The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Ying-chun Chen - One of the best experts on this subject based on the ideXlab platform.
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enantioselective h bond directed vinylogous Iminium Ion strategy for the functIonalizatIon of vinyl substituted heteroaryl aldehydes
Chemical Communications, 2021Co-Authors: Anna Skrzynska, Xin-yue Gao, Ying-chun Chen, Sebastian Frankowski, Aleksandra Topolska, Mateusz Dyguda, łukasz AlbrechtAbstract:In this work the first H-bond-directed vinylogous Iminium Ion strategy has been developed as a convenient strategy for the γ,δ-functIonalizatIon of vinyl-substituted heteroaromatic aldehydes. Their reactIon with α-mercaptoketones proceeds in a cascade manner involving 1,6-additIon followed by intramolecular aldol reactIon. Excellent stereoselectivities have been obtained as a result of the H-bond interactIons controlling the outcome of the cyclizatIon step. The applicatIon of the strategy for the synthesis of tricyclic compounds bearing furan, tetrahydrothiophene and dihydropyran moieties has also been demonstrated.
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Asymmetric Formal Vinylogous Iminium Ion ActivatIon for Vinyl-Substituted Heteroaryl and Aryl Aldehydes.
Organic letters, 2019Co-Authors: Xin-yue Gao, Ru-jie Yan, Ben-xian Xiao, Łukasz Albrecht, Ying-chun ChenAbstract:The vinyl group tethered to furfurals could be LUMO-lowered by forming formal vinylogous Iminium Ion intermediates catalyzed by a chiral secondary amine and underwent asymmetric [3 + 2] cycloadditi...
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asymmetric benzylic functIonalizatIons of 3 vinyl benzofurans via cascade formal trienamine vinylogous Iminium Ion activatIon
Organic Letters, 2017Co-Authors: Ben-xian Xiao, Xin-yue Gao, Ru-jie Yan, Ying-chun ChenAbstract:An efficient approach to construct chiral 1,1-disubstituted ethane derivatives is presented. This strategy relies on the formatIon of the key dearomatizative vinylogous Iminium Ion species through protonatIon of the formal trienamine intermediates between 2-(3-vinylbenzofuran-2-yl)ethan-1-ones and a chiral primary amine. An array of nucleophiles, including 4-hydroxycoumarins, indoles, etc., have been effectively assembled at the benzylic site, delivering the expected 1,1-disubstituted ethane products in moderate to excellent enantioselectivity.
Xin-yue Gao - One of the best experts on this subject based on the ideXlab platform.
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enantioselective h bond directed vinylogous Iminium Ion strategy for the functIonalizatIon of vinyl substituted heteroaryl aldehydes
Chemical Communications, 2021Co-Authors: Anna Skrzynska, Xin-yue Gao, Ying-chun Chen, Sebastian Frankowski, Aleksandra Topolska, Mateusz Dyguda, łukasz AlbrechtAbstract:In this work the first H-bond-directed vinylogous Iminium Ion strategy has been developed as a convenient strategy for the γ,δ-functIonalizatIon of vinyl-substituted heteroaromatic aldehydes. Their reactIon with α-mercaptoketones proceeds in a cascade manner involving 1,6-additIon followed by intramolecular aldol reactIon. Excellent stereoselectivities have been obtained as a result of the H-bond interactIons controlling the outcome of the cyclizatIon step. The applicatIon of the strategy for the synthesis of tricyclic compounds bearing furan, tetrahydrothiophene and dihydropyran moieties has also been demonstrated.
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Asymmetric Formal Vinylogous Iminium Ion ActivatIon for Vinyl-Substituted Heteroaryl and Aryl Aldehydes.
Organic letters, 2019Co-Authors: Xin-yue Gao, Ru-jie Yan, Ben-xian Xiao, Łukasz Albrecht, Ying-chun ChenAbstract:The vinyl group tethered to furfurals could be LUMO-lowered by forming formal vinylogous Iminium Ion intermediates catalyzed by a chiral secondary amine and underwent asymmetric [3 + 2] cycloadditi...
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asymmetric benzylic functIonalizatIons of 3 vinyl benzofurans via cascade formal trienamine vinylogous Iminium Ion activatIon
Organic Letters, 2017Co-Authors: Ben-xian Xiao, Xin-yue Gao, Ru-jie Yan, Ying-chun ChenAbstract:An efficient approach to construct chiral 1,1-disubstituted ethane derivatives is presented. This strategy relies on the formatIon of the key dearomatizative vinylogous Iminium Ion species through protonatIon of the formal trienamine intermediates between 2-(3-vinylbenzofuran-2-yl)ethan-1-ones and a chiral primary amine. An array of nucleophiles, including 4-hydroxycoumarins, indoles, etc., have been effectively assembled at the benzylic site, delivering the expected 1,1-disubstituted ethane products in moderate to excellent enantioselectivity.
Nicholas C. O. Tomkinson - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric Synthesis II: More Methods and ApplicatIons - Organocatalyzed transformatIons of alpha,beta-unsaturated carbonyl compounds through Iminium Ion intermediates
Asymmetric Synthesis II, 2013Co-Authors: Julian H. Rowley, Nicholas C. O. TomkinsonAbstract:Chapter 4 looks at organocatalyzed transformatIons of alpha,beta-unsaturated carbonyl compounds through Iminium Ion intermediates.
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Organocatalysed transformatIons of alpha,beta-unsaturated carbonyl compoundsthrough Iminium Ion intermediates
2012Co-Authors: Nicholas C. O. Tomkinson, Julian H. RowleyAbstract:This chapter looks at how organocatalysed transformatIons of alpha,beta-unsaturated carbonyl compounds through Iminium Ion intermediates.
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Iminium Ion catalysis: direct comparison of imidazolidinone and diarylprolinol ether reactivity
Tetrahedron Letters, 2011Co-Authors: John B. Brazier, James A. Platts, Gregory P. Hopkins, Meriem Jirari, Shaun T. Mutter, Ronan Pommereuil, Leopold Samulis, Nicholas C. O. TomkinsonAbstract:Comparison of the relative reactivities of the benchmark catalysts for Iminium Ion catalysed Diels-Alder cycloadditIon under optimised literature conditIons showed the imidazolidinone scaffold to possess significantly superior levels of activity in the Diels-Alder cycloadditIon when compared to diarylprolinol silyl ethers.
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Iminium Ion catalysis: tools and observatIons
2009Co-Authors: John B. Brazier, Jamie A. Platts, Nicholas C. O. TomkinsonAbstract:In recent years the identificatIon of new transformatIons and modes of reactIon for Iminium Ion catalysis has attracted much interest, but the majority of reports have not looked at understanding the often complex processes taking place within the reactIon flask. We have sought to understand these reactIons and to test the validity of computatIonal models. Iminium Ion catalysts can be used to accelerate a variety of cycloaddn. and conjugate addn. processes. The accepted catalytic cycles do not help in explaining important observatIons, particularly regarding reactIon medium. Through exptl. and theor. investigatIons we have focussed on three principle observatIons for the Diels-Alder cycloaddn.: - Water increases the rate of reactIons. - Water increases the e.e. of the isolated products. - Theor. models for the conformatIons of the active species do not agree. We present evidence offering insights into the crucial roles of water within these transformatIons.
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The α-effect in cyclic secondary amines: new scaffolds for Iminium Ion accelerated transformatIons
Tetrahedron, 2009Co-Authors: John B. Brazier, Ian Leigh Jones, Julie L. Cavill, Richard L. Elliott, James A. Platts, Gareth J. S. Evans, Timothy J. K. Gibbs, Nicholas C. O. TomkinsonAbstract:Five-membered secondary amine heterocycles containing an α-heteroatom were prepared and shown to be ineffective as catalysts for the Iminium Ion catalysed Diels–Alder reactIon between cinnamaldehyde and cyclopentadiene. Their six-membered counterparts proved to be highly active catalysts. In stark contrast, the catalytic activity observed when comparing the non α-heteroatom cyclic amines proline methyl ester and methyl pipecolinate showed the five-membered ring amine was significantly more active. Concurrent density functIonal theoretical calculatIons suggest a ratIonale for the observed trends in reactivity, highlighting that LUMO activatIon through an Iminium Ion intermediate plays a key role in catalytic activity.
Michinori Suginome - One of the best experts on this subject based on the ideXlab platform.
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b ome 3 as a nonacidic Iminium Ion generator in mannich and ugi type reactIons
European Journal of Organic Chemistry, 2009Co-Authors: Yusuke Tanaka, Tomoaki Hasui, Kousuke Hidaka, Michinori SuginomeAbstract:Mannich-type reactIons of aldehydes with secondary amines and a ketene silyl acetal were promoted by trimethoxyborane in DMSO to afford the corresponding β-amino esters in good yields. B(OMe)3 also promoted Ugi-type reactIons ofaldehydes with secondary amines and isocyanides in 1,2-dichloroethane, which leads to the formatIon of α-amino amides. In these reactIons, trimethoxyborane serves as an inexpensive, commercially available, and virtually nonacidic Iminium Ion generator.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
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Reductive AminatIon Of Aldehydes Using Aminoboranes As Iminium Ion Generators
Synlett, 2006Co-Authors: Michinori Suginome, Yusuke Tanaka, Tomoaki HasuiAbstract:2-Dialkylamino-4H-1,3,2-benzodioxaborins, salicyl alcohol derived aminoboranes, serve as efficient and mild Iminium Ion generators in the reductive aminatIon of aldehydes with NaBH 4 . Using a diisopropylamino derivative, a variety of amines including secondary and primary amines, and ammonia can participate to the reductive aminatIon in aprotic organic solvents without the use of acidic promoters.
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Aminoboranes as new Iminium Ion generators in aminatIon reactIons
Pure and Applied Chemistry, 2006Co-Authors: Michinori SuginomeAbstract:The utilizatIon of aminoborane derivatives in aminatIon reactIons such as Strecker- type aminative cyanatIon, Mannich-type reactIon, and reductive aminatIon is described. Bis(dialkylamino)cyanoboranes and bis(dialkylamino)boron enolates underwent the concur- rent transfer of the amino group and either the cyano or the enoxy group from the boron to carbonyl carbon atom in their reactIon with aldehydes, leading to the formatIon of α-amino nitriles and β-amino ketones, respectively. Bis(dialkylamino)borane derivatives that lack the additIonal nucleophilic groups on the boron atoms were found to serve as effective genera- tors of Iminium Ions from aldehydes. In the presence of these aminoboranes, reactIons of aldehydes with ketene silyl acetals or silyl enol ethers take place, giving Mannich-type prod- ucts, i.e., β-amino esters and ketones, selectively. Using diisopropylamino-substituted boron compounds, which are designed as "universal" Iminium Ion generators, reactIons of free sec-amines, aldehydes, and ketene silyl acetals proceed efficiently, giving β-amino esters in which the amino groups are derived exclusively from the free amines. The use of the univer- sal Iminium Ion generator is also effective for reductive aminatIon of aldehydes, in which NaBH 4 is used as a hydride donor.
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Aminoboranes as “Compatible” Iminium Ion Generators in Aminative C−C Bond FormatIons
Journal of the American Chemical Society, 2004Co-Authors: Michinori Suginome, Lars Uehlin, Masahiro MurakamiAbstract:Aminoboranes have been shown to be highly efficient and mild Iminium Ion generators in the Mannich-type aminative coupling of aldehydes with silyl ketene acetals. By using aminoboranes bearing bulky amino groups, such as a diisopropylamino group, free secondary amines can be successfully used as the amino component in a three-component Mannich reactIon with aldehydes and silyl ketene acetals.
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aminoboranes as compatible Iminium Ion generators in aminative c c bond formatIons
Journal of the American Chemical Society, 2004Co-Authors: Michinori Suginome, Lars Uehlin, Masahiro MurakamiAbstract:Aminoboranes have been shown to be highly efficient and mild Iminium Ion generators in the Mannich-type aminative coupling of aldehydes with silyl ketene acetals. By using aminoboranes bearing bulky amino groups, such as a diisopropylamino group, free secondary amines can be successfully used as the amino component in a three-component Mannich reactIon with aldehydes and silyl ketene acetals.
Le Zhen - One of the best experts on this subject based on the ideXlab platform.
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Iminium Ion and n hydroxyimide as the surrogate components in dead promoted oxidative ugi variant
Journal of Organic Chemistry, 2018Co-Authors: Jiankun Wang, Yilin Sun, Muhan Jiang, Yongjie Zhao, Guangji Wang, Kun Hao, Le ZhenAbstract:A practical metal-free oxidative Ugi-type three-component assembly has been achieved efficiently, employing a tertiary-amine-derived Iminium Ion as an imine surrogate, N-hydroxyimide as an acid surrogate, and DEAD as an oxidant. This dual-surrogate Ugi variant proceeded with a broad substrate scope and desired functIonal group tolerance, leading to a wide range of N-alkyl- N-acyl aminophthalimide and N-alkyl- N-acylaminosuccinimide derivatives in good isolated yields.
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Iminium Ion and N‑Hydroxyimide as the Surrogate Components in DEAD-Promoted Oxidative Ugi Variant
2018Co-Authors: Jiankun Wang, Yilin Sun, Muhan Jiang, Yongjie Zhao, Guangji Wang, Kun Hao, Le ZhenAbstract:A practical metal-free oxidative Ugi-type three-component assembly has been achieved efficiently, employing a tertiary-amine-derived Iminium Ion as an imine surrogate, N-hydroxyimide as an acid surrogate, and DEAD as an oxidant. This dual-surrogate Ugi variant proceeded with a broad substrate scope and desired functIonal group tolerance, leading to a wide range of N-alkyl-N-acyl aminophthalimide and N-alkyl-N-acylaminosuccinimide derivatives in good isolated yields
