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Author: Blach, Patricia ×

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    Synthesis of 3,4-Dihydro-2H-Pyrroles from Ketones, Aldehydes, and Nitro Alkanes via Hydrogenative Cyclization
    (Weinheim : Wiley-VCH, 2022) Klausfelder, Barbara; Blach, Patricia; de Jonge, Niels; Kempe, Rhett
    Syntheses of N-heterocyclic compounds that permit a flexible introduction of various substitution patterns by using inexpensive and diversely available starting materials are highly desirable. Easy to handle and reusable catalysts based on earth-abundant metals are especially attractive for these syntheses. We report here on the synthesis of 3,4-dihydro-2H-pyrroles via the hydrogenation and cyclization of nitro ketones. The latter are easily accessible from three components: a ketone, an aldehyde and a nitroalkane. Our reaction has a broad scope and 23 of the 33 products synthesized are compounds which have not yet been reported. The key to the general hydrogenation/cyclization reaction is a highly active, selective and reusable nickel catalyst, which was identified from a library of 24 earth-abundant metal catalysts.
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    Key Parameters for the Synthesis of Active and Selective Nanostructured 3d Metal Catalysts Starting from Coordination Compounds – Case Study: Nickel Mediated Reductive Amination
    (Weinheim : WILEY-VCH Verlag, 2021) Klarner, Mara; Blach, Patricia; Wittkämper, Haiko; de Jonge, Niels; Papp, Christian; Kempe, Rhett
    The design of nanostructured catalysts based on earth-abundant metals that mediate important reactions efficiently, selectively and with a broad scope is highly desirable. Unfortunately, the synthesis of such catalysts is poorly understood. We report here on highly active Ni catalysts for the reductive amination of ketones by ammonia employing hydrogen as a reducing agent. The key functions of the Ni-salen precursor complex during catalyst synthesis have been identified: (1) Ni-salen complexes sublime during catalyst synthesis, which allows molecular dispersion of the metal precursor on the support material. (2) The salen ligand forms a nitrogen-doped carbon shell by decomposition, which embeds and stabilizes the Ni nanoparticles on the γ-Al2O3 support. (3) Parameters, such as flow rate of the pyrolysis gas, determine the carbon supply for the embedding process of Ni nanoparticles.
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    Graphene Enclosure of Chemically Fixed Mammalian Cells for Liquid-Phase Electron Microscopy
    (Cambridge, MA : JoVE, 2020) Blach, Patricia; Keskin, Sercan; de Jonge, Niels
    A protocol is described for investigating the human epidermal growth factor receptor 2 (HER2) in the intact plasma membrane of breast cancer cells using scanning transmission electron microscopy (STEM). Cells of the mammalian breast cancer cell line SKBR3 were grown on silicon microchips with silicon nitride (SiN) windows. Cells were chemically fixed, and HER2 proteins were labeled with quantum dot nanoparticles (QDs), using a two-step biotin-streptavidin binding protocol. The cells were coated with multilayer graphene to maintain a hydrated state, and to protect them from electron beam damage during STEM. To examine the stability of the samples under electron beam irradiation, a dose series experiment was performed. Graphene-coated and non-coated samples were compared. Beam induced damage, in the form of bright artifacts, appeared for some non-coated samples at increased electron dose D, while no artifacts appeared on coated samples.