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Philip Bulman C Page - One of the best experts on this subject based on the ideXlab platform.
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asymmetric oxidation of enol derivatives to α alkoxy carbonyls using Iminium Salt catalysts a synthetic and computational study
Journal of Organic Chemistry, 2019Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, Saud M Almutairi, Richard G Stephenson, Yannick Gama, Ross L Goodyear, Alice Douteau, Garth A JonesAbstract:We report herein the first examples of asymmetric oxidation of enol ether and ester substrates using Iminium Salt organocatalysis, affording moderate to excellent enantioselectivities of up to 98% ee for tetralone-derived substrates in the α-hydroxyketone products. A comprehensive density functional theory study was undertaken to interpret the competing diastereoisomeric transition states in this example in order to identify the origins of enantioselectivity. The calculations, performed at the B3LYP/6-31G(D) level of theory, gave good agreement with the experimental results, in terms of the magnitude of the effects under the specified reaction conditions, and in terms of the preferential formation of the ( R)-enantiomer. Just one of the 30 characterized transition states dominates the enantioselectivity, which is attributed to the adoption of an orientation relative to stereochemical features of the chiral controlling element that combines a CH-π interaction between a CH2 group in the substrate and one of the aromatic rings of the biaryl section of the chiral auxiliary with a good alignment of the acetoxy group with the other biaryl ring, and places the smallest substituent on the alkene (a hydrogen atom) in the most sterically hindered position.
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Asymmetric Oxidation of Enol Derivatives to α‑Alkoxy Carbonyls Using Iminium Salt Catalysts: A Synthetic and Computational Study
2018Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, Saud M Almutairi, Richard G Stephenson, Yannick Gama, Ross L Goodyear, Alice Douteau, Garth A JonesAbstract:We report herein the first examples of asymmetric oxidation of enol ether and ester substrates using Iminium Salt organocatalysis, affording moderate to excellent enantioselectivities of up to 98% ee for tetralone-derived substrates in the α-hydroxyketone products. A comprehensive density functional theory study was undertaken to interpret the competing diastereoisomeric transition states in this example in order to identify the origins of enantioselectivity. The calculations, performed at the B3LYP/6-31G(D) level of theory, gave good agreement with the experimental results, in terms of the magnitude of the effects under the specified reaction conditions, and in terms of the preferential formation of the (R)-enantiomer. Just one of the 30 characterized transition states dominates the enantioselectivity, which is attributed to the adoption of an orientation relative to stereochemical features of the chiral controlling element that combines a CH−π interaction between a CH2 group in the substrate and one of the aromatic rings of the biaryl section of the chiral auxiliary with a good alignment of the acetoxy group with the other biaryl ring, and places the smallest substituent on the alkene (a hydrogen atom) in the most sterically hindered position
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new biphenyl Iminium Salt catalysts for highly enantioselective asymmetric epoxidation role of additional substitution and dihedral angle
Organic and Biomolecular Chemistry, 2016Co-Authors: Philip Bulman C Page, Christopher J Bartlett, Yohan Chan, Steven M Allin, Michael J Mckenzie, Jerome Lacour, Garth A JonesAbstract:New biaryl Iminium Salt catalysts for enantioselective alkene epoxidation containing additional substitution in the heterocyclic ring are reported. The effects upon conformation and enantioselectivity of this additional substitution, and the influence of dihedral angle in these systems, has been investigated using a synthetic approach supported by density functional theory. Enantioselectivities of up to 97% ee were observed.
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enantioselective epoxidation of dihydroquinolines by using Iminium Salt organocatalysts
ChemInform, 2015Co-Authors: Philip Bulman C Page, David P Day, Yohan ChanAbstract:The epoxidation of dihydroquinolines (I) in the presence of optically active Iminium Salt catalyst gives epoxides with low to moderate enantioselectivities.
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carbohydrate derived Iminium Salt organocatalysts for the asymmetric epoxidation of alkenes
ChemInform, 2015Co-Authors: Philip Bulman C Page, Yohan Chan, John Liddle, Mark R J ElsegoodAbstract:A new family of carbohydrate-based dihydroisoquinolinium Salts has been prepared and tested for potential as asymmetric catalysts for the epoxidation of unfunctionalized alkene substrates, providing up to 57% ee in the product epoxides.
Benjamin R Buckley - One of the best experts on this subject based on the ideXlab platform.
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Kinetic Resolution in Asymmetric Epoxidation using Iminium Salt Catalysis
2015Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Alexandra M Z Slawin, Louise F. Appleby, Michael J MckenzieAbstract:The first reported examples of kinetic resolution in epoxidation reactions using Iminium Salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes
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kinetic resolution in asymmetric epoxidation using Iminium Salt catalysis
Journal of Organic Chemistry, 2013Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Louise F Appleby, Alexandra M Z Slawin, Michael J MckenzieAbstract:The first reported examples of kinetic resolution in epoxidation reactions using Iminium Salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes.
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asymmetric epoxidation using Iminium Salt organocatalysts featuring dynamically controlled atropoisomerism
Journal of Organic Chemistry, 2012Co-Authors: Philip Bulman C Page, Christopher J Bartlett, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Alexandra M Z Slawin, Phillip Parker, Geracimos Rassias, Jerome LacourAbstract:Introduction of a pseudoaxial substituent at a stereogenic center adjacent to the nitrogen atom in binaphthyl- and biphenyl-derived azepinium Salt organocatalysts affords improved enantioselectivities and yields in the epoxidation of unfunctionalized alkenes. In the biphenyl-derived catalysts, the atropoisomerism at the biphenyl axis is controlled by the interaction of this substituent with the chiral substituent at nitrogen.
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binaphthalene derived Iminium Salt catalysts for highly enantioselective asymmetric epoxidation
ChemInform, 2009Co-Authors: Philip Bulman C Page, Benjamin R Buckley, Mohamed M Farah, John A BlackerAbstract:Enantiomerically enriched epoxides are useful intermediates that have found many applications in asymmetric synthesis, and development of efficient catalysts for asymmetric epoxidation has received considerable attention. In this manuscript we describe the design, preparation, and use of new highly selective Iminium Salt organocatalysts for asymmetric epoxidation, based around a chiral binaphthalene motif coupled with a chiral substituted dioxane moiety. The new catalysts have been tested in the catalytic asymmetric epoxidation of unfunctionalized alkenes, and provide up to 95 % ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
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Iminium Salt catalysed asymmetric epoxidation using hydrogen peroxide as stoichiometric oxidant
Advanced Synthesis & Catalysis, 2008Co-Authors: Philip Bulman C Page, Benjamin R Buckley, Phillip Parker, Gerasimos A Rassias, Donald BethellAbstract:Iminium Salt organocatalysts can provide high selectivity and high efficiency in catalytic asymmetric epoxidation. They are normally used in conjunction with Oxone as the stoichiometric oxidant. Oxone, however, has limited stability and is insoluble in most organic solvents; we report here for the first time the development of a reaction system driven by hydrogen peroxide as the stoichiometric oxidant, involving an unusual double catalytic cycle.
Yohan Chan - One of the best experts on this subject based on the ideXlab platform.
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asymmetric oxidation of enol derivatives to α alkoxy carbonyls using Iminium Salt catalysts a synthetic and computational study
Journal of Organic Chemistry, 2019Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, Saud M Almutairi, Richard G Stephenson, Yannick Gama, Ross L Goodyear, Alice Douteau, Garth A JonesAbstract:We report herein the first examples of asymmetric oxidation of enol ether and ester substrates using Iminium Salt organocatalysis, affording moderate to excellent enantioselectivities of up to 98% ee for tetralone-derived substrates in the α-hydroxyketone products. A comprehensive density functional theory study was undertaken to interpret the competing diastereoisomeric transition states in this example in order to identify the origins of enantioselectivity. The calculations, performed at the B3LYP/6-31G(D) level of theory, gave good agreement with the experimental results, in terms of the magnitude of the effects under the specified reaction conditions, and in terms of the preferential formation of the ( R)-enantiomer. Just one of the 30 characterized transition states dominates the enantioselectivity, which is attributed to the adoption of an orientation relative to stereochemical features of the chiral controlling element that combines a CH-π interaction between a CH2 group in the substrate and one of the aromatic rings of the biaryl section of the chiral auxiliary with a good alignment of the acetoxy group with the other biaryl ring, and places the smallest substituent on the alkene (a hydrogen atom) in the most sterically hindered position.
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Asymmetric Oxidation of Enol Derivatives to α‑Alkoxy Carbonyls Using Iminium Salt Catalysts: A Synthetic and Computational Study
2018Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, Saud M Almutairi, Richard G Stephenson, Yannick Gama, Ross L Goodyear, Alice Douteau, Garth A JonesAbstract:We report herein the first examples of asymmetric oxidation of enol ether and ester substrates using Iminium Salt organocatalysis, affording moderate to excellent enantioselectivities of up to 98% ee for tetralone-derived substrates in the α-hydroxyketone products. A comprehensive density functional theory study was undertaken to interpret the competing diastereoisomeric transition states in this example in order to identify the origins of enantioselectivity. The calculations, performed at the B3LYP/6-31G(D) level of theory, gave good agreement with the experimental results, in terms of the magnitude of the effects under the specified reaction conditions, and in terms of the preferential formation of the (R)-enantiomer. Just one of the 30 characterized transition states dominates the enantioselectivity, which is attributed to the adoption of an orientation relative to stereochemical features of the chiral controlling element that combines a CH−π interaction between a CH2 group in the substrate and one of the aromatic rings of the biaryl section of the chiral auxiliary with a good alignment of the acetoxy group with the other biaryl ring, and places the smallest substituent on the alkene (a hydrogen atom) in the most sterically hindered position
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new biphenyl Iminium Salt catalysts for highly enantioselective asymmetric epoxidation role of additional substitution and dihedral angle
Organic and Biomolecular Chemistry, 2016Co-Authors: Philip Bulman C Page, Christopher J Bartlett, Yohan Chan, Steven M Allin, Michael J Mckenzie, Jerome Lacour, Garth A JonesAbstract:New biaryl Iminium Salt catalysts for enantioselective alkene epoxidation containing additional substitution in the heterocyclic ring are reported. The effects upon conformation and enantioselectivity of this additional substitution, and the influence of dihedral angle in these systems, has been investigated using a synthetic approach supported by density functional theory. Enantioselectivities of up to 97% ee were observed.
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enantioselective epoxidation of dihydroquinolines by using Iminium Salt organocatalysts
ChemInform, 2015Co-Authors: Philip Bulman C Page, David P Day, Yohan ChanAbstract:The epoxidation of dihydroquinolines (I) in the presence of optically active Iminium Salt catalyst gives epoxides with low to moderate enantioselectivities.
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carbohydrate derived Iminium Salt organocatalysts for the asymmetric epoxidation of alkenes
ChemInform, 2015Co-Authors: Philip Bulman C Page, Yohan Chan, John Liddle, Mark R J ElsegoodAbstract:A new family of carbohydrate-based dihydroisoquinolinium Salts has been prepared and tested for potential as asymmetric catalysts for the epoxidation of unfunctionalized alkene substrates, providing up to 57% ee in the product epoxides.
David P Day - One of the best experts on this subject based on the ideXlab platform.
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recent advances in Iminium Salt catalysed asymmetric epoxidation
European Journal of Organic Chemistry, 2017Co-Authors: David P Day, Philip B SellarsAbstract:The research in this thesis depicts some of the most current developments in the area of asymmetric epoxidation of alkenes using chiral Iminium Salt catalysts. The first chapter reviews past and present developments in; catalytic asymmetric epoxidation, and covers the application of this reaction towards the kinetic resolution of racemic olefins. Chapter two is separated into two key areas; (i) asymmetric epoxidation as a tool in the kinetic resolution of racemic chromene substrates, and (ii) investigations into the asymmetric epoxidation of new N-protected dihydroquinoline substrates. In the first part of chapter two, the first examples of kinetic resolution in epoxidation reactions using Iminium Salt catalysts are reported, providing up to 98% ee in the epoxidation of racemic cis-chromenes. The second part of chapter two details the first known examples of asymmetric epoxidation upon nitrogen-protected dihydroquinoline substrates, affording enantioselectivities as high as 73% ee. In both parts of chapter two, non-aqueous epoxidation conditions were employed using Page’s dihydroisoquinolinium Iminium Salt catalyst. The later part of chapter two introduces a biphenylazepinium Iminium Salt catalyst used under aqueous epoxidation conditions. Chapter three includes experimental data for all the compounds mentioned in chapter two, with chapter four containing HPLC traces to show determination of enantiomeric excess of epoxides, and enantioenriched alkene traces.
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enantioselective epoxidation of dihydroquinolines by using Iminium Salt organocatalysts
ChemInform, 2015Co-Authors: Philip Bulman C Page, David P Day, Yohan ChanAbstract:The epoxidation of dihydroquinolines (I) in the presence of optically active Iminium Salt catalyst gives epoxides with low to moderate enantioselectivities.
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Kinetic Resolution in Asymmetric Epoxidation using Iminium Salt Catalysis
2015Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Alexandra M Z Slawin, Louise F. Appleby, Michael J MckenzieAbstract:The first reported examples of kinetic resolution in epoxidation reactions using Iminium Salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes
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enantioselective epoxidation of dihydroquinolines by using Iminium Salt organocatalysts
European Journal of Organic Chemistry, 2014Co-Authors: Philip Bulman C Page, David P Day, Yohan ChanAbstract:The first examples of asymmetric epoxidation of dihydroquinoline substrates using Iminium Salt organocatalysts are reported. The 3,4-epoxytetrahydroquinoline products are obtained in good yields and with moderate to good enantioselectivities.
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kinetic resolution in asymmetric epoxidation using Iminium Salt catalysis
Journal of Organic Chemistry, 2013Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Louise F Appleby, Alexandra M Z Slawin, Michael J MckenzieAbstract:The first reported examples of kinetic resolution in epoxidation reactions using Iminium Salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes.
Alexandra M Z Slawin - One of the best experts on this subject based on the ideXlab platform.
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Kinetic Resolution in Asymmetric Epoxidation using Iminium Salt Catalysis
2015Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Alexandra M Z Slawin, Louise F. Appleby, Michael J MckenzieAbstract:The first reported examples of kinetic resolution in epoxidation reactions using Iminium Salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes
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kinetic resolution in asymmetric epoxidation using Iminium Salt catalysis
Journal of Organic Chemistry, 2013Co-Authors: Philip Bulman C Page, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Louise F Appleby, Alexandra M Z Slawin, Michael J MckenzieAbstract:The first reported examples of kinetic resolution in epoxidation reactions using Iminium Salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes.
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asymmetric epoxidation using Iminium Salt organocatalysts featuring dynamically controlled atropoisomerism
Journal of Organic Chemistry, 2012Co-Authors: Philip Bulman C Page, Christopher J Bartlett, Yohan Chan, Steven M Allin, David P Day, Benjamin R Buckley, Alexandra M Z Slawin, Phillip Parker, Geracimos Rassias, Jerome LacourAbstract:Introduction of a pseudoaxial substituent at a stereogenic center adjacent to the nitrogen atom in binaphthyl- and biphenyl-derived azepinium Salt organocatalysts affords improved enantioselectivities and yields in the epoxidation of unfunctionalized alkenes. In the biphenyl-derived catalysts, the atropoisomerism at the biphenyl axis is controlled by the interaction of this substituent with the chiral substituent at nitrogen.
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functionalized Iminium Salt systems for catalytic asymmetric epoxidation
Journal of Organic Chemistry, 2001Co-Authors: Philip Bulman C Page, Benjamin R Buckley, Gerasimos A Rassias, Donald Bethell, David Barros, Adel Ardakani, And Timothy A D Smith, Alexandra M Z SlawinAbstract:A range of dihydroisoquinolinium Salts containing alcohol, ether, and acetal functionalities in the nitrogen substituent has been prepared and tested as asymmetric epoxidation catalysts, providing ee's of up to ca. 60%.
