1
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Hanek K, Żak P. Eco-Friendly Functionalization of Ynals with Thiols under Mild Conditions. Int J Mol Sci 2024; 25:9201. [PMID: 39273150 PMCID: PMC11395323 DOI: 10.3390/ijms25179201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2024] [Revised: 08/21/2024] [Accepted: 08/23/2024] [Indexed: 09/15/2024] Open
Abstract
A new eco-friendly method for the synthesis of mono- and multifunctional organosulfur compounds, based on the process between ynals and thiols, catalyzed by bulky N-heterocyclic carbene (NHC), was designed and optimized. The proposed organocatalytic approach allows the straightforward formation of a broad range of thioesters and sulfenyl-substituted aldehydes in yields above 86%, in mild and metal-free conditions. In this study, thirty-six sulfur-based derivatives were obtained and characterized by spectroscopic methods.
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Affiliation(s)
- Kamil Hanek
- Faculty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego St. 8, 61-614 Poznan, Poland
| | - Patrycja Żak
- Faculty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego St. 8, 61-614 Poznan, Poland
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2
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Mermela A, Bołt M, Mrzygłód A, Żak P. Organocatalytic synthetic route to esters and their application in hydrosilylation process. Sci Rep 2024; 14:19108. [PMID: 39154105 PMCID: PMC11330490 DOI: 10.1038/s41598-024-70036-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 08/08/2024] [Indexed: 08/19/2024] Open
Abstract
A facile esterification of α,β-unsaturated aldehydes with alcohols has been developed for the synthesis of esters by using bulky N-heterocyclic (NHC) carbene as a metal-free and eco-friendly organocatalyst. This new protocol has been proved to be effective with a wide substrate scope, giving selective esters in yields greater than 84% under mild conditions. Moreover, proposed synthetic strategy enables modification of various types of silsesquioxanes (SQ) which cannot or are technically difficult to be carried out with known protocols. For the first time, a one-pot sequential esterification/hydrosilylation has been successfully carried out.
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Affiliation(s)
- Aleksandra Mermela
- Faculty of Chemistry, Department of Organometallic Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614, Poznań, Poland
| | - Małgorzata Bołt
- Faculty of Chemistry, Department of Organometallic Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614, Poznań, Poland
| | - Aleksandra Mrzygłód
- Faculty of Chemistry, Department of Organometallic Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614, Poznań, Poland
- Centre for Advanced Technologies, Uniwersytetu Poznańskiego 10, 61-614, Poznań, Poland
| | - Patrycja Żak
- Faculty of Chemistry, Department of Organometallic Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, 61-614, Poznań, Poland.
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3
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Huang GT, Yu JSK. Catalytic role of the enol ether intermediate in the intramolecular Stetter reaction: a computational perspective. Phys Chem Chem Phys 2024; 26:11833-11853. [PMID: 38567403 DOI: 10.1039/d3cp06051a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The intramolecular Stetter reaction catalyzed by a carbene is investigated by density functional theory (DFT) calculations and kinetic simulations. Catalyst 1 first reacts with aldehyde 2 to give the primary adduct (PA). The PA undergoes the intramolecular oxa-Michael reaction to irreversibly generate enol ether intermediate 9. The conversion of the enol ether to the Breslow intermediate (BI) requires the assistance of a base such as the PA. The next step involves formation of a carbon-carbon bond through the Michael addition, and expulsion of the catalyst generates the Stetter product 7. Calculations show that the catalytic cycle is composed of two irreversible processes: the first one involves the exergonic formation of the enol ether intermediate, while the second one is the conversion of the enol ether to the final product. Kinetic simulations using initial concentrations of [1]0 = 0.005 M and [2]0 = 0.025 M demonstrate that under a steady-state condition, 35% of the catalyst rests on the state of the enol ether (0.0018 M). The catalyst resting state therefore consists of the unbound form (the free catalyst) and its bound form (the enol ether species). According to variable time normalization analysis, the reaction exhibits a second-order dependence (first order in catalyst and first order in substrate), which agrees with experiments. The oxa-Michael reaction to form the enol ether is identified to be turnover limiting in the intramolecular Stetter reaction, which rationalizes the observed electronic effect of the Michael acceptor on the reactivity, as well as the measured isotope effect with respect to the aldehydic proton/deuteron. The base that participates in the BI formation has a significant effect on the build-up of the resting state 9 and the active catalyst concentration. In addition, the thermodynamic stability of the enol ether is found to depend on the tether length between the aromatic aldehyde and the Michael acceptor, as well as the chemical nature of the carbene catalyst. The favorability for the oxa-Michael reaction is therefore suggested to govern the reactivity of the intramolecular Stetter transformation.
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Affiliation(s)
- Gou-Tao Huang
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu City 300, Taiwan.
| | - Jen-Shiang K Yu
- Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu City 300, Taiwan.
- Institute of Bioinformatics and Systems Biology, National Yang Ming Chiao Tung University, Hsinchu City 300, Taiwan
- Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung University, Hsinchu City 300, Taiwan
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4
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Aysin RR, Galkin KI. Adaptive carbonyl umpolung involving a carbanionic carbene Breslow intermediate: an alternative mechanism for NHC-mediated organocatalysis. Org Biomol Chem 2023; 21:8702-8707. [PMID: 37867444 DOI: 10.1039/d3ob01195j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2023]
Abstract
Herein, we propose a novel mechanistic model for NHC-mediated carbonyl umpolung which involves the formation of a carbanionic carbene Breslow intermediate (CCBI). We have demonstrated theoretically that this reactive intermediate can be formed by inserting an aldehyde into the C4-H position of an N-aryl-substituted imidazolium-derived NHC via the generation of an H-bonded ditopic carbanionic NHC (dcNHC). Our DFT study on benzoin condensation has revealed that the mechanism of polarity inversion proceeding through the CCBI may be more energetically favorable than the classical mechanism of umpolung that uses the C2 carbene position in NHC. The potential existence of the CCBI highlights the dynamic and adaptive nature of NHC-mediated organocatalysis, particularly in relation to carbonyl umpolung. This finding also sheds light on new pathways in organocatalytic transformations employing the ambident reactivity of NHC, which may be particularly attractive for reactions involving furanic aldehydes and sterically encumbered N-aryl-substituted carbenes.
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Affiliation(s)
- Rinat R Aysin
- Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ul. Vavilova, 28, 119991 Moscow, Russia
| | - Konstantin I Galkin
- Bauman Moscow State Technical University, 2nd Baumanskaya ul., 5/1, 105005 Moscow, Russia.
- Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, ul. Leninsky Prospekt, 47, 119991, Moscow, Russia
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5
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Mulks FF, Melaimi M, Yan X, Baik MH, Bertrand G. How To Enhance the Efficiency of Breslow Intermediates for SET Catalysis. J Org Chem 2023; 88:2535-2542. [PMID: 36719963 DOI: 10.1021/acs.joc.2c02978] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Oxidative carbene organocatalysis, which proceeds via single electron transfer (SET) pathways, has been limited by the moderately reducing properties of deprotonated Breslow intermediates BI-s derived from thiazol-2-ylidene 1 and 1,2,4-triazolylidene 2. Using computational methods, we assess the redox potentials of BI-s based on ten different types of known stable carbenes and report our findings concerning the key parameters influencing the steps of the catalytic cycle. From the calculated values of the first oxidation potential of BI-s derived from carbenes 1 to 10, it appears that, apart from the diamidocarbene 7, all the others are more reducing than thiazol-2-ylidene 1 and the 1,2,4-triazolylidene 2. We observed that while the reducing power of BI-s significantly decreases with increasing solvent polarity, the redox potential of the oxidant can increase at a greater rate, thus facilitating the reaction. The cation, associated with the base, also plays an important role when a nonpolar solvent is used; large and weakly coordinating cations such as Cs+ are beneficial. The radical-radical coupling step is probably the most challenging step due to both electronic and steric constraints. Based on our results, we predict that mesoionic carbene 3 and abnormal NHC 4 are the most promising candidates for oxidative carbene organocatalysis.
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Affiliation(s)
- Florian F Mulks
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea.,Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.,UCSD-CNRS Joint Research Chemistry Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358, United States
| | - Mohand Melaimi
- UCSD-CNRS Joint Research Chemistry Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358, United States
| | - Xiaoyu Yan
- Department of Chemistry, Renmin University of China, Beijing 100872, People's Republic of China
| | - Mu-Hyun Baik
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea.,Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea
| | - Guy Bertrand
- UCSD-CNRS Joint Research Chemistry Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358, United States
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6
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De Risi C, Brandolese A, Di Carmine G, Ragno D, Massi A, Bortolini O. Oxidative N-Heterocyclic Carbene Catalysis. Chemistry 2023; 29:e202202467. [PMID: 36205918 PMCID: PMC10099058 DOI: 10.1002/chem.202202467] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Indexed: 11/05/2022]
Abstract
N-Heterocyclic carbene (NHC) catalysis is a by now consolidated organocatalytic platform for a number of synthetic (asymmetric) transformations via diverse reaction modes/intermediates. In addition to the typical umpolung processes involving acyl anion/homoenolate equivalent species, implementation of protocols under oxidative conditions greatly expands the possibilities of this methodology. Oxidative NHC-catalysis allows for oxidative and oxygenative transformations through specific manipulations of Breslow-type species depending upon the oxidant used (external oxidant or O2 /air), the derived NHC-bound intermediates paving the way to non-umpolung processes through activation of carbon atoms and heteroatoms. This review is intended to update the state of the art in oxidative NHC-catalyzed reactions that appeared in the literature from 2014 to present, with a strong focus to crucial intermediates and their mechanistic implications.
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Affiliation(s)
- Carmela De Risi
- Dipartimento di Scienze Chimiche, Farmaceutiche ed AgrarieUniversità di FerraraVia L. Borsari, 4644121FerraraItaly
| | - Arianna Brandolese
- Dipartimento di Scienze dell'Ambiente e della PrevenzioneUniversità di FerraraVia L. Borsari, 4644121FerraraItaly
| | - Graziano Di Carmine
- Dipartimento di Scienze Chimiche, Farmaceutiche ed AgrarieUniversità di FerraraVia L. Borsari, 4644121FerraraItaly
| | - Daniele Ragno
- Dipartimento di Scienze Chimiche, Farmaceutiche ed AgrarieUniversità di FerraraVia L. Borsari, 4644121FerraraItaly
| | - Alessandro Massi
- Dipartimento di Scienze Chimiche, Farmaceutiche ed AgrarieUniversità di FerraraVia L. Borsari, 4644121FerraraItaly
| | - Olga Bortolini
- Dipartimento di Scienze dell'Ambiente e della PrevenzioneUniversità di FerraraVia L. Borsari, 4644121FerraraItaly
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7
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Duan Z, Young CM, Zhu J, Slawin AMZ, O'Donoghue AC, Smith AD. Rate and equilibrium constants for the addition of triazolium salt derived N-heterocyclic carbenes to heteroaromatic aldehydes. Chem Sci 2022; 14:162-170. [PMID: 36605738 PMCID: PMC9769090 DOI: 10.1039/d2sc05704b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 11/13/2022] [Indexed: 11/16/2022] Open
Abstract
Heteroaromatic aldehydes are often used preferentially or exclusively in a range of NHC-catalysed processes that proceed through the generation of a reactive diaminoenol or Breslow Intermediate (BI), with the reason for their unique reactivity currently underexplored. This manuscript reports measurement of rate and equilibrium constants for the reaction between N-aryl triazolium NHCs and heteroaromatic aldehydes, providing insight into the effect of the NHC and heteroaromatic aldehyde structure up to formation of the BI. Variation in NHC catalyst and heteroaromatic aldehyde structure markedly affect the observed kinetic parameters of adduct formation, decay to starting materials and onward reaction to BI. In particular, large effects are observed with both 3-halogen (Br, F) and 3-methyl substituted pyridine-2-carboxaldehyde derivatives which substantially favour formation of the tetrahedral intermediate relative to benzaldehyde derivatives. Key observations indicate that increased steric hindrance leads to a reduction in both k 2 and k -1 for large (2,6-disubstituted)-N-Ar groups within the triazolium scaffold, and sterically demanding aldehyde substituents in the 3-position, but not in the 6-position of the pyridine-2-carboxaldehyde derivatives. As part of this study, the isolation and characterisation of twenty tetrahedral adducts formed upon addition of N-aryl triazolium derived NHCs into heteroaromatic aldehydes are described. These adducts are key intermediates in NHC-catalysed umpolung addition of heteroaromatic aldehydes and are BI precursors.
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Affiliation(s)
- Zhuan Duan
- EaStCHEM, School of Chemistry, University of St Andrews North Haugh St Andrews Fife KY16 9ST UK
| | - Claire M Young
- EaStCHEM, School of Chemistry, University of St Andrews North Haugh St Andrews Fife KY16 9ST UK
| | - Jiayun Zhu
- Department of Chemistry, Durham University South Road Durham DH1 3LE UK
| | - Alexandra M Z Slawin
- EaStCHEM, School of Chemistry, University of St Andrews North Haugh St Andrews Fife KY16 9ST UK
| | | | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St Andrews North Haugh St Andrews Fife KY16 9ST UK
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8
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Rowshanpour R, Gravel M, Dudding T. N-Heterocyclic Carbene Organocatalyzed Redox-Active/Ring Expansion Reactions: Mechanistic Insights Unveiling Base Cooperativity. J Org Chem 2022; 87:16785-16793. [DOI: 10.1021/acs.joc.2c02462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- Rozhin Rowshanpour
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S3A1, Canada
| | - Michel Gravel
- Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan S7N5C9, Canada
| | - Travis Dudding
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S3A1, Canada
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9
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Wang Z, Yang T, Liu D, Chen R, Wang N, Liu H, Li J, Wang K, Liu H. Catalyst-Controlled Selectivity Switch in Three-Component Reaction: An NHC-Catalyzed Strategy for the Synthesis of δ-Lactone-Fused Spirobenzofuran-3-ones. Molecules 2022; 27:5952. [PMID: 36144686 PMCID: PMC9503435 DOI: 10.3390/molecules27185952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 09/09/2022] [Accepted: 09/09/2022] [Indexed: 11/28/2022] Open
Abstract
An efficient, three-component reaction of aldehydes and benzofuran-3-ones was developed. This process provides a new approach for the preparation of synthetically and biologically important spirobenzofuran-3-one derivatives with moderate-to-good yields under mild conditions. A switch of intramolecular to intermolecular domino Michael-aldol-lactonization leading to differential product formation was achieved by different NHCs catalysis.
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Affiliation(s)
- Zhanyong Wang
- School of Pharmacy, Xinxiang University, Xinxiang 453003, China
| | - Ting Yang
- Nursing College, Xinxiang University, Xinxiang 453003, China
| | - Dongfang Liu
- Xinxiang Runyu Material Co., Ltd., Xinxiang 453003, China
| | - Rongxiang Chen
- School of Pharmacy, Xinxiang University, Xinxiang 453003, China
| | - Nan Wang
- School of Pharmacy, Xinxiang University, Xinxiang 453003, China
| | - Hong Liu
- School of Pharmacy, Xinxiang University, Xinxiang 453003, China
| | - Jiarong Li
- School of Pharmacy, Xinxiang University, Xinxiang 453003, China
| | - Kaikai Wang
- School of Pharmacy, Xinxiang University, Xinxiang 453003, China
| | - Hongxin Liu
- College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China
- Institute of New Materials & Industrial Technology, Wenzhou University, Wenzhou 325035, China
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10
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Wessels A, Klussmann M, Breugst M, Schlörer NE, Berkessel A. Formation of Breslow Intermediates from N‐Heterocyclic Carbenes and Aldehydes Involves Autocatalysis by the Breslow Intermediate, and a Hemiacetal. Angew Chem Int Ed Engl 2022; 61:e202117682. [PMID: 35238462 PMCID: PMC9325009 DOI: 10.1002/anie.202117682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Indexed: 11/23/2022]
Abstract
Under aprotic conditions, the stoichiometric reaction of N‐heterocyclic carbenes (NHCs) such as imidazolidin‐2‐ylidenes with aldehydes affords Breslow Intermediates (BIs), involving a formal 1,2‐C‐to‐O proton shift. We herein report kinetic studies (NMR), complemented by DFT calculations, on the mechanism of this kinetically disfavored H‐translocation. Variable time normalization analysis (VTNA) revealed that the kinetic orders of the reactants vary for different NHC‐to‐aldehyde ratios, indicating different and ratio‐dependent mechanistic regimes. We propose that for high NHC‐to‐aldehyde ratios, the H‐shift takes place in the primary, zwitterionic NHC‐aldehyde adduct. With excess aldehyde, the zwitterion is in equilibrium with a hemiacetal, in which the H‐shift occurs. In both regimes, the critical H‐shift is auto‐catalyzed by the BI. Kinetic isotope effects observed for R‐CDO are in line with our proposal. Furthermore, we detected an H‐bonded complex of the BI with excess NHC (NMR).
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Affiliation(s)
- Alina Wessels
- Department of Chemistry Organic Chemistry University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Martin Klussmann
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Germany
- Borchers GmbH Berghausener Straße 100 40764 Langenfeld Germany
| | - Martin Breugst
- Department of Chemistry Organic Chemistry University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Nils E. Schlörer
- Department of Chemistry Organic Chemistry University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Albrecht Berkessel
- Department of Chemistry Organic Chemistry University of Cologne Greinstraße 4 50939 Cologne Germany
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11
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Liu C, Han P, Zhang X, Qiao Y, Xu Z, Zhang Y, Li D, Wei D, Lan Y. NHC-Catalyzed Transformation Reactions of Imines: Electrophilic versus Nucleophilic Attack. J Org Chem 2022; 87:7989-7994. [PMID: 35618673 DOI: 10.1021/acs.joc.2c00621] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
It is generally accepted that N-heterocyclic carbene (NHC)-catalyzed imine transformations are initiated by a nucleophilic attack (NA) by NHC. However, due to significant nucleophilicity of the iminyl nitrogen atom in imines, the electrophilic attack (EA) by electrophiles onto imine would also be a possible mechanism of these kinds of reactions. Therefore, we use the quantum mechanical approach to disclose that both the NA and EA modes could be switchable for a wide range of NHC-catalyzed transformations of imines.
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Affiliation(s)
- Chunhui Liu
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Xuchang, Henan 461000, China
| | - Peilin Han
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Xuchang, Henan 461000, China
| | - Xusheng Zhang
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Xuchang, Henan 461000, China
| | - Yan Qiao
- Department of Pathophysiology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, Henan 450001, China
| | - Zhihong Xu
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Xuchang, Henan 461000, China
| | - Yange Zhang
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Xuchang, Henan 461000, China
| | - Dapeng Li
- Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, College of Chemical and Materials Engineering, Xuchang University, Xuchang, Henan 461000, China
| | - Donghui Wei
- Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, China
| | - Yu Lan
- Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou, Henan 450001, China.,School of Chemistry and Chemical Engineering, Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 400030, China
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12
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Wessels A, Klussmann M, Breugst M, Schlörer NE, Berkessel A. Die Bildung von Breslow‐Intermediaten aus N‐heterocyclischen Carbenen und Aldehyden verläuft autokatalytisch und mit einem Halbacetal als Intermediat. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202117682] [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)
- Alina Wessels
- Department für Chemie Organische Chemie Universität zu Köln Greinstraße 4 50939 Köln Deutschland
| | - Martin Klussmann
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Deutschland
- Borchers GmbH Berghausener Straße 100 40764 Langenfeld Deutschland
| | - Martin Breugst
- Department für Chemie Organische Chemie Universität zu Köln Greinstraße 4 50939 Köln Deutschland
| | - Nils E. Schlörer
- Department für Chemie Organische Chemie Universität zu Köln Greinstraße 4 50939 Köln Deutschland
| | - Albrecht Berkessel
- Department für Chemie Organische Chemie Universität zu Köln Greinstraße 4 50939 Köln Deutschland
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13
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Chen Y, Lv J, Pan X, Jin Z. An Unexpected Inactivation of N-Heterocyclic Carbene Organic Catalyst by 1-Methylcyclopropylcarbaldehyde and 2,2,2-Trifluoroacetophenone. Front Chem 2022; 10:875286. [PMID: 35402372 PMCID: PMC8988059 DOI: 10.3389/fchem.2022.875286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 02/18/2022] [Indexed: 12/01/2022] Open
Abstract
An unprecedented inactivation process of the indanol-derived NHC catalysts bearing N-C6F5 groups is reported. An unexpected multi-cyclic complex product is obtained from the 3-component reaction with the 1-methylcyclopropyl-carbaldehyde, the 2,2,2-trifluoroacetophenone and the NHC catalyst. The absolute structure of the inactivation product is unambiguously assigned via X-ray analysis on its single crystals. The formation of the structurally complex product is rationalized through a multi-step cascade cyclization process.
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14
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Huang GT, Hsieh MH, Yu JSK. Formation of Breslow Intermediates under Aprotic Conditions: A Computational Study. J Org Chem 2022; 87:2501-2507. [PMID: 35029105 DOI: 10.1021/acs.joc.1c02408] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mechanism of formation of the Breslow intermediate (BI) under aprotic conditions is investigated with density functional theory (DFT) calculations. The zwitterionic adduct (ZA) is formed by the first addition of an imidazolinylidene to benzaldehyde. The forward reaction is found to proceed through the second addition of the ZA to another benzaldehyde, and subsequent proton migration gives a hemiacetal. The bimolecular reaction enables the conversion of the ZA to a more reactive hemiacetal, which is further decomposed to the BI with the assistance of the ZA. During the ZA-assisted process, the hemiacetal and the BI act as hydrogen bond donors to stabilize the ZA. The hydrogen bond interactions between the ZA and the BI or hemiacetal are analyzed. The DFT computations demonstrate that along the proposed route, the proton migration leading to the hemiacetal intermediate is the rate-determining step (ΔG⧧ = 21.2 kcal mol-1). The bimolecular mechanism provides an alternative pathway to explain BI formation under aprotic conditions.
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15
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Golub T, Kano T, Maruoka K, Merten C. VCD spectroscopy distinguishes the enamine and iminium ion of a 1,1’-binaphthyl azepine. Chem Commun (Camb) 2022; 58:8412-8415. [DOI: 10.1039/d2cc02863h] [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
We present a VCD spectroscopic characterization of a chiral 1,1’-binaphthyl azepine catalyst and show that the VCD spectra of an in-situ generated enamine and an ex-situ prepared iminium ion are...
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16
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Abstract
An efficient construction of amides through NHC-mediated oxidation of imines is described. This work has the advantages of wide scope, fast assembly and high yield, and can avoid the use of coupling agents, such as HATU, DCC, etc.
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Affiliation(s)
- Shaofa Sun
- College of Chemistry and Biological Sciences, Hubei University of Science and Technology, Hubei, 437100, China
| | - Donghui Guo
- School of Pharmaceutical Sciences, Tsinghua University, Beijing 100084, P. R. China
| | - Fangyi Li
- School of Pharmaceutical Sciences, Tsinghua University, Beijing 100084, P. R. China
| | - Jian Wang
- College of Chemistry and Biological Sciences, Hubei University of Science and Technology, Hubei, 437100, China
- School of Pharmaceutical Sciences, Tsinghua University, Beijing 100084, P. R. China
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17
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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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18
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Fajardo AM, Queyraiux N, Camy A, Vendier L, Grellier M, Del Rosal I, Maron L, Bontemps S. A masked form of an O-borylated Breslow intermediate for the diastereoselective FLP-type activation of aldehydes. Chemistry 2021; 28:e202104122. [PMID: 34964516 DOI: 10.1002/chem.202104122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Indexed: 11/07/2022]
Abstract
Breslow intermediates are very often elusive species whose application in Frustrated Lewis Pair chemistry is unprecedented. We describe herein the use of a masked form of an O-Borylated Breslow (OBB) intermediate that performs FLP-type activation of the carbonyl function of five different benzaldehyde derivatives with complete diastereoselectivity. The resulting compounds are characterised in solution by NMR spectroscopy (compounds 4 - 8 ) and in solid state by X-Ray diffraction analysis (compounds 4 - 6 ). A combined kinetic and theoretical investigation reveals the associative nature of the rate determining step and suggests that the OBB intermediate part is never released during the whole process.
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Affiliation(s)
| | | | - Aurèle Camy
- Laboratoire de Chimie de Coordination, chemistry, FRANCE
| | - Laure Vendier
- Laboratoire de Chimie de Coordination, chemistry, FRANCE
| | - Mary Grellier
- Laboratoire de Chimie de Coordination, chemistry, FRANCE
| | - Iker Del Rosal
- LPCNO: Laboratoire de physique et chimie des nano-objets, chemistry, FRANCE
| | - Laurent Maron
- LPCNO: Laboratoire de physique et chimie des nano-objets, chemistry, FRANCE
| | - Sébastien Bontemps
- Centre National de la Recherche Scientifique, Laboratoire de Chimie de Coordination, 205 route de Narbonne, 31077 cedex 04, toulouse, FRANCE
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19
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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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20
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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: 42] [Impact Index Per Article: 14.0] [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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21
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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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22
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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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23
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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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24
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Harnying W, Sudkaow P, Biswas A, Berkessel A. N-Heterocyclic Carbene/Carboxylic Acid Co-Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading. Angew Chem Int Ed Engl 2021; 60:19631-19636. [PMID: 34010504 PMCID: PMC8457137 DOI: 10.1002/anie.202104712] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/10/2021] [Indexed: 01/07/2023]
Abstract
We report the discovery that simple carboxylic acids, such as benzoic acid, boost the activity of N-heterocyclic carbene (NHC) catalysts in the oxidative esterification of aldehydes. A simple and efficient protocol for the transformation of a wide range of sterically hindered α- and β-substituted aliphatic aldehydes/enals, catalyzed by a novel and readily accessible N-Mes-/N-2,4,6-trichlorophenyl 1,2,4-triazolium salt, and benzoic acid as co-catalyst, was developed. A whole series of α/β-substituted aliphatic aldehydes/enals hitherto not amenable to NHC-catalyzed esterification could be reacted at typical catalyst loadings of 0.02-1.0 mol %. For benzaldehyde, even 0.005 mol % of NHC catalyst proved sufficient: the lowest value ever achieved in NHC catalysis. Preliminary studies point to carboxylic acid-induced acceleration of acyl transfer from azolium enolate intermediates as the mechanistic basis of the observed effect.
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Affiliation(s)
- Wacharee Harnying
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
| | - Panyapon Sudkaow
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
| | - Animesh Biswas
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
| | - Albrecht Berkessel
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
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25
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Harnying W, Sudkaow P, Biswas A, Berkessel A. N‐Heterocyclic Carbene/Carboxylic Acid Co‐Catalysis Enables Oxidative Esterification of Demanding Aldehydes/Enals, at Low Catalyst Loading. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202104712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Wacharee Harnying
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Panyapon Sudkaow
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Animesh Biswas
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Albrecht Berkessel
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
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26
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Kyan R, Kitagawa Y, Ide R, Sato K, Mase N, Narumi T. β,γ-trans-selective γ-butyrolactone formation via homoenolate cross-annulation of enals and aldehydes catalyzed by sterically hindered N-heterocyclic carbene. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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27
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Pareek M, Reddi Y, Sunoj RB. Tale of the Breslow intermediate, a central player in N-heterocyclic carbene organocatalysis: then and now. Chem Sci 2021; 12:7973-7992. [PMID: 34194690 PMCID: PMC8208132 DOI: 10.1039/d1sc01910d] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 04/28/2021] [Indexed: 12/27/2022] Open
Abstract
N-Heterocyclic carbenes (NHCs) belong to the popular family of organocatalysts used in a wide range of reactions, including that for the synthesis of complex natural products and biologically active compounds. In their organocatalytic manifestation, NHCs are known to impart umpolung reactivity to aldehydes and ketones, which are then exploited in the generation of homoenolate, acyl anion, and enolate equivalents suitable for a plethora of reactions such as annulation, benzoin, Stetter, Claisen rearrangement, cycloaddition, and C-C and C-H bond functionalization reactions and so on. A common thread that runs through these NHC catalyzed reactions is the proposed involvement of an enaminol, also known as the Breslow intermediate, formed by the nucleophilic addition of an NHC to a carbonyl group of a suitable electrophile. In the emerging years of NHC catalysis, enaminol remained elusive and was largely considered a putative intermediate owing to the difficulties encountered in its isolation and characterization. However, in the last decade, synergistic efforts utilizing an array of computational and experimental techniques have helped in gaining important insights into the formation and characterization of Breslow intermediates. Computational studies have suggested that a direct 1,2-proton transfer within the initial zwitterionic intermediate, generated by the action of an NHC on the carbonyl carbon, is energetically prohibitive and hence the participation of other species capable of promoting an assisted proton transfer is more likely. The proton transfer assisted by additives (such as acids, bases, other species, or even a solvent) was found to ease the kinetics of formation of Breslow intermediates. These important details on the formation, in situ detection, isolation, and characterization of the Breslow intermediate are scattered over a series of reports spanning well over a decade, and we intend to consolidate them in this review and provide a critical assessment of these developments. Given the central role of the Breslow intermediate in organocatalytic reactions, this treatise is expected to serve as a valuable source of knowledge on the same.
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Affiliation(s)
- Monika Pareek
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| | - Yernaidu Reddi
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
| | - Raghavan B Sunoj
- Department of Chemistry, Indian Institute of Technology Bombay Powai Mumbai 400076 India
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28
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Biswas A, Neudörfl JM, Schlörer NE, Berkessel A. Acyl Donor Intermediates in N-Heterocyclic Carbene Catalysis: Acyl Azolium or Azolium Enolate? Angew Chem Int Ed Engl 2021; 60:4507-4511. [PMID: 33140529 PMCID: PMC7986403 DOI: 10.1002/anie.202010348] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 10/20/2020] [Indexed: 11/23/2022]
Abstract
Azolium enolates and acyl azolium cations have been proposed as intermediates in numerous N‐heterocyclic carbene (NHC) catalyzed transformations. Acetyl azolium enolates were generated from the reaction of 2‐propenyl acetate with both saturated (SIPr) and aromatic (IPr) NHCs, isolated, and characterized (NMR, XRD). Protonation with triflic acid gave the corresponding acetyl azolium triflates which were isolated and characterized (NMR, XRD). Acyl azolium cations have been proposed as immediate precursors of the ester product, for example, in the redox esterification of α,β‐enals. Studies with d3‐acetyl azolium triflate suggest that ester formation originates instead from an azolium enolate intermediate. Furthermore, the acetyl azolium enolate selectively reacted with alcohol nucleophiles in the presence of amines. While the acetyl azolium cation did not react with alcohols, an ester‐selective reaction was induced by addition of base, by intermediate formation of the acetyl azolium enolate.
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Affiliation(s)
- Animesh Biswas
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
| | - Jörg-M Neudörfl
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
| | - Nils E Schlörer
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
| | - Albrecht Berkessel
- Department of Chemistry (Organic Chemistry), University of Cologne, Greinstraße 4, 50939, Cologne, Germany
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29
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Biswas A, Neudörfl J, Schlörer NE, Berkessel A. Acyl Donor Intermediates in N‐Heterocyclic Carbene Catalysis: Acyl Azolium or Azolium Enolate? Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202010348] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Animesh Biswas
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Jörg‐M. Neudörfl
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Nils E. Schlörer
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
| | - Albrecht Berkessel
- Department of Chemistry (Organic Chemistry) University of Cologne Greinstraße 4 50939 Cologne Germany
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30
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Paul M, Peckelsen K, Thomulka T, Martens J, Berden G, Oomens J, Neudörfl JM, Breugst M, Meijer AJHM, Schäfer M, Berkessel A. Breslow Intermediates (Amino Enols) and Their Keto Tautomers: First Gas-Phase Characterization by IR Ion Spectroscopy. Chemistry 2021; 27:2662-2669. [PMID: 32893891 PMCID: PMC7898712 DOI: 10.1002/chem.202003454] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 09/01/2020] [Indexed: 12/11/2022]
Abstract
Breslow intermediates (BIs) are the crucial nucleophilic amino enol intermediates formed from electrophilic aldehydes in the course of N-heterocyclic carbene (NHC)-catalyzed umpolung reactions. Both in organocatalytic and enzymatic umpolung, the question whether the Breslow intermediate exists as the nucleophilic enol or in the form of its electrophilic keto tautomer is of utmost importance for its reactivity and function. Herein, the preparation of charge-tagged Breslow intermediates/keto tautomers derived from three different types of NHCs (imidazolidin-2-ylidenes, 1,2,4-triazolin-5-ylidenes, thiazolin-2-ylidenes) and aldehydes is reported. An ammonium charge tag is introduced through the aldehyde unit or the NHC. ESI-MS IR ion spectroscopy allowed the unambiguous conclusion that in the gas phase, the imidazolidin-2-ylidene-derived BI indeed exists as a diamino enol, while both 1,2,4-triazolin-5-ylidenes and thiazolin-2-ylidenes give the keto tautomer. This result coincides with the tautomeric states observed for the BIs in solution (NMR) and in the crystalline state (XRD), and is in line with our earlier calculations on the energetics of BI keto-enol equilibria.
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Affiliation(s)
- Mathias Paul
- Department of Chemistry, Cologne University, Greinstrasse 4, 50939, Cologne, Germany
| | - Katrin Peckelsen
- Department of Chemistry, Cologne University, Greinstrasse 4, 50939, Cologne, Germany
| | - Thomas Thomulka
- Department of Chemistry, Cologne University, Greinstrasse 4, 50939, Cologne, Germany
| | - Jonathan Martens
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525, ED, Nijmegen, The Netherlands
| | - Giel Berden
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525, ED, Nijmegen, The Netherlands
| | - Jos Oomens
- Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525, ED, Nijmegen, The Netherlands.,Van' t Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Jörg-M Neudörfl
- Department of Chemistry, Cologne University, Greinstrasse 4, 50939, Cologne, Germany
| | - Martin Breugst
- Department of Chemistry, Cologne University, Greinstrasse 4, 50939, Cologne, Germany
| | | | - Mathias Schäfer
- Department of Chemistry, Cologne University, Greinstrasse 4, 50939, Cologne, Germany
| | - Albrecht Berkessel
- Department of Chemistry, Cologne University, Greinstrasse 4, 50939, Cologne, Germany
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31
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Messelberger J, Kumar M, Goodner SJ, Munz D. Wanzlick's equilibrium in tri- and tetraaminoolefins. Org Chem Front 2021. [DOI: 10.1039/d1qo01320c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
How to isolate small carbenes, previously reported to from dimers instantaneously, and how to split triaminoolefins into free carbenes.
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Affiliation(s)
- Julian Messelberger
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
| | - Manoj Kumar
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
| | - Stephen J. Goodner
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
- Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Chemistry and Pharmacy: Chair of Inorganic and General Chemistry, Egerlandstraße 1, D-91058 Erlangen, Germany
| | - Dominik Munz
- Saarland University, Inorganic Chemistry: Coordination Chemistry, Campus C4.1, D-66123 Saarbrücken, Germany
- Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Chemistry and Pharmacy: Chair of Inorganic and General Chemistry, Egerlandstraße 1, D-91058 Erlangen, Germany
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32
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Zhang Z, Huang S, Huang L, Xu X, Zhao H, Yan X. Synthesis of Mesoionic N-Heterocyclic Olefins and Catalytic Application for Hydroboration Reactions. J Org Chem 2020; 85:12036-12043. [DOI: 10.1021/acs.joc.0c00257] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Zengyu Zhang
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Shiqing Huang
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Linwei Huang
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Xingyu Xu
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Hongyan Zhao
- Department of Chemistry, Renmin University of China, Beijing 100872, China
| | - Xiaoyu Yan
- Department of Chemistry, Renmin University of China, Beijing 100872, China
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33
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Gehrke S, Hollóczki O. N-Heterocyclic Carbene Organocatalysis: With or Without Carbenes? Chemistry 2020; 26:10140-10151. [PMID: 32608090 PMCID: PMC7496998 DOI: 10.1002/chem.202002656] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Revised: 06/26/2020] [Indexed: 11/18/2022]
Abstract
In this work the mechanism of the aldehyde umpolung reactions, catalyzed by azolium cations in the presence of bases, was studied through computational methods. Next to the mechanism established by Breslow in the 1950s that takes effect through the formation of a free carbene, we have suggested that these processes can follow a concerted asynchronous path, in which the azolium cation directly reacts with the substrate, avoiding the formation of the carbene intermediate. We hereby show that substituting the azolium cation, and varying the base or the substrate do not affect the preference for the concerted reaction mechanism. The concerted path was found to exhibit low barriers also for the reactions of thiamine with model substrates, showing that this path might have biological relevance. The dominance of the concerted mechanism can be explained through the specific structure of the key transition state, avoiding the liberation of the highly reactive, and thus unstable carbene lone pair, whereas activating the substrate through hydrogen-bonding interactions. Polar and hydrogen-bonding solvents, as well as the presence of the counterions of the azolium salts facilitate the reaction through carbenes, bringing the barriers of the two reaction mechanisms closer, in many cases making the concerted path less favorable. Thus, our data show that by choosing the exact components in a reaction, the mechanism can be switched to occur with or without carbenes.
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Affiliation(s)
- Sascha Gehrke
- Mulliken Center for Theoretical ChemistryUniversity of BonnBeringstr. 4+653115BonnGermany
| | - Oldamur Hollóczki
- Mulliken Center for Theoretical ChemistryUniversity of BonnBeringstr. 4+653115BonnGermany
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Das TK, Biju AT. Imines as acceptors and donors in N-heterocyclic carbene (NHC) organocatalysis. Chem Commun (Camb) 2020; 56:8537-8552. [PMID: 32602493 DOI: 10.1039/d0cc03290e] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The synthetic potential of imines as electrophiles or as a source of nucleophilic coupling partner in N-heterocyclic carbene (NHC) catalysis for the synthesis of various nitrogen heterocycles and functionalized amines is highlighted in this Feature Article. Electrophilic imines are suitable candidates for intercepting the NHC-derived acyl anions, homoenolate equivalents, and (di)enolates for the synthesis of α-amino ketones and a variety of lactam derivatives. Moreover, enamines generated from imines bearing α-hydrogen could be trapped with α,β-unsaturated acylazoliums for the synthesis of functionalized dihydropyridinones. NHCs are also useful for the umpolung of imines for the generation of aza-Breslow intermediates thus leading to the synthesis of indoles, quinolines, dihydroquinoxalines etc. A concise account of the diverse reactivity of imines in NHC catalysis has been presented.
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Affiliation(s)
- Tamal Kanti Das
- Organic Chemistry Division, CSIR-National Chemical Laboratory (CSIR-NCL), Dr Homi Bhabha Road, Pune-411008, India and Academy of Scientific and Innovative Research (AcSIR), New Delhi 110020, India
| | - Akkattu T Biju
- Department of Organic Chemistry, Indian Institute of Science, Bangalore-560012, India.
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Galkin KI, Karlinskii BY, Kostyukovich AY, Gordeev EG, Ananikov VP. Ambident Reactivity of Imidazolium Cations as Evidence of the Dynamic Nature of N-Heterocyclic Carbene-Mediated Organocatalysis. Chemistry 2020; 26:8567-8571. [PMID: 32227612 DOI: 10.1002/chem.201905704] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/27/2020] [Indexed: 11/10/2022]
Abstract
This work reveals ambident nucleophilic reactivity of imidazolium cations towards carbonyl compounds at the C2 or C4 carbene centers depending on the steric properties of the substrates and reaction conditions. Such an adaptive behavior indicates the dynamic nature of organocatalysis proceeding via a covalent interaction of imidazolium carbenes with carbonyl substrates and can be explained by generation of the H-bonded ditopic carbanionic carbenes.
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Affiliation(s)
- Konstantin I Galkin
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| | - Bogdan Ya Karlinskii
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| | - Alexander Yu Kostyukovich
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| | - Evgeniy G Gordeev
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
| | - Valentine P Ananikov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, 119991, Moscow, Russia
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36
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Hollóczki O. The Mechanism of N-Heterocyclic Carbene Organocatalysis through a Magnifying Glass. Chemistry 2020; 26:4885-4894. [PMID: 31797448 PMCID: PMC7187225 DOI: 10.1002/chem.201903021] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Indexed: 11/11/2022]
Abstract
The term "N-Heterocyclic carbene organocatalysis" is often invoked in organic synthesis for reactions that are catalyzed by different azolium salts in the presence of bases. Although the mechanism of these reactions is considered today evident, a closer look into the details that have been collected throughout the last century reveals that there are many open questions and even contradictions in the field. Emerging new theoretical and experimental results offer solutions to these problems, because they show that through considering alternative reaction mechanisms a more consistent picture on the catalytic process can be obtained. These novel perspectives will be able to extend the scope of the reactions that we call today N-heterocyclic carbene organocatalysis.
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Affiliation(s)
- Oldamur Hollóczki
- Mulliken Center for Theoretical ChemistryUniversity of BonnBeringstrasse 4+653115BonnGermany
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37
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Harnying W, Neudörfl JM, Berkessel A. Enantiospecific Synthesis of Nepetalactones by One-Step Oxidative NHC Catalysis. Org Lett 2020; 22:386-390. [PMID: 31904243 DOI: 10.1021/acs.orglett.9b04034] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An efficient oxidative NHC-catalyzed one-step transformation of (S)- or (R)-8-oxocitronellal to nepetalactone (NL) in enantio- and diastereomerically pure form has been developed. Several new and "easy to make" N-Mes- or N-Dipp-substituted 1,2,4-triazolium salts carrying nitroaromatic groups on N1 were synthesized and evaluated as precatalysts in combination with base and stoichiometric organic oxidant. Under optimized conditions, NLs are accessible in very good yields and diastereomerically pure under mild conditions. The oxidant used could be recovered and recycled under operationally simple conditions.
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Affiliation(s)
- Wacharee Harnying
- Department of Chemistry (Organic Chemistry) , University of Cologne , Greinstrasse 4 , 50939 Cologne , Germany
| | - Jörg-M Neudörfl
- Department of Chemistry (Organic Chemistry) , University of Cologne , Greinstrasse 4 , 50939 Cologne , Germany
| | - Albrecht Berkessel
- Department of Chemistry (Organic Chemistry) , University of Cologne , Greinstrasse 4 , 50939 Cologne , Germany
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38
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Barik S, Biju AT. N-Heterocyclic carbene (NHC) organocatalysis using aliphatic aldehydes. Chem Commun (Camb) 2020; 56:15484-15495. [DOI: 10.1039/d0cc06867e] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Recent advances are presented in NHC catalysis employing aliphatic aldehydes as substrates for the generation of various carbene-bound intermediates and subsequent interception with electrophiles/nucleophiles.
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Affiliation(s)
- Shilpa Barik
- Department of Organic Chemistry
- Indian Institute of Science
- Bangalore 560012
- India
| | - Akkattu T. Biju
- Department of Organic Chemistry
- Indian Institute of Science
- Bangalore 560012
- India
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39
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Synthesis of pentafluorobenzene-based NHC adducts and their catalytic activity in the microwave-assisted reactions of aldehydes. Tetrahedron Lett 2020. [DOI: 10.1016/j.tetlet.2019.151419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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40
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Konstandaras N, Dunn MH, Guerry MS, Barnett CD, Cole ML, Harper JB. The impact of cation structure upon the acidity of triazolium salts in dimethyl sulfoxide. Org Biomol Chem 2019; 18:66-75. [PMID: 31746919 DOI: 10.1039/c9ob02258a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A series of triazolium salts, selected for their varying electronic and steric properties, were prepared and their pKa values were determined in DMSO at 25 °C using the bracketing indicator method. The effect of each systematic structural variation upon the acidity of the triazolium cation has been considered, in particular examining the effects of systematically altering electronic properties, quantified through the use of Hammett σ parameters. The first pKa value for an azolium salt that generates a mesionic carbene is also reported. These new data allow for the selection of appropriate bases for the deprotonation of such triazolium salts and the potential to correlate the pKa values determined herein with the nucleophilicity of the corresponding carbenes.
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41
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Ghosh A, Barik S, Biju AT. NHC-Catalyzed [3 + 3] Annulation of Thioamides and Modified Enals for the Enantioselective Synthesis of Functionalized Thiazinones. Org Lett 2019; 21:8598-8602. [PMID: 31618035 DOI: 10.1021/acs.orglett.9b03188] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
N-Heterocyclic carbene (NHC)-catalyzed [3 + 3] annulation of thioamides with modified enals allowing the enantioselective synthesis of functionalized 1,3-thiazin-4-ones is reported. The NHC generated from the chiral triazolium salt was optimal and the reaction is initiated by the thia-Michael addition to catalytically generated α,β-unsaturated acylazolium intermediates derived from 2-bromoenals, followed by intramolecular cyclization. This operationally simple procedure offers a straightforward and rapid access to target compounds in moderate to good yields and enantiomeric ratio values.
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Affiliation(s)
- Arghya Ghosh
- Department of Organic Chemistry , Indian Institute of Science , Bangalore - 560012 , India
| | - Soumen Barik
- Department of Organic Chemistry , Indian Institute of Science , Bangalore - 560012 , India
| | - Akkattu T Biju
- Department of Organic Chemistry , Indian Institute of Science , Bangalore - 560012 , India
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42
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Liu W, Zhao LL, Melaimi M, Cao L, Xu X, Bouffard J, Bertrand G, Yan X. Mesoionic Carbene (MIC)-Catalyzed H/D Exchange at Formyl Groups. Chem 2019. [DOI: 10.1016/j.chempr.2019.08.011] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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43
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Paul M, Peckelsen K, Thomulka T, Neudörfl J, Martens J, Berden G, Oomens J, Berkessel A, Meijer AJHM, Schäfer M. Hydrogen tunneling avoided: enol-formation from a charge-tagged phenyl pyruvic acid derivative evidenced by tandem-MS, IR ion spectroscopy and theory. Phys Chem Chem Phys 2019; 21:16591-16600. [PMID: 31317140 DOI: 10.1039/c9cp02316j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A charge-tagged phenyl pyruvic acid derivative was investigated by tandem-MS, infrared (IR) ion spectroscopy and theory. The tailor-made precursor ions efficiently lose CO2 in collision induced dissociation (CID) experiments, offering access to study the secondary decay reactions of the product ions. IR ion spectroscopy provides evidence for the formation of an enol acid precursor ion structure in the gas phase and indicates the presence of enol products formed after CO2 loss. Extensive DFT computations however, suggest intermediate generation of hydroxycarbene products, which in turn rearrange in a secondary process to the enol ions detected by IR ion spectroscopy. Quantum mechanical tunneling of the hydroxycarbene can be excluded since no evidence for aldehyde product ion formation could be found. This finding is in contrast to the behavior of methylhydroxycarbene, which cleanly penetrates the energy barrier to form exclusively acetaldehyde at cryogenic temperatures in an argon matrix via quantum mechanical hydrogen tunneling. The results presented here are attributed to the highly excited energy levels of the product ions formed by CID in combination with different barrier heights of the competing reaction channels, which allow exclusive access over one energy barrier leading to the formation of the enol tautomer ions observed.
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Affiliation(s)
- Mathias Paul
- University of Cologne, Department of Chemistry, Greinstrasse 4, 50939 Köln, Germany.
| | - Katrin Peckelsen
- University of Cologne, Department of Chemistry, Greinstrasse 4, 50939 Köln, Germany.
| | - Thomas Thomulka
- University of Cologne, Department of Chemistry, Greinstrasse 4, 50939 Köln, Germany.
| | - Jörg Neudörfl
- University of Cologne, Department of Chemistry, Greinstrasse 4, 50939 Köln, Germany.
| | - Jonathan Martens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - Giel Berden
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands
| | - Jos Oomens
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525 ED Nijmegen, The Netherlands and Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Albrecht Berkessel
- University of Cologne, Department of Chemistry, Greinstrasse 4, 50939 Köln, Germany.
| | | | - Mathias Schäfer
- University of Cologne, Department of Chemistry, Greinstrasse 4, 50939 Köln, Germany.
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44
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Paul M, Neudörfl JM, Berkessel A. Breslow Intermediates from a Thiazolin-2-ylidene and Fluorinated Aldehydes: XRD and Solution-Phase NMR Spectroscopic Characterization. Angew Chem Int Ed Engl 2019; 58:10596-10600. [PMID: 31131519 DOI: 10.1002/anie.201904308] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 05/20/2019] [Indexed: 12/20/2022]
Abstract
The first generation and X-ray diffraction (XRD) analysis of a crystalline Breslow intermediate (BI) derived from a thiazolin-2-ylidene, that is, the aromatic heterocycle present in vitamin B1 , is reported. Key to success was the combined use of pentafluorobenzaldehyde and a thiazolin-2-ylidene carrying an enol-stabilizing dispersion energy donor as N-substituent. A so-called primary intermediate (PI) could be isolated in protonated form (pPI) as well and analyzed by XRD. Furthermore, the first stable BI derived from an aromatic thiazolin-2-ylidene and an aliphatic aldehyde (trifluoroacetaldehyde) was prepared and characterized by NMR spectroscopy in solution. When switching to a saturated thiazolidin-2-ylidene, reaction with pentafluorobenzaldehyde afforded a new BI in solution (NMR spectroscopy). Attempts to crystallize the latter BI resulted in the isolation of a novel thiazolidin-2-ylidene dimer that had undergone rearrangement to a hexahydro[1,4]-thiazino[3,2-b]-1,4-thiazine.
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Affiliation(s)
- Mathias Paul
- Cologne University, Department of Chemistry, Greinstrasse 4, 50939, Cologne, Germany
| | - Jörg-M Neudörfl
- Cologne University, Department of Chemistry, Greinstrasse 4, 50939, Cologne, Germany
| | - Albrecht Berkessel
- Cologne University, Department of Chemistry, Greinstrasse 4, 50939, Cologne, Germany
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45
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Paul M, Neudörfl J, Berkessel A. Breslow Intermediates from a Thiazolin‐2‐ylidene and Fluorinated Aldehydes: XRD and Solution‐Phase NMR Spectroscopic Characterization. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201904308] [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)
- Mathias Paul
- Cologne UniversityDepartment of Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Jörg‐M. Neudörfl
- Cologne UniversityDepartment of Chemistry Greinstrasse 4 50939 Cologne Germany
| | - Albrecht Berkessel
- Cologne UniversityDepartment of Chemistry Greinstrasse 4 50939 Cologne Germany
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46
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Wang S, Rodríguez-Escrich C, Fianchini M, Maseras F, Pericàs MA. Diastereodivergent Enantioselective [8 + 2] Annulation of Tropones and Enals Catalyzed by N-Heterocyclic Carbenes. Org Lett 2019; 21:3187-3192. [DOI: 10.1021/acs.orglett.9b00906] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Shoulei Wang
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av Països Catalans 16, 43007 Tarragona, Spain
| | - Carles Rodríguez-Escrich
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av Països Catalans 16, 43007 Tarragona, Spain
| | - Mauro Fianchini
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av Països Catalans 16, 43007 Tarragona, Spain
| | - Feliu Maseras
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av Països Catalans 16, 43007 Tarragona, Spain
- Departament de Química, Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain
| | - Miquel A. Pericàs
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av Països Catalans 16, 43007 Tarragona, Spain
- Departament de Química Inorgànica i Orgànica, Universitat de Barcelona, 08080 Barcelona, Spain
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47
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Doddi A, Peters M, Tamm M. N-Heterocyclic Carbene Adducts of Main Group Elements and Their Use as Ligands in Transition Metal Chemistry. Chem Rev 2019; 119:6994-7112. [PMID: 30983327 DOI: 10.1021/acs.chemrev.8b00791] [Citation(s) in RCA: 302] [Impact Index Per Article: 60.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
N-Heterocyclic carbenes (NHC) are nowadays ubiquitous and indispensable in many research fields, and it is not possible to imagine modern transition metal and main group element chemistry without the plethora of available NHCs with tailor-made electronic and steric properties. While their suitability to act as strong ligands toward transition metals has led to numerous applications of NHC complexes in homogeneous catalysis, their strong σ-donating and adaptable π-accepting abilities have also contributed to an impressive vitalization of main group chemistry with the isolation and characterization of NHC adducts of almost any element. Formally, NHC coordination to Lewis acids affords a transfer of nucleophilicity from the carbene carbon atom to the attached exocyclic moiety, and low-valent and low-coordinate adducts of the p-block elements with available lone pairs and/or polarized carbon-element π-bonds are able to act themselves as Lewis basic donor ligands toward transition metals. Accordingly, the availability of a large number of novel NHC adducts has not only produced new varieties of already existing ligand classes but has also allowed establishment of numerous complexes with unusual and often unprecedented element-metal bonds. This review aims at summarizing this development comprehensively and covers the usage of N-heterocyclic carbene adducts of the p-block elements as ligands in transition metal chemistry.
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Affiliation(s)
- Adinarayana Doddi
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Hagenring 30, 38106 Braunschweig, Germany
| | - Marius Peters
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Hagenring 30, 38106 Braunschweig, Germany
| | - Matthias Tamm
- Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Hagenring 30, 38106 Braunschweig, Germany
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48
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Singh T, George A, Parameswaran P, Bharatam PV. Enols, Diamino Enols, and Breslow Intermediates: A Comparative Quantum Chemical Analysis. European J Org Chem 2019. [DOI: 10.1002/ejoc.201801817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Tejender Singh
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER), Sector 67; 160 062 S.A.S. Nagar - Punjab India
| | - Anjana George
- Department of Chemistry; National Institute of Technology Calicut; NIT Calicut Campus P.O. 673 601 Kozhikode - Kerala India
| | - Pattiyil Parameswaran
- Department of Chemistry; National Institute of Technology Calicut; NIT Calicut Campus P.O. 673 601 Kozhikode - Kerala India
| | - Prasad V. Bharatam
- Department of Medicinal Chemistry; National Institute of Pharmaceutical Education and Research (NIPER), Sector 67; 160 062 S.A.S. Nagar - Punjab India
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49
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Wu Z, Wang J. A tandem dearomatization/rearomatization strategy: enantioselective N-heterocyclic carbene-catalyzed α-arylation. Chem Sci 2019; 10:2501-2506. [PMID: 30881680 PMCID: PMC6385844 DOI: 10.1039/c8sc04601h] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 12/21/2018] [Indexed: 12/14/2022] Open
Abstract
In this study, the first example of carbene-catalyzed tandem dearomatization/rearomatization reaction of azonaphthalenes with α-chloroaldehydes is described.
In this study, the first example of the carbene-catalyzed tandem dearomatization/rearomatization reaction of azonaphthalenes with α-chloroaldehydes is described. This protocol enables the efficient assembly of chiral dihydrocinnolinone derivatives in good yields with excellent enantioselectivities (up to 99% ee). Moreover, this strategy enables not only the highly enantioselective NHC-catalyzed nucleophilic aromatic substitution, but also a formal Csp2–Csp3 bond formation.
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Affiliation(s)
- Zijun Wu
- School of Pharmaceutical Sciences , Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology , Ministry of Education , Tsinghua University , Beijing , 100084 , China .
| | - Jian Wang
- School of Pharmaceutical Sciences , Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology , Ministry of Education , Tsinghua University , Beijing , 100084 , China .
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50
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Xu W, Li Y, Liu R, Yang S, Liu J, Fang X. Kinetic resolution of 2,2-disubstituted-1,3-diketones via carbene catalysis. Org Chem Front 2019. [DOI: 10.1039/c8qo01137k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Organocatalytic kinetic resolution of 1,3-diketones with central quaternary stereocenters was achieved for the first time. The resolution proceeds via two basic modes, and the inherent principles between the different combinations of ketone groups and the resolution patterns were also disclosed.
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Affiliation(s)
- Weici Xu
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Yuanzhen Li
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Rui Liu
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Shuang Yang
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Jian Liu
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
| | - Xinqiang Fang
- State Key Laboratory of Structural Chemistry
- and Key Laboratory of Coal to Ethylene Glycol and Its Related Technology
- Fujian Institute of Research on the Structure of Matter (FJIRSM)
- University of Chinese Academy of Sciences
- Fuzhou 350100
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