1
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Yamaguchi E, Murai M, Itoh A. Halogen-Bonding-Enabled Photoinduced Atom Transfer Radical Addition/Cyclization Reaction Leading to Tricyclic Heterocycles. J Org Chem 2024; 89:6555-6563. [PMID: 38657225 DOI: 10.1021/acs.joc.4c00204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Atom transfer radical addition (ATRA) reactions are crucial for the dual functionalization of unsaturated hydrocarbons. Radical generation, pivotal in ATRA, has seen advancements from thermal to photochemical methods. Recent focus on halogen-bonding-based radical generation, including our group's innovative photochemical approach, offers cost-effective alternatives to transition-metal-dependent photocatalysts. This eliminates the need for high-energy UV light, enhancing the efficiency with noncovalent interactions.
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Affiliation(s)
- Eiji Yamaguchi
- Gifu Pharmaceutical University, 1-25-4, Daigaku-Nishi, Gifu 501-1196, Japan
- Center for One Medicine Innovative Translational Research (COMIT), Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Masanobu Murai
- Gifu Pharmaceutical University, 1-25-4, Daigaku-Nishi, Gifu 501-1196, Japan
| | - Akichika Itoh
- Gifu Pharmaceutical University, 1-25-4, Daigaku-Nishi, Gifu 501-1196, Japan
- Center for One Medicine Innovative Translational Research (COMIT), Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
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2
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Zhao Y, Li L, Zang J, Young DJ, Ren ZG, Li HY, Yu L, Bian GQ, Li HX. Modulating β-Keto-enamine-Based Covalent Organic Frameworks for Photocatalytic Atom-Transfer Radical Addition Reaction. Chemistry 2024; 30:e202400377. [PMID: 38403857 DOI: 10.1002/chem.202400377] [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: 01/29/2024] [Revised: 02/19/2024] [Accepted: 02/20/2024] [Indexed: 02/27/2024]
Abstract
The atom-transfer radical addition (ATRA) reaction simultaneously forges carbon-carbon and carbon-halogen bonds. However, frequently-used photosensitizers such as precious transition metal complexes, or organic dyes have limitations in terms of their potential toxicity and recyclability. Three β-ketoenamine-linked covalent organic frameworks (COFs) from 1,3,5-triformylphloroglucinol and 1,4-phenylenediamines with variable transient photocurrent and photocatalytic activity have been prepared. A COF bearing electron-deficient Cl atoms displayed the highest photocatalytic activity toward the ATRA reaction of polyhalogenated alkanes to give halogenated olefins under visible light at room temperature. This heterogeneous photocatalyst exhibited good functional group tolerance and could be recycled without significant loss of activity.
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Affiliation(s)
- Yuting Zhao
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Lei Li
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Jiyuan Zang
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - David J Young
- Glasgow College, UESTC, University of Electronic Science and Technology of China, Chengdu, 611731, P. R. China
| | - Zhi-Gang Ren
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Hai-Yan Li
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Lei Yu
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Guo-Qing Bian
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
| | - Hong-Xi Li
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, P. R. China
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3
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Rrapi M, Batsika CS, Nikitas NF, Tappin NDC, Triandafillidi I, Renaud P, Kokotos CG. Photochemical Synthesis of Lactones, Cyclopropanes and ATRA Products: Revealing the Role of Sodium Ascorbate. Chemistry 2024; 30:e202400253. [PMID: 38324672 DOI: 10.1002/chem.202400253] [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: 01/28/2024] [Revised: 02/06/2024] [Accepted: 02/06/2024] [Indexed: 02/09/2024]
Abstract
Light-mediated processes have received significant attention, since they have re-surfaced unconventional reactivity platforms, complementary to conventional polar chemistry. γ-Lactones and cyclopropanes are prevalent moieties, found in numerous natural products and pharmaceuticals. Among various methods for their synthesis, light-mediated protocols are coming to the spotlight, although these are contingent upon the use of photoorgano- or metal-based catalysts. Herein, we introduce a novel photochemical activation of iodo-reagents via the use of cheap sodium ascorbate or ascorbic acid to enable their homolytic scission and addition onto double bonds. The developed protocol was applied successfully to the formal [3+2] cycloaddition for the synthesis of γ-lactones, traditional atom transfer radical addition (ATRA) reactions and the one-pot two-step conversion of alkenes to cyclopropanes. In all cases, the desired products were obtained in good to high yields, while the reaction mechanism was thoroughly investigated. Depending on the nature of the iodo-reagent, a halogen or a hydrogen-bonded complex is formed, which initiates the process.
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Affiliation(s)
- Marie Rrapi
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 15771, Greece
| | - Charikleia S Batsika
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 15771, Greece
| | - Nikolaos F Nikitas
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 15771, Greece
- Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland
| | - Nicholas D C Tappin
- Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland
| | - Ierasia Triandafillidi
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 15771, Greece
| | - Philippe Renaud
- Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland
| | - Christoforos G Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 15771, Greece
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4
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Jiang Z, You K, Wu H, Xu M, Wang T, Luo J. Photochemical Halogen-Bonding Promoted Synthesis of Vinyl Sulfones via Vinyl and Sulfonyl Radicals. Org Lett 2024; 26:636-641. [PMID: 38273796 DOI: 10.1021/acs.orglett.3c03958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2024]
Abstract
A photochemical halogen-bonding-assisted synthesis of vinyl sulfones via radical-radical cross-coupling of vinyl bromines and sodium sulfinates is developed. This methodology offers a facile and efficient approach to various vinyl sulfones with excellent functional group tolerance under metal-, photocatalyst-, base-, and oxidant-free conditions. The reaction is also applicable for the late-stage functionalization of drug molecules and the hectogram scale. Moreover, instead of sodium sulfites being prepared, these reactions could also be conducted using sulfonyl chlorides in a one-pot method.
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Affiliation(s)
- Zhou Jiang
- Jiangxi Province Key Laboratory of Chemical Biology, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, P. R. China
| | - Ke You
- Jiangxi Province Key Laboratory of Chemical Biology, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, P. R. China
| | - Haibo Wu
- Jiangxi Province Key Laboratory of Chemical Biology, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, P. R. China
| | - Mengyu Xu
- Jiangxi Province Key Laboratory of Chemical Biology, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, P. R. China
| | - Tao Wang
- Jiangxi Province Key Laboratory of Chemical Biology, College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, P. R. China
| | - Jin Luo
- Analytical and Testing Center, Jiangxi Normal University, Nanchang, Jiangxi 330022, P. R. China
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5
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Zhang FP, Wang RH, Li JF, Chen H, Hari Babu M, Ye M. Intermolecular Carbophosphination of Alkynes with Phosphole Oxides via Ni-Al Bimetal-Catalyzed C-P Bond Activation. Angew Chem Int Ed Engl 2023; 62:e202314701. [PMID: 37846814 DOI: 10.1002/anie.202314701] [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: 09/30/2023] [Revised: 10/15/2023] [Accepted: 10/17/2023] [Indexed: 10/18/2023]
Abstract
Intermolecular carbophosphination reaction of alkynes or alkenes with unreactive C-P bonds remains an elusive challenge. Herein, we used a Ni-Al bimetallic catalyst to realize an intermolecular carbophosphination reaction of alkynes with 5-membered phosphole oxides, providing a series of 7-membered phosphepines in up to 94 % yield.
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Affiliation(s)
- Feng-Ping Zhang
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Haihe Laboratory of Sustainable Chemical Transformations, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, China
| | - Rong-Hua Wang
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Haihe Laboratory of Sustainable Chemical Transformations, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, China
| | - Jiang-Fei Li
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Haihe Laboratory of Sustainable Chemical Transformations, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, China
| | - Hao Chen
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Haihe Laboratory of Sustainable Chemical Transformations, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, China
| | - Madala Hari Babu
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Haihe Laboratory of Sustainable Chemical Transformations, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, China
| | - Mengchun Ye
- State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Haihe Laboratory of Sustainable Chemical Transformations, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, China
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6
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Jazani AM, Schild DJ, Sobieski J, Hu X, Matyjaszewski K. Visible Light-ATRP Driven by Tris(2-Pyridylmethyl)Amine (TPMA) Impurities in the Open Air. Macromol Rapid Commun 2023; 44:e2200855. [PMID: 36471106 DOI: 10.1002/marc.202200855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 11/29/2022] [Indexed: 12/12/2022]
Abstract
Atom transfer radical polymerization (ATRP) of oligo(ethylene oxide) monomethyl ether methacrylate (OEOMA500 ) in water is enabled using CuBr2 with tris(2-pyridylmethyl)amine (TPMA) as a ligand under blue or green-light irradiation without requiring any additional reagent, such as a photo-reductant, or the need for prior deoxygenation. Polymers with low dispersity (Đ = 1.18-1.25) are synthesized at high conversion (>95%) using TPMA from three different suppliers, while no polymerization occurred with TPMA is synthesized and purified in the laboratory. Based on spectroscopic studies, it is proposed that TPMA impurities (i.e., imine and nitrone dipyridine), which absorb blue and green light, can act as photosensitive co-catalyst(s) in a light region where neither pure TPMA nor [(TPMA)CuBr]+ absorbs light.
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Affiliation(s)
- Arman Moini Jazani
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Dirk J Schild
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Julian Sobieski
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
| | - Xiaolei Hu
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA
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7
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Yang X, Zhou J, Wu S, Yu W. Copper-mediated bromine atom transfer radical cyclisation of unactivated alkyl bromides. Chem Commun (Camb) 2023. [PMID: 37401443 DOI: 10.1039/d3cc02430j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2023]
Abstract
The atom transfer radical cyclisation of unactivated alkyl bromides was realized by using a catalytic system of CuBr and Me6-TREN. This protocol is applicable to the preparation of five-membered rings from unsaturated primary and secondary bromides.
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Affiliation(s)
- Xue Yang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China.
| | - Jianlin Zhou
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China.
| | - Shuoren Wu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China.
| | - Wei Yu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China.
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8
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Piedra HF, Valdés C, Plaza M. Shining light on halogen-bonding complexes: a catalyst-free activation mode of carbon-halogen bonds for the generation of carbon-centered radicals. Chem Sci 2023; 14:5545-5568. [PMID: 37265729 PMCID: PMC10231334 DOI: 10.1039/d3sc01724a] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 05/03/2023] [Indexed: 06/03/2023] Open
Abstract
The discovery of new activation modes for the creation of carbon-centered radicals is a task of great interest in organic chemistry. Classical activation modes for the generation of highly reactive radical carbon-centered intermediates typically relied on thermal activation of radical initiators or irradiation with unsafe energetic UV light of adequate reaction precursors. In recent years, photoredox chemistry has emerged as a leading strategy towards the catalytic generation of C-centered radicals, which enabled their participation in novel synthetic organic transformations which is otherwise very challenging or even impossible to take place. As an alternative to these activation modes for the generation of C-centered radicals, the pursuit of greener, visible-light initiated reactions that do not necessitate a photoredox/metal catalyst has recently caught the attention of chemists. In this review, we covered recent transformations, which rely on photoactivation with low-energy light of a class of EDA complexes, known as halogen-bonding adducts, for the creation of C-centered radicals.
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Affiliation(s)
- Helena F Piedra
- Departamento de Química Orgánica e Inorgánica, Instituto Universitario de Química Organometálica "Enrique Moles" and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Oviedo Julián Clavería 8 33006 Oviedo Spain
| | - Carlos Valdés
- Departamento de Química Orgánica e Inorgánica, Instituto Universitario de Química Organometálica "Enrique Moles" and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Oviedo Julián Clavería 8 33006 Oviedo Spain
| | - Manuel Plaza
- Departamento de Química Orgánica e Inorgánica, Instituto Universitario de Química Organometálica "Enrique Moles" and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Oviedo Julián Clavería 8 33006 Oviedo Spain
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9
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Matsuo K, Yamaguchi E, Itoh A. Halogen-Bonding-Promoted Photoinduced C-X Borylation of Aryl Halide Using Phenol Derivatives. J Org Chem 2023; 88:6176-6181. [PMID: 37083371 DOI: 10.1021/acs.joc.3c00201] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
Abstract
This study investigates the photoinduced C-X borylation reaction of aryl halides by forming a halogen-bonding (XB) complex using 2-naphthol as an XB acceptor. The method is chemoselective and broadly functional group tolerant and provides concise access to corresponding boronate esters. Mechanistic studies reveal that forming the XB complex between aryl halide and naphthol acts as an electron donor-acceptor complex to furnish aryl radicals through photoinduced electron transfer.
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Affiliation(s)
- Kazuki Matsuo
- Laboratory of Pharmaceuticals Synthetic, Gifu Pharmaceutical University 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
| | - Eiji Yamaguchi
- Laboratory of Pharmaceuticals Synthetic, Gifu Pharmaceutical University 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
| | - Akichika Itoh
- Laboratory of Pharmaceuticals Synthetic, Gifu Pharmaceutical University 1-25-4 Daigaku-nishi, Gifu 501-1196, Japan
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10
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Treacy SM, Vaz DR, Noman S, Tard C, Rovis T. Coupling of α-bromoamides and unactivated alkenes to form γ-lactams through EDA and photocatalysis. Chem Sci 2023; 14:1569-1574. [PMID: 36794189 PMCID: PMC9906710 DOI: 10.1039/d2sc05973h] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 01/15/2023] [Indexed: 01/22/2023] Open
Abstract
γ-Lactams are prevalent in small-molecule pharmaceuticals and provide useful precursors to highly substituted pyrrolidines. Despite numerous methods for the synthesis of this valuable motif, previous redox approaches to γ-lactam synthesis from α-haloamides and olefins require additional electron withdrawing functionality as well as N-aryl substitution to promote electrophilicity of the intermediate radical and prevent competitive O-nucleophilicity about the amide. Using α-bromo imides and α-olefins, our strategy enables the synthesis of monosubstituted protected γ-lactams in a formal [3 + 2] fashion. These species are poised for further derivatization into more complex heterocyclic scaffolds, complementing existing methods. C-Br bond scission occurs through two complementary approaches, the formation of an electron donor-acceptor complex between the bromoimide and a nitrogenous base which undergoes photoinduced electron transfer, or triplet sensitization with photocatalyst, to furnish an electrophilic carbon-centered radical. The addition of Lewis acids allows for further increased electrophilicity of the intermediate carbon-centered radical, enabling tertiary substituted α-Br-imides to be used as coupling partners as well as internal olefins.
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Affiliation(s)
- Sean M. Treacy
- Department of Chemistry, Columbia UniversityNew YorkNY10027USA
| | - Daniel R. Vaz
- Department of Chemistry, Columbia UniversityNew YorkNY10027USA
| | - Syed Noman
- Laboratoire de Chimie Moléculaire (LCM), CNRS, École Polytechnique, Institut Polytechnique de Paris91120 PalaiseauFrance
| | - Cédric Tard
- Laboratoire de Chimie Moléculaire (LCM), CNRS, École Polytechnique, Institut Polytechnique de Paris91120 PalaiseauFrance
| | - Tomislav Rovis
- Department of Chemistry, Columbia University New York NY 10027 USA
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11
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Tang WX, Chen KQ, Sun DQ, Chen XY. Photoinduced halogen-bonding enabled synthesis of oxindoles and isoindolinones from aryl iodides. Org Biomol Chem 2023; 21:715-718. [PMID: 36412116 DOI: 10.1039/d2ob01818g] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We report the use of halogen bonding (XB) for the generation of aryl radicals from aryl halides under blue light irradiation and applied it in radical generation/1,5-hydrogen-atom transfer/radical cyclization cascade reactions for the synthesis of oxindoles and isoindolinones. On the basis of experimental studies, we propose that DBU can serve as a suitable XB acceptor with aryl halides for the formation of a photoactive electron donor and acceptor complex.
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Affiliation(s)
- Wen-Xin Tang
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, P. R. China.
| | - Kun-Quan Chen
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
| | - De-Qun Sun
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, P. R. China.
| | - Xiang-Yu Chen
- School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing 100049, P. R. China. .,Binzhou Institute of Technology, Weiqiao-UCAS Science and Technology Park, Binzhou, Shandong Province 256606, P. R. China
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12
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Yan CY, Wu ZW, He XY, Ma YH, Peng XR, Wang L, Yang QQ. Visible-Light-Induced Tandem Radical Brominative Addition/Cyclization of Activated Alkynes with CBr 4 for the Synthesis of 3-Bromocoumarins. J Org Chem 2023; 88:647-652. [PMID: 36480338 DOI: 10.1021/acs.joc.2c01721] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A visible-light-induced tandem radical brominative addition/spiro-cyclization/1,2-ester migration of activated alkynes with CBr4 is developed. This protocol features good functional group tolerance, operational simplicity, and mild reaction conditions without the use of catalysts and external additives, providing easy access to valuable 3-bromocoumarins in generally high yields.
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Affiliation(s)
- Chen-Yang Yan
- College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, 8 Daxue Road, Yichang, Hubei 443002, P. R. China
| | - Zheng-Wei Wu
- College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, 8 Daxue Road, Yichang, Hubei 443002, P. R. China
| | - Xiao-Yu He
- College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, 8 Daxue Road, Yichang, Hubei 443002, P. R. China
| | - Yu-Hong Ma
- College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, 8 Daxue Road, Yichang, Hubei 443002, P. R. China
| | - Xiao-Rong Peng
- GongAn County People's Hospital, No. 119, Chanling Avenue, Douhudi Town, Gongan County, Jingzhou, Hubei 434300, P. R. China
| | - Long Wang
- College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, 8 Daxue Road, Yichang, Hubei 443002, P. R. China.,Hubei Three Gorges Laboratory, Yichang, Hubei 443007, P. R. China
| | - Qing-Qing Yang
- College of Materials and Chemical Engineering, Key Laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials, China Three Gorges University, 8 Daxue Road, Yichang, Hubei 443002, P. R. China.,Hubei Three Gorges Laboratory, Yichang, Hubei 443007, P. R. China
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13
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Yamaguchi E. [Development of Molecular Transformation Reactions Using Visible Light and Main Group Elements]. YAKUGAKU ZASSHI 2023; 143:693-699. [PMID: 37661434 DOI: 10.1248/yakushi.23-00091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Owing to their ability to induce excitation of specific molecular orbitals or initiate chemical reactions, photochemical reactions have the potential to be more effective at selectively activating target molecules than thermal reactions. The thermal reactions transfer thermal energy to activate molecules, which often leads to the activation of multiple molecular species, including undesired ones, resulting in non-selectivity. This nonselectivity may result in undesirable side reactions or decrease reaction efficiency. Additionally, photochemical reactions can induce selective activation by absorbing specific wavelengths of light. However, visible light-driven photocatalytic reactions typically require expensive transition metal catalysts or organic dyes, leaving plenty of room for improvement. To address the aforementioned issues, the photochemical properties of the main group elements, such as halogens, were optimized and methodologies for visible light-induced reactions were developed. Activation of molecular halogen, halogen-carbon bonds, and halogen bonding interactions were independently investigated and various methodologies were reported. These developed reactions are excellent methodologies that use inexpensive raw materials and are thus predicted to contribute significantly toward sustainability.
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Affiliation(s)
- Eiji Yamaguchi
- Department of Pharmacy, Gifu Pharmaceutical University
- Center for One Medicine Innovative Translational Research, Gifu University
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14
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Wen T, Liang B, Liang J, Wang D, Shi J, Xu S, Zhu W, Chen X, Zhu Z. Copper-Promoted N-Alkylation and Bromination of Arylamines/Indazoles Using Alkyl Bromides as Reagents for Difunctionalization. J Org Chem 2022; 87:12214-12224. [PMID: 36053202 DOI: 10.1021/acs.joc.2c01356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Practical copper-promoted N-alkylation and bromination of arylamines/indazoles with alkyl bromides are described; the N-alkylation-C-4-bromination and N-dialkylation-C-4-bromination of arylamines, and N-alkylation-C-3-bromination of indazoles, with alkyl bromides have been analyzed. The full use of alkyl bromides as alkylating and brominating building blocks without atom wastage, indicating excellent atom and step economy, has been highlighted. Eco-friendly oxygen and water are the reaction oxidant and byproduct, respectively.
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Affiliation(s)
- Tingting Wen
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Baihui Liang
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Jiacheng Liang
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Dongyi Wang
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Jianyi Shi
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Shengting Xu
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Weidong Zhu
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Xiuwen Chen
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
| | - Zhongzhi Zhu
- School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
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15
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Kato N, Nanjo T, Takemoto Y. A Pyridine-Based Donor–Acceptor Molecule: A Highly Reactive Organophotocatalyst That Enables the Reductive Cleavage of C–Br Bonds through Halogen Bonding. ACS Catal 2022. [DOI: 10.1021/acscatal.2c02067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Natsuki Kato
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Takeshi Nanjo
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Yoshiji Takemoto
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
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16
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Liautard V, Delgado M, Colin B, Chabaud L, Michaud G, Pucheault M. In situ generation of radical initiators using amine-borane complexes for carbohalogenation of alkenes. Chem Commun (Camb) 2022; 58:2124-2127. [DOI: 10.1039/d1cc06390a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Atom transfer radical addition of alkyl halides to alkenes was developed using a low amount of a stable initiator, amine borane complexes.
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Affiliation(s)
- Virginie Liautard
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400 Talence, France
| | - Marine Delgado
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400 Talence, France
- BOSTIK, Smart Technology Centre, ZAC du bois de Plaisance, 101, rue du Champ Cailloux 60280, Venette, France
| | - Boris Colin
- BOSTIK, Smart Technology Centre, ZAC du bois de Plaisance, 101, rue du Champ Cailloux 60280, Venette, France
| | - Laurent Chabaud
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400 Talence, France
| | - Guillaume Michaud
- BOSTIK, Smart Technology Centre, ZAC du bois de Plaisance, 101, rue du Champ Cailloux 60280, Venette, France
| | - Mathieu Pucheault
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400 Talence, France
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17
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Tasnim T, Ryan C, Christensen ML, Fennell CJ, Pitre SP. Radical Perfluoroalkylation Enabled by a Catalytically Generated Halogen Bonding Complex and Visible Light Irradiation. Org Lett 2021; 24:446-450. [PMID: 34914870 DOI: 10.1021/acs.orglett.1c04139] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Exploiting charge-transfer complexes in visible light-promoted single-electron redox reactions is a promising route for opening novel synthetic pathways, and catalytic approaches to complex formation are critical for facilitating this chemistry. This report describes the use of a substituted hydroquinone catalyst to promote radical perfluoroalkylation reactions. Mechanistic studies indicate that the reaction is initiated through formation of a visible light-absorbing halogen bonding complex between the hydroquinone catalyst and the perfluoroalkyl halide radical precursor.
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Affiliation(s)
- Tarannum Tasnim
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, Oklahoma 74078, United States
| | - Calvin Ryan
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, Oklahoma 74078, United States
| | - Miranda L Christensen
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, Oklahoma 74078, United States
| | - Christopher J Fennell
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, Oklahoma 74078, United States
| | - Spencer P Pitre
- Department of Chemistry, Oklahoma State University, 107 Physical Sciences, Stillwater, Oklahoma 74078, United States
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18
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Zeng X, Xu Y, Liu J, Deng Y. Access to gem-Dibromoenones Enabled by Carbon-Centered Radical Addition to Terminal Alkynes in Water Solution. Org Lett 2021; 23:9058-9062. [PMID: 34766780 DOI: 10.1021/acs.orglett.1c03305] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We herein report a novel and more practical approach to prepare gem-dibromoenones from terminal alkynes, tetrabromomethane (CBr4), and water in a single step. Mechanistic studies reveal that the generation of a tribromomethyl radical with the assistance of a persulfate salt (K2S2O8) is essential to this transformation. The reaction features readily available chemicals, a broad substrate scope, a green solvent, and mild reaction conditions, providing an efficient alternative for construction of halogen-substituted enones.
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Affiliation(s)
- Xianghua Zeng
- College of Biological, Chemical Science and Engineering, Jiaxing University, 118 Jiahang Road, Jiaxing 314001, P.R. China
| | - Yuhai Xu
- College of Biological, Chemical Science and Engineering, Jiaxing University, 118 Jiahang Road, Jiaxing 314001, P.R. China
| | - Jiawei Liu
- College of Biological, Chemical Science and Engineering, Jiaxing University, 118 Jiahang Road, Jiaxing 314001, P.R. China
| | - Yuanyuan Deng
- College of Biological, Chemical Science and Engineering, Jiaxing University, 118 Jiahang Road, Jiaxing 314001, P.R. China
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19
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Matsuo K, Yoshitake T, Yamaguchi E, Itoh A. Photoinduced Atom Transfer Radical Addition/Cyclization Reaction between Alkynes or Alkenes with Unsaturated α-Halogenated Carbonyls. Molecules 2021; 26:molecules26226781. [PMID: 34833874 PMCID: PMC8618827 DOI: 10.3390/molecules26226781] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 11/03/2021] [Accepted: 11/07/2021] [Indexed: 11/16/2022] Open
Abstract
We have developed a photochemical ATRA/ATRC reaction that is mediated by halogen bonding interactions. This reaction is caused by the reaction of malonic acid ester derivatives containing bromine or iodine with unsaturated compounds such as alkenes and alkynes in the presence of diisopropylethylamine under visible light irradiation. As a result of various control experiments, it was found that the formation of complexes between amines and halogens by halogen-bonding interaction occurs in the reaction system, followed by the cleavage of the carbon-halogen bonds by visible light, resulting in the formation of carbon radicals. In this reaction, a variety of substrates can be used, and the products, cyclopentenes and cyclopentanes, were obtained by intermolecular addition and intramolecular cyclization.
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20
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Wang Y, Tu K, Cheng J, He E, Wang J, Zhang L, Cheng Z. Facile photochemical synthesis of main-chain-type semifluorinated alternating copolymers catalyzed by conventional amines or halide salts. Chem Commun (Camb) 2021; 57:11354-11357. [PMID: 34643625 DOI: 10.1039/d1cc04967d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
In this work, we report a much simpler and low-cost method to prepare main-chain-type semifluorinated alternating copolymers by the formation of a halogen bond (XB) complex between α,ω-diiodoperfluoroalkanes and amines/halide salts. It is interesting that the terminal iodine functional group of the polymer chains is easily lost in the amine-promoted system, while the loss can be significantly reduced by adding a small amount of water. Importantly, the system promoted by halide salts can ensure complete retention of the iodine functional group. Overall, the establishment of this method provides a new strategy for designing smart fluoropolymer materials in a green and environmentally friendly facile manner under irradiation with visible light at room temperature.
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Affiliation(s)
- Yuxue Wang
- Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
| | - Kai Tu
- Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
| | - Jiannan Cheng
- Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
| | - Enjie He
- Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
| | - Jinying Wang
- Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
| | - Lifen Zhang
- Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
| | - Zhenping Cheng
- Suzhou Key Laboratory of Macromolecular Design and Precision Synthesis, Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application, State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
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21
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Li JZ, Zhang WK, Ge GP, Zheng H, Wei WT. Recent progress in the radical α-C(sp 3)-H functionalization of ketones. Org Biomol Chem 2021; 19:7333-7347. [PMID: 34612358 DOI: 10.1039/d1ob01408k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The direct use structurally simple ketones as α-ketone radical sources for α-C(sp3)-H functionalization is a sustainable and powerful approach for constructing complex and multifunctional chemical scaffolds with diverse applications. The reactions of α-ketone radicals with alkenes, alkynes, enynes, imides, and imidazo[1,2-a]pyridines have broadened the structural diversity and complexity of ketones. Through chosen illustrative examples, we outline the recent progress in the development of methods that enable the radical α-C(sp3)-H functionalization of ketones, with an emphasis on radical initiation systems and possible mechanisms of the transformations. The application of these strategies is illustrated by the synthesis of several biologically active molecules and drug molecules. Further subdivision is based on substrate type and reaction type.
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Affiliation(s)
- Jiao-Zhe Li
- Key Laboratory of Advanced Mass Spectrometry and Molecular Analysis of Zhejiang Province, State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-products, School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang 315211, China.
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22
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Matsuo K, Kondo T, Yamaguchi E, Itoh A. Photoinduced Atom Transfer Radical Addition Reaction of Olefins with α-Bromo Carbonyls. Chem Pharm Bull (Tokyo) 2021; 69:796-801. [PMID: 34334524 DOI: 10.1248/cpb.c21-00360] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The irradiation of halogen-bonded complexes with light leads to the homolysis of carbon-halogen bonds and the formation of the corresponding carbon radical species. However, the only methodology reported for these halogen-bonding complexes is using CBr4 as the halogen-bond donor and its applicability is of great interest. In this study, the atom transfer radical addition (ATRA) reaction of olefins using bromomalonates as halogen-bonding donors was developed. Using 4-phenylpyridine as the halogen-bonding acceptor, the desired reaction proceeded well under external irradiation of 380 nm light to furnish the corresponding ATRA reaction product. The ATRA reaction was effective in generating the corresponding products for a variety of olefins. Furthermore, the ATRA reaction was applicable to bulky ketones, substrates, and malonate esters. The intermediates of the reaction were identified and a plausible reaction mechanism was proposed.
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Affiliation(s)
- Kazuki Matsuo
- Laboratory of Pharmaceutical Synthetic Chemistry, Gifu Pharmaceutical University
| | - Takemasa Kondo
- Laboratory of Pharmaceutical Synthetic Chemistry, Gifu Pharmaceutical University
| | - Eiji Yamaguchi
- Laboratory of Pharmaceutical Synthetic Chemistry, Gifu Pharmaceutical University
| | - Akichika Itoh
- Laboratory of Pharmaceutical Synthetic Chemistry, Gifu Pharmaceutical University
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23
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Zheng L, Cai L, Tao K, Xie Z, Lai Y, Guo W. Progress in Photoinduced Radical Reactions using Electron Donor‐Acceptor Complexes. ASIAN J ORG CHEM 2021. [DOI: 10.1002/ajoc.202100009] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Lvyin Zheng
- Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province Gannan Normal University Ganzhou 341000 P. R. China
| | - Liuhuan Cai
- Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province Gannan Normal University Ganzhou 341000 P. R. China
| | - Kailiang Tao
- Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province Gannan Normal University Ganzhou 341000 P. R. China
| | - Zhen Xie
- Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province Gannan Normal University Ganzhou 341000 P. R. China
| | - Yin‐Long Lai
- College of Chemistry and Civil Engineering Shaoguan University Shaoguan 512005 P. R. China
| | - Wei Guo
- Key Laboratory of Organo-Pharmaceutical Chemistry of Jiangxi Province Gannan Normal University Ganzhou 341000 P. R. China
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24
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Worp BA, Kosobokov MD, Dilman AD. Visible‐Light‐Promoted Reversible Sulfide/Iodide Exchange in Fluoroalkyl Sulfides Enabled by Electron Donor‐Acceptor Complex Formation. CHEMPHOTOCHEM 2021. [DOI: 10.1002/cptc.202100042] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Boris A. Worp
- N. D. Zelinsky Institute of Organic Chemistry 119991 Moscow Leninsky prosp. 47 Russian Federation
- Lomonosov Moscow State University Department of Chemistry 119991 Moscow Leninskie Gory 1–3 Russian Federation
| | - Mikhail D. Kosobokov
- N. D. Zelinsky Institute of Organic Chemistry 119991 Moscow Leninsky prosp. 47 Russian Federation
| | - Alexander D. Dilman
- N. D. Zelinsky Institute of Organic Chemistry 119991 Moscow Leninsky prosp. 47 Russian Federation
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25
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Steiner A, de Frutos O, Rincón JA, Mateos C, Williams JD, Kappe CO. N-Chloroamines as substrates for metal-free photochemical atom-transfer radical addition reactions in continuous flow. REACT CHEM ENG 2021. [DOI: 10.1039/d1re00429h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Photochemical ATRA reactions of N-chloroamines represent an efficient and green method of alkene functionalization. N-Chloroamine generation, purification and reaction in flow enables an efficient process, with a variety of irradiation wavelengths.
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Affiliation(s)
- Alexander Steiner
- Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, NAWI Graz, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Oscar de Frutos
- Centro de Investigación Lilly S.A., Avda. de la Industria 30, 28108 Alcobendas-Madrid, Spain
| | - Juan A. Rincón
- Centro de Investigación Lilly S.A., Avda. de la Industria 30, 28108 Alcobendas-Madrid, Spain
| | - Carlos Mateos
- Centro de Investigación Lilly S.A., Avda. de la Industria 30, 28108 Alcobendas-Madrid, Spain
| | - Jason D. Williams
- Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, NAWI Graz, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - C. Oliver Kappe
- Center for Continuous Flow Synthesis and Processing (CC FLOW), Research Center Pharmaceutical Engineering GmbH (RCPE), Inffeldgasse 13, 8010 Graz, Austria
- Institute of Chemistry, NAWI Graz, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
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