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Mariconda A, Iacopetta D, Sirignano M, Ceramella J, D'Amato A, Marra M, Pellegrino M, Sinicropi MS, Aquaro S, Longo P. Silver and Gold Complexes with NHC-Ligands Derived from Caffeine: Catalytic and Pharmacological Activity. Int J Mol Sci 2024; 25:2599. [PMID: 38473851 DOI: 10.3390/ijms25052599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 02/19/2024] [Accepted: 02/21/2024] [Indexed: 03/14/2024] Open
Abstract
N-heterocyclic carbene (NHC) silver(I) and gold(I) complexes have found different applications in various research fields, as in medicinal chemistry for their antiproliferative, anticancer, and antibacterial activity, and in chemistry as innovative and effective catalysts. The possibility of modulating the physicochemical properties, by acting on their ligands and substituents, makes them versatile tools for the development of novel metal-based compounds, mostly as anticancer compounds. As it is known, chemotherapy is commonly adopted for the clinical treatment of different cancers, even though its efficacy is hampered by several factors. Thus, the development of more effective and less toxic drugs is still an urgent need. Herein, we reported the synthesis and characterization of new silver(I) and gold(I) complexes stabilized by caffeine-derived NHC ligands, together with their biological and catalytic activities. Our data highlight the interesting properties of this series as effective catalysts in A3-coupling and hydroamination reactions and as promising anticancer, anti-inflammatory, and antioxidant agents. The ability of these complexes in regulating different pathological aspects, and often co-promoting causes, of cancer makes them ideal leads to be further structurally functionalized and investigated.
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Affiliation(s)
- Annaluisa Mariconda
- Department of Science, University of Basilicata, Via dell'Ateneo Lucano 10, 85100 Potenza, Italy
| | - Domenico Iacopetta
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, Italy
| | - Marco Sirignano
- Department of Chemistry and Biology "A. Zambelli", University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy
| | - Jessica Ceramella
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, Italy
| | - Assunta D'Amato
- Department of Chemistry and Biology "A. Zambelli", University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy
| | - Maria Marra
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, Italy
| | - Michele Pellegrino
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, Italy
| | - Maria Stefania Sinicropi
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, Italy
| | - Stefano Aquaro
- Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Via Pietro Bucci, 87036 Arcavacata di Rende, Italy
| | - Pasquale Longo
- Department of Chemistry and Biology "A. Zambelli", University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano, Italy
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Sirignano M, D’Amato A, Costabile C, Mariconda A, Crispini A, Scarpelli F, Longo P. Hydroamination of alkynes catalyzed by NHC-Gold(I) complexes: the non-monotonic effect of substituted arylamines on the catalyst activity. Front Chem 2023; 11:1260726. [PMID: 38124702 PMCID: PMC10731675 DOI: 10.3389/fchem.2023.1260726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 10/24/2023] [Indexed: 12/23/2023] Open
Abstract
Imines are valuable key compounds for synthesizing several nitrogen-containing molecules used in biological and industrial fields. They have been obtained, as highly regioselective Markovnikov products, by reacting several alkynes with arylamines in the presence of three new N-Heterocyclic carbene gold(I) complexes (3b, 4b, and 6b) together with the known 1-2b and 7b gold complexes as well as silver complexes 1-2a. Gold(I) complexes were investigated by means of NMR, mass spectroscopy, elemental analysis, and X-ray crystallographic studies. Accurate screening of co-catalysts and solvents led to identifying the best reaction conditions and the most active catalyst (2b) in the model hydroamination of phenylacetylene with aniline. Complex 2b was then tested in the hydroamination of alkynes with a wide variety of arylamines yielding a lower percentage of product when arylamines with both electron-withdrawing and electron-donating substituents were involved. Computational studies on the rate-determining step of hydroamination were conducted to shed light on the significantly different yields observed when reacting arylamines with different substituents.
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Affiliation(s)
- Marco Sirignano
- Department of Chemistry and Biology “A. Zambelli”, University of Salerno, Fisciano, Italy
| | - Assunta D’Amato
- Department of Chemistry and Biology “A. Zambelli”, University of Salerno, Fisciano, Italy
| | - Chiara Costabile
- Department of Chemistry and Biology “A. Zambelli”, University of Salerno, Fisciano, Italy
| | | | - Alessandra Crispini
- Department of Chemistry and Chemical Technologies, University of Calabria, Arcavacata Di Rende, Italy
| | - Francesca Scarpelli
- Department of Chemistry and Chemical Technologies, University of Calabria, Arcavacata Di Rende, Italy
| | - Pasquale Longo
- Department of Chemistry and Biology “A. Zambelli”, University of Salerno, Fisciano, Italy
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3
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Hussein AA, Ariffin A. Remote Steric and Electronic Effects of N-Heterocyclic Carbene Ligands on Alkene Reactivity and Regioselectivity toward Hydrocupration Reactions: The Role of Expanded-Ring N-Heterocyclic Carbenes. J Org Chem 2023; 88:13009-13021. [PMID: 37649423 DOI: 10.1021/acs.joc.3c01121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
The remote groups in N-heterocyclic carbene (NHC) ligands have a significant influence on metal-catalyzed reactions. We examine how remote bulkiness, electronic groups, and expanded-ring NHCs (ER-NHCs) influence alkene reactivity and regioselectivity toward hydrocupration using density functional theory calculations. The impact of remote steric bulkiness on the Cu-H insertion rate is analyzed, revealing a strong correlation between the steric substituent constant and rate ratio, where a bulky group increases the rate due to reduced steric effects in the transition state (TS). The steric properties of the examined catalysts (with a remote group R2 = CPh3, CHPh2, CH2Ph, CH3, and H) and their corresponding TSs are found to be modulated greatly by the remote steric substitution group and the ring size of the NHC ligand. Enhanced bulkiness enhances the nucleophilic Cu-H moiety. The remote electronic groups have a smaller impact on insertion barrier compared to that of steric hindrance. Furthermore, ER-NHC exploration indicates that NHCs with over five-membered rings have a significantly negative influence on the reaction rate. Finally, with a highly bulky group (R2 = CPh3), anti-Markovnikov insertion preference is attributed to high interaction energy and improved steric properties. Overall, our findings here provide valuable insights for the development of a more effective catalyst in metal-catalyzed reactions.
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Affiliation(s)
- Aqeel A Hussein
- Department of Medical Laboratory Science, College of Science, Komar University of Science and Technology, Sulaymaniyah, Kurdistan Region 46001, Iraq
- Department of Biology, College of Science, Al-Qasim Green University, Al-Qassim, Babylon 51013, Iraq
| | - Azhar Ariffin
- Department of Chemistry, Faculty of Science, University Malaya, Kuala Lumpur 50603, Malaysia
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4
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Vanden Broeck SMP, Tzouras NV, Saab M, Van Hecke K, Dereli B, Ritacco I, Cavallo L, Vougioukalakis GC, Braunstein P, Nolan SP, Danopoulos AA, Cazin CSJ. Gold complexes with remote-substituted amino N-heterocyclic carbenes. Dalton Trans 2023; 52:9908-9912. [PMID: 37458362 DOI: 10.1039/d3dt02086j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
The 4-RN-1,3-Ar2-imidazolium salt, R = iPr, tBu, Ar = Mes, Dipp, Mes = mesityl, Dipp = 2,6-bis-diisopropyl-phenyl was metalated by AuI at the C2-, C5- and 4-RN positions depending on the reactants and conditions employed; a rare direct rearrangement of a AuI aminide to an abnormal imidazol-5-ylidene AuI complex was also observed and based on a DFT study it may involve TfO- facilitated H+ transfer.
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Affiliation(s)
- Sofie M P Vanden Broeck
- Department of Chemistry and Centre of Sustainable Chemistry, Ghent University, Krijgslaan 281, S-3, 9000 Ghent, Belgium.
| | - Nikolaos V Tzouras
- Department of Chemistry and Centre of Sustainable Chemistry, Ghent University, Krijgslaan 281, S-3, 9000 Ghent, Belgium.
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771 Athens, Greece.
| | - Marina Saab
- Department of Chemistry and Centre of Sustainable Chemistry, Ghent University, Krijgslaan 281, S-3, 9000 Ghent, Belgium.
| | - Kristof Van Hecke
- Department of Chemistry and Centre of Sustainable Chemistry, Ghent University, Krijgslaan 281, S-3, 9000 Ghent, Belgium.
| | - Busra Dereli
- KAUST Catalysis Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Ida Ritacco
- Dipartimento di Chimica e Biologia, Università di Salerno, Fisciano 84084, Italy
| | - Luigi Cavallo
- KAUST Catalysis Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
- Dipartimento di Chimica e Biologia, Università di Salerno, Fisciano 84084, Italy
| | - Georgios C Vougioukalakis
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771 Athens, Greece.
| | - Pierre Braunstein
- Université de Strasbourg, CNRS, Institut de Chimie UMR 7177, Strasbourg 67081, Cedex, France
| | - Steven P Nolan
- Department of Chemistry and Centre of Sustainable Chemistry, Ghent University, Krijgslaan 281, S-3, 9000 Ghent, Belgium.
| | - Andreas A Danopoulos
- Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771 Athens, Greece.
| | - Catherine S J Cazin
- Department of Chemistry and Centre of Sustainable Chemistry, Ghent University, Krijgslaan 281, S-3, 9000 Ghent, Belgium.
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Abstract
Until the year 2000, gold compounds were considered catalytically inert. Subsequently, it was found that they are able to promote the nucleophilic attack on unsaturated substrates by forming an Au–π-system. The main limitation in the use of these catalytic systems is the ease with which they decompose, which is avoided by stabilization with an ancillary ligand. N-heterocyclic carbenes (NHCs), having interesting s-donor capacities, are able to stabilize the gold complexes (Au (I/III) NHC), favoring the exploration of their catalytic activity. This review reports the state of the art (years 2007–2022) in the nucleophilic addition of amines (hydroamination) and water (hydration) to the terminal and internal alkynes catalyzed by N-heterocyclic carbene gold (I/III) complexes. These reactions are particularly interesting both because they are environmentally sustainable and because they lead to the production of important intermediates in the chemical and pharmaceutical industry. In fact, they have an atom economy of 100%, and lead to the formation of imines and enamines, as well as the formation of ketones and enols, all important scaffolds in the synthesis of bioactive molecules, drugs, heterocycles, polymers, and bulk and fine chemicals.
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6
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Ma Y, Ali HS, Hussein AA. A mechanistic study on the gold(i)-catalyzed cyclization of propargylic amide: revealing the impact of expanded-ring N-heterocyclic carbenes. Catal Sci Technol 2022. [DOI: 10.1039/d1cy01617b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Density functional theory (DFT) was applied to understand the mechanistic pathway of the gold(i)-catalyzed cyclization of propargylic amide, and to reveal the impact of expanded-ring N-heterocyclic carbenes.
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Affiliation(s)
- Yumiao Ma
- BSJ Institute, Haidian, Beijing, 100084, People's Republic of China
- Hangzhou Yanqu Information Technology Co., Ltd., Xixi Legu Creative Pioneering Park, No. 712 Wen'er West Road, Xihu District, Hangzhou City, Zhejiang Province, 310003, People's Republic of China
| | - Hafiz Saqib Ali
- School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Rd, Kings Buildings, EH9 3FJ Edinburgh, UK
| | - Aqeel A. Hussein
- Department of Pharmacy, College of Medicine, Komar University of Science and Technology, Sulaymaniyah, Kurdistan Region, Iraq
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7
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Li J, Li X, Sun L, Wang X, Yuan L, Wu L, Liu X, Wang Y. Syntheses of Triangular Gold Complexes and Their Applications in Hydroamination Reaction. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Jia Li
- Department of Chemistry and Chemical Engineering Liaocheng University 252059 Liaocheng China
| | - Xujun Li
- Department of Chemistry and Chemical Engineering Liaocheng University 252059 Liaocheng China
| | - Lei Sun
- Department of Chemistry and Chemical Engineering Liaocheng University 252059 Liaocheng China
| | - Xiaoshuang Wang
- Department of Chemistry and Chemical Engineering Liaocheng University 252059 Liaocheng China
| | - Lixia Yuan
- Department of Chemistry and Chemical Engineering Liaocheng University 252059 Liaocheng China
| | - Lingang Wu
- Department of Chemistry and Chemical Engineering Liaocheng University 252059 Liaocheng China
| | - Xiang Liu
- College of Materials and Chemical Engineering Key laboratory of Inorganic Nonmetallic Crystalline and Energy Conversion Materials Material Analysis and Testing center China Three Gorges University Yichang Hubei 443002 China
| | - Yanlan Wang
- Department of Chemistry and Chemical Engineering Liaocheng University 252059 Liaocheng China
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Collado A, Nelson DJ, Nolan SP. Optimizing Catalyst and Reaction Conditions in Gold(I) Catalysis-Ligand Development. Chem Rev 2021; 121:8559-8612. [PMID: 34259505 DOI: 10.1021/acs.chemrev.0c01320] [Citation(s) in RCA: 68] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
This review considers phosphine and N-heterocyclic carbene complexes of gold(I) that are used as (pre)catalysts for a range of reactions in organic synthesis. These are divided according to the structure of the ligand, with the narrative focusing on studies that offer a quantitative comparison between the ligands and readily available or widely used existing systems.
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Affiliation(s)
- Alba Collado
- Departamento de Química Inorgánica, Universidad Autónoma de Madrid, C/Francisco Tomás y Valiente, 7, 28049 Madrid, Spain
| | - David J Nelson
- WestCHEM Department of Pure & Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland
| | - Steven P Nolan
- Department of Chemistry and Center for Sustainable Chemistry, Ghent University, Krijgslaan 281 - S3, 9000 Gent, Belgium
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9
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Jónsson HF, Orthaber A, Fiksdahl A. Studies on gold(I) and gold(III) alcohol functionalised NHC complexes. Dalton Trans 2021; 50:5128-5138. [PMID: 33720256 DOI: 10.1039/d1dt00387a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Five pairs of novel chiral alcohol functionalised gold(i) and gold(iii) NHC complexes derived from chiral amino alcohols, were synthesized and characterised (NMR, IR, HRMS). Single crystal X-ray diffraction data of gold(i) and gold(iii) complexes are reported and discussed. The chiral imidazolium preligands were readily synthesized via the oxalamides, subsequent reduction and final orthoformate condensation. An improved method was used for generation of gold(i) NHC complexes (up to 92%) and further oxidation afforded the corresponding gold(iii) NHC complexes (up to 99%). All the Au(i) and Au(iii) NHC complexes proved far more catalytically active in a 1,6-enyne alkoxycyclization test reaction than our previously tested N,N- and P,N-ligated Au(iii) complexes. Comparative gold(i) and gold(iii) catalytic studies demonstrated different catalytic ability, depending on the NHC ligand flexibility and bulkiness. Excellent yields (92-99%) of target alkoxycyclization product were obtained with both gold(i) and gold(iii) complexes with the bulky N1-Mes-N2-ethanol based NHC ligand.
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Affiliation(s)
- Helgi Freyr Jónsson
- Department of Chemistry, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
| | - Andreas Orthaber
- Department of Organic Chemistry - Ångström Laboratory, Uppsala University, Lägerhyddsvägen 1, 751 20, Uppsala, Sweden
| | - Anne Fiksdahl
- Department of Chemistry, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
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Reiersølmoen AC, Battaglia S, Orthaber A, Lindh R, Erdélyi M, Fiksdahl A. P, N-Chelated Gold(III) Complexes: Structure and Reactivity. Inorg Chem 2021; 60:2847-2855. [PMID: 33169989 PMCID: PMC7927145 DOI: 10.1021/acs.inorgchem.0c02720] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Gold(III) complexes are versatile catalysts offering a growing number of new synthetic transformations. Our current understanding of the mechanism of homogeneous gold(III) catalysis is, however, limited, with that of phosphorus-containing complexes being hitherto underexplored. The ease of phosphorus oxidation by gold(III) has so far hindered the use of phosphorus ligands in the context of gold(III) catalysis. We present a method for the generation of P,N-chelated gold(III) complexes that circumvents ligand oxidation and offers full counterion control, avoiding the unwanted formation of AuCl4-. On the basis of NMR spectroscopic, X-ray crystallographic, and density functional theory analyses, we assess the mechanism of formation of the active catalyst and of gold(III)-mediated styrene cyclopropanation with propargyl ester and intramolecular alkoxycyclization of 1,6-enyne. P,N-chelated gold(III) complexes are demonstrated to be straightforward to generate and be catalytically active in synthetically useful transformations of complex molecules.
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Affiliation(s)
- Ann Christin Reiersølmoen
- Department of Chemistry, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway
| | - Stefano Battaglia
- Department of Chemistry-BMC Uppsala University, Husargatan 3, 75237 Uppsala, Sweden
| | - Andreas Orthaber
- Ångström Laboratory, Department of Organic Chemistry, Uppsala University, Lägerhyddsvägen 1, 75120 Uppsala, Sweden
| | - Roland Lindh
- Department of Chemistry-BMC Uppsala University, Husargatan 3, 75237 Uppsala, Sweden
| | - Máté Erdélyi
- Department of Chemistry-BMC Uppsala University, Husargatan 3, 75237 Uppsala, Sweden
| | - Anne Fiksdahl
- Department of Chemistry, Norwegian University of Science and Technology, Høgskoleringen 5, 7491 Trondheim, Norway
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11
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Rocchigiani L, Bochmann M. Recent Advances in Gold(III) Chemistry: Structure, Bonding, Reactivity, and Role in Homogeneous Catalysis. Chem Rev 2020; 121:8364-8451. [DOI: 10.1021/acs.chemrev.0c00552] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Luca Rocchigiani
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR47TJ, United Kingdom
| | - Manfred Bochmann
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR47TJ, United Kingdom
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12
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Evaluating the electronic properties of ditopic and hetero-ditopic ligands derived from benzimidazole and pyrazole by 13C NMR spectroscopy. J Organomet Chem 2020. [DOI: 10.1016/j.jorganchem.2020.121409] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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13
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Abstract
A library of 14 heterobis(carbene) complexes of the general formula [Au(iPr2-bimy)(ADC)]BF4 (7-20) containing the N-heterocyclic carbene reporter iPr2-bimy and various protic acyclic diaminocarbenes (ADCs) have been prepared to estimate their stereoelectronic properties by 13C NMR spectroscopy and percentage buried volume (%Vbur) determinations. Their preparation was achieved by nucleophilic attack of five secondary amines on six mixed NHC/isocyanide complexes of the type [Au(iPr2-bimy)(CN-R)]BF4 (1-6). Analyses of the iPr2-bimy carbene signals reveal that protic ADCs are stronger donors than classical and expanded-ring NHCs. On the other hand, they are weaker donating compared to NHCs with reduced-heteroatom stabilization. Moreover, stereoelectronic fine-tuning of these ligands is possible by a diverse range of substituents originating from the employed isocyanides and amines.
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Affiliation(s)
- Chandan Singh
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Anuj Kumar
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Han Vinh Huynh
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
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14
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Cervantes‐Reyes A, Rominger F, Hashmi ASK. Sterically Demanding Ag I and Cu I N-Heterocyclic Carbene Complexes: Synthesis, Structures, Steric Parameters, and Catalytic Activity. Chemistry 2020; 26:5530-5540. [PMID: 32104933 PMCID: PMC7216994 DOI: 10.1002/chem.202000600] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 02/27/2020] [Indexed: 12/13/2022]
Abstract
The synthesis and full characterization of new air-stable AgI and CuI complexes bearing structurally bulky expanded-ring N-heterocyclic carbene (erNHC) ligands is presented. The condensation of protonated NHC salts with Ag2 O afforded a collection of AgI complexes, and their first use as ligand transfer reagents led to novel isostructural CuI or AuI complexes. In situ deprotonation of the NHC salts in the presence of a copper(I) source, provides a library of new CuI complexes. The solid-state structures feature large N-CNHC -N angles (118-128°) and almost identical angles between the aryl groups on the nitrogen atoms and the plane of the N-C-N unit of the carbene (i.e. torsion angles close to 0°). Among the steric parameters, the percent buried volume (%Vbur ) values span easily in the 50-57 % range, and that one of (9-Dipp)CuBr complex (%Vbur =57.5) overcomes to other known erNHC-metal complexes reported to date. Preliminary catalytic experiments in the copper-catalyzed coupling between N-tosylhydrazone and phenylacetylene, afforded 76-93 % product at the 0.5-2.5 mol % catalyst loading, proving the stability of CuI erNHC complexes at elevated temperatures (100 °C).
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Affiliation(s)
| | - Frank Rominger
- Organisch-Chemisches InstitutHeidelberg UniversityIm Neuenheimer Feld 27069120HeidelbergGermany
| | - A. Stephen K. Hashmi
- Organisch-Chemisches InstitutHeidelberg UniversityIm Neuenheimer Feld 27069120HeidelbergGermany
- Chemistry DepartmentFaculty of ScienceKing Abdulaziz UniversityJeddah21589Saudi Arabia
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15
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Gold(I) Complexes with Eight‐Membered NHC Ligands: Synthesis, Structures and Catalytic Activity. Adv Synth Catal 2020. [DOI: 10.1002/adsc.202000281] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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16
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Recent Progress in N-Heterocyclic Carbene Gold-Catalyzed Reactions of Alkynes Involving Oxidation/Amination/Cycloaddition. Catalysts 2020. [DOI: 10.3390/catal10030350] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Recent rapid development in homogeneous gold catalysis affords an alternative and particularly thriving strategy for the generation of gold carbenes through gold-catalyzed oxidation/amination/cycloaddition of alkynes, while it avoids the employment of hazardous and potentially explosive diazo compounds as starting materials for carbene generation. In addition to facile and secure operation, gold carbenes generated in this strategy display good chemoselectivity distinct from other metal carbenes produced from the related diazo approach. N-heterocyclic carbene (NHC) gold is a special metal complex that can be used as ancillary ligands, which provides enhanced stability and can also act as an efficient chiral directing group. In this review, we will present an overview of these recent advances in alkyne oxidation/amination/cycloaddition by highlighting their specificity and applicability, aiming to facilitate progress in this very exciting area of research.
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