20 research outputs found
Retail Clerks International Protective Association, Local 872 (1936)
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
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
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
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
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
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
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
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
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
Copper-Mediated Fluoroalkylation of Aryl Iodides Enables Facile Access to Diverse Fluorinated Compounds: The Important Role of the (2-Pyridyl)sulfonyl Group
The (2-pyridyl)sulfonyl group was found to be a multifunctional group in the preparation of structurally diverse fluorinated products. It not only facilitates the copper-mediated (or catalyzed) cross-coupling reaction between α-fluoro sulfone 4a and aryl iodides, but also enables further transformations of the coupling products 2