51
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Bołt M, Hanek K, Żak P. Metal-free thioesterification of α,β-unsaturated aldehydes with thiols. Org Chem Front 2022. [DOI: 10.1039/d2qo00678b] [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
For the first time, the synthesis of thioesters starting from enals and thiols has been performed in the presence of a bulky N-heterocyclic carbene (NHC) as a catalyst.
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Affiliation(s)
- Małgorzata Bołt
- Department of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznańskiego 8, 61-614 Poznan, Poland
| | - Kamil Hanek
- Department of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznańskiego 8, 61-614 Poznan, Poland
| | - Patrycja Żak
- Department of Organometallic Chemistry, Faculty of Chemistry, Adam Mickiewicz University in Poznan, Uniwersytetu Poznańskiego 8, 61-614 Poznan, Poland
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52
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Li Y, Geng L, Song Z, Zhang Z. A DFT study of NHC-catalyzed reactions between 2-bromo-2-enals and acylhydrazones: mechanisms, and chemo- and stereoselectivities. NEW J CHEM 2022. [DOI: 10.1039/d2nj01078j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The reaction mechanisms and origins of the chemo- and stereoselectivities of NHC-catalyzed [4 + 2] annulation of 2-bromo-2-enals and acylhydrazones.
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Affiliation(s)
- Yan Li
- School of Chemical Engineering, University of Science and Technology Liaoning, Anshan, 114051, P. R. China
| | - Lina Geng
- School of Chemical Engineering, University of Science and Technology Liaoning, Anshan, 114051, P. R. China
| | - Zhiyi Song
- School of Chemical Engineering, University of Science and Technology Liaoning, Anshan, 114051, P. R. China
| | - Zhiqiang Zhang
- School of Chemical Engineering, University of Science and Technology Liaoning, Anshan, 114051, P. R. China
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53
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Abstract
Biocatalysis has an enormous impact on chemical synthesis. The waves in which biocatalysis has developed, and in doing so changed our perception of what organic chemistry is, were reviewed 20 and 10 years ago. Here we review the consequences of these waves of development. Nowadays, hydrolases are widely used on an industrial scale for the benign synthesis of commodity and bulk chemicals and are fully developed. In addition, further enzyme classes are gaining ever increasing interest. Particularly, enzymes catalysing selective C-C-bond formation reactions and enzymes catalysing selective oxidation and reduction reactions are solving long-standing synthetic challenges in organic chemistry. Combined efforts from molecular biology, systems biology, organic chemistry and chemical engineering will establish a whole new toolbox for chemistry. Recent developments are critically reviewed.
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Affiliation(s)
- Ulf Hanefeld
- Biocatalysis, Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, The Netherlands.
| | - Frank Hollmann
- Biocatalysis, Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, The Netherlands.
| | - Caroline E Paul
- Biocatalysis, Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, The Netherlands.
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54
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Hsieh MH, Yu JSK. Fragmentation and rearrangement of Breslow intermediates: branches to both radical and ionic pathways. Phys Chem Chem Phys 2021; 23:27377-27384. [PMID: 34854852 DOI: 10.1039/d1cp03118j] [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
Breslow intermediates are the key species in N-heterocyclic carbene-catalyzed reactions to promote the C-C bond formation. As the fragmentation and rearrangement of Breslow intermediates terminate the catalytic cycle of N-heterocyclic carbene, two mechanisms under debate have been proposed in terms of the radical channel and the ionic route. Theoretical calculations demonstrate herein that ionic and radical characteristics can coexist, depending on the protonation state of the hydroxyl group in Breslow intermediates: radicals are merely generated in the enol system, while both ionic and radical species exist in the enolate system with a lower barrier. Complete pathways for thiamin analogue and N-allyl benzothiazole Breslow intermediates are exclusively constructed considering experimental conditions. The growing population of the enolate under higher pH values rationalizes the increased rate of the fragmentation of thiamin. The fragmentation products of thiamin, namely pyrimidine and ketone, are the thermodynamic products, while the tertiary alcohol is both the kinetic and thermodynamic product for N-allyl benzothiazole Breslow intermediate via a Claisen-like rearrangement. Other NHCs used to synthesize tertiary alcohols could form the enolate due to the base, followed by the production of stable radicals and recombination to form tertiary alcohols. It is concluded that specific protonation states and chemical structures of NHCs account for the distinct mechanisms.
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Affiliation(s)
- Ming-Hsiu Hsieh
- Institute of Bioinformatics and Systems Biology, National Yang Ming Chiao Tung University, No. 75, Bo'ai St., Hsinchu 300, Taiwan
| | - Jen-Shiang K Yu
- Institute of Bioinformatics and Systems Biology, Department of Biological Science and Technology, Institute of Molecular Medicine and Bioengineering, and Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung University, No. 75, Bo'ai St., Hsinchu 300, Taiwan.
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55
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Delfau L, Nichilo S, Molton F, Broggi J, Tomás‐Mendivil E, Martin D. Critical Assessment of the Reducing Ability of Breslow-type Derivatives and Implications for Carbene-Catalyzed Radical Reactions*. Angew Chem Int Ed Engl 2021; 60:26783-26789. [PMID: 34651408 PMCID: PMC9299025 DOI: 10.1002/anie.202111988] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Indexed: 01/05/2023]
Abstract
We report the synthesis of acyl azolium salts stemming from thiazolylidenes CNS , triazolylidenes CTN, mesoionic carbenes CMIC and the generation of their corresponding radicals and enolates, covering about 60 Breslow-type derivatives. This study highlights the role of additives in the redox behavior of these compounds and unveils several critical misconceptions about radical transformations of aldehyde derivatives under N-heterocyclic carbene catalysis. In particular, the reducing ability of enolates has been dramatically underestimated in the case of biomimetic CNS . In contrast with previous electrochemical studies, we show that these catalytic intermediates can transfer electrons to iodobenzene within minutes at room temperature. Enols derived from CMIC are not the previously claimed super electron donors, although enolate derivatives of CNS and CMIC are powerful reducing agents.
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Affiliation(s)
| | | | | | - Julie Broggi
- Aix Marseille UnivCNRSInstitut de Chimie Radicalaire (ICR)27 Bd Jean Moulin13385MarseilleFrance
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56
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Delfau L, Nichilo S, Molton F, Broggi J, Tomás‐Mendivil E, Martin D. Critical Assessment of the Reducing Ability of Breslow‐type Derivatives and Implications for Carbene‐Catalyzed Radical Reactions**. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202111988] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
| | | | | | - Julie Broggi
- Aix Marseille Univ CNRS Institut de Chimie Radicalaire (ICR) 27 Bd Jean Moulin 13385 Marseille France
| | | | - David Martin
- Univ. Grenoble Alpes CNRS DCM 38000 Grenoble France
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57
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Nandi A, Alassad Z, Milo A, Kozuch S. Quantum Tunneling on Carbene Organocatalysis: Breslow Intermediate Formation via Water-Bridges. ACS Catal 2021. [DOI: 10.1021/acscatal.1c04475] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Ashim Nandi
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Zayed Alassad
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel
| | - Anat Milo
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel
| | - Sebastian Kozuch
- Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva 841051, Israel
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58
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Sunoj RB. Coming of Age of Computational Chemistry from a Resilient Past to a Promising Future. Isr J Chem 2021. [DOI: 10.1002/ijch.202100106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Raghavan B. Sunoj
- Department of Chemistry Indian Institute of Technology Bombay, Powai Mumbai 400076 India
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59
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Pei Z, Qiao Q, Gong C, Wei D, Coote ML. Electrostatic effects in N-heterocyclic carbene catalysis: revealing the nature of catalysed decarboxylation. Phys Chem Chem Phys 2021; 23:24627-24633. [PMID: 34719698 DOI: 10.1039/d1cp04444c] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Quantum chemistry is used to investigate the nature of protonated N-heterocyclic carbene (NHC·H+) catalysed decarboxylation recently reported by Zhang et al. (ACS Catal., 2021, 11, 3443-3454). Our results show that there are strong electrostatic effects within the NHC·H+ catalysed decarboxylation, and these dominate hydrogen bonding. At the same time, energy decomposition analyses and comparison between the original NHC·H+ catalyst and a truncated form reveal that stabilizing dispersion interactions are also critical, as is induction. We also show that the electrostatic effects and their associated catalytic effects can be further enhanced using charged functional groups.
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Affiliation(s)
- Zhipeng Pei
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
| | - Qinyu Qiao
- Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, China.
| | - Cunxi Gong
- Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, China.
| | - Donghui Wei
- Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, China.
| | - Michelle L Coote
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
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60
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Hsieh M, Huang G, Yu JK. Dipole‐bound states and substituent effects of Breslow intermediates in the enolate form. J CHIN CHEM SOC-TAIP 2021. [DOI: 10.1002/jccs.202100310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Ming‐Hsiu Hsieh
- Institute of Bioinformatics and Systems Biology National Yang Ming Chiao Tung University Hsinchu Taiwan
| | - Gou‐Tao Huang
- Department of Biological Science and Technology National Yang Ming Chiao Tung University Hsinchu Taiwan
| | - Jen‐Shiang K. Yu
- Institute of Bioinformatics and Systems Biology, Department of Biological Science and Technology, and Institute of Molecular Medicine and Bioengineering National Yang Ming Chiao Tung University Hsinchu Taiwan
- Center for Intelligent Drug Systems and Smart Bio‐Devices National Yang Ming Chiao Tung University Hsinchu Taiwan
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61
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Nechaev MS. Tetrylenes: Electronic Structure, Stability, Reactivity, and Ligand Properties—A Comparative DFT Study. Organometallics 2021. [DOI: 10.1021/acs.organomet.1c00440] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mikhail S. Nechaev
- A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow 119991, Russia
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62
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Triazolium Salt Organocatalysis: Mechanistic Evaluation of Unusual Ortho-Substituent Effects on Deprotonation. Catalysts 2021. [DOI: 10.3390/catal11091055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Organocatalysis by N-heterocyclic carbenes is normally initiated by the deprotonation of precursor azolium ions to form active nucleophilic species. Substituent effects on deprotonation have an impact on catalytic efficiency and provide insight into general catalytic mechanisms by commonly used azolium systems. Using an NMR kinetic method for the analysis of C(3)-H/D exchange, we determined log kex–pD profiles for three ortho-substituted N-aryl triazolium salts, which enables a detailed analysis of ortho-substituent effects on deprotonation. This includes N-5-methoxypyrid-2-yl triazolium salt 7 and di-ortho-methoxy and di-ortho-isopropoxyphenyl triazolium salts 8 and 9, and we acquired additional kinetic data to supplement our previously published analysis of N-pyrid-2-yl triazolium salt 6. For 2-pyridyl triazoliums 6 and 7, novel acid catalysis of C(3)-H/D exchange is observed under acidic conditions. These kinetic data were supplemented by DFT analyses of the conformational preferences of 6 upon N-protonation. A C(3) deprotonation mechanism involving intramolecular general base deprotonation by the pyridyl nitrogen of the N(1)-deuterated dicationic triazolium salt is most consistent with the data. We also report kDO values (protofugalities) for deuteroxide-catalyzed exchange for 6–9. The protofugalities for 8 and 9 are the lowest values to date in the N-aryl triazolium series.
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