1
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Kluga R, Kinens A, Suna E. Chiral 4-MeO-Pyridine (MOPY) Catalyst for Enantioselective Cyclopropanation: Attenuation of Lewis Basicity Leads to Improved Catalytic Efficiency. Chemistry 2024; 30:e202301136. [PMID: 37781964 DOI: 10.1002/chem.202301136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 09/26/2023] [Accepted: 09/29/2023] [Indexed: 10/03/2023]
Abstract
The design of pyridine-derived organocatalysts aims at the increase of their Lewis basicity, however such an approach is not always efficient. For example, strongly Lewis basic DMAP is completely inefficient as catalyst in the cyclopropanation reaction. Herein we disclose an alternative approach that relies on attenuation of DMAP Lewis basicity. Specifically, the replacement of 4-dimethylamino substituent in DMAP for 4-MeO group delivered a highly efficient catalyst for cyclopropanation of electron-deficient olefins with α-bromoketones. Kinetic studies provide compelling evidence that the superior catalytic efficiency of 4-MeO pyridine (MOPY) is to be attributed to the favorable balance between Lewis basicity and leaving group ability. The use of chiral, enantiomerically pure MOPY catalyst has helped to achieve high enantioselectivities (up to 91 : 9 er) in the previously unreported pyridine-catalyzed cyclopropanation reaction.
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Affiliation(s)
- Rihards Kluga
- Latvian Institute of Organic Synthesis, Aizkraukles 21, LV-1006, Riga, Latvia
- Department of Chemistry, University of Latvia, Jelgavas 1, LV-1004, Riga, Latvia
| | - Artis Kinens
- Latvian Institute of Organic Synthesis, Aizkraukles 21, LV-1006, Riga, Latvia
- Department of Chemistry, University of Latvia, Jelgavas 1, LV-1004, Riga, Latvia
| | - Edgars Suna
- Latvian Institute of Organic Synthesis, Aizkraukles 21, LV-1006, Riga, Latvia
- Department of Chemistry, University of Latvia, Jelgavas 1, LV-1004, Riga, Latvia
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2
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Ratnam S, Unone S, Janssen-Müller D. 2,2'-Biquinoline-Based Recyclable Electroauxiliaries for the Generation of Alkyl Radicals via C-C Bond Cleavage. Chemistry 2023; 29:e202301685. [PMID: 37265104 DOI: 10.1002/chem.202301685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/01/2023] [Accepted: 06/02/2023] [Indexed: 06/03/2023]
Abstract
Alkyl radical precursors are essential for a wide variety of photocatalytic and 3d-metal-catalyzed C-C bond forming reactions. Neutral organic heterocycles as electroauxiliaries such as 4-alkyl Hantzsch esters have become reliable tools for alkyl radical formation. Here we show that 2,2'-biquinoline-derived alkyl-substituted dihydroquinolines act as competent radical precursors with the ability to form primary, secondary and tertiary alkyl radicals. Hydroalkylation of benzalmalononitriles and N-Boc protected diazenes has been achieved through copper catalysis under mild conditions of 50 °C with good to very good yields of up to 85 %. Furthermore, the dihydroquinolines' reactivity towards a denitrative alkylation of nitroolefins such as β-nitrostyrene was discovered. Most importantly, the released biquinoline can be recycled, which greatly improves the overall atom-economy of these alkyl radical precursors in comparison to previous N-heterocyclic electroauxiliaries.
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Affiliation(s)
- Shahilan Ratnam
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Shreya Unone
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
| | - Daniel Janssen-Müller
- Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany
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3
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Pitre SP, Allred TK, Overman LE. Lewis Acid Activation of Fragment-Coupling Reactions of Tertiary Carbon Radicals Promoted by Visible-Light Irradiation of EDA Complexes. Org Lett 2021; 23:1103-1106. [PMID: 33492152 DOI: 10.1021/acs.orglett.1c00023] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The addition of tertiary carbon radicals generated from N-(acyloxy)phthalimide esters to cyclic α,β-unsaturated ketones and lactones is markedly enhanced by the addition of substoichiometric amounts of a Ln(OTf)3. The reaction is accomplished by irradiation with visible light in the absence of a photosensitizer and is suggested to proceed by excitation of a ternary electron donor-acceptor complex between the NHPI ester, Hantzsch ester, and a Ln(OTf)3.
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Affiliation(s)
- Spencer P Pitre
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, Oklahoma 74078, United States
| | - Tyler K Allred
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Larry E Overman
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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4
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Nagatomo M, Zhang K, Fujino H, Inoue M. Et 3 B/Et 2 AlCl/O 2 -Mediated Radical Coupling Reaction between α-Alkoxyacyl Tellurides and 2-Hydroxybenzaldehyde Derivatives. Chem Asian J 2020; 15:3820-3824. [PMID: 33006274 DOI: 10.1002/asia.202001090] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/01/2020] [Indexed: 12/19/2022]
Abstract
A newly devised radical-based strategy enabled coupling between multiply oxygenated α-alkoxyacyl tellurides and 2-hydroxybenzaldehyde derivatives. A reagent combination of Et3 B, Et2 AlCl, and O2 promoted the formation of the α-alkoxy carbon radical from the α-alkoxyacyl telluride and the addition of the radical to the carbonyl group of 2-hydroxybenzaldehyde. The reaction chemo- and stereoselectively forged the hindered C-C bond between two oxygen-functionalized carbons at ambient temperature. The method was applied to the preparation of 12 coupling adducts with three to six contiguous stereocenters and to the concise synthesis of an antitumor compound, LLY-283.
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Affiliation(s)
- Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Keshu Zhang
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Haruka Fujino
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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5
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Fujino H, Fukuda T, Nagatomo M, Inoue M. Convergent Total Synthesis of Hikizimycin Enabled by Intermolecular Radical Addition to Aldehyde. J Am Chem Soc 2020; 142:13227-13234. [PMID: 32628018 DOI: 10.1021/jacs.0c06354] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hikizimycin (1), which exhibits powerful anthelmintic activity, has the most densely functionalized structure among nucleoside antibiotics. A central 4-amino-4-deoxyundecose of 1 possesses 10 contiguous stereocenters on a C1-C11 linear chain and is decorated with a cytosine base at C1 and a 3-amino-3-deoxyglucose at C6-OH. These distinctive structural features of 1 make it an extremely challenging target for de novo construction. Herein, we report a convergent total synthesis of 1 from four known components: 3-azide-3-deoxyglucose derivative 4, bis-TMS-cytosine 5, d-mannose 9, and d-galactose derivative 10. We first designed and devised a novel radical coupling reaction between multiply hydroxylated aldehydes and α-alkoxyacyl tellurides. The generality and efficiency of this process was demonstrated by the coupling of 7c and 8, which were readily accessible from two hexoses, 9 and 10, respectively. Et3B and O2 rapidly induced decarbonylative radical formation from α-alkoxyacyl telluride 8, and intermolecular addition of the generated α-alkoxy radical to aldehyde 7c yielded 4-amino-4-deoxyundecose 6-α with installation of the desired C5,6-stereocenters. Subsequent attachments of the cytosine with 5 and of the 3-azide-3-deoxyglucose with 4 were realized through selective activation of the C1-acetal and selective deprotection of the C6-hydroxy group. Finally, the 3 amino and 10 hydroxy groups were liberated in a single step to deliver the target 1. Thus, the combination of the newly developed radical-coupling and protective-group strategies minimized the functional group manipulations and thereby enabled the synthesis of 1 from 10 in only 17 steps. The present total synthesis demonstrates the versatility of intermolecular radical addition to aldehyde for the first time and offers a new strategic design for multistep target-oriented syntheses of various nucleoside antibiotics and other bioactive natural products.
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Affiliation(s)
- Haruka Fujino
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Takumi Fukuda
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masanori Nagatomo
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masayuki Inoue
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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6
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Lingua H, Dwadnia N, Siri D, Bertrand MP, Feray L. Reactivity of benzylidene and alkylidenemalonates in radical addition mediated with dialkylzincs – An intriguing story. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.11.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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7
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Chen JQ, Chang R, Wei YL, Mo JN, Wang ZY, Xu PF. Direct Decarboxylative–Decarbonylative Alkylation of α-Oxo Acids with Electrophilic Olefins via Visible-Light Photoredox Catalysis. J Org Chem 2017; 83:253-259. [DOI: 10.1021/acs.joc.7b02628] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Jian-Qiang Chen
- State Key Laboratory of Applied
Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Rui Chang
- State Key Laboratory of Applied
Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Yun-Long Wei
- State Key Laboratory of Applied
Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Jia-Nan Mo
- State Key Laboratory of Applied
Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Zhu-Yin Wang
- State Key Laboratory of Applied
Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Peng-Fei Xu
- State Key Laboratory of Applied
Organic Chemistry, Lanzhou University, Lanzhou, 730000, P. R. China
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8
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Zhang H, Han M, Chen T, Xu L, Yu L. Poly(N-isopropylacrylamide-co-l-proline)-catalyzed Claisen–Schmidt and Knoevenagel condensations: unexpected enhanced catalytic activity of the polymer catalyst. RSC Adv 2017. [DOI: 10.1039/c7ra09412d] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The heterogeneous catalyst is more active than the homogeneous one! The abnormal phenomenon is probably caused by the polymer, which enriches the reactants around the reaction sites.
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Affiliation(s)
- Hao Zhang
- Institute of Pesticide
- School of Chemistry and Chemical Engineering
- School of Horticulture and Plant Protection
- Yangzhou University
- Yangzhou
| | - Mengting Han
- Institute of Pesticide
- School of Chemistry and Chemical Engineering
- School of Horticulture and Plant Protection
- Yangzhou University
- Yangzhou
| | - Tian Chen
- Institute of Pesticide
- School of Chemistry and Chemical Engineering
- School of Horticulture and Plant Protection
- Yangzhou University
- Yangzhou
| | - Lin Xu
- Institute of Pesticide
- School of Chemistry and Chemical Engineering
- School of Horticulture and Plant Protection
- Yangzhou University
- Yangzhou
| | - Lei Yu
- Institute of Pesticide
- School of Chemistry and Chemical Engineering
- School of Horticulture and Plant Protection
- Yangzhou University
- Yangzhou
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9
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Theoretical investigation of the reaction of dialkylzincs with α-alkoxycarbonyl radicals. Evaluation of α-bromoacrylates as radical acceptors in radical-polar crossover processes. Tetrahedron 2015. [DOI: 10.1016/j.tet.2015.09.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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10
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Castle SL. Total synthesis of the congested propellane alkaloid (-)-acutumine. CHEM REC 2014; 14:580-91. [PMID: 24863243 DOI: 10.1002/tcr.201400005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Indexed: 11/11/2022]
Abstract
The enantioselective total synthesis of (-)-acutumine is described. The synthetic strategy was inspired by the premise that the cyclohexenone ring could be derived from an aromatic precursor. After successful construction of a propellane model system, an initial attempt to prepare the spirocyclic subunit was thwarted by incorrect regioselectivity in a radical cyclization. A second-generation approach involving a radical-polar crossover reaction was successful, and the chemistry developed in the aforementioned model system was then applied to synthesize the natural product. Key reactions included a phenolic oxidation, a diastereoselective ketone allylation utilizing Nakamura's chiral allylzinc reagent, an anionic oxy-Cope rearrangement, an acid-promoted cyclization of a secondary amine onto an α,β-unsaturated ketal, and a regioselective methyl enol etherification of a 1,3-diketone.
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Affiliation(s)
- Steven L Castle
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah, 84602, USA.
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11
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Li G, Wu L, Lv G, Liu H, Fu Q, Zhang X, Tang Z. Alkyl transfer from C–C cleavage: replacing the nitro group of nitro-olefins. Chem Commun (Camb) 2014; 50:6246-8. [DOI: 10.1039/c4cc01119h] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogenation is only the beginning: alkyl groups are mildly transferred from alkyl substituted Hantzsch esters to replace the nitro groups of nitro olefins to providetrans-olefins in moderate to excellent yields.
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Affiliation(s)
- Guangxun Li
- Natural Products Research Center
- Chengdu Institution of Biology
- Chinese Academy of Science
- Chengdu, China
| | - Lei Wu
- Natural Products Research Center
- Chengdu Institution of Biology
- Chinese Academy of Science
- Chengdu, China
| | - Gang Lv
- Natural Products Research Center
- Chengdu Institution of Biology
- Chinese Academy of Science
- Chengdu, China
| | - Hongxin Liu
- Natural Products Research Center
- Chengdu Institution of Biology
- Chinese Academy of Science
- Chengdu, China
| | - Qingquan Fu
- Natural Products Research Center
- Chengdu Institution of Biology
- Chinese Academy of Science
- Chengdu, China
| | - Xiaomei Zhang
- Chengdu Institute of Organic Chemistry
- Chinese Academy of Sciences
- Chengdu, China
| | - Zhuo Tang
- Natural Products Research Center
- Chengdu Institution of Biology
- Chinese Academy of Science
- Chengdu, China
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12
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Lorenzo P, Aurrecoechea JM, de Lera AR, Álvarez R. Palladium-Catalyzed Diorganozinc Conjugate Additions to Enones: Preparative and Computational Studies. European J Org Chem 2013. [DOI: 10.1002/ejoc.201201519] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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13
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Hashizume S, Oisaki K, Kanai M. Functional‐Group‐Tolerant Catalytic Migratory Oxidative Coupling of Nitrones. Chem Asian J 2012; 7:2600-6. [DOI: 10.1002/asia.201200359] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Indexed: 11/11/2022]
Affiliation(s)
- Shogo Hashizume
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo‐ku, Tokyo 113‐0033 (Japan), Fax: (+81) 3‐5841‐5206
- Kanai Life Science Catalysis Project, ERATO (Japan) Science and Technology Agency (JST), Hongo, Bunkyo‐ku, Tokyo 113‐0033 (Japan)
| | - Kounosuke Oisaki
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo‐ku, Tokyo 113‐0033 (Japan), Fax: (+81) 3‐5841‐5206
- Kanai Life Science Catalysis Project, ERATO (Japan) Science and Technology Agency (JST), Hongo, Bunkyo‐ku, Tokyo 113‐0033 (Japan)
| | - Motomu Kanai
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo‐ku, Tokyo 113‐0033 (Japan), Fax: (+81) 3‐5841‐5206
- Kanai Life Science Catalysis Project, ERATO (Japan) Science and Technology Agency (JST), Hongo, Bunkyo‐ku, Tokyo 113‐0033 (Japan)
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14
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Yamada KI, Konishi T, Nakano M, Fujii S, Cadou R, Yamamoto Y, Tomioka K. Radical One-Pot α,β-Dual and β-Mono-Oxymethylation of Alkylidenemalonate. J Org Chem 2012; 77:5775-80. [DOI: 10.1021/jo300944f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Ken-ichi Yamada
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Yoshida, Sakyo,
Kyoto 606-8501, Japan
| | - Takehito Konishi
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Yoshida, Sakyo,
Kyoto 606-8501, Japan
| | - Mayu Nakano
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Yoshida, Sakyo,
Kyoto 606-8501, Japan
| | - Shintaro Fujii
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Yoshida, Sakyo,
Kyoto 606-8501, Japan
| | - Romain Cadou
- Graduate School of Pharmaceutical
Sciences, Kyoto University, Yoshida, Sakyo,
Kyoto 606-8501, Japan
| | - Yasutomo Yamamoto
- Faculty
of Pharmaceutical Sciences, Doshisha Women’s College of Liberal Arts, Kodo,
Kyotanabe 610-0395, Japan
| | - Kiyoshi Tomioka
- Faculty
of Pharmaceutical Sciences, Doshisha Women’s College of Liberal Arts, Kodo,
Kyotanabe 610-0395, Japan
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15
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Maury J, Mouysset D, Feray L, Marque SRA, Siri D, Bertrand MP. Aminomethylation of Michael acceptors: complementary radical and polar approaches mediated by dialkylzincs. Chemistry 2012; 18:3241-7. [PMID: 22328494 DOI: 10.1002/chem.201102366] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 11/14/2011] [Indexed: 11/10/2022]
Abstract
Phtalimidomethyl iodide and substituted maleimidomethyl iodide were used as radical precursors in dialkylzinc-mediated radical addition to diethyl fumarate. The reactions led stereoselectively to functionalized pyrrolizidines. The radical mechanism was supported by spin-trapping experiments and rationalized by theoretical calculations. Radical additions, on the one hand, and carbozincation followed by transmetalation with copper(I), on the other, were shown to be complementary methods to achieve the formal aminomethylation of activated unsaturated compounds.
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Affiliation(s)
- Julien Maury
- Institut de Chimie Radicalaire, UMR 7273, Faculté des Sciences et Techniques de Saint-Jérôme, Avenue Normandie-Niemen, Aix-Marseille Université, 13397 Marseille Cedex 20, France
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16
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Hashizume S, Oisaki K, Kanai M. Catalytic migratory oxidative coupling of nitrones through an outer-sphere C(sp3)-H activation process. CHEM REC 2011; 11:236-41. [PMID: 21898780 DOI: 10.1002/tcr.201100024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Indexed: 11/08/2022]
Abstract
Outer-sphere redox catalysis is key to efficient C-H activation, which has attracted increased interest in organic chemistry. In this account, we describe a Cu(I) -catalyzed oxidative coupling between nitrones and various ethers or amines as an example. Predictable site-selective C-C bond formation was achieved through activation of the C-H bonds in each coupling partner and the migration of a C-N double bond. Mechanistic studies strongly suggested that the reaction proceeded via an oxonium/iminium cation species as the key intermediate. The mechanistic information allows for future extension of outer-sphere redox catalysis.
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Affiliation(s)
- Shogo Hashizume
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1, Hongo, Tokyo 113-0033, Japan
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17
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Zimmerman JR, Manpadi M, Spatney R, Baker A. Diastereoselective Tin-Free Tandem Radical Additions to 3-Formylchromones. J Org Chem 2011; 76:8076-81. [DOI: 10.1021/jo201350w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jake R. Zimmerman
- Department of Chemistry and Biochemistry, Ohio Northern University, Ada, Ohio 45810, United States
| | - Madhuri Manpadi
- Department of Chemistry and Biochemistry, Ohio Northern University, Ada, Ohio 45810, United States
| | - Russell Spatney
- Department of Chemistry and Biochemistry, Ohio Northern University, Ada, Ohio 45810, United States
| | - Aaron Baker
- Department of Chemistry and Biochemistry, Ohio Northern University, Ada, Ohio 45810, United States
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18
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Hashizume S, Oisaki K, Kanai M. Catalytic migratory oxidative coupling of nitrones. Org Lett 2011; 13:4288-91. [PMID: 21766802 DOI: 10.1021/ol201629n] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A Cu(I)-catalyzed migratory oxidative coupling between nitrones and heterocycles or a methylamine is described. Selective C-C bond-formation proceeds through cleavage of two C(sp(3))-H bonds concomitant with C═N double bond-migration. The reaction provides an alternating nitrone moiety, allowing for further synthetically useful transformations. Radical clock studies suggest that the nucleophilic addition of nitrones to an oxidatively generated carbocation is a key step.
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Affiliation(s)
- Shogo Hashizume
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1, Hongo, Tokyo 113-0033, Japan
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19
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Houllier N, Lasne MC, Bureau R, Lestage P, Rouden J. Synthesis of a cytisine/epibatidine hybrid: a radical approach. Tetrahedron 2010. [DOI: 10.1016/j.tet.2010.09.079] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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20
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Li F, Tartakoff SS, Castle SL. Enantioselective total synthesis of (-)-acutumine. J Org Chem 2010; 74:9082-93. [PMID: 19904909 DOI: 10.1021/jo902006q] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An account of the total synthesis of the tetracyclic alkaloid (-)-acutumine is presented. A first-generation approach to the spirocyclic subunit was unsuccessful as a result of incorrect regioselectivity in a radical cyclization. However, this work spawned a second-generation strategy in which the spirocycle was fashioned via a radical-polar crossover reaction. This process merged an intramolecular radical conjugate addition with an enolate hydroxylation and created two stereocenters with excellent diastereoselectivity. The reaction was promoted by irradiation with a sunlamp, and a ditin reagent was required for aryl radical formation. These facts suggest that the substrate may function as a sensitizer, thereby facilitating homolytic cleavage of the ditin reagent. The propellane motif of the target was then installed via annulation of a pyrrolidine ring onto the spirocycle. The sequence of reactions used included a phenolic oxidation, an asymmetric ketone allylation mediated by Nakamura's chiral allylzinc reagent, an anionic oxy-Cope rearrangement, a one-pot ozonolysis-reductive amination, and a Lewis acid promoted cyclization of an amine onto an alpha,beta-unsaturated dimethyl ketal. Further studies of the asymmetric ketone allylation demonstrated the ability of the Nakamura reagent to function well in a mismatched situation. A TiCl(4)-catalyzed regioselective methyl enol etherification of a 1,3-diketone completed the synthesis.
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Affiliation(s)
- Fang Li
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA
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21
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Synthesis of (S)-(+)-tylophorine and its seco analogues using free radical reaction. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/s11426-009-0183-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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22
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Abstract
A new radical-polar crossover reaction was developed that consists of intramolecular conjugate addition of an aryl radical followed by enolate formation and hydroxylation. A C-C bond, a C-O bond, and two congested stereocenters are created in the process. The product is obtained as a single isomer. The method was used to synthesize the spirocyclic subunit of the alkaloid acutumine.
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Affiliation(s)
- Fang Li
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA
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Bazin S, Feray L, Vanthuyne N, Siri D, Bertrand MP. α,β-Unsaturated diesters: radical acceptors in dialkylzinc-mediated tandem radical addition/aldol condensation. A straightforward synthesis of rac-nephrosteranic acid. Tetrahedron 2007. [DOI: 10.1016/j.tet.2006.10.049] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Tu Z, Lin C, Jang Y, Jang YJ, Ko S, Fang H, Liu JT, Yao CF. One-pot synthesis of malononitriles by free radical reactions of ylidenemalononitrile with Et3B and iodoalkane in a water–ether biphase medium. Tetrahedron Lett 2006. [DOI: 10.1016/j.tetlet.2006.06.061] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Dondi D, Cardarelli AM, Fagnoni M, Albini A. Photomediated synthesis of β-alkylketones from cycloalkanes. Tetrahedron 2006. [DOI: 10.1016/j.tet.2006.03.028] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Black PJ, Cami-Kobeci G, Edwards MG, Slatford PA, Whittlesey MK, Williams JMJ. Borrowing hydrogen: iridium-catalysed reactions for the formation of C–C bonds from alcohols. Org Biomol Chem 2006; 4:116-25. [PMID: 16358005 DOI: 10.1039/b511053j] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Alcohols have been employed as substrates for C-C bond-forming reactions which involve initial activation by the temporary removal of hydrogen to form an aldehyde. The intermediate aldehyde is converted into an alkene via a Horner-Wadsworth-Emmons reaction, nitroaldol and aldol reactions. The 'borrowed hydrogen' is then returned to the alkene to form a C-C bond.
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Affiliation(s)
- Phillip J Black
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
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Free radical-promoted conjugate addition of activated bromo compounds using titanocene(III) chloride as the radical initiator. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.07.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Okano T, Chokai M, Hiraishi M, Yoshizawa M, Kusukawa T, Fujita M. Phenyl trifluorovinyl sulfide: a radical acceptor for preparation of gem-difluoromethylene compounds. Tetrahedron 2004. [DOI: 10.1016/j.tet.2004.03.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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