1
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Guan Y, Chang K, Su Y, Xu X, Xu X. Frustrated Lewis Pair-Type Reactivity of Intermolecular Rare-Earth Aryloxide and N-Heterocyclic Carbene/Olefin Combinations. Chem Asian J 2024; 19:e202400190. [PMID: 38451014 DOI: 10.1002/asia.202400190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 03/05/2024] [Accepted: 03/06/2024] [Indexed: 03/08/2024]
Abstract
This work reports the cooperative reactivity of rare-earth aryloxide complexes with N-heterocyclic carbene (NHC) or N-heterocyclic olefin (NHO), showcasing their synergistic effect on the activation of H2 and diverse organic substrates. Reactions of RE(OAr)3 (RE=La, Sm, and Y; Ar=2,6-tBu2-C6H3) with unsaturated NHC ItBu (:C[N(R)CH]2, R=tBu) isolated abnormally bound RE metal NHC complexes RE/aNHC. In contrast, no metal-NHO adducts were formed when RE(OAr)3 were treated with NHO (R2C=C[N(R)C(R)]2, R=CH3). Both RE/aNHC and RE/NHO Lewis pairs enabled cooperative H2 activation. Furthermore, RE(OAr)3 were found to catalyze the hydrogenation of the exocyclic C=C double bond of NHO under mild conditions. Moreover, treatment of the La/aNHC complex with benzaldehyde produced a La/C4 1,2-addition product. The La/NHO Lewis pair could react with (trimethylsilyl)diazomethane and α, β-conjugated imine, affording an isocyanotrimethylsilyl lanthanum amide complex and a La/C 1,4-addition product, respectively.
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Affiliation(s)
- Yiwen Guan
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123, Suzhou, P. R. China
| | - Kejian Chang
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123, Suzhou, P. R. China
| | - Yujie Su
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123, Suzhou, P. R. China
| | - Xian Xu
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123, Suzhou, P. R. China
| | - Xin Xu
- Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, 215123, Suzhou, P. R. China
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2
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Zhang W, Li Y, Liang SH. Radiodifluoromethylation of well-functionalized molecules. Am J Nucl Med Mol Imaging 2024; 14:82-86. [PMID: 38737642 PMCID: PMC11087296 DOI: 10.62347/iiog5660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Accepted: 04/02/2024] [Indexed: 05/14/2024]
Abstract
The strategic installation of a [18F]fluorine atom at the specific position of the lead molecule is a never-ending challenge for radiochemists in their endeavour to develop novel positron emission tomography (PET) imaging applications. Although the radiosynthesis of [18F]CF2H-containing molecules has been explored in the past decade, more methods need to be explored for various well-functionalized compounds. Recently, two novel strategies of radiodifluoromethylation were reported, namely the utilization of [18F]difluorocarbene building block and frustrated Lewis pair-mediated C-18F bond formation, respectively. These methods provide an efficient radiofunctionalization of complex CF2H-containing molecules for drug discovery and PET ligand development.
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Affiliation(s)
- Wei Zhang
- Department of Radiology and Imaging Sciences, Emory University Atlanta, Georgia 30322, USA
| | - Yinlong Li
- Department of Radiology and Imaging Sciences, Emory University Atlanta, Georgia 30322, USA
| | - Steven H Liang
- Department of Radiology and Imaging Sciences, Emory University Atlanta, Georgia 30322, USA
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3
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He Y, Liu Y, Chen C, Wang X, Li C, Chen XB, Shi Z, Feng S. Defect-Induced All-Solid-State Frustrated Lewis Pair on Metal-Organic Monolayer Accelerating Photocatalytic CO 2 Reduction with H 2O Vapor. Nano Lett 2024. [PMID: 38620050 DOI: 10.1021/acs.nanolett.4c00903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
Understanding the structure-performance relationships of a frustrated Lewis pair (FLP) at the atomic level is key to yielding high efficiency in activating chemically "inert" molecules into value-added products. A sound strategy was developed herein through incorporating oxygen defects into a Zr-based metal-organic layer (Zr-MOL-D) and employing Lewis basic proximal surface hydroxyls for the in situ formation of solid heterogeneous FLP (Zr4-δ-VO-Zr-OH). Zr-MOL-D exhibits a superior CO2 to CO conversion rate of 49.4 μmol g-1 h-1 in water vapor without any sacrificing agent or photosensitizer, which is about 12 times higher than that of pure MOL (Zr-MOL-P), with extreme stability even after being placed for half a year. Theoretical and experimental results reveal that the introduction of FLP converts the process of the crucial intermediate COOH* from an endothermic reaction to an exothermic spontaneous reaction. This work is expected to provide new prospects for developing efficient MOL-based photocatalysts in FLP chemistry through a sound defect-engineering strategy.
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Affiliation(s)
- Yiqiang He
- College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, China
| | - Yuxin Liu
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People's Republic of China
| | - Cailing Chen
- Advanced Membranes and Porous Materials Center, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Xiyang Wang
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People's Republic of China
| | - Chunguang Li
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People's Republic of China
| | - Xiao-Bo Chen
- School of Engineering, RMIT University, Carlton, VIC 3053, Australia
| | - Zhan Shi
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People's Republic of China
| | - Shouhua Feng
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, People's Republic of China
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4
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Csókás D, Mondal B, Đokić M, Gupta R, Lee BJY, Young RD. Stereoselective Synthesis of Fluoroalkanes via FLP Mediated Monoselective C─F Activation of Geminal Difluoroalkanes. Adv Sci (Weinh) 2023; 10:e2305768. [PMID: 37907424 PMCID: PMC10754124 DOI: 10.1002/advs.202305768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Indexed: 11/02/2023]
Abstract
A method of desymmetrization of geminal difluoroalkanes using frustrated Lewis pair (FLP) mediated monoselective C-F activation where a chiral sulfide is the Lewis base component is reported. The stereoselective reaction provides generally high yields of diastereomeric sulfonium salts with dr of up to 95:5. The distribution of diastereomers is found to be thermodynamically controlled via facile sulfide exchange. The use of enantiopure chiral sulfides allows for high stereospecificity in nucleophilic substitution reactions and the formation of stereoenriched products.
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Affiliation(s)
- Dániel Csókás
- Department of ChemistryNational University of SingaporeSingapore117543Singapore
- Research Centre for Natural SciencesInstitute of Organic ChemistryBudapest1117Hungary
| | - Bivas Mondal
- Department of ChemistryNational University of SingaporeSingapore117543Singapore
| | - Miloš Đokić
- Department of ChemistryNational University of SingaporeSingapore117543Singapore
| | - Richa Gupta
- Department of ChemistryNational University of SingaporeSingapore117543Singapore
| | - Beatrice J. Y. Lee
- Department of ChemistryNational University of SingaporeSingapore117543Singapore
| | - Rowan D. Young
- School of Chemistry and Molecular BiosciencesThe University of QueenslandSt Lucia4067Australia
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5
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Luo Z, Li Z, Zhao H, Yang J, Xu L, Lei M, Fan Q, Walsh PJ. Borane-Catalyzed Tandem Cyclization/Hydrosilylation Towards Enantio- and Diastereoselective Construction of trans-2,3-Disubstituted-1,2,3,4-Tetrahydroquinoxalines. Angew Chem Int Ed Engl 2023:e202305449. [PMID: 37338222 DOI: 10.1002/anie.202305449] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 06/18/2023] [Accepted: 06/19/2023] [Indexed: 06/21/2023]
Abstract
Recent years have witnessed marked progress in the efficient synthesis of various enantioenriched 1,2,3,4-tetrahydroquinoxalines. However, enantio- and diastereoselective access to trans-2,3-disubstituted 1,2,3,4-tetrahydroquinoxalines remains much less explored. Herein we report that a frustrated Lewis pair-based catalyst generated via in situ hydroboration of 2-vinylnaphthalene with HB(C6F5)2 allows for the one-pot tandem cyclization/hydrosilylation of 1,2-diaminobenzenes and 1,2-diketones with commercially available PhSiH3 to exclusively afford trans-2,3-disubstituted 1,2,3,4-tetrahydroquinoxalines in high yields with excellent diastereoselectivities (>20:1 dr). Furthermore, this reaction can be rendered asymmetric by using an enantioenriched borane-based catalyst derived from HB(C6F5)2 and a binaphthyl-based chiral diene to give rise to enantioenriched trans-2,3-disubstituted 1,2,3,4-tetrahydroquinoxalines in high yields with almost complete diastereo- and enantiocontrol (>20:1 dr, up to >99% ee). A wide substrate scope, good tolerance of diverse functionality and up to 20-gram scale production are demonstrated. The enantio- and diastereocontrol are achieved by the judicious choice of borane catalyst and hydrosilane. The catalytic pathway and the origin of the excellent stereoselectivity are elucidated by mechanistic experiments and DFT calculations.
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Affiliation(s)
- Zhenli Luo
- Renmin University of China, Chemistry, CHINA
| | - Zhewei Li
- Beijing University of Chemical Technology, chem, CHINA
| | - Haoqiang Zhao
- Renmin University of China School of Social Sciences: Renmin University of China, Chemistry, CHINA
| | - Ji Yang
- Renmin University of China, Chem, CHINA
| | - Lijin Xu
- Renmin University of China, Chemistry, CHINA
| | - Ming Lei
- Beijing University of Chemical Technology, Chemistry, CHINA
| | - Qinghua Fan
- Beijing National Laboratory for Molecular Sciences, Chinese Academy of Sciences, CHINA
| | - Patrick Joseph Walsh
- The University of Pennsylvania, Department of Chemistry, 231 South 34th Street, 19104-6323, Philadelphia, UNITED STATES
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6
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Salusso D, Grillo G, Manzoli M, Signorile M, Zafeiratos S, Barreau M, Damin A, Crocellà V, Cravotto G, Bordiga S. CeO 2 Frustrated Lewis Pairs Improving CO 2 and CH 3OH Conversion to Monomethylcarbonate. ACS Appl Mater Interfaces 2023; 15:15396-15408. [PMID: 36917679 PMCID: PMC10064321 DOI: 10.1021/acsami.2c22122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 02/15/2023] [Indexed: 06/18/2023]
Abstract
Frustrated Lewis pairs (FLPs), discovered in the last few decades for homogeneous catalysts and in the last few years also for heterogeneous catalysts, are stimulating the scientific community's interest for their potential in small-molecule activation. Nevertheless, how an FLP activates stable molecules such as CO2 is still undefined. Through a careful spectroscopic study, we here report the formation of FLPs over a highly defective CeO2 sample prepared by microwave-assisted synthesis. Carbon dioxide activation over FLP is shown to occur through a bidentate carbonate bridging the FLP and implying a Ce3+-to-CO2 charge transfer, thus enhancing its activation. Carbon dioxide reaction with methanol to form monomethylcarbonate is here employed to demonstrate active roles of FLP and, eventually, to propose a reaction mechanism clarifying the role of Ce3+ and oxygen vacancies.
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Affiliation(s)
- Davide Salusso
- Department
of Chemistry, University of Turin, 10125 Turin, Italy
- NIS
Center, University of Turin, 10125 Turin, Italy
- INSTM
Reference Center, University of Turin, 10125 Turin, Italy
- European
Synchrotron Radiation Facility, CS 40220, Cedex 9 38043 Grenoble, France
| | - Giorgio Grillo
- Department
of Drug Science and Technology, University
of Turin, 10125 Turin, Italy
| | - Maela Manzoli
- NIS
Center, University of Turin, 10125 Turin, Italy
- INSTM
Reference Center, University of Turin, 10125 Turin, Italy
- Department
of Drug Science and Technology, University
of Turin, 10125 Turin, Italy
| | - Matteo Signorile
- Department
of Chemistry, University of Turin, 10125 Turin, Italy
- NIS
Center, University of Turin, 10125 Turin, Italy
- INSTM
Reference Center, University of Turin, 10125 Turin, Italy
| | - Spyridon Zafeiratos
- Institut
de Chimie et Procédés pour L’Energie, L’Environnement
et La Santé, UMR
7515 CNRS-UdS, 25 Rue Becquerel, 67087 Strasbourg, France
| | - Mathias Barreau
- Institut
de Chimie et Procédés pour L’Energie, L’Environnement
et La Santé, UMR
7515 CNRS-UdS, 25 Rue Becquerel, 67087 Strasbourg, France
| | - Alessandro Damin
- Department
of Chemistry, University of Turin, 10125 Turin, Italy
- NIS
Center, University of Turin, 10125 Turin, Italy
- INSTM
Reference Center, University of Turin, 10125 Turin, Italy
| | - Valentina Crocellà
- Department
of Chemistry, University of Turin, 10125 Turin, Italy
- NIS
Center, University of Turin, 10125 Turin, Italy
- INSTM
Reference Center, University of Turin, 10125 Turin, Italy
| | - Giancarlo Cravotto
- NIS
Center, University of Turin, 10125 Turin, Italy
- Department
of Drug Science and Technology, University
of Turin, 10125 Turin, Italy
| | - Silvia Bordiga
- Department
of Chemistry, University of Turin, 10125 Turin, Italy
- NIS
Center, University of Turin, 10125 Turin, Italy
- INSTM
Reference Center, University of Turin, 10125 Turin, Italy
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7
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Marques LR, Ando RA. Infrared Spectroscopy Evidence of Weak Interactions in Frustrated Lewis Pairs Formed by Tris(pentafluorophenyl)borane. Chemphyschem 2023; 24:e202200715. [PMID: 36450662 DOI: 10.1002/cphc.202200715] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 10/26/2022] [Accepted: 11/29/2022] [Indexed: 12/04/2022]
Abstract
Frustrated Lewis pairs (FLPs) have been widely investigated as promising catalysts due to their metal-free feature and ability to activate small molecules. Since their discovery, many works have been investigating how these Lewis pairs (intermolecular pairs) are held together in an encounter complex. This prompted several studies based on theoretical investigations, but experimental ones are limited yet. In this communication we show evidence of weak intermolecular interactions between Lewis acids and Lewis bases, distinguishing the Lewis adduct from FLPs, by probing fluorine-carbon vibrational modes using infrared spectroscopy. The main evidence is based on the band shifts occurring in FLPs due to weak hydrogen bonds between the hydrogen atoms of the Lewis base and the fluorine atoms of Lewis acid.
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Affiliation(s)
- Leandro Ramos Marques
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, Butantã, 05508-000, São Paulo-SP, Brazil
| | - Rômulo Augusto Ando
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, Butantã, 05508-000, São Paulo-SP, Brazil
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8
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Mummadi S, Krempner C. Triphenylborane in Metal-Free Catalysis. Molecules 2023; 28. [PMID: 36771006 DOI: 10.3390/molecules28031340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 02/04/2023] Open
Abstract
The development and application of new organoboron reagents as Lewis acids in synthesis and metal-free catalysis have dramatically expanded over the past 20 years. In this context, we will show the recent uses of the simple and relatively weak Lewis acid BPh3-discovered 100 years ago-as a metal-free catalyst for various organic transformations. The first part will highlight catalytic applications in polymer synthesis such as the copolymerization of epoxides with CO2, isocyanate, and organic anhydrides to various polycarbonate copolymers and controlled diblock copolymers as well as alternating polyurethanes. This is followed by a discussion of BPh3 as a Lewis acid component in the frustrated Lewis pair (FLP) mediated cleavage of hydrogen and hydrogenation catalysis. In addition, BPh3-catalyzed reductive N-methylations and C-methylations with CO2 and silane to value-added organic products will be covered as well along with BPh3-catalyzed cycloadditions and insertion reactions. Collectively, this mini-review showcases the underexplored potential of commercially available BPh3 in metal-free catalysis.
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9
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Milinkovic A, Dupé A, Belaj F, Mösch-Zanetti NC. Molybdenum(VI) Bis(imido) Complexes: From Frustrated Lewis Pairs to Weakly Coordinating Cations. Chemistry 2022; 28:e202201867. [PMID: 35775999 DOI: 10.1002/chem.202201867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Indexed: 01/07/2023]
Abstract
Molybdenum(VI) bis(imido) complexes [Mo(NtBu)2 (LR )2 ] (R=H 1 a; R=CF3 1 b) combined with B(C6 F5 )3 (1 a/B(C6 F5 )3 , 1 b/B(C6 F5 )3 ) exhibit a frustrated Lewis pair (FLP) character that can heterolytically split H-H, Si-H and O-H bonds. Cleavage of H2 and Et3 SiH affords ion pairs [Mo(NtBu)(NHtBu)(LR )2 ][HB(C6 F5 )3 ] (R=H 2 a; R=CF3 2 b) composed of a Mo(VI) amido imido cation and a hydridoborate anion, while reaction with H2 O leads to [Mo(NtBu)(NHtBu)(LR )2 ][(HO)B(C6 F5 )3 ] (R=H 3 a; R=CF3 3 b). Ion pairs 2 a and 2 b are catalysts for the hydrosilylation of aldehydes with triethylsilane, with 2 b being more active than 2 a. Mechanistic elucidation revealed insertion of the aldehyde into the B-H bond of [HB(C6 F5 )3 ]- . We were able to isolate and fully characterize, including by single-crystal X-ray diffraction analysis, the inserted products Mo(NtBu)(NHtBu)(LR )2 ][{PhCH2 O}B(C6 F5 )3 ] (R=H 4 a; R=CF3 4 b). Catalysis occurs at [HB(C6 F5 )3 ]- while [Mo(NtBu)(NHtBu)(LR )2 ]+ (R=H or CF3 ) act as the cationic counterions. However, the striking difference in reactivity gives ample evidence that molybdenum cations behave as weakly coordinating cations (WCC).
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Affiliation(s)
- Angela Milinkovic
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Antoine Dupé
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Ferdinand Belaj
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
| | - Nadia C Mösch-Zanetti
- Institute of Chemistry - Inorganic Chemistry, University of Graz, Schubertstraße 1, 8010, Graz
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10
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Zhang ZF, Su MD. The reactivity of the trapping reaction of the benzene-bridged boron/phosphorus-based frustrated Lewis pair with difluorocarbene and its group 14 analogs: A theoretical investigation. J Comput Chem 2022; 43:1783-1792. [PMID: 36063085 DOI: 10.1002/jcc.26980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/22/2022] [Accepted: 07/15/2022] [Indexed: 11/07/2022]
Abstract
The trapping reactions of carbene analogs G14F2 (G14 = group 14 element) by the benzene-bridged B/P-Rea frustrated Lewis pair (FLPs) molecule are studied using density functional theory (B3LYP-D3(BJ)/def2-TZVP). Our theoretical investigations predict that only the CF2 intermediate rather than other heavy carbene analogs can be trapped by the B/P-Rea FLP-type molecule. Energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) analyses indicate that the bonding nature of the G14F2 catching reactions by the B/P-Rea FLP-type molecule is a donor-acceptor (singlet-singlet) interaction rather than an electron-sharing (triplet-triplet) interaction. Moreover, EDA-NOCV and frontier molecular orbital (FMO) theory findings strongly suggest that the lone pair (LP) (P) → vacant p-π-orbital (G14F2 ) interaction rather than the empty σ-orbital (B) ← sp2 -σ-orbital (G14F2 ) interaction plays a predominant role in establishing its bonding condition during the G14F2 trapping reaction with the B/P-Rea FLP-associated molecule. Our activation strain model findings reveal that the atomic radius of the G14 element of G14F2 plays a key role in determining the activation barrier of the G14F2 trapping reactions by the benzene-bridged B/P-Rea FLP. The valence bond state correlation diagram (VBSCD) model developed by Shaik is used to rationalize the calculated results. The VBSCD findings demonstrate that in the present trapping reactions, the singlet triplet splitting of G14F2 plays a significant role in influencing its reaction barrier and reaction enthalpy. Our theoretical results demonstrate that the relationship between the geometrical parameters of the transition states and the corresponding reaction free energy barriers agrees well with the findings based on the Hammond postulate.
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Affiliation(s)
- Zheng-Feng Zhang
- Department of Applied Chemistry, National Chiayi University, Chiayi, Taiwan
| | - Ming-Der Su
- Department of Applied Chemistry, National Chiayi University, Chiayi, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung, Taiwan
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11
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Abstract
Heteroaryl boronic acids and esters are extremely important and valuable intermediates because of their wide application in the synthesis of marketed drugs and bioactive compounds. Over the last couple of decades, the construction of highly important heteroaryl carbon-boron bonds has created huge attention. The transition-metal-free protocols are more green, less sensitive to air and moisture, and also economically advantageous over the transition-metal-based protocols. The transition-metal-free C-H borylation of heteroarenes and C-X (X=halogen) borylation of heteroaryl halides represents an excellent approach for their synthesis. Also, various cyclization and alkyne activation protocols have been recently established for their synthesis. The goal of this review article is to summarize the existing literature and the current state of the art for transition-metal-free synthesis of heteroaryl boronic acid and esters.
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Affiliation(s)
- Subrata Hazra
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Somenath Mahato
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Kanak Kanti Das
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
| | - Santanu Panda
- Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India
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12
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Wang T, Xu M, Jupp AR, Qu ZW, Grimme S, Stephan DW. Selective Catalytic Frustrated Lewis Pair Hydrogenation of CO 2 in the Presence of Silylhalides. Angew Chem Int Ed Engl 2021; 60:25771-25775. [PMID: 34606160 PMCID: PMC9298004 DOI: 10.1002/anie.202112233] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Indexed: 12/15/2022]
Abstract
The frustrated Lewis pair (FLP) derived from 2,6‐lutidine and B(C6F5)3 is shown to mediate the catalytic hydrogenation of CO2 using H2 as the reductant and a silylhalide as an oxophile. The nature of the products can be controlled with the judicious selection of the silylhalide and the solvent. In this fashion, this metal‐free catalysis affords avenues to the selective formation of the disilylacetal (R3SiOCH2OSiR3), methoxysilane (R3SiOCH3), methyliodide (CH3I) and methane (CH4) under mild conditions. DFT studies illuminate the complexities of the mechanism and account for the observed selectivity.
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Affiliation(s)
- Tongtong Wang
- Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario, M5S3H6, Canada.,School of Chemistry, Faculty of Chemical, Environmental and Biological Science and Technology, Dalian University of Technology, China
| | - Maotong Xu
- Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario, M5S3H6, Canada
| | - Andrew R Jupp
- Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario, M5S3H6, Canada
| | - Zheng-Wang Qu
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany
| | - Douglas W Stephan
- Department of Chemistry, University of Toronto, 80 St. George St., Toronto, Ontario, M5S3H6, Canada
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13
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Köring L, Sitte NA, Bursch M, Grimme S, Paradies J. Hydrogenation of Secondary Amides using Phosphane Oxide and Frustrated Lewis Pair Catalysis. Chemistry 2021; 27:14179-14183. [PMID: 33460471 PMCID: PMC8596796 DOI: 10.1002/chem.202100041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Indexed: 01/07/2023]
Abstract
The metal‐free catalytic hydrogenation of secondary carboxylic acid amides is developed. The reduction is realized by two new catalytic reactions. First, the amide is converted into the imidoyl chloride by triphosgene (CO(OCCl3)2) using novel phosphorus(V) catalysts. Second, the in situ generated imidoyl chlorides are hydrogenated in high yields by an FLP‐catalyst. Mechanistic and quantum mechanical calculations support an autoinduced catalytic cycle for the hydrogenation with chloride acting as unusual Lewis base for FLP‐mediated H2‐activation.
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Affiliation(s)
- Laura Köring
- Chemistry Department, Paderborn University, Warburger Strasse 100, D-33098, Paderborn, Germany
| | - Nikolai A Sitte
- Chemistry Department, Paderborn University, Warburger Strasse 100, D-33098, Paderborn, Germany
| | - Markus Bursch
- Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität Bonn, Beringstr. 4, D-53115, Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Institute of Physical and Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität Bonn, Beringstr. 4, D-53115, Bonn, Germany
| | - Jan Paradies
- Chemistry Department, Paderborn University, Warburger Strasse 100, D-33098, Paderborn, Germany
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14
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Chan YC, Bai Y, Chen WC, Chen HY, Li CY, Wu YY, Tseng MC, Yap GPA, Zhao L, Chen HY, Ong TG. Synergistic Catalysis by Brønsted Acid/Carbodicarbene Mimicking Frustrated Lewis Pair-Like Reactivity. Angew Chem Int Ed Engl 2021; 60:19949-19956. [PMID: 34128303 DOI: 10.1002/anie.202107127] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Indexed: 01/06/2023]
Abstract
Carbodicarbene (CDC), unique carbenic entities bearing two lone pairs of electrons are well-known for their strong Lewis basicity. We demonstrate herein, upon introducing a weak Brønsted acid benzyl alcohol (BnOH) as a co-modulator, CDC is remolded into a Frustrated Lewis Pair (FLP)-like reactivity. DFT calculation and experimental evidence show BnOH loosely interacting with the binding pocket of CDC via H-bonding and π-π stacking. Four distinct reactions in nature were deployed to demonstrate the viability of proof-of-concept as synergistic FLP/Modulator (CDC/BnOH), demonstrating enhanced catalytic reactivity in cyclotrimerization of isocyanate, polymerization process for L-lactide (LA), methyl methacrylate (MMA) and dehydrosilylation of alcohols. Importantly, the catalytic reactivity of carbodicarbene is uniquely distinct from conventional NHC which relies on only single chemical feature of nucleophilicity. This finding also provides a new spin in diversifying FLP reactivity with co-modulator or co-catalyst.
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Affiliation(s)
- Yi-Chen Chan
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C.,Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu, Taiwan, R.O.C.,Taiwan International Graduate Program (TIGP), Sustainable Chemical Science and Technology (SCST), Academia Sinica, Taipei, Taiwan, R.O.C
| | - Yuna Bai
- Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing, China
| | - Wen-Ching Chen
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C
| | - Hsing-Yin Chen
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan, R.O.C
| | - Chen-Yu Li
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan, R.O.C
| | - Ying-Yann Wu
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C
| | - Mei-Chun Tseng
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C
| | - Glenn P A Yap
- The Department of Chemistry and Biochemistry, University of Delaware, Newark, DE, USA
| | - Lili Zhao
- Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing, China
| | - Hsuan-Ying Chen
- Department of Medicinal and Applied Chemistry, Drug Development and Value Creation Research Center, Kaohsiung Medical University, Kaohsiung, 80708, Taiwan, R.O.C.,Department of Medicinal Research, Kaohsiung Medical University Hospital, Kaohsiung, 80708, Taiwan, R.O.C
| | - Tiow-Gan Ong
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan, R.O.C.,Department of Chemistry, National (Taiwan) University, Taipei, Taiwan, R.O.C
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15
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Zheng X, Zulkifly I, Heilmann A, McManus C, Aldridge S. Colorimetric Metal-Free Detection of Carbon Monoxide: Reversible CO Uptake by a BNB Frustrated Lewis Pair. Angew Chem Int Ed Engl 2021; 60:16416-16419. [PMID: 34047424 PMCID: PMC8362209 DOI: 10.1002/anie.202106413] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Indexed: 01/03/2023]
Abstract
We report two BNB‐type frustrated Lewis pairs which feature an acceptor‐donor‐acceptor functionalized cavity, and which differ in the nature of the B‐bound fluoroaryl group (C6F5 vs. C6H3(CF3)2‐3,5, Arf). These receptor systems are capable of capturing gaseous CO, and in the case of the ‐BArf2 system this can be shown to occur in reversible fashion at/above room temperature. For both systems, the binding event is accompanied by migration of one of the aryl substituents to the electrophilic carbon of the CO guest. Experiments utilizing an additional equivalent of PtBu3 allow the initially formed (non‐migrated) CO adduct to be identified and trapped (via demethylation), while also establishing the reversibility of the B‐to‐C migration process. When partnered with the slightly less Lewis acidic ‐BArf2 substituent, this reversibility allows for release of the captured carbon monoxide in the temperature range 40–70 °C, and the possibility for CO sensing, making use of the associated colourless to orange/red colour change.
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Affiliation(s)
- Xiongfei Zheng
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Ili Zulkifly
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Andreas Heilmann
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Caitilín McManus
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Simon Aldridge
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
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16
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Manankandayalage C, Unruh DK, Krempner C. Small Molecule Activation with Intramolecular "Inverse" Frustrated Lewis Pairs. Chemistry 2021; 27:6263-6273. [PMID: 33567143 DOI: 10.1002/chem.202005143] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 01/29/2021] [Indexed: 12/25/2022]
Abstract
The intramolecular "inverse" frustrated Lewis pairs (FLPs) of general formula 1-BR2 -2-[(Me2 N)2 C=N]-C6 H4 (3-6) [BR2 =BMes2 (3), BC12 H8 , (4), BBN (5), BBNO (6)] were synthesized and structurally characterized by multinuclear NMR spectroscopy and X-ray analysis. These novel types of pre-organized FLPs, featuring strongly basic guanidino units rigidly linked to weakly Lewis acidic boryl moieties via an ortho-phenylene linker, are capable of activating H-H, C-H, N-H, O-H, Si-H, B-H and C=O bonds. 4 and 5 deprotonated terminal alkynes and acetylene to form the zwitterionic borates 1-(RC≡C-BR2 )-2-[(Me2 N)2 C=NH]-C6 H4 (R=Ph, H) and reacted with ammonia, BnNH2 and pyrrolidine, to generate the FLP adducts 1-(R2 HN→BR2 )-2-[(Me2 N)2 C=NH]-C6 H4 , where the N-H functionality is activated by intramolecular H-bond interactions. In addition, 5 was found to rapidly add across the double bond of H2 CO, PhCHO and PhNCO to form cyclic zwitterionic guanidinium borates in excellent yields. Likewise, 5 is capable of cleaving H2 , HBPin and PhSiH3 to form various amino boranes. Collectively, the results demonstrate that these new types of intramolecular FLPs featuring weakly Lewis acidic boryl and strongly basic guanidino moieties are as potent as conventional intramolecular FLPs with strongly Lewis acidic units in activating small molecules.
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Affiliation(s)
| | - Daniel K Unruh
- Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, Texas, USA
| | - Clemens Krempner
- Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, Texas, USA
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17
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Abstract
The term boron-ligand cooperation was introduced to describe a specific mode of action by which certain metal-free systems activate chemical bonds. The main characteristic of this mode of action is that one covalently bound substituent at the boron is actively involved in the bond activation process and changes to a datively bound ligand in the course of the bond activation. Within this review, how the term boron-ligand cooperation evolved is reflected on and examples of bond activation by boron-ligand cooperation are discussed. It is furthermore shown that systems that operate via boron-ligand cooperation can complement the reactivity of classic intramolecular frustrated Lewis pairs and applications of this new concept for metal-free catalysis are summarized.
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Affiliation(s)
- Max Hasenbeck
- Institut für Organische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring-17, 35392, Gießen, Germany
| | - Urs Gellrich
- Institut für Organische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring-17, 35392, Gießen, Germany
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18
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Marques LR, Ando RA. Probing the Charge Transfer in a Frustrated Lewis Pair by Resonance Raman Spectroscopy and DFT Calculations. Chemphyschem 2021; 22:522-525. [PMID: 33512751 DOI: 10.1002/cphc.202001024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/28/2021] [Indexed: 01/01/2023]
Abstract
A classical Lewis adduct derives from a covalent bond between a Lewis acid and a base. When the adduct formation is precluded by means of steric hindrance the association of the respective acid-base molecular system is defined as a frustrated Lewis pair (FLP). In this work, the archetypal FLP Mes3 P/B(C6 F5 )3 was characterized for the first time by resonance Raman spectroscopy, and the results were supported by density functional theory (DFT) calculations. The charge transfer nature of the lowest energy electronic transition, from phosphine to borane, was confirmed by the selective enhancement of the Raman bands associated to the FLP chromophore at resonance condition. Herein, we demonstrate the use of resonance Raman spectroscopy as a distinguished technique to probe the weak interaction involved in FLP chemistry.
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Affiliation(s)
- Leandro Ramos Marques
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, Butantã, 05508-000, São Paulo-SP, Brazil
| | - Rômulo Augusto Ando
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, Butantã, 05508-000, São Paulo-SP, Brazil
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19
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Abstract
Progress in frustrated Lewis pair (FLP) chemistry has revealed the importance of the main group elements in catalysis, opening new avenues in synthetic chemistry. Recently, new reactivities of frustrated Lewis pairs have been uncovered that disclose that certain combinations of Lewis acids and bases undergo single-electron transfer (SET) processes. Here an electron can be transferred from the Lewis basic donor to a Lewis acidic acceptor to generate a reactive frustrated radical pair (FRP). This minireview aims to showcase the recent advancements in this emerging field covering the synthesis and reactivities of frustrated radical pairs, with extensive highlights of the results from Electron Paramagnetic Resonance (EPR) spectroscopy to explain the nature and stability of the different radical species observed.
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Affiliation(s)
- Ayan Dasgupta
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
| | - Emma Richards
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
| | - Rebecca L. Melen
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
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20
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Holtkamp P, Schwabedissen J, Neumann B, Stammler HG, Koptyug IV, Zhivonitko VV, Mitzel NW. A Zwitterionic Phosphonium Stannate(II) via Hydrogen Splitting by a Sn/P Frustrated Lewis-Pair and Reductive Elimination. Chemistry 2020; 26:17381-17385. [PMID: 33016507 PMCID: PMC7839681 DOI: 10.1002/chem.202004425] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Indexed: 11/22/2022]
Abstract
The reactivity of the frustrated Lewis pair (FLP) (F5C2)3SnCH2P(tBu)2 (1) was investigated with respect to the activation of elemental hydrogen. The reaction of 1 at elevated hydrogen pressure afforded the intramolecular phosphonium stannate(II) (F5C2)2SnCH2PH(tBu)2 (3). It was characterized by means of multinuclear NMR spectroscopy and single crystal X‐ray diffraction. NMR experiments with the two isotopologues H2 and D2 showed it to be formed via an H2 adduct (F5C2)3HSnCH2PH(tBu)2 (2) and the subsequent formal reductive elimination of pentafluoroethane; this is supported by DFT calculations. Parahydrogen‐induced polarization experiments revealed the formation of a second product of the reaction of 1 with H2, [HP(tBu)2Me][Sn(C2F5)3] (4), in 1H NMR spectra, whereas 2 was not detected due to its transient nature.
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Affiliation(s)
- Philipp Holtkamp
- Lehrstuhl für Anorganische Chemie und Strukturchemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Jan Schwabedissen
- Lehrstuhl für Anorganische Chemie und Strukturchemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Beate Neumann
- Lehrstuhl für Anorganische Chemie und Strukturchemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Hans-Georg Stammler
- Lehrstuhl für Anorganische Chemie und Strukturchemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Igor V Koptyug
- International Tomography Center, SB RAS, Institutskaya St. 3A, Novosibirsk, 630090, Russia
| | | | - Norbert W Mitzel
- Lehrstuhl für Anorganische Chemie und Strukturchemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
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21
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Zhang L, Oishi T, Gao L, Hu S, Yang L, Li W, Wu S, Shang R, Yamamoto Y, Li S, Wang W, Zeng G. Catalytic Dehydrogenation of Ammonia Borane Mediated by a Pt(0)/Borane Frustrated Lewis Pair: Theoretical Design. Chemphyschem 2020; 21:2573-2578. [PMID: 33015881 DOI: 10.1002/cphc.202000661] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/27/2020] [Indexed: 11/09/2022]
Abstract
A new efficient metal-based frustrated Lewis pair constructed by (Pt Bu3 )2 Pt and B(C6 F5 )3 was designed through density functional theory calculations for the catalytic dehydrogenation of ammonia borane (AB). The reaction was composed by the successive dehydrogenation of AB and H2 liberation, which occurs through the cooperative functions of the Pt(0) center and the B(C6 F5 )3 moiety. Two equivalents of H2 were predicted to be liberated from each AB molecule. The generation of the second H2 is the rate-determining step, with a Gibbs energy barrier and reaction energy of 27.4 and 12.8 kcal/mol, respectively.
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Affiliation(s)
- Lei Zhang
- Kuang Yaming Honors School and Institute for Brain Sciences, Nanjing University, Nanjing, 210023, China
| | - Takumi Oishi
- Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 7398526, Japan
| | - Liuzhou Gao
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Shiyu Hu
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Linlin Yang
- Kuang Yaming Honors School and Institute for Brain Sciences, Nanjing University, Nanjing, 210023, China
| | - Wei Li
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Shengjun Wu
- Kuang Yaming Honors School and Institute for Brain Sciences, Nanjing University, Nanjing, 210023, China
| | - Rong Shang
- Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 7398526, Japan
| | - Yohsuke Yamamoto
- Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 7398526, Japan
| | - Shuhua Li
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Wei Wang
- Kuang Yaming Honors School and Institute for Brain Sciences, Institute of Biophysics, School of Physics, Nanjing University, Nanjing, 210023, China
| | - Guxiang Zeng
- Kuang Yaming Honors School and Institute for Brain Sciences, Nanjing University, Nanjing, 210023, China
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22
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Wech F, Hasenbeck M, Gellrich U. Semihydrogenation of Alkynes Catalyzed by a Pyridone Borane Complex: Frustrated Lewis Pair Reactivity and Boron-Ligand Cooperation in Concert. Chemistry 2020; 26:13445-13450. [PMID: 32242988 PMCID: PMC7693047 DOI: 10.1002/chem.202001276] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 04/01/2020] [Indexed: 11/11/2022]
Abstract
The metal‐free cis selective hydrogenation of alkynes catalyzed by a boroxypyridine is reported. A variety of internal alkynes are hydrogenated at 80 °C under 5 bar H2 with good yields and stereoselectivity. Furthermore, the catalyst described herein enables the first metal‐free semihydrogenation of terminal alkynes. Mechanistic investigations, substantiated by DFT computations, reveal that the mode of action by which the boroxypyridine activates H2 is reminiscent of the reactivity of an intramolecular frustrated Lewis pair. However, it is the change in the coordination mode of the boroxypyridine upon H2 activation that allows the dissociation of the formed pyridone borane complex and subsequent hydroboration of an alkyne. This change in the coordination mode upon bond activation is described by the term boron‐ligand cooperation.
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Affiliation(s)
- Felix Wech
- Institut für Organische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 17, 35392, Gießen, Germany
| | - Max Hasenbeck
- Institut für Organische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 17, 35392, Gießen, Germany
| | - Urs Gellrich
- Institut für Organische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 17, 35392, Gießen, Germany
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23
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Lange H, Schröder H, Oberem E, Villinger A, Rabeah J, Ludwig R, Neymeyr K, Seidel WW. Facile Synthesis of a Stable Side-on Phosphinyne Complex by Redox Driven Intramolecular Cyclisation. Chemistry 2020; 26:11492-11502. [PMID: 32181544 PMCID: PMC7540294 DOI: 10.1002/chem.201905750] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 03/08/2020] [Indexed: 11/23/2022]
Abstract
Alkyne complexes with vicinal substitution by a Lewis acid and a Lewis base at the coordinated alkyne are prospective frustrated Lewis pairs exhibiting a particular mutual distance and, hence, a specific activation potential. In this contribution, investigations on the generation of a WII alkyne complex bearing a phosphine as Lewis base and a carbenium group as Lewis acid are presented. Independently on potential substrates added, an intramolecular cyclisation product was always isolated. A subsequent deprotonation step led to an unprecedented side-on λ5 -phosphinyne complex, which is interpreted as highly zwitterionic according to visible absorption spectroscopy supported by TD-DFT. Low-temperature 31 P NMR and EPR spectroscopic measurements combined with time-dependent IR-spectroscopic monitoring provided insights in the mechanism of the cyclisation reaction. Decomposition of the multicomponent IR spectra by multivariate curve resolution and a kinetic hard-modelling approach allowed the derivation of kinetic parameters. Assignment of the individual IR spectra to potential intermediates was provided by DFT calculations.
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Affiliation(s)
- Helge Lange
- Institut für ChemieUniversität RostockAlbert-Einstein-Str. 3a18059RostockGermany
| | - Henning Schröder
- Institut für MathematikUniversität RostockUlmenstraße 6918057RostockGermany
| | - Elisabeth Oberem
- Institut für ChemieUniversität RostockAlbert-Einstein-Str. 3a18059RostockGermany
| | - Alexander Villinger
- Institut für ChemieUniversität RostockAlbert-Einstein-Str. 3a18059RostockGermany
| | - Jabor Rabeah
- Leibniz-Institut für Katalyse e.V.Albert-Einstein-Straße 29a18059RostockGermany
| | - Ralf Ludwig
- Institut für ChemieUniversität RostockAlbert-Einstein-Str. 3a18059RostockGermany
- Leibniz-Institut für Katalyse e.V.Albert-Einstein-Straße 29a18059RostockGermany
| | - Klaus Neymeyr
- Institut für MathematikUniversität RostockUlmenstraße 6918057RostockGermany
- Leibniz-Institut für Katalyse e.V.Albert-Einstein-Straße 29a18059RostockGermany
| | - Wolfram W. Seidel
- Institut für ChemieUniversität RostockAlbert-Einstein-Str. 3a18059RostockGermany
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24
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Leitl J, Jupp AR, Habraken ERM, Streitferdt V, Coburger P, Scott DJ, Gschwind RM, Müller C, Slootweg JC, Wolf R. A Phosphinine-Derived 1-Phospha-7-Bora-Norbornadiene: Frustrated Lewis Pair Type Activation of Triple Bonds. Chemistry 2020; 26:7788-7800. [PMID: 32052879 PMCID: PMC7383905 DOI: 10.1002/chem.202000266] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 02/12/2020] [Indexed: 02/06/2023]
Abstract
Salt metathesis of 1-methyl-2,4,6-triphenylphosphacyclohexadienyl lithium and chlorobis(pentafluorophenyl)borane affords a 1-phospha-7-bora-norbornadiene derivative 2. The C≡N triple bonds of nitriles insert into the P-B bond of 2 with concomitant C-B bond cleavage, whereas the C≡C bonds of phenylacetylenes react with 2 to form λ4 -phosphabarrelenes. Even though 2 must formally be regarded as a classical Lewis adduct, the C≡N and C≡C activation processes observed (and the mild conditions under which they occur) are reminiscent of the reactivity of frustrated Lewis pairs. Indeed, NMR and computational studies give insight into the mechanism of the reactions and reveal the labile nature of the phosphorus-boron bond in 2, which is also suggested by detailed NMR spectroscopic studies on this compound. Nitrile insertion is thus preceded by ring opening of the bicycle of 2 through P-B bond splitting with a low energy barrier. By contrast, the reaction with alkynes involves formation of a reactive zwitterionic methylphosphininium borate intermediate, which readily undergoes alkyne 1,4-addition.
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Affiliation(s)
- Julia Leitl
- Institute of Inorganic ChemistryUniversity of Regensburg93040RegensburgGermany
| | - Andrew R. Jupp
- van ‘t Hoff Institute for Molecular SciencesUniversity of AmsterdamScience Park 904, PO Box 941571090 GDAmsterdamThe Netherlands
| | - Evi R. M. Habraken
- van ‘t Hoff Institute for Molecular SciencesUniversity of AmsterdamScience Park 904, PO Box 941571090 GDAmsterdamThe Netherlands
| | - Verena Streitferdt
- Institute of Organic ChemistryUniversity of Regensburg93040RegensburgGermany
| | - Peter Coburger
- Institute of Inorganic ChemistryUniversity of Regensburg93040RegensburgGermany
| | - Daniel J. Scott
- Institute of Inorganic ChemistryUniversity of Regensburg93040RegensburgGermany
| | - Ruth M. Gschwind
- Institute of Organic ChemistryUniversity of Regensburg93040RegensburgGermany
| | - Christian Müller
- Institute of Chemistry and BiochemistryFreie Universität BerlinFabeckstr. 34/3614195BerlinGermany
| | - J. Chris Slootweg
- van ‘t Hoff Institute for Molecular SciencesUniversity of AmsterdamScience Park 904, PO Box 941571090 GDAmsterdamThe Netherlands
| | - Robert Wolf
- Institute of Inorganic ChemistryUniversity of Regensburg93040RegensburgGermany
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25
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Gao B, Feng X, Meng W, Du H. Asymmetric Hydrogenation of Ketones and Enones with Chiral Lewis Base Derived Frustrated Lewis Pairs. Angew Chem Int Ed Engl 2020; 59:4498-4504. [PMID: 31863715 DOI: 10.1002/anie.201914568] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Indexed: 01/13/2023]
Abstract
The concept of frustrated Lewis pairs (FLPs) has been widely applied in various research areas, and metal-free hydrogenation undoubtedly belongs to the most significant and successful ones. In the past decade, great efforts have been devoted to the synthesis of chiral boron Lewis acids. In a sharp contrast, chiral Lewis base derived FLPs have rarely been disclosed for the asymmetric hydrogenation. In this work, a novel type of chiral FLP was developed by simple combination of chiral oxazoline Lewis bases with achiral boron Lewis acids, thus providing a promising new direction for the development of chiral FLPs in the future. These chiral FLPs proved to be highly effective for the asymmetric hydrogenation of ketones, enones, and chromones, giving the corresponding products in high yields with up to 95 % ee. Mechanistic studies suggest that the hydrogen transfer to simple ketones likely proceeds in a concerted manner.
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Affiliation(s)
- Bochao Gao
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiangqing Feng
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wei Meng
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Haifeng Du
- Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.,School of Chemical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China
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Zhang D, Li Q, Zhang J, Wang J, Zhang X, Wang R, Zhou J, Wei Z, Zhang C, Zhou H, Zhang Y. Control of Nanomorphology in Fullerene-Free Organic Solar Cells by Lewis Acid Doping with Enhanced Photovoltaic Efficiency. ACS Appl Mater Interfaces 2020; 12:667-677. [PMID: 31838840 DOI: 10.1021/acsami.9b17238] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Generating desired efficiency enhancements in organic solar cells (OSCs) by charge-transfer doping requires to obtain modified optoelectronic properties while retaining the favorable nanomorphology. We report a thermally assisted doping based on Lewis acid tris(pentafluorophenyl)-borane (BCF) as a p-dopant for two groups of OSCs comprising the PBDB-TF and PBDB-T donors and a nonfullerene acceptor IT-4F. We found that the face-on molecular packing in the PBDB-TF:IT-4F blend or neat PBDB-TF donor films is favorably modified with the formation of frustrated Lewis pairs (FLPs) in the donor, which is in contrast to the hampered π-π stacking in the doped PBDB-T film. The different impacts of BCF dopants on the morphology lead to contrasting photovoltaic behaviors where the PBDB-TF-based devices receive enhanced power conversion efficiencies (PCEs) in the presence of BCF, while reduction of efficiencies is observed in the PBDB-T device. In the best doping conditions with the proposed hot-film deposition, we achieve a boosted PCE of 14.1% in PBDB-TF:IT-4F solar cells at low BCF concentrations. Based on the same fluorinated donor, the described BCF doping also applies to NF-solar cells based on the NF-acceptor Y6, leading to an increase in the PCE to 16.0%. Our results suggest that controlling the degree of FLP formation in the donor component with the addition of BCF is key to obtaining desired improvements on nanomorphology and relevant photophysical properties in OSCs.
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Affiliation(s)
- Dongyang Zhang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering , Beihang University , Beijing 100191 , P. R. China
| | - Qian Li
- School of Physics , Nanjing University , Nanjing , Jiangsu Province 210093 , P. R. China
| | - Jianqi Zhang
- CAS Key Laboratory of Nanosystem and Hierachical Fabrication CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology , Beijing 100190 , P. R. China
| | - Jianqiu Wang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering , Beihang University , Beijing 100191 , P. R. China
- CAS Key Laboratory of Nanosystem and Hierachical Fabrication CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology , Beijing 100190 , P. R. China
| | - Xuning Zhang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering , Beihang University , Beijing 100191 , P. R. China
| | - Rong Wang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering , Beihang University , Beijing 100191 , P. R. China
| | - Jiyu Zhou
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering , Beihang University , Beijing 100191 , P. R. China
| | - Zhixiang Wei
- CAS Key Laboratory of Nanosystem and Hierachical Fabrication CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology , Beijing 100190 , P. R. China
| | - Chunfeng Zhang
- School of Physics , Nanjing University , Nanjing , Jiangsu Province 210093 , P. R. China
| | - Huiqiong Zhou
- CAS Key Laboratory of Nanosystem and Hierachical Fabrication CAS Center for Excellence in Nanoscience , National Center for Nanoscience and Technology , Beijing 100190 , P. R. China
| | - Yuan Zhang
- School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering , Beihang University , Beijing 100191 , P. R. China
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Wang XJ, Hong M. Lewis-Pair-Mediated Selective Dimerization and Polymerization of Lignocellulose-Based β-Angelica Lactone into Biofuel and Acrylic Bioplastic. Angew Chem Int Ed Engl 2020; 59:2664-2668. [PMID: 31762147 DOI: 10.1002/anie.201913136] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 11/16/2019] [Indexed: 12/13/2022]
Abstract
This contribution reports an unprecedentedly efficient dimerization and the first successful polymerization of lignocellulose-based β-angelica lactone (β-AL) by utilizing a selective Lewis pair (LP) catalytic system, thereby establishing a versatile bio-refinery platform wherein two products, including a dimer for high-quality gasoline-like biofuel (C8 -C9 branched alkanes, yield=87 %) and a heat- and solvent-resistant acrylic bioplastic (Mn up to 26.0 kg mol-1 ), can be synthesized from one feedstock by one catalytic system. The underlying reason for exquisite selectivity of the LP catalytic system toward dimerization and polymerization was explored mechanistically.
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Affiliation(s)
- Xiao-Jun Wang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, P. R. China
| | - Miao Hong
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, P. R. China
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Zhu H, Qu ZW, Grimme S. Reduction of Phosphine Oxide by Using Chlorination Reagents and Dihydrogen: DFT Mechanistic Insights. Chemistry 2019; 25:4670-4672. [PMID: 30758069 DOI: 10.1002/chem.201900379] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Indexed: 11/08/2022]
Abstract
Extensive DFT calculations provide detailed mechanistic insights into the metal-free reduction of phosphine oxide Ph3 P=O by using chlorination reagents O=CClX (X=COCl, Cl, OCCl3 and Ph) and H2 . Fast electrophilic attack to the P=O group oxygen atom is favored by exergonic CO2 release to form phosphonium Ph3 PCl+ and chloride Cl- , which may slowly cleave H2 by an unstable HPh3 PCl complex yielding Ph3 PH+ and Cl- ions in solution. Moderate heating is required to accelerate the slow H2 -activation step and to eliminate HCl to form phosphine Ph3 P instead of Ph3 PH+ Cl- salt as the desired product. Though partially quenched by Ph3 P (and reactant Ph3 P=O if present), borane B(2,6-F2 C6 H3 )3 can be still combined with Cl- and Ph3 P as reactive frustrated Lewis pair (FLP) catalysts.
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Affiliation(s)
- Hui Zhu
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany
| | - Zheng-Wang Qu
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany
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Malär AA, Dong S, Kehr G, Erker G, Meier BH, Wiegand T. Characterization of H 2 -Splitting Products of Frustrated Lewis Pairs: Benefit of Fast Magic-Angle Spinning. Chemphyschem 2019; 20:672-679. [PMID: 30663843 DOI: 10.1002/cphc.201900006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 01/19/2019] [Indexed: 11/09/2022]
Abstract
Proton spectroscopy in solid-state NMR on catalytic materials offers new opportunities in structural characterization, in particular of reaction products of catalytic reactions such as hydrogenation reactions. Unfortunately, the 1 H NMR line widths in magic-angle spinning solid-state spectra are often broadened by an incomplete averaging of 1 H-1 H dipolar couplings. We herein discuss two model compounds, namely the H2 -splitting products of two phosphane-borane Frustrated Lewis Pairs (FLPs), to study potentials and limitations of proton solid-state NMR experiments employing magic-angle spinning frequencies larger than 100 kHz at a static magnetic field strength of 20.0 T. The 1 H lines are homogeneously broadened as illustrated by spin-echo decay experiments. We study two structurally similar materials which however show significant differences in 1 H line widths which we explain by differences in their 1 H-1 H dipolar networks. We discuss the benefit of fast MAS experiments up to 110 kHz to detect the resonances of the H+ /H- pair in the hydrogenation products of FLPs.
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Affiliation(s)
- Alexander A Malär
- Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - Shunxi Dong
- Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, 48149, Münster, Germany
| | - Gerald Kehr
- Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, 48149, Münster, Germany
| | - Gerhard Erker
- Organisch-Chemisches Institut, WWU Münster, Corrensstraße 40, 48149, Münster, Germany
| | - Beat H Meier
- Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
| | - Thomas Wiegand
- Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093, Zurich, Switzerland
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30
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Benton A, Copeland Z, Mansell SM, Rosair GM, Welch AJ. Exploiting the Electronic Tuneability of Carboranes as Supports for Frustrated Lewis Pairs. Molecules 2018; 23:E3099. [PMID: 30486434 DOI: 10.3390/molecules23123099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 11/22/2018] [Accepted: 11/23/2018] [Indexed: 11/16/2022] Open
Abstract
The first example of a carborane with a catecholborolyl substituent, [1-Bcat-2-Ph-closo-1,2-C₂B10H10] (1), has been prepared and characterized and shown to act as the Lewis acid component of an intermolecular frustrated Lewis pair in catalyzing a Michael addition. In combination with B(C₆F₅)₃ the C-carboranylphosphine [1-PPh₂-closo-1,2-C₂B10H11] (IVa) is found to be comparable with PPh₂(C₆F₅) in its ability to catalyze hydrosilylation, whilst the more strongly basic B-carboranylphosphine [9-PPh₂-closo-1,7-C₂B10H11] (V) is less effective and the very weakly basic species [μ-2,2'-PPh-{1-(1'-1',2'-closo-C₂B10H10)-1,2-closo-C₂B10H10}] (IX) is completely ineffective. Base strengths are rank-ordered via measurement of the ¹J 31P-77Se coupling constants of the phosphineselenides [1-SePPh₂-closo-1,2-C₂B10H11] (2), [9-SePPh₂-closo-1,7-C₂B10H11] (3), and [SePPh₂(C₆F₅)] (4).
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31
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Wang X, Zhang Y, Hong M. Controlled and Efficient Polymerization of Conjugated Polar Alkenes by Lewis Pairs Based on Sterically Hindered Aryloxide-Substituted Alkylaluminumitle. Molecules 2018; 23:E442. [PMID: 29462959 PMCID: PMC6017945 DOI: 10.3390/molecules23020442] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 02/12/2018] [Accepted: 02/14/2018] [Indexed: 01/08/2023] Open
Abstract
Reported herein is the development of an effective strategy for controlled and efficient Lewis pair polymerization of conjugated polar alkenes, including methyl methacrylate (MMA), n-butyl methacrylate (nBuMA), and γ-methyl-α-methylene-γ-butyrolactone (γMMBL), by the utilization of sterically encumbered Al(BHT)₂Me (BHT: 2,6-di-tert-butyl-4-methylphenol) as a Lewis acid that shuts down intramolecular backbiting termination. In combination with a selected N-heterocyclic carbene (NHC) as a Lewis base, the polymerization of MMA exhibited activity up to 3000 h-1 TOF and an acceptable initiation efficiency of 60.6%, producing polymers with high molecular weight (Mn up to 130 kg/mol) and extremely narrow dispersity (Đ = 1.06~1.13). This controlled polymerization with a living characteristic has been evidenced by chain-extension experiments and chain-end analysis, and enabled the synthesis of well-defined diblock copolymers.
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Affiliation(s)
- Xiaojun Wang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
| | - Yixin Zhang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
| | - Miao Hong
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
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Abstract
An unconventional cis-cis-cis-trans or (Z,Z,Z,E) structure B of cyclooctatetraene (COT) is calculated to lie only 23 kcal/mol above the well-known tub-shaped (Z,Z,Z,Z) isomer A; one example of this type of structure is known. The barrier for B returning to A is small, 3 kcal/mol. However, by suitable choice of substituents, the (Z,Z,Z,E) isomer can be made to lie in energy below the tub-shaped structure. Steric, clamping, and electronic strategies are proposed for achieving this. In the steric strategy, the C8H4(CH3)2(C( t Bu)3)2 structure B is predicted to lie 21 kcal/mol below structure A, which is separated from form B only by a small barrier. A simple clamping strategy, effective for COT planarization, does not influence the A/B isomerization much. But, if the clamping group is aromatic (a fused benzene, pyrrole, thiophene, furan), the subtle interplay of potential aromaticity with clamping can be used to confer persistence if not stability on the (Z,Z,Z,E) isomer. An electronic strategy of a different kind, push-pull substitution on the COT ring, was not very effective in stabilizing the B form. However, it led us to vicinal amine-borane-substituted normal COTs that proved to be quite good at activating H2 in a frustrated Lewis pair scenario.
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33
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Wilkins LC, Santi N, Luk LYP, Melen RL. Reactions of biologically inspired hydride sources with B(C 6F 5) 3. Philos Trans A Math Phys Eng Sci 2017; 375:20170009. [PMID: 28739967 PMCID: PMC5540842 DOI: 10.1098/rsta.2017.0009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 03/25/2017] [Indexed: 06/07/2023]
Abstract
The combination of 1-benzyl-1,4-dihydropyridines with the strong Lewis acid, B(C6F5)3, generates a stable pyridinium borohydride species in high yields (94%) in as little as 10 min. This use of biologically inspired hydride sources further builds on the recent work of new hydride donors in the formation of borohydrides. When functionalizing the dihydropyridine with an amide or carboxylic acid moiety, a disproportionation reaction composed of a series of protonation/reduction steps is observed upon the addition of B(C6F5)3 As a result, one equivalent of dihydropyridine undergoes net hydrogenation, whereas the other is dehydrogenated yielding the pyridinium counterpart in a transfer hydrogenation-type mechanism.This article is part of the themed issue 'Frustrated Lewis pair chemistry'.
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Affiliation(s)
- Lewis C Wilkins
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
| | - Nicolò Santi
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
| | - Louis Y P Luk
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
| | - Rebecca L Melen
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
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34
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Möricke J, Wibbeling B, Daniliuc CG, Kehr G, Erker G. Design and reactions of a carbon Lewis base/boron Lewis acid frustrated Lewis pair. Philos Trans A Math Phys Eng Sci 2017; 375:rsta.2017.0015. [PMID: 28739970 PMCID: PMC5540844 DOI: 10.1098/rsta.2017.0015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/09/2017] [Indexed: 06/07/2023]
Abstract
The conjugated dienamine 4 selectively adds Piers' borane [HB(C6F5)2] to give the enamine/borane system 5, which features a boratirane structure by internal enamine carbon Lewis base to boron Lewis acid interaction. Compound 5 behaves as a C/B frustrated Lewis pair and undergoes typical addition reactions to benzaldehyde, several nitriles and to sulfur dioxide.This article is part of the themed issue 'Frustrated Lewis pair chemistry'.
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Affiliation(s)
- Jennifer Möricke
- Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Birgit Wibbeling
- Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Constantin G Daniliuc
- Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Gerald Kehr
- Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Gerhard Erker
- Organisch-Chemisches Institut, Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
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35
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Carr SB, Evans RM, Brooke EJ, Wehlin SA, Nomerotskaia E, Sargent F, Armstrong FA, Phillips SE. Hydrogen activation by [NiFe]-hydrogenases. Biochem Soc Trans 2016; 44:863-8. [PMID: 27284053 DOI: 10.1042/BST20160031] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Indexed: 11/17/2022]
Abstract
Hydrogenase-1 (Hyd-1) from Escherichia coli is a membrane-bound enzyme that catalyses the reversible oxidation of molecular H2 The active site contains one Fe and one Ni atom and several conserved amino acids including an arginine (Arg(509)), which interacts with two conserved aspartate residues (Asp(118) and Asp(574)) forming an outer shell canopy over the metals. There is also a highly conserved glutamate (Glu(28)) positioned on the opposite side of the active site to the canopy. The mechanism of hydrogen activation has been dissected by site-directed mutagenesis to identify the catalytic base responsible for splitting molecular hydrogen and possible proton transfer pathways to/from the active site. Previous reported attempts to mutate residues in the canopy were unsuccessful, leading to an assumption of a purely structural role. Recent discoveries, however, suggest a catalytic requirement, for example replacing the arginine with lysine (R509K) leaves the structure virtually unchanged, but catalytic activity falls by more than 100-fold. Variants containing amino acid substitutions at either or both, aspartates retain significant activity. We now propose a new mechanism: heterolytic H2 cleavage is via a mechanism akin to that of a frustrated Lewis pair (FLP), where H2 is polarized by simultaneous binding to the metal(s) (the acid) and a nitrogen from Arg(509) (the base).
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36
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Wang L, Samigullin K, Wagner M, McQuilken AC, Warren TH, Daniliuc CG, Kehr G, Erker G. An Ethylene-Bridged Phosphane/Borane Frustrated Lewis Pair Featuring the -B(Fxyl)2 Lewis Acid Component. Chemistry 2016; 22:11015-21. [PMID: 27355412 DOI: 10.1002/chem.201601583] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Indexed: 11/07/2022]
Abstract
Hydroboration of dimesitylvinylphosphane with bis[3,5-bis(trifluoromethyl)phenyl]borane [HB(Fxyl)2 ] gave the intramolecular ethylene-bridged P/B frustrated Lewis pair (FLP) Mes2 PCH2 CH2 B(Fxyl)2 . The new compound underwent a variety of typical FLP reactions such as P/B-addition to the carbonyl group of p-chloro-benzaldehyde. Cooperative N,N-addition to nitric oxide gave the respective persistent P/B FLPNO(.) radical, which readily reacted with 1,4-cyclohexadiene by H-atom abstraction to yield the corresponding P/B FLPNOH product. The B(Fxyl)2 -containing FLP reacted as a template for the HB(C6 F5 )2 reduction of carbon monoxide to the formyl stage to give the respective FLP(η(2) -formylborane) product. Most products were characterized by single-crystal X-ray crystal structure analysis.
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Affiliation(s)
- Long Wang
- Organisch-Chemisches Institut, Universität Münster, Corrensstraße 40, 48149, Münster, Germany
| | - Kamil Samigullin
- Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt, Max-von-Laue-Straße 7, 60438, Frankfurt (Main), Germany
| | - Matthias Wagner
- Institut für Anorganische und Analytische Chemie, Goethe-Universität Frankfurt, Max-von-Laue-Straße 7, 60438, Frankfurt (Main), Germany
| | - Alison C McQuilken
- Department of Chemistry, Georgetown University, Box 571557, Washington DC, 20057-1227, USA
| | - Timothy H Warren
- Department of Chemistry, Georgetown University, Box 571557, Washington DC, 20057-1227, USA
| | - Constantin G Daniliuc
- Organisch-Chemisches Institut, Universität Münster, Corrensstraße 40, 48149, Münster, Germany
| | - Gerald Kehr
- Organisch-Chemisches Institut, Universität Münster, Corrensstraße 40, 48149, Münster, Germany
| | - Gerhard Erker
- Organisch-Chemisches Institut, Universität Münster, Corrensstraße 40, 48149, Münster, Germany.
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37
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Özgün T, Ye KY, Daniliuc CG, Wibbeling B, Liu L, Grimme S, Kehr G, Erker G. Why Does the Intramolecular Trimethylene-Bridged Frustrated Lewis Pair Mes2 PCH2 CH2 CH2 B(C6 F5 )2 Not Activate Dihydrogen? Chemistry 2016; 22:5988-95. [PMID: 26999779 DOI: 10.1002/chem.201505200] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Indexed: 11/12/2022]
Abstract
The methyl labelled C3 -bridged frustrated phosphane borane Lewis pair (P/B FLP) 2 b was prepared by treatment of Mes2 PCl with a methallyl Grignard reagent followed by anti-Markovnikov hydroboration with Piers' borane [HB(C6 F5 )2 )]. The FLP 2 b is inactive toward dihydrogen under typical ambient conditions, in contrast to the C2 - and C4 -bridged FLP analogues. Dynamic NMR spectroscopy showed that this was not due to kinetically hindered P⋅⋅⋅B dissociation of 2 b. DFT calculations showed that the hydrogen-splitting reaction of the parent compound 2 a is markedly endergonic. The PH(+) /BH(-) H2 -splitting product of 2 b was indirectly synthesized by a sequence of H(+) /H(-) addition. It lost H2 at ambient conditions and confirmed the result of the DFT analysis.
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Affiliation(s)
- Thomas Özgün
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany
| | - Ke-Yin Ye
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany
| | - Constantin G Daniliuc
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany
| | - Birgit Wibbeling
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany
| | - Lei Liu
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
| | - Gerald Kehr
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany
| | - Gerhard Erker
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany.
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38
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Tamang SR, Hoefelmeyer JD. Chloro({2-[mesityl(quinolin-8-yl-κN)boryl]-3,5-dimethyl-phenyl}methyl-κC)palladium(II) as a catalyst for Heck reactions. Molecules 2015; 20:12979-91. [PMID: 26193250 DOI: 10.3390/molecules200712979] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Revised: 07/09/2015] [Accepted: 07/15/2015] [Indexed: 11/17/2022] Open
Abstract
We recently reported an air and moisture stable 16-electron borapalladacycle formed upon combination of 8-quinolyldimesitylborane with bis(benzonitrile)dichloropalladium(II). The complex features a tucked mesityl group formed upon metalation of an ortho-methyl group on a mesityl; however it is unusually stable due to contribution of the boron pz orbital in delocalizing the carbanion that gives rise to an η4-boratabutadiene fragment coordinated to Pd(II), as evidenced from crystallographic data. This complex was observed to be a highly active catalyst for the Heck reaction. Data of the catalyst activity are presented alongside data found in the literature, and initial comparison reveals that the borapalladacycle is quite active. The observed catalysis suggests the borapalladacycle readily undergoes reductive elimination; however the Pd(0) complex has not yet been isolated. Nevertheless, the ambiphilic ligand 8-quinolyldimesitylborane may be able to support palladium in different redox states.
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Fu MC, Shang R, Cheng WM, Fu Y. Boron-Catalyzed N-Alkylation of Amines using Carboxylic Acids. Angew Chem Int Ed Engl 2015; 54:9042-6. [PMID: 26150397 DOI: 10.1002/anie.201503879] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 05/26/2015] [Indexed: 11/07/2022]
Abstract
A boron-based catalyst was found to catalyze the straightforward alkylation of amines with readily available carboxylic acids in the presence of silane as the reducing agent. Various types of primary and secondary amines can be smoothly alkylated with good selectivity and good functional-group compatibility. This metal-free amine alkylation was successfully applied to the synthesis of three commercial medicinal compounds, Butenafine, Cinacalcet. and Piribedil, in a one-pot manner without using any metal catalysts.
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Affiliation(s)
- Ming-Chen Fu
- iChEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China)
| | - Rui Shang
- iChEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China).
| | - Wan-Min Cheng
- iChEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China)
| | - Yao Fu
- iChEM, CAS Key Laboratory of Urban Pollutant Conversion, Anhui Province Key Laboratory of Biomass Clean Energy, Department of Chemistry, University of Science and Technology of China, Hefei 230026 (China).
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Chen J, Chen EXY. Reactivity of Amine/E(C6F5)3 (E = B, Al) Lewis Pairs toward Linear and Cyclic Acrylic Monomers: Hydrogenation vs. Polymerization. Molecules 2015; 20:9575-90. [PMID: 26016548 PMCID: PMC6272166 DOI: 10.3390/molecules20069575] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 05/20/2015] [Accepted: 05/21/2015] [Indexed: 11/23/2022] Open
Abstract
This work reveals the contrasting reactivity of amine/E(C6F5)3 (E = B, Al) Lewis pairs toward linear and cyclic acrylic monomers, methyl methacrylate (MMA) and biorenewable γ-methyl-α-methylene-γ-butyrolactone (γMMBL). While mixing of 2,2,6,6-tetramethylpiperidine (TMP) and B(C6F5)3 leads to a frustrated Lewis pair (FLP), Et3N reacts with B(C6F5)3 to form disproportionation products, ammonium hydridoborate ionic pair and iminium zwitterion. On the other hand, the stoichiometric reaction of either TMP or Et3N with Al(C6F5)3 leads to clean formation of a classic Lewis adduct (CLA). Neither TMP nor Et3N, when paired with E(C6F5)3, polymerizes MMA, but the Et3N/2B(C6F5)3 pair promotes transfer hydrogenation of MMA to form methyl isobutyrate. In contrast, the amine/E(C6F5)3 pairs promote rapid polymerization of γMMBL carrying the more reactive exocyclic methylene moiety, achieving full conversion in less than 3 min even at a low catalyst loading of 0.0625 mol %. TMP is more effective than Et3N for the polymerization when paired with either the borane or the alane, while the alane exhibits higher polymerization activity than the borane when paired with Et3N. Overall, the TMP/Al(C6F5)3 system exhibits the highest polymerization activity, achieving a maximum turn-over frequency of 96,000 h-1 at 0.125 mol % of catalyst loading, producing high molecular weight PγMMBL with Mn = 1.29 × 105 g∙mol-1.
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Affiliation(s)
- Jiawei Chen
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA
| | - Eugene X-Y Chen
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA.
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Abstract
The concept of frustrated Lewis pairs (FLPs) has received considerable attention of late, and numerous reports have demonstrated the power of non- or weakly interacting Lewis acid–base pairs for the cooperative activation of small molecules. Although most studies have focused on the use of organic or main-group FLPs that utilize steric encumbrance to prevent adduct formation, a related strategy can be envisioned for both organic and inorganic complexes, in which "electronic frustration" engenders reactivity consistent with both nucleophilic (basic) and electrophilic (acidic) character. Here we propose that such a description is consistent with the behavior of many coordinatively unsaturated transition-metal species featuring metal–ligand multiple bonds, and we further demonstrate that the resultant reactivity may be a powerful tool for the functionalization of C–H and E–H bonds.
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Affiliation(s)
- Matthew T Whited
- Department of Chemistry, Carleton College, Northfield, MN, United States
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