1
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Mazars F, Zaragoza G, Delaude L. The facile alkylation and iodination of imidazol(in)ium salts in the presence of cesium carbonate. Chem Commun (Camb) 2023; 59:14528-14531. [PMID: 37942885 DOI: 10.1039/d3cc04971j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
The alkylation or iodination of imidazol(in)ium salts takes place readily in the presence of Cs2CO3. The procedure is very easy to implement and provides facile and straightforward access to a wealth of C2-substituted azolium salts. Furthermore, a C2α alkylation is also feasible, which extends the chemistry of NHCs and weak bases to their NHO analogues.
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Affiliation(s)
- François Mazars
- Laboratory of Catalysis, MolSys Research Unit, Université de Liège, Institut de Chimie Organique (B6a), Allée du six Août 13, Liège 4000, Belgium.
| | - Guillermo Zaragoza
- Unidade de Difracción de Raios X, RIAIDT, Universidade de Santiago de Compostela, Campus Vida, 15782 Santiago de Compostela, Spain
| | - Lionel Delaude
- Laboratory of Catalysis, MolSys Research Unit, Université de Liège, Institut de Chimie Organique (B6a), Allée du six Août 13, Liège 4000, Belgium.
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2
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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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3
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Dubey G, Singh T, Bharatam PV. The importance of four-membered NHCs in stabilizing Breslow intermediates on benzoin condensation pathway. J Comput Chem 2023; 44:346-354. [PMID: 35652523 DOI: 10.1002/jcc.26935] [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: 02/23/2022] [Revised: 04/27/2022] [Accepted: 05/07/2022] [Indexed: 01/03/2023]
Abstract
N-heterocyclic carbenes (NHCs) have been established to be effective organocatalysts for facilitating the benzoin condensation and many other reactions. These reactions involve the formation of a Breslow intermediate (BI), which exhibits umpolung chemistry. To facilitate organocatalysis, several new cyclic carbenes are being introduced, four-membered NHCs are of special interest. Whether these NHCs can exhibit catalytic influence or not, can be evaluated by exploring the potential energy surface (PES) of the benzoin condensation reaction. Quantum chemical analysis has been carried out to compare the PES of these four-membered NHCs with that of standard five-membered NHCs to explore their catalytic ability. The barrier for the first step of the reaction for the formation of BI is comparable in all the cases. But the barrier for the second step of the reaction leading to the benzoin formation from BI is estimated to be very high for the four membered NHCs. These results indicate that the probability of identifying and isolating the BI is very high in comparison to the completion of benzoin condensation reaction in the case of the four-membered NHCs.
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Affiliation(s)
- Gurudutt Dubey
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), SAS Nagar, India
| | - Tejender Singh
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), SAS Nagar, India
| | - Prasad V Bharatam
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), SAS Nagar, India
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4
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Blyth MT, Coote ML. Manipulation of N-heterocyclic carbene reactivity with practical oriented electric fields. Phys Chem Chem Phys 2023; 25:375-383. [DOI: 10.1039/d2cp04507a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Electric fields can be used to tune the nucleophilicity and electrophilicity of N-heterocyclic carbenes and enhance their catalytic activity.
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Affiliation(s)
- Mitchell T. Blyth
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Michelle L. Coote
- Institute for Nanoscale Science and Technology, College of Science and Engineering, Flinders University, Bedford Park, South Australia 5042, Australia
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5
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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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6
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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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7
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Zhang N, Yu X, Zhang Y. Recent Advances of Thiamine in Organic Synthesis. Adv Synth Catal 2022. [DOI: 10.1002/adsc.202200098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Ning Zhang
- School of Chemistry and Pharmaceutical Engineering Jilin Institute of Chemical Technology Jilin 132022 People's Republic of China
- College of Chemistry Jilin University Changchun 130012 People's Republic of China
| | - Xue Yu
- School of Chemistry and Pharmaceutical Engineering Jilin Institute of Chemical Technology Jilin 132022 People's Republic of China
| | - Yuewei Zhang
- School of Chemistry and Pharmaceutical Engineering Jilin Institute of Chemical Technology Jilin 132022 People's Republic of China
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8
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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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9
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Lu F, Chen Y, Song X, Yu C, Li T, Zhang K, Yao C. NHC-Catalyzed [2 + 4] Annulation of Alkynyl Ester with Chalcone. J Org Chem 2022; 87:6902-6909. [PMID: 35486449 DOI: 10.1021/acs.joc.2c00022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An NHC-catalyzed [2 + 4] cyclization of alkynyl ester with α,β-unsaturated ketone to form a pyran scaffold was developed successfully. The cheap and easily available starting materials, mild reaction conditions, moderate to excellent yields, and high atom economy make this strategy attractive for the syntheses of highly substituted 4H-pyran derivatives.
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Affiliation(s)
- Fangfang Lu
- Jiangsu Key Lab of Green Synthetic Chemistry for Functional Materials, School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, P. R. China
| | - Yangxu Chen
- Jiangsu Key Lab of Green Synthetic Chemistry for Functional Materials, School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, P. R. China
| | - Xue Song
- Jiangsu Key Lab of Green Synthetic Chemistry for Functional Materials, School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, P. R. China
| | - Chenxia Yu
- Jiangsu Key Lab of Green Synthetic Chemistry for Functional Materials, School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, P. R. China
| | - Tuanjie Li
- Jiangsu Key Lab of Green Synthetic Chemistry for Functional Materials, School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, P. R. China
| | - Kai Zhang
- Jiangsu Key Lab of Green Synthetic Chemistry for Functional Materials, School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, P. R. China
| | - Changsheng Yao
- Jiangsu Key Lab of Green Synthetic Chemistry for Functional Materials, School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou, Jiangsu 221116, P. R. China
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10
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Direct Synthesis of Vinylene Carbonates from Aromatic Aldehydes. European J Org Chem 2022. [DOI: 10.1002/ejoc.202200153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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11
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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: 3] [Impact Index Per Article: 1.5] [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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12
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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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13
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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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14
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Alizadeh V, Kirchner B. Molecular level insight into the solvation of cellulose in deep eutectic solvents. J Chem Phys 2021; 155:084501. [PMID: 34470350 DOI: 10.1063/5.0058333] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Deep eutectic solvents as sustainable and new-generation solvents show potential in the field of cellulose dissolution. Although these novel materials are tested for numerous industrial, environmental, and medical applications, little is known about the structural features of cellulose interacting with deep eutectic solvents. In this work, the interplay of cellulose is studied in two deep eutectic solvents: choline acetate mixed with urea and choline chloride mixed with urea using classical molecular dynamics simulations. Dissolution of cellulose in the studied liquids was not observed to be in agreement with experimental work from the literature. However, a slight swelling in the chloride, as compared to the acetate-based solvent, is apparent. A possible rationale might be found in the stronger hydrogen bonding of the chloride anion compared to the acetate anion with the hydrogen atoms of the cellulose. Moreover, chloride approaches the outer glucose units comparatively more, which could be interpreted as the onset of entering and thus dissolving the cellulose as was previously observed. Specific hydrogen bonds between all units are analyzed and discussed in detail.
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Affiliation(s)
- Vahideh Alizadeh
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstraße 4+6, D-53115 Bonn, Germany
| | - Barbara Kirchner
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstraße 4+6, D-53115 Bonn, Germany
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15
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Mazars F, Hrubaru M, Tumanov N, Wouters J, Delaude L. Synthesis of Azolium‐2‐dithiocarboxylate Zwitterions under Mild, Aerobic Conditions. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100274] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- François Mazars
- Laboratory of Catalysis MolSys Research Unit Université de Liège Institut de Chimie Organique (B6a) Allée du six Août 13 4000 Liège Belgium
| | - Madalina Hrubaru
- Center for Organic Chemistry “Costin D. Nenitescu” Romanian Academy Spl Independentei Bucureşti, 202B 060023 Bucharest Romania
| | - Nikolay Tumanov
- Department of Chemistry Université de Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Johan Wouters
- Department of Chemistry Université de Namur Rue de Bruxelles 61 5000 Namur Belgium
| | - Lionel Delaude
- Laboratory of Catalysis MolSys Research Unit Université de Liège Institut de Chimie Organique (B6a) Allée du six Août 13 4000 Liège Belgium
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16
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Vetica F, Bortolami M, Petrucci R, Rocco D, Feroci M. Electrogenerated NHCs in Organic Synthesis: Ionic Liquids vs Organic Solvents Effects. CHEM REC 2021; 21:2130-2147. [PMID: 33507627 DOI: 10.1002/tcr.202000178] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 01/08/2021] [Indexed: 12/14/2022]
Abstract
In the last twenty years, N-heterocyclic carbenes (NHCs) have been extensively studied for their application as organocatalysts in stereoselective synthesis as well as ligands for transition metals-promoted synthetic methodologies. Derived mainly from azolium salts, NHCs have demonstrated exceptional versatility in their generation usually performed by deprotonation or reduction (chemical or electrochemical). In particular, the generation of NHC under electrochemical conditions, starting from azolium-based ionic liquids, has proven to be a successful green approach and demonstrated wide applicability in organic synthesis. In this Personal Account, the application of electrogenerated NHCs in organic synthesis will be discussed, with a particular attention to the different reactivity in ionic liquids compared to classical organic solvents.
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Affiliation(s)
- Fabrizio Vetica
- Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Martina Bortolami
- Department of Basic and Applied Sciences for Engineering (SBAI), Sapienza University of Rome, Via Castro Laurenziano 7, 00161, Rome, Italy
| | - Rita Petrucci
- Department of Basic and Applied Sciences for Engineering (SBAI), Sapienza University of Rome, Via Castro Laurenziano 7, 00161, Rome, Italy
| | - Daniele Rocco
- Department of Basic and Applied Sciences for Engineering (SBAI), Sapienza University of Rome, Via Castro Laurenziano 7, 00161, Rome, Italy
| | - Marta Feroci
- Department of Basic and Applied Sciences for Engineering (SBAI), Sapienza University of Rome, Via Castro Laurenziano 7, 00161, Rome, Italy
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17
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Martynova EA, Tzouras NV, Pisanò G, Cazin CSJ, Nolan SP. The “weak base route” leading to transition metal–N-heterocyclic carbene complexes. Chem Commun (Camb) 2021; 57:3836-3856. [DOI: 10.1039/d0cc08149c] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
N-Heterocyclic carbenes (NHCs) are nowadays ubiquitous in organometallic chemistry and catalysis. A simple synthetic route to these is presented.
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Affiliation(s)
- Ekaterina A. Martynova
- Department of Chemistry and Centre for Sustainable Chemistry
- Ghent University
- 9000 Gent
- Belgium
| | - Nikolaos V. Tzouras
- Department of Chemistry and Centre for Sustainable Chemistry
- Ghent University
- 9000 Gent
- Belgium
| | - Gianmarco Pisanò
- Department of Chemistry and Centre for Sustainable Chemistry
- Ghent University
- 9000 Gent
- Belgium
| | - Catherine S. J. Cazin
- Department of Chemistry and Centre for Sustainable Chemistry
- Ghent University
- 9000 Gent
- Belgium
| | - Steven P. Nolan
- Department of Chemistry and Centre for Sustainable Chemistry
- Ghent University
- 9000 Gent
- Belgium
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18
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N-PEGylated Thiazolium Salt: A Green and Reusable Homogenous Organocatalyst for the Synthesis of Benzoins and Acyloins. Catal Letters 2020. [DOI: 10.1007/s10562-020-03417-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Shi XL, Sun B, Hu Q, Liu K, Li P, Wang J. Recyclable polyetheretherketone fiber-supported N-heterocyclic carbene catalysts for nucleophilic acylation of fluorobenzenes. Chem Commun (Camb) 2020; 56:11390-11393. [PMID: 32990293 DOI: 10.1039/d0cc04394j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We report for the first time a novel support of polyetheretherketone fiber for the synthesis of recyclable N-heterocyclic carbene (NHC) catalysts. The fiber catalysts were verified in nucleophilic acylation of fluorobenzenes with superior catalytic activities, and successfully recycled by a tiny pair of tweezers over 21 cycles with minimal loss of performance.
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Affiliation(s)
- Xian-Lei Shi
- Synerigism Innovative Center of Coal Safety Production in Henan Province, College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo, Henan 454003, P. R. China.
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20
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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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21
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Li X, Xu J, Li SJ, Qu LB, Li Z, Chi YR, Wei D, Lan Y. Prediction of NHC-catalyzed chemoselective functionalizations of carbonyl compounds: a general mechanistic map. Chem Sci 2020; 11:7214-7225. [PMID: 34123007 PMCID: PMC8159411 DOI: 10.1039/d0sc01793k] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Generally, N-heterocyclic carbene (NHC) complexed with carbonyl compounds would transform into several important active intermediates, i.e., enolates, Breslow intermediates, or acylazolium intermediates, which act as either a nucleophile (Nu) or an electrophile (E) to react with the other E/Nu partner. Hence, the key to predicting the origin of chemoselectivity is to compute the activity (i.e., electrophilic index ω for E and nucleophilic index N for Nu) and stability of the intermediates and products, which are suggested in a general mechanistic map of these reactions. To support this point, we selected and studied different cases of the NHC-catalyzed reactions of carbonyl compounds in the presence of a base and/or an oxidant, in which multiple possible pathways involving acylazolium, enolate, Breslow, and α,β-unsaturated acylazolium intermediates were proposed and a novel index ω + N of the E and Nu partners was employed to exactly predict the energy barrier of the chemoselective step in theory. This work provides a guide for determining the general principle behind organocatalytic reactions with various chemoselectivities, and suggests a general application of the reaction index in predicting the chemoselectivity of the nucleophilic and electrophilic reactions. A novel index ω + N can be used to predict the chemoselectivity according to the general NHC-catalyzed reaction mechanism.![]()
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Affiliation(s)
- Xue Li
- College of Chemistry, Institute of Green Catalysis, Zhengzhou University 100 Science Avenue Zhengzhou Henan 450001 China
| | - Jun Xu
- College of Pharmacy, Guizhou University of Traditional Chinese Medicine Guiyang China
| | - Shi-Jun Li
- College of Chemistry, Institute of Green Catalysis, Zhengzhou University 100 Science Avenue Zhengzhou Henan 450001 China
| | - Ling-Bo Qu
- College of Chemistry, Institute of Green Catalysis, Zhengzhou University 100 Science Avenue Zhengzhou Henan 450001 China
| | - Zhongjun Li
- College of Chemistry, Institute of Green Catalysis, Zhengzhou University 100 Science Avenue Zhengzhou Henan 450001 China
| | - Yonggui Robin Chi
- Division of Chemistry & Biological Chemistry, School of Physical & Mathematical Sciences, Nanyang Technological University Singapore 637371 Singapore
| | - Donghui Wei
- College of Chemistry, Institute of Green Catalysis, Zhengzhou University 100 Science Avenue Zhengzhou Henan 450001 China
| | - Yu Lan
- College of Chemistry, Institute of Green Catalysis, Zhengzhou University 100 Science Avenue Zhengzhou Henan 450001 China .,College of Chemistry and Chemical Engineering, Chongqing University Chongqing 400044 China
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22
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Blasius J, Elfgen R, Hollóczki O, Kirchner B. Glucose in dry and moist ionic liquid: vibrational circular dichroism, IR, and possible mechanisms. Phys Chem Chem Phys 2020; 22:10726-10737. [PMID: 32150178 DOI: 10.1039/c9cp06798a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquids and their mixtures with water show remarkable features in cellulose processing. For this reason, understanding the behavior of carbohydrates in ionic liquids is important. In the present study, we investigated three d-glucose isomers (α, β and open-chain) in 1-ethyl-3-methylimidazolium acetate in the presence and absence of water, through ab initio molecular dynamics simulations. In the complex hydrogen bonding network of these mixtures, the most interesting observation is that upon water addition every hydrogen bond elongates, except the glucose-glucose hydrogen bond for the open-chain and the α-form which shortens, clearly showing the beginning of the crystallization process. The ring glucose rearranges from on-top to in-plane and the open form changes from a coiled to a more linear arrangement when adding water which explains the contradiction that the center of mass distances of the glucose molecules with other glucose molecules grow while the hydrogen bonds shorten. The appearance of coiled open forms indicates that the previously suggested isomerization between these forms is possible and might play a role in the solubility of the related carbohydrates. The calculated IR and VCD spectra reveal insight into the intermolecular interactions, with good to excellent agreements with experimental spectra. Investigating the role of the cation, distances between the acidic carbon atom of the cation and the glucose carbon atom where ring closure and opening occurs are found, which are way shorter than dispersion-like interactions between aliphatic hydrocarbons.
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Affiliation(s)
- Jan Blasius
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstraße 4 + 6, D-53115 Bonn, Germany.
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23
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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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24
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Affiliation(s)
- Jinseong Jeong
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute of Basic Science (IBS), Daejeon, 34126, South Korea
| | - Joon Heo
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute of Basic Science (IBS), Daejeon, 34126, South Korea
| | - Dongwook Kim
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute of Basic Science (IBS), Daejeon, 34126, South Korea
| | - Sukbok Chang
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, South Korea
- Center for Catalytic Hydrocarbon Functionalizations, Institute of Basic Science (IBS), Daejeon, 34126, South Korea
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25
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Tzouras NV, Nahra F, Falivene L, Cavallo L, Saab M, Van Hecke K, Collado A, Collett CJ, Smith AD, Cazin CSJ, Nolan SP. A Mechanistically and Operationally Simple Route to Metal-N-Heterocyclic Carbene (NHC) Complexes. Chemistry 2020; 26:4515-4519. [PMID: 32022329 DOI: 10.1002/chem.202000564] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Indexed: 11/08/2022]
Abstract
We have been puzzled by the involvement of weak organic and inorganic bases in the synthesis of metal-N-heterocyclic carbene (NHC) complexes. Such bases are insufficiently strong to permit the presumed required deprotonation of the azolium salt (the carbene precursor) prior to metal binding. Experimental and computational studies provide support for a base-assisted concerted process that does not require free NHC formation. The synthetic protocol was found applicable to a number of transition-metal- and main-group-centered NHC compounds and could become the synthetic route of choice to form M-NHC bonds.
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Affiliation(s)
- Nikolaos V Tzouras
- Department of Chemistry and Centre for Sustainable Chemistry, Ghent University, Krijgslaan 281,S-3, 9000, Ghent, Belgium
| | - Fady Nahra
- Department of Chemistry and Centre for Sustainable Chemistry, Ghent University, Krijgslaan 281,S-3, 9000, Ghent, Belgium.,Separation and Conversion Technology Unit, VITO (Flemish Institute for Technological Research), Boeretang 200, B-2400, Mol, Belgium
| | - Laura Falivene
- KAUST Catalysis Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Luigi Cavallo
- KAUST Catalysis Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Marina Saab
- Department of Chemistry and Centre for Sustainable Chemistry, Ghent University, Krijgslaan 281,S-3, 9000, Ghent, Belgium
| | - Kristof Van Hecke
- Department of Chemistry and Centre for Sustainable Chemistry, Ghent University, Krijgslaan 281,S-3, 9000, Ghent, Belgium
| | - Alba Collado
- EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK
| | | | - Andrew D Smith
- EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK
| | - Catherine S J Cazin
- Department of Chemistry and Centre for Sustainable Chemistry, Ghent University, Krijgslaan 281,S-3, 9000, Ghent, Belgium
| | - Steven P Nolan
- Department of Chemistry and Centre for Sustainable Chemistry, Ghent University, Krijgslaan 281,S-3, 9000, Ghent, Belgium
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26
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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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27
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Hsieh MH, Huang GT, Yu JSK. Can the Radical Channel Contribute to the Catalytic Cycle of N-Heterocyclic Carbene in Benzoin Condensation? J Org Chem 2018; 83:15202-15209. [PMID: 30457867 DOI: 10.1021/acs.joc.8b02483] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
NHC can catalyze benzoin condensation via the key Breslow intermediate. EPR spectroscopy recently confirmed the existence of the radical species, but its catalytic role is still unclear. Herein, we use density functional approaches to study the radical-associated pathway in comparison with the nonradical mechanism reported previously. Theoretical investigations show that the nonradical path (Δ G⧧ = 18.7 kcal/mol) is more kinetically favorable than the radical route (Δ G⧧ = 27.6 kcal/mol), which is initialized by the hydrogen abstraction from the Breslow intermediate by benzaldehyde, leading to a radical pair. The product formation is thus dominated by the nonradical pathway. In addition, the Breslow intermediate is less stable than its keto form, which blocks the benzoin condensation, and the radical species could play an important role in assisting the tautomerization and promoting the catalytic reaction.
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28
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Phan J, Ruser SM, Zeitler K, Rehbein J. NHC-Stabilized Radicals in the Formal Hydroacylation Reaction of Alkynes. European J Org Chem 2018. [DOI: 10.1002/ejoc.201801185] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jenny Phan
- Fakultät für Chemie und Pharmazie; Universität Regensburg; Institut für Organische Chemie; Universitätsstrasse 1 93053 Regensburg Germany
| | - Stephanie-M. Ruser
- Fachbereich Chemie; Universität Hamburg; Institut für Organische Chemie; Martin-Luther-King-Platz 6 20146 Hamburg Germany
| | - Kirsten Zeitler
- Institut für Organische Chemie; Universität Leipzig; Johannis-Allee 29 04103 Leipzig Germany
| | - Julia Rehbein
- Fakultät für Chemie und Pharmazie; Universität Regensburg; Institut für Organische Chemie; Universitätsstrasse 1 93053 Regensburg Germany
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29
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Gehrke S, Reckien W, Palazzo I, Welton T, Hollóczki O. On the Carbene-Like Reactions of Imidazolium Acetate Ionic Liquids: Can Theory and Experiments Agree? European J Org Chem 2018. [DOI: 10.1002/ejoc.201801050] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Sascha Gehrke
- Mulliken Center for Theoretical Chemistry; University of Bonn; Beringstr. 4+6 Bonn Germany
- Max Planck Institute for Chemical Energy Conversion; Stiftstrasse 34-36 45470 Muelheim an der Ruhr Germany
| | - Werner Reckien
- Mulliken Center for Theoretical Chemistry; University of Bonn; Beringstr. 4+6 Bonn Germany
| | - Ivan Palazzo
- Department of Chemistry; Imperial College London; 2AZ London, SW7 UK
| | - Tom Welton
- Department of Chemistry; Imperial College London; 2AZ London, SW7 UK
| | - Oldamur Hollóczki
- Mulliken Center for Theoretical Chemistry; University of Bonn; Beringstr. 4+6 Bonn Germany
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30
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Rico del Cerro D, Mera‐Adasme R, King AWT, Perea‐Buceta JE, Heikkinen S, Hase T, Sundholm D, Wähälä K. On the Mechanism of the Reactivity of 1,3‐Dialkylimidazolium Salts under Basic to Acidic Conditions: A Combined Kinetic and Computational Study. Angew Chem Int Ed Engl 2018; 57:11613-11617. [PMID: 29987916 DOI: 10.1002/anie.201805016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/07/2018] [Indexed: 11/09/2022]
Affiliation(s)
- Daniel Rico del Cerro
- Department of ChemistryUniversity of Helsinki P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Raúl Mera‐Adasme
- Departamento de Ciencias del AmbienteFacultad de Química y BiologíaUniversidad de Santiago de Chile Av. Libertador Bernardo O'Higgins 3363 9170022 Estacion Central Chile
| | - Alistair W. T. King
- Department of ChemistryUniversity of Helsinki P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Jesus E. Perea‐Buceta
- Department of ChemistryUniversity of Helsinki P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Sami Heikkinen
- Department of ChemistryUniversity of Helsinki P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Tapio Hase
- Department of ChemistryUniversity of Helsinki P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Dage Sundholm
- Department of ChemistryUniversity of Helsinki P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Kristiina Wähälä
- Department of ChemistryUniversity of Helsinki P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
- Department of Biochemistry and Development BiologyUniversity of Helsinki Haartmaninkatu 3, P.O. Box 21 000140 Helsinki Finland
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31
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Rico del Cerro D, Mera-Adasme R, King AWT, Perea-Buceta JE, Heikkinen S, Hase T, Sundholm D, Wähälä K. On the Mechanism of the Reactivity of 1,3-Dialkylimidazolium Salts under Basic to Acidic Conditions: A Combined Kinetic and Computational Study. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201805016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Daniel Rico del Cerro
- Department of Chemistry; University of Helsinki; P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Raúl Mera-Adasme
- Departamento de Ciencias del Ambiente; Facultad de Química y Biología; Universidad de Santiago de Chile; Av. Libertador Bernardo O'Higgins 3363 9170022 Estacion Central Chile
| | - Alistair W. T. King
- Department of Chemistry; University of Helsinki; P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Jesus E. Perea-Buceta
- Department of Chemistry; University of Helsinki; P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Sami Heikkinen
- Department of Chemistry; University of Helsinki; P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Tapio Hase
- Department of Chemistry; University of Helsinki; P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Dage Sundholm
- Department of Chemistry; University of Helsinki; P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
| | - Kristiina Wähälä
- Department of Chemistry; University of Helsinki; P.O. Box 55, A.I. Virtasen aukio 1 00014 Helsinki Finland
- Department of Biochemistry and Development Biology; University of Helsinki; Haartmaninkatu 3, P.O. Box 21 000140 Helsinki Finland
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32
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Macchieraldo R, Esser L, Elfgen R, Voepel P, Zahn S, Smarsly BM, Kirchner B. Hydrophilic Ionic Liquid Mixtures of Weakly and Strongly Coordinating Anions with and without Water. ACS OMEGA 2018; 3:8567-8582. [PMID: 31458986 PMCID: PMC6644474 DOI: 10.1021/acsomega.8b00995] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/20/2018] [Indexed: 05/22/2023]
Abstract
With the aid of ab initio molecular dynamics simulations, we investigate an ionic liquid (IL) mixture composed of three components 1-butyl-3-methylimidazolium [C4C1Im]+, tetrafluoroborate [BF4]-, and chloride [Cl]- without and with water. In the pure IL mixture, we observe an already complex network of interactions between cations and anions, and addition of water to the system even extends the complexity. Observed number integrals show that the coordination number between cations and anions is reduced in the system with water compared to that in the pure system. Further studies show that the Coulombic network of the strongly coordinating anion [Cl]- is disturbed by water, while that of the weakly coordinating anion [BF4]- is not. These observations can also be confirmed by the Voronoi polyhedra analysis, which shows that the polar network of microheterogeneous IL collapses by the introduction of water. Hydrogen-acceptor interactions revealed that the [Cl]- anions are transferred from being situated in the IL to the water continuum, while [BF4]- is almost unperturbed; these effects mainly influence the interplay of the ionic liquid network.
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Affiliation(s)
- Roberto Macchieraldo
- Mulliken
Center for Theoretical Chemistry, University
of Bonn, Beringstr. 4+6, D-53115 Bonn, Germany
| | - Lars Esser
- Mulliken
Center for Theoretical Chemistry, University
of Bonn, Beringstr. 4+6, D-53115 Bonn, Germany
| | - Roman Elfgen
- Mulliken
Center for Theoretical Chemistry, University
of Bonn, Beringstr. 4+6, D-53115 Bonn, Germany
- Max
Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45413 Mülheim an der Ruhr, Germany
| | - Pascal Voepel
- Institute
of Physical Chemistry and Center for Materials Research (LaMa), Justus-Liebig-University Giessen, Heinrich-Buff Ring 17+16, D-35392 Giessen, Germany
| | - Stefan Zahn
- Leibniz
Institute of Surface Engineering, Permoserstr. 15, D-04318 Leipzig, Germany
| | - Bernd M. Smarsly
- Institute
of Physical Chemistry and Center for Materials Research (LaMa), Justus-Liebig-University Giessen, Heinrich-Buff Ring 17+16, D-35392 Giessen, Germany
| | - Barbara Kirchner
- Mulliken
Center for Theoretical Chemistry, University
of Bonn, Beringstr. 4+6, D-53115 Bonn, Germany
- E-mail:
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33
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Chiarotto I, Mattiello L, Pandolfi F, Rocco D, Feroci M. NHC in Imidazolium Acetate Ionic Liquids: Actual or Potential Presence? Front Chem 2018; 6:355. [PMID: 30211149 PMCID: PMC6121013 DOI: 10.3389/fchem.2018.00355] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 07/30/2018] [Indexed: 11/13/2022] Open
Abstract
Ionic liquids (ILs) are considered in the majority of cases green solvents, due to their virtually null vapor pressure and to the easiness in recycling them. In particular, imidazolium ILs are widely used in many fields of Chemistry, as solvents or precursors of N-heterocyclic carbenes (NHCs). The latter are easily obtained by deprotonation of the C2-H, usually using strong bases or cathodic reduction. Nevertheless, it is known that weaker bases (e.g., triethylamine) are able to promote C2-H/D exchange. From this perspective, the possibility of deprotonating C2-H group of an imidazolium cation by means of a basic counter-ion was seriously considered and led to the synthesis of imidazolium ILs spontaneously containing NHCs. The most famous of this class of ILs are N,N'-disubstituted imidazolium acetates. Due to the particular reactivity of this kind of ILs, they were appointed as “organocatalytic ionic liquids” or “proto-carbenes.” Many papers report the use of these imidazolium acetates in organocatalytic reactions (i. e., catalyzed by NHC) or in stoichiometric NHC reactions (e.g., with elemental sulfur to yield the corresponding imidazole-2-thiones). Nevertheless, the actual presence of NHC in N,N'-disubstituted imidazolium acetate is still controversial. Moreover, theoretical studies seem to rule out the presence of NHC in such a polar environment as an IL. Aim of this Mini Review is to give the reader an up-to-date overview on the actual or potential presence of NHC in such an “organocatalytic ionic liquid,” both from the experimental and theoretical point of view, without the intent to be exhaustive on N,N'-disubstituted imidazolium acetate applications.
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Affiliation(s)
- Isabella Chiarotto
- Dipartimento di Scienze di Base e Applicate per l'Ingegneria, Sapienza University of Rome, Rome, Italy
| | - Leonardo Mattiello
- Dipartimento di Scienze di Base e Applicate per l'Ingegneria, Sapienza University of Rome, Rome, Italy
| | - Fabiana Pandolfi
- Dipartimento di Scienze di Base e Applicate per l'Ingegneria, Sapienza University of Rome, Rome, Italy
| | - Daniele Rocco
- Dipartimento di Scienze di Base e Applicate per l'Ingegneria, Sapienza University of Rome, Rome, Italy
| | - Marta Feroci
- Dipartimento di Scienze di Base e Applicate per l'Ingegneria, Sapienza University of Rome, Rome, Italy
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Gehrke S, Hollóczki O. Hydrogen Bonding of N‐Heterocyclic Carbenes in Solution: Mechanisms of Solvent Reorganization. Chemistry 2018; 24:11594-11604. [DOI: 10.1002/chem.201802286] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 06/07/2018] [Indexed: 11/05/2022]
Affiliation(s)
- Sascha Gehrke
- Mulliken Center for Theoretical ChemistryUniversity of Bonn Beringstr. 4+6 53115 Bonn Germany
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 45470 Muelheim an der Ruhr Germany
| | - Oldamur Hollóczki
- Mulliken Center for Theoretical ChemistryUniversity of Bonn Beringstr. 4+6 53115 Bonn Germany
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35
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Nesterov V, Reiter D, Bag P, Frisch P, Holzner R, Porzelt A, Inoue S. NHCs in Main Group Chemistry. Chem Rev 2018; 118:9678-9842. [PMID: 29969239 DOI: 10.1021/acs.chemrev.8b00079] [Citation(s) in RCA: 508] [Impact Index Per Article: 84.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Since the discovery of the first stable N-heterocyclic carbene (NHC) in the beginning of the 1990s, these divalent carbon species have become a common and available class of compounds, which have found numerous applications in academic and industrial research. Their important role as two-electron donor ligands, especially in transition metal chemistry and catalysis, is difficult to overestimate. In the past decade, there has been tremendous research attention given to the chemistry of low-coordinate main group element compounds. Significant progress has been achieved in stabilization and isolation of such species as Lewis acid/base adducts with highly tunable NHC ligands. This has allowed investigation of numerous novel types of compounds with unique electronic structures and opened new opportunities in the rational design of novel organic catalysts and materials. This Review gives a general overview of this research, basic synthetic approaches, key features of NHC-main group element adducts, and might be useful for the broad research community.
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Affiliation(s)
- Vitaly Nesterov
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Dominik Reiter
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Prasenjit Bag
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Philipp Frisch
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Richard Holzner
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Amelie Porzelt
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
| | - Shigeyoshi Inoue
- Department of Chemistry, WACKER-Institute of Silicon Chemistry and Catalysis Research Center , Technische Universität München , Lichtenbergstrasse 4 , Garching bei München 85748 , Germany
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ADUC Prizes: U.-P. Apfel, P. Heretsch, O. Hollóczki / Carl Duisberg Memorial Award: B. Morandi / Elected to the Académie des Sciences: E. Charpentier, J. Cossy, I. Marek / Max Delbrück Junior Prize: S. Disch / Novartis Early Career Award: B. Morandi and R. Angew Chem Int Ed Engl 2018; 57:2286-2287. [DOI: 10.1002/anie.201801006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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ADUC-Preise: U.-P. Apfel, P. Heretsch, O. Hollóczki / Carl-Duisberg-Gedächtnispreis: B. Morandi / Neu in der Académie des Sciences: E. Charpentier, J. Cossy, I. Marek / Max-Delbrück-Nachwuchspreis: S. Disch / Novartis Early Career Award: B. Morandi und R. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201801006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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