catalyzed Heck and C–H activation reactions in a cascade manner. The use of allylic ammonium salts and specific Pd catalysts are key to the success of the transformations. The synthetic utility of these methodologies is showcased by the preparation of 48 spiro-fused dihydrobenzofuranes and indolines including a variety of fluorinated derivatives.
- ItemIntermetallic nickel silicide nanocatalyst—A non-noble metal–based general hydrogenation catalyst(Washington, DC [u.a.] : Assoc., 2018) Ryabchuk, Pavel; Agostini, Giovanni; Pohl, Marga-Martina; Lund, Henrik; Agapova, Anastasiya; Junge, Henrik; Junge, Kathrin; Beller, MatthiasHydrogenation reactions are essential processes in the chemical industry, giving access to a variety of valuable compounds including fine chemicals, agrochemicals, and pharmachemicals. On an industrial scale, hydrogenations are typically performed with precious metal catalysts or with base metal catalysts, such as Raney nickel, which requires special handling due to its pyrophoric nature. We report a stable and highly active intermetallic nickel silicide catalyst that can be used for hydrogenations of a wide range of unsaturated compounds. The catalyst is prepared via a straightforward procedure using SiO2 as the silicon atom source. The process involves thermal reduction of Si–O bonds in the presence of Ni nanoparticles at temperatures below 1000°C. The presence of silicon as a secondary component in the nickel metal lattice plays the key role in its properties and is of crucial importance for improved catalytic activity. This novel catalyst allows for efficient reduction of nitroarenes, carbonyls, nitriles, N-containing heterocycles, and unsaturated carbon–carbon bonds. Moreover, the reported catalyst can be used for oxidation reactions in the presence of molecular oxygen and is capable of promoting acceptorless dehydrogenation of unsaturated N-containing heterocycles, opening avenues for H2 storage in organic compounds. The generality of the nickel silicide catalyst is demonstrated in the hydrogenation of over a hundred of structurally diverse unsaturated compounds. The wide application scope and high catalytic activity of this novel catalyst make it a nice alternative to known general hydrogenation catalysts, such as Raney nickel and noble metal–based catalysts.
- ItemHydrogenation of terminal and internal olefins using a biowaste-derived heterogeneous cobalt catalyst(Washington, DC [u.a.] : Assoc., 2018) Scharnagl, Florian Korbinian; Hertrich, Maximilian Franz; Ferretti, Francesco; Kreyenschulte, Carsten; Lund, Henrik; Jackstell, Ralf; Beller, MatthiasHydrogenation of olefins is achieved using biowaste-derived cobalt chitosan catalysts. Characterization of the optimal Co@Chitosan-700 by STEM (scanning transmission electron microscopy), EELS (electron energy loss spectroscopy), PXRD (powder x-ray diffraction), and elemental analysis revealed the formation of a distinctive magnetic composite material with high metallic Co content. The general performance of this catalyst is demonstrated in the hydrogenation of 50 olefins including terminal, internal, and functionalized derivatives, as well as renew-ables. Using this nonnoble metal composite, hydrogenation of terminal C==C double bonds occurs under very mild and benign conditions (water or methanol, 40° to 60°C). The utility of Co@Chitosan-700 is showcased for efficient hydrogenation of the industrially relevant examples diisobutene, fatty acids, and their triglycerides. Because of the magnetic behavior of this material and water as solvent, product separation and recycling of the catalyst are straightforward.