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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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2
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Thadathil DA, Varghese A, Ahamed CVS, Krishnakumar K, Varma SS, Lankalapalli RS, Radhakrishnan KV. Enzyme based bioelectrocatalysis over laccase immobilized poly-thiophene supported carbon fiber paper for the oxidation of D-ribofuranose to D-ribonolactone. MOLECULAR CATALYSIS 2022. [DOI: 10.1016/j.mcat.2022.112314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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3
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Pokhrel T, B K B, Giri R, Adhikari A, Ahmed N. C-H Bond Functionalization under Electrochemical Flow Conditions. CHEM REC 2022; 22:e202100338. [PMID: 35315954 DOI: 10.1002/tcr.202100338] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 03/04/2022] [Accepted: 03/07/2022] [Indexed: 01/12/2023]
Abstract
Electrochemical C-H functionalization is a rapidly growing area of interest in organic synthesis. To achieve maximum atom economy, the flow electrolysis process is more sustainable. This allows shorter reaction times, safer working environments, and better selectivities. Using this technology, the problem of overoxidation can be reduced and less emergence of side products or no side products are possible. Flow electro-reactors provide high surface-to-volume ratios and contain electrodes that are closely spaced where the diffusion layers overlap to give the desired product, electrochemical processes can now be managed without the need for a deliberately added supporting electrolyte. Considering the importance of flow electrochemical C-H functionalization, a comprehensive review is presented. Herein, we summarize flow electrolysis for the construction of C-C and C-X (X=O, N, S, and I) bonds formation. Also, benzylic oxidation and access to biologically active molecules are discussed.
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Affiliation(s)
- Tamlal Pokhrel
- Central Department of Chemistry, Tribhuvan University, Kirtipur, 44618, Kathmandu, Nepal
| | - Bijaya B K
- Central Department of Chemistry, Tribhuvan University, Kirtipur, 44618, Kathmandu, Nepal
| | - Ramesh Giri
- Central Department of Chemistry, Tribhuvan University, Kirtipur, 44618, Kathmandu, Nepal
| | - Achyut Adhikari
- Central Department of Chemistry, Tribhuvan University, Kirtipur, 44618, Kathmandu, Nepal
| | - Nisar Ahmed
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, United Kingdom
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4
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Murray PD, Cox JH, Chiappini ND, Roos CB, McLoughlin EA, Hejna BG, Nguyen ST, Ripberger HH, Ganley JM, Tsui E, Shin NY, Koronkiewicz B, Qiu G, Knowles RR. Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis. Chem Rev 2022; 122:2017-2291. [PMID: 34813277 PMCID: PMC8796287 DOI: 10.1021/acs.chemrev.1c00374] [Citation(s) in RCA: 150] [Impact Index Per Article: 75.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Indexed: 12/16/2022]
Abstract
We present here a review of the photochemical and electrochemical applications of multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms in which both an electron and a proton are exchanged together, often in a concerted elementary step. As such, MS-PCET can function as a non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from a wide variety of common organic functional groups. We present an introduction to MS-PCET and a practitioner's guide to reaction design, with an emphasis on the unique energetic and selectivity features that are characteristic of this reaction class. We then present chapters on oxidative N-H, O-H, S-H, and C-H bond homolysis methods, for the generation of the corresponding neutral radical species. Then, chapters for reductive PCET activations involving carbonyl, imine, other X═Y π-systems, and heteroarenes, where neutral ketyl, α-amino, and heteroarene-derived radicals can be generated. Finally, we present chapters on the applications of MS-PCET in asymmetric catalysis and in materials and device applications. Within each chapter, we subdivide by the functional group undergoing homolysis, and thereafter by the type of transformation being promoted. Methods published prior to the end of December 2020 are presented.
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Affiliation(s)
- Philip
R. D. Murray
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - James H. Cox
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Nicholas D. Chiappini
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Casey B. Roos
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | | | - Benjamin G. Hejna
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Suong T. Nguyen
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Hunter H. Ripberger
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Jacob M. Ganley
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Elaine Tsui
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Nick Y. Shin
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Brian Koronkiewicz
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Guanqi Qiu
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Robert R. Knowles
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
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5
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He Y, Qin X, He X, Wu X, Yin Z. Practical Synthesis of Halogenated
N
‐Heterocycles via Electrochemical Anodic Oxidation of Unactivated Alkenes. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101189] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Yanyang He
- School of Pharmacy Jiangsu University Zhenjiang 212013 P. R. China
| | - Xiaowen Qin
- School of Pharmacy Jiangsu University Zhenjiang 212013 P. R. China
| | - Xinxu He
- School of Pharmacy Jiangsu University Zhenjiang 212013 P. R. China
| | - Xiao‐Feng Wu
- Dalian National Laboratory for Clean Energy Dalian Institute of Chemical Physics Chinese Academy of Science 116023 Dalian Liaoning China
- Leibniz-Institut für Katalyse e.V. Albert-Einstein-Straße 29a 18059 Rostock Germany
| | - Zhiping Yin
- School of Pharmacy Jiangsu University Zhenjiang 212013 P. R. China
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6
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Thadathil DA, Varghese A, Radhakrishnan KV. The Renaissance of Electro‐Organic Synthesis for the Difunctionalization of Alkenes and Alkynes: A Sustainable Approach. ASIAN J ORG CHEM 2021. [DOI: 10.1002/ajoc.202100447] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Ditto Abraham Thadathil
- Department of Chemistry CHRIST (Deemed to be University) Hosur Road Bengaluru, Karnataka 560029 India
| | - Anitha Varghese
- Department of Chemistry CHRIST (Deemed to be University) Hosur Road Bengaluru, Karnataka 560029 India
| | - Kokkuvayil Vasu Radhakrishnan
- Chemical Sciences and Technology Division CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST) Thiruvananthapuram 695019 India
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Ronchetti R, Moroni G, Carotti A, Gioiello A, Camaioni E. Recent advances in urea- and thiourea-containing compounds: focus on innovative approaches in medicinal chemistry and organic synthesis. RSC Med Chem 2021; 12:1046-1064. [PMID: 34355177 PMCID: PMC8293013 DOI: 10.1039/d1md00058f] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 04/23/2021] [Indexed: 12/18/2022] Open
Abstract
Urea and thiourea represent privileged structures in medicinal chemistry. Indeed, these moieties constitute a common framework of a variety of drugs and bioactive compounds endowed with a broad range of therapeutic and pharmacological properties. Herein, we provide an overview of the state-of-the-art of urea and thiourea-containing pharmaceuticals. We also review the diverse approaches pursued for (thio)urea bioisosteric replacements in medicinal chemistry applications. Finally, representative examples of recent advances in the synthesis of urea- and thiourea-based compounds by enabling chemical tools are discussed.
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Affiliation(s)
- Riccardo Ronchetti
- Department of Pharmaceutical Sciences, University of Perugia Via del Liceo 1 06123 Perugia Italy +39 075 5855161 +39 075 5855129
| | - Giada Moroni
- Department of Pharmaceutical Sciences, University of Perugia Via del Liceo 1 06123 Perugia Italy +39 075 5855161 +39 075 5855129
- Department of Chemistry "Giacomo Ciamician", Alma Mater Studiorum, University of Bologna Via Selmi 2 40126 Bologna Italy
| | - Andrea Carotti
- Department of Pharmaceutical Sciences, University of Perugia Via del Liceo 1 06123 Perugia Italy +39 075 5855161 +39 075 5855129
| | - Antimo Gioiello
- Department of Pharmaceutical Sciences, University of Perugia Via del Liceo 1 06123 Perugia Italy +39 075 5855161 +39 075 5855129
| | - Emidio Camaioni
- Department of Pharmaceutical Sciences, University of Perugia Via del Liceo 1 06123 Perugia Italy +39 075 5855161 +39 075 5855129
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8
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Deng XJ, Liu HX, Zhang LW, Zhang GY, Yu ZX, He W. Iodoarene-Catalyzed Oxyamination of Unactivated Alkenes to Synthesize 5-Imino-2-Tetrahydrofuranyl Methanamine Derivatives. J Org Chem 2020; 86:235-253. [PMID: 33336571 DOI: 10.1021/acs.joc.0c02047] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Reported here is the room-temperature metal-free iodoarene-catalyzed oxyamination of unactivated alkenes. In this process, the alkenes are difunctionalized by the oxygen atom of the amide group and the nitrogen in an exogenous HNTs2 molecule. This mild and open-air reaction provided an efficient synthesis to N-bistosyl-substituted 5-imino-2-tetrahydrofuranyl methanamine derivatives, which are important motifs in drug development and biological studies. Mechanistic study based on experiments and density functional theory calculations showed that this transformation proceeds via activation of the substrate alkene by an in situ generated cationic iodonium(III) intermediate, which is subsequently attacked by an oxygen atom (instead of nitrogen) of amides to form a five-membered ring intermediate. Finally, this intermediate undergoes an SN2 reaction by NTs2 as the nucleophile to give the oxygen and nitrogen difunctionalized 5-imino-2-tetrahydrofuranyl methanamine product. An asymmetric variant of the present alkene oxyamination using chiral iodoarenes as catalysts also gave promising results for some of the substrates.
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Affiliation(s)
- Xiao-Jun Deng
- Department of Chemistry, School of Pharmacy, Fourth Military Medical University, Xi'an 710032, China
| | - Hui-Xia Liu
- Department of Chemistry, School of Pharmacy, Fourth Military Medical University, Xi'an 710032, China
| | - Lu-Wen Zhang
- Department of Chemistry, School of Pharmacy, Fourth Military Medical University, Xi'an 710032, China
| | - Guan-Yu Zhang
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Zhi-Xiang Yu
- Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Wei He
- Department of Chemistry, School of Pharmacy, Fourth Military Medical University, Xi'an 710032, China
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9
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Zaib S, Khan I. Synthetic and medicinal chemistry of phthalazines: Recent developments, opportunities and challenges. Bioorg Chem 2020; 105:104425. [PMID: 33157344 DOI: 10.1016/j.bioorg.2020.104425] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/22/2020] [Accepted: 10/20/2020] [Indexed: 12/14/2022]
Abstract
Fused diaza-heterocycles constitute the core structure of numerous bioactive natural products and effective therapeutic drugs. Among them, phthalazines have been recognized as remarkable structural leads in medicinal chemistry due to their wide application in pharmaceutical and agrochemical industries. Accessing such challenging pharmaceutical agents/drug candidates with high chemical complexity through synthetically efficient approaches remains an attractive goal in the contemporary medicinal chemistry and drug discovery arena. In this review, we focus on the recent developments in the synthetic routes towards the generation of phthalazine-based active pharmaceutical ingredients and their biological potential against various targets. The general reaction scope of these innovative and easily accessible strategies was emphasized focusing on the functional group tolerance, substrate and coupling partner compatibility/limitation, the choice of catalyst, and product diversification. These processes were also accompanied by the mechanistic insights where deemed appropriate to demonstrate meaningful information. Moreover, the rapid examination of the structure-activity relationship analyses around the phthalazine core enabled by the pharmacophore replacement/integration revealed the generation of robust, efficient, and more selective compounds with pronounced biological effects. A large variety of in silico methods and ADME profiling tools were also employed to provide a global appraisal of the pharmacokinetics profile of diaza-heterocycles. Thus, the discovery of new structural leads offers the promise of improving treatments for various tropical diseases such as tuberculosis, leishmaniasis, malaria, Chagas disease, among many others including various cancers, atherosclerosis, HIV, inflammatory, and cardiovascular diseases. We hope this review would serve as an informative collection of structurally diverse molecules enabling the generation of mature, high-quality, and innovative routes to support the drug discovery endeavors.
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Affiliation(s)
- Sumera Zaib
- Department of Biochemistry, Faculty of Life Sciences, University of Central Punjab, Lahore 54590, Pakistan
| | - Imtiaz Khan
- Department of Chemistry and Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom.
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10
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Taily IM, Saha D, Banerjee P. Palladium-catalyzed regio- and stereoselective access to allyl ureas/carbamates: facile synthesis of imidazolidinones and oxazepinones. Org Biomol Chem 2020; 18:6564-6570. [PMID: 32789352 DOI: 10.1039/d0ob01514h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Typically, transition metal catalysis enforces the stereodefined outcome of a reaction. Here we disclose the palladium-catalyzed regio- and stereoselective access to allylic ureas/carbamates and their further exploitation to diverse cyclic structures under operationally simple reaction conditions. This protocol features palladium-catalyzed decarboxylative amidation of highly modular VECs with good to excellent yield, minimal waste production, wide substrate scope, and low catalyst loading. In follow-up chemistry, we demonstrated the debenzylation of vinylic imidazolidinones to N-hydroxycyclic ureas and regioselective derivatization towards the facile synthesis of halohydrins and oxiranes under mild reaction conditions in good to excellent yields.
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Affiliation(s)
- Irshad Maajid Taily
- Department of Chemistry, Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab-140001, India.
| | - Debarshi Saha
- Department of Chemistry, Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab-140001, India.
| | - Prabal Banerjee
- Department of Chemistry, Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab-140001, India.
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11
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Wang P, Gao X, Huang P, Lei A. Recent Advances in Electrochemical Oxidative Cross‐Coupling of Alkenes with H
2
Evolution. ChemCatChem 2019. [DOI: 10.1002/cctc.201901773] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Pan Wang
- Institute for Advanced Studies (IAS) College of Chemistry and Molecular SciencesWuhan University Wuhan 430072 P. R. China
| | - Xinlong Gao
- Institute for Advanced Studies (IAS) College of Chemistry and Molecular SciencesWuhan University Wuhan 430072 P. R. China
| | - Pengfei Huang
- Institute for Advanced Studies (IAS) College of Chemistry and Molecular SciencesWuhan University Wuhan 430072 P. R. China
| | - Aiwen Lei
- Institute for Advanced Studies (IAS) College of Chemistry and Molecular SciencesWuhan University Wuhan 430072 P. R. China
- National Research Center for Carbohydrate SynthesisJiangxi Normal University Nanchang 330022 P. R. China
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12
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Khatoon S, Vgenopoulou A, Naseer MM, Shirinfar B, Kariuki BM, Dege N, Ahmed N. Easy Access to Crystalline Indolines
via
Hydrogen Bond Transfer. J Heterocycl Chem 2019. [DOI: 10.1002/jhet.3516] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Saira Khatoon
- School of Chemistry Cardiff University Cardiff CF10 3AT UK
- Department of Chemistry Quaid‐i‐Azam University Islamabad 45320 Pakistan
| | | | | | | | | | - Necmi Dege
- Department of Physics Samsun Ondokuz Mayıs University Samsun 55139 Turkey
| | - Nisar Ahmed
- School of Chemistry Cardiff University Cardiff CF10 3AT UK
- School of Chemistry University of Bristol Bristol BS8 1TS UK
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13
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Recent Advances in the Catalytic Synthesis of Imidazolidin-2-ones and Benzimidazolidin-2-ones. Catalysts 2019. [DOI: 10.3390/catal9010028] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
2-Imidazolidinone and its analogues are omnipresent structural motifs of pharmaceuticals, natural products, chiral auxiliaries, and intermediates in organic syntheses. Over the years, continuous efforts have been addressed to the development of sustainable and more efficient protocols for the synthesis of these heterocycles. This review gives a summary of the catalytic strategies to access imidazolidin-2-ones and benzimidazolidin-2-ones that have appeared in the literature from 2010 to 2018. Particularly important contributions beyond the timespan will be mentioned. The review is organized in four main chapters that identify the most common approaches to imidazolidin-2-one derivatives: (1) the direct incorporation of the carbonyl group into 1,2-diamines, (2) the diamination of olefins, (3) the intramolecular hydroamination of linear urea derivatives and (4) aziridine ring expansion. Methods not included in this classification will be addressed in the miscellaneous section.
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Islam M, Kariuki BM, Shafiq Z, Wirth T, Ahmed N. Efficient Electrosynthesis of Thiazolidin-2-imines via Oxysulfurization of Thiourea-Tethered Terminal Alkenes Using the Flow Microreactor. European J Org Chem 2018. [DOI: 10.1002/ejoc.201801688] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Muhammad Islam
- School of Chemistry; Cardiff University; CF10 3AT Cardiff United Kingdom
| | - Benson M. Kariuki
- School of Chemistry; Cardiff University; CF10 3AT Cardiff United Kingdom
| | - Zahid Shafiq
- Institute of Chemical Sciences; Bahauddin Zakariya University; 60800 Multan Pakistan
| | - Thomas Wirth
- School of Chemistry; Cardiff University; CF10 3AT Cardiff United Kingdom
| | - Nisar Ahmed
- School of Chemistry; Cardiff University; CF10 3AT Cardiff United Kingdom
- School of Chemistry; University of Bristol; BS8 1TS Bristol United Kingdom
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15
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Martins GM, Shirinfar B, Hardwick T, Ahmed N. A Green Approach: Vicinal Oxidative Electrochemical Alkene Difunctionalization. ChemElectroChem 2018. [DOI: 10.1002/celc.201801466] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Guilherme M. Martins
- School of ChemistryCardiff University Main Building, Park Place Cardiff CF10 3AT United Kingdom
- Departamento de QuímicaUniversidade Federal de Santa Maria Santa Maria RS 97105–900 Brazil
| | - Bahareh Shirinfar
- School of ChemistryUniversity of Bristol Bristol BS8 1TS United Kingdom
| | - Tomas Hardwick
- School of Physics and AstronomyUniversity of Manchester Manchester M13 9PL UK
| | - Nisar Ahmed
- School of ChemistryCardiff University Main Building, Park Place Cardiff CF10 3AT United Kingdom
- School of ChemistryUniversity of Bristol Bristol BS8 1TS United Kingdom
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Ahmed N, Khatoon S. Facile Electrochemical Intramolecular Amination of Urea-Tethered Terminal Alkenes for the Synthesis of Cyclic Ureas. ChemistryOpen 2018; 7:576-582. [PMID: 30083492 PMCID: PMC6070678 DOI: 10.1002/open.201800064] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 06/05/2018] [Indexed: 01/11/2023] Open
Abstract
Facile intramolecular amination of unactivated alkenes has been achieved by using electricity as a catalyst that helps to generate an intermediate and accelerates formation of cyclic ureas in high yields. Using this method, no metal catalysts were used. During electrolysis, a nitrogen radical was formed at the urea substrate that cyclised with the alkene and generated a terminal carbon radical which further formed a bond with the 2,2,6,6-tetramethylpiperidine-N-oxyl radical (TEMPO). This method of electrolysis not only gives cyclic ureas but also functionalises terminal unactivated alkenes. This method can be considered to be environmentally friendly given that it avoids the issues of toxicity or complicated metal ligands and could therefore be potentially employed in green chemistry.
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Affiliation(s)
- Nisar Ahmed
- School of ChemistryCardiff UniversityCardiffCF10 3ATUK
| | - Saira Khatoon
- School of ChemistryCardiff UniversityCardiffCF10 3ATUK
- Department of ChemistryQuaid-i-Azam UniversityIslamabad45320Pakistan
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