Felix C. Raps  Dr. Vincent C. Fäseke  Prof. Dr. Daniel Häussinger  Prof. Dr. Christof Sparr 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18548-18552

The biomimetic synthesis of aromatic polyketides from macrocyclic substrates by means of catalyst-controlled transannular cyclization cascades is described. The macrocyclic substrates, which feature increased stability and fewer conformational states, were thereby transformed into several distinct polyketide scaffolds. The catalyst-controlled transannular cyclizations selectively led to aromatic polyketides with a defined folding and oxygenation pattern, thus emulating β-keto-processing steps of polyketide biosynthesis.  相似文献   

    

Dr. Song Song  Vincent Fung Kin Yuen  Dr. Lu Di  Dr. Qiming Sun  Prof. Dr. Kang Zhou  Prof. Dr. Ning Yan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20018-20022

Production of renewable, high-value N-containing chemicals from lignocellulose will expand product diversity and increase the economic competitiveness of the biorefinery. Herein, we report a single-step conversion of furfural to pyrrole in 75 % yield as a key N-containing building block, achieved via tandem decarbonylation–amination reactions over tailor-designed Pd@S-1 and H-beta zeolite catalytic system. Pyrrole was further transformed into dl -proline in two steps following carboxylation with CO₂ and hydrogenation over Rh/C catalyst. After treating with Escherichia coli, valuable d -proline was obtained in theoretically maximum yield (50 %) bearing 99 % ee. The report here establishes a route bridging commercial commodity feedstock from biomass with high-value organonitrogen chemicals through pyrrole as a hub molecule.  相似文献   

    

Dustin Bornemann  Dr. Cody Ross Pitts  Lionel Wettstein  Fabian Brüning  Sebastian Küng  Dr. Liangyu Guan  Dr. Nils Trapp  Prof. Dr. Hansjörg Grützmacher  Prof. Dr. Antonio Togni 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22982-22988

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Charlotte Menager  Nathanaël Guigo  Luc Vincent  Nicolas Sbirrazzuoli 《Journal of polymer science. Part A, Polymer chemistry》2020,58(12):1717-1727

The curing of epoxidized linseed oil (ELO) with three different bio-based dicarboxylic acids (sebacic acid, suberic acid, and succinic acid) has been investigated. No accelerators or catalysts were used and the resulting thermosets are 100% bio-based. Structural investigations of the three crosslinked ELO resins were made using FTIR spectroscopy and TMA, that is, tensile tests, TGA, and DMA. As evidenced by FTIR measurements ELO and dicarboxylic acids reacts but no major differences can be distinguished between the dicarboxylic acids. Non-isothermal curing has been conducted by rheological and DSC measurements. Advanced isoconversional analysis applied to DSC data in association with the complex viscosity variations gives new insights into the polymerization mechanism. The length of dicarboxylic acid carbon chain modifies the reaction rate. Then, a correlation between reaction rate, activation energy, pre-exponential factors, polymerization mechanism, and change in rate-limiting step was shown. DMA and tensile tests highlight the relationship between the carbon chain length, reactivity, and thermomechanical properties. The use of succinic acid allows reaching a higher T_g and thermal stability.  相似文献   

Chemistry—A European Journal Turns 25     

Dr. Haymo Ross 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(1):5-8

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Dr. Franck Ulm  Dr. Yann Cornaton  Dr. Jean-Pierre Djukic  Prof. Michael J. Chetcuti  Prof. Vincent Ritleng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8916-8925

The pentamethylcyclopentadienyl N-heterocyclic carbene nickel complex [Ni(η⁵-C₅Me₅)Cl(IMes)] (IMes=1,3-dimesitylimidazol-2-ylidene) efficiently catalyses the anti-Markovnikov hydroboration of alkenes with catecholborane in the presence of a catalytic amount of potassium tert-butoxide, and joins the very exclusive club of nickel catalysts for this important transformation. Interestingly, the regioselectivity can be reversed in some cases by using pinacolborane instead of catecholborane. Mechanistic investigations involving control experiments, ¹H and ¹¹B NMR spectroscopy, cyclic voltammetry, piezometric measurements and DFT calculations suggest an initial reduction of the Ni^II precursor to a Ni^I active species with the concomitant release of H₂. The crucial role of the alkoxo-catecholato-borohydride species resulting from the reaction of potassium tert-butoxide with catecholborane in the formation of an intermediate nickel-hydride species that would then be reduced to the Ni^I active species, is highlighted.  相似文献   

    

Evan Terrell  Dr. Vincent Carré  Dr. Anthony Dufour  Dr. Frédéric Aubriet  Dr. Yann Le Brech  Dr. Manuel Garcia-Pérez 《ChemSusChem》2020,13(17):4428-4445

The lack of standards to identify oligomeric molecules is a challenge for the analysis of complex organic mixtures. High-resolution mass spectrometry—specifically, Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS)—offers new opportunities for analysis of oligomers with the assignment of formulae (C_xH_yO_z) to detected peaks. However, matching a specific structure to a given formula remains a challenge due to the inability of FT-ICR MS to distinguish between isomers. Additional separation techniques and other analyses (e.g., NMR spectroscopy) coupled with comparison of results to those from pure compounds is one route for assignment of MS peaks. Unfortunately, this strategy may be impractical for complete analysis of complex, heterogeneous samples. In this study we use computational stochastic generation of lignin oligomers to generate a molecular library for supporting the assignment of potential candidate structures to compounds detected during FT-ICR MS analysis. This approach may also be feasible for other macromolecules beyond lignin.  相似文献   

    

Ross S. Forgan 《Chemical science》2020,11(18):4546

Exercising fine control over the synthesis of metal–organic frameworks (MOFs) is key to ensuring reproducibility of physical properties such as crystallinity, particle size, morphology, porosity, defectivity, and surface chemistry. The principle of modulated self-assembly – incorporation of modulator molecules into synthetic mixtures – has emerged as the primary means to this end. This perspective article will detail the development of modulated synthesis, focusing primarily on coordination modulation, from a technique initially intended to cap the growth of MOF crystals to one that is now used regularly to enhance crystallinity, control particle size, induce defectivity and select specific phases. The various mechanistic driving forces will be discussed, as well as the influence of modulation on physical properties and how this can facilitate potential applications. Modulation is also increasingly being used to exert kinetic control over self-assembly; examples of phase selection and the development of new protocols to induce this will be provided. Finally, the application of modulated self-assembly to alternative materials will be discussed, and future perspectives on the area given.

This Perspective gives an overview of the modulated self-assembly of MOFs – incorporating additives and alternative precursors into syntheses – focusing on its varying influences on crystallization mechanisms, physical properties, and applications.  相似文献   

    

Margaret C. Gerthoffer  Sikai Wu  Bo Chen  Tao Wang  Steven Huss  Shalisa M. Oburn  Vincent H. Crespi  John V. Badding  Elizabeth Elacqua 《Chemical science》2020,11(42):11419

Limited supramolecular strategies have been utilized to synthesize sequence-defined polymers, despite the prominence of noncovalent interactions in materials design. Herein, we illustrate the utility of ‘sacrificial’ aryl-perfluoroaryl supramolecular synthons to synthesize sp³-hybridized nanothreads from sp²-enriched reactants. Our strategy features A–B reactant pairs in the form of a phenol:pentafluorophenol co-crystal that is preorganized for an electronically-biased and sequence-defined polymerization. The polymerization, initiated at 12 GPa, affords an alternating copolymer featuring exogenous –OH functionalities. The external substitution is confirmed through IR spectroscopy. Importantly, the inclusion of the functional unit provides the first experimental glimpse at reaction mechanism: keto–enol tautomerization that can only occur during cycloaddition is observed through IR spectroscopy. Our approach realizes the first example of a functionalized nanothread and attains sequence definition through sacrificial supramolecular preorganization and presents a further approach for de novo design of complex nanothreads.

Supramolecular synthons are exploited to synthesize –OH functionalized sp³-rich sequence-defined nanothreads using pressure-induced polymerization of a phenol:pentafluorophenol co-crystal.   相似文献   

    

Cécile Cadoux  Dr. Ross D. Milton 《ChemElectroChem》2020,7(9):1974-1986

Enzymatic electrochemistry is the coupling of oxidoreductase enzymes to electrodes, where electrons are transferred between the electrode and an enzyme's cofactor(s). In addition to enzymatic electrochemistry enabling mechanistic study [such as the determination of cofactor reduction potential(s)], enzymatic electrocatalysis also enables substrate reduction or oxidation by exploiting the catalytic properties of enzymes. This Minireview illustrates some recent examples, in which electrodes are coupled with enzymes that catalyze the reduction of substrates such as dinitrogen (N₂), carbon dioxide (CO₂) and protons (H⁺), performed by metalloenzymes such as nitrogenases, formate dehydrogenases and hydrogenases. We review some strategies to achieve electron transfer (such as mediated and direct electron transfer), as well as some key results of recent studies.  相似文献