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- ItemA Stable Manganese Pincer Catalyst for the Selective Dehydrogenation of Methanol(Weinheim : Wiley-VCH, 2016-12-2) Andérez-Fernández, María; Vogt, Lydia K.; Fischer, Steffen; Zhou, Wei; Jiao, Haijun; Garbe, Marcel; Elangovan, Saravanakumar; Junge, Kathrin; Junge, Henrik; Ludwig, Ralf; Beller, MatthiasFor the first time, structurally defined manganese pincer complexes catalyze the dehydrogenation of aqueous methanol to hydrogen and carbon dioxide, which is a transformation of interest with regard to the implementation of a hydrogen and methanol economy. Excellent long-term stability was demonstrated for the Mn-PNPiPr catalyst, as a turnover of more than 20 000 was reached. In addition to methanol, other important hydrogen carriers were also successfully dehydrogenated.
- ItemSynthesis of Single Atom Based Heterogeneous Platinum Catalysts: High Selectivity and Activity for Hydrosilylation Reactions(Washington, DC : ACS Publ., 2017) Cui, Xinjiang; Junge, Kathrin; Dai, Xingchao; Kreyenschulte, Carsten; Pohl, Marga-Martina; Wohlrab, Sebastian; Shi, Feng; Brückner, Angelika; Beller, MatthiasCatalytic hydrosilylation represents a straightforward and atom-efficient methodology for the creation of C-Si bonds. In general, the application of homogeneous platinum complexes prevails in industry and academia. Herein, we describe the first heterogeneous single atom catalysts (SACs), which are conveniently prepared by decorating alumina nanorods with platinum atoms. The resulting stable material efficiently catalyzes hydrosilylation of industrially relevant olefins with high TON (≈105). A variety of substrates is selectively hydrosilylated including compounds with sensitive reducible and other functional groups (N, B, F, Cl). The single atom based catalyst shows significantly higher activity compared to related Pt nanoparticles.
- ItemToward Green Acylation of (Hetero)arenes: Palladium-Catalyzed Carbonylation of Olefins to Ketones(Washington, DC : ACS Publ., 2017) Liu, Jie; Wei, Zhihong; Jiao, Haijun; Jackstell, Ralf; Beller, MatthiasGreen Friedel-Crafts acylation reactions belong to the most desired transformations in organic chemistry. The resulting ketones constitute important intermediates, building blocks, and functional molecules in organic synthesis as well as for the chemical industry. Over the past 60 years, advances in this topic have focused on how to make this reaction more economically and environmentally friendly by using green acylating conditions, such as stoichiometric acylations and catalytic homogeneous and heterogeneous acylations. However, currently well-established methodologies for their synthesis either produce significant amounts of waste or proceed under harsh conditions, limiting applications. Here, we present a new protocol for the straightforward and selective introduction of acyl groups into (hetero)arenes without directing groups by using available olefins with inexpensive CO. In the presence of commercial palladium catalysts, inter- and intramolecular carbonylative C-H functionalizations take place with good regio- and chemoselectivity. Compared to classical Friedel-Crafts chemistry, this novel methodology proceeds under mild reaction conditions. The general applicability of this methodology is demonstrated by the direct carbonylation of industrial feedstocks (ethylene and diisobutene) as well as of natural products (eugenol and safrole). Furthermore, synthetic applications to drug molecules are showcased.
- 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.
- ItemCorrection: A robust iron catalyst for the selective hydrogenation of substituted (iso)quinolones(Cambridge : RSC, 2018) Sahoo, Basudev; Kreyenschulte, Carsten; Agostini, Giovanni; Lund, Henrik; Bachmann, Stephan; Scalone, Michelangelo; Junge, Kathrin; Beller, MatthiasThe authors regret that the term “(iso)quinolones” was used throughout the article, including the title, when the correct term should be “(iso)quinolines”. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.
- ItemUnprecedented selective homogeneous cobalt-catalysed reductive alkoxylation of cyclic imides under mild conditions(Cambridge : RSC, 2017) Cabrero-Antonino, Jose R.; Adam, Rosa; Papa, Veronica; Holsten, Mattes; Junge, Kathrin; Beller, MatthiasThe first general and efficient non-noble metal-catalysed reductive C2-alkoxylation of cyclic imides (phthalimides and succinimides) is presented. Crucial for the success is the use of [Co(BF4)2·6H2O/triphos (L1)] combination and no external additives are required. Using the optimal cobalt-system, the hydrogenation of the aromatic ring of the parent phthalimide is avoided and only one of the carbonyl groups is selectively functionalized. The resulting products, N- and aryl-ring substituted 3-alkoxy-2,3-dihydro-1H-isoindolin-1-one and N-substituted 3-alkoxy-pyrrolidin-2-one derivatives, are prepared under mild conditions in good to excellent isolated yields. Intramolecular reductive couplings can also be performed affording tricyclic compounds in a one-step process. The present protocol opens the way to the development of new base-metal processes for the straightforward synthesis of functionalized N-heterocyclic compounds of pharmaceutical and biological interest.
- ItemEfficient and selective hydrogenation of amides to alcohols and amines using a well-defined manganese-PNN pincer complex(Cambridge : RSC, 2017) Papa, Veronica; Cabrero-Antonino, Jose R.; Alberico, Elisabetta; Spanneberg, Anke; Junge, Kathrin; Junge, Henrik; Beller, MatthiasNovel well-defined NNP and PNP manganese pincer complexes have been synthetized and fully characterized. The catalyst Mn-2 containing an imidazolyaminolphosphino ligand shows high activity and selectivity in the hydrogenation of a wide range of secondary and tertiary amides to the corresponding alcohols and amines, under relatively mild conditions. For the first time, more challenging substrates like primary aromatic amides including an actual herbicide can also be hydrogenated using this earth-abundant metal-based pincer catalyst.
- 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.
- ItemCobalt-catalysed reductive C-H alkylation of indoles using carboxylic acids and molecular hydrogen(Cambridge : RSC, 2017) Cabrero-Antonino, Jose R.; Adam, Rosa; Junge, Kathrin; Beller, MatthiasThe direct CH-alkylation of indoles using carboxylic acids is presented for the first time. The catalytic system based on the combination of Co(acac)3 and 1,1,1-tris(diphenylphosphinomethyl)-ethane (Triphos, L1), in the presence of Al(OTf)3 as co-catalyst, is able to perform the reductive alkylation of 2-methyl-1H-indole with a wide range of carboxylic acids. The utility of the protocol was further demonstrated through the C3 alkylation of several substituted indole derivatives using acetic, phenylacetic or diphenylacetic acids. In addition, a careful selection of the reaction conditions allowed to perform the selective C3 alkenylation of some indole derivatives. Moreover, the alkenylation of C2 position of 3-methyl-1H-indole was also possible. Control experiments indicate that the aldehyde, in situ formed from the carboxylic acid hydrogenation, plays a central role in the overall process. This new protocol enables the direct functionalization of indoles with readily available and stable carboxylic acids using a non-precious metal based catalyst and hydrogen as reductant.