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Jean-marie Lehn - One of the best experts on this subject based on the ideXlab platform.
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Imine as unidirectional photodriven mol motor dynamic device
Chem. Eur. J., 2006Co-Authors: Jean-marie LehnAbstract:Compounds containing the CN group, such as Imines and derivatives, may undergo syn-anti isomerization by two different routes: 1) photochemically, by out-of-plane rotation around the carbon-nitrogen double bond through a perpendicular form, and 2) thermally, by in-plane nitrogen inversion through a linear transition state. When the two interconversions occur in sequence, a full, closed process is accomplished, restoring the initial state of the system along two different steps. In a chiral Imine-type compound, for example, with an asymmetric center next to the CN function, photoinduced rotation may be expected to occur in one sense in preference to the opposite one. Thus, photoisomerization followed by thermal isomerization in a chiral Imine compound generates unidirectional molecular motion. Generally, Imine-type compounds represent unidirectional molecular photomotors converting light energy into mechanical motion. As they are also able to undergo exchange of the carbonyl and amine partners, they present constitutional dynamics. Thus, Imine-type compounds are double dynamic, motional, and constitutional devices.
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Conjecture: Imines as unidirectional photodriven molecular motors-motional and constitutional dynamic devices
Chemistry - A European Journal, 2006Co-Authors: Jean-marie LehnAbstract:Compounds containing the C==N group, such as Imines and their derivatives, may undergo syn-anti isomerization by two different routes: 1) photochemically, by out-of-plane rotation around the carbon-nitrogen double bond through a "perpendicular" form, and 2) thermally, by in-plane nitrogen inversion through a "linear" transition state. When the two interconversions occur in sequence, a full, closed process is accomplished, restoring the initial state of the system along two different steps. In a chiral Imine-type compound, for example, with an asymmetric center next to the C==N function, photoinduced rotation may be expected to occur in one sense in preference to the opposite one. Thus, photoisomerization followed by thermal isomerization in a chiral Imine compound generates unidirectional molecular motion. Generally, Imine-type compounds represent unidirectional molecular photomotors converting light energy into mechanical motion. As they are also able to undergo exchange of the carbonyl and amine partners, they present constitutional dynamics. Thus, Imine-type compounds are double dynamic, motional, and constitutional devices.
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scandium iii catalysis of transimination reactions independent and constitutionally coupled reversible processes
Journal of the American Chemical Society, 2005Co-Authors: Nicolas Giuseppone, Jeanlouis Schmitt, Evan Schwartz, Jean-marie LehnAbstract:Sc(OTf)3 efficiently catalyzes the self-sufficient transimination reaction between various types of CN bonds in organic solvents, with turnover frequencies up to 3600 h-1 and rate accelerations up to 6 × 105. The mechanism of the crossover reaction in mixtures of amines and Imines is studied, comparing parallel individual reactions with coupled equilibria. The intrinsic kinetic parameters for isolated reactions cannot simply be added up when several components are mixed, and the behavior of the system agrees with the presence of a unique mediator that constitutes the core of a network of competing reactions. In mixed systems, every single amine or Imine competes for the same central hub, in accordance with their binding affinity for the catalyst metal ion center. More generally, the study extends the basic principles of constitutional dynamic chemistry to interconnected chemical transformations and provides a step toward dynamic systems of increasing complexity.
Jiaxi Xu - One of the best experts on this subject based on the ideXlab platform.
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do reaction conditions affect the stereoselectivity in the staudinger reaction
Journal of Organic Chemistry, 2006Co-Authors: Yikai Wang, Daming Du, Lei Jiao, Yong Liang, Jiaxi XuAbstract:The stereochemistry is one of the critical issues in the Staudinger reaction. We have proposed the origin of the stereoselectivity recently. The effects of solvents, additives, and pathways of ketene generation on the stereoselectivity were investigated by using a clean Staudinger reaction, which is a sensitive reaction system to the stereoselectivity. The results indicate that the additives, usually existed and generated in the Staudinger reaction, and the pathways of the ketene generation do not generally affect the stereoselectivity. The solvent affects the stereoselectivity. The polar solvent is favorable to the formation of trans-β-lactams. The addition orders of the reagents affect the stereoselectivity in the Staudinger reaction between acyl chlorides and Imines. The addition of a tertiary amine into a solution of the acyl chloride and the Imine generally decreases the stereoselectivity, which is affected by the interval between additions of the acyl chloride and the tertiary amine, and the Imine s...
Yikai Wang - One of the best experts on this subject based on the ideXlab platform.
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do reaction conditions affect the stereoselectivity in the staudinger reaction
Journal of Organic Chemistry, 2006Co-Authors: Yikai Wang, Daming Du, Lei Jiao, Yong Liang, Jiaxi XuAbstract:The stereochemistry is one of the critical issues in the Staudinger reaction. We have proposed the origin of the stereoselectivity recently. The effects of solvents, additives, and pathways of ketene generation on the stereoselectivity were investigated by using a clean Staudinger reaction, which is a sensitive reaction system to the stereoselectivity. The results indicate that the additives, usually existed and generated in the Staudinger reaction, and the pathways of the ketene generation do not generally affect the stereoselectivity. The solvent affects the stereoselectivity. The polar solvent is favorable to the formation of trans-β-lactams. The addition orders of the reagents affect the stereoselectivity in the Staudinger reaction between acyl chlorides and Imines. The addition of a tertiary amine into a solution of the acyl chloride and the Imine generally decreases the stereoselectivity, which is affected by the interval between additions of the acyl chloride and the tertiary amine, and the Imine s...
Armido Studer - One of the best experts on this subject based on the ideXlab platform.
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Radical Amination with Trimethylstannylated Benzophenone Imine.
ChemInform, 2010Co-Authors: Marie‐celine Lamas, Santiago E. Vaillard, Birgit Wibbeling, Armido StuderAbstract:Amination reaction of a variety of primary, secondary and tertiary alkyl radicals using the title Imine (II) and tBuOOtBu as an initiator affords the Imines in good yields, but in many cases they decompose on purification.
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Radical Amination with Trimethylstannylated Benzophenone Imine
Organic Letters, 2010Co-Authors: Marie‐celine Lamas, Santiago E. Vaillard, Birgit Wibbeling, Armido StuderAbstract:Intermolecular radical amination reactions of various primary, secondary, and tertiary alkyl radicals by using trimethylstannylated benzophenone Imine A as a novel radical acceptor to provide Imines of type B are described. These Imines are readily reduced with NaBH4 to the corresponding secondary amines C. The novel radical amination can be combined with typical radical cyclization reactions.
Robert H Morris - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and use of an asymmetric transfer hydrogenation catalyst based on iron(II) for the synthesis of enantioenriched alcohols and amines
Nature Protocols, 2015Co-Authors: Robert H MorrisAbstract:The catalytic hydrogenation of prochiral ketones and Imines is an advantageous approach to the synthesis of enantioenriched alcohols and amines, respectively, which are two classes of compounds that are highly prized in pharmaceutical, fragrance and flavoring chemistry. This hydrogenation reaction is generally carried out using ruthenium-based catalysts. Our group has developed an alternative synthetic route that is based on the environmentally friendlier iron-based catalysis. This protocol describes the three-part synthesis of trans -[amine(Imine)diphosphine]chlorocarbonyliron(II) tetrafluoroborate templated by iron salts and starting from commercially available chemicals, which provides the precatalyst for the efficient asymmetric transfer hydrogenation of ketones and Imines. The use of the enantiopure ( S , S ) catalyst to reduce prochiral ketones to the ( R )-alcohol in good to excellent yields and enantioenrichment is also detailed, as well as the reduction to the amine in very high yield and enantiopurity of Imines substituted at the nitrogen with the N -(diphenylphosphinoyl) group (-P(O)Ph_2). Although the best ruthenium catalysts provide alcohols in higher enantiomeric excess (ee) than the iron complex catalyst used in this protocol, they do so on much longer time scales or at higher catalyst loadings. This protocol can be completed in 2 weeks. Zuo and Morris describe an approach to catalytic hydrogenation of prochiral ketones and Imines to produce enantioenriched alcohols and amines that uses a more environmentally friendly iron-based catalyst instead of conventional Ru-based catalysts.
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amine Imine diphosphine iron catalysts for asymmetric transfer hydrogenation of ketones and Imines
ChemInform, 2014Co-Authors: Alan J Lough, Young Feng Li, Robert H MorrisAbstract:The synthesis of novel enantiopure amine(Imine)diphosphine catalysts that take advantage of the iron(II) ion as a template is described.
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amine Imine diphosphine iron catalysts for asymmetric transfer hydrogenation of ketones and Imines
Science, 2013Co-Authors: Alan J Lough, Young Feng Li, Robert H MorrisAbstract:A rational approach is needed to design hydrogenation catalysts that make use of Earth-abundant elements to replace the rare elements such as ruthenium, rhodium, and palladium that are traditionally used. Here, we validate a prior mechanistic hypothesis that partially saturated amine(Imine)diphosphine ligands (P-NH-N-P) activate iron to catalyze the asymmetric reduction of the polar bonds of ketones and Imines to valuable enantiopure alcohols and amines, with isopropanol as the hydrogen donor, at turnover frequencies as high as 200 per second at 28°C. We present a direct synthetic approach to enantiopure ligands of this type that takes advantage of the iron(lI) ion as a template. The catalytic mechanism is elucidated by the spectroscopic detection of iron hydride and amide intermediates.
