1
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Hu KW, You X, Wang JZ, Wen X, Sun H, Xu QL, Lai Z. Chiral Phosphoric Acid Catalyzed Asymmetric Desymmetrization of para-Quinamines with Isocyanates: Access to Functionalized Imidazolidin-2-one Derivatives. Org Lett 2021; 23:7873-7877. [PMID: 34581589 DOI: 10.1021/acs.orglett.1c02889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The development of enantioselective desymmetrization of para-quinamines with isocyanates catalyzed by chiral phosphoric acid is reported. The strategy provides concise access to functionalized imidazolidin-2-one derivatives in high yields and enantioselectivities under mild reaction conditions. Remarkably, this reaction could be performed on a gram scale using 5 mol % catalyst loading and the chiral imidazolidin-2-one derivatives could be easily transformed into valuable scaffolds without disturbing the enantiopurity, demonstrating the synthetic utility of this protocol.
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Affiliation(s)
- Kai-Wen Hu
- Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases and State Key Laboratory of Natural Medicines, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210000, China
| | - Xiao You
- Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases and State Key Laboratory of Natural Medicines, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210000, China
| | - Jin-Zheng Wang
- Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases and State Key Laboratory of Natural Medicines, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210000, China
| | - Xiaoan Wen
- Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases and State Key Laboratory of Natural Medicines, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210000, China
| | - Hongbin Sun
- Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases and State Key Laboratory of Natural Medicines, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210000, China
| | - Qing-Long Xu
- Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases and State Key Laboratory of Natural Medicines, China Pharmaceutical University, 24 Tongjiaxiang, Nanjing 210000, China
| | - Zengwei Lai
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
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2
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Zhang Z, Chang W. Progress in Transition-Metal-Catalyzed Cyclization of Carbodiimides. CHINESE J ORG CHEM 2021. [DOI: 10.6023/cjoc202010020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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3
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Das D, Sahoo G, Biswas A, Samanta R. Rh
III
‐Catalyzed Synthesis of Highly Substituted 2‐Pyridones using Fluorinated Diazomalonate. Chem Asian J 2020; 15:360-364. [DOI: 10.1002/asia.201901620] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Indexed: 01/13/2023]
Affiliation(s)
- Debapratim Das
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur 721302 India
| | - Gopal Sahoo
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur 721302 India
| | - Aniruddha Biswas
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur 721302 India
| | - Rajarshi Samanta
- Department of ChemistryIndian Institute of Technology Kharagpur Kharagpur 721302 India
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4
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Transition-metal-free highly efficient synthesis of 2-pyridones from β-keto amides and ynals. Tetrahedron Lett 2019. [DOI: 10.1016/j.tetlet.2019.04.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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5
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Kaur N, Grewal P, Bhardwaj P, Devi M, Verma Y. Nickel-catalyzed synthesis of five-membered heterocycles. SYNTHETIC COMMUN 2019. [DOI: 10.1080/00397911.2019.1594306] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Navjeet Kaur
- Department of Chemistry, Banasthali Vidyapith, Jaipur, India
| | - Pooja Grewal
- Department of Chemistry, Banasthali Vidyapith, Jaipur, India
| | | | - Meenu Devi
- Department of Chemistry, Banasthali Vidyapith, Jaipur, India
| | - Yamini Verma
- Department of Chemistry, Banasthali Vidyapith, Jaipur, India
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6
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Li J, Ye Y, Zhang Y. Cycloaddition/annulation strategies for the construction of multisubstituted pyrrolidines and their applications in natural product synthesis. Org Chem Front 2018. [DOI: 10.1039/c7qo01077j] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Pyrrolidines are privileged substructures of numerous bioactive natural products and drugs.
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Affiliation(s)
- Jundong Li
- Department of Chemistry and Key Laboratory of Chemical Biology of Fujian Province
- iChEM
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen
| | - Yilin Ye
- Department of Chemistry and Key Laboratory of Chemical Biology of Fujian Province
- iChEM
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen
| | - Yandong Zhang
- Department of Chemistry and Key Laboratory of Chemical Biology of Fujian Province
- iChEM
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen
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7
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Kobayashi T, Tanaka K, Ishida M, Yamakita N, Abe H, Ito H. Asymmetric total synthesis of pleurospiroketals A and B. Chem Commun (Camb) 2018; 54:10316-10319. [DOI: 10.1039/c8cc06185h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The first asymmetric total synthesis of pleurospiroketals A and B has been accomplished in 16 steps from 5-methyl-5-hexenoic acid.
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Affiliation(s)
- Toyoharu Kobayashi
- School of Life Sciences
- Tokyo University of Pharmacy and Life Sciences
- Hachioji
- Japan
| | - Konomi Tanaka
- School of Life Sciences
- Tokyo University of Pharmacy and Life Sciences
- Hachioji
- Japan
| | - Masako Ishida
- School of Life Sciences
- Tokyo University of Pharmacy and Life Sciences
- Hachioji
- Japan
| | - Natsumi Yamakita
- School of Life Sciences
- Tokyo University of Pharmacy and Life Sciences
- Hachioji
- Japan
| | - Hideki Abe
- School of Life Sciences
- Tokyo University of Pharmacy and Life Sciences
- Hachioji
- Japan
- Department of Chemical and Biological Sciences
| | - Hisanaka Ito
- School of Life Sciences
- Tokyo University of Pharmacy and Life Sciences
- Hachioji
- Japan
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8
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Grosheva D, Cramer N. Ketene Aminal Phosphates: Competent Substrates for Enantioselective Pd(0)-Catalyzed C–H Functionalizations. ACS Catal 2017. [DOI: 10.1021/acscatal.7b02783] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daria Grosheva
- Laboratory of Asymmetric
Catalysis and Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCSA, BCH 4305, CH-1015 Lausanne, Switzerland
| | - Nicolai Cramer
- Laboratory of Asymmetric
Catalysis and Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC LCSA, BCH 4305, CH-1015 Lausanne, Switzerland
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9
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Affiliation(s)
- Wenzhen Fu
- State Key Laboratory of Bio-Organic
and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
| | - Wenjun Tang
- State Key Laboratory of Bio-Organic
and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
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10
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Chattopadhyay AK, Hanessian S. Cyclic enaminones. Part I: stereocontrolled synthesis using diastereoselective and catalytic asymmetric methods. Chem Commun (Camb) 2016; 51:16437-49. [PMID: 26490402 DOI: 10.1039/c5cc05891k] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclic enaminones are versatile intermediates to construct a variety of azacyclic frameworks and have been widely used in alkaloid synthesis. Here, we summarize three approaches for stereoselective syntheses of cyclic enaminones and their functionalized derivatives. These include chiral substrates (chirons) as starting materials, syntheses employing non-catalytic (stoichiometric) reagents, and catalytic asymmetric methods.
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Affiliation(s)
- Amit Kumar Chattopadhyay
- Department of Chemistry, Université de Montréal, Station Centre Ville, C.P. 6128, Montreal, QC H3C 3J7, Canada.
| | - Stephen Hanessian
- Department of Chemistry, Université de Montréal, Station Centre Ville, C.P. 6128, Montreal, QC H3C 3J7, Canada.
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11
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Chattopadhyay AK, Hanessian S. Cyclic enaminones. Part II: applications as versatile intermediates in alkaloid synthesis. Chem Commun (Camb) 2016; 51:16450-67. [PMID: 26490499 DOI: 10.1039/c5cc05892a] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Among many other strategies, the enaminone approach is an important strategy to construct and diversify the azacyclic core in various alkaloids syntheses. In this brief review we discuss the application of cyclic enaminones as building blocks, as well as potential intermediates in the total synthesis of selected alkaloids.
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Affiliation(s)
- Amit Kumar Chattopadhyay
- Department of Chemistry, Université de Montréal, Station Centre Ville, C. P. 6128, Montréal, Qc H3C 3J7, Canada.
| | - Stephen Hanessian
- Department of Chemistry, Université de Montréal, Station Centre Ville, C. P. 6128, Montréal, Qc H3C 3J7, Canada.
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12
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Neuhaus JD, Willis MC. Homogeneous rhodium(i)-catalysis in de novo heterocycle syntheses. Org Biomol Chem 2016; 14:4986-5000. [DOI: 10.1039/c6ob00835f] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Rh(i)-catalysed reactions often employ mild reaction conditions and offer excellent functional group tolerance, making them ideal transformations for the preparation of complex molecules. This review surveys examples of these synthetically useful transformations as applied to the synthesis of various heterocycles.
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Affiliation(s)
- James D. Neuhaus
- Department of Chemistry
- Chemistry Research Laboratory
- University of Oxford
- Oxford
- UK
| | - Michael C. Willis
- Department of Chemistry
- Chemistry Research Laboratory
- University of Oxford
- Oxford
- UK
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13
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Augé M, Feraldi-Xypolia A, Barbazanges M, Aubert C, Fensterbank L, Gandon V, Kolodziej E, Ollivier C. Double-Stereodifferentiation in Rhodium-Catalyzed [2 + 2 + 2] Cycloaddition: Chiral Ligand/Chiral Counterion Matched Pair. Org Lett 2015. [DOI: 10.1021/acs.orglett.5b01738] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Mylène Augé
- Sorbonne Universités, UPMC Univ Paris 06,
Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, Case
229, 4 Place Jussieu, Paris 75252 Cedex 05, France
| | - Alexandra Feraldi-Xypolia
- Sorbonne Universités, UPMC Univ Paris 06,
Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, Case
229, 4 Place Jussieu, Paris 75252 Cedex 05, France
| | - Marion Barbazanges
- Sorbonne Universités, UPMC Univ Paris 06,
Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, Case
229, 4 Place Jussieu, Paris 75252 Cedex 05, France
| | - Corinne Aubert
- Sorbonne Universités, UPMC Univ Paris 06,
Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, Case
229, 4 Place Jussieu, Paris 75252 Cedex 05, France
| | - Louis Fensterbank
- Sorbonne Universités, UPMC Univ Paris 06,
Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, Case
229, 4 Place Jussieu, Paris 75252 Cedex 05, France
| | - Vincent Gandon
- ICMMO,
UMR CNRS 8182, Univ Paris-Sud 11, 91405 Orsay, France
| | | | - Cyril Ollivier
- Sorbonne Universités, UPMC Univ Paris 06,
Institut Parisien de Chimie Moléculaire, UMR CNRS 8232, Case
229, 4 Place Jussieu, Paris 75252 Cedex 05, France
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14
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Ni-Catalyzed Asymmetric Cycloisomerization of Dienes by Using TADDOL Phosphoramidites. Chemistry 2015; 21:10696-702. [DOI: 10.1002/chem.201500352] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Indexed: 11/07/2022]
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15
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16
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Kriening S, Evagelou A, Claasen B, Baro A, Laschat S. Asymmetric Evanssyn-Aldol Reactions of Terpene-Derived Enals: Scope and Limitations. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402736] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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17
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Ishii M, Mori F, Tanaka K. Rhodium-Catalyzed [2+2+2] Cycloaddition of Diynes with Carbodiimides and Carbon Dioxide under Ambient Conditions. Chemistry 2014; 20:2169-74. [DOI: 10.1002/chem.201304623] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 12/03/2013] [Indexed: 11/09/2022]
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18
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Abels F, Lindemann C, Schneider C. A General Strategy for the Catalytic, Highly Enantio- and Diastereoselective Synthesis of Indolizidine-Based Alkaloids. Chemistry 2014; 20:1964-79. [DOI: 10.1002/chem.201304086] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Indexed: 11/07/2022]
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19
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Oberg KM, Martin TJ, Oinen ME, Dalton DM, Friedman RK, Neely JM, Rovis T. Enantioselective Rhodium-Catalyzed [2+2+2] Cycloaddition of Pentenyl Isocyanate and 4-Ethynylanisole: Preparation and Use of Taddolpyrrolidine Phosphoramidite. ORGANIC SYNTHESES; AN ANNUAL PUBLICATION OF SATISFACTORY METHODS FOR THE PREPARATION OF ORGANIC CHEMICALS 2014; 91:150-161. [PMID: 25346554 PMCID: PMC4205754 DOI: 10.15227/orgsyn.091.0150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Caution, alkyl acyl azides can rapidly decompose with heat to release large amounts of nitrogen. Care should be taken during handling: do not attempt to convert neat and avoid handling neat.
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20
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Brimioulle R, Bach T. Enantioselective Lewis Acid Catalysis of Intramolecular Enone [2+2] Photocycloaddition Reactions. Science 2013; 342:840-3. [DOI: 10.1126/science.1244809] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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21
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Chou SSP, Huang JL. Studies toward the first stereoselective total synthesis of (±)-quinolizidine 195C and other transformations. Molecules 2013; 18:8243-56. [PMID: 23857127 PMCID: PMC6269906 DOI: 10.3390/molecules18078243] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 07/02/2013] [Accepted: 07/03/2013] [Indexed: 11/16/2022] Open
Abstract
Starting from a thio-substituted 4-quinolizidinone, a series of C-6 alkylated derivatives with a trans C-6, C-9a relationship was synthesized. Further transformations led to the first stereoselective total synthesis of the structure proposed for (±)-quinolizidine 195C, the major alkaloid isolated from the skin extracts of the Madagascan frog Mantella betsileo. Since the spectral data of the synthetic and natural products differed significantly, the true structure of (±)-quinolizidine 195C remains uncertain.
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Affiliation(s)
- Shang-Shing P Chou
- Department of Chemistry, Fu Jen Catholic University, New Taipei City 24205, Taiwan.
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22
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Dalton DM, Rovis T. Catalytic, asymmetric indolizidinone aza-quaternary stereocenter synthesis: expedient synthesis of the cylindricine alkaloid core. Org Lett 2013; 15:2346-9. [PMID: 23631448 PMCID: PMC3809156 DOI: 10.1021/ol400529k] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Rh(I)•CKphos catalyzed [2 + 2 + 2] cycloaddition of 1,1-disubstituted alkenyl isocyanates and alkyl alkynes selectively forms previously inaccessible vinylogous amide indolizidinone cycloadducts, establishing an aza-quaternery stereocenter with excellent enantioselectivities (up to 98% ee). This advance enables a seven step catalytic, asymmetric synthesis of the tricyclic core of the cylindricine alkaloids with excellent control of product selectivity as well as regio- and enantioselectivity.
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Affiliation(s)
- Derek M. Dalton
- Department of Chemistry, Colorado State University, Ft. Collins, CO 80523
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Ft. Collins, CO 80523
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23
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Dalton DM, Rappé AK, Rovis T. Perfluorinated Taddol Phosphoramidite as an L,Z-Ligand on Rh(I) and Co(-I): Evidence for Bidentate Coordination via Metal-C 6F 5 Interaction. Chem Sci 2013; 4:2062-2070. [PMID: 23671790 PMCID: PMC3650898 DOI: 10.1039/c3sc50271f] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Perfluorinated Taddol-based phosphoramidite, CKphos, is a highly selective ligand for formation of the vinylogous amide cycloadduct in the Rh(I) catalyzed [2+2+2] cycloaddition of alkenyl isocyanates and alkynes. CKphos overrides substrate bias of product selectivity in the cycloaddition, providing indolizinones in excellent product and enantioselectivities. Excellent selectivities are attributed to a shortened Rh-P bond and coordination of one C6F5 to rhodium via a Z-type interaction, making the phosphoramidite a bidentate L,Z-ligand on rhodium. Evidence for the shortened Rh-P and C6F5 coordination is provided by X-ray, NMR and DFT computation analyses. Additionally, an anionic cobalt complex with CKphos was synthesized and two Co-C6F5 interactions are seen. Rh(C2H4)Cl•CKphos catalyst in the [2+2+2] cycloaddition of alkenyl isocyanates and alkynes represents a rare example of metal-C6F5 Z-type interaction affecting selectivity in transition metal catalysis.
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Affiliation(s)
- Derek M. Dalton
- Department of Chemistry, Colorado State University, Fort Collins, CO 80526, USA
| | - Anthony K. Rappé
- Department of Chemistry, Colorado State University, Fort Collins, CO 80526, USA
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Fort Collins, CO 80526, USA
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24
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Martin TJ, Rovis T. A catalytic asymmetric synthesis of polysubstituted piperidines using a rhodium(I)-catalyzed [2+2+2] cycloaddition employing a cleavable tether. Angew Chem Int Ed Engl 2013; 52:5368-71. [PMID: 23606664 DOI: 10.1002/anie.201301741] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Timothy J Martin
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
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25
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Martin TJ, Rovis T. A Catalytic Asymmetric Synthesis of Polysubstituted Piperidines Using a Rhodium(I)-Catalyzed [2+2+2] Cycloaddition Employing a Cleavable Tether. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201301741] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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26
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McCormack MP, Waters SP. Synthesis of functionalized indolizidines through Pauson-Khand cycloaddition of 2-allylpyrrolidines. J Org Chem 2013; 78:1176-83. [PMID: 23311620 DOI: 10.1021/jo302734w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A concise entry to functionalized indolizidine scaffolds through a domino 2-aza-Cope-[3 + 2] dipolar cycloaddition and Pauson-Khand [2 + 2 + 1] cyclization has been accomplished. The process was conducted under mild conditions to afford diverse indolizidine systems as single diastereomers in good overall yields.
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Affiliation(s)
- Michael P McCormack
- Department of Chemistry, The University of Vermont, 82 University Place, Burlington, Vermont 05405, USA
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27
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Faulkner A, Scott JS, Bower JF. Palladium catalyzed cyclizations of oximeesters with 1,1-disubstituted alkenes: synthesis of α,α-disubstituted dihydropyrroles and studies towards an asymmetric protocol. Chem Commun (Camb) 2013; 49:1521-3. [DOI: 10.1039/c2cc38944d] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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28
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Perreault S, Rovis T. Enantioselective Synthesis of the Tricyclic Core of FR901483 Featuring a Rh-Catalyzed [2+2+2] Cycloaddition. SYNTHESIS-STUTTGART 2013; 45:719-728. [PMID: 25506094 PMCID: PMC4263289 DOI: 10.1055/s-0032-1316786] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
An efficient approach to the tricyclic framework of FR901483 is described. The sequence features a [3, 3]-sigmatropic rearrangement of a cyanate into an isocyanate, followed by its subsequent asymmetric rhodium-catalyzed [2+2+2] cycloaddition with a terminal alkyne for the synthesis of the indolizidine core. The aza-tricyclic core is completed using an intramolecular benzoin reaction to close the last ring of the natural product. Through a model study of the key cycloaddition, we evaluated the impact of different substituents on the tether of the alkenyl isocyanate.
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Affiliation(s)
- Stéphane Perreault
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523
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29
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Augé M, Barbazanges M, Tran AT, Simonneau A, Elley P, Amouri H, Aubert C, Fensterbank L, Gandon V, Malacria M, Moussa J, Ollivier C. Atroposelective [2+2+2] cycloadditions catalyzed by a rhodium(i)–chiral phosphate system. Chem Commun (Camb) 2013; 49:7833-5. [DOI: 10.1039/c3cc43188f] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Basch CH, Brinck JA, Ramos JE, Habay SA, Yap GPA. Synthesis of cis-octahydroindoles via intramolecular 1,3-dipolar cycloaddition of 2-acyl-5-aminooxazolium salts. J Org Chem 2012; 77:10416-21. [PMID: 23092391 DOI: 10.1021/jo301600p] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A concise method for the diastereoselective synthesis of octahydroindoles is presented. The products contain 2-amido and 7-hydroxyl substituents. A series of 2-acyl-5-aminooxazoles were prepared in one step. Upon methylation of the oxazole nitrogen atom, the substrates underwent rapid intramolecular 1,3-dipolar cycloaddition with a tethered alkene and, after reduction with excess hydride, produced octahydroindoles with excellent diastereoselectivity. The method allows for the installation of α-quaternary stereogenic carbon atoms.
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Affiliation(s)
- Corey H Basch
- Department of Chemistry, Henson School of Science and Technology, Salisbury University, 1101 Camden Avenue, Salisbury, Maryland 21801, USA
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31
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Pichota A, Gramlich V, Bichsel HU, Styner T, Knöpfel T, Wünsch R, Hintermann T, Schweizer WB, Beck AK, Seebach D. Preparation and Characterization of New C2- and C1-Symmetric Nitrogen, Oxygen, Phosphorous, and Sulfur Derivatives and Analogs of TADDOL. Part II. Helv Chim Acta 2012. [DOI: 10.1002/hlca.201200147] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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32
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Onodera G, Suto M, Takeuchi R. Iridium-Catalyzed [2+2+2] Cycloaddition of α,ω-Diynes with Isocyanates. J Org Chem 2011; 77:908-20. [DOI: 10.1021/jo202083z] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gen Onodera
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara,
Kanagawa 252-5258, Japan
| | - Mari Suto
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara,
Kanagawa 252-5258, Japan
| | - Ryo Takeuchi
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo, Sagamihara,
Kanagawa 252-5258, Japan
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33
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Shu W, Yu Q, Jia G, Ma S. Palladium-Catalyzed Three-Component Reaction of 2,3-Allenyl Amines, Isocyanates, and Organic Halides: A Diversified Assembly of Imidazolidinones. Chemistry 2011; 17:4720-3. [DOI: 10.1002/chem.201003611] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2010] [Indexed: 11/06/2022]
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34
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Oberg KM, Rovis T. Enantioselective rhodium-catalyzed [4+2] cycloaddition of α,β-unsaturated imines and isocyanates. J Am Chem Soc 2011; 133:4785-7. [PMID: 21401131 DOI: 10.1021/ja200766k] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
A [4+2] cycloaddition of α,β-unsaturated imines and isocyanates catalyzed by a phosphoramidite-rhodium complex provides pyrimidinones in good yields and high enantioselectivities.
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Affiliation(s)
- Kevin M Oberg
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
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35
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36
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Koay N, Campeau LC. Efficient preparation of 3-substituted quinazolinediones directly from anthranilic acids and isocyanates. J Heterocycl Chem 2010. [DOI: 10.1002/jhet.551] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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37
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Su Y, Zhao M, Han K, Song G, Li X. Synthesis of 2-pyridones and iminoesters via Rh(III)-catalyzed oxidative coupling between acrylamides and alkynes. Org Lett 2010; 12:5462-5. [PMID: 21033749 DOI: 10.1021/ol102306c] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Catalytic oxidative coupling between acrylamides and alkynes was achieved using 0.5 mol % loading of [RhCp*Cl(2)](2) with Cu(OAc)(2) as an oxidant. 2-Pyridones, iminoesters, and substituted indoles could be obtained as a result of the electronic and steric effects of the substituents in the acrylamides.
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Affiliation(s)
- Yan Su
- Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, P. R. China 116023
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38
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Niphakis MJ, Turunen BJ, Georg GI. Synthesis of 6- and 7-membered cyclic enaminones: scope and mechanism. J Org Chem 2010; 75:6793-805. [PMID: 20929269 PMCID: PMC2953738 DOI: 10.1021/jo100907u] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Six- and seven-membered cyclic enaminones can be prepared using common, environmentally benign reagents. Amino acids are used as synthetic precursors allowing diversification and the incorporation of chirality. The key reaction in this multistep process involves deprotection of Boc-amino ynones and subsequent treatment with methanolic K(2)CO(3) to induce cyclization. A β-amino elimination side reaction was identified in a few labile substrates that led to either loss of stereochemical purity or degradation. This process can be mitigated in specific cases using mild deprotection conditions. NMR and deuterium-labeling experiments provided valuable insight into the workings and limitations of this reaction. Although disguised as a 6-endo-dig cyclization, the reagents employed in the transformation play a direct role in bond-making and bond-breaking, thus changing the mode of addition to a 6-endo-trig cyclization. This method can be used to construct an array of monocyclic and bicyclic scaffolds, many of which are found in well-known natural products (e.g., indolizidine, quinolizidine, and Stemona alkaloids).
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Affiliation(s)
- Micah J. Niphakis
- Department of Medicinal Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, The University of Kansas Center of Excellence in Chemical Methodologies and Library Development, Structural Biology Center, 2121 Simons Drive, Lawrence, Kansas 66047
| | - Brandon J. Turunen
- Department of Medicinal Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, The University of Kansas Center of Excellence in Chemical Methodologies and Library Development, Structural Biology Center, 2121 Simons Drive, Lawrence, Kansas 66047
| | - Gunda I. Georg
- Department of Medicinal Chemistry and the Institute for Therapeutics Discovery and Development, University of Minnesota, 717 Delaware Street SE, Minneapolis, Minnesota 55414
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39
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Hyster TK, Rovis T. Rhodium-catalyzed oxidative cycloaddition of benzamides and alkynes via C-H/N-H activation. J Am Chem Soc 2010; 132:10565-9. [PMID: 20662529 PMCID: PMC2929375 DOI: 10.1021/ja103776u] [Citation(s) in RCA: 532] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The oxidative cycloaddition of benzamides and alkynes has been developed. The reaction utilizes Rh(III) catalysts in the presence of Cu(II) oxidants, and is proposed to proceed by N-H metalation of the amide followed by ortho C-H activation. The resultant rhodacycle undergoes alkyne insertion to form isoquinolones in good yield. The reaction is tolerant of extensive substitution on the amide, alkyne, and arene, including halides, silyl ethers, and unprotected aldehydes as substituents. Unsymmetrical alkynes proceed with excellent regioselectivity, and heteroaryl carboxamides are tolerated leading to intriguing scaffolds for medicinal chemistry. A series of competition experiments shed further light on the mechanism of the transformation and reasons for selectivity.
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Affiliation(s)
- Todd K. Hyster
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523
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40
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Teichert JF, Feringa BL. Phosphoramidites: privileged ligands in asymmetric catalysis. Angew Chem Int Ed Engl 2010; 49:2486-528. [PMID: 20333685 DOI: 10.1002/anie.200904948] [Citation(s) in RCA: 541] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Asymmetric catalysis with transition-metal complexes is the basis for a vast array of stereoselective transformations and has changed the face of modern synthetic chemistry. Key to this success has been the design of chiral ligands to control the regio-, diastereo-, and enantioselectivity. Phosphoramidites have emerged as a highly versatile and readily accessible class of chiral ligands. Their modular structure enables the formation of ligand libraries and easy fine-tuning for a specific catalytic reaction. Phosphoramidites frequently show exceptional levels of stereocontrol, and their monodentate nature is essential in combinatorial catalysis, where a ligand-mixture approach is used. In this Review, recent developments in asymmetric catalysis with phosphoramidites used as ligands are discussed, with a focus on the formation of carbon-carbon and carbon-heteroatom bonds.
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Affiliation(s)
- Johannes F Teichert
- Stratingh Institute for Chemistry and Center for Systems Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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41
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New chiral phosphoramidite complexes of iron as catalytic precursors in the oxidation of activated methylene groups. Molecules 2010; 15:2631-50. [PMID: 20428070 PMCID: PMC6257337 DOI: 10.3390/molecules15042631] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 03/31/2010] [Accepted: 04/06/2010] [Indexed: 11/17/2022] Open
Abstract
New phosphoramidite complexes of iron were synthesized and structurally characterized. Reaction of the known chiral phosphoramidites (RO)2PNR'2 (R = binaphthyl, R' = CH3, 1a; R = binaphthyl, R' = benzyl, 1b) with [FeBr(Cp)(CO)2] afforded the title compounds [FeBr(Cp)(CO)(1a,b)] (4a,b) in 34 and 65 % isolated yields as mixtures of diastereomers, since both the metal and the ligand are stereogenic. Similarly, reaction of 1b with [Fe(Cp)I(CO)2] in the presence of catalytic [Fe(Cp)(CO)2]2 afforded [Fe(Cp)I(CO)(1b)] (5b) in 81% yield as a mixture of diastereomers. The molecular structures of 4a, 4b and 5 were determined, revealing a pseudo octahedral coordination geometry about the iron center. The new metal complexes are catalytically active in the oxidation of benzylic methylene groups to the corresponding ketones, utilizing t-BuOOH as oxidant (2 mol% catalyst, 36 h, room temperature, 31-80% yield).
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Yu RT, Friedman RK, Rovis T. Enantioselective rhodium-catalyzed [4+2+2] cycloaddition of dienyl isocyanates for the synthesis of bicyclic azocine rings. J Am Chem Soc 2010; 131:13250-1. [PMID: 19711950 DOI: 10.1021/ja906641d] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A highly enantioselective rhodium-catalyzed [4+2+2] cycloaddition of terminal alkynes and dienyl isocyanates has been developed. The cycloaddition provides a rapid entry to highly functionalized and enantioenriched bicyclic azocines. This reaction represents the first [4+2+2] cycloaddition strategy to construct nitrogen-containing eight-membered rings.
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Affiliation(s)
- Robert T Yu
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
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43
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Oinen ME, Yu RT, Rovis T. Excess substrate is a spectator ligand in a rhodium-catalyzed asymmetric [2 + 2 + 2] cycloaddition of alkenyl isocyanates with tolanes. Org Lett 2009; 11:4934-7. [PMID: 19803471 DOI: 10.1021/ol9020805] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Excess substrate has been identified as an unintended spectator ligand affecting enantioselectivity in the [2 + 2 + 2] cycloaddition of alkenyl isocyanates with tolanes. Replacement of excess substrate with an exogenous additive affords products with consistent and higher ee's. The increase in enantioselectivity is the result of a change in composition of a proposed rhodium(III) intermediate on the catalytic cycle. The net result is a rational probe of a short-lived rhodium(III) intermediate and gives insight that may have applications in many rhodium-catalyzed reactions.
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Affiliation(s)
- Mark Emil Oinen
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
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44
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Dalton DM, Oberg KM, Yu RT, Lee EE, Perreault S, Oinen ME, Pease ML, Malik G, Rovis T. Enantioselective rhodium-catalyzed [2 + 2 + 2] cycloadditions of terminal alkynes and alkenyl isocyanates: mechanistic insights lead to a unified model that rationalizes product selectivity. J Am Chem Soc 2009; 131:15717-28. [PMID: 19817441 PMCID: PMC2796191 DOI: 10.1021/ja905065j] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This manuscript describes the development and scope of the asymmetric rhodium-catalyzed [2 + 2 + 2] cycloaddition of terminal alkynes and alkenyl isocyanates leading to the formation of indolizidine and quinolizidine scaffolds. The use of phosphoramidite ligands proved crucial for avoiding competitive terminal alkyne dimerization. Both aliphatic and aromatic terminal alkynes participate well, with product selectivity a function of both the steric and electronic character of the alkyne. Manipulation of the phosphoramidite ligand leads to tuning of enantio- and product selectivity, with a complete turnover in product selectivity seen with aliphatic alkynes when moving from Taddol-based to biphenol-based phosphoramidites. Terminal and 1,1-disubstituted olefins are tolerated with nearly equal efficacy. Examination of a series of competition experiments in combination with analysis of reaction outcome shed considerable light on the operative catalytic cycle. Through a detailed study of a series of X-ray structures of rhodium(cod)chloride/phosphoramidite complexes, we have formulated a mechanistic hypothesis that rationalizes the observed product selectivity.
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Affiliation(s)
- Derek M. Dalton
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Kevin M. Oberg
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Robert T. Yu
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Ernest E. Lee
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Stéphane Perreault
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Mark Emil Oinen
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Melissa L. Pease
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Guillaume Malik
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Fort Collins, CO, 80523
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Perreault S, Rovis T. Multi-component cycloaddition approaches in the catalytic asymmetric synthesis of alkaloid targets. Chem Soc Rev 2009; 38:3149-59. [PMID: 19847348 PMCID: PMC2893402 DOI: 10.1039/b816702h] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cycloaddition reactions are attractive strategies for the rapid formation of molecular complexity in organic synthesis, as multiple bonds are formed in a single process. To this end, several research groups have been actively involved in the development of catalytic methods to activate readily accessible pi-components to achieve cycloadditions. However, the use of C-N pi-components for the formation of heterocycles by these processes is less well developed. It has been previously demonstrated that the combination of different isocyanates with two alkynes yields pyridones of several types by metal-catalyzed [2 + 2 + 2] cycloadditions. The potential of this chemistry has been extended to alkenes as C-C pi-components, allowing the formation of sp(3)-stereocenters. In this tutorial review directed towards [n + 2 + 2] cycloadditions of heterocumulenes, alkynes and alkenes, the recent advances in the catalytic asymmetric synthesis of indolizidine, quinolizidine and azocine skeletons are discussed.
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Affiliation(s)
- Stéphane Perreault
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
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46
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Synthesis of substituted 6-imino-2-piperidinones by Rh-catalyzed [4+2] annulation of 4-alkynals with carbodiimides. Tetrahedron 2009. [DOI: 10.1016/j.tet.2009.06.115] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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47
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Abstract
A mild and general route for preparing dienamides is described. Nickel imidazolylidene complexes were used to mediate cycloadditive coupling between enynes and isocyanates. Dienamides were prepared in excellent yields and with good E:Z selectivity. These dienamides can be further manipulated through oxidative cyclization methods. When a terminal enyne is employed, cyclization affords a lactam rather than a dienamide.
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Affiliation(s)
| | - Janis Louie
- University of Utah 315S 1400 E Salt Lake City UT 84112
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48
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Friedman RK, Rovis T. Predictable and regioselective insertion of internal unsymmetrical alkynes in rhodium-catalyzed cycloadditions with alkenyl isocyanates. J Am Chem Soc 2009; 131:10775-82. [PMID: 19569692 PMCID: PMC2737069 DOI: 10.1021/ja903899c] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A regioselective, rhodium-catalyzed cycloaddition between a variety of internal, unsymmetrical alkynes is described. We document the impact of both steric and electronic properties of the alkyne on reaction course, efficiency, and enantioselectivity. The substituent that better stabilizes a positive charge or the larger group, all else being equal, inserts distal to the carbonyl moiety in a predictable and controllable fashion. The reaction scope is broad and the enantioselectivities are high, providing an "instruction manual" for substrate choice when utilizing this reaction as a synthetic tool.
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Affiliation(s)
| | - Tomislav Rovis
- Department of Chemistry, Colorado State University Fort Collins, Colorado 80523
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49
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Friedman RK, Oberg KM, Dalton DM, Rovis T. Phosphoramidite-Rhodium Complexes as Catalysts for the Asymmetric [2+2+2] Cycloaddition of Alkenyl Isocyanates and Alkynes. PURE APPL CHEM 2009; 82:1353-1364. [PMID: 20622923 PMCID: PMC2899493 DOI: 10.1351/pac-con-09-12-09] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The discovery and development of the asymmetric rhodium-catalyzed [2+2+2] cycloaddition of alkenyl isocyanates and exogenous alkynes to form indolizinone and quinolizinone scaffolds is described. This methodology has been expanded to include substituted alkenes and dienes, a variety of sterically and electronically diverse alkynes, and carbodiimides in place of the isocyanate. Through X-ray analysis of Rh(cod)/phosphoramidite complexes, additives that modify the enantio-determining step, and other experimental data, a mechanism has been proposed that explains lactam, vinylogous amide, and pyridone products and the factors governing their formation. Finally, we have applied this methodology to the synthesis of (+)-lasubine-II and (-)-209D.
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50
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Oberg KM, Lee EE, Rovis T. Regioselective rhodium-catalyzed intermolecular [2+2+2] cycloaddition of alkynes and isocyanates to form pyridones. Tetrahedron 2009; 65:5056-5061. [PMID: 21927511 DOI: 10.1016/j.tet.2009.02.021] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
A highly regioselective rhodium-catalyzed intermolecular [2+2+2] cycloaddition of terminal alkynes with a variety of isocyanates to provide 2- and 4-pyridones has been developed. This reaction proceeds in good to excellent yields and overcomes the problem of dimerization and trimerization through the use of phosphoramidite ligands. A CO migration in the metallacycle is proposed to account for the formation of 4-pyridone.
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Affiliation(s)
- Kevin M Oberg
- Department of Chemistry, Colorado State Univeristy, Fort Collins, CO 80523, USA
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