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Huang Y, Peng X, Li T. Recent Advances in NHC-Catalyzed Chemoselective Activation of Carbonyl Compounds. Chem Asian J 2024; 19:e202400097. [PMID: 38451172 DOI: 10.1002/asia.202400097] [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: 01/29/2024] [Revised: 03/05/2024] [Accepted: 03/06/2024] [Indexed: 03/08/2024]
Abstract
N-Heterocyclic carbenes (NHCs) catalysts have been employed as effective tools in the development of various reactions, which have made notable contributions in developing diverse reaction modes and generating significant functionalized molecules. This review provides an overview of the recent advancements in the chemo- and regioselective activation of different aldehydes using NHCs, categorized into five parts based on the different activation modes. A brief conclusion and outlook is provided to stimulate the development of novel activation modes for accessing functional molecules.
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Affiliation(s)
- Yixian Huang
- State Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang, 550025, China
| | - Xiaolin Peng
- State Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang, 550025, China
| | - Tingting Li
- State Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Center for R&D of Fine Chemicals of Guizhou University, Guiyang, 550025, China
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2
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Larcombe CN, Malins LR. Accessing Diverse Cross-Benzoin and α-Siloxy Ketone Products via Acyl Substitution Chemistry. J Org Chem 2022; 87:9408-9413. [PMID: 35758296 DOI: 10.1021/acs.joc.2c00801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An approach to diverse cross-benzoin and α-siloxy ketone products which leverages a simple yet underutilized C-C bond disconnection strategy is reported. Acyl substitution of readily accessible α-siloxy Weinreb amides with organolithium compounds enables access to a broad scope of aryl, heteroaryl, alkyl, alkenyl, and alkynyl derivatives. Enantiopure benzoins can be accessed via a chiral pool approach, and the utility of accessible cross-benzoins and α-siloxy ketones is highlighted in a suite of downstream synthetic applications.
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Affiliation(s)
- Chloe N Larcombe
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Lara R Malins
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
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Triazolium Salt Organocatalysis: Mechanistic Evaluation of Unusual Ortho-Substituent Effects on Deprotonation. Catalysts 2021. [DOI: 10.3390/catal11091055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Organocatalysis by N-heterocyclic carbenes is normally initiated by the deprotonation of precursor azolium ions to form active nucleophilic species. Substituent effects on deprotonation have an impact on catalytic efficiency and provide insight into general catalytic mechanisms by commonly used azolium systems. Using an NMR kinetic method for the analysis of C(3)-H/D exchange, we determined log kex–pD profiles for three ortho-substituted N-aryl triazolium salts, which enables a detailed analysis of ortho-substituent effects on deprotonation. This includes N-5-methoxypyrid-2-yl triazolium salt 7 and di-ortho-methoxy and di-ortho-isopropoxyphenyl triazolium salts 8 and 9, and we acquired additional kinetic data to supplement our previously published analysis of N-pyrid-2-yl triazolium salt 6. For 2-pyridyl triazoliums 6 and 7, novel acid catalysis of C(3)-H/D exchange is observed under acidic conditions. These kinetic data were supplemented by DFT analyses of the conformational preferences of 6 upon N-protonation. A C(3) deprotonation mechanism involving intramolecular general base deprotonation by the pyridyl nitrogen of the N(1)-deuterated dicationic triazolium salt is most consistent with the data. We also report kDO values (protofugalities) for deuteroxide-catalyzed exchange for 6–9. The protofugalities for 8 and 9 are the lowest values to date in the N-aryl triazolium series.
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Spin-Crossover in Iron(II) Complexes of N,N′-Disubstituted 2,6-Bis(Pyrazol-3-yl)Pyridines: An Effect of a Distal Substituent in the 2,6-Dibromophenyl Group. CRYSTALS 2021. [DOI: 10.3390/cryst11080922] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A series of new bis(pyrazol-3-yl)pyridines (LR) N,N′-disubstituted by 4-functionalized 2,6-dibromophenyl groups have been synthesized to study the effect of a distal substituent on the spin-crossover (SCO) behaviour of the iron(II) complexes [Fe(LR)2](ClO4)2 by variable-temperature magnetometry, NMR spectroscopy, and X-ray diffraction. The SCO-assisting tendency of the substituents with different electronic and steric properties (i.e., the bromine atom and the methyl group) in the para-position of the 2,6-dibromophenyl group is discussed. Together with earlier reported SCO-active iron(II) complexes with N,N′-disubstituted bis(pyrazol-3-yl)pyridines, these new complexes open the way for this family of SCO compounds to emerge as an effective ‘tool’ in revealing structure–function relations, a prerequisite for successful molecular design of switchable materials for future breakthrough applications in sensing, switching, and memory devices.
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Onodera K, Takashima R, Suzuki Y. Selective Synthesis of Acylated Cross-Benzoins from Acylals and Aldehydes via N-Heterocyclic Carbene Catalysis. Org Lett 2021; 23:4197-4202. [PMID: 33999632 DOI: 10.1021/acs.orglett.1c01134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The utility of acylals as building blocks for selective cross-benzoin synthesis was explored in this study. The synthesis of α-acetoxyketones (O-acyl cross-benzoins) was achieved via selective N-heterocyclic carbene-catalyzed cross-benzoin reactions using acylals as aldehyde equivalents. Thus, the combination of ortho-substituted phenyl acylals and aromatic/aliphatic aldehydes as coupling substrates using bicyclic triazolium salts as precatalysts and potassium carbonate as a base in THF at reflux temperature selectively yielded O-acyl cross-benzoins.
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Affiliation(s)
- Kou Onodera
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
| | - Ryo Takashima
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
| | - Yumiko Suzuki
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
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Ma L, Yu Y, Xin L, Zhu L, Xia J, Ou P, Huang X. Visible Light Enabled Formal Cross Silyl Benzoin Reaction as an Access to α‐Hydroxyketones. Adv Synth Catal 2021. [DOI: 10.1002/adsc.202100186] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Liyao Ma
- Key Laboratory of Coal to Ethylene Glycol and Its Related Technology Center for Excellence in Molecular Synthesis Fujian Institute of Research on the Structure of Matter Fujian College Chinese Academy of Sciences Fuzhou Fujian 350002 People's Republic of China
- College of Chemistry Fuzhou University Fuzhou 350116 People's Republic of China
| | - Yinghua Yu
- Key Laboratory of Coal to Ethylene Glycol and Its Related Technology Center for Excellence in Molecular Synthesis Fujian Institute of Research on the Structure of Matter Fujian College Chinese Academy of Sciences Fuzhou Fujian 350002 People's Republic of China
| | - Luoting Xin
- Key Laboratory of Coal to Ethylene Glycol and Its Related Technology Center for Excellence in Molecular Synthesis Fujian Institute of Research on the Structure of Matter Fujian College Chinese Academy of Sciences Fuzhou Fujian 350002 People's Republic of China
| | - Lei Zhu
- Key Laboratory of Coal to Ethylene Glycol and Its Related Technology Center for Excellence in Molecular Synthesis Fujian Institute of Research on the Structure of Matter Fujian College Chinese Academy of Sciences Fuzhou Fujian 350002 People's Republic of China
| | - Jiajin Xia
- Key Laboratory of Coal to Ethylene Glycol and Its Related Technology Center for Excellence in Molecular Synthesis Fujian Institute of Research on the Structure of Matter Fujian College Chinese Academy of Sciences Fuzhou Fujian 350002 People's Republic of China
| | - Pengcheng Ou
- Key Laboratory of Coal to Ethylene Glycol and Its Related Technology Center for Excellence in Molecular Synthesis Fujian Institute of Research on the Structure of Matter Fujian College Chinese Academy of Sciences Fuzhou Fujian 350002 People's Republic of China
- College of Chemistry Fuzhou University Fuzhou 350116 People's Republic of China
| | - Xueliang Huang
- Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research Ministry of Education of China Key Laboratory of the Assembly and Application of Organic Functional Molecules of Hunan Province College of Chemistry and Chemical Engineering Hunan Normal University Changsha Hunan 410081 People's Republic of China
- Key Laboratory of Coal to Ethylene Glycol and Its Related Technology Center for Excellence in Molecular Synthesis Fujian Institute of Research on the Structure of Matter Fujian College Chinese Academy of Sciences Fuzhou Fujian 350002 People's Republic of China
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Delany EG, Connon SJ. Enantioselective N-heterocyclic carbene-catalysed intermolecular crossed benzoin condensations: improved catalyst design and the role of in situ racemisation. Org Biomol Chem 2021; 19:248-258. [PMID: 33289760 DOI: 10.1039/d0ob02017f] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The enantioselective intermolecular crossed-benzoin condensation mediated by novel chiral N-heterocyclic carbenes derived from pyroglutamic acid has been investigated. A small library of chiral triazolium ions were synthesised. Each possessed a tertiary alcohol H-bond donor and a variable N-aryl substituent. It was found that increasing both the steric requirement and the electron-withdrawing characteristics of the N-aryl ring led to more chemoselective, efficient and enantioselective chemistry, however both quenching the reaction at different times and deuterium incorporation experiments involving the product revealed that this is complicated by product racemisation in situ (except in the case of benzoin itself), which explains the dependence of enantioselectivity on the electrophilicity of the reacting aldehydes common in the literature. Subsequent protocol optimisation, where one reacting partner was an o-substituted benzaldehyde, allowed a range of crossed-benzoins to be synthesised in moderate-good yields with moderate to excellent enantioselectivity.
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Affiliation(s)
- Eoghan G Delany
- Centre for Synthesis and Chemical Biology, Trinity Biomedical Sciences Institute, School of Chemistry, The University of Dublin, Trinity College, Dublin 2, Ireland.
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Iwai K, Ono M, Nanjo Y, Ema T. Minimization of Amounts of Catalyst and Solvent in NHC-Catalyzed Benzoin Reactions of Solid Aldehydes: Mechanistic Consideration of Solid-to-Solid Conversion and Total Synthesis of Isodarparvinol B. ACS OMEGA 2020; 5:10207-10216. [PMID: 32391509 PMCID: PMC7203951 DOI: 10.1021/acsomega.0c01141] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 04/08/2020] [Indexed: 05/03/2023]
Abstract
Attempts were made to minimize the amounts of catalyst and solvent in the NHC-catalyzed benzoin reactions of solid aldehydes. In some case, solid-to-solid conversions proceeded in the solvent-free NHC-catalyzed benzoin reactions. Even if a mixture of the substrate, N-heterocyclic carbene (NHC) precursor, and inorganic base was initially a powdery solid, the reaction did proceed at reaction temperature lower than the melting points of each compound. The solid mixture partially melted or became a slurry or suspension in the meantime. We call this solid/liquid mixture a semisolid state. The reaction giving an optically active product was faster than that giving a racemic mixture of the same product. Melting-point depression was observed for a series of mixtures of the substrate and product in different substrate/product ratios. Solvent-free solid-to-solid conversions were accelerated by the formation of a semisolid state resulting from the melting-point depression of the solid substrate accompanied by the product formation. In the case of solid substrates with high melting points, melting-point depression was useless, and the addition of a small amount of solvent was needed. The first total synthesis of isodarparvinol B was achieved via the NHC-catalyzed intramolecular benzoin reaction using a small amount of solvent as an additive.
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Kumar S. Recent Advances in the Schiff Bases and
N
‐Heterocyclic Carbenes as Ligands in the Cross‐Coupling Reactions: A Comprehensive Review. J Heterocycl Chem 2019. [DOI: 10.1002/jhet.3504] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Sumit Kumar
- Department of Chemistry Central University of Haryana Jant‐Pali Mahendergarh 123031 India
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Zhu J, Fang S, Sun K, Fang C, Lu T, Du D. N-Heterocyclic Carbene-Catalyzed Formal Conjugate Hydroacylation: An Atom-Economic Synthesis of 1H-Indol-3-yl Esters. J Org Chem 2018; 83:10430-10435. [DOI: 10.1021/acs.joc.8b01488] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Jindong Zhu
- State Key Laboratory of Natural Medicines, Department of Organic Chemistry, China Pharmaceutical University, Nanjing 210009, P. R. China
| | - Shuaishuai Fang
- State Key Laboratory of Natural Medicines, Department of Organic Chemistry, China Pharmaceutical University, Nanjing 210009, P. R. China
| | - Kewen Sun
- State Key Laboratory of Natural Medicines, Department of Organic Chemistry, China Pharmaceutical University, Nanjing 210009, P. R. China
| | - Chao Fang
- State Key Laboratory of Natural Medicines, Department of Organic Chemistry, China Pharmaceutical University, Nanjing 210009, P. R. China
| | - Tao Lu
- State Key Laboratory of Natural Medicines, Department of Organic Chemistry, China Pharmaceutical University, Nanjing 210009, P. R. China
| | - Ding Du
- State Key Laboratory of Natural Medicines, Department of Organic Chemistry, China Pharmaceutical University, Nanjing 210009, P. R. China
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