20 research outputs found

    Retail Clerks International Protective Association, Local 872 (1936)

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    Improved methods for quickly identifying neutral organic compounds and differentiation of analytes with similar chemical structures are widely needed. We report a new approach to effectively “fingerprint” neutral organic molecules by using <sup>19</sup>F NMR and molecular containers. The encapsulation of analytes induces characteristic up- or downfield shifts of <sup>19</sup>F resonances that can be used as multidimensional parameters to fingerprint each analyte. The strategy can be achieved either with an array of fluorinated receptors or by incorporating multiple nonequivalent fluorine atoms in a single receptor. Spatial proximity of the analyte to the <sup>19</sup>F is important to induce the most pronounced NMR shifts and is crucial in the differentiation of analytes with similar structures. This new scheme allows for the precise and simultaneous identification of multiple analytes in a complex mixture

    Simultaneous Chirality Sensing of Multiple Amines by <sup>19</sup>F NMR

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    The rapid detection and differentiation of chiral compounds is important to synthetic, medicinal, and biological chemistry. Palladium complexes with chiral pincer ligands are demonstrated to have utility in determining the chirality of various amines. The binding of enantiomeric amines induces distinct <sup>19</sup>F NMR shifts of the fluorine atoms appended on the ligand that defines a chiral environment around palladium. It is further demonstrated that this method has the ability to evaluate the enantiomeric composition and discriminate between enantiomers with chiral centers several carbons away from the binding site. The wide detection window provided by optimized chiral chemosensors allows the simultaneous identification of as many as 12 chiral amines. The extraordinary discriminating ability of this method is demonstrated by the resolution of chiral aliphatic amines that are difficult to separate using chiral chromatography

    Bioinspired Organic Porous Coupling Agent for Enhancement of Nanoparticle Dispersion and Interfacial Strength

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    Composite materials have significantly advanced with the integration of inorganic nanoparticles as fillers in polymers. Achieving fine dispersion of these nanoparticles within the composites, however, remains a challenge. This study presents a novel solution inspired by the natural structure of Xanthium. We have developed a polymer of intrinsic microporosity (PIM)-based porous coupling agent, named PCA. PCA’s rigid backbone structure enhances interfacial interactions through a unique intermolecular interlocking mechanism. This approach notably improves the dispersion of SiO2 nanoparticles in various organic solvents and low-polarity polymers. Significantly, PCA-modified SiO2 nanoparticles embedded in polyisoprene rubber showed enhanced mechanical properties. The Young’s modulus increases to 30.7 MPa, compared to 5.4 MPa in hexadecyltrimethoxysilane-modified nanoparticles. Further analysis shows that PCA-modified composites not only become stiffer but also gain strength and ductility. This research demonstrates a novel biomimetic strategy for enhancing interfacial interactions in composites, potentially leading to stronger, more versatile composite materials

    Detection and Differentiation of Neutral Organic Compounds by <sup>19</sup>F NMR with a Tungsten Calix[4]arene Imido Complex

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    Fluorinated tungsten calix[4]­arene imido complexes were synthesized and used as receptors to detect and differentiate neutral organic compounds. It was found that the binding of specific neutral organic molecules to the tungsten centers induces an upfield shift of the fluorine atom appended on the arylimido group, the extent of which is highly dependent on electronic and steric properties. We demonstrate that the specific bonding and size-selectivity of calix[4]­arene tungsten–imido complex combined with <sup>19</sup>F NMR spectroscopy is a powerful new method for the analysis of complex mixtures

    Detection and Differentiation of Neutral Organic Compounds by <sup>19</sup>F NMR with a Tungsten Calix[4]arene Imido Complex

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    Fluorinated tungsten calix[4]­arene imido complexes were synthesized and used as receptors to detect and differentiate neutral organic compounds. It was found that the binding of specific neutral organic molecules to the tungsten centers induces an upfield shift of the fluorine atom appended on the arylimido group, the extent of which is highly dependent on electronic and steric properties. We demonstrate that the specific bonding and size-selectivity of calix[4]­arene tungsten–imido complex combined with <sup>19</sup>F NMR spectroscopy is a powerful new method for the analysis of complex mixtures

    From Olefination to Alkylation: In-Situ Halogenation of Julia–Kocienski Intermediates Leading to Formal Nucleophilic Iodo- and Bromodifluoromethylation of Carbonyl Compounds

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    Iodo- and bromodifluoromethylated compounds are important synthetic intermediates and halogen-bond acceptors. However, direct introduction of −CF<sub>2</sub>I and −CF<sub>2</sub>Br groups through nucleophilic addition is particularly challenging because of the high tendency of decomposition of CF<sub>2</sub>Br<sup>–</sup> and CF<sub>2</sub>I<sup>–</sup> to difluorocarbene. In this work, we have developed a formal nucleophilic iodo- and bromodifluoromethylation for carbonyl compounds. The key strategy of the method is the halogenation of in situ-generated sulfinate intermediates from the Julia–Kocienski reaction to change the reaction pathway from the traditional olefination to alkylation. Interesting halogen−π interactions between the halocarbon and aromatic donors were observed in the crystal structures of the products. The method could also be extended to the introduction of other fluorinated groups, such as −CFClBr, −CFClI, −CFBr<sub>2</sub>, and −CFMeI, which opens up new avenues for the synthesis of a wide range of useful fluorinated products

    From Olefination to Alkylation: In-Situ Halogenation of Julia–Kocienski Intermediates Leading to Formal Nucleophilic Iodo- and Bromodifluoromethylation of Carbonyl Compounds

    No full text
    Iodo- and bromodifluoromethylated compounds are important synthetic intermediates and halogen-bond acceptors. However, direct introduction of −CF<sub>2</sub>I and −CF<sub>2</sub>Br groups through nucleophilic addition is particularly challenging because of the high tendency of decomposition of CF<sub>2</sub>Br<sup>–</sup> and CF<sub>2</sub>I<sup>–</sup> to difluorocarbene. In this work, we have developed a formal nucleophilic iodo- and bromodifluoromethylation for carbonyl compounds. The key strategy of the method is the halogenation of in situ-generated sulfinate intermediates from the Julia–Kocienski reaction to change the reaction pathway from the traditional olefination to alkylation. Interesting halogen−π interactions between the halocarbon and aromatic donors were observed in the crystal structures of the products. The method could also be extended to the introduction of other fluorinated groups, such as −CFClBr, −CFClI, −CFBr<sub>2</sub>, and −CFMeI, which opens up new avenues for the synthesis of a wide range of useful fluorinated products

    From Olefination to Alkylation: In-Situ Halogenation of Julia–Kocienski Intermediates Leading to Formal Nucleophilic Iodo- and Bromodifluoromethylation of Carbonyl Compounds

    No full text
    Iodo- and bromodifluoromethylated compounds are important synthetic intermediates and halogen-bond acceptors. However, direct introduction of −CF<sub>2</sub>I and −CF<sub>2</sub>Br groups through nucleophilic addition is particularly challenging because of the high tendency of decomposition of CF<sub>2</sub>Br<sup>–</sup> and CF<sub>2</sub>I<sup>–</sup> to difluorocarbene. In this work, we have developed a formal nucleophilic iodo- and bromodifluoromethylation for carbonyl compounds. The key strategy of the method is the halogenation of in situ-generated sulfinate intermediates from the Julia–Kocienski reaction to change the reaction pathway from the traditional olefination to alkylation. Interesting halogen−π interactions between the halocarbon and aromatic donors were observed in the crystal structures of the products. The method could also be extended to the introduction of other fluorinated groups, such as −CFClBr, −CFClI, −CFBr<sub>2</sub>, and −CFMeI, which opens up new avenues for the synthesis of a wide range of useful fluorinated products

    From Olefination to Alkylation: In-Situ Halogenation of Julia–Kocienski Intermediates Leading to Formal Nucleophilic Iodo- and Bromodifluoromethylation of Carbonyl Compounds

    No full text
    Iodo- and bromodifluoromethylated compounds are important synthetic intermediates and halogen-bond acceptors. However, direct introduction of −CF<sub>2</sub>I and −CF<sub>2</sub>Br groups through nucleophilic addition is particularly challenging because of the high tendency of decomposition of CF<sub>2</sub>Br<sup>–</sup> and CF<sub>2</sub>I<sup>–</sup> to difluorocarbene. In this work, we have developed a formal nucleophilic iodo- and bromodifluoromethylation for carbonyl compounds. The key strategy of the method is the halogenation of in situ-generated sulfinate intermediates from the Julia–Kocienski reaction to change the reaction pathway from the traditional olefination to alkylation. Interesting halogen−π interactions between the halocarbon and aromatic donors were observed in the crystal structures of the products. The method could also be extended to the introduction of other fluorinated groups, such as −CFClBr, −CFClI, −CFBr<sub>2</sub>, and −CFMeI, which opens up new avenues for the synthesis of a wide range of useful fluorinated products

    Spontaneous Resolution of Julia-Kocienski Intermediates Facilitates Phase Separation to Produce <i>Z</i>- and <i>E</i>‑Monofluoroalkenes

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    The monofluoroalkene motif is important in drug development as it serves as a peptide bond isostere and is found in a number of biologically active compounds with various pharmacological activities. Direct olefination of carbonyl compound is a straightforward way to prepare monofluoroalkenes; however, these methods often result in a mixture of <i>Z</i>- and <i>E</i>-isomers that cannot be easily separated. We discovered a unique spontaneous resolving reaction that simultaneously addresses the problems in the synthesis and separation of <i>Z</i>- and <i>E</i>-monofluoroalkenes. The reaction is accompanied by a highly efficient spontaneous kinetic resolution and phase labeling of monofluoroalkene precursors which allows the separation of <i>Z</i>- and <i>E</i>-monofluoroalkenes by liquid–liquid extraction. The application of the method is demonstrated by the synthesis and separation of potential anticancer agents, which are inseparable by HPLC
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