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Kay Severin - One of the best experts on this subject based on the ideXlab platform.
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metal stabilized Boronate Ester cages
Inorganic Chemistry, 2021Co-Authors: Erica Giraldi, Rosario Scopelliti, Farzaneh Fadaeitirani, Kay SeverinAbstract:Molecular cages with arylBoronate Ester caps at the vertices are described. The cages were obtained by metal-templated polycondensation reactions of a tris(2-formylpyridine oxime) ligand with arylboronic acids. Suited templates are triflate or triflimide salts of ZnII, FeII, CoII, or MnII. In the products, the metal ions are coordinated internally to the pyridyl and oximato N atoms adjacent to the Boronate Ester, resulting in an improved hydrolytic stability of the latter. It is possible to decorate the cages with cyano or aldehyde groups using functionalized arylboronic acids. The aldehyde groups allow for a postsynthetic modification of the cages via an imine bond formation.
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Boronate Ester capped helicates
Chemistry: A European Journal, 2020Co-Authors: Erica Giraldi, Rosario Scopelliti, Farzaneh Fadaeitirani, Adrien B Depallens, Daniel Ortiz, Kay SeverinAbstract:Triple-stranded helicates were obtained by metal-templated multicomponent reactions of bispyridyloxime ligands with arylboronic acids. The helicates feature two hexa-coordinated MII ions (M=Fe, Zn, or Mn), which are embedded in a macrobicyclic ligand framework, and two arylBoronate Ester capping groups. The latter can be used to introduce functional groups such as pyridines, aldehydes, nitriles, and carboxylic acids in apical position. The functionalized helicates have the potential to be used as nanoscale building blocks for more complex assemblies, as evidenced by the synthesis of a 3 nm-sized trianglimine.
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a four component organogel based on orthogonal chemical interactions
Chemical Communications, 2014Co-Authors: Nicolas Luisier, Kurt Schenk, Kay SeverinAbstract:A thermoresponsive organogel was obtained by orthogonal assembly of four compounds using dynamic covalent Boronate Ester and imine bonds, as well as dative boron–nitrogen bonds. It is shown that the gel state can be disrupted or reinforced by chemicals which undergo exchange reactions with the gel components.
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formation of Boronate Ester polymers with efficient intrastrand charge transfer transitions by three component reactions
European Journal of Inorganic Chemistry, 2007Co-Authors: Nicolas Christinat, Rosario Scopelliti, Emmanuel Croisier, Michele Cascella, Ursula Rothlisberger, Kay SeverinAbstract:The three-component reaction of aryl boronic acids with 1,2,4,5-tetrahydroxybenzene and 1,2-bis(4-pyridyl)ethylene or 4,4-bipyridine leads to the formation of dark-purple Boronate Ester polymers. Crystallographic analyses show that the polymer strands have a zig-zag geometry, and the bis(dioxaborole) units are connected by dipyridyl linkers through dative B-N interactions. Upon dissolution of the polymers in hot chloroform, most of the B-N connections are broken, which indicates that polymer formation is a reversible process. A computational study provides evidence that the strong color of the polymers is due to efficient intrastrand charge-transfer excitations from the tetraoxobenzene to the dipyridyl linker.
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formation of Boronate Ester polymers with efficient intrastrand charge transfer transitions by three component reactions eur j inorg chem 33 2007
European Journal of Inorganic Chemistry, 2007Co-Authors: Nicolas Christinat, Rosario Scopelliti, Emmanuel Croisier, Michele Cascella, Ursula Rothlisberger, Kay SeverinAbstract:The cover picture shows the formation of deeply colored Boronate Ester polymers by three-component reactions of boronic acids with 1,2,4,5-tetrahydroxybenzene and dipyridyl compounds. The strong color of the polymers is due to efficient intrastrand charge transfer excitations from the tetraoxobenzene to the dipyridyl linker. Upon dissolution of the polymers in hot chloroform, most of the B–N connections are broken, which indicates that polymer formation is a reversible process. More details on these reactions are described in the article by K. Severin et al. on page 5177 ff.
Eric V Anslyn - One of the best experts on this subject based on the ideXlab platform.
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the mechanisms of Boronate Ester formation and fluorescent turn on in ortho aminomethylphenylboronic acids
Nature Chemistry, 2019Co-Authors: Tony D James, Byron E Collins, Pedro Metola, Xiaolong Sun, Brette M Chapin, Binghe Wang, Eric V AnslynAbstract:ortho-Aminomethylphenylboronic acids are used in receptors for carbohydrates and various other compounds containing vicinal diols. The presence of the o-aminomethyl group enhances the affinity towards diols at neutral pH, and the manner in which this group plays this role has been a topic of debate. Further, the aminomethyl group is believed to be involved in the turn-on of the emission properties of appended fluorophores upon diol binding. In this treatise, a uniform picture emerges for the role of this group: it primarily acts as an electron-withdrawing group that lowers the pKa of the neighbouring boronic acid thereby facilitating diol binding at neutral pH. The amine appears to play no role in the modulation of the fluorescence of appended fluorophores in the protic-solvent-inserted form of the boronic acid/Boronate Ester. Instead, fluorescence turn-on can be consistently tied to vibrational-coupled excited-state relaxation (a loose-bolt effect). Overall, this Review unifies and discusses the existing data as of 2019 whilst also highlighting why o-aminomethyl groups are so widely used, and the role they play in carbohydrate sensing using phenylboronic acids.
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the mechanisms of Boronate Ester formation and fluorescent turn on in ortho aminomethylphenylboronic acids
Nature Chemistry, 2019Co-Authors: Tony D James, Byron E Collins, Pedro Metola, Xiaolong Sun, Brette M Chapin, Binghe Wang, Eric V AnslynAbstract:ortho-Aminomethylphenylboronic acids are used in receptors for carbohydrates and various other compounds containing vicinal diols. The presence of the o-aminomethyl group enhances the affinity towards diols at neutral pH, and the manner in which this group plays this role has been a topic of debate. Further, the aminomethyl group is believed to be involved in the turn-on of the emission properties of appended fluorophores upon diol binding. In this treatise, a uniform picture emerges for the role of this group: it primarily acts as an electron-withdrawing group that lowers the pKa of the neighbouring boronic acid thereby facilitating diol binding at neutral pH. The amine appears to play no role in the modulation of the fluorescence of appended fluorophores in the protic-solvent-inserted form of the boronic acid/Boronate Ester. Instead, fluorescence turn-on can be consistently tied to vibrational-coupled excited-state relaxation (a loose-bolt effect). Overall, this Review unifies and discusses the existing data as of 2019 whilst also highlighting why o-aminomethyl groups are so widely used, and the role they play in carbohydrate sensing using phenylboronic acids. ortho-Aminomethylphenylboronic acids are routinely used in sensors for carbohydrates, but the function of the o-aminomethyl group in enhancing binding affinity and modulating the emission of appended fluorophores has been the matter of some debate. This Review presents a unified picture of the structural features, mechanisms of sugar complexation and photophysics of these kinds of sensors.
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boronic acid mediated coupling of catechols and n hydroxylamines a bioorthogonal reaction to label peptides
Organic Letters, 2017Co-Authors: Margaret K Meadows, Emily K Roesner, Vincent M Lynch, Tony D James, Eric V AnslynAbstract:An irreversible, three-component assembly with 2-formylphenylboronic acid, catechol, and N-hydroxylamines was achieved in aqueous media. The Boronate Ester product was formed with substituted catechols including l-DOPA. Assembly was found to be orthogonal to common biological functional groups and both copper(I)-catalyzed alkyne–azide cycloaddition and aminoether/carbonyl condensations. Boronate Ester formation and aminoether condensation were achieved in one pot with a hexameric peptide.
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Boronic Acid Mediated Coupling of Catechols and N‑Hydroxylamines: A Bioorthogonal Reaction to Label Peptides
2017Co-Authors: Margaret K. Meadows, Emily K Roesner, Tony D James, Vincent M. Lynch, Eric V AnslynAbstract:An irreversible, three-component assembly with 2-formylphenylboronic acid, catechol, and N-hydroxylamines was achieved in aqueous media. The Boronate Ester product was formed with substituted catechols including l-DOPA. Assembly was found to be orthogonal to common biological functional groups and both copper(I)-catalyzed alkyne–azide cycloaddition and aminoether/carbonyl condensations. Boronate Ester formation and aminoether condensation were achieved in one pot with a hexameric peptide
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on the rate of Boronate Ester formation in ortho aminomethyl functionalized phenyl boronic acids
Supramolecular Chemistry, 2013Co-Authors: Byron E Collins, Pedro Metola, Eric V AnslynAbstract:The role of the ortho-aminomethyl functional group in phenyl boronic acids for sugar complexation is a topic of debate. To decipher its effect on the kinetics of Boronate Ester formation, we first performed pseudo-first-order kinetics analyses at five pH values up to 4 mM in fructose, revealing a first-order kinetic dependence upon fructose. Under these conditions, the reaction is in equilibrium and does not reach completion, but at 50 mM fructose saturation is achieved, revealing zero-order dependence upon fructose. This indicates rate-determining creation of an intermediate prior to reaction with fructose, which we propose involves leaving group departure of inserted solvent. Furthermore, the region of kinetics displaying zero-order dependence has a kinetic isotope effect of 1.42, showing involvement of a proton transfer in the leaving group departure. The ratio of forward and reverse rate constants branching from the intermediate shows that fructose is several thousand times more nucleophilic than the ...
Timothy Clark - One of the best experts on this subject based on the ideXlab platform.
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selective formation of ortho aminobenzylamines by the copper catalyzed amination of benzylamine Boronate Esters
Journal of Organic Chemistry, 2015Co-Authors: Kathryn A Mcgarry, Alexi A Duenas, Timothy ClarkAbstract:The copper-catalyzed coupling between benzylamino Boronate Esters and aryl amines has been investigated. Formation of ortho-aminobenzylamines was achieved under oxidative conditions in the presence of copper(II) acetate. The major side product of the transformation is the homocoupling of the aryl Boronate Ester. The formation of the desired diamines was found to be improved in the absence of base, increasing selectivity over the homocoupled product. Both electron-donating and electron-withdrawing substituents are tolerated on both the Boronate Ester substrate and the aniline coupling partner under the reaction conditions. The presence of the adjacent benzylamine moiety appears to enhance the reactivity of the Boronate Ester and influence the resulting product distribution, likely by affecting the competing rates of transmetalation in the catalytic cycles.
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facile formation of β hydroxyBoronate Esters by a cu catalyzed diboration matteson homologation sequence
Organic Letters, 2014Co-Authors: Cameron M. Moore, Casey R. Medina, Peter C. Cannamela, Melissa L. Mcintosh, Carl J. Ferber, Andrew J. Roering, Timothy ClarkAbstract:The copper-catalyzed diboration of aldehydes was used in conjunction with the Matteson homologation, providing the efficient synthesis of β-hydroxyBoronate Esters. The oxygen-bound Boronate Ester was found to play a key role in mediating the homologation reaction, which was compared to the α-hydroxyBoronate Ester (isolated hydrolysis product). The synthetic utility of the diboration/homologation sequence was demonstrated through the oxidation of one product to provide a 1,2-diol.
Rosario Scopelliti - One of the best experts on this subject based on the ideXlab platform.
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metal stabilized Boronate Ester cages
Inorganic Chemistry, 2021Co-Authors: Erica Giraldi, Rosario Scopelliti, Farzaneh Fadaeitirani, Kay SeverinAbstract:Molecular cages with arylBoronate Ester caps at the vertices are described. The cages were obtained by metal-templated polycondensation reactions of a tris(2-formylpyridine oxime) ligand with arylboronic acids. Suited templates are triflate or triflimide salts of ZnII, FeII, CoII, or MnII. In the products, the metal ions are coordinated internally to the pyridyl and oximato N atoms adjacent to the Boronate Ester, resulting in an improved hydrolytic stability of the latter. It is possible to decorate the cages with cyano or aldehyde groups using functionalized arylboronic acids. The aldehyde groups allow for a postsynthetic modification of the cages via an imine bond formation.
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Boronate Ester capped helicates
Chemistry: A European Journal, 2020Co-Authors: Erica Giraldi, Rosario Scopelliti, Farzaneh Fadaeitirani, Adrien B Depallens, Daniel Ortiz, Kay SeverinAbstract:Triple-stranded helicates were obtained by metal-templated multicomponent reactions of bispyridyloxime ligands with arylboronic acids. The helicates feature two hexa-coordinated MII ions (M=Fe, Zn, or Mn), which are embedded in a macrobicyclic ligand framework, and two arylBoronate Ester capping groups. The latter can be used to introduce functional groups such as pyridines, aldehydes, nitriles, and carboxylic acids in apical position. The functionalized helicates have the potential to be used as nanoscale building blocks for more complex assemblies, as evidenced by the synthesis of a 3 nm-sized trianglimine.
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formation of Boronate Ester polymers with efficient intrastrand charge transfer transitions by three component reactions
European Journal of Inorganic Chemistry, 2007Co-Authors: Nicolas Christinat, Rosario Scopelliti, Emmanuel Croisier, Michele Cascella, Ursula Rothlisberger, Kay SeverinAbstract:The three-component reaction of aryl boronic acids with 1,2,4,5-tetrahydroxybenzene and 1,2-bis(4-pyridyl)ethylene or 4,4-bipyridine leads to the formation of dark-purple Boronate Ester polymers. Crystallographic analyses show that the polymer strands have a zig-zag geometry, and the bis(dioxaborole) units are connected by dipyridyl linkers through dative B-N interactions. Upon dissolution of the polymers in hot chloroform, most of the B-N connections are broken, which indicates that polymer formation is a reversible process. A computational study provides evidence that the strong color of the polymers is due to efficient intrastrand charge-transfer excitations from the tetraoxobenzene to the dipyridyl linker.
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formation of Boronate Ester polymers with efficient intrastrand charge transfer transitions by three component reactions eur j inorg chem 33 2007
European Journal of Inorganic Chemistry, 2007Co-Authors: Nicolas Christinat, Rosario Scopelliti, Emmanuel Croisier, Michele Cascella, Ursula Rothlisberger, Kay SeverinAbstract:The cover picture shows the formation of deeply colored Boronate Ester polymers by three-component reactions of boronic acids with 1,2,4,5-tetrahydroxybenzene and dipyridyl compounds. The strong color of the polymers is due to efficient intrastrand charge transfer excitations from the tetraoxobenzene to the dipyridyl linker. Upon dissolution of the polymers in hot chloroform, most of the B–N connections are broken, which indicates that polymer formation is a reversible process. More details on these reactions are described in the article by K. Severin et al. on page 5177 ff.
Nicolas Christinat - One of the best experts on this subject based on the ideXlab platform.
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formation of Boronate Ester polymers with efficient intrastrand charge transfer transitions by three component reactions
European Journal of Inorganic Chemistry, 2007Co-Authors: Nicolas Christinat, Rosario Scopelliti, Emmanuel Croisier, Michele Cascella, Ursula Rothlisberger, Kay SeverinAbstract:The three-component reaction of aryl boronic acids with 1,2,4,5-tetrahydroxybenzene and 1,2-bis(4-pyridyl)ethylene or 4,4-bipyridine leads to the formation of dark-purple Boronate Ester polymers. Crystallographic analyses show that the polymer strands have a zig-zag geometry, and the bis(dioxaborole) units are connected by dipyridyl linkers through dative B-N interactions. Upon dissolution of the polymers in hot chloroform, most of the B-N connections are broken, which indicates that polymer formation is a reversible process. A computational study provides evidence that the strong color of the polymers is due to efficient intrastrand charge-transfer excitations from the tetraoxobenzene to the dipyridyl linker.
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formation of Boronate Ester polymers with efficient intrastrand charge transfer transitions by three component reactions eur j inorg chem 33 2007
European Journal of Inorganic Chemistry, 2007Co-Authors: Nicolas Christinat, Rosario Scopelliti, Emmanuel Croisier, Michele Cascella, Ursula Rothlisberger, Kay SeverinAbstract:The cover picture shows the formation of deeply colored Boronate Ester polymers by three-component reactions of boronic acids with 1,2,4,5-tetrahydroxybenzene and dipyridyl compounds. The strong color of the polymers is due to efficient intrastrand charge transfer excitations from the tetraoxobenzene to the dipyridyl linker. Upon dissolution of the polymers in hot chloroform, most of the B–N connections are broken, which indicates that polymer formation is a reversible process. More details on these reactions are described in the article by K. Severin et al. on page 5177 ff.