51
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Nguyen LN, Hai FI, Kang J, Leusch FD, Roddick F, Magram SF, Price WE, Nghiem LD. Enhancement of trace organic contaminant degradation by crude enzyme extract from Trametes versicolor culture: Effect of mediator type and concentration. J Taiwan Inst Chem Eng 2014. [DOI: 10.1016/j.jtice.2014.03.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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52
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Díaz-Rodríguez A, Martínez-Montero L, Lavandera I, Gotor V, Gotor-Fernández V. Laccase/2,2,6,6-Tetramethylpiperidinoxyl Radical (TEMPO): An Efficient Catalytic System for Selective Oxidations of Primary Hydroxy and Amino Groups in Aqueous and Biphasic Media. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201400260] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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53
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Mazzonna M, Bietti M, DiLabio GA, Lanzalunga O, Salamone M. Importance of π-Stacking Interactions in the Hydrogen Atom Transfer Reactions from Activated Phenols to Short-Lived N-Oxyl Radicals. J Org Chem 2014; 79:5209-18. [DOI: 10.1021/jo500789v] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Marco Mazzonna
- Dipartimento
di Chimica and Istituto CNR di Metodologie
Chimiche (IMC−CNR), Sezione Meccanismi di Reazione, c/o Dipartimento
di Chimica, Sapienza Università di Roma, P.le A. Moro, 5, I-00185 Rome, Italy
| | - Massimo Bietti
- Dipartimento
di Scienze e Tecnologie Chimiche, Università “Tor Vergata”, Via della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Gino A. DiLabio
- National
Institute for Nanotechnology, National Research Council of Canada, 11421
Saskatchewan Drive, Edmonton, Alberta, Canada T6G 2M9
- Department
of Chemistry, University of British Columbia, Okanagan, 3333 University
Way, Kelowna, British Columbia, Canada V1V 1V7
| | - Osvaldo Lanzalunga
- Dipartimento
di Chimica and Istituto CNR di Metodologie
Chimiche (IMC−CNR), Sezione Meccanismi di Reazione, c/o Dipartimento
di Chimica, Sapienza Università di Roma, P.le A. Moro, 5, I-00185 Rome, Italy
| | - Michela Salamone
- Dipartimento
di Scienze e Tecnologie Chimiche, Università “Tor Vergata”, Via della Ricerca Scientifica, 1, I-00133 Rome, Italy
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54
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Heidary M, Khoobi M, Ghasemi S, Habibi Z, Faramarzi MA. Synthesis of Quinazolinones from AlcoholsviaLaccase-Mediated Tandem Oxidation. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201400103] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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55
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Comparing the catalytic efficiency of ring substituted 1-hydroxybenzotriazoles as laccase mediators. Tetrahedron 2014. [DOI: 10.1016/j.tet.2014.02.068] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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56
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Tetianec L, Chaleckaja A, Vidziunaite R, Kulys J, Bachmatova I, Marcinkeviciene L, Meskys R. Development of a laccase/syringaldazine system for NAD(P)H oxidation. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.molcatb.2013.12.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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57
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Mogharabi M, Faramarzi MA. Laccase and Laccase-Mediated Systems in the Synthesis of Organic Compounds. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201300960] [Citation(s) in RCA: 183] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
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58
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Bernini R, Crisante F, Gentili P, Menta S, Morana F, Pierini M. Unexpected different chemoselectivity in the aerobic oxidation of methylated planar catechin and bent epicatechin derivatives catalysed by the Trametes villosa laccase/1-hydroxybenzotriazole system. RSC Adv 2014. [DOI: 10.1039/c3ra47753c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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59
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Shiraishi T, Sannami Y, Kamitakahara H, Takano T. Comparison of a series of laccase mediators in the electro-oxidation reactions of non-phenolic lignin model compounds. Electrochim Acta 2013. [DOI: 10.1016/j.electacta.2013.05.112] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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60
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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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61
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Coseri S, Biliuta G, Simionescu BC, Stana-Kleinschek K, Ribitsch V, Harabagiu V. Oxidized cellulose—Survey of the most recent achievements. Carbohydr Polym 2013; 93:207-15. [DOI: 10.1016/j.carbpol.2012.03.086] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Revised: 03/22/2012] [Accepted: 03/27/2012] [Indexed: 11/30/2022]
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62
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Andreu G, Vidal T. Laccase from Pycnoporus cinnabarinus and phenolic compounds: can the efficiency of an enzyme mediator for delignifying kenaf pulp be predicted? BIORESOURCE TECHNOLOGY 2013; 131:536-540. [PMID: 23403063 DOI: 10.1016/j.biortech.2013.01.033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 01/04/2013] [Accepted: 01/06/2013] [Indexed: 06/01/2023]
Abstract
In this work, kenaf pulp was delignified by using laccase in combination with various redox mediators and the efficiency of the different laccase–mediator systems assessed in terms of the changes in pulp properties after bleaching. The oxidative ability of the individual mediators used (acetosyringone, syringaldehyde, p-coumaric acid, vanillin and actovanillone) and the laccase–mediator systems was determined by monitoring the oxidation–reduction potential (ORP) during process. The results confirmed the production of phenoxy radicals of variable reactivity and stressed the significant role of lignin structure in the enzymatic process. Although changes in ORP were correlated with the oxidative ability of the mediators, pulp properties as determined after the bleaching stage were also influenced by condensation and grafting reactions. As shown here, ORP measurements provide a first estimation of the delignification efficiency of a laccase–mediator system.
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Affiliation(s)
- Glòria Andreu
- Chemical Engineering Department, ETSEIAT, Universitat Politècnica de Catalunya, Colom 11, E-08222 Terrassa, Spain
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63
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D’Alfonso C, Bietti M, DiLabio GA, Lanzalunga O, Salamone M. Reactions of the Phthalimide N-Oxyl Radical (PINO) with Activated Phenols: The Contribution of π-Stacking Interactions to Hydrogen Atom Transfer Rates. J Org Chem 2013; 78:1026-37. [DOI: 10.1021/jo302483s] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Claudio D’Alfonso
- Dipartimento di Chimica, Sapienza
Università di Roma and Istituto CNR di Metodologie Chimiche
(IMC−CNR), Sezione Meccanismi di Reazione, c/o Dipartimento
di Chimica, Sapienza Università di Roma, P.le A. Moro, 5 I-00185 Rome, Italy
| | - Massimo Bietti
- Dipartimento di Scienze e Tecnologie
Chimiche, Università ″Tor Vergata″, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
| | - Gino A. DiLabio
- National Institute for Nanotechnology, National Research Council of Canada, 11421 Saskatchewan
Drive, Edmonton, Alberta, Canada T6G 2M9
- Department of Physics, University of Alberta, Edmonton, Alberta, Canada
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica, Sapienza
Università di Roma and Istituto CNR di Metodologie Chimiche
(IMC−CNR), Sezione Meccanismi di Reazione, c/o Dipartimento
di Chimica, Sapienza Università di Roma, P.le A. Moro, 5 I-00185 Rome, Italy
| | - Michela Salamone
- Dipartimento di Scienze e Tecnologie
Chimiche, Università ″Tor Vergata″, Via della Ricerca Scientifica, 1 I-00133 Rome, Italy
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64
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Aracri E, Tzanov T, Vidal T. Use of Cyclic Voltammetry as an Effective Tool for Selecting Efficient Enhancers for Oxidative Bioprocesses: Importance of pH. Ind Eng Chem Res 2013. [DOI: 10.1021/ie3027586] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Elisabetta Aracri
- Department
of Textile and Paper Engineering and ‡Group of Molecular and Industrial
Biotechnology, Department of Chemical Engineering, Universitat Politècnica de Catalunya—BarcelonaTech, E-08222 Terrassa, Spain
| | - Tzanko Tzanov
- Department
of Textile and Paper Engineering and ‡Group of Molecular and Industrial
Biotechnology, Department of Chemical Engineering, Universitat Politècnica de Catalunya—BarcelonaTech, E-08222 Terrassa, Spain
| | - Teresa Vidal
- Department
of Textile and Paper Engineering and ‡Group of Molecular and Industrial
Biotechnology, Department of Chemical Engineering, Universitat Politècnica de Catalunya—BarcelonaTech, E-08222 Terrassa, Spain
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65
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Asta C, Schmidt D, Conrad J, Förster-Fromme B, Tolasch T, Beifuss U. The first enzymatic Achmatowicz reaction: selective laccase-catalyzed synthesis of 6-hydroxy-(2H)-pyran-3(6H)-ones and (2H)-pyran-2,5(6H)-diones. RSC Adv 2013. [DOI: 10.1039/c3ra44107e] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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66
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In situ aldehyde generation for aldol addition reactions catalyzed by d-fructose-6-phosphate aldolase. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.molcatb.2012.02.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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67
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Rosado T, Bernardo P, Koci K, Coelho AV, Robalo MP, Martins LO. Methyl syringate: an efficient phenolic mediator for bacterial and fungal laccases. BIORESOURCE TECHNOLOGY 2012; 124:371-378. [PMID: 22995168 DOI: 10.1016/j.biortech.2012.08.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 08/03/2012] [Accepted: 08/04/2012] [Indexed: 06/01/2023]
Abstract
The aim of the present work is to provide insight into the mechanism of laccase reactions using syringyl-type mediators. We studied the pH dependence and the kinetics of oxidation of syringyl-type phenolics using the low CotA and the high redox potential TvL laccases. Additionally, the efficiency of these compounds as redox mediators for the oxidation of non-phenolic lignin units was tested at different pH values and increasing mediator/non-phenolic ratios. Finally, the intermediates and products of reactions were identified by LC-MS and (1)H NMR. These approaches allow concluding on the (1) mechanism involved in the oxidation of phenolics by bacterial laccases, (2) importance of the chemical nature and properties of phenolic mediators, (3) apparent independence of the enzyme's properties on the yields of non-phenolics conversion, (4) competitive routes involved in the catalytic cycle of the laccase-mediator system with several new C-O coupling type structures being proposed.
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Affiliation(s)
- Tânia Rosado
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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68
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Wertz S, Studer A. Metal-Free 2,2,6,6-Tetramethylpiperidin-1-yloxy Radical (TEMPO) Catalyzed Aerobic Oxidation of Hydroxylamines and Alkoxyamines to Oximes and Oxime Ethers. Helv Chim Acta 2012. [DOI: 10.1002/hlca.201200175] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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69
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Guazzaroni M, Bozzini T, Saladino R. Synthesis of Aldehydes by Layer-by-Layer Immobilized Laccases in the Presence of Redox Mediators. ChemCatChem 2012. [DOI: 10.1002/cctc.201200330] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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70
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71
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Constantin MA, Conrad J, Merişor E, Koschorreck K, Urlacher VB, Beifuss U. Oxidative Dimerization of (E)- and (Z)-2-Propenylsesamol with O2 in the Presence and Absence of Laccases and Other Catalysts: Selective Formation of Carpanones and Benzopyrans under Different Reaction Conditions. J Org Chem 2012; 77:4528-43. [DOI: 10.1021/jo300263k] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mihaela-Anca Constantin
- Bioorganische Chemie, Institut für
Chemie, Universität Hohenheim, Garbenstraße
30, D-70599 Stuttgart, Germany
| | - Jürgen Conrad
- Bioorganische Chemie, Institut für
Chemie, Universität Hohenheim, Garbenstraße
30, D-70599 Stuttgart, Germany
| | - Elena Merişor
- Bioorganische Chemie, Institut für
Chemie, Universität Hohenheim, Garbenstraße
30, D-70599 Stuttgart, Germany
| | - Katja Koschorreck
- Institut für Biochemie, Heinrich-Heine Universität Düsseldorf, Universitätsstraße 1,
D-40225 Düsseldorf, Germany
| | - Vlada B. Urlacher
- Institut für Biochemie, Heinrich-Heine Universität Düsseldorf, Universitätsstraße 1,
D-40225 Düsseldorf, Germany
| | - Uwe Beifuss
- Bioorganische Chemie, Institut für
Chemie, Universität Hohenheim, Garbenstraße
30, D-70599 Stuttgart, Germany
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72
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Fillat A, Gallardo O, Vidal T, Pastor F, Díaz P, Roncero M. Enzymatic grafting of natural phenols to flax fibres: Development of antimicrobial properties. Carbohydr Polym 2012; 87:146-152. [DOI: 10.1016/j.carbpol.2011.07.030] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 05/30/2011] [Accepted: 07/20/2011] [Indexed: 11/26/2022]
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73
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Hajdok S, Conrad J, Beifuss U. Laccase-catalyzed domino reactions between hydroquinones and cyclic 1,3-dicarbonyls for the regioselective synthesis of substituted p-benzoquinones. J Org Chem 2011; 77:445-59. [PMID: 22117114 DOI: 10.1021/jo202082v] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Highly substituted p-benzoquinones were obtained in yields ranging from 39% to 98% by laccase-catalyzed domino reactions between hydroquinones and cyclic 1,3-dicarbonyls using aerial oxygen as the oxidant. In almost all reactions bis-adducts with two adjacent 1,3-dicarbonyl substituents on the quinone moiety were formed selectively. The transformations can be regarded as domino oxidation/1,4-addition/oxidation/1,4-addition/oxidation processes. With unsubstituted hydroquinone as the substrate 2,3-disubstituted p-benzoquinones were isolated. Bis-adducts were also formed exclusively upon reaction with monosubstituted hydroquinones. In almost all cases the 2,3,5-trisubstituted p-benzoquinones were obtained. When 2,3-disubstituted hydroquinones were employed as starting materials the 2,3,5,6-tetrasubstituted p-benzoquinones were isolated. The unambiguous structure elucidation of all products has been achieved by NMR spectroscopic methods including spin pattern analysis of the long-range coupled C═O carbons and (13)C satellites analysis in (1)H NMR spectra.
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Affiliation(s)
- Szilvia Hajdok
- Bioorganische Chemie, Institut für Chemie, Universität Hohenheim, Garbenstrasse 30, D-70599 Stuttgart, Germany
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74
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Baciocchi E, Bietti M, D'Alfonso C, Lanzalunga O, Lapi A, Salamone M. One-electron oxidation of ferrocenes by short-lived N-oxyl radicals. The role of structural effects on the intrinsic electron transfer reactivities. Org Biomol Chem 2011; 9:4085-90. [PMID: 21541382 DOI: 10.1039/c0ob01257b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A kinetic study of the one electron oxidation of substituted ferrocenes (FcX: X = H, COPh, COMe, CO(2)Et, CONH(2), CH(2)OH, Et, and Me(2)) by a series of N-oxyl radicals (succinimide-N-oxyl radical (SINO), maleimide-N-oxyl radical (MINO), 3-quinazolin-4-one-N-oxyl radical (QONO) and 3-benzotriazin-4-one-N-oxyl radical (BONO)), has been carried out in CH(3)CN. N-oxyl radicals were produced by hydrogen abstraction from the corresponding N-hydroxy derivatives by the cumyloxyl radical. With all systems, the rate constants exhibited a satisfactory fit to the Marcus equation allowing us to determine self-exchange reorganization energy values (λ(NO˙/NO(-))) which have been compared with those previously determined for the PINO/PINO(-) and BTNO/BTNO(-) couples. Even small modification of the structure of the N-oxyl radicals lead to significant variation of the λ(NO˙/NO(-)) values. The λ(NO˙/NO(-)) values increase in the order BONO < BTNO < QONO < PINO < SINO < MINO which do not parallel the order of the oxidation potentials. The higher λ(NO˙/NO(-)) values found for the MINO and SINO radicals might be in accordance with a lower degree of spin delocalization in the radicals MINO and SINO and charge delocalization in the anions MINO(-) and SINO(-) due to the absence of an aromatic ring in their structure.
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Affiliation(s)
- Enrico Baciocchi
- Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, Rome, Italy
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75
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Andreu G, Vidal T. Effects of laccase-natural mediator systems on kenaf pulp. BIORESOURCE TECHNOLOGY 2011; 102:5932-7. [PMID: 21444198 DOI: 10.1016/j.biortech.2011.03.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 03/01/2011] [Accepted: 03/03/2011] [Indexed: 05/09/2023]
Abstract
This paper reports the first application of laccase-mediator systems (LMS) to kenaf pulp. Five natural phenolic compounds (acetosyringone, syringaldehyde, p-coumaric acid, vanillin and acetovanillone) were used as mediators in combination with laccase in an L stage in order to elucidate their effect on delignification. After LMS treatment, pulp samples were subjected to two alkaline treatments (an E or P stage). The results obtained were compared with those provided by the laccase-1-hydroxybenzotriazole (HBT) system. All natural mediators increased kappa number, decreased brightness and changed optical properties of the pulp after the L stage, suggesting that natural mediators tend to couple to fibers during a laccase-mediator treatment. The greatest delignification and bleaching effects after the P stage were obtained with syringaldehyde and acetosyringone, providing an effective means for delignifying kenaf, whereas those based on the other three could be used to functionalize kenaf with a view to obtaining pulp with novel properties.
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Affiliation(s)
- Glòria Andreu
- Chemical Engineering Department, ETSEIAT, Universitat Politècnica de Catalunya, Colom 11, E-08222 Terrassa, Spain
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76
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Tebben L, Studer A. Nitroxides: applications in synthesis and in polymer chemistry. Angew Chem Int Ed Engl 2011; 50:5034-68. [PMID: 21538729 DOI: 10.1002/anie.201002547] [Citation(s) in RCA: 505] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Indexed: 01/23/2023]
Abstract
This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.
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Affiliation(s)
- Ludger Tebben
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
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77
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Hanson SK, Wu R, Silks LA“P. Mild and Selective Vanadium-Catalyzed Oxidation of Benzylic, Allylic, and Propargylic Alcohols Using Air. Org Lett 2011; 13:1908-11. [DOI: 10.1021/ol103107v] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Susan K. Hanson
- Chemistry and Biosciences Divisions, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Ruilian Wu
- Chemistry and Biosciences Divisions, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - L. A. “Pete” Silks
- Chemistry and Biosciences Divisions, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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78
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A new laccase-catalyzed domino process and its application to the efficient synthesis of 2-aryl-1H-benzimidazoles. Tetrahedron Lett 2011. [DOI: 10.1016/j.tetlet.2010.11.145] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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79
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Bernini R, Crisante F, Gentili P, Morana F, Pierini M, Piras M. Chemoselective C-4 aerobic oxidation of catechin derivatives catalyzed by the Trametes villosa laccase/1-hydroxybenzotriazole system: synthetic and mechanistic aspects. J Org Chem 2011; 76:820-32. [PMID: 21204551 DOI: 10.1021/jo101886s] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Catechin derivatives were oxidized in air in the presence of the Trametes villosa laccase/1-hydroxybenzotriazole (HBT) system in buffered water/1,4-dioxane as reaction medium. The oxidation products, flavan-3,4-diols and the corresponding C-4 ketones, are bioactive compounds and useful intermediates for the hemisynthesis of proanthocyanidins, plant polyphenols which provide beneficial health properties for humans. Determinations of oxidation potentials excluded that catechin derivatives could be directly oxidized by laccase Cu(II), while it resulted in the H-abstraction from benzylic positions being promptly promoted by the enzyme in the presence of the mediator HBT, the parent species producing in situ the reactive intermediate benzotriazole-N-oxyl (BTNO) radical. A remarkable and unexpected result for the laccase/HBT oxidative system has been the chemoselective insertion of the oxygen atom into the C-4-H bond of catechin derivatives. Mechanistic aspects of the oxidation reaction have been investigated in detail for the first time in order to corroborate these results. Since the collected experimental findings could not alone provide information useful to clarify the origin of the observed chemoselectivity, these data were expressly supplemented with information derived by suitable molecular modeling investigations. The integrated evaluation of the dissociation energies of the C-H bonds calculated both by semiempirical and DFT methods and the differential activation energies of the process estimated by a molecular modeling approach suggested that the observed selective oxidation at the C-4 carbon has a kinetic origin.
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Affiliation(s)
- Roberta Bernini
- Dipartimento di Agrobiologia e Agrochimica, Università degli Studi della Tuscia, Viterbo, Italy.
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80
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Aracri E, Fillat A, Colom JF, Gutiérrez A, Del Río JC, Martínez AT, Vidal T. Enzymatic grafting of simple phenols on flax and sisal pulp fibres using laccases. BIORESOURCE TECHNOLOGY 2010; 101:8211-8216. [PMID: 20580550 DOI: 10.1016/j.biortech.2010.05.080] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 05/19/2010] [Accepted: 05/25/2010] [Indexed: 05/29/2023]
Abstract
Flax and sisal pulps were treated with two laccases (from Pycnoporus cinnabarinus, PcL and Trametes villosa, TvL, respectively), in the presence of different phenolic compounds (syringaldehyde, acetosyringone and p-coumaric acid in the case of flax pulp, and coniferaldehyde, sinapaldehyde, ferulic acid and sinapic acid in the case of sisal pulp). In most cases the enzymatic treatments resulted in increased kappa number of pulps suggesting the incorporation of the phenols into fibres. The covalent binding of these compounds to fibres was evidenced by the analysis of the treated pulps, after acetone extraction, by pyrolysis coupled with gas chromatography/mass spectrometry in the absence and/or in the presence of tetramethylammonium hydroxide (TMAH) as methylating agent. The highest extents of phenol incorporation were observed with the p-hydroxycinnamic acids, p-coumaric and ferulic acids. The present work shows for the first time the use of analytical pyrolysis as an effective approach to study fibre functionalization by laccase-induced grafting of phenols.
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Affiliation(s)
- Elisabetta Aracri
- Textile and Paper Engineering Department, ETSEIAT, Universitat Politècnica de Catalunya, Colom 11, E-08222 Terrassa, Spain
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81
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Tadesse MA, Galli C, Gentili P. Hydrogen abstraction from H-donor substrates by the 6-CF3-benzotriazol-N-oxyl radical (TFNO). J PHYS ORG CHEM 2010. [DOI: 10.1002/poc.1783] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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82
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Biliuta G, Fras L, Strnad S, Harabagiu V, Coseri S. Oxidation of cellulose fibers mediated by nonpersistent nitroxyl radicals. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/pola.24270] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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83
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Brioche J, Masson G, Zhu J. Passerini three-component reaction of alcohols under catalytic aerobic oxidative conditions. Org Lett 2010; 12:1432-5. [PMID: 20218637 DOI: 10.1021/ol100012y] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alcohols instead of aldehydes were used in the Passerini three-component reaction under catalytic aerobic conditions. Mixing alcohols, isocyanides, and carboxylic acids in toluene in the presence of a catalytic amount of cupric chloride, NaNO(2), and TEMPO afforded, under an oxygen atmosphere, the P-3CR adducts in good yields.
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Affiliation(s)
- Julien Brioche
- Centre de Recherche de Gif, Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette Cedex, France
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84
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Cañas AI, Camarero S. Laccases and their natural mediators: biotechnological tools for sustainable eco-friendly processes. Biotechnol Adv 2010; 28:694-705. [PMID: 20471466 DOI: 10.1016/j.biotechadv.2010.05.002] [Citation(s) in RCA: 406] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 04/21/2010] [Accepted: 04/30/2010] [Indexed: 11/27/2022]
Abstract
Laccases are oxidoreductases which oxidize a variety of aromatic compounds using oxygen as the electron acceptor and producing water as by-product. The interest for these old enzymes (first described in 19th century) has progressively increased due to their outstanding biotechnological applicability. The presence of redox mediators is required for a number of biotechnological applications, providing the oxidation of complex substrates not oxidized by the enzyme alone. The efficiency of laccase-mediator systems to degrade recalcitrant compounds has been demonstrated, but still the high cost and possible toxicity of artificial mediators hamper their application at the industrial scale. Here, we present a general outlook of how alternative mediators can change this tendency. We focus on phenolic compounds related to lignin polymer that promotes the in vitro transformation of recalcitrant non-phenolic structures by laccase and are seemingly the natural mediators of laccases. The use of eco-friendly mediators easily available from lignocellulose, could contribute to the industrial implementation of laccases and the development of the 21th century biorefineries.
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Affiliation(s)
- Ana I Cañas
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, Madrid, Spain
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85
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Baciocchi E, Bietti M, Lanzalunga O, Lapi A, Raponi D. N-demethylation of N,N-dimethylanilines by the benzotriazole N-oxyl radical: evidence for a two-step electron transfer-proton transfer mechanism. J Org Chem 2010; 75:1378-85. [PMID: 20146440 DOI: 10.1021/jo100040y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction of the benzotriazole N-oxyl radical (BTNO) with a series of 4-X-N,N-dimethylanilines (X = CN, CF(3), CO(2)CH(2)CH(3), CH(3), OC(6)H(5), OCH(3)) has been investigated in CH(3)CN. Product analysis shows that the radical, 4-X-C(6)H(4)N(CH(3))CH(2)(*), is first formed, which can lead to the N-demethylated product or the product of coupling with BTNO. Reaction rates were found to increase significantly by increasing the electron-donating power of the aryl substituents (rho(+) = -3.8). With electron-donating substituents (X = CH(3), OC(6)H(5), OCH(3)), no intermolecular deuterium kinetic isotope effect (DKIE) and a substantial intramolecular DKIE are observed. With electron-withdrawing substituents (X = CN, CF(3), CO(2)CH(2)CH(3)), substantial values of both intermolecular and intramolecular DKIEs are observed. These results can be interpreted on the basis of an electron-transfer mechanism from the N,N-dimethylanilines to the BTNO radical followed by deprotonation of the anilinium radical cation (ET-PT mechanism). By applying the Marcus equation to the kinetic data for X = CH(3), OC(6)H(5), OCH(3) (rate-determining ET), a reorganization energy for the ET reaction was determined (lambda(BTNO/DMA) = 32.1 kcal mol(-1)). From the self-exchange reorganization energy for the BTNO/BTNO(-) couple, a self-exchange reorganization energy value of 31.9 kcal mol(-1) was calculated for the DMA(*+)/DMA couple.
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Affiliation(s)
- Enrico Baciocchi
- Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma, Piazzale A. Moro 5, I-00185 Rome, Italy
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86
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The laccase-catalyzed domino reaction between catechols and heterocyclic 1,3-dicarbonyls and the unambiguous structure elucidation of the products by NMR spectroscopy and X-ray crystal structure analysis. J Org Chem 2009; 74:7230-7. [PMID: 19739645 DOI: 10.1021/jo9011915] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The laccase-catalyzed reaction between catechols and heterocyclic 1,3-dicarbonyls (pyridinones, quinolinones, thiocoumarins) using aerial oxygen as the oxidant delivers benzofuropyridinones, benzofuroquinolinones, and thiocoumestans in a simple fashion, highly regioselectively with yields ranging from 55 to 98%. With barbituric acid derivatives the exclusive formation of dispiropyrimidinone derivatives takes place. The unambiguous and complete structure elucidation of all reaction products has been achieved by means of NMR spectroscopic methods (HSQMBC and band-selective HMBC) as well as by X-ray crystal structure analysis.
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87
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Díaz González M, Vidal T, Tzanov T. Electrochemical Study of Phenolic Compounds as Enhancers in Laccase-Catalyzed Oxidative Reactions. ELECTROANAL 2009. [DOI: 10.1002/elan.200904678] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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88
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Pogni R, Brogioni B, Baratto MC, Sinicropi A, Giardina P, Pezzella C, Sannia G, Basosi R. Evidence for a radical mechanism in biocatalytic degradation of synthetic dyes by fungal laccases mediated by violuric acid. BIOCATAL BIOTRANSFOR 2009. [DOI: 10.1080/10242420701422757] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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89
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Baciocchi E, Bietti M, Di Fusco M, Lanzalunga O, Raponi D. Electron-Transfer Properties of Short-Lived N-Oxyl Radicals. Kinetic Study of the Reactions of Benzotriazole-N-oxyl Radicals with Ferrocenes. Comparison with the Phthalimide-N-oxyl Radical. J Org Chem 2009; 74:5576-83. [DOI: 10.1021/jo900951c] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Enrico Baciocchi
- Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma, piazzale A. Moro, 5 I-00185 Rome, Italy
| | - Massimo Bietti
- Dipartimento di Scienze e Tecnologie Chimiche, Università “Tor Vergata”, Via della Ricerca Scientifica, I-00133 Rome, Italy
| | - Massimo Di Fusco
- Dipartimento di Chimica, Sapienza Università di Roma, piazzale A. Moro, 5 I-00185 Rome, Italy
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica, Sapienza Università di Roma, piazzale A. Moro, 5 I-00185 Rome, Italy
- Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma, piazzale A. Moro, 5 I-00185 Rome, Italy
| | - Daniele Raponi
- Dipartimento di Chimica, Sapienza Università di Roma, piazzale A. Moro, 5 I-00185 Rome, Italy
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90
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91
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Zoia L, Argyropoulos DS. Phenoxy radical detection using 31
P NMR spin trapping. J PHYS ORG CHEM 2009. [DOI: 10.1002/poc.1561] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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92
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Lahtinen M, Kruus K, Boer H, Kemell M, Andberg M, Viikari L, Sipilä J. The effect of lignin model compound structure on the rate of oxidation catalyzed by two different fungal laccases. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.molcatb.2008.09.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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93
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Rodríguez-Couto S, Osma JF, Toca-Herrera JL. Removal of synthetic dyes by an eco-friendly strategy. Eng Life Sci 2009. [DOI: 10.1002/elsc.200800088] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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94
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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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95
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González Arzola K, Arévalo M, Falcón M. Catalytic efficiency of natural and synthetic compounds used as laccase-mediators in oxidising veratryl alcohol and a kraft lignin, estimated by electrochemical analysis. Electrochim Acta 2009. [DOI: 10.1016/j.electacta.2008.10.059] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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96
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Coniglio A, Galli C, Gentili P, Vadalà R. Hydrogen atom abstraction from C-H bonds of benzylamides by the aminoxyl radical BTNO: a kinetic study. Org Biomol Chem 2008; 7:155-60. [PMID: 19081958 DOI: 10.1039/b815584d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The aminoxyl radical BTNO (benzotriazole-N-oxyl; >N-O*) is generated from HBT (1-hydroxybenzotriazole; >N-OH) by oxidation with a Ce(IV) salt. BTNO presents a broad absorption band with lambda(max) 474 nm that lends itself to investigate the kinetics of H-abstraction from H-donor substrates by spectrophotometry. Thus, rate constants (k(H)) of H-abstraction by BTNO from CH(2)-groups alpha to the nitrogen atom in X-substituted-(N-acetyl)benzylamines (X-C(6)H(4)CH(2)NHCOCH(3)) have been determined in MeCN solution at 25 degrees C. Correlation of the k(H)(X) data with the Hammett sigma(+) parameters gives a small value for rho (-0.65) that is compatible with a radical H-abstraction step. The sizeable value (k(H)/k(D)=8.8) of the kinetic isotope effect from a suitably deuteriated amide substrate further confirms H-abstraction as rate-determining. Evidence is acquired for the relevance of stereoelectronic effects that speed up the H-abstraction whenever the scissile C-H bond is co-linear with either the nitrogen lone-pair of the amide moiety or an adjacent aromatic group. An assessment of the dissociation energy value of the benzylic C-H bond in ArCH(2)NHCOMe is accordingly reported.
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Affiliation(s)
- Alessandra Coniglio
- Dipartimento di Chimica, Università La Sapienza, and IMC-CNR Sezione Meccanismi di Reazione, P.le A. Moro 5, 00185, Roma, Italy
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97
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Moldes D, Díaz M, Tzanov T, Vidal T. Comparative study of the efficiency of synthetic and natural mediators in laccase-assisted bleaching of eucalyptus kraft pulp. BIORESOURCE TECHNOLOGY 2008; 99:7959-65. [PMID: 18499450 DOI: 10.1016/j.biortech.2008.04.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Revised: 03/31/2008] [Accepted: 04/03/2008] [Indexed: 05/03/2023]
Abstract
The natural phenolic compounds syringaldehyde and vanillin were compared to the synthetic mediators 1-hydroxybenzotriazole, violuric acid and promazine in terms of boosting efficiency in a laccase-assisted biobleaching of eucalyptus kraft pulp. Violuric acid and 1-hydroxybenzotriazole revealed to be the most effective mediators of the bioprocess. Nevertheless, laccase-syringaldehyde system also improved the final pulp properties (28% delignification and 63.5% ISO brightness) compared to the process without mediator (23% and 61.5% respectively), in addition to insignificant denaturation effect over laccase. The efficiency of the biobleaching process was further related to changes in non-conventionally used optical and chromatic parameters of pulp, such as (L*), chroma (C*) and dye removal index (DRI) showing good correlation. Adverse coupling reactions of the natural phenolic mediators on pulp lignin were predicted by electrochemical studies, demonstrating the complexity of the laccase-mediator reaction on pulp.
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Affiliation(s)
- D Moldes
- Department of Textile and Paper Engineering, Universitat Politècnica de Catalunya, Colom 11, E-08222 Terrassa, Spain.
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98
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Brogioni B, Biglino D, Sinicropi A, Reijerse EJ, Giardina P, Sannia G, Lubitz W, Basosi R, Pogni R. Characterization of radical intermediates in laccase-mediator systems. A multifrequency EPR, ENDOR and DFT/PCM investigation. Phys Chem Chem Phys 2008; 10:7284-92. [PMID: 19060974 DOI: 10.1039/b812096j] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Suitable low molecular-weight compounds, called mediators, can be used in combination with the phenol-oxidase enzyme laccase to indirectly oxidize large organic substrates, such as environmental pollutants, which are not laccase natural substrates. The oxidation of two different synthetic redox mediators, violuric acid (VIO) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) has been studied under catalysis of two laccases from white-rot fungi (Trametes versicolor and Pleurotus ostreatus). VIO was selected as a prototype of the -NOH type of mediators and compared to ABTS, a well-known two-step redox system. To characterize the radical intermediates formed from both mediators after the enzymatic oxidation, a multifrequency EPR approach has been adopted. The radical species have been investigated employing 9.4 GHz (X-band), 34 GHz (Q-band) and 244 GHz (high field) EPR and pulse electron nuclear double resonance (ENDOR) techniques. Theoretical calculations based on density functional theory (DFT/PCM) have been performed to support and further interpret the experimental EPR and ENDOR data. This integrated approach allowed us to obtain a complete characterization of both radicals and to elucidate the type of the radical state (neutral or cationic).
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Affiliation(s)
- Barbara Brogioni
- Department of Chemistry, University of Siena, Via Aldo Moro, 53100, Siena, Italy
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99
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Galli C, Gentili P, Lanzalunga O. Wasserstoffabstraktion und Elektronentransfer mit Aminoxylradikalen: Synthesen und Mechanismen. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200704292] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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100
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Galli C, Gentili P, Lanzalunga O. Hydrogen Abstraction and Electron Transfer with Aminoxyl Radicals: Synthetic and Mechanistic Issues. Angew Chem Int Ed Engl 2008; 47:4790-6. [DOI: 10.1002/anie.200704292] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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