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Tilby MJ, Dewez DF, Hall A, Martínez Lamenca C, Willis MC. Exploiting Configurational Lability in Aza‐Sulfur Compounds for the Organocatalytic Enantioselective Synthesis of Sulfonimidamides. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202109160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Michael J. Tilby
- Department of Chemistry University of Oxford Chemistry Research Laboratory Mansfield Road Oxford OX1 3TA UK
| | - Damien F. Dewez
- Department of Chemistry University of Oxford Chemistry Research Laboratory Mansfield Road Oxford OX1 3TA UK
| | | | | | - Michael C. Willis
- Department of Chemistry University of Oxford Chemistry Research Laboratory Mansfield Road Oxford OX1 3TA UK
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2
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Tilby MJ, Dewez DF, Hall A, Martínez Lamenca C, Willis MC. Exploiting Configurational Lability in Aza-Sulfur Compounds for the Organocatalytic Enantioselective Synthesis of Sulfonimidamides. Angew Chem Int Ed Engl 2021; 60:25680-25687. [PMID: 34558788 PMCID: PMC9298307 DOI: 10.1002/anie.202109160] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 09/20/2021] [Indexed: 11/19/2022]
Abstract
Methods for establishing the absolute configuration of sulfur‐stereogenic aza‐sulfur derivatives are scarce, often relying on cumbersome protocols and a limited pool of enantioenriched starting materials. We have addressed this by exploiting, for the first time, a feature of sulfonimidamides in which it is possible for tautomeric structures to also be enantiomeric. Such sulfonimidamides can readily generate prochiral ions, which we have exploited in an enantioselective alkylation process. Selectivity is achieved using a readily prepared bis‐quaternized phase‐transfer catalyst. The overall process establishes the capability of configurationally labile aza‐sulfur species to be used in asymmetric catalysis.
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Affiliation(s)
- Michael J Tilby
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA, UK
| | - Damien F Dewez
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA, UK
| | - Adrian Hall
- UCB Biopharma, 1420, Braine-l'Alleud, Belgium
| | | | - Michael C Willis
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford, OX1 3TA, UK
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3
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Hayama N. [Asymmetric Hetero-Michael Additions to α,β-Unsaturated Carboxylic Acids by Multifunctional Boronic Acid Catalysts]. YAKUGAKU ZASSHI 2021; 141:293-301. [PMID: 33642494 DOI: 10.1248/yakushi.20-00214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Several direct asymmetric Michael additions to α,β-unsaturated carboxylic acids with integrated catalysts comprising chiral bifunctional thiourea and arylboronic acid were developed. First, the asymmetric aza-Michael addition of hydroxylamine derivatives efficiently afforded a variety of optically active β-amino acid derivatives. Furthermore, upon detailed investigation of the reaction, tetrahedral borate complexes, comprising two carboxylate molecules, were found to serve as reaction intermediates. Based on this observation, a drastic improvement in product enantioselectivity was achieved upon benzoic acid addition. Second, on merely changing the solvent, the asymmetric thia-Michael addition of arylthiols afforded both enantiomers of the adducts, which are important building blocks for biologically active compounds.
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Affiliation(s)
- Noboru Hayama
- School of Pharmaceutical Sciences, Mukogawa Women's University
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4
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Hayama N, Kobayashi Y, Takemoto Y. Asymmetric hetero-Michael addition to α,β-unsaturated carboxylic acids using thiourea–boronic acid hybrid catalysts. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132089] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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5
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Tang QG, Cai SL, Wang CC, Lin GQ, Sun XW. Organocatalytic Aza-Michael/Michael Cyclization Cascade Reaction: Enantioselective Synthesis of Spiro-oxindole Piperidin-2-one Derivatives. Org Lett 2020; 22:3351-3355. [PMID: 32281799 DOI: 10.1021/acs.orglett.0c00779] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A simple, direct, and highly enantioselective synthesis of spiro-oxindole piperidin-2-one derivatives was achieved through an aza-Michael/Michael cyclization cascade sequence using a squaramide catalyst. The desired products were obtained in excellent yields (up to 99%) and good to high stereoselectivities (up to >20:1 dr and up to 99% ee) under mild conditions.
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Affiliation(s)
- Qing-Gang Tang
- Department of Chemistry, Fudan University, Shanghai 200433, China
| | - Sen-Lin Cai
- Department of Chemistry, Fudan University, Shanghai 200433, China
| | - Chuan-Chuan Wang
- Department of Chemistry, Fudan University, Shanghai 200433, China
| | - Guo-Qiang Lin
- Department of Chemistry, Fudan University, Shanghai 200433, China.,CAS Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
| | - Xing-Wen Sun
- Department of Chemistry, Fudan University, Shanghai 200433, China
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6
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Lin Y, Hirschi WJ, Kunadia A, Paul A, Ghiviriga I, Abboud KA, Karugu RW, Vetticatt MJ, Hirschi JS, Seidel D. A Selenourea-Thiourea Brønsted Acid Catalyst Facilitates Asymmetric Conjugate Additions of Amines to α,β-Unsaturated Esters. J Am Chem Soc 2020; 142:5627-5635. [PMID: 32118419 PMCID: PMC7533150 DOI: 10.1021/jacs.9b12457] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
β-Amino esters are obtained with high levels of enantioselectivity via the conjugate addition of cyclic amines to unactivated α,β-unsaturated esters. A related strategy enables the kinetic resolution of racemic cyclic 2-arylamines, using benzyl acrylate as the resolving agent. Reactions are facilitated by an unprecedented selenourea-thiourea organocatalyst. As elucidated by DFT calculations and 13C kinetic isotope effect studies, the rate-limiting and enantiodetermining step of the reaction is the protonation of a zwitterionic intermediate by the catalyst. This represents a rare case in which a thiourea compound functions as an asymmetric Brønsted acid catalyst.
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Affiliation(s)
- Yingfu Lin
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - William J Hirschi
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Anuj Kunadia
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Anirudra Paul
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Ion Ghiviriga
- Center for NMR Spectroscopy, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Khalil A Abboud
- Center for X-ray Crystallography, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Rachael W Karugu
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Mathew J Vetticatt
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Jennifer S Hirschi
- Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States
| | - Daniel Seidel
- Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
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7
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Michigami K, Murakami H, Nakamura T, Hayama N, Takemoto Y. Catalytic asymmetric aza-Michael addition of fumaric monoacids with multifunctional thiourea/boronic acids. Org Biomol Chem 2019; 17:2331-2335. [DOI: 10.1039/c9ob00045c] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Chiral multifunctional thiourea/boronic acid catalysts enabled the synthesis of N-hydroxyaspartate derivatives applicable for KAHA amidation through acid-β selective aza-Michael addition.
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Affiliation(s)
- Kenichi Michigami
- Graduate School of Pharmaceutical Sciences
- Kyoto University
- Kyoto 606-8501
- Japan
| | - Hiroki Murakami
- Graduate School of Pharmaceutical Sciences
- Kyoto University
- Kyoto 606-8501
- Japan
| | - Takeru Nakamura
- Graduate School of Pharmaceutical Sciences
- Kyoto University
- Kyoto 606-8501
- Japan
| | - Noboru Hayama
- Graduate School of Pharmaceutical Sciences
- Kyoto University
- Kyoto 606-8501
- Japan
| | - Yoshiji Takemoto
- Graduate School of Pharmaceutical Sciences
- Kyoto University
- Kyoto 606-8501
- Japan
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Vinogradov MG, Turova OV, Zlotin SG. Recent advances in the asymmetric synthesis of pharmacology-relevant nitrogen heterocycles via stereoselective aza-Michael reactions. Org Biomol Chem 2019; 17:3670-3708. [DOI: 10.1039/c8ob03034k] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In this review, recent applications of a stereoselective aza-Michael reaction for asymmetric synthesis of naturally occurring N-containing heterocyclic scaffolds and their usefulness to pharmacology are summarized.
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Affiliation(s)
- Maxim G. Vinogradov
- N.D. Zelinsky Institute of Organic Chemistry
- Russian Academy of Sciences
- 119991 Moscow
- Russian Federation
| | - Olga V. Turova
- N.D. Zelinsky Institute of Organic Chemistry
- Russian Academy of Sciences
- 119991 Moscow
- Russian Federation
| | - Sergei G. Zlotin
- N.D. Zelinsky Institute of Organic Chemistry
- Russian Academy of Sciences
- 119991 Moscow
- Russian Federation
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9
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Hayama N, Kuramoto R, Földes T, Nishibayashi K, Kobayashi Y, Pápai I, Takemoto Y. Mechanistic Insight into Asymmetric Hetero-Michael Addition of α,β-Unsaturated Carboxylic Acids Catalyzed by Multifunctional Thioureas. J Am Chem Soc 2018; 140:12216-12225. [PMID: 30215516 DOI: 10.1021/jacs.8b07511] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Carboxylic acids and their corresponding carboxylate anions are generally utilized as Brønsted acids/bases and oxygen nucleophiles in organic synthesis. However, a few asymmetric reactions have used carboxylic acids as electrophiles. Although chiral thioureas bearing both arylboronic acid and tertiary amine were found to promote the aza-Michael addition of BnONH2 to α,β-unsaturated carboxylic acids with moderate to good enantioselectivities, the reaction mechanism remains to be clarified. Detailed investigation of the reaction using spectroscopic analysis and kinetic studies identified tetrahedral borate complexes, comprising two carboxylate anions, as reaction intermediates. We realized a dramatic improvement in product enantioselectivity with the addition of 1 equiv of benzoic acid. In this aza-Michael reaction, the boronic acid not only activates the carboxylate ligand as a Lewis acid, together with the thiourea NH-protons, but also functions as a Brønsted base through a benzoyloxy anion to activate the nucleophile. Moreover, molecular sieves were found to play an important role in generating the ternary borate complexes, which were crucial for obtaining high enantioselectivity as demonstrated by DFT calculations. We also designed a new thiourea catalyst for the intramolecular oxa-Michael addition to suppress another catalytic pathway via a binary borate complex using steric hindrance between the catalyst and substrate. Finally, to demonstrate the synthetic versatility of both hetero-Michael additions, we used them to accomplish the asymmetric synthesis of key intermediates in pharmaceutically important molecules, including sitagliptin and α-tocopherol.
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Affiliation(s)
- Noboru Hayama
- Graduate School of Pharmaceutical Sciences , Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501 , Japan
| | - Ryuta Kuramoto
- Graduate School of Pharmaceutical Sciences , Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501 , Japan
| | - Tamás Földes
- Institute of Organic Chemistry, Research Centre for Natural Sciences , Hungarian Academy of Sciences , Magyar tudósok körútja 2 , H-1117 Budapest , Hungary
| | - Kazuya Nishibayashi
- Graduate School of Pharmaceutical Sciences , Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501 , Japan
| | - Yusuke Kobayashi
- Graduate School of Pharmaceutical Sciences , Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501 , Japan
| | - Imre Pápai
- Institute of Organic Chemistry, Research Centre for Natural Sciences , Hungarian Academy of Sciences , Magyar tudósok körútja 2 , H-1117 Budapest , Hungary
| | - Yoshiji Takemoto
- Graduate School of Pharmaceutical Sciences , Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501 , Japan
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10
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Sallio R, Lebrun S, Capet F, Agbossou-Niedercorn F, Michon C, Deniau E. Diastereoselective auxiliary- and catalyst-controlled intramolecular aza-Michael reaction for the elaboration of enantioenriched 3-substituted isoindolinones. Application to the synthesis of a new pazinaclone analogue. Beilstein J Org Chem 2018; 14:593-602. [PMID: 29623121 PMCID: PMC5852534 DOI: 10.3762/bjoc.14.46] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 02/21/2018] [Indexed: 02/03/2023] Open
Abstract
A new asymmetric organocatalyzed intramolecular aza-Michael reaction by means of both a chiral auxiliary and a catalyst for stereocontrol is reported for the synthesis of optically active isoindolinones. A selected cinchoninium salt was used as phase-transfer catalyst in combination with a chiral nucleophile, a Michael acceptor and a base to provide 3-substituted isoindolinones in good yields and diastereomeric excesses. This methodology was applied to the asymmetric synthesis of a new pazinaclone analogue which is of interest in the field of benzodiazepine-receptor agonists.
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Affiliation(s)
- Romain Sallio
- Univ, Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Stéphane Lebrun
- Univ, Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Frédéric Capet
- Univ, Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Francine Agbossou-Niedercorn
- Univ, Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Christophe Michon
- Univ, Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
| | - Eric Deniau
- Univ, Lille, CNRS, Centrale Lille, ENSCL, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000 Lille, France
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11
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Uno BE, Dicken RD, Redfern LR, Stern CM, Krzywicki GG, Scheidt KA. Calcium(ii)-catalyzed enantioselective conjugate additions of amines. Chem Sci 2018; 9:1634-1639. [PMID: 29675209 PMCID: PMC5887857 DOI: 10.1039/c7sc05205g] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 12/15/2017] [Indexed: 02/04/2023] Open
Abstract
The direct enantioselective chiral calcium(ii)·phosphate complex (Ca[CPA]2)-catalyzed conjugate addition of unprotected alkyl amines to maleimides was developed.
The direct enantioselective chiral calcium(ii)·phosphate complex (Ca[CPA]2)-catalyzed conjugate addition of unprotected alkyl amines to maleimides was developed. This mild catalytic system represents a significant advance towards the general convergent asymmetric amination of α,β-unsaturated electrophiles, providing medicinally relevant chiral aminosuccinimide products in high yields and enantioselectivities. Furthermore, the catalyst can be reused directly from a previously chromatographed reaction and still maintain both high yield and selectivity.
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Affiliation(s)
- Brice E Uno
- Department of Chemistry , Center for Molecular Innovation and Drug Discovery , Northwestern University , 2145 Sheridan Rd , Evanston , IL 60208 , USA .
| | - Rachel D Dicken
- Department of Chemistry , Center for Molecular Innovation and Drug Discovery , Northwestern University , 2145 Sheridan Rd , Evanston , IL 60208 , USA .
| | - Louis R Redfern
- Department of Chemistry , Center for Molecular Innovation and Drug Discovery , Northwestern University , 2145 Sheridan Rd , Evanston , IL 60208 , USA .
| | - Charlotte M Stern
- Department of Chemistry , Center for Molecular Innovation and Drug Discovery , Northwestern University , 2145 Sheridan Rd , Evanston , IL 60208 , USA .
| | - Greg G Krzywicki
- Department of Chemistry , Center for Molecular Innovation and Drug Discovery , Northwestern University , 2145 Sheridan Rd , Evanston , IL 60208 , USA .
| | - Karl A Scheidt
- Department of Chemistry , Center for Molecular Innovation and Drug Discovery , Northwestern University , 2145 Sheridan Rd , Evanston , IL 60208 , USA .
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12
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Dutartre M, Bayardon J, Jugé S. Applications and stereoselective syntheses of P-chirogenic phosphorus compounds. Chem Soc Rev 2016; 45:5771-5794. [DOI: 10.1039/c6cs00031b] [Citation(s) in RCA: 233] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This review reports the best stereoselective or asymmetric syntheses, the most efficient P*-building blocks and functionalisation of P-chirogenic compounds, in the light of chiral phosphorus compound applications.
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Affiliation(s)
- Mathieu Dutartre
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB-StéréochIM)
- UMR CNRS 6302
- 21078 Dijon Cedex
- France
| | - Jérôme Bayardon
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB-StéréochIM)
- UMR CNRS 6302
- 21078 Dijon Cedex
- France
| | - Sylvain Jugé
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB-StéréochIM)
- UMR CNRS 6302
- 21078 Dijon Cedex
- France
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13
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Hayama N, Azuma T, Kobayashi Y, Takemoto Y. Chiral Integrated Catalysts Composed of Bifunctional Thiourea and Arylboronic Acid: Asymmetric Aza-Michael Addition of α,β-Unsaturated Carboxylic Acids. Chem Pharm Bull (Tokyo) 2016; 64:704-17. [DOI: 10.1248/cpb.c15-00983] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Noboru Hayama
- Graduate School of Pharmaceutical Sciences, Kyoto University
| | - Takumi Azuma
- Graduate School of Pharmaceutical Sciences, Kyoto University
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14
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Guo J, Yu S. Enantioselective synthesis of benzoindolizidine derivatives using chiral phase-transfer catalytic intramolecular domino aza-Michael addition/alkylation. Org Biomol Chem 2015; 13:1179-86. [DOI: 10.1039/c4ob02227k] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An efficient and enantioselective strategy to synthesize benzoindolizidinesviadomino intramolecular aza-Michael addition/alkylation was developed.
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Affiliation(s)
- Jiajia Guo
- State Key Laboratory of Analytical Chemistry for Life Science
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210093
- China
| | - Shouyun Yu
- State Key Laboratory of Analytical Chemistry for Life Science
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210093
- China
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15
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Shirakawa S, Maruoka K. Neue Entwicklungen bei asymmetrischen Phasentransferreaktionen. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201206835] [Citation(s) in RCA: 139] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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16
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Shirakawa S, Maruoka K. Recent developments in asymmetric phase-transfer reactions. Angew Chem Int Ed Engl 2013; 52:4312-48. [PMID: 23450630 DOI: 10.1002/anie.201206835] [Citation(s) in RCA: 529] [Impact Index Per Article: 48.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Indexed: 11/09/2022]
Abstract
Phase-transfer catalysis has been recognized as a powerful method for establishing practical protocols for organic synthesis, because it offers several advantages, such as operational simplicity, mild reaction conditions, suitability for large-scale synthesis, and the environmentally benign nature of the reaction system. Since the pioneering studies on highly enantioselective alkylations promoted by chiral phase-transfer catalysts, this research field has served as an attractive area for the pursuit of "green" sustainable chemistry. A wide variety of asymmetric transformations catalyzed by chiral onium salts and crown ethers have been developed for the synthesis of valuable organic compounds in the past several decades, especially in recent years.
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Affiliation(s)
- Seiji Shirakawa
- Laboratory of Synthetic Organic Chemistry, Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
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