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.
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Asymmetric Pinacol coupling of aromatic aldehydes catalyzed by TiCl4(THF)2-Zn/chiral diamines
Chinese Journal of Chemistry, 2010Co-Authors: Chang‐sheng Jiang, Qing‐shan Tian, Tianpa YouAbstract:Asymmetric Pinacol coupling of aromatic aldehydes catalyzed by chiral diamines/low-valent titanium complexes gave corresponding Pinacols in good yields with high diastereoselectivity and moderate enantioselectivities.
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Enantioselective Pinacol coupling of aromatic aldehydes mediated by TiCI4(THF)2/Zn with tartaric ester
Chinese Journal of Chemistry, 2010Co-Authors: Chen Jiang, Jun Zhao, Qing‐shan Tian, Tianpa YouAbstract:Asymmetric Pinacol coupling of aromatic aldehydes mediated by low valent titanium complexes of chiral ligands derived from natural tartaric acid provided corresponding Pinacols in good yields with excellent diastereo-selectivities and moderate enantioselectivities.
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Biphenyl-oxazoline ligands derived from β-DDB: Their synthesis and application in asymmetric Pinacol coupling reaction
Journal of Molecular Catalysis A-chemical, 2006Co-Authors: Jiwu Wen, Qitao Tan, Tianpa YouAbstract:Biphenyl-bisoxazoline ligands conveniently synthesized from β-DDB have been exploited in asymmetric Pinacol coupling reaction for the first time. The Pinacol products were obtained with good yields, high diastereoselectivities and good enantioselectivities (up to 83%e.e.). The stereochemistry of the diol products was dominated by the steric structure of the oxazoline component. Ligands bearing bulky groups in the chiral centre of the oxazolines showed more efficient for achieving both high diastereoselectivity and enantioselectivity.
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asymmetric Pinacol coupling of aromatic aldehydes catalyzed by a new titanium schiff base complex
Tetrahedron-asymmetry, 2004Co-Authors: Qingshan Tian, Jun Zhao, Yan Feng, Tianpa YouAbstract:Abstract A new Schiff-base with two stereogenic centers has been prepared and its titanium complex applied to catalyze the Pinacol coupling of aldehydes, which afforded Pinacols in high yield, excellent diastereoselectivities, and high enantioselectivities.
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Asymmetric Pinacol coupling of aromatic aldehydes catalyzed by a new titanium–Schiff base complex
Tetrahedron: Asymmetry, 2004Co-Authors: Qing‐shan Tian, Jun Zhao, Yan Feng, Tianpa YouAbstract:Abstract A new Schiff-base with two stereogenic centers has been prepared and its titanium complex applied to catalyze the Pinacol coupling of aldehydes, which afforded Pinacols in high yield, excellent diastereoselectivities, and high enantioselectivities.
Jean Raynaud - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Networks High Glass-Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
Angewandte Chemie, 2019Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean RaynaudAbstract: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.
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High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
Angewandte Chemie International Edition, 2019Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean RaynaudAbstract: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.
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Enantioselective Pinacol coupling of aromatic aldehydes mediated by TiCI4(THF)2/Zn with tartaric ester
Chinese Journal of Chemistry, 2010Co-Authors: Chen Jiang, Jun Zhao, Qing‐shan Tian, Tianpa YouAbstract:Asymmetric Pinacol coupling of aromatic aldehydes mediated by low valent titanium complexes of chiral ligands derived from natural tartaric acid provided corresponding Pinacols in good yields with excellent diastereo-selectivities and moderate enantioselectivities.
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Asymmetric Pinacol coupling of aromatic aldehydes catalyzed by TiCl4(THF)2-Zn/chiral diamines
Chinese Journal of Chemistry, 2010Co-Authors: Chang‐sheng Jiang, Qing‐shan Tian, Tianpa YouAbstract:Asymmetric Pinacol coupling of aromatic aldehydes catalyzed by chiral diamines/low-valent titanium complexes gave corresponding Pinacols in good yields with high diastereoselectivity and moderate enantioselectivities.
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Asymmetric Pinacol coupling of aromatic aldehydes catalyzed by a new titanium–Schiff base complex
Tetrahedron: Asymmetry, 2004Co-Authors: Qing‐shan Tian, Jun Zhao, Yan Feng, Tianpa YouAbstract:Abstract A new Schiff-base with two stereogenic centers has been prepared and its titanium complex applied to catalyze the Pinacol coupling of aldehydes, which afforded Pinacols in high yield, excellent diastereoselectivities, and high enantioselectivities.
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Experimental and theoretical investigation of the relationship between the stericstructure of Schiff bases and the diastereoselectivity of Pinacol produced from benzaldehyde
Journal of Molecular Catalysis A: Chemical, 2004Co-Authors: Qing‐shan Tian, Chen Jiang, Changsheng Jiang, Tianpa YouAbstract:Abstract After synthesis of a series of chiral Schiff bases from easily available amino-alcohol, Pinacol coupling reaction of benzaldehyde catalyzed by a series of Schiff bases–Ti complexes afforded Pinacol with high yield and different diastereoselectivity. The relationship between the stericstructure of these Schiff bases and the diastereoselectivity of Pinacol was systemically studied and calculated by QSAR calculation method.
Juliette Brunet - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Networks High Glass-Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
Angewandte Chemie, 2019Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean RaynaudAbstract: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.
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High Glass‐Transition Temperature Polymer Networks Harnessing the Dynamic Ring Opening of Pinacol Boronates
Angewandte Chemie International Edition, 2019Co-Authors: Juliette Brunet, Franck Collas, Matthieu Humbert, Lionel Perrin, Fabrice Brunel, Emmanuel Lacôte, Damien Montarnal, Jean RaynaudAbstract: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.
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Highly Diastereo- and Enantioselective Allylboration of Aldehydes using α‑Substituted Allyl/Crotyl Pinacol Boronic Esters via in Situ Generated Borinic Esters
2016Co-Authors: Jack L Y Chen, Matthew J Hesse, Helen K. Scott, Christine L. Willis, Varinder K AggarwalAbstract: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
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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, 2013Co-Authors: Jack L Y Chen, Helen K Scott, Matthew J Hesse, Christine L Willis, Varinder K AggarwalAbstract: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.