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Wu X, Smet E, Brandi F, Raikwar D, Zhang Z, Maes BUW, Sels BF. Advancements and Perspectives toward Lignin Valorization via O-Demethylation. Angew Chem Int Ed Engl 2024; 63:e202317257. [PMID: 38128012 DOI: 10.1002/anie.202317257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 12/20/2023] [Accepted: 12/21/2023] [Indexed: 12/23/2023]
Abstract
Lignin represents the largest aromatic carbon resource in plants, holding significant promise as a renewable feedstock for bioaromatics and other cyclic hydrocarbons in the context of the circular bioeconomy. However, the methoxy groups of aryl methyl ethers, abundantly found in technical lignins and lignin-derived chemicals, limit their pertinent chemical reactivity and broader applicability. Unlocking the phenolic hydroxyl functionality through O-demethylation (ODM) has emerged as a valuable approach to mitigate this need and enables further applications. In this review, we provide a comprehensive summary of the progress in the valorization of technical lignin and lignin-derived chemicals via ODM, both catalytic and non-catalytic reactions. Furthermore, a detailed analysis of the properties and potential applications of the O-demethylated products is presented, accompanied by a systematic overview of available ODM reactions. This review primarily focuses on enhancing the phenolic hydroxyl content in lignin-derived species through ODM, showcasing its potential in the catalytic funneling of lignin and value-added applications. A comprehensive synopsis and future outlook are included in the concluding section of this review.
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Affiliation(s)
- Xian Wu
- Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Ewoud Smet
- Organic Synthesis Division, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Francesco Brandi
- Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Deepak Raikwar
- Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Zhenlei Zhang
- Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Bert U W Maes
- Organic Synthesis Division, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, 2020, Antwerp, Belgium
| | - Bert F Sels
- Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
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Borioni J, Baumgartner MT, Puiatti M, Jimenez LB. 1-Substituted Perylene Derivatives by Anionic Cyclodehydrogenation: Analysis of the Reaction Mechanism. ACS OMEGA 2022; 7:21860-21867. [PMID: 35785287 PMCID: PMC9245103 DOI: 10.1021/acsomega.2c02017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
Perylene derivatives constitute a promising class of compounds with technological applications mainly due to their optoelectronic properties. One mechanism proposed to synthesize them, starting from binaphthyl derivatives, is anionic cyclodehydrogenation (under reductive conditions). However, the scope of this reaction is limited. In the present study, we report a theoretical and experimental analysis of this particular reaction mechanism for its use in the synthesis of 1-substituted perylenes. Different substituents at position 2 of 1,1'-binaphthalene were evaluated: -OCH3, -OSi(CH3)2C(CH3)3, and -N(CH3)2. Based on density functional theory (DFT) calculations on the proposed mechanism, we suggest that the cyclization takes place from binaphthyl dianion instead of its radical anion. This dianion has an open-shell diradical nature, and this could be the species that was detected by EPR in previous studies. The O-substituted derivatives could not afford the perylene derivatives since their radical anions fragment and the necessary binaphthyl dianion could not be formed. On the other hand, 49% of N,N-dimethylperylen-1-amine was obtained starting from the N-substituted 2-binapthyl derivative as a substrate, employing a simpler experimental methodology.
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Shigeno M, Hayashi K, Korenaga T, Nozawa-Kumada K, Kondo Y. Organic superbase t-Bu-P4-catalyzed demethylations of methoxyarenes. Org Chem Front 2022. [DOI: 10.1039/d2qo00483f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The organic superbase t-Bu-P4 catalyzes the demethylation reactions of methoxyarenes in the presence of alkanethiol and hexamethyldisilazane.
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Affiliation(s)
- Masanori Shigeno
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai, 980-8578, Japan
| | - Kazutoshi Hayashi
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai, 980-8578, Japan
| | - Toshinobu Korenaga
- Department of Chemistry and Biological Sciences, Faculty of Science and Engineering, Iwate University, Ueda, Morioka, 020-8551, Japan
- Soft-Path Science and Engineering Research Center (SPERC), Iwate University, Ueda, Morioka, 020-8551, Japan
| | - Kanako Nozawa-Kumada
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai, 980-8578, Japan
| | - Yoshinori Kondo
- Department of Biophysical Chemistry, Graduate School of Pharmaceutical Science, Tohoku University, Aoba, Sendai, 980-8578, Japan
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Chernowsky CP, Chmiel AF, Wickens ZK. Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity*. Angew Chem Int Ed Engl 2021; 60:21418-21425. [PMID: 34288312 PMCID: PMC8440429 DOI: 10.1002/anie.202107169] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 07/07/2021] [Indexed: 12/15/2022]
Abstract
Herein, we disclose that electrochemical stimulation induces new photocatalytic activity from a range of structurally diverse conventional photocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2 )-N and C(sp2 )-O bonds. We illustrate several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employ electrochemical current measurements to perform a reaction progress kinetic analysis. This technique reveals that the improved activity of this new system is a consequence of an enhanced catalyst stability profile.
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Affiliation(s)
- Colleen P. Chernowsky
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave, Madison, WI 53706
| | - Alyah F. Chmiel
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave, Madison, WI 53706
| | - Zachary K. Wickens
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave, Madison, WI 53706
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Chernowsky CP, Chmiel AF, Wickens ZK. Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202107169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Colleen P. Chernowsky
- Department of Chemistry University of Wisconsin-Madison 1101 University Ave Madison WI 53706 USA
| | - Alyah F. Chmiel
- Department of Chemistry University of Wisconsin-Madison 1101 University Ave Madison WI 53706 USA
| | - Zachary K. Wickens
- Department of Chemistry University of Wisconsin-Madison 1101 University Ave Madison WI 53706 USA
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Chmiel AF, Williams OP, Chernowsky CP, Yeung CS, Wickens ZK. Non-innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides. J Am Chem Soc 2021; 143:10882-10889. [PMID: 34255971 DOI: 10.1021/jacs.1c05988] [Citation(s) in RCA: 87] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated in situ. The combination of an isophthalonitrile photocatalyst and sodium formate promotes diverse aryl radical coupling reactions from abundant but difficult to reduce aryl chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled by a key terminal reductant byproduct, carbon dioxide radical anion.
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Affiliation(s)
- Alyah F Chmiel
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Oliver P Williams
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Colleen P Chernowsky
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Charles S Yeung
- Discovery Chemistry, Merck & Co., Inc., 33 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States
| | - Zachary K Wickens
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
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7
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Qiu Z, Li CJ. Transformations of Less-Activated Phenols and Phenol Derivatives via C–O Cleavage. Chem Rev 2020; 120:10454-10515. [DOI: 10.1021/acs.chemrev.0c00088] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Zihang Qiu
- Department of Chemistry and FQRNT Centre for Green Chemistry and Catalysis, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
| | - Chao-Jun Li
- Department of Chemistry and FQRNT Centre for Green Chemistry and Catalysis, McGill University, 801 Sherbrooke Street West, Montreal, Quebec H3A 0B8, Canada
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Bal MK, Banks CE, Jones AM. Metabolism Mimicry: An Electrosynthetic Method for the Selective Deethylation of Tertiary Benzamides. ChemElectroChem 2019. [DOI: 10.1002/celc.201900028] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Mandeep K. Bal
- Faculty of Science and EngineeringManchester Metropolitan University Chester Street Manchester M1 5GD United Kingdom
| | - Craig E. Banks
- Faculty of Science and EngineeringManchester Metropolitan University Chester Street Manchester M1 5GD United Kingdom
| | - Alan M. Jones
- School of PharmacyUniversity of Birmingham Edgbaston B15 2TT United Kingdom
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Liu L, Li Z, Chen C, Li H, Xu L, Yu Z. Efficient dealkylation of aryl alkyl ethers catalyzed by Cu 2 O. Tetrahedron 2018. [DOI: 10.1016/j.tet.2018.03.070] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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10
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Kiriyama K, Okura K, Tamakuni F, Shirakawa E. Electron-Catalyzed Coupling of Magnesium Amides with Aryl Iodides. Chemistry 2018; 24:4519-4522. [PMID: 29450924 DOI: 10.1002/chem.201800011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Indexed: 11/06/2022]
Abstract
An electron was found to catalyze the coupling of magnesium diarylamides with aryl iodides giving triarylamines through a radical-anion intermediate. The transformation requires no transition metal catalysts or additives, and a wide array of products are formed in good-to-excellent yields.
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Affiliation(s)
- Kazuya Kiriyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto, 606-8502, Japan
| | - Keisho Okura
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto, 606-8502, Japan
| | - Fumiko Tamakuni
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto, 606-8502, Japan
| | - Eiji Shirakawa
- Department of Applied Chemistry for Environment, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo, 669-1337, Japan
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Ogawa N, Yamaoka Y, Yamada KI, Takasu K. Synthesis of π-Extended Fluoranthenes via a KHMDS-Promoted Anionic-Radical Reaction Cascade. Org Lett 2017; 19:3327-3330. [PMID: 28590747 DOI: 10.1021/acs.orglett.7b01538] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An unprecedented KHMDS-promoted domino reaction to furnish hydroxyfluoranthenes is described. Biaryl compounds bearing acyl and naphthylalkenyl moieties are transformed into 9-hydroxydibenzo[j,l]fluoranthenes in a single step through the formation of an aromatic and a pentagonal ring system. A variety of fluoranthenes including those with extended π-conjugation, a heteroaromatic ring, and unsymmetrical substituents could be synthesized. Mechanistic studies reveal a unique reaction cascade where KHMDS acts as both a base and a single-electron donor.
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Affiliation(s)
- Naoki Ogawa
- Graduate School of Pharmaceutical Sciences, Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Yousuke Yamaoka
- Graduate School of Pharmaceutical Sciences, Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Ken-Ichi Yamada
- Graduate School of Pharmaceutical Sciences, Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kiyosei Takasu
- Graduate School of Pharmaceutical Sciences, Kyoto University , Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
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12
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Pshenichnyuk SA, Modelli A, Jones D, Lazneva EF, Komolov AS. Low-Energy Electron Interaction with Melatonin and Related Compounds. J Phys Chem B 2017; 121:3965-3974. [PMID: 28394598 DOI: 10.1021/acs.jpcb.7b01408] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The electron attaching properties and fragmentation of temporary negative ions of melatonin and its biosynthetic precursor tryptophan are studied in vacuo using dissociative electron attachment (DEA) spectroscopy. The experimental findings are interpreted in silico with the support of Hartree-Fock and density functional theory calculations of empty orbital energies and symmetries, and evaluation of the electron affinities of the indolic molecules under investigation. The only fragment anions formed by DEA to melatonin at incident electron energies below 2 eV are associated with the elimination of a hydrogen atom (energetically favored from the NH site of the pyrrole ring, leaving the ring intact) or a CH3· radical from the temporary molecular negative ion. Opening of the pyrrole ring of melatonin is not detected over the whole electron energy range of 0-14 eV. The DEA spectra of l- and d-tryptophan are almost identical under the present experimental conditions. The adiabatic electron affinity of melatonin is predicted to be -0.49 eV at the B3LYP/6-31+G(d) level, indicating that the DEA mechanism in melatonin is likely to be present in most life forms given the availability of low energy electrons in living systems in both plant and animal kingdoms. In particular, H atom donation usually associated with free-radical scavenging activity can be stimulated by electron attachment and N-H bond cleavage at electron energies around 1 eV.
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Affiliation(s)
- Stanislav A Pshenichnyuk
- Institute of Molecule and Crystal Physics, Ufa Research Centre, Russian Academy of Sciences , Prospeκt Oktyabrya 151, 450075 Ufa, Russia.,St. Petersburg State University , Universitetskaya nab. 7/9, 199034 St. Petersburg, Russia
| | - Alberto Modelli
- Dipartimento di Chimica "G. Ciamician″, Università di Bologna , via Selmi 2, 40126 Bologna, Italy.,Centro Interdipartimentale di Ricerca in Scienze Ambientali , via S. Alberto 163, 48123 Ravenna, Italy
| | - Derek Jones
- ISOF, Istituto per la Sintesi Organica e la Fotoreattività , C.N.R., via Gobetti 101, 40129 Bologna, Italy
| | - Eleonora F Lazneva
- St. Petersburg State University , Universitetskaya nab. 7/9, 199034 St. Petersburg, Russia
| | - Alexei S Komolov
- St. Petersburg State University , Universitetskaya nab. 7/9, 199034 St. Petersburg, Russia
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13
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Azzena U, Carraro M, Meloni C, Murgia I, Pisano L, Pittalis M, Luisi R, Musio B, Degennaro L. Regio- and stereochemistry of Na-mediated reductive cleavage of alkyl aryl ethers. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.tetasy.2014.10.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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14
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Zhang X, Yong G, She W. In Situ Demethoxylation, Dechloridation, or Decyanogenation from Coupling Aromatic Compounds Mediated by Potassium Metal. SYNTHETIC COMMUN 2013. [DOI: 10.1080/00397911.2012.744057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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15
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Yamada H, Ikeda Y, Nagao K, Kasai Y. Synthesis of Ellagitannins Containing Axial-Rich Glucose. J SYN ORG CHEM JPN 2013. [DOI: 10.5059/yukigoseikyokaishi.71.1051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Singh S, de Tacconi NR, Boston D, MacDonnell FM. Photoinduced ligand transformations in a ruthenium complex of dimethoxytetrapyridotetraazapentacene. Dalton Trans 2010; 39:11180-7. [DOI: 10.1039/c0dt00982b] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Selective aromatic carbon–oxygen bond cleavage of trifluoromethoxyarenes: a trifluoromethoxy group as a convertible directing group. Tetrahedron Lett 2008. [DOI: 10.1016/j.tetlet.2008.08.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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21
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Azzena U, Dettori G, Mascia I, Pisano L, Pittalis M. Ion pairing effects on the regioselectivity of arylic versus benzylic C–O bond reductive cleavage: synthetic applications. Tetrahedron 2007. [DOI: 10.1016/j.tet.2007.09.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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23
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Stolarzewicz A, Grobelny Z, Pisarski W, Łosiewicz B, Piekarnik B, Swinarew A. Photochemical, Electrochemical and Enzymatic Methods for Ether‐Bond Cleavage. European J Org Chem 2006. [DOI: 10.1002/ejoc.200500794] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Andrzej Stolarzewicz
- Institute of Materials Science, University of Silesia, 40‐007 Katowice, Poland, Fax: +48‐32‐259‐6929
| | - Zbigniew Grobelny
- Institute of Materials Science, University of Silesia, 40‐007 Katowice, Poland, Fax: +48‐32‐259‐6929
| | - Wojciech Pisarski
- Institute of Materials Science, University of Silesia, 40‐007 Katowice, Poland, Fax: +48‐32‐259‐6929
| | - Bożena Łosiewicz
- Institute of Materials Science, University of Silesia, 40‐007 Katowice, Poland, Fax: +48‐32‐259‐6929
| | - Beata Piekarnik
- Institute of Materials Science, University of Silesia, 40‐007 Katowice, Poland, Fax: +48‐32‐259‐6929
| | - Andrzej Swinarew
- Institute of Materials Science, University of Silesia, 40‐007 Katowice, Poland, Fax: +48‐32‐259‐6929
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Yus M, Foubelo F. Homologation of Heterocycles by a Sequential Reductive Opening Lithiation–Electrophilic Substitution–Cyclization. ADVANCES IN HETEROCYCLIC CHEMISTRY 2006. [DOI: 10.1016/s0065-2725(06)91002-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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25
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Hazimeh H, Mattalia JM, Marchi-Delapierre C, Barone R, Nudelman NS, Chanon M. Radical clocks and electron transfer. Comparison of crown ether effects on the reactivity of potassium and magnesium towards 1-bromo-2-(3-butenyl)benzene. The incidence of homogeneous versus heterogeneous electron transfer on selectivity. J PHYS ORG CHEM 2005. [DOI: 10.1002/poc.986] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Asensio X, González-Lafont A, Marquet J, Lluch JM. A Theoretical Study of the Competitive Homolytic/Heterolytic Aniomesolytic Cleavages of C−O Alkyl Ether Bonds. J Org Chem 2004; 70:540-8. [PMID: 15651799 DOI: 10.1021/jo040208t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional theory electronic structure calculations of the homolytic/heterolytic aniomesolytic C-O fragmentations in the gas phase of a series of radical anions of substituted-phenyl benzyl ethers and substituted-benzyl phenyl ethers have been carried out. Along the series, the electron-withdrawing strength of the substituents increases. An intramolecular electron transfer from the pi system to the sigma molecular orbital of the scissile C-O bond is required to produce the fragmentation. As the electron-withdrawing strength of the substituents increases, the transition-state structures appear later with higher potential energy and Gibbs free energy barriers. The homolytic mesolytic cleavages are always thermodynamically favored versus the corresponding heterolytic mesolytic ones. The heterolytic mesolytic fragmentations in radical anions containing only weak electron-withdrawing groups are faster than the corresponding homolytic mesolytic ones. Conversely, in radical anions supporting strong electron-withdrawing groups the homolytic mesolytic fragmentations are faster in terms of potential energy barriers. However, the entropic contribution makes it comparable the homolytic and the heterolytic Gibbs free energy barriers in this case. The main factors that determine the relative rates of those kind of aniomesolytic cleavages are discussed.
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Affiliation(s)
- Xavier Asensio
- Departament de Química, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
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27
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Grobelny Z. Chemical Methods for Ether‐Bond Cleavage by Electron‐Transfer Reagents. European J Org Chem 2004. [DOI: 10.1002/ejoc.200400004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Zbigniew Grobelny
- Institute of Materials Science, University of Silesia, 40‐007 Katowice, Poland, Fax: + 48‐32‐2596929
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Reductive lithiation of cyclic benzofused ethers: a source of oxygen-functionalised organolithium compounds. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(02)00434-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Pisano L, Farriol M, Asensio X, Gallardo I, González-Lafont A, Lluch JM, Marquet J. Thermodynamics, kinetics, and dynamics of the two alternative aniomesolytic fragmentations of C-O bonds: an electrochemical and theoretical study. J Am Chem Soc 2002; 124:4708-15. [PMID: 11971720 DOI: 10.1021/ja012444g] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fragmentation reactions of radical anions (mesolytic cleavages) of cyanobenzyl alkyl ethers (intramolecular dissociative electron transfer, heterolytic cleavages) have been studied electrochemically. The intrinsic barriers for the processes have been established from the experimental thermodynamic and kinetic parameters. These values are more than 3 kcal/mol lower as an average than the related homolytic mesolytic fragmentations of radical anions of 4-cyanophenyl ethers. In the particular case of isomers 4-cyanobenzyl phenyl ether and 4-cyanophenyl benzyl ether, the difference in intrinsic barriers amounts to 5.5 kcal/mol, and this produces an energetic crossing where the thermodynamically more favorable process (homolytic) is the kinetically slower one. The fundamental reasons for this behavior have been established by means of theoretical calculations within the density functional theory framework, showing that, in this case, the factors that determine the kinetics are clearly different (mainly present in the transition state) from those that determine the thermodynamics and they are not related to the regioconservation of the spin density ("spin regioconservation principle"). Our theoretical results reproduce quite well the experimental energetic difference of barriers and demonstrate the main structural origin of the difference.
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Affiliation(s)
- Luisa Pisano
- Departament de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
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Gallardo I, Guirado G, Marquet J. Nucleophilic aromatic substitution for heteroatoms: an oxidative electrochemical approach. J Org Chem 2002; 67:2548-55. [PMID: 11950300 DOI: 10.1021/jo010847t] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The nucleophilic aromatic substitution for heteroatom through electrochemical oxidation of the intermediate sigma-complexes (Meisenheimer complexes) in simple nitroaromatic compounds is reported for the first time (NASX process). The studies have been carried out with hydride, cyanide, fluoride, methoxy, and ethanethiolate anions and n-butylamine as a nucleophile, at the cyclic voltammetry (CV) and preparative electrolysis level. The cyclic voltammetry experiments allow for detection and characterization of the sigma-complexes and they have led us to a proposal for the mechanism of the oxidation step. Furthermore, the power of the CV technique in the analysis of the reaction mixture throughout the whole chemical and electrochemical process is described.
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Affiliation(s)
- Iluminada Gallardo
- Departament de Química, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Barcelona, Spain.
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Maran F, Wayner DD, Workentin MS. Kinetics and mechanism of the dissociative reduction of CX and XX bonds (X O, S). ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2001. [DOI: 10.1016/s0065-3160(01)36004-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
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Electrostatic and electrophilic catalysis in the reductive cleavage of alkyl aryl ethers. The influence of ion pairing on the regioselectivity. J Org Chem 2000; 65:322-31. [PMID: 10813937 DOI: 10.1021/jo991059v] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electrophilic and electrostatic catalysis have been identified as distinct contributions that affect the reactivity of radical anions in the reductive cleavage of alkyl aryl ethers. Two modes of mesolytic scission of these radical anions are possible: homolytic (dealkylation, a thermodynamically favored but kinetically forbidden process) and heterolytic (dealkoxylation). From our studies (alkali metal reductions, electrochemical studies, use of substrates with a preformed positive charge in certain positions of their structure) it can be concluded that the heterolytic scission is very much dependent on the electrophilic assistance by the counterion and it is only observed in contact ionic pairs with unsaturated cations (electrophilic catalysis). On the other hand, the homolytic scission is observed in solvent-separated ionic pairs, and it is especially efficient when the pair has a controlled topology with a tetralkylammonium cation (saturated cation) near the oxygen atom. The effect of the cation has, in this case, electrostatic origin (electrostatic catalysis), probably lowering the barrier of the intramolecular pi-sigma electron transfer process and thus reducing the kinetic control of the reaction in such a way that the thermodynamically more favorable process is produced.
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Single electron transfer reductive cleavage of the aryl-nitrogen bond in phenyl-substituted dimethylanilines. Tetrahedron Lett 1999. [DOI: 10.1016/s0040-4039(99)01758-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Gonzalez-Blanco R, Bourdelande JL, Marquet J. Effect of Topologically Controlled Coulombic Interactions on the Dynamic Behavior of Photoexcited Nitrophenyl Alkyl Ethers in the Presence of Tertiary Amines with Limited Motion Freedom. J Org Chem 1997. [DOI: 10.1021/jo961821i] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Roberto Gonzalez-Blanco
- Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
| | - José L. Bourdelande
- Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
| | - Jordi Marquet
- Department of Chemistry, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
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Bunnett JF, Jenvey J. Reactivity in Cleavage of Dimethoxybenzenes by Sodium in Liquid Ammonia. J Org Chem 1996; 61:8069-8073. [PMID: 11667790 DOI: 10.1021/jo960148u] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The sodium/liquid ammonia cleavage of the dimethoxybenzenes and related substances, reported in large part by Birch in 1947, has been re-examined with use of improved techniques. Remarkable patterns of reactivity (e.g., ortho > meta >> para) that he described are confirmed and extended. They are agreeably rationalized by means of a simple, approximate adaptation from MO theory.
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Affiliation(s)
- Joseph F. Bunnett
- Thimann Laboratories, University of California, Santa Cruz, California 95064
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Kadam SM, Nayak SK, Banerji A. Dramatic Influence of Nitrogen Heterocycles on the Activity of Low-Valent Titanium Reagent: An Improved One-Pot Synthesis of Phenanthrenes. SYNTHETIC COMMUN 1995. [DOI: 10.1080/00397919508010799] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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38
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Pierini AB, Duca JS, Baumgartner MT. On the fragmentation of haloaromatic radical anions and their orbital isomerism. A theoretical study. J Mol Struct 1994. [DOI: 10.1016/s0022-2860(10)80043-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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