Pinacol

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The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform

Tianpa You - One of the best experts on this subject based on the ideXlab platform.

Jean Raynaud - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Networks High Glass-Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
    Angewandte Chemie, 2019
    Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean Raynaud
    Abstract:

    Differential scanning calorimetry of high molar mass poly(4-vinylphenylboronic acid, Pinacol ester)s evi-denced unusual reactive events above 120 8 8C, resulting in ahigh glass-transition temperature of 220 8 8C. Areversible ring-opening reactivity of Pinacol boronates is proposed, involving anucleophilic attackonthe sp 2 boron and subsequent bridging between boron atoms by interconnected Pinacol moieties to form adensely crosslinked network with high T g .FTIR, solid-state NMR investigations,and rheology studies on the polymer as well as double-tagging analyses on molecular model structures and theoretical calculations further support this hypothesis and indicate ar ing-opening inducing crosslinking. When diluted in an apolar solvent such as toluene,the polymer network can be resolubilized via ring closing,t hus recovering the entropically favored linear chains featuring cyclic boronate esters.

  • High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
    Angewandte Chemie International Edition, 2019
    Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean Raynaud
    Abstract:

    Differential scanning calorimetry of high molar mass poly(4-vinylphenylboronic acid, Pinacol ester)s evidenced unusual reactive events above 120°C, resulting in a high glass transition temperature of 220°C. We hypothesize a ring-opening reactivity of Pinacol boronates involving a nucleophilic attack on the sp 2 boron and subsequent bridging by interconnected Pinacol moieties to form a densely crosslinked network with high-Tg. FTIR, solid-state NMR investigations and rheology studies on the polymer as well as double-tagging analyses on molecular model structures and theoretical calculations further support this hypothesis and indicate an entropy-driven ring opening inducing crosslinking. When diluted in an apolar solvent such as toluene, the polymer network can be resolubilized via ring closing thus recovering the entropically-favoured linear chains featuring cyclic boronate esters. The introduction of boron reactivity in polymer chains may open a path to a new class of dynamic polymer networks with uncommon and exciting thermodynamics.

Qing‐shan Tian - One of the best experts on this subject based on the ideXlab platform.

Juliette Brunet - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Networks High Glass-Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
    Angewandte Chemie, 2019
    Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean Raynaud
    Abstract:

    Differential scanning calorimetry of high molar mass poly(4-vinylphenylboronic acid, Pinacol ester)s evi-denced unusual reactive events above 120 8 8C, resulting in ahigh glass-transition temperature of 220 8 8C. Areversible ring-opening reactivity of Pinacol boronates is proposed, involving anucleophilic attackonthe sp 2 boron and subsequent bridging between boron atoms by interconnected Pinacol moieties to form adensely crosslinked network with high T g .FTIR, solid-state NMR investigations,and rheology studies on the polymer as well as double-tagging analyses on molecular model structures and theoretical calculations further support this hypothesis and indicate ar ing-opening inducing crosslinking. When diluted in an apolar solvent such as toluene,the polymer network can be resolubilized via ring closing,t hus recovering the entropically favored linear chains featuring cyclic boronate esters.

  • High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
    Angewandte Chemie International Edition, 2019
    Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean Raynaud
    Abstract:

    Differential scanning calorimetry of high molar mass poly(4-vinylphenylboronic acid, Pinacol ester)s evidenced unusual reactive events above 120°C, resulting in a high glass transition temperature of 220°C. We hypothesize a ring-opening reactivity of Pinacol boronates involving a nucleophilic attack on the sp 2 boron and subsequent bridging by interconnected Pinacol moieties to form a densely crosslinked network with high-Tg. FTIR, solid-state NMR investigations and rheology studies on the polymer as well as double-tagging analyses on molecular model structures and theoretical calculations further support this hypothesis and indicate an entropy-driven ring opening inducing crosslinking. When diluted in an apolar solvent such as toluene, the polymer network can be resolubilized via ring closing thus recovering the entropically-favoured linear chains featuring cyclic boronate esters. The introduction of boron reactivity in polymer chains may open a path to a new class of dynamic polymer networks with uncommon and exciting thermodynamics.

Varinder K Aggarwal - One of the best experts on this subject based on the ideXlab platform.

  • Highly Diastereo- and Enantioselective Allylboration of Aldehydes using α‑Substituted Allyl/Crotyl Pinacol Boronic Esters via in Situ Generated Borinic Esters
    2016
    Co-Authors: Jack L Y Chen, Matthew J Hesse, Helen K. Scott, Christine L. Willis, Varinder K Aggarwal
    Abstract:

    Readily available, α-substituted allyl/crotyl Pinacol boronic esters often give low E/Z selectivity (with Z favored) in reactions with aldehydes. We found that addition of nBuLi to the Pinacol boronic ester followed by trapping of the alkoxide with TFAA leads to an intermediate allyl borinic ester which undergoes allylboration with very high E selectivity. The substrate scope includes primary to tertiary alkyl α-substituents, crotyl substrates, and the previously unreported β-methallyl Pinacol boronic esters. The latter give very high Z selectivity under standard conditions which is completely reversed to high E selectivity under the new conditions. Monitoring the reaction by 11B NMR confirmed that the reaction proceeds through a borinic ester intermediate

  • highly diastereo and enantioselective allylboration of aldehydes using α substituted allyl crotyl Pinacol boronic esters via in situ generated borinic esters
    Journal of the American Chemical Society, 2013
    Co-Authors: Jack L Y Chen, Helen K Scott, Matthew J Hesse, Christine L Willis, Varinder K Aggarwal
    Abstract:

    Readily available, α-substituted allyl/crotyl Pinacol boronic esters often give low E/Z selectivity (with Z favored) in reactions with aldehydes. We found that addition of nBuLi to the Pinacol boronic ester followed by trapping of the alkoxide with TFAA leads to an intermediate allyl borinic ester which undergoes allylboration with very high E selectivity. The substrate scope includes primary to tertiary alkyl α-substituents, crotyl substrates, and the previously unreported β-methallyl Pinacol boronic esters. The latter give very high Z selectivity under standard conditions which is completely reversed to high E selectivity under the new conditions. Monitoring the reaction by 11B NMR confirmed that the reaction proceeds through a borinic ester intermediate.