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Zhu C, Yang L, Chen C, Zeng G, Jiang W. Metal-free recycling of waste polyethylene terephthalate mediated by TBD protic ionic salts: the crucial role of anionic ligands. Phys Chem Chem Phys 2023; 25:27936-27941. [PMID: 37830243 DOI: 10.1039/d3cp03590e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
The structure-activity relationships of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) based protic ionic salts for polyethylene terephthalate (PET) glycolysis by ethylene glycol (EG) were comprehensively investigated through theoretical prediction and experimental verification. The proton capture ability of the anionic ligand from EG is positively correlated with the activity of the catalyst, as the generation of EG- was crucial for the chain breaking reaction via nucleophilic attack on the carbonyl group. Furthermore, density functional theory calculations demonstrated that the HTBD cation and anionic ligands work in a cooperative manner in the PET glycolysis reaction, where the ligands abstract a proton from EG to generate EG- and provide a proton to produce the bis(hydroxyalkyl)terephthalate (BHET) product. The rate-determining step is the nucleophilic attack step, where the Gibbs energy barriers (ΔG≠) increase in the order of 29.7 kcal mol-1 (HTBD-OAc) < 30.2 kcal mol-1 (HTBD-CH3CH2COO) < 31.4 kcal mol-1 (HTBD-HCOO) < 35.7 kcal mol-1 (HTBD-CH3COCOO) < 36.9 kcal mol-1 (HTBD-NO3). This is confirmed from the experimental results that the BHET yields decrease in the order of 84.8% (HTBD-OAc) > 82.4% (HTBD-CH3CH2COO) > 80.2% (HTBD-HCOO) > 73.6% (HTBD-CH3COCOO) > 4.7% (HTBD-NO3). These findings offer valuable guidance for designing more efficient metal-free protic ionic salts, promoting sustainable PET recycling.
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Affiliation(s)
- Chenxi Zhu
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
| | - Linlin Yang
- Kuang Yaming Honors School, Nanjing University, Nanjing 210023, China
| | - Chenhui Chen
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
| | - Guixiang Zeng
- Kuang Yaming Honors School, Nanjing University, Nanjing 210023, China
| | - Wei Jiang
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
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Takagi R, Duong DT, Ichiki T. Disulfonimide catalyzed asymmetric intramolecular hydroamination of alkenyl thioureas: Concentration effect in the hydroamination. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Guanidine-Amide-Catalyzed Aza-Henry Reaction of Isatin-Derived Ketimines: Origin of Selectivity and New Catalyst Design. Molecules 2021; 26:molecules26071965. [PMID: 33807341 PMCID: PMC8037019 DOI: 10.3390/molecules26071965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/29/2021] [Accepted: 03/29/2021] [Indexed: 12/05/2022] Open
Abstract
Density functional theory (DFT) calculations were performed to investigate the mechanism and the enantioselectivity of the aza-Henry reaction of isatin-derived ketimine catalyzed by chiral guanidine–amide catalysts at the M06-2X-D3/6-311+G(d,p)//M06-2X-D3/6-31G(d,p) (toluene, SMD) theoretical level. The catalytic reaction occurred via a three-step mechanism: (i) the deprotonation of nitromethane by a chiral guanidine–amide catalyst; (ii) formation of C–C bonds; (iii) H-transfer from guanidine to ketimine, accompanied with the regeneration of the catalyst. A dual activation model was proposed, in which the protonated guanidine activated the nitronate, and the amide moiety simultaneously interacted with the ketimine substrate by intermolecular hydrogen bonding. The repulsion of CPh3 group in guanidine as well as N-Boc group in ketimine raised the Pauli repulsion energy (∆EPauli) and the strain energy (∆Estrain) of reacting species in the unfavorable si-face pathway, contributing to a high level of stereoselectivity. A new catalyst with cyclopropenimine and 1,2-diphenylethylcarbamoyl as well as sulfonamide substituent was designed. The strong basicity of cyclopropenimine moiety accelerated the activation of CH3NO2 by decreasing the energy barrier in the deprotonation step. The repulsion between the N-Boc group in ketimine and cyclohexyl group as well as chiral backbone in the new catalyst raised the energy barrier in C–C bond formation along the si-face attack pathway, leading to the formation of R-configuration product. A possible synthetic route for the new catalyst is also suggested.
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Kee CW, Wong MW. Bicyclic Guanidine-Catalyzed Asymmetric Cycloaddition Reaction of Anthrones-Bifunctional Binding Modes and Origin of Stereoselectivity. J Org Chem 2020; 85:15139-15153. [PMID: 33175532 DOI: 10.1021/acs.joc.0c02008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We report a computational analysis of the [5,5] bicyclic guanidine-catalyzed asymmetric cycloaddition reaction of anthrones. Based on extensive conformational search of key intermediates and transition states on the potential energy surface and density functional theory calculations, we studied five plausible binding modes between the guanidine catalyst and substrates for this reaction. Our results indicate that the most favorable pathway is a stepwise conjugate addition-Aldol sequence via the dual hydrogen-bond binding mode. The predicted level of enantioselectivity is in good agreement with experimental values. Trends in variation of substrates and catalysts have also been reproduced by our calculations. Decomposition analysis revealed the significance of aromatic interactions in stabilizing the key enantioselectivity-determining transition state structures.
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Affiliation(s)
- Choon Wee Kee
- Process & Catalysis Research, Institute of Chemical and Engineering Sciences, 1 Pesek Road, Singapore 627899.,Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Ming Wah Wong
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
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Ashraf MA, Li C, Norouzi F, Zhang D. New insights into the Lewis acidity of guanidinium species: Lewis acid interaction provides reactivity. CR CHIM 2020. [DOI: 10.5802/crchim.16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Gimeno MC, Herrera RP. Hydrogen Bonding and Internal or External Lewis or Brønsted Acid Assisted (Thio)urea Catalysts. European J Org Chem 2019. [DOI: 10.1002/ejoc.201901344] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- M. Concepción Gimeno
- Departamento de Química Inorgánica; Instituto de Síntesis Química y Catálisis Homogénea (ISQCH) CSIC-Universidad de Zaragoza; C/ Pedro Cerbuna 12 50009 Zaragoza Spain
| | - Raquel P. Herrera
- Departamento de Química Orgánica. Laboratorio de Organocatálisis Asimétrica; Instituto de Síntesis Química y Catálisis Homogénea (ISQCH) CSIC-Universidad de Zaragoza; C/ Pedro Cerbuna 12 50009 Zaragoza Spain
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Kee CW, Peh KQE, Wong MW. Coupling Reactions of Alkynyl Indoles and CO 2 by Bicyclic Guanidine: Origin of Catalytic Activity? Chem Asian J 2017; 12:1780-1789. [PMID: 28582609 DOI: 10.1002/asia.201700338] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 04/11/2017] [Indexed: 01/05/2023]
Abstract
Density functional theory calculations were used to investigate the three possible modes of activation for the coupling of CO2 with alkynyl indoles in the presence of a guanidine base. The first of these mechanisms, involving electrophilic activation, was originally proposed by Skrydstrup et al. (Angew. Chem. Int. Ed. 2015, 54, 6682). The second mechanism involves the nucleophilic activation of CO2 . Both of these electrophilic and nucleophilic activation processes involve the formation of a guanidine-CO2 zwitterion adduct. We have proposed a third mechanism involving the bifunctional activation of the bicyclic guanidine catalyst, allowing for the simultaneous activation of the indole and CO2 by the catalyst. We demonstrated that a second molecule of catalyst is required to facilitate the final cyclization step. Based on the calculated turnover frequencies, our newly proposed bifunctional activation mechanism is the most plausible pathway for this reaction under these experimental conditions. Furthermore, we have shown that this bifunctional mode of activation is consistent with the experimental results. Thus, this guanidine-catalyzed reaction favors a specific-base catalyzed mechanism rather than the CO2 activation mechanism. We therefore believe that this bifunctional mechanism for the activation of bicyclic guanidine is typical of most CO2 coupling reactions.
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Affiliation(s)
- Choon Wee Kee
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore.,Chemical Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, UK
| | - Kai Qi Elizabeth Peh
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore
| | - Ming Wah Wong
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore, 117543, Singapore
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Berlinck RGS, Bertonha AF, Takaki M, Rodriguez JPG. The chemistry and biology of guanidine natural products. Nat Prod Rep 2017; 34:1264-1301. [DOI: 10.1039/c7np00037e] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The chemistry and biology of natural guanidines isolated from microbial culture media, from marine invertebrates, as well as from terrestrial plants and animals, are reviewed.
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Affiliation(s)
| | - Ariane F. Bertonha
- Instituto de Química de São Carlos
- Universidade de São Paulo
- São Carlos
- Brazil
| | - Mirelle Takaki
- Instituto de Química de São Carlos
- Universidade de São Paulo
- São Carlos
- Brazil
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Xue H, Tan CH, Wong MW. Guanidine-catalyzed asymmetric Strecker reaction: modes of activation and origin of stereoselectivity. CAN J CHEM 2016. [DOI: 10.1139/cjc-2016-0307] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Density functional theory calculations were employed to study the catalytic mechanism, modes of activation, and origin of enantioselectivity of guanidine-catalyzed asymmetric Strecker reaction of N-benzhydryl imine with hydrogen cyanide. Two types of bifunctional activation mode were identified, namely conventional bifunctional Brønsted acid activation and unconventional bifunctional Brønsted–Lewis acid activation. The lowest-energy transition states correspond to the conventional bifunctional mode of activation. The calculated enantiomeric excess, based on eight lowest-energy C–C bond forming transition states, is in good accord with observed enantioselectivity. NCI (noncovalent interaction) analysis of the key transition states reveals extensive noncovalent interactions, including aromatic interactions and hydrogen bonds, between the guanidinium catalyst and substrates. Multiple aryl–aryl interactions between the phenyl groups of guanidine catalyst and the phenyl rings of N-benzhydryl imine are the key stabilizations in the most stable (R)-inducing transition state. Differential attractive aryl–aryl stabilization is the major factor for stereoinduction.
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Affiliation(s)
- Hansong Xue
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
| | - Choon-Hong Tan
- Department of Chemistry and Biological Chemistry, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Ming Wah Wong
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
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Kee CW, Wong MW. Pentanidium-Catalyzed Asymmetric Phase-Transfer Conjugate Addition: Prediction of Stereoselectivity via DFT Calculations and Docking Sampling of Transition States, and Origin of Stereoselectivity. Aust J Chem 2016. [DOI: 10.1071/ch16225] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Density functional theory (DFT) study, at the M06–2X/6–311+G(d,p)//M06–2X/6–31G(d,p) level, was carried out to examine the catalytic mechanism and origin of stereoselectivity of pentanidium-catalyzed asymmetric phase-transfer conjugate addition. We employed a hybrid approach by combining automated conformation generation through molecular docking followed by subsequent DFT calculation to locate various possible transition states for the enantioselective conjugate addition. The calculated enantioselectivity (enantiomeric excess), based on the key diastereomeric C–C bond-forming transition states, is in good accord with experimental result. Non-covalent interaction analysis of the key transition states reveals extensive non-covalent interactions, including aromatic interactions, hydrogen bonds, and non-classical C–H⋯O interactions between the pentanidium catalyst and substrates. The origin of stereoselectivity was analysed using a strain-interaction model.
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