Dr. Jochen Niemeyer
Institute of Organic Chemistry
University of Duisburg-Essen
- Development of Fluorescent Chemosensors for Amino-sugars
Yadav, R. and Kwamen, C. and Niemeyer, J.
Israel Journal of Chemistry (2021)In this account, we describe the application of a series of multidentate BINOL-based phosphoric acids for the fluorescence-based chemosensing of amino sugars. To this end, we developed a novel synthetic protocol for three isomerically pure phosphoric acid monoesters of the type ArOP(O)(OH)2. These were investigated with respect to their binding towards amino sugars (glucosamine, galactosamine and mannosamine) in comparison to the previously reported diesters of the type (ArO)2P(O)(OH). We could find that the diesters show no significant binding, while the monoesters can be used as hosts for amino sugars. Indeed, one host selectively binds to galactosamine, while a second host binds both glucosamine and mannosamine. This allows the fluorescence-based detection and discrimination of the amino sugars by a novel class of phosphate-based supramolecular hosts. © 2021 The Authors. Israel Journal of Chemistry published by Wiley-VCH GmbH
view abstract 10.1002/ijch.202000104
- Functional Rotaxanes in Catalysis
Kwamen, C. and Niemeyer, J.
Chemistry - A European Journal 27 (2021)Mechanically interlocked molecules (MIMs) have gained attention in the field of catalysis due to their unique molecular properties. Central to MIMs, rotaxanes are highly promising and attractive supramolecular catalysts due to their unique three-dimensional structures and the flexibility of their subcomponents. This Minireview discusses the use of rotaxanes in organocatalysis and transition-metal catalysis. © 2020 The Authors. Published by Wiley-VCH GmbH
view abstract 10.1002/chem.202002876
- Photonic NO2 Gas Sensing with Binaphthyl-Based Dopants
Spengler, M. and Pschyklenk, L. and Niemeyer, J. and Kaul, P. and Giese, M.
Advanced Optical Materials (2021)A series of reactive binaphthyl-diimine-based dopants is prepared and investigated with respect to their potential for the chiral induction of structural coloration in nematic liquid crystal mixture E7 and the selective photonic sensing of nitrogen dioxide (NO2). Studies of the helical twisting power (HTP) in 4-cyano-4′-pentylbiphenyl (5CB) reveal HTP values as high as 375 µm-1 and the tremendous impact of structural compatibility and changes of the dihedral binaphthyl angle on the efficiency of the chiral transfer. Detailed investigation of the sensing capabilities of the systems reveals an extraordinarily high selectivity for NO2 and a response to concentrations as low as 100 ppm. The systems show a direct response to the analyte gas leading to a concentration-dependent shift of the reflectance wavelength of up to several hundred nanometers. Incorporation of copper ions remarkably improves the sensor's properties in terms of sensitivity and selectivity, enabling the tailored tweaking of the system's properties. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
view abstract 10.1002/adom.202001828
- Supramolecular polymers with reversed viscosity/temperature profile for application in motor oils
Ostwaldt, J.-E. and Hirschhäuser, C. and Maier, S.K. and Schmuck, C. and Niemeyer, J.
Beilstein Journal of Organic Chemistry 17 (2021)We report novel supramolecular polymers, which possess a reversed viscosity/temperature profile. To this end, we developed a series of ditopic monomers featuring two self-complementary binding sites, either the guanidiniocarbonyl pyrrole carboxylic acid (GCP) or the aminopyridine carbonyl pyrrole carboxylic acid (ACP). At low temperatures, small cyclic structures are formed. However, at elevated temperatures, a ring–chain transformation leads to the formation of a supramolecular polymer. We demonstrate that this effect is dependent on the concentration of the solution and on the polarity of the solvent. This effect can counteract the loss of viscosity of the solvent at elevated temperatures, thus opening an application of our systems as viscosity index improvers (VIIs) in working fluids. This was tested for different motor oils and led to the identification of one compound as a promising VII. © 2021 Ostwaldt et al.
view abstract 10.3762/BJOC.17.11
- A combined experimental and modelling approach for the Weimberg pathway optimisation
Shen, L. and Kohlhaas, M. and Enoki, J. and Meier, R. and Schönenberger, B. and Wohlgemuth, R. and Kourist, R. and Niemeyer, F. and van Niekerk, D. and Bräsen, C. and Niemeyer, J. and Snoep, J. and Siebers, B.
Nature Communications 11 (2020)The oxidative Weimberg pathway for the five-step pentose degradation to α-ketoglutarate is a key route for sustainable bioconversion of lignocellulosic biomass to added-value products and biofuels. The oxidative pathway from Caulobacter crescentus has been employed in in-vivo metabolic engineering with intact cells and in in-vitro enzyme cascades. The performance of such engineering approaches is often hampered by systems complexity, caused by non-linear kinetics and allosteric regulatory mechanisms. Here we report an iterative approach to construct and validate a quantitative model for the Weimberg pathway. Two sensitive points in pathway performance have been identified as follows: (1) product inhibition of the dehydrogenases (particularly in the absence of an efficient NAD+ recycling mechanism) and (2) balancing the activities of the dehydratases. The resulting model is utilized to design enzyme cascades for optimized conversion and to analyse pathway performance in C. cresensus cell-free extracts. © 2020, The Author(s).
view abstract 10.1038/s41467-020-14830-y
- A Metallosupramolecular Coordination Polymer for the ‘Turn-on’ Fluorescence Detection of Hydrogen Sulfide
Hatai, J. and Hirschhäuser, C. and Schmuck, C. and Niemeyer, J.
ChemistryOpen 9 (2020)A coumarin based probe for the efficient detection of hydrogen sulfide in aqueous medium is reported. The investigated coumarine-based derivative forms spherical nanoparticles in aqueous media. In presence of Pd2+, a metallosupramolecular coordination polymer is formed, which is accompanied by quenching of the coumarin emission at 390 nm. Its Pd2+ complex could be used as a probe for chemoselective detection of monohydrogensulfide (HS−). Presence of HS− leads to a'turn-on' fluorescence signal, resulting from decomplexation of Pd2+ from the metallosupramolecular probe. The probe was successfully applied for qualitative and quantitative detection of HS− in different sources of water directly collected from sea, river, tap and laboratory drain water, as well as in growth media for aquatic species. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
view abstract 10.1002/open.202000163
- Control of secondary structure and morphology of peptide–guanidiniocarbonylpyrrole conjugates by variation of the chain length
Liu, X. and Wang, K. and Externbrink, M. and Niemeyer, J. and Giese, M. and Hu, X.-Y.
Chinese Chemical Letters 31 (2020)Peptide amphiphiles with well-organized secondary structure are an important family of molecules that are known to assemble into a variety of nanostructures. In this work, we present three guanidiniocarbonylpyrrole (GCP) containing peptide amphiphiles, which show versatile morphology and secondary structure changes as a result of different chain lengths and in different concentration regimes. The random coil conformation, α-helix, and β-sheet are obtained for peptide 1, peptide 2, and peptide 3, respectively under neutral aqueous conditions. Furthermore, all peptide amphiphiles can aggregate to form nanoparticles at low concentrations. However, at high concentrations, peptide 1 self-assembles into left-handed twisted helical fibers, while longer bamboo-like morphology can be observed exclusively for peptide 2. For peptide 3, freshly prepared samples show uniform spherical morphology, whereas an obvious morphological transition from original nanoparticles to disordered fibers was realized after incubating for one week. These fascinating morphology changes were determined by the combination of circular dichroism, dynamic light scattering, transmission electron microscopy, atomic force microscopy, and theoretical calculations. © 2020 The Author
view abstract 10.1016/j.cclet.2019.10.036
- Dual pH-Induced Reversible Self-Assembly of Gold Nanoparticles by Surface Functionalization with Zwitterionic Ligands
He, H. and Ostwaldt, J.-E. and Hirschhäuser, C. and Schmuck, C. and Niemeyer, J.
Small 16 (2020)The dual pH-induced reversible self-assembly (PIRSA) of Au-nanoparticles (Au NPs) is reported, based on their decoration with the self-complementary guanidiniocarbonyl pyrrole carboxylate zwitterion (GCPZ). The assembly of such functionalized Au NPs is found at neutral pH, based on supramolecular pairing of the GCPZ groups. The resulting self-assembled system can be switched back to the disassembled state by addition of base or acid. Two predominant effects that contribute to the dual-PIRSA of Au NPs are identified, namely the ionic hydrogen bonding between the GCPZ groups, but also a strong hydrophobic effect. The contribution of each interaction is depending on the concentration of GCPZ on NPs, which allows to control the self-assembly state over a wide range of different water/solvent ratios. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
view abstract 10.1002/smll.202001044
- Functionalized Macrocycles in Supramolecular Organocatalysis
Kauerhof, D. and Niemeyer, J.
ChemPlusChem 85 (2020)Supramolecular organocatalysis has emerged as a novel research field in the context of homogeneous catalysis. In particular, the use of functionalized macrocycles as supramolecular catalysts is highly promising, as these systems are oftentimes easily accessible and offer distinct advantages in catalysis. Macrocyclic catalysts can provide defined binding pockets, such as hydrophobic cavities, and can thus create a reaction microenvironment for catalysis. In addition, macrocycles can offer a preorganized arrangement of functional groups, such as binding sites or catalytically active groups, thus enabling a defined and possibly multivalent binding and activation of substrates. The aim of this Minireview is to provide an overview of recent advances in the area of supramolecular organocatalysis based on functionalized macrocycles (including cyclodextrins, calixarenes, and resorcinarenes), with a focus on those examples where certain catalytically active groups (such as hydrogen bond donors/acceptors, Brønsted acid or base groups, or nucleophilic units) are present in or have been installed on the macrocycles. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
view abstract 10.1002/cplu.202000152
- Guanidiniocarbonyl-Pyrroles (GCP) – 20 Years of the Schmuck Binding Motif
Giese, M. and Niemeyer, J. and Voskuhl, J.
ChemPlusChem 85 (2020)In this Minireview, an overview about the past 20 years of the guanidiniocarbonyl-pyrrole (GCP) binding motif, which was designed, investigated and applied by Prof. Dr. Carsten Schmuck, is presented. Here we highlight the first steps from design and discovery, initial binding studies, applications in material science to advanced biomedical use in protein modulation and delivery of genetic material. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
view abstract 10.1002/cplu.202000142
- Heterobifunctional Rotaxanes for Asymmetric Catalysis
Pairault, N. and Zhu, H. and Jansen, D. and Huber, A. and Daniliuc, C.G. and Grimme, S. and Niemeyer, J.
Angewandte Chemie - International Edition 59 (2020)Heterobifunctional rotaxanes serve as efficient catalysts for the addition of malonates to Michael acceptors. We report a series of four different heterobifunctional rotaxanes, featuring an amine-based thread and a chiral 1,1′-binaphthyl-phosphoric-acid-based macrocycle. High-level DFT calculations provided mechanistic insights and enabled rational catalyst improvements, leading to interlocked catalysts that surpass their non-interlocked counterparts in terms of reaction rates and stereoselectivities. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
view abstract 10.1002/anie.201913781
- Multi-Stimuli-Responsive Supramolecular Polymers Based on Noncovalent and Dynamic Covalent Bonds
Hatai, J. and Hirschhäuser, C. and Niemeyer, J. and Schmuck, C.
ACS Applied Materials and Interfaces 12 (2020)Several modes of supramolecular assembly relying on noncovalent as well as dynamic covalent interactions were combined in a single molecule. The supramolecular self-assembly of 1 can be controlled by three stimuli, namely light, pH, and addition of metal ions, in both organic and aqueous media. The multi-stimuli-responsive nature of 1 was used successfully for the controlled encapsulation and on-demand release of hydrophobic molecules, such as dyes and drugs. © 2019 American Chemical Society.
view abstract 10.1021/acsami.9b19279
- Synthesis of Bis-BINOL Derivatives: Linking via the 3-, 4-, or 5-Position by Generation of Suitable C 1 -Symmetric Precursors
Kohlhaas, M. and Lutz, F. and Paransothy, N. and Octa-Smolin, F. and Wölper, C. and Niemeyer, J.
Synthesis (Germany) 52 (2020)Bis-BINOL derivatives have proven highly useful in applications such as chemosensing or organocatalysis. In this account, we describe strategies for the linking of BINOL units via the 3-, 4-, or 5-positions, showing that unique synthetic strategies are necessary to address each position. We report the synthesis of suitable C 1 -symmetric precursors, which are generated either by monohalogenation or by monodeprotection of C 2 -symmetric starting materials, and their subsequent coupling to give linked bis-BINOL derivatives. © 2020 American Institute of Physics Inc.. All rights reserved.
view abstract 10.1055/s-0039-1690763
- What is the role of acid-acid interactions in asymmetric phosphoric acid organocatalysis? A detailed mechanistic study using interlocked and non-interlocked catalysts
Jansen, D. and Gramüller, J. and Niemeyer, F. and Schaller, T. and Letzel, M.C. and Grimme, S. and Zhu, H. and Gschwind, R.M. and Niemeyer, J.
Chemical Science 11 (2020)Organocatalysis has revolutionized asymmetric synthesis. However, the supramolecular interactions of organocatalysts in solution are often neglected, although the formation of catalyst aggregates can have a strong impact on the catalytic reaction. For phosphoric acid based organocatalysts, we have now established that catalyst-catalyst interactions can be suppressed by using macrocyclic catalysts, which react predominantly in a monomeric fashion, while they can be favored by integration into a bifunctional catenane, which reacts mainly as phosphoric acid dimers. For acyclic phosphoric acids, we found a strongly concentration dependent behavior, involving both monomeric and dimeric catalytic pathways. Based on a detailed experimental analysis, DFT-calculations and direct NMR-based observation of the catalyst aggregates, we could demonstrate that intermolecular acid-acid interactions have a drastic influence on the reaction rate and stereoselectivity of asymmetric transfer-hydrogenation catalyzed by chiral phosphoric acids. © The Royal Society of Chemistry 2020.
view abstract 10.1039/d0sc01026j
- Chiral hydrogen-bonded supramolecular capsules: Synthesis, characterization and complexation of C70
Kohlhaas, M. and Zähres, M. and Mayer, C. and Engeser, M. and Merten, C. and Niemeyer, J.
Chemical Communications 55 (2019)Two supramolecular nanocapsules were generated by multi-component self-assembly of the novel bisphosphoric acid (R,R)-6 with suitable bis- and trisamidines. The resulting chiral, hydrogen-bonded capsules are stable even in polar media and at low concentrations and can be employed for the binding of C70-fullerene in solution. © 2019 The Royal Society of Chemistry.
view abstract 10.1039/c8cc10152c
- Cooperative Organocatalysis: A Systematic Investigation of Covalently Linked Organophosphoric Acids for the Stereoselective Transfer Hydrogenation of Quinolines
Thölke, S. and Zhu, H. and Jansen, D. and Octa-Smolin, F. and Thiele, M. and Kaupmees, K. and Leito, I. and Grimme, S. and Niemeyer, J.
European Journal of Organic Chemistry 2019 (2019)A series of covalently linked bis- and trisphosphoric acids was investigated for their application in the stereoselective transfer-hydrogenation of quinolines. In a combined experimental and theoretical study, it was found that the number and relative positioning of the chiral 1,1′-binaphthyl-phosphoric acid groups strongly influences the stereoselectivity of the reaction, based on two competing reaction mechanisms. While a single 3-monosubstituted phosphoric acid moiety gives rise to little enantioselectivity, correct positioning of two phosphoric acids allows a cooperative mechanism, resulting in significantly higher stereoselectivities. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
view abstract 10.1002/ejoc.201900548
- Trend report: Organic chemistry [Organische Chemie]
Andexer, J.N. and Beifuss, U. and Beuerle, F. and Brasholz, M. and Breinbauer, R. and Ernst, M. and Gulder, T.A.M. and Kath-Schorr, S. and Kordes, M. and Lehmann, M. and Lindel, T. and Lüdeke, S. and Luy, B. and Mantel, M. and Mück-Lichtenfeld, C. and Muhle-Goll, C. and Narine, A. and Niemeyer, J. and Pfau, R. and Pietruszka, J. and Schaschke, N. and Senge, M.O. and Straub, B.F. and Werner, T. and Werz, D.B. and Winter, C.
Nachrichten aus der Chemie 67 (2019)
view abstract 10.1002/nadc.20194085243
- Asymmetrische Katalyse mit DNA
Lutz, F. and Niemeyer, J.
Nachrichten aus der Chemie 66 (2018)
view abstract 10.1002/nadc.20184076961
- Chiral Mechanically Interlocked Molecules - Applications of Rotaxanes, Catenanes and Molecular Knots in Stereoselective Chemosensing and Catalysis
Pairault, N. and Niemeyer, J.
Synlett 29 (2018)Interlocked molecules, such as rotaxanes, catenanes, and molecular knots, offer conceptually new possibilities for the generation of chiral chemosensors and catalysts. Due to the presence of the mechanical or topological bond, interlocked molecules can be used to design functional systems with unprecedented features, such as switchability and deep binding cavities. In addition, classical elements of chirality can be supplemented with mechanical or topological chirality, which have so far only scarcely been employed as sources of chirality for stereoselective applications. This minireview discusses recent examples in this emerging area, showing that the application of chiral interlocked molecules in sensing and catalysis offers many fascinating opportunities for future research. 1 Introduction 2 Interlocked Molecules with Chiral Subcomponents 2.1 Point Chirality 2.2 Axial Chirality 3 Mechanically Chiral Interlocked Molecules 4 Topologically Chiral Interlocked Molecules 5 Outlook. © Georg Thieme Verlag Stuttgart New York.
view abstract 10.1055/s-0036-1591934
- Chiral Receptors for Lysine Based on Covalently Linked Bis- and Tris-binaphthylphosphoric Acids
Octa-Smolin, F. and Thiele, M. and Yadav, R. and Platzek, A. and Clever, G.H. and Niemeyer, J.
Organic Letters 20 (2018)The synthesis and application of three chiral receptors based on the covalent linkage of 1,1′-binaphthylphosphoric acids is reported. The binding of the lysine enantiomers to the chiral receptors was investigated by DOSY-NMR and NMR titrations, revealing that the bisphosphoric acid 1d acts as a highly stereoselective receptor for binding of d-lysine. © 2018 American Chemical Society.
view abstract 10.1021/acs.orglett.8b02619
- Dual Brønsted-acid Organocatalysis: Cooperative Asymmetric Catalysis with Combined Phosphoric and Carboxylic Acids
Mitra, R. and Niemeyer, J.
ChemCatChem (2018)How can an assisting Brønsted-acid be beneficial in asymmetric Brønsted-acid catalysis? In this Minireview, we discuss selected examples of chiral organocatalysts that feature two acidic groups working cooperatively by virtue of intra- or intermolecular hydrogen-bonding. In these systems, the assisting Brønsted-acid can play different roles, ranging from simple hydrogen-bond donation, to substrate-binding or even as a nucleophilic reaction partner. By analysis of combined experimental, structural and theoretical data, we aim at developing a better understanding of the reaction mechanisms, which are largely influenced by the underlying intramolecular- and intermolecular catalyst-substrate interactions. This may aid in the future development of more selective dual Brønsted-acid organocatalysts for specific asymmetric transformations. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
view abstract 10.1002/cctc.201701698
- Stereoselective Sensing of l- and d-Amino Acids: Development of a Fluorescence-Array Based on Readily Available Chiral Phosphoric Acids
Octa-Smolin, F. and Niemeyer, J.
Chemistry - A European Journal 24 (2018)The identification of structurally related analytes has become possible using sensor arrays, based on sets of cross-reactive chemosensors. This work reports the use of readily available chiral phosphoric acids for the array-based, chemo- and stereoselective sensing of l- and d-amino acids. Six bis- and trisphosphoric acids were used in combination with Ni2+ and Eu3+, resulting in a set of twelve chiral fluorescent chemosensors. This sensor-array enables a correct classification of l-amino acids with 100 % accuracy, while the differentiation between l- and d-amino acids can be achieved with 94 % accuracy. In addition, the systematic analysis of sensor contributions has allowed the use of a reduced set of seven sensors for the classification of l-amino acids, thus drastically reducing the amount of necessary measurements. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
view abstract 10.1002/chem.201805003
- Synthese im Blickpunkt: Durch aktive Template zu verzahnten MolekÃ¼len
Pairault, N. and Niemeyer, J.
Nachrichten aus der Chemie 66 (2018)
view abstract 10.1002/nadc.20184081599
- Synthesis of Furan-Annelated BINOL Derivatives: Acid-Catalyzed Cyclization Induces Partial Racemization
Octa-Smolin, F. and Van Der Vight, F. and Yadav, R. and Bhangu, J. and Soloviova, K. and Wölper, C. and Daniliuc, C.G. and Strassert, C.A. and Somnitz, H. and Jansen, G. and Niemeyer, J.
Journal of Organic Chemistry 83 (2018)In this account, we describe the synthesis of a series of BINOL-based bis- and trisphosphoric acids 11d/e/f, which commonly feature an unusual phosphoric acid monoester motif. This motif is generated by an acid-catalyzed 5-endo-dig cyclization of the 3-alkynyl-substituted BINOL precursors to give the corresponding Furan-annelated derivatives, followed by phosphorylation of the remaining phenolic alcohols. In the cyclization reaction, we observed an unexpected partial racemization in the bis- and tris-BINOL scaffolds, leading to mixtures of diastereomers that were separated and characterized spectroscopically and by X-ray crystal structure analyses. The cyclization and racemization processes were investigated both experimentally and by DFT-calculations, showing that although the cyclization proceeds faster, the barrier for the acid-catalyzed binaphthyl-racemization is only slightly higher. © 2018 American Chemical Society.
view abstract 10.1021/acs.joc.8b02353
- Functional Mechanically Interlocked Molecules: Asymmetric Organocatalysis with a Catenated Bifunctional Brønsted Acid
Mitra, R. and Zhu, H. and Grimme, S. and Niemeyer, J.
Angewandte Chemie - International Edition 56 (2017)Interlocked molecules, such as catenanes, rotaxanes, and molecular knots, have become interesting candidates for the development of sophisticated chemical catalysts. Herein, we report the first application of a catenane-based catalyst in asymmetric organocatalysis, revealing that the catenated catalyst shows dramatically increased stereoselectivities (up to 98 % ee) in comparison to its non-interlocked analogues. A mechanistic rationale for the observed differences was developed by DFT studies, suggesting that the involvement of two catalytically active groups in the stereodetermining reaction step is responsible for the superior selectivity of the interlocked catalyst. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
view abstract 10.1002/anie.201704647
- Rigidly Tethered Bis-phosphoric Acids: Generation of Tunable Chiral Fluorescent Frameworks and Unexpected Selectivity for the Detection of Ferric Ions
Octa-Smolin, F. and Mitra, R. and Thiele, M. and Daniliuc, C.G. and Stegemann, L. and Strassert, C. and Niemeyer, J.
Chemistry - A European Journal 23 (2017)We describe the straightforward synthesis of a series of bis-phosphoric acids (R,R)-1 a–d, featuring two chiral 1,1′-binaphthyl-phosphoric acid units that are tethered by rigid, π-conjugated linkers. The nature of the linker has a profound influence on the properties of the bis-phosphoric acids, such as their self-association behavior and their interaction with metal ions. This led to the identification of one preferred bis-phosphoric acid (R,R)-1 d, which shows selective fluorescence quenching in the presence of ferric ions (Fe3+). Thus, (R,R)-1 d could be applied for the detection of Fe3+, even in the presence of a variety of other metal ions. The chiral nature of the bis-phosphoric acid enables the interaction with Fe3+ to be followed by CD spectroscopy, providing a complementary detection mode with the same probe. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
view abstract 10.1002/chem.201700954
- A bifunctional chiral catenane based on 1,1′-binaphthyl-phosphates
Mitra, R. and Thiele, M. and Octa-Smolin, F. and Letzel, M.C. and Niemeyer, J.
Chemical Communications 52 (2016)A novel catenane was synthesised by ring-closing metathesis from a Ca-bisphosphate template. The resulting interlocked structure features two chiral 1,1′-binaphthyl-phosphates, leading to a bifunctional catenane structure. Initial binding studies point at the applicability of such mechanically interlocked bisphosphates as artificial receptors for dicationic guest molecules. © The Royal Society of Chemistry 2016.
view abstract 10.1039/c6cc01980c
- Verzahnte Moleküle für die Katalyse
Nachrichten aus der Chemie 64 (2016)
view abstract 10.1002/nadc.20164046026
- Erratum: Iminoborylene complexes: evaluation of synthetic routes towards BN-allenylidenes and unexpected reactivity towards carbodiimides (Dalton Trans. (2015) 10.1039/c5dt00131e)
Niemeyer, J. and Kelly, M.J. and Riddlestone, I.M. and Vidovic, D. and Aldridge, S.
Dalton Transactions 44 (2015)
view abstract 10.1039/c5dt90082d
- Iminoborylene complexes: evaluation of synthetic routes towards BN-allenylidenes and unexpected reactivity towards carbodiimides
Niemeyer, J. and Kelly, M.J. and Riddlestone, I.M. and Vidovic, D. and Aldridge, S.
Dalton Transactions 44 (2015)The synthetic and reaction chemistries of cationic iminoborylene complexes [L<inf>n</inf>M=B=N=CR<inf>2</inf>]+, which feature a unique heterocumulene structure, have been systematically investigated. Precursors of the type CpFe(CO)<inf>2</inf>B(Cl)NCAr<inf>2</inf> (Ar = p-Tol/Mes, 5c/d) have been generated by B-centred substitution chemistry using CpFe(CO)<inf>2</inf>BCl<inf>2</inf> and suitable lithiated ketimines - a reaction which is found to be highly sensitive to the steric bulk at both the metal fragment and the ketimino group. Carbonyl/phosphine exchange (using PCy<inf>3</inf> or PPh<inf>3</inf>), followed by halide abstraction allows for the generation of the cationic iminoborylenes [CpFe(PR<inf>3</inf>)(CO)(BNCAr<inf>2</inf>)]+[BArX <inf>4</inf>]- (R = Cy, Ar = p-Tol/Mes, 12c/d; R = Ph, Ar = Mes, 13d; ArX = 3,5-X<inf>2</inf>C<inf>6</inf>H<inf>3</inf> where X = Cl, CF<inf>3</inf>) which have been characterized spectroscopically and by X-ray crystallography. The reactivity of these iminoborylene systems towards a range of nucleophiles and unsaturated substrates has been investigated. The latter includes the first examples of M=B metathesis reactivity with a carbodiimide, and results in Fe=B cleavage and formation of the isonitrile complexes [CpFe(PCy<inf>3</inf>)(CO)(CNR)]+[BArCl <inf>4</inf>]- (R = iPr/Cy, 16/17). © The Royal Society of Chemistry.
view abstract 10.1039/c5dt00131e
- Corrigendum: Fullerene-Mediated Activation of Dihydrogen: A New Method of Metal-Free Catalytic Hydrogenation
Niemeyer, J. and Erker, G.
ChemCatChem 3 (2011)
view abstract 10.1002/cctc.201190015
- Extending the chain: Synthetic, structural, and reaction chemistry of a BN allenylidene analogue
Niemeyer, J. and Addy, D.A. and Riddlestone, I. and Kelly, M. and Thompson, A.L. and Vidovic, D. and Aldridge, S.
Angewandte Chemie - International Edition 50 (2011)α versus γ: [CpFe(CO)(PCy3)(BNCMes 2)]+, synthesized by halide abstraction, represents the first example of a BN allenylidene analogue, and features an unsaturated MBNC π system. Although DFT calculations show significant LUMO amplitude at the γ (carbon) position, primary reactivity towards nucleophiles occurs at the sterically less hindered α (boron) center. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
view abstract 10.1002/anie.201103757
- Modelling fundamental arene-borane contacts: Spontaneous formation of a dibromoborenium cation driven by interaction between a borane Lewis acid and an arene π system
Mansaray, H.B. and Rowe, A.D.L. and Phillips, N. and Niemeyer, J. and Kelly, M. and Addy, D.A. and Bates, J.I. and Aldridge, S.
Chemical Communications 47 (2011)Reaction of 2,6-dimesityl pyridine (Lpy) with BBr3 leads to the spontaneous formation of the trigonal dibromoborenium cation [Lpy·BBr2]+via bromide ejection. Systematic structural and computational studies, and the reactivity displayed by a closely related N-heterocyclic carbene (NHC) donor, reveal the role played by arene-borane interactions in this chemistry. [Lpy·BBr 2]+ features a structurally characterized (albeit weak) electrostatic interaction between the borane Lewis acid and flanking arene π systems. © 2011 The Royal Society of Chemistry.
view abstract 10.1039/c1cc15259a
- Fullerene-Mediated Activation of Dihydrogen: A New Method of Metal-Free Catalytic Hydrogenation
Niemeyer, J. and Erker, G.
ChemCatChem 2 (2010)
view abstract 10.1002/cctc.201000038
- Salen ligands revisited: synthesis and application of a planar chiral "Ferro-salen" ligand
Niemeyer, J. and Kehr, G. and Fröhlich, R. and Erker, G.
European Journal of Inorganic Chemistry (2010)Condensation of the O-protected planar chiral hydroxyferrocene carbaldehyde (Sp)-1 with ethylenedlarcime, followed by deprotection gave rise to the "ferro-salen" ligand (Sp,Sp)-3 in good yield. This scaffold was used for the preparation of a series of metal complexes [(Sp,Sp)-4/5/8], which were subsequently applied for the Lewis acid catalyzed asymmetric trimethylsilylcyanation of benzaldehyde. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
view abstract 10.1002/ejic.200901118
- Salen-ligands based on a planar-chiral hydroxyferrocene moiety: Synthesis, coordination chemistry and use in asymmetric silylcyanation
Niemeyer, J. and Cloppenburg, J. and Fröhlich, R. and Kehr, G. and Erker, G.
Journal of Organometallic Chemistry 695 (2010)Condensation of the O-protected hydroxyferrocene carbaldehyde (Sp)-1 with suitable diamines, followed by liberation of the hydroxyferrocene moiety leads to a new type of ferrocene-based salen ligands (3). While the use of ethylenediamine in the condensation reaction yields the planar-chiral ethylene-bridged ligand [(Sp,Sp)-3a], reaction with the enantiomers of trans-1,2-cyclohexylendiamine gives rise to the corresponding diastereomeric cyclohexylene-bridged systems [(S,S,Sp,Sp)-3b and (R,R,Sp,Sp)-3c], which feature a combination of a planar-chiral ferrocene unit with a centrochiral diamine backbone. Starting with the ferrocene-aldehyde derivative (Rp)-1, the enantiomeric ligand series (3d/e/f) is accessible via the same synthetic route. The (Sp)-series of these newly developed N2O2-type ligands was used for the construction of the corresponding mononuclear bis(isopropoxy)titanium (4a/b/c), methylaluminum (5a/b/c) and chloroaluminum-complexes (6a/b/c), which were isolated in good yields and identified by X-ray diffraction in several cases. The aluminum complexes (5/6) were successfully used in the Lewis-acid catalyzed addition of trimethylsilylcyanide to benzaldehyde, yielding the corresponding cyanohydrins in 45-62% enantiomeric excess. © 2010 Elsevier B.V. All rights reserved.
view abstract 10.1016/j.jorganchem.2010.04.008