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Abstract
Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R1R2N-O•. The spin distribution over the nitroxide N and O atoms contributes to the thermodynamic stability of these radicals. The presence of bulky N-substituents R1 and R2 prevents nitroxide radical dimerization, ensuring their kinetic stability. Despite their reactivity toward various transient C radicals, some nitroxides can be easily stored under air at room temperature. Furthermore, nitroxides can be oxidized to oxoammonium salts (R1R2N═O+) or reduced to anions (R1R2N-O-), enabling them to act as valuable oxidants or reductants depending on their oxidation state. Therefore, they exhibit interesting reactivity across all three oxidation states. Due to these fascinating properties, nitroxides find extensive applications in diverse fields such as biochemistry, medicinal chemistry, materials science, and organic synthesis. This review focuses on the versatile applications of nitroxides in organic synthesis. For their use in other important fields, we will refer to several review articles. The introductory part provides a brief overview of the history of nitroxide chemistry. Subsequently, the key methods for preparing nitroxides are discussed, followed by an examination of their structural diversity and physical properties. The main portion of this review is dedicated to oxidation reactions, wherein parent nitroxides or their corresponding oxoammonium salts serve as active species. It will be demonstrated that various functional groups (such as alcohols, amines, enolates, and alkanes among others) can be efficiently oxidized. These oxidations can be carried out using nitroxides as catalysts in combination with various stoichiometric terminal oxidants. By reducing nitroxides to their corresponding anions, they become effective reducing reagents with intriguing applications in organic synthesis. Nitroxides possess the ability to selectively react with transient radicals, making them useful for terminating radical cascade reactions by forming alkoxyamines. Depending on their structure, alkoxyamines exhibit weak C-O bonds, allowing for the thermal generation of C radicals through reversible C-O bond cleavage. Such thermally generated C radicals can participate in various radical transformations, as discussed toward the end of this review. Furthermore, the application of this strategy in natural product synthesis will be presented.
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Affiliation(s)
- Dirk Leifert
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
| | - Armido Studer
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
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Kato T, Maruoka K. Selective functionalization of benzylic C-H bonds of two different benzylic ethers by bowl-shaped N-hydroxyimide derivatives as efficient organoradical catalysts. Chem Commun (Camb) 2021; 58:1021-1024. [PMID: 34951412 DOI: 10.1039/d1cc06425h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A highly efficient, site-selective benzylic C-H bond amination of two different benzylic ether substrates was described by using bowl-shaped N-hydroxyimide organoradical catalysts with diethyl azodicarboxylate. The synthetic utility of this approach is demonstrated by the subsequent transformation of the amination products into the corresponding aldehydes and alkylhydrazines.
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Affiliation(s)
- Terumasa Kato
- School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China.,Guangdong Provincial Key Laboratory of Plant Resources Biorefinery, Guangdong University of Technology, Guangzhou 510006, China.,Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo, Kyoto 606-8501, Japan.
| | - Keiji Maruoka
- School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China.,Guangdong Provincial Key Laboratory of Plant Resources Biorefinery, Guangdong University of Technology, Guangzhou 510006, China.,Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo, Kyoto 606-8501, Japan.
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LaMartina KB, Kuck HK, Oglesbee LS, Al-Odaini A, Boaz NC. Selective benzylic C-H monooxygenation mediated by iodine oxides. Beilstein J Org Chem 2019; 15:602-609. [PMID: 30931001 PMCID: PMC6423598 DOI: 10.3762/bjoc.15.55] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 02/19/2019] [Indexed: 12/30/2022] Open
Abstract
A method for the selective monooxdiation of secondary benzylic C–H bonds is described using an N-oxyl catalyst and a hypervalent iodine species as a terminal oxidant. Combinations of ammonium iodate and catalytic N-hydroxyphthalimide (NHPI) were shown to be effective in the selective oxidation of n-butylbenzene directly to 1-phenylbutyl acetate in high yield (86%). This method shows moderate substrate tolerance in the oxygenation of substrates containing secondary benzylic C–H bonds, yielding the corresponding benzylic acetates in good to moderate yield. Tertiary benzylic C–H bonds were shown to be unreactive under similar conditions, despite the weaker C–H bond. A preliminary mechanistic analysis suggests that this NHPI-iodate system is functioning by a radical-based mechanism where iodine generated in situ captures formed benzylic radicals. The benzylic iodide intermediate then solvolyzes to yield the product ester.
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Affiliation(s)
- Kelsey B LaMartina
- Department of Chemistry and Physics, North Central College, 30 N. Brainard Street, Naperville, IL 60540 USA
| | - Haley K Kuck
- Department of Chemistry and Physics, North Central College, 30 N. Brainard Street, Naperville, IL 60540 USA
| | - Linda S Oglesbee
- Department of Chemistry and Physics, North Central College, 30 N. Brainard Street, Naperville, IL 60540 USA
| | - Asma Al-Odaini
- Department of Chemistry and Physics, North Central College, 30 N. Brainard Street, Naperville, IL 60540 USA
| | - Nicholas C Boaz
- Department of Chemistry and Physics, North Central College, 30 N. Brainard Street, Naperville, IL 60540 USA.,Department of Chemistry, Frick Chemical Laboratory, Princeton University, Washington Road, Princeton, NJ 08544 USA.,Permanent address: Department of Chemistry, North Central College, 30 N. Brainard Street, Naperville, IL 60540 USA; phone: +1-630-637-5187
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Ni J, Ozawa J, Oisaki K, Kanai M. Directing activator-assisted regio- and oxidation state-selective aerobic oxidation of secondary C(sp(3))-H bonds in aliphatic alcohols. Org Biomol Chem 2018; 14:4378-81. [PMID: 27109464 DOI: 10.1039/c6ob00678g] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The regioselective conversion of an unactivated C(sp(3))-H bond of a methylene carbon (CH2) into a C-O single bond is an attractive reaction in organic synthesis. Herein, we present a strategy for a regio- and oxidation state-selective aerobic C-H oxidation based on an N-hydroxyamide-derived directing activator (DA), which is attached to a hydroxy group in alcohol substrates. The DA reacts with NOx species generated in situ from NaNO2, a Brønsted acid, and aerobic oxygen, and effectively generates an amidoxyl radical from the N-hydroxy moiety of the DA. Then, the amidoxyl radical promotes site-selective intramolecular C-H abstraction from methylenes with γ- (or δ-) selectivity. The thus-generated methylene radicals are trapped by molecular oxygen and NO. This process results in the predominant formation of nitrate esters as products, which suppresses undesired overoxidation. The products can be easily converted into alcohols after hydrogenolysis.
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Affiliation(s)
- Jizhi Ni
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan. and Japan Science Technology Agency (JST), ERATO Kanai Life Science Catalysis Project, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan
| | - Jun Ozawa
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan.
| | - Kounosuke Oisaki
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan.
| | - Motomu Kanai
- Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan. and Japan Science Technology Agency (JST), ERATO Kanai Life Science Catalysis Project, 7-3-1 Bunkyo-ku, Tokyo 113-0033, Japan
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Xu X, Sun J, Lin Y, Cheng J, Li P, Jiang X, Bai R, Xie Y. Iron-Nitrate-Catalyzed Oxidative Esterification of Aldehydes and Alcohols with N
-Hydroxyphthalimide: Efficient Synthesis of N
-Hydroxyimide Esters. European J Org Chem 2017. [DOI: 10.1002/ejoc.201701411] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Xiaohe Xu
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
| | - Jian Sun
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
| | - Yuyan Lin
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
| | - Jingya Cheng
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
| | - Pingping Li
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
| | - Xiaoying Jiang
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
| | - Renren Bai
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
| | - Yuanyuan Xie
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals; Zhejiang University of Technology; Hangzhou P. R. China
- College of Pharmaceutical Sciences; Zhejiang University of Technology; Hangzhou P. R. China
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Yasukawa N, Kanie T, Kuwata M, Monguchi Y, Sajiki H, Sawama Y. Palladium on Carbon-Catalyzed Benzylic Methoxylation for Synthesis of Mixed Acetals and Orthoesters. Chemistry 2017; 23:10974-10977. [DOI: 10.1002/chem.201702278] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Indexed: 12/18/2022]
Affiliation(s)
- Naoki Yasukawa
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Takafumi Kanie
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Marina Kuwata
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Yasunari Monguchi
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Hironao Sajiki
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
| | - Yoshinari Sawama
- Laboratory of Organic Chemistry; Gifu Pharmaceutical University; 1-25-4 Daigaku-nishi Gifu 501-1196 Japan
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Xu X, Sun J, Lin Y, Cheng J, Li P, Yan Y, Shuai Q, Xie Y. Copper nitrate-catalyzed oxidative coupling of unactivated C(sp3)–H bonds of ethers and alkanes with N-hydroxyphthalimide: synthesis of N-hydroxyimide esters. Org Biomol Chem 2017; 15:9875-9879. [DOI: 10.1039/c7ob02249b] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel oxygenative cross dehydrogenative coupling of ethers and alkanes with NHPI under a copper nitrate/oxygen catalytic system is described.
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Affiliation(s)
- Xiaohe Xu
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
| | - Jian Sun
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
| | - Yuyan Lin
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
| | - Jingya Cheng
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
| | - Pingping Li
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
| | - Yiyan Yan
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
| | - Qi Shuai
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
- College of Pharmaceutical Sciences
| | - Yuanyuan Xie
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals
- Zhejiang University of Technology
- Hangzhou
- PR China
- College of Pharmaceutical Sciences
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Hu Y, Chen L, Li B. NHPI/tert-butyl nitrite: A highly efficient metal-free catalytic system for aerobic oxidation of alcohols to carbonyl compounds using molecular oxygen as the terminal oxidant. CATAL COMMUN 2016. [DOI: 10.1016/j.catcom.2016.05.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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Majumdar B, Bhattacharya T, Sarma TK. Gold Nanoparticle-Polydopamine-Reduced Graphene Oxide Ternary Nanocomposite as an Efficient Catalyst for Selective Oxidation of Benzylic C(sp3)−H Bonds Under Mild Conditions. ChemCatChem 2016. [DOI: 10.1002/cctc.201600136] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Biju Majumdar
- Discipline of Chemistry, School of Basic Sciences; Indian Institute of Technology Indore, Simrol; Khandwa Road Indore 452020 India
| | - Tamalika Bhattacharya
- Discipline of Chemistry, School of Basic Sciences; Indian Institute of Technology Indore, Simrol; Khandwa Road Indore 452020 India
| | - Tridib K. Sarma
- Discipline of Chemistry, School of Basic Sciences; Indian Institute of Technology Indore, Simrol; Khandwa Road Indore 452020 India
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Jafarpour M, Rezaeifard A, Yasinzadeh V, Kargar H. Starch-coated maghemite nanoparticles functionalized by a novel cobalt Schiff base complex catalyzes selective aerobic benzylic C–H oxidation. RSC Adv 2015. [DOI: 10.1039/c5ra04718h] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The CoL2@SMNP nanocatalyst catalyzed heterogeneous aerobic oxidation of benzylic C–H bonds of saturated hydrocarbons and alcohols to the related carbonyl compounds.
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Affiliation(s)
- Maasoumeh Jafarpour
- Catalysis Research Laboratory
- Department of Chemistry
- Faculty of Science
- University of Birjand
- Birjand
| | - Abdolreza Rezaeifard
- Catalysis Research Laboratory
- Department of Chemistry
- Faculty of Science
- University of Birjand
- Birjand
| | - Vahid Yasinzadeh
- Catalysis Research Laboratory
- Department of Chemistry
- Faculty of Science
- University of Birjand
- Birjand
| | - Hossein Kargar
- Catalysis Research Laboratory
- Department of Chemistry
- Faculty of Science
- University of Birjand
- Birjand
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Siddaraju Y, Prabhu KR. A chemoselective α-aminoxylation of aryl ketones: a cross dehydrogenative coupling reaction catalysed by Bu4NI. Org Biomol Chem 2015; 13:11651-6. [DOI: 10.1039/c5ob01929j] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Tetrabutyl ammonium iodide (TBAI) catalyzed α-aminoxylation of ketones using aq. TBHP as an oxidant has been accomplished.
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Affiliation(s)
- Yogesh Siddaraju
- Department of Organic Chemistry
- Indian Institute of Science
- Bangalore 560 012
- India
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12
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Gonzalez-de-Castro A, Robertson CM, Xiao J. Dehydrogenative α-oxygenation of ethers with an iron catalyst. J Am Chem Soc 2014; 136:8350-60. [PMID: 24835531 DOI: 10.1021/ja502167h] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Selective α-oxidation of ethers under aerobic conditions is a long-pursued transformation; however, a green and efficient catalytic version of this reaction remains challenging. Herein, we report a new family of iron catalysts capable of promoting chemoselective α-oxidation of a range of ethers with excellent mass balance and high turnover numbers under 1 atm of O2 with no need for any additives. Unlike metalloenzymes and related biomimetics, the catalyst produces H2 as the only byproduct. Mechanistic investigations provide evidence for an unexpected two-step reaction pathway, which involves dehydrogenative incorporation of O2 into the ether to give a peroxobisether intermediate followed by cleavage of the peroxy bond to form two ester molecules, releasing stoichiometric H2 gas in each step. The operational simplicity and environmental friendliness of this methodology affords a useful alternative for performing oxidation, while the unique ability of the catalyst in oxygenating a substrate via dehydrogenation points to a new direction for understanding metalloenzymes and designing new biomimetic catalysts.
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Melone L, Punta C. Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review. Beilstein J Org Chem 2013; 9:1296-310. [PMID: 23843925 PMCID: PMC3701383 DOI: 10.3762/bjoc.9.146] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 06/12/2013] [Indexed: 01/20/2023] Open
Abstract
Since the beginning of the century, N-hydroxyphthalimide and related compounds have been revealed to be efficient organocatalysts for free-radical processes and have found ample application in promoting the aerobic oxidation of a wide range of organic substrates. When combined with different co-catalysts, they are activated to the corresponding N-oxyl radical species and become able to promote radical chains, involving molecular oxygen, directly or indirectly. Most of the examples reported in the literature describe the use of these N-hydroxy derivatives in the presence of transition-metal complexes. However, eco-friendly standards, including the demand for highly selective transformations, impose the development of metal-free processes, especially for large-scale productions, as in the case of the oxygenation of hydrocarbons. For this reason, many efforts have been devoted in the past decade to the design of new protocols for the activation of N-hydroxy imides in the presence of nonmetal initiators. Herein we provide a concise overview of the most significant and successful examples in this field, with the final aim to furnish a useful instrument for all scientists actively involved in the O2-mediated selective oxidation of organic compounds and looking for environmentally safe alternatives to metal catalysis.
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Affiliation(s)
- Lucio Melone
- Department of Chemistry, Materials, and Chemical Engineering "Giulio Natta", Politecnico di Milano, Piazza L. Da Vinci 32, Milano 20131, Italy ; INSTM, National Consortium of Materials Science and Technology, Local Unit Politecnico di Milano, Italy
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Chen K, Jia L, Dao R, Yao J, Wang C, Chen Z, Li H. Theoretical Studies on Muti-Hydroxyimides as Highly Efficient Catalysts for Aerobic Oxidation. Chemphyschem 2012. [DOI: 10.1002/cphc.201200865] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Lu T, Mao Y, Yao K, Xu J, Lu M. Metal free: A novel and efficient aerobic oxidation of toluene derivatives catalyzed by N′, N″, N‴, -trihydroxyisocyanuric acid and dimethylglyoxime in PEG-1000-based dicationic acidic ionic liquid. CATAL COMMUN 2012. [DOI: 10.1016/j.catcom.2012.07.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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G. Tsoungas P, Cordopatis P, Gardikis Y, Potamitis C, Zervou M, Pairas G. Xanthones in Heterocyclic Synthesis. An Efficient and General Route for the Synthesis of Regioselectively Substituted Phthalazines. HETEROCYCLES 2011. [DOI: 10.3987/com-11-12168] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Affiliation(s)
- Jens Hartung
- Fachbereich Chemie, Organische Chemie, Technische Universität Kaiserslautern, Erwin-Schrödinger-Strasse, D-67663 Kaiserslautern, Germany.
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Coseri S. Phthalimide‐N‐oxyl (PINO) Radical, a Powerful Catalytic Agent: Its Generation and Versatility Towards Various Organic Substrates. CATALYSIS REVIEWS-SCIENCE AND ENGINEERING 2009. [DOI: 10.1080/01614940902743841] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Abstract
Developments in modern organic synthesis owe much to the field of radical chemistry. Mild reaction conditions, high selectivity, good functional group tolerance and high product yield are features that have made reactions involving radical species indispensable tools for synthetic chemists. In part, the discovery of new radical initiators has led to the efficiency that now characterizes most radical reactions. This Account describes our investigations of radical reactions initiated by dimethylzinc. In 2001, we unexpectedly observed this reaction while investigating the amidophosphane-copper-catalyzed asymmetric addition of dimethylzinc to N-sulfonyl imines with tetrahydrofuran (THF) as reaction solvent. However, instead of adding the desired methyl group to the N-sulfonyl imine, we produced the THF adduct in excellent yield. This result laid the foundation for our discovery of novel modes of reactivity. Further investigations of the unexpected addition reaction revealed that a trace amount of air was needed for reaction progress, indicating that radical intermediates were involved. Indeed, controlled injection of air into the reaction flask by a syringe pump through a sodium hydroxide tube afforded the products in good to excellent yield. In addition, the reaction proved to be chemoselective for a C=N bond over a C=O bond, as well as for 1,4-addition over 1,2-addition. We developed asymmetric variants of the radical addition reaction of ethers to imines using chiral N-sulfinyl imines to produce the adducts in reasonably high stereoselectivity (up to 11:1). A 93:7 diastereomeric ratio of the adduct was obtained when bis(8-phenylmenthyl) benzylidenemalonate was used in the radical addition of ethers to C=C bonds. Interestingly, in the presence of dimethylzinc and air, arylamines, alkoxyamines, and dialkylhydrazines react with THF to give amino alcohols, oximes, and hydrazones, respectively, in moderate to high yields. We performed a tin-free intermolecular addition of functionalized primary alkyl groups, generated from their corresponding iodides, to N-sulfonyl imines using dimethylzinc, air, boron trifluoride diethyl etherate, and a catalytic amount of copper(II) triflate. Direct C-H bond cleavage from cycloalkanes was also feasible in the presence of dimethylzinc, air, and boron trifluoride diethyl etherate to give the corresponding cycloalkyl radicals, which were suitable nucleophiles for N-sulfonyl imines. In all of the above reactions, dimethylzinc was a superior radical initiator than other conventional initiators such as dibenzoyl peroxide, diethylzinc, and triethylborane. We hope the coming decades will witness the report of other novel radical initiators that would complement the reactivity modes of existing ones.
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Affiliation(s)
- Tito Akindele
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Ken-ichi Yamada
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kiyoshi Tomioka
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
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Shaabani A, Rahmati A. Aerobic oxidation of alkyl arenes using a combination of N-hydroxy phthalimide and recyclable cobalt(II) tetrasulfophthalocyanine supported on silica. CATAL COMMUN 2008. [DOI: 10.1016/j.catcom.2007.12.023] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Recupero F, Punta C. Free Radical Functionalization of Organic Compounds Catalyzed byN-Hydroxyphthalimide. Chem Rev 2007; 107:3800-42. [PMID: 17848093 DOI: 10.1021/cr040170k] [Citation(s) in RCA: 478] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Francesco Recupero
- Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Politecnico di Milano, Via Mancinelli 7, I-20131 Milano MI, Italy
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Yamamoto Y, Maekawa M, Akindele T, Yamada KI, Tomioka K. Dimethylzinc-initiated radical reaction of cyclic ethers with arylamines, alkoxyamines, and dialkylhydrazines. Tetrahedron 2005. [DOI: 10.1016/j.tet.2004.10.080] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Yang G, Zhang Q, Miao H, Tong X, Xu J. Selective Organocatalytic Oxygenation of Hydrocarbons by Dioxygen Using Anthraquinones and N-Hydroxyphthalimide. Org Lett 2004; 7:263-6. [PMID: 15646973 DOI: 10.1021/ol047749p] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[Reaction: see text] Purely organic and catalytic systems of anthraquinones and N-hydroxyphthalimide efficiently promote oxygenation of hydrocarbons with dioxygen under mild conditions, e.g., fluorene can be converted completely to fluorenone with 85% yield at 80 degrees C.
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Affiliation(s)
- Guanyu Yang
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian, 116023, PR China
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A convenient access to benzo-substituted phthalazines as potential precursors to DNA intercalators. Tetrahedron Lett 2001. [DOI: 10.1016/s0040-4039(01)01302-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Sakaguchi S, Nishiwaki Y, Kitamura T, Ishii Y. Efficient Catalytic Alkane Nitration with NO2 under Air Assisted byN-Hydroxyphthalimide. Angew Chem Int Ed Engl 2001. [DOI: 10.1002/1521-3757(20010105)113:1<228::aid-ange228>3.0.co;2-r] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Sakaguchi S, Nishiwaki Y, Kitamura T, Ishii Y. Efficient Catalytic Alkane Nitration with NO2 under Air Assisted by N-Hydroxyphthalimide. Angew Chem Int Ed Engl 2001; 40:222-224. [DOI: 10.1002/1521-3773(20010105)40:1<222::aid-anie222>3.0.co;2-w] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2000] [Indexed: 11/05/2022]
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Einhorn C, Einhorn J, Marcadal-Abbadi C. MILD AND CONVENIENT ONE POT SYNTHESIS OFN-HYDROXYIMIDES FROMN-UNSUBSTITUTED IMIDES. SYNTHETIC COMMUN 2001. [DOI: 10.1081/scc-100103264] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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