101
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Yang C, Xue XS, Li X, Cheng JP. Computational Study on the Acidic Constants of Chiral Brønsted Acids in Dimethyl Sulfoxide. J Org Chem 2014; 79:4340-51. [DOI: 10.1021/jo500158e] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Chen Yang
- State Key
Laboratory of Elemento-Organic
Chemistry, Department of Chemistry, and Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Xiao-Song Xue
- State Key
Laboratory of Elemento-Organic
Chemistry, Department of Chemistry, and Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Xin Li
- State Key
Laboratory of Elemento-Organic
Chemistry, Department of Chemistry, and Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
| | - Jin-Pei Cheng
- State Key
Laboratory of Elemento-Organic
Chemistry, Department of Chemistry, and Collaborative Innovation Center
of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
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102
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Hans M, Delaude L, Rodriguez J, Coquerel Y. N-heterocyclic carbene catalyzed carba-, sulfa-, and phospha-Michael additions with NHC·CO₂ adducts as precatalysts. J Org Chem 2014; 79:2758-64. [PMID: 24568358 DOI: 10.1021/jo500108a] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
N-heterocyclic carbene catalyzed Michael additions have been revisited with 1,3-dialkyl- or 1,3-diarylimidazol(in)ium-2-carboxylates, that is, NHC·CO2 adducts, as the source of the free NHC catalysts in solution. Using these precatalysts, a number of efficient carba-, sulfa-, and phospha-Michael additions were achieved very conveniently, without the need for an external strong base to generate the NHC by deprotonation of an azolium salt. To further expand the scope of the procedure, some NHC-catalyzed sulfa-Michael/aldol organocascades were also investigated.
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Affiliation(s)
- Morgan Hans
- Laboratory of Organometallic Chemistry and Homogeneous Catalysis, Institut de chimie (B6a), Université de Liège , Sart-Tilman par 4000 Liège, Belgium
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103
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Asymmetric catalysis with N-heterocyclic carbenes as non-covalent chiral templates. Nat Commun 2014; 5:3437. [PMID: 24599089 DOI: 10.1038/ncomms4437] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 02/12/2014] [Indexed: 11/08/2022] Open
Abstract
N-heterocyclic carbenes are a class of persistent carbenes stabilized by adjacent heteroatoms that are part of a heterocycle. They play a central role in multiple enzymatic biosynthetic reactions that involve thiamine diphosphate. Inspired by this biocatalysis machinery, N-heterocyclic carbenes have emerged as one of the most versatile classes of organocatalysts for organic reactions. However, the asymmetric synthesis of carbon-carbon bonds through a non-covalent interaction mechanism has not been previously established for chiral carbenes. Here, we report an N-heterocylic carbene-catalysed, highly enantioselective process that uses weak hydrogen bonds to relay asymmetric bias. We find that catalytic amounts of hexafluoroisopropanol are the critical proton shuttle that facilitates hydrogen transfer to provide high-reaction rates and high enantioselectivity. We demonstrate that a successful asymmetric reaction of this type can be accomplished through a rational design that balances the pKa values of the substrate, the carbene precursor and the product.
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104
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Mahatthananchai J, Bode JW. On the mechanism of N-heterocyclic carbene-catalyzed reactions involving acyl azoliums. Acc Chem Res 2014; 47:696-707. [PMID: 24410291 DOI: 10.1021/ar400239v] [Citation(s) in RCA: 563] [Impact Index Per Article: 56.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Catalytic reactions promoted by N-heterocyclic carbenes (NHCs) have exploded in popularity since 2004 when several reports described new fundamental reactions that extended beyond the long-studied generation of acyl anion equivalents. These new NHC-catalyzed reactions allow chemists to generate unique reactive species from otherwise inert starting materials, all under simple, mild reaction conditions and with exceptional selectivities. In analogy to transition metal catalysis, the use of NHCs has introduced a new set of elementary steps that operate via discrete reactive species, including acyl anion, homoenolate, and enolate equivalents, usually generated by oxidation state reorganization ("redox neutral" reactions). Nearly all NHC-catalyzed reactions offer operationally simple reactions, proceed at room temperature without the need for stringent exclusion of air, and do not generate reaction byproducts. Variation of the catalyst or reaction conditions can profoundly influence reaction outcomes, and researchers can tune the desired selectivities through careful choice of NHC precursor and base. The catalytically generated homoenolate and enolate equivalents are nucleophilic species. In contrast, the catalytically generated acyl azolium and α,β-unsaturated acyl azoliums are electrophilic cationic species with unique and unprecedented chemistry. For example, when generated catalytically, these species transformed an α-functionalized aldehyde to an ester under redox neutral conditions without coupling reagents or waste. In addition to providing new approaches to catalytic esterifications, acyl azoliums offer unique reactivities that chemists can exploit for selective reactions. This Account focuses on the discovery and mechanistic investigation of the catalytic generation of acyl azoliums and α,β-unsaturated acyl azoliums. These chemical species are fascinating, and their catalytic generation is an important development. Studies of their unusual chemistry, however, date back to the intense investigation of thiamine-dependent enzymatic processes in the 1960s. Acyl azoliums are remarkably reactive in acylation chemistry and are unusually chemoselective. These two properties have led to a new wave of reactions such as redox esterification reaction (1) and the catalytic kinetic resolution of challenging substrates (i.e., 3). Our group and others have also developed methods to generate and exploit α,β-unsaturated acyl azoliums, which have facilitated new C-C bond-forming annulations, including a catalytic, enantioselective variant of the Claisen rearrangement (2). From essentially one class of catalysts, the N-mesityl derived triazolium salts, researchers can easily prepare highly enantioenriched dihydropyranones and dihydropyridinones. Although this field is now one of the most explored areas of enantioselective C-C bond forming reactions, many mechanistic details remained unsolved and in dispute. In this Account, we address the mechanistic inquiries about the characterization of the unsaturated acyl triazolium species and its kinetic profile under catalytically relevant conditions. We also provide explanations for the requirement and effect of the N-mesityl group in NHC catalysis based on detailed experimental data within given specific reactions or conditions. We hope that our studies provide a roadmap for catalyst design/selection and new reaction discovery based on a fundamental understanding of the mechanistic course of NHC reactions.
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Affiliation(s)
- Jessada Mahatthananchai
- Laboratorium für Organische Chemie, ETH−Zürich, Wolfgang Pauli Strasse 10, 8093 Zürich, Switzerland
| | - Jeffrey W. Bode
- Laboratorium für Organische Chemie, ETH−Zürich, Wolfgang Pauli Strasse 10, 8093 Zürich, Switzerland
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105
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Albrecht M. Normal and Abnormal N-Heterocyclic Carbene Ligands. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2014. [DOI: 10.1016/b978-0-12-800976-5.00002-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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106
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Johnston RC, Cohen DT, Eichman CC, Scheidt KA, Cheong PHY. Catalytic Kinetic Resolution of a Dynamic Racemate: Highly Stereoselective β-Lactone Formation by N-Heterocyclic Carbene Catalysis. Chem Sci 2014; 5:1974-1982. [PMID: 25045464 DOI: 10.1039/c4sc00317a] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
This study describes the combined experimental and computational elucidation of the mechanism and origins of stereoselectivities in the NHC-catalyzed dynamic kinetic resolution (DKR) of α-substituted-β-ketoesters. Density functional theory computations reveal that the NHC-catalyzed DKR proceeds by two mechanisms, depending on the stereochemistry around the forming bond: 1) a concerted, asynchronous formal (2+2) aldol-lactonization process, or 2) a stepwise spiro-lactonization mechanism where the alkoxide is trapped by the NHC-catalyst. These mechanisms contrast significantly from mechanisms found and postulated in other related transformations. Conjugative stabilization of the electrophile and non-classical hydrogen bonds are key in controlling the stereoselectivity. This reaction constitutes an interesting class of DKRs in which the catalyst is responsible for the kinetic resolution to selectively and irreversibly capture an enantiomer of a substrate undergoing rapid racemization with the help of an exogenous base.
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Affiliation(s)
- Ryne C Johnston
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331, USA
| | - Daniel T Cohen
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Chad C Eichman
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Karl A Scheidt
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Paul Ha-Yeon Cheong
- Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR, 97331, USA
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107
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Schulze B, Schubert US. Beyond click chemistry – supramolecular interactions of 1,2,3-triazoles. Chem Soc Rev 2014; 43:2522-71. [DOI: 10.1039/c3cs60386e] [Citation(s) in RCA: 583] [Impact Index Per Article: 58.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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108
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Nawaz F, Zaghouani M, Bonne D, Chuzel O, Rodriguez J, Coquerel Y. Design, Synthesis, and Organocatalytic Activity of N-Heterocyclic Carbenes Functionalized with Hydrogen-Bond Donors in Enantioselective Reactions of Homoenolates. European J Org Chem 2013. [DOI: 10.1002/ejoc.201301366] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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109
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Taylor JE, Daniels DSB, Smith AD. Asymmetric NHC-Catalyzed Redox α-Amination of α-Aroyloxyaldehydes. Org Lett 2013; 15:6058-61. [DOI: 10.1021/ol402955f] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- James E. Taylor
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, United Kingdom
| | - David S. B. Daniels
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, United Kingdom
| | - Andrew D. Smith
- EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, United Kingdom
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110
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Chen M, Moerdyk JP, Blake GA, Bielawski CW, Lee JK. Assessing the Proton Affinities of N,N′-Diamidocarbenes. J Org Chem 2013; 78:10452-8. [DOI: 10.1021/jo401902c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Mu Chen
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, United States
| | - Jonathan P. Moerdyk
- Department
of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712,
United States
| | - Garrett A. Blake
- Department
of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712,
United States
| | - Christopher W. Bielawski
- Department
of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712,
United States
| | - Jeehiun K. Lee
- Department
of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, United States
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111
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Davies AT, Taylor JE, Douglas J, Collett CJ, Morrill LC, Fallan C, Slawin AMZ, Churchill G, Smith AD. Stereospecific Asymmetric N-Heterocyclic Carbene (NHC)-Catalyzed Redox Synthesis of Trifluoromethyl Dihydropyranones and Mechanistic Insights. J Org Chem 2013; 78:9243-57. [DOI: 10.1021/jo401433q] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Alyn T. Davies
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
| | - James E. Taylor
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
| | - James Douglas
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
| | - Christopher J. Collett
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
| | - Louis C. Morrill
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
| | - Charlene Fallan
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
| | - Alexandra M. Z. Slawin
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
| | - Gwydion Churchill
- Process
Research and Development, AstraZeneca, Macclesfield, Cheshire SK10 2NA, United Kingdom
| | - Andrew D. Smith
- EaStCHEM,
School of Chemistry, University of St Andrews, North Haugh, St Andrews KY16 9ST, United Kingdom
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112
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Park C, Lee BS, Chi DY. High efficiency synthesis of F-18 fluoromethyl ethers: an attractive alternative for C-11 methyl groups in positron emission tomography radiopharmaceuticals. Org Lett 2013; 15:4346-9. [PMID: 23930998 DOI: 10.1021/ol401792n] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A rapid and efficient method for the synthesis of O-fluoromethyl aliphatic and aromatic ethers is presented. This method is so mild that it can be used for the preparation of positron emission tomography (PET) radiopharmaceuticals bearing O-[(18)F]fluoromethyl groups.
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Affiliation(s)
- Chansoo Park
- Department of Chemistry, Sogang University, 35 Baekbeomro Mapogu, Seoul 121-742, Korea
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113
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Yotphan S, Beukeaw D, Reutrakul V. Synthesis of 2-aminobenzoxazoles via copper-catalyzed electrophilic amination of benzoxazoles with O-benzoyl hydroxylamines. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.05.127] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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114
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Boulanger E, Anoop A, Nachtigallova D, Thiel W, Barbatti M. Photochemical Steps in the Prebiotic Synthesis of Purine Precursors from HCN. Angew Chem Int Ed Engl 2013; 52:8000-3. [DOI: 10.1002/anie.201303246] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Indexed: 11/07/2022]
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115
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Boulanger E, Anoop A, Nachtigallova D, Thiel W, Barbatti M. Photochemical Steps in the Prebiotic Synthesis of Purine Precursors from HCN. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201303246] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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116
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Hans M, Wouters J, Demonceau A, Delaude L. Mechanistic Insight into the Staudinger Reaction Catalyzed by N-Heterocyclic Carbenes. Chemistry 2013; 19:9668-76. [DOI: 10.1002/chem.201204428] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 04/11/2013] [Indexed: 11/07/2022]
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117
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Daily LA, Miller KM. Correlating Structure with Thermal Properties for a Series of 1-Alkyl-4-methyl-1,2,4-triazolium Ionic Liquids. J Org Chem 2013; 78:4196-201. [DOI: 10.1021/jo4003932] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lucas A. Daily
- Department of Chemistry, Murray State University, 1201 Jesse D. Jones Hall, Murray, Kentucky
42071, United States
| | - Kevin M. Miller
- Department of Chemistry, Murray State University, 1201 Jesse D. Jones Hall, Murray, Kentucky
42071, United States
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118
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Nelson DJ, Nolan SP. Quantifying and understanding the electronic properties of N-heterocyclic carbenes. Chem Soc Rev 2013; 42:6723-53. [DOI: 10.1039/c3cs60146c] [Citation(s) in RCA: 808] [Impact Index Per Article: 73.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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119
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Delany EG, Fagan CL, Gundala S, Mari A, Broja T, Zeitler K, Connon SJ. NHC-catalysed aerobic aldehyde-esterifications with alcohols: no additives or cocatalysts required. Chem Commun (Camb) 2013; 49:6510-2. [DOI: 10.1039/c3cc42596g] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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120
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Collett CJ, Massey RS, Maguire OR, Batsanov AS, O'Donoghue AC, Smith AD. Mechanistic insights into the triazolylidene-catalysed Stetter and benzoin reactions: role of the N-aryl substituent. Chem Sci 2013. [DOI: 10.1039/c2sc22137c] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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