1
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Zhang R, Xu J, Liu S, Si S, Chen J, Wang L, Chen WW, Zhao B. Direct Enantioselective α-C-H Conjugate Addition of Propargylamines to α,β-Unsaturated Ketones via Carbonyl Catalysis. J Am Chem Soc 2024; 146:25927-25933. [PMID: 39259771 DOI: 10.1021/jacs.4c09840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2024]
Abstract
Direct asymmetric α-C-H conjugate addition of propargylamines to α,β-unsaturated ketones remains a great challenge due to the low α-amino C-H acidity of propargylamines and the nucleophilic interference of the NH2 group. Utilizing a new type of pyridoxals featuring a benzene-pyridine biaryl skeleton and a bulky amide side chain as carbonyl catalyst, we have accomplished direct asymmetric α-C-H conjugate addition of NH2-unprotected propargylamines to α,β-unsaturated ketones. The adducts undergo subsequent in situ intramolecular cyclization, delivering a wide range of chiral polysubstituted 1-pyrrolines in high yields (up to 92%) with excellent diastereo- and enatioelectivities (up to >20:1 dr and 99% ee). This work has demonstrated a straightforward approach to access pharmaceutically important chiral 1-pyrrolines, and it has also provided an impressive instance of direct asymmetric functionalization of inert C-H bonds enabled by biomimetic organocatalysts.
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Affiliation(s)
- Ruixin Zhang
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
| | - Jiwei Xu
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
| | - Siqi Liu
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
| | - Shibo Si
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
| | - Jiayao Chen
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
| | - Lingxiao Wang
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
| | - Wen-Wen Chen
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
| | - Baoguo Zhao
- The Education Ministry Key Lab of Resource Chemistry, Shanghai Frontiers Science Center of Biomimetic Catalysis, and College of Chemistry and Materials Science, Shanghai Normal University, Shanghai 200234, China
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2
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Lops C, Pasquato L, Pengo P. Development of Organocatalytic Darzens Reactions Exploiting the Cyclopropenimine Superbase. Molecules 2024; 29:4350. [PMID: 39339345 PMCID: PMC11434499 DOI: 10.3390/molecules29184350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2024] [Revised: 09/03/2024] [Accepted: 09/07/2024] [Indexed: 09/30/2024] Open
Abstract
A truly organocatalytic approach to the Darzens reaction affording α,β-epoxy carbonyl compounds in good yields was developed taking advantage of the high basic strength and low nucleophilicity of cyclopropenimine superbases. The catalytic active free base can easily be generated in situ from its hydrochloride salt and maintained in the active deprotonated form by performing the reactions in a heterogeneous reaction system in the presence of excess potassium carbonate as a sacrificial base.
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Affiliation(s)
- Carmine Lops
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy
| | - Lucia Pasquato
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy
| | - Paolo Pengo
- Department of Chemical and Pharmaceutical Sciences, University of Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy
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3
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Tampellini N, Mercado BQ, Miller SJ. Scaffold-Oriented Asymmetric Catalysis: Conformational Modulation of Transition State Multivalency during a Catalyst-Controlled Assembly of a Pharmaceutically Relevant Atropisomer. Chemistry 2024; 30:e202401109. [PMID: 38507249 PMCID: PMC11132932 DOI: 10.1002/chem.202401109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 03/20/2024] [Indexed: 03/22/2024]
Abstract
A new class of superbasic, bifunctional peptidyl guanidine catalysts is presented, which enables the organocatalytic, atroposelective synthesis of axially chiral quinazolinediones. Computational modeling unveiled the conformational modulation of the catalyst by a novel phenyl urea N-cap, that preorganizes the structure into the active, folded state. A previously unanticipated noncovalent interaction involving a difluoroacetamide acting as a hybrid mono- or bidentate hydrogen bond donor emerged as a decisive control element inducing atroposelectivity. These discoveries spurred from a scaffold-oriented project inspired from a fascinating investigational BTK inhibitor featuring two stable chiral axes and relies on a mechanistic framework that was foreign to the extant lexicon of asymmetric catalysis.
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Affiliation(s)
- Nicolò Tampellini
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06511 (USA)
| | - Brandon Q. Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06511 (USA)
| | - Scott J. Miller
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06511 (USA)
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4
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Deka H, Fridman N, Eisen MS. Temperature Dependence of the Ring Opening of Cyclopropene Imines on Thorium Metallocenes. Inorg Chem 2024; 63:9572-9578. [PMID: 38471108 PMCID: PMC11134510 DOI: 10.1021/acs.inorgchem.3c04213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 02/13/2024] [Accepted: 02/20/2024] [Indexed: 03/14/2024]
Abstract
The reactions of two highly strained cyclopropenimine ligands L1H and L2H (L1H = N1,N1,N2,N2-tetraisopropyl-3-iminocycloprop-1-ene-1,2-diamine, L2H = N1,N1,N2,N2-tetracyclohexyl-3-iminocycloprop-1-ene-1,2-diamine) with three thorium precursors Cp*2ThCl2, Cp*2Th(Cl)(CH3), and Cp*2Th(CH3)2 were studied. At -20 °C, L1H and L2H react with Cp*2ThCl2 to form Th1 (Th1 = Cp*2ThCl2(L1H)) and Th2 (Th2 = Cp*2ThCl2(L2H)), respectively, where the neutral ligand coordinates to the thorium metal center. Coordination of the ligand to the thorium metal center introduces aromaticity at the cyclopropene ring of the ligand. Reaction at room temperature results in the ring opening of the ligand to form Th3 (Th3 = Cp*2ThCl2((Z)-2,3-bis(diisopropylamino)acrylonitrile) and Th4 (Th4 = Cp*2ThCl2((Z)-2,3-bis(dicyclohexylamino)acrylonitrile), where the cyclopropenimine converts into a nitrile and coordinates to the thorium metal center. Reaction of L1H and L2H with Cp*2Th(Cl)(CH3) and/or Cp*2Th(CH3)2 at -20 °C results in a rapid methanolysis reaction and forms Cp*2Th(L1/L2)(CH3/Cl)-type complexes Th5 (Th5 = Cp*2Th(L1)(CH3)), Th6 (Th6 = Cp*2Th(L2)(CH3), Th7 (Th7 = Cp*2Th(L1)(Cl), and Th8 (Th8 = Cp*2Th(L2)(Cl). On the other hand, at room temperature, these reactions result in a ring opening of the ligand. Room-temperature reaction of L1H and L2H with Cp*2Th(CH3)2 results in Th9 (Th9 = Cp*2Th(CH3)((Z)-3-imino-N1,N1,N2,N2-tetraisopropylbut-1-ene-1,2-diamine) and Th10 (Th10 = Cp*2Th(CH3)((Z)-3-imino-N1,N1,N2,N2-tetracyclohexylbut-1-ene-1,2-diamine). Similarly, at room temperature, L1H and L2H react with Cp*2Th(Cl)(CH3) to form Th11 (Th11 = Cp*2Th(Cl)((Z)-3-imino- N1,N1,N2,N2-tetraisopropylbut-1-ene-1,2-diamine) and Th12 (Th12 = Cp*2Th(Cl)((Z)-3-imino-N1,N1,N2,N2-tetracyclohexylbut-1-ene-1,2-diamine). The ring-opening reaction is assisted by the nucleophilic attack of the thorium-coordinated methyl group to the highly strained cyclopropene imine carbon.
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Affiliation(s)
- Hemanta Deka
- Schulich
Faculty of Chemistry, Technion-Israel Institute
of Technology, Haifa
City 3200003, Israel
- Department
of Chemistry, Goalpara College, Goalpara 783101, Assam, India
| | - Natalia Fridman
- Schulich
Faculty of Chemistry, Technion-Israel Institute
of Technology, Haifa
City 3200003, Israel
| | - Moris S. Eisen
- Schulich
Faculty of Chemistry, Technion-Israel Institute
of Technology, Haifa
City 3200003, Israel
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5
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Yan B, Ma P, Shu X, Yin W, Guo W. Merging of Palladium and Organocatalysis Enabled Asymmetric Decarboxylative (2+1) Cycloadditions toward Cyclopropanes. Org Lett 2024; 26:4274-4279. [PMID: 38727082 DOI: 10.1021/acs.orglett.4c01088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
A cascade reaction enabling enantio- and diastereoselective construction of strained cyclopropanes is described. This asymmetric (2+1) annulation process uses vinyl methylene carbonate and 2-cyanoacrylate as reaction partners in the presence of Pd(PPh3)4 as a precatalyst and an enantioenriched phosphoramidite ligand featuring a morpholine functionality. Mechanistic investigations unveil that the PPh3 derived from the Pd(PPh3)4 and the morpholine-containing phosphoramidite work as cooperative phosphorus and Brønsted base catalysts to promote the reaction.
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Affiliation(s)
- Biwei Yan
- Frontier Institute of Science and Technology (FIST), Xi'an Jiaotong University, Xi'an 710049, China
| | - Pengchen Ma
- School of Chemistry, Xi'an Key Laboratory of Sustainable Energy Material Chemistry and Engineering Research Center of Energy Storage Materials and Devices, Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China
| | - Xiao Shu
- Frontier Institute of Science and Technology (FIST), Xi'an Jiaotong University, Xi'an 710049, China
| | - Wenhao Yin
- Frontier Institute of Science and Technology (FIST), Xi'an Jiaotong University, Xi'an 710049, China
| | - Wusheng Guo
- Frontier Institute of Science and Technology (FIST), Xi'an Jiaotong University, Xi'an 710049, China
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6
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Pecchini P, Fochi M, Bartoccini F, Piersanti G, Bernardi L. Enantioselective organocatalytic strategies to access noncanonical α-amino acids. Chem Sci 2024; 15:5832-5868. [PMID: 38665517 PMCID: PMC11041364 DOI: 10.1039/d4sc01081g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 03/23/2024] [Indexed: 04/28/2024] Open
Abstract
Organocatalytic asymmetric synthesis has evolved over the years and continues to attract the interest of many researchers worldwide. Enantiopure noncanonical amino acids (ncAAs) are valuable building blocks in organic synthesis, medicinal chemistry, and chemical biology. They are employed in the elaboration of peptides and proteins with enhanced activities and/or improved properties compared to their natural counterparts, as chiral catalysts, in chiral ligand design, and as chiral building blocks for asymmetric syntheses of complex molecules, including natural products. The linkage of ncAA synthesis and enantioselective organocatalysis, the subject of this perspective, tries to imitate the natural biosynthetic process. Herein, we present contemporary and earlier developments in the field of organocatalytic activation of simple feedstock materials, providing potential ncAAs with diverse side chains, unique three-dimensional structures, and a high degree of functionality. These asymmetric organocatalytic strategies, useful for forging a wide range of C-C, C-H, and C-N bonds and/or combinations thereof, vary from classical name reactions, such as Ugi, Strecker, and Mannich reactions, to the most advanced concepts such as deracemisation, transamination, and carbene N-H insertion. Concurrently, we present some interesting mechanistic studies/models, providing information on the chirality transfer process. Finally, this perspective highlights, through the diversity of the amino acids (AAs) not selected by nature for protein incorporation, the most generic modes of activation, induction, and reactivity commonly used, such as chiral enamine, hydrogen bonding, Brønsted acids/bases, and phase-transfer organocatalysis, reflecting their increasingly important role in organic and applied chemistry.
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Affiliation(s)
- Pietro Pecchini
- Department of Industrial Chemistry "Toso Montanari", Center for Chemical Catalysis C3 & INSTM RU Bologna V. Gobetti 85 40129 Bologna Italy
| | - Mariafrancesca Fochi
- Department of Industrial Chemistry "Toso Montanari", Center for Chemical Catalysis C3 & INSTM RU Bologna V. Gobetti 85 40129 Bologna Italy
| | - Francesca Bartoccini
- Department of Biomolecular Sciences, University of Urbino Carlo Bo Piazza Rinascimento 6 61029 Urbino PU Italy
| | - Giovanni Piersanti
- Department of Biomolecular Sciences, University of Urbino Carlo Bo Piazza Rinascimento 6 61029 Urbino PU Italy
| | - Luca Bernardi
- Department of Industrial Chemistry "Toso Montanari", Center for Chemical Catalysis C3 & INSTM RU Bologna V. Gobetti 85 40129 Bologna Italy
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7
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Wu D, Martin RT, Piña J, Kwon J, Crockett MP, Thomas AA, Gutierrez O, Park NH, Hedrick JL, Campos LM. Cyclopropenimine-Mediated CO 2 Activation for the Synthesis of Polyurethanes and Small-Molecule Carbonates and Carbamates. Angew Chem Int Ed Engl 2024; 63:e202401281. [PMID: 38462499 PMCID: PMC11078573 DOI: 10.1002/anie.202401281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 02/29/2024] [Accepted: 03/05/2024] [Indexed: 03/12/2024]
Abstract
Carbon dioxide (CO2) is an abundant C1 feedstock with tremendous potential to produce versatile building blocks in synthetic applications. Given the adverse impact of CO2 on the atmosphere, it is of paramount importance to devise strategies for upcycling it into useful materials, such as polymers and fine chemicals. To activate such stable molecule, superbases offer viable modes of binding to CO2. In this study, a superbase cyclopropenimine derivative was found to exhibit exceptional proficiency in activating CO2 and mediating its polymerization at ambient temperature and pressure for the synthesis of polyurethanes. The versatility of this reaction can be extended to monofunctional amines and alcohols, yielding a variety of functional carbonates and carbamates.
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Affiliation(s)
- Dino Wu
- Department of Chemistry, Columbia University, 10027 New York, NY, USA
| | - Robert T. Martin
- Department of Chemistry & Biochemistry, University of Maryland, 8051 Regents Drive, College Park, 20742 Maryland, MD, USA
| | - Jeanette Piña
- Department of Chemistry, Texas A&M University, 3255 TAMU, 580 Ross St, 77843 College Station, TX, USA
| | - Junho Kwon
- Department of Chemistry, Columbia University, 10027 New York, NY, USA
| | - Michael P. Crockett
- Department of Chemistry, Texas A&M University, 3255 TAMU, 580 Ross St, 77843 College Station, TX, USA
| | - Andy A. Thomas
- Department of Chemistry, Texas A&M University, 3255 TAMU, 580 Ross St, 77843 College Station, TX, USA
| | - Osvaldo Gutierrez
- Department of Chemistry & Biochemistry, University of Maryland, 8051 Regents Drive, College Park, 20742 Maryland, MD, USA
- Department of Chemistry, Texas A&M University, 3255 TAMU, 580 Ross St, 77843 College Station, TX, USA
| | | | | | - Luis M. Campos
- Department of Chemistry, Columbia University, 10027 New York, NY, USA
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8
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Lee H, Nam H, Lee SY. Enantio- and Diastereoselective Variations on α-Iminonitriles: Harnessing Chiral Cyclopropenimine-Thiourea Organocatalysts. J Am Chem Soc 2024; 146:3065-3074. [PMID: 38281151 DOI: 10.1021/jacs.3c09911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2024]
Abstract
Chiral 1-pyrrolines containing a nitrile motif serve as crucial structural scaffolds in biologically active molecules and exhibit diversity as building blocks owing to their valuable functional groups; however, the asymmetric synthesis of such compounds remains largely unexplored. Herein, we present an enantio- and diastereoselective method for the synthesis of α-chiral nitrile-containing 1-pyrroline derivatives bearing vicinal stereocenters through the design and introduction of chiral cyclopropenimine-based bifunctional catalysts featuring a thiourea moiety. This synthesis entails a highly stereoselective conjugate addition of α-iminonitriles to a wide array of enones, followed by cyclocondensation, thereby affording a series of cyanopyrroline derivatives, some of which contain all-carbon quaternary centers. Moreover, we demonstrate the synthetic utility of this strategy by performing a gram-scale reaction with 1% catalyst loading, along with a variety of chemoselective transformations of the product, including the synthesis of a vildagliptin analogue. Finally, we showcase the selective synthesis of all four stereoisomers of the cyanopyrroline products through trans-to-cis isomerization, highlighting the versatility of our approach.
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Affiliation(s)
- Hooseung Lee
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
| | - Hyeongwoo Nam
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
| | - Sarah Yunmi Lee
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
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9
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Morodo R, Dumas DM, Zhang J, Lui KH, Hurst PJ, Bosio R, Campos LM, Park NH, Waymouth RM, Hedrick JL. Ring-Opening Polymerization of Cyclic Esters and Carbonates with (Thio)urea/Cyclopropenimine Organocatalytic Systems. ACS Macro Lett 2024:181-188. [PMID: 38252690 DOI: 10.1021/acsmacrolett.3c00716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Organocatalyzed ring-opening polymerization is a powerful tool for the synthesis of a variety of functional, readily degradable polyesters and polycarbonates. We report the use of (thio)ureas in combination with cyclopropenimine bases as a unique catalyst for the polymerization of cyclic esters and carbonates with a large span of reactivities. Methodologies of exceptionally effective and selective cocatalyst combinations were devised to produce polyesters and polycarbonates with narrow dispersities (Đ = 1.01-1.10). Correlations of the pKa of the various ureas and cyclopropenimine bases revealed the critical importance of matching the pKa of the two cocatalysts to achieve the most efficient polymerization conditions. It was found that promoting strong H-bonding interactions with a noncompetitive organic solvent, such as CH2Cl2, enabled greatly increased polymerization rates. The stereoselective polymerization of rac-lactide afforded stereoblock poly(lactides) that crystallize as stereocomplexes, as confirmed by wide-angle X-ray scattering.
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Affiliation(s)
- Romain Morodo
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - David M Dumas
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Jia Zhang
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Kai H Lui
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Paul J Hurst
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - Riccardo Bosio
- IBM Almaden Research Center, San Jose, California 95120, United States
| | - Luis M Campos
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Nathaniel H Park
- IBM Almaden Research Center, San Jose, California 95120, United States
| | - Robert M Waymouth
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States
| | - James L Hedrick
- IBM Almaden Research Center, San Jose, California 95120, United States
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10
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Chen J, Yang X, Huang Y, Zheng Z, Li T. The Development of Aldehyde Catalytic System. Chem Asian J 2023; 18:e202300731. [PMID: 37755436 DOI: 10.1002/asia.202300731] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 09/21/2023] [Accepted: 09/25/2023] [Indexed: 09/28/2023]
Abstract
Aldehyde catalysts have proven to be highly effective in facilitating and accelerating a wide range of challenging transformations in organic chemistry. This article is structured into three main sections, focusing on the utilization of aldehydes as organocatalysts, the aldehydes/transition metals catalytic systems, and photochemical initiators. Finally, we provide a concise summary of the advancements in this fascinating research field, offering our perspectives and insights.
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Affiliation(s)
- Jinli Chen
- National Key Laboratory of Green Pesticides, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University. Huaxi District, Guiyang, 550025, China
| | - Xiaoqun Yang
- National Key Laboratory of Green Pesticides, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University. Huaxi District, Guiyang, 550025, China
| | - Yixian Huang
- National Key Laboratory of Green Pesticides, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University. Huaxi District, Guiyang, 550025, China
| | - Zhiguo Zheng
- National Key Laboratory of Green Pesticides, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University. Huaxi District, Guiyang, 550025, China
| | - Tingting Li
- National Key Laboratory of Green Pesticides, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University. Huaxi District, Guiyang, 550025, China
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11
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Stockhammer L, Craik R, Monkowius U, Cordes DB, Smith AD, Waser M. Isothiourea-Catalyzed Enantioselective Functionalisation of Glycine Schiff Base Aryl Esters via 1,6- and 1,4-Additions. CHEMISTRYEUROPE 2023; 1:e202300015. [PMID: 38882579 PMCID: PMC7616101 DOI: 10.1002/ceur.202300015] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Indexed: 06/18/2024]
Abstract
The enantioselective α-functionalisation of glycine Schiff base aryl esters through isothiourea catalysis is successfully demonstrated for 1,6-additions to para-quinone methides (21 examples, up to 95:5 dr and 96:4 er) and 1,4-additions to methylene substituted dicarbonyl or disulfonyl Michael acceptors (17 examples, up to 98:2 er). This nucleophilic organocatalysis approach gives access to a range of α-functionalised α-amino acid derivatives and further transformations of the activated aryl ester group provide a straightforward entry to advanced amino acid-based esters, amides or thioesters.
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Affiliation(s)
- Lotte Stockhammer
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz (Austria)
| | - Rebecca Craik
- EaStCHEM, School of Chemistry, University of St Andrews, KY16 9ST St Andrews, Fife, (UK)
| | - Uwe Monkowius
- School of Education, Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz (Austria)
| | - David B Cordes
- EaStCHEM, School of Chemistry, University of St Andrews, KY16 9ST St Andrews, Fife, (UK)
| | - Andrew D Smith
- EaStCHEM, School of Chemistry, University of St Andrews, KY16 9ST St Andrews, Fife, (UK)
| | - Mario Waser
- Institute of Organic Chemistry, Johannes Kepler University Linz, Altenbergerstrasse 69, 4040 Linz (Austria)
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12
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Rozsar D, Farley AJM, McLauchlan I, Shennan BDA, Yamazaki K, Dixon DJ. Bifunctional Iminophosphorane-Catalyzed Enantioselective Nitroalkane Addition to Unactivated α,β-Unsaturated Esters. Angew Chem Int Ed Engl 2023; 62:e202303391. [PMID: 36929179 PMCID: PMC10946890 DOI: 10.1002/anie.202303391] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 03/18/2023]
Abstract
Herein we describe the enantioselective intermolecular conjugate addition of nitroalkanes to unactivated α,β-unsaturated esters, catalyzed by a bifunctional iminophosphorane (BIMP) superbase. The transformation provides the most direct access to pharmaceutically relevant enantioenriched γ-nitroesters, utilizing feedstock chemicals, with unprecedented selectivity. The methodology exhibits a broad substrate scope, including β-(fluoro)alkyl, aryl and heteroaryl substituted electrophiles, and was successfully applied on a gram scale with reduced catalyst loading, and, additionally, catalyst recovery was carried out. The formal synthesis of a range of drug molecules, and an enantioselective synthesis of (S)-rolipram were achieved. Additionally, computational studies revealed key reaction intermediates and transition state structures, and provided rationale for high enantioselectivities, in good agreement with experimental results.
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Affiliation(s)
- Daniel Rozsar
- Department of ChemistryUniversity of OxfordChemistry Research LaboratoryOX1 3TAOxfordUK
| | - Alistair J. M. Farley
- Department of ChemistryUniversity of OxfordChemistry Research LaboratoryOX1 3TAOxfordUK
| | - Iain McLauchlan
- Department of ChemistryUniversity of OxfordChemistry Research LaboratoryOX1 3TAOxfordUK
| | | | - Ken Yamazaki
- Division of Applied ChemistryOkayama University700-8530TsushimanakaOkayamaJapan
| | - Darren J. Dixon
- Department of ChemistryUniversity of OxfordChemistry Research LaboratoryOX1 3TAOxfordUK
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13
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Kőnig B, Sztanó G, Holczbauer T, Soós T. Syntheses of 2- and 3-Substituted Morpholine Congeners via Ring Opening of 2-Tosyl-1,2-Oxazetidine. J Org Chem 2023; 88:6182-6191. [PMID: 37125664 PMCID: PMC10167689 DOI: 10.1021/acs.joc.3c00207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Diastereoselective and diastereoconvergent syntheses of 2- and 3-substituted morpholine congeners are reported. Starting from tosyl-oxazatedine 1 and α-formyl carboxylates 2, base catalysis is utilized to yield morpholine hemiaminals. Their further synthetic elaborations allowed the concise constructions of conformationally rigid morpholines. The observed diastereoselectivities and the unusual diastereoconvergence in the photoredox radical processes seem to be the direct consequence of the avoidance of pseudo A1,3 strain between the C-3 substituent and the N-tosyl group and the anomeric effect of oxygen atoms.
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Affiliation(s)
- Bálint Kőnig
- Institute of Organic Chemistry, Research Centre for Natural Sciences, 2 Magyar tudósok körútja, H-1117 Budapest, Hungary
- Hevesy György PhD School of Chemistry, Eötvös Loránd University, 1/A Pázmány Péter sétány, H-1117 Budapest, Hungary
| | - Gábor Sztanó
- Institute of Organic Chemistry, Research Centre for Natural Sciences, 2 Magyar tudósok körútja, H-1117 Budapest, Hungary
- Hevesy György PhD School of Chemistry, Eötvös Loránd University, 1/A Pázmány Péter sétány, H-1117 Budapest, Hungary
| | - Tamás Holczbauer
- Institute of Organic Chemistry, Research Centre for Natural Sciences, 2 Magyar tudósok körútja, H-1117 Budapest, Hungary
- Centre for Structural Science, Research Centre for Natural Sciences, 2 Magyar tudósok körútja, H-1117 Budapest, Hungary
| | - Tibor Soós
- Institute of Organic Chemistry, Research Centre for Natural Sciences, 2 Magyar tudósok körútja, H-1117 Budapest, Hungary
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14
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Tataroğlu M, Sungur FA. Mechanistic insights into the challenges of organocatalytic Beckmann rearrangement reactions. Org Biomol Chem 2023; 21:1254-1263. [PMID: 36633313 DOI: 10.1039/d2ob01641a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Organocatalytic Beckmann rearrangement (BKR) reactions are of great interest for synthetic chemists interested in "green chemistry". There are different proposals for the reaction mechanism depending on the experimental conditions. Clarifying the details of the BKR reaction mechanism is important for the selectivity of amides and lactams yet to be synthesized. In this study, the DFT computational method at the M06-2X/6-31+G(d,p) level of theory in conjunction with the implicit PCM solvation method has been used to elucidate alternative pathways for the Beckmann rearrangement reaction at elevated temperatures. The results enabled us to explain details of the Beckmann rearrangement reaction via a Meisenheimer complex where the process was thermodynamically driven. Meisenheimer complexes are found to be highly stable species due to the presence of aromatic ring systems allowing electron delocalization.
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Affiliation(s)
- Melin Tataroğlu
- Informatics Institute, Computational Science and Engineering, Istanbul Technical University, Ayazağa Campus, Maslak, Istanbul, Turkey.
| | - Fethiye Aylin Sungur
- Informatics Institute, Computational Science and Engineering, Istanbul Technical University, Ayazağa Campus, Maslak, Istanbul, Turkey.
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15
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Li Q, Zhang W, Zhu C, Pan H, Shi KY, Zhang Y, Han MY, Tan CH. Organobase-Catalyzed Umpolung of Amides: The Generation and Transfer of Carbamoyl Anion. J Org Chem 2023; 88:1245-1255. [PMID: 36628963 DOI: 10.1021/acs.joc.2c02487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A novel organobase-catalyzed umpolung reaction of amides was disclosed. This method provides an efficient method to generate and transfer carbamoyl anions. In this transformation, some of the inherent disadvantages of carbamoyl metal were avoided. The mechanistic analysis revealed that the reaction proceeds through polarity inversion of amide, and various carbamoyl anions were applied in the reaction. Moreover, a wide range of substrates was achieved with moderate to excellent yield.
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Affiliation(s)
- Qi Li
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, College of Chemistry and Materials Science, Huabei Normal University, Huaibei, Anhui 235000, PR China
| | - Wang Zhang
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, College of Chemistry and Materials Science, Huabei Normal University, Huaibei, Anhui 235000, PR China
| | - Chen Zhu
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, College of Chemistry and Materials Science, Huabei Normal University, Huaibei, Anhui 235000, PR China
| | - Hong Pan
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, College of Chemistry and Materials Science, Huabei Normal University, Huaibei, Anhui 235000, PR China
| | - Kang-Yue Shi
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, College of Chemistry and Materials Science, Huabei Normal University, Huaibei, Anhui 235000, PR China
| | - Yicheng Zhang
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, College of Chemistry and Materials Science, Huabei Normal University, Huaibei, Anhui 235000, PR China
| | - Man-Yi Han
- Key Laboratory of Green and Precise Synthetic Chemistry and Applications, Ministry of Education, College of Chemistry and Materials Science, Huabei Normal University, Huaibei, Anhui 235000, PR China
| | - Choon-Hong Tan
- Division of Chemistry and Biological Chemistry, Nanyang Technological University, Singapore 637371
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16
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Abstract
Cyclopropenium ions are the smallest class of aromatic compounds, satisfying Hückel's rules of aromaticity with two π electrons within a three-membered ring. First prepared by Breslow in 1957, cyclopropenium ions have been found to possess extraordinary stability despite being both cationic and highly strained. In the 65 years since their first preparation, cyclopropenium ions have been the subject of innumerable studies concerning their synthesis, physical properties, and reactivity. However, prior to our work, the reactivity of these unique carbocations had not been exploited for reaction promotion or catalysis.Over the past 13 years, we have been exploring aromatic ions as unique and versatile building blocks for the development of catalysts for organic chemistry. A major portion of this work has been focused on leveraging the remarkable properties of the smallest of the aromatic ions─cyclopropeniums─as a design element in the invention of highly reactive catalysts. Indeed, because of its unique profile of hydrolytic stability, compact geometry, and relatively easy oxidizability, the cyclopropenium ring has proven to be a highly advantageous construction module for catalyst invention.In this Account, we describe some of our work using cyclopropenium ions as a key element in the design of novel catalysts. First, we discuss our early work aimed at promoting dehydrative reactions, starting with Appel-type chlorodehydrations of alcohols and carboxylic acids, cyclic ether formations, and Beckmann rearrangements and culminating in the realization of catalytic chlorodehydrations of alcohols and a catalytic Mitsunobu-type reaction. Next, we describe the development of cyclopropenimines as strong, neutral organic Brønsted bases and, in particular, the use of chiral cyclopropenimines for enantioselective Brønsted catalysis. We also describe the development of higher-order cyclopropenimine superbases. The use of tris(amino)cyclopropenium (TAC) ions as a novel class of phase-transfer catalysts is discussed for the reaction of epoxides with carbon dioxide. Next, we describe the formation of a cyclopropenone radical cation that has a portion of its spin density on the oxygen atom, leading to some peculiar metal ligand behavior. Finally, we discuss recent work that employs TAC electrophotocatalysts for oxidation reactions. The key intermediate for this chemistry is a TAC radical dication, which as an open-shell photocatalyst has remarkably strong excited-state oxidizing power. We describe the application of this strategy to transformations ranging from the oxidative functionalization of unactivated arenes to the regioselective derivatization of ethers, C-H aminations, vicinal C-H diaminations, and finally aryl olefin dioxygenations. Collectively, these catalytic platforms demonstrate the utility of charged aromatic rings, and cyclopropenium ions in particular, to enable unique advances in catalysis.
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Affiliation(s)
- Rebecca M Wilson
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Tristan H Lambert
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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17
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Modeling pKa of the Brønsted Bases as an Approach to the Gibbs Energy of the Proton in Acetonitrile. Int J Mol Sci 2022; 23:ijms231810576. [PMID: 36142490 PMCID: PMC9502073 DOI: 10.3390/ijms231810576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 11/17/2022] Open
Abstract
A simple but efficient computational approach to calculate pKa in acetonitrile for a set of phosphorus, nitrogen, and carbon bases was established. A linear function that describes relations between the calculated ΔG’a.sol(BH+) and pKa values was determined for each group of bases. The best model was obtained through the variations in the basis set, in the level of theory (density functionals or MP2), and in the continuum solvation model (IPCM, CPCM, or SMD). The combination of the IPCM/B3LYP/6-311+G(d,p) solvation approach with MP2/6-311+G(2df,p)//B3LYP/6-31G(d) gas-phase energies provided very good results for all three groups of bases with R2 values close to or above 0.99. Interestingly, the slopes and the intercepts of the obtained linear functions showed significant deviations from the theoretical values. We made a linear plot utilizing all the conducted calculations and all the structural variations and employed methods to prove the systematic nature of the intercept/slope dependence. The interpolation of the intercept to the ideal slope value enabled us to determine the Gibbs energy of the proton in acetonitrile, which amounted to −258.8 kcal mol−1. The obtained value was in excellent agreement with previously published results.
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18
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Muñoz Sánchez GM, Zdilla MJ. Crystal structure of N-butyl-2,3-bis-(di-cyclo-hexyl-amino)-cyclo-propeniminium chloride benzene monosolvate. Acta Crystallogr E Crystallogr Commun 2022; 78:936-941. [PMID: 36072514 PMCID: PMC9443799 DOI: 10.1107/s2056989022008076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2021] [Accepted: 08/11/2022] [Indexed: 11/16/2022]
Abstract
N-Butyl-2,3-bis-(di-cyclo-hexyl-amino)-cyclo-propenimine (1) crystallizes from benzene and hexa-nes in the presence of HCl as a mono-benzene solvate of the hydro-chloride salt, [1H]Cl·C6H6 or C31H54N3 +·Cl-·C6H6, in the P21/n space group. The protonation of 1 results in the generation of an aromatic structure based upon the delocalization of the cyclo-propene double bond around the cyclo-propene ring, giving three inter-mediate C-C bond lengths of ∼1.41 Å, and the delocalization of the imine-type C-N double bond, giving three inter-mediate C-N bond lengths of ∼1.32 Å. Ion-ion and ion-benzene packing inter-actions are described and illustrated.
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Affiliation(s)
- Gaby M. Muñoz Sánchez
- Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, PA 19122, USA
| | - Michael J. Zdilla
- Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, PA 19122, USA
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19
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Cabrera-Trujillo JJ, Fernández I. Aromaticity-enhanced reactivity of geminal frustrated Lewis pairs. Chem Commun (Camb) 2022; 58:6801-6804. [PMID: 35611955 DOI: 10.1039/d2cc02013k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The presence of a cyclopropenimine moiety as the Lewis base partner in geminal frustrated Lewis pairs greatly enhances the reactivity of the system towards the activation of small molecules. This is mainly due to an increase of the aromaticity strength of this fragment during the activation reaction which results in a significant gain of stability ultimately leading to low barrier and high exergonic transformations.
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Affiliation(s)
- Jorge Juan Cabrera-Trujillo
- Departamento de Química Orgánica I and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040-Madrid, Spain.
| | - Israel Fernández
- Departamento de Química Orgánica I and Centro de Innovación en Química Avanzada (ORFEO-CINQA), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040-Madrid, Spain.
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20
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Guerrero-Corella A, Fraile A, Alemán J. Intramolecular Hydrogen-Bond Activation: Strategies, Benefits, and Influence in Catalysis. ACS ORGANIC & INORGANIC AU 2022; 2:197-204. [PMID: 35673681 PMCID: PMC9164241 DOI: 10.1021/acsorginorgau.1c00053] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/21/2022] [Accepted: 01/21/2022] [Indexed: 12/12/2022]
Abstract
![]()
The activation of
molecules through intramolecular hydrogen-bond
formation to promote chemical reactions appears as a suitable strategy
in organic synthesis, especially for the preparation of chiral compounds
under metal and organocatalytic conditions. The use of this interaction
has enabled reactivity enhancement of reagents, as well as stabilization
of the chemical species and enantiocontrol of the processes.
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Affiliation(s)
| | - Alberto Fraile
- Organic Chemistry Department, Módulo 1, Universidad Autónoma de Madrid, 28049 Madrid, Spain.,Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - José Alemán
- Organic Chemistry Department, Módulo 1, Universidad Autónoma de Madrid, 28049 Madrid, Spain.,Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
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21
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Bai YJ, Cheng ML, Zheng XH, Zhang SY, Wang PA. Chiral Cyclopropenimine-catalyzed Asymmetric Michael Addition of Bulky Glycine Imine to α,β-Unsaturated Isoxazoles. Chem Asian J 2022; 17:e202200131. [PMID: 35415949 DOI: 10.1002/asia.202200131] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 03/26/2022] [Indexed: 11/11/2022]
Abstract
A highly efficient asymmetric Michael addition of bulky glycine imine to α,β-unsaturated isoxazoles has been achieved by using 5 mol% of chiral cyclopropenimine as a chiral organo-superbase catalyst under mild conditions. Michael adducts were obtained in excellent yields (up to 97%) and stereoselectivities (up to>99 : 1 dr and 98% ee). A significant solvent effect was found in these chiral organosuperbase catalyzed asymmetric Michael reactions. Gram-scale preparation of Michael adducts and their transformations are realized to provide corresponding products without loss of stereoselectivities. The configurations of Michael adduct was determined by single-crystal X-ray diffraction analysis.
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Affiliation(s)
- Yu-Jun Bai
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, The College of Life Sciences, Northwest University, Xi'an, 710069, P. R. China) E-mails.,Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
| | - Mei-Ling Cheng
- Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
| | - Xiao-Hui Zheng
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, The College of Life Sciences, Northwest University, Xi'an, 710069, P. R. China) E-mails
| | - Sheng-Yong Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, The College of Life Sciences, Northwest University, Xi'an, 710069, P. R. China) E-mails.,Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
| | - Ping-An Wang
- Department of Medicinal Chemistry and Pharmaceutical Analysis, School of Pharmacy, Fourth Military Medical University, Xi'an, 710032, P. R. China
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22
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Rozsar D, Formica M, Yamazaki K, Hamlin TA, Dixon DJ. Bifunctional Iminophosphorane-Catalyzed Enantioselective Sulfa-Michael Addition to Unactivated α,β-Unsaturated Amides. J Am Chem Soc 2022; 144:1006-1015. [PMID: 34990142 PMCID: PMC8793149 DOI: 10.1021/jacs.1c11898] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
![]()
The
first metal-free catalytic intermolecular enantioselective
Michael addition to unactivated α,β-unsaturated amides
is described. Consistently high enantiomeric excesses and yields were
obtained over a wide range of alkyl thiol pronucleophiles and electrophiles
under mild reaction conditions, enabled by a novel squaramide-based
bifunctional iminophosphorane catalyst. Low catalyst loadings (2.0
mol %) were achieved on a decagram scale, demonstrating the scalability
of the reaction. Computational analysis revealed the origin of the
high enantiofacial selectivity via analysis of relevant transition
structures and provided substantial support for specific noncovalent
activation of the carbonyl group of the α,β-unsaturated
amide by the catalyst.
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Affiliation(s)
- Daniel Rozsar
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Michele Formica
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Ken Yamazaki
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom.,Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Trevor A Hamlin
- Department of Theoretical Chemistry, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Amsterdam Center for Multiscale Modeling (ACMM), Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
| | - Darren J Dixon
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
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23
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Saha A, Ganguly B. The design of C2-chiral bases with dual basic sites predicted to exceed the range of superbasicity: a computational study. NEW J CHEM 2022. [DOI: 10.1039/d2nj03537e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A set of C2-chiral bases with bis-protonation sites (1–9) on dimethyl-binaphthalene derivatives have been explored using the B3LYP/6-311+G(d,p) level and the proton affinities calculated are in the range of superbases for both the sites.
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Affiliation(s)
- Anusuya Saha
- Computation and Simulation Unit, Analytical and Environmental Science Division and Centralized Instrument Facility, CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat-364002, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Bishwajit Ganguly
- Computation and Simulation Unit, Analytical and Environmental Science Division and Centralized Instrument Facility, CSIR-Central Salt & Marine Chemicals Research Institute, Bhavnagar, Gujarat-364002, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
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24
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Wang CG, Li N, Wu G, Lin TT, Lee AMX, Yang SW, Li Z, Luo DHK. Carbon Dioxide Mediated Cellulose Dissolution and Derivatization to Cellulose Carbonates in a Low-pressure System. CARBOHYDRATE POLYMER TECHNOLOGIES AND APPLICATIONS 2022. [DOI: 10.1016/j.carpta.2022.100186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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25
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Liu ZC, Yue WJ, Yin L. Copper(I)-Catalyzed Asymmetric Synthesis of Unnatural α-Amino Acid Derivatives and Related Peptides Containing γ-(aza)Aryls. J Org Chem 2021; 87:399-405. [PMID: 34908422 DOI: 10.1021/acs.joc.1c02426] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chiral α-amino acids are indispensable compounds in organic chemistry, biochemistry, and medicinal chemistry. Herein, by means of copper(I)-catalyzed asymmetric conjugate addition of derivatives of glycine, serine, cysteine, and β-amino-alanine to electron-deficient vinyl(aza)arenes, an array of novel unnatural chiral α-amino acid derivatives bearing a γ-(aza)aryl is prepared in moderate to high yields with high enantioselectivity. Various azaarenes, such as pyrimidine, 1,3,5-triazine, pyridine, pyridine-N-oxide, quinoline, quinoxaline, purine, benzo[d]imidazole, benzothiazole, and 1,2,4-oxadiazole, are well tolerated. Moreover, the electrophiles are nicely extended to (Z)/(E) mixtures of electron-deficient butadienylpyridine and benzene, which are transformed to the corresponding chiral α-amino acid derivatives in high (E)/(Z) ratio and high enantioselectivity. More importantly, the present methodology is successfully applied in the catalytic asymmetric functionalization of Schiff bases derived from peptides, which finally afforded a new chiral tripeptide bearing two electron-deficient azaaryls and one electron-deficient aryl in high total yield with high diastereo- and excellent enantioselectivities.
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Affiliation(s)
- Zong-Ci Liu
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, 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
| | - Wen-Jun Yue
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, 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
| | - Liang Yin
- CAS Key Laboratory of Synthetic Chemistry of Natural Substances, 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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26
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Ranga PK, Ahmad F, Singh G, Tyagi A, Vijaya Anand R. Recent advances in the organocatalytic applications of cyclopropene- and cyclopropenium-based small molecules. Org Biomol Chem 2021; 19:9541-9564. [PMID: 34704583 DOI: 10.1039/d1ob01549d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The development of novel small molecule-based catalysts for organic transformations has increased noticeably in the last two decades. A very recent addition to this particular research area is cyclopropene- and cyclopropenium-based catalysts. At one point in time, particularly in the mid-20th century, much attention was focused on the structural aspects and physical properties of cyclopropene-based compounds. However, a paradigm shift was observed in the late 20th century, and the focus shifted to the synthetic utility of these compounds. In fact, a wide range of cyclopropene derivatives have been found serving as valuable synthons for the construction of carbocycles, heterocycles and other useful organic compounds. In the last few years, the catalytic applications of cyclopropene/cyclopropenium-based compounds have been uncovered and many synthetic protocols have been developed using cyclopropene-based compounds as organocatalysts. Therefore, the main objective of this review is to highlight recent developments in the catalytic applications of cyclopropene-based small molecules in different areas of organocatalysis such as phase-transfer catalysis (PTC), Brønsted base catalysis, hydrogen-bond donor catalysis, nucleophilic carbene catalysis, and electrophotocatalysis developed within the past two decades.
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Affiliation(s)
- Pavit K Ranga
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Feroz Ahmad
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Gurdeep Singh
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Akshi Tyagi
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
| | - Ramasamy Vijaya Anand
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, S.A.S Nagar, Manauli (PO), Punjab - 140306, India.
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27
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DBU-catalyzed Michael addition of bulky glycine imine to α,β-unsaturated isoxazoles and pyrazolamides. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132511] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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28
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Oguz M, Yildirim A, Durmus IM, Karakurt S, Yilmaz M. Synthesis of new calix[4]arene derivatives and evaluation of their cytotoxic activity. Med Chem Res 2021. [DOI: 10.1007/s00044-021-02813-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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29
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Kim B, Song Y, Lee SY. Stereodivergent silver-catalyzed synthesis of pyroglutamic acid esters. Chem Commun (Camb) 2021; 57:11052-11055. [PMID: 34608900 DOI: 10.1039/d1cc04875a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report here a silver-catalyzed method for the enantio- and diastereodivergent synthesis of chiral pyroglutamic acid esters with multiple stereocenters. This process proceeds through asymmetric conjugate addition of glycine imine esters to a broad range of β-substituted α,β-unsaturated perfluorophenyl esters followed by lactamization. By leveraging catalyst control and stereospecificity of the 1,4-addition process, all four product stereoisomers containing two adjacent stereocenters are accessible with high stereoselectivity.
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Affiliation(s)
- Byungjun Kim
- Department of Chemistry, Yonsei University, Seoul 03722, South Korea.
| | - Yuna Song
- Department of Chemistry, Yonsei University, Seoul 03722, South Korea.
| | - Sarah Yunmi Lee
- Department of Chemistry, Yonsei University, Seoul 03722, South Korea.
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30
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Leonardi C, Brandolese A, Preti L, Bortolini O, Polo E, Dambruoso P, Ragno D, Di Carmine G, Massi A. Expanding the Toolbox of Heterogeneous Asymmetric Organocatalysts: Bifunctional Cyclopropenimine Superbases for Enantioselective Catalysis in Batch and Continuous Flow. Adv Synth Catal 2021. [DOI: 10.1002/adsc.202100757] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Costanza Leonardi
- Department of Chemical, Pharmaceutical and Agricultural Sciences University of Ferrara Via L. Borsari 46 44121 Ferrara Italy
| | - Arianna Brandolese
- Department of Chemical, Pharmaceutical and Agricultural Sciences University of Ferrara Via L. Borsari 46 44121 Ferrara Italy
| | - Lorenzo Preti
- Department of Chemical, Pharmaceutical and Agricultural Sciences University of Ferrara Via L. Borsari 46 44121 Ferrara Italy
| | - Olga Bortolini
- Department of Chemical, Pharmaceutical and Agricultural Sciences University of Ferrara Via L. Borsari 46 44121 Ferrara Italy
| | - Eleonora Polo
- Istituto per la Sintesi Organica e la Fotoreattività Consiglio Nazionale delle Ricerche Via P. Gobetti, 101 40129 Bologna Italy
| | - Paolo Dambruoso
- Istituto per la Sintesi Organica e la Fotoreattività Consiglio Nazionale delle Ricerche Via P. Gobetti, 101 40129 Bologna Italy
| | - Daniele Ragno
- Department of Chemical, Pharmaceutical and Agricultural Sciences University of Ferrara Via L. Borsari 46 44121 Ferrara Italy
| | - Graziano Di Carmine
- Department of Chemical, Pharmaceutical and Agricultural Sciences University of Ferrara Via L. Borsari 46 44121 Ferrara Italy
| | - Alessandro Massi
- Department of Chemical, Pharmaceutical and Agricultural Sciences University of Ferrara Via L. Borsari 46 44121 Ferrara Italy
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31
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Seibel ZM, Bandar JS, Lambert TH. Enantioenriched α-substituted glutamates/pyroglutamates via enantioselective cyclopropenimine-catalyzed Michael addition of amino ester imines. Beilstein J Org Chem 2021; 17:2077-2084. [PMID: 34476014 PMCID: PMC8381810 DOI: 10.3762/bjoc.17.134] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 08/04/2021] [Indexed: 11/25/2022] Open
Abstract
A procedure for the enantioselective synthesis of α-substituted glutamates and pyroglutamates via a cyclopropenimine-catalyzed Michael addition of amino ester imines is described. Enantioselectivities of up to 94% have been achieved, and a variety of functional groups were found to be compatible. The impact of the catalyst structure and imine substitution is discussed. Compared to other methods, this protocol allows for a broader and more enantioselective access to pyroglutamate derivatives.
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Affiliation(s)
- Zara M Seibel
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Jeffrey S Bandar
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Tristan H Lambert
- Department of Chemistry, Columbia University, New York, New York 10027, USA.,Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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32
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Push–Pull Effect on the Gas-Phase Basicity of Nitriles: Transmission of the Resonance Effects by Methylenecyclopropene and Cyclopropenimine π-Systems Substituted by Two Identical Strong Electron Donors. Symmetry (Basel) 2021. [DOI: 10.3390/sym13091554] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The gas-phase basicity of nitriles can be enhanced by a push–pull effect. The role of the intercalated scaffold between the pushing group (electron-donor) and the pulling (electron-acceptor) nitrile group is crucial in the basicity enhancement, simultaneously having a transmission function and an intrinsic contribution to the basicity. In this study, we examine the methylenecyclopropene and the N-analog, cyclopropenimine, as the smallest cyclic π systems that can be considered for resonance propagation in a push–pull system, as well as their derivatives possessing two strong pushing groups (X) attached symmetrically to the cyclopropene scaffold. For basicity and push–pull effect investigations, we apply theoretical methods (DFT and G2). The effects of geometrical and rotational isomerism on the basicity are explored. We establish that the protonation of the cyano group is always favored. The push–pull effect of strong electron donor X substituents is very similar and the two π-systems appear to be good relays for this effect. The effects of groups in the two cyclopropene series are found to be proportional to the effects in the directly substituted nitrile series X–C≡N. In parallel to the basicity, changes in electron delocalization caused by protonation are also assessed on the basis of aromaticity indices. The calculated proton affinities of the nitrile series reported in this study enrich the gas-phase basicity scale of nitriles to around 1000 kJ mol−1.
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33
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Vazdar K, Margetić D, Kovačević B, Sundermeyer J, Leito I, Jahn U. Design of Novel Uncharged Organic Superbases: Merging Basicity and Functionality. Acc Chem Res 2021; 54:3108-3123. [PMID: 34308625 DOI: 10.1021/acs.accounts.1c00297] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
ConspectusOne of the constant challenges of synthetic chemistry is the molecular design and synthesis of nonionic, metal-free superbases as chemically stable neutral organic compounds of moderate molecular weight, intrinsically high thermodynamic basicity, adaptable kinetic basicity, and weak or tunable nucleophilicity at their nitrogen, phosphorus, or carbon basicity centers. Such superbases can catalyze numerous reactions, ranging from C-C bond formation to cycloadditions and polymerization, to name just a few. Additional benefits of organic superbases, as opposed to their inorganic counterparts, are their solubility in organic reaction media, mild reaction conditions, and higher selectivity. Approaching such superbasic compounds remains a continuous challenge. However, recent advances in synthetic methodology and theoretical understanding have resulted in new design principles and synthetic strategies toward superbases. Our computational contributions have demonstrated that the gas-phase basicity region of 350 kcal mol-1 and even beyond is easily reachable by organosuperbases. However, despite record-high basicities, the physical limitations of many of these compounds become quickly evident. The typically large molecular weight of these molecules and their sensitivity to ordinary reaction conditions prevent them from being practical, even though their preparation is often not too difficult. Thus, obviously structural limitations with respect to molecular weight and structural complexity must be imposed on the design of new synthetically useful organic superbases, but strategies for increasing their basicity remain important.The contemporary design of novel organic superbases is illustrated by phosphazenyl phosphanes displaying gas-phase basicities (GB) above 300 kcal mol-1 but having molecular weights well below 1000 g·mol-1. This approach is based on a reconsideration of phosphorus(III) compounds, which goes along with increasing their stability in solution. Another example is the preparation of carbodiphosphoranes incorporating pyrrolidine, tetramethylguanidine, or hexamethylphosphazene as a substituent. With gas-phase proton affinities of up to 300 kcal mol-1, they are among the top nonionic carbon bases on the basicity scale. Remarkably, the high basicity of these compounds is achieved at molecular weights of around 600 g·mol-1. Another approach to achieving high basicity through the cooperative effect of multiple intramolecular hydrogen bonding, which increases the stabilization of conjugate acids, has recently been confirmed.This Account focuses on our efforts to produce superbasic molecules that embody many desirable traits, but other groups' approaches will also be discussed. We reveal the crucial structural features of superbases and place them on known basicity scales. We discuss the emerging potential and current limits of their application and give a general outlook into the future.
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Affiliation(s)
- Katarina Vazdar
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, v.v.i. Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | | | | | - Jörg Sundermeyer
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg, Germany
| | - Ivo Leito
- Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu, Estonia
| | - Ullrich Jahn
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, v.v.i. Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
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34
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Guo F, Chen J, Huang Y. A Bifunctional N-Heterocyclic Carbene as a Noncovalent Organocatalyst for Enantioselective Aza-Michael Addition Reactions. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01908] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Fangfang Guo
- State Key Laboratory of Chemical Oncogenomics, Peking University Shenzhen Graduate School, Shenzhen 518055, People’s Republic of China
| | - Jiean Chen
- Shenzhen Bay Laboratory, Shenzhen 518055, People’s Republic of China
| | - Yong Huang
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, People’s Republic of China
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35
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Ma J, Zhou Q, Song G, Song Y, Zhao G, Ding K, Zhao B. Enantioselective Synthesis of Pyroglutamic Acid Esters from Glycinate via Carbonyl Catalysis. Angew Chem Int Ed Engl 2021; 60:10588-10592. [PMID: 33554429 DOI: 10.1002/anie.202017306] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/28/2021] [Indexed: 12/18/2022]
Abstract
Direct α-functionalization of NH2 -free glycinates with relatively weak electrophiles such as α,β-unsaturated esters still remains a big challenge in organic synthesis. With chiral pyridoxal 5 d as a carbonyl catalyst, direct asymmetric conjugated addition at the α-C of glycinate 1 a with α,β-unsaturated esters 2 has been successfully realized, to produce various chiral pyroglutamic acid esters 4 in 14-96 % yields with 81-97 % ee's after in situ lactamization. The trans and cis diastereomers can be obtained at the same time by chromatography and both of them can be easily converted into chiral 4-substituted pyrrolidin-2-ones such as Alzheimer's drug Rolipram (11) with the same absolute configuration via tert-butyl group removal and subsequent Barton decarboxylation.
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Affiliation(s)
- Jiguo Ma
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, College of Chemistry and Materials Science, Shanghai Normal University, Shanghai, 200234, China.,State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, China
| | - Qinghai Zhou
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, College of Chemistry and Materials Science, Shanghai Normal University, Shanghai, 200234, China
| | - Guanshui Song
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, College of Chemistry and Materials Science, Shanghai Normal University, Shanghai, 200234, China
| | - Yongchang Song
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, College of Chemistry and Materials Science, Shanghai Normal University, Shanghai, 200234, China
| | - Guoqing Zhao
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, College of Chemistry and Materials Science, Shanghai Normal University, Shanghai, 200234, China
| | - Kuiling Ding
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, China
| | - Baoguo Zhao
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, College of Chemistry and Materials Science, Shanghai Normal University, Shanghai, 200234, China
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36
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Ranga PK, Ahmad F, Nager P, Rana PS, Vijaya Anand R. Bis(amino)cyclopropenium Ion as a Hydrogen-Bond Donor Catalyst for 1,6-Conjugate Addition Reactions. J Org Chem 2021; 86:4994-5010. [PMID: 33721500 DOI: 10.1021/acs.joc.0c02940] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The catalytic application of the bis(amino)cyclopropenium ion has been investigated in conjugate addition reactions. The hydrogen atom, which is attached to the cyclopropene ring of bis(amino)cyclopropenium salts, is moderately acidic and can potentially serve as a hydrogen-bond donor catalyst in some organic transformations. This hypothesis has been successfully realized in the 1,6-conjugate addition reactions of p-quinone methides with various nucleophiles such as indole, 2-naphthol, thiols, phenols, and so forth. The spectroscopic studies (NMR and UV-vis) as well as the deuterium isotope labeling studies clearly revealed that the hydrogen atom (C-H) that is present in the cyclopropene ring of the catalyst is indeed solely responsible for catalyzing these transformations. In addition, these studies also strongly indicate that the C-H hydrogen of the cyclopropene ring activates the carbonyl group of the p-quinone methide through hydrogen bonding.
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Affiliation(s)
- Pavit Kumar Ranga
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Feroz Ahmad
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Prashant Nager
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Prabhat Singh Rana
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
| | - Ramasamy Vijaya Anand
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Knowledge City, Manauli (P.O.), S. A. S. Nagar, Punjab 140306, India
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37
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Guanidine-Amide-Catalyzed Aza-Henry Reaction of Isatin-Derived Ketimines: Origin of Selectivity and New Catalyst Design. Molecules 2021; 26:molecules26071965. [PMID: 33807341 PMCID: PMC8037019 DOI: 10.3390/molecules26071965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/29/2021] [Accepted: 03/29/2021] [Indexed: 12/05/2022] Open
Abstract
Density functional theory (DFT) calculations were performed to investigate the mechanism and the enantioselectivity of the aza-Henry reaction of isatin-derived ketimine catalyzed by chiral guanidine–amide catalysts at the M06-2X-D3/6-311+G(d,p)//M06-2X-D3/6-31G(d,p) (toluene, SMD) theoretical level. The catalytic reaction occurred via a three-step mechanism: (i) the deprotonation of nitromethane by a chiral guanidine–amide catalyst; (ii) formation of C–C bonds; (iii) H-transfer from guanidine to ketimine, accompanied with the regeneration of the catalyst. A dual activation model was proposed, in which the protonated guanidine activated the nitronate, and the amide moiety simultaneously interacted with the ketimine substrate by intermolecular hydrogen bonding. The repulsion of CPh3 group in guanidine as well as N-Boc group in ketimine raised the Pauli repulsion energy (∆EPauli) and the strain energy (∆Estrain) of reacting species in the unfavorable si-face pathway, contributing to a high level of stereoselectivity. A new catalyst with cyclopropenimine and 1,2-diphenylethylcarbamoyl as well as sulfonamide substituent was designed. The strong basicity of cyclopropenimine moiety accelerated the activation of CH3NO2 by decreasing the energy barrier in the deprotonation step. The repulsion between the N-Boc group in ketimine and cyclohexyl group as well as chiral backbone in the new catalyst raised the energy barrier in C–C bond formation along the si-face attack pathway, leading to the formation of R-configuration product. A possible synthetic route for the new catalyst is also suggested.
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38
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Ma J, Zhou Q, Song G, Song Y, Zhao G, Ding K, Zhao B. Enantioselective Synthesis of Pyroglutamic Acid Esters from Glycinate via Carbonyl Catalysis. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202017306] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Jiguo Ma
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials College of Chemistry and Materials Science Shanghai Normal University Shanghai 200234 China
- State Key Laboratory of Organometallic Chemistry Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry Chinese Academy of Sciences 345 Lingling Road Shanghai 200032 China
| | - Qinghai Zhou
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials College of Chemistry and Materials Science Shanghai Normal University Shanghai 200234 China
| | - Guanshui Song
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials College of Chemistry and Materials Science Shanghai Normal University Shanghai 200234 China
| | - Yongchang Song
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials College of Chemistry and Materials Science Shanghai Normal University Shanghai 200234 China
| | - Guoqing Zhao
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials College of Chemistry and Materials Science Shanghai Normal University Shanghai 200234 China
| | - Kuiling Ding
- State Key Laboratory of Organometallic Chemistry Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry Chinese Academy of Sciences 345 Lingling Road Shanghai 200032 China
| | - Baoguo Zhao
- The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials College of Chemistry and Materials Science Shanghai Normal University Shanghai 200234 China
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39
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Trubitsõn D, Martõnova J, Kudrjašova M, Erkman K, Järving I, Kanger T. Enantioselective Organocatalytic Michael Addition to Unsaturated Indolyl Ketones. Org Lett 2021; 23:1820-1824. [PMID: 33625233 DOI: 10.1021/acs.orglett.1c00222] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An efficient enantioselective organocatalytic method for the synthesis of N-alkylated indoles with α-branched alkyl substituents from the corresponding unsaturated indolyl ketones via a Michael addition has been developed. The resulting products were obtained in high enantioselectivities and in good yields. Various nucleophiles (nitroalkanes, malononitrile, malonic esters) can be used. The substitution pattern of the indole ring had no significant impact on the reaction outcome. Both electron-withdrawing and electron-donating substituents in any position of the heteroaromatic ring were well-tolerated.
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Affiliation(s)
- Dmitri Trubitsõn
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Jevgenija Martõnova
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Marina Kudrjašova
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Kristin Erkman
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Ivar Järving
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Tõnis Kanger
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
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40
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Xu J, Xian A, Li Z, Liu J, Zhang Z, Yan R, Gao L, Liu B, Zhao L, Guo K. A Strained Ion Pair Permits Carbon Dioxide Fixation at Atmospheric Pressure by C-H H-Bonding Organocatalysis. J Org Chem 2021; 86:3422-3432. [PMID: 33512164 DOI: 10.1021/acs.joc.0c02790] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cycloadditions of carbon dioxide into epoxides to afford cyclic carbonates by H-bond donor (HBD) and onium halide (X) cocatalysis have emerged as a key strategy for CO2 fixation. However, if the HBD is also a halide receptor, the two will quench each other, decreasing the catalytic activity. Here, we propose a strained ion pair tris(alkylamino)cyclopropenium halide (TAC·X), in which TAC repels X. TAC possesses a positively charged cyclopropenium core that makes the vicinal C-H or N-H a nonclassical HBD. The interionic strain within TAC·X makes TAC a more electrophilic HBD, allowing it to activate the oxygen of the epoxide and making X more nucleophilic and better able to attack the methylene carbon of the epoxide. NMR titration spectra and computational studies were employed to probe the mechanism of the cycloaddition of CO2 to epoxides reactions under the catalysis of TAC·X. The 1H and 13C{1H}NMR titration spectra of the catalyst with the epoxide substrate unambiguously confirmed H-bonding between TAC and the epoxide. DFT computational studies identified the transition states in the ring-opening of the epoxide (TS1) and in the ring-closure of the cyclic carbonate (TS2).
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Affiliation(s)
- Jiaxi Xu
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Anmei Xian
- Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Zhenjiang Li
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Jingjing Liu
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Zhihao Zhang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Rui Yan
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Luoyu Gao
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Bo Liu
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Lili Zhao
- Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
| | - Kai Guo
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, 30 Puzhu Road South, Nanjing, Jiangsu 211816, China
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41
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Das S, Hu Q, Kondoh A, Terada M. Enantioselective Protonation: Hydrophosphinylation of 1,1-Vinyl Azaheterocycle N-Oxides Catalyzed by Chiral Bis(guanidino)iminophosphorane Organosuperbase. Angew Chem Int Ed Engl 2021; 60:1417-1422. [PMID: 33030798 DOI: 10.1002/anie.202012492] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Indexed: 12/30/2022]
Abstract
Enantioselective protonation by hydrophosphinylation of diarylphosphine oxides with 2-vinyl azaheterocycle N-oxide derivatives was demonstrated using chiral bis(guanidino)iminophosphorane as the higher-order organosuperbase catalyst. It was confirmed by several control experiments that a chiral weak conjugate acid of the chiral bis(guanidino)iminophosphorane, instead of achiral diarylphosphine oxides, directly functioned as the proton source to afford the corresponding product in a highly enantioselective manner in most cases. Enantioselective protonation by a weak conjugate acid generated from the higher-order organosuperbase would broaden the scope of enantioselective reaction systems because of utilization of a range of less acidic pronucleophiles. This method is highlighted by the valuable synthesis of a series of chiral P,N-ligands for chiral metal complexes through the reduction of phosphine oxide and N-oxide units of the corresponding product without loss of enantiomeric purity.
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Affiliation(s)
- Saikat Das
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Qiupeng Hu
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Azusa Kondoh
- Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Masahiro Terada
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
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42
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Kondoh A, Terada M. Development of Molecular Transformations on the Basis of Catalytic Generation of Anionic Species by Organosuperbase. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20200308] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Azusa Kondoh
- Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Masahiro Terada
- Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, Miyagi 980-8578, Japan
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43
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Das S, Hu Q, Kondoh A, Terada M. Enantioselective Protonation: Hydrophosphinylation of 1,1‐Vinyl Azaheterocycle
N
‐Oxides Catalyzed by Chiral Bis(guanidino)iminophosphorane Organosuperbase. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202012492] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Saikat Das
- Department of Chemistry Graduate School of Science Tohoku University Aramaki, Aoba-ku Sendai 980-8578 Japan
| | - Qiupeng Hu
- Department of Chemistry Graduate School of Science Tohoku University Aramaki, Aoba-ku Sendai 980-8578 Japan
| | - Azusa Kondoh
- Research and Analytical Center for Giant Molecules Graduate School of Science Tohoku University Aramaki, Aoba-ku Sendai 980-8578 Japan
| | - Masahiro Terada
- Department of Chemistry Graduate School of Science Tohoku University Aramaki, Aoba-ku Sendai 980-8578 Japan
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44
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Guest M, Mir R, Foran G, Hickson B, Necakov A, Dudding T. Trisaminocyclopropenium Cations as Small-Molecule Organic Fluorophores: Design Guidelines and Bioimaging Applications. J Org Chem 2020; 85:13997-14011. [PMID: 32930593 DOI: 10.1021/acs.joc.0c02026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The discovery of fluorescence two centuries ago ushered in, what is today, an illuminating field of science rooted in the rational design of photochromic molecules for task-specific bio-, material-, and medical-driven applications. Today, this includes applications in bioimaging and diagnosis, photodynamic therapy regimes, in addition to photovoltaic devices and solar cells, among a vast multitude of other usages. In furthering this indispensable area of daily life and modern-day scientific research, we report herein the synthesis of a class of trisaminocyclopropenium fluorophores along with a systematic investigation of their unique molecular and electronic dependent photophysical properties. Among these fluorophores, tris[N(naphthalen-2-ylmethyl)phenylamino] cyclopropenium chloride (TNTPC) displayed a strong photophysical profile including a 0.92 quantum yield ascribed to intramolecular charge transfer and intramolecular through-space conjugation. Moreover, this cyclopropenium-based fluorophore functions as a competent imaging agent for DNA visualization and nuclear counterstaining in cell culture. To facilitate the broader use of these compounds, design principles supported by density functional theory calculations for engineering analogs of this class of fluorophores are offered. Collectively, this study adds to the burgeoning interest in cyclopropenium compounds and their unique properties as fluorophores with uses in bioimaging applications.
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Affiliation(s)
- Matt Guest
- Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Roya Mir
- Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Gregory Foran
- Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Brianne Hickson
- Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Aleksandar Necakov
- Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Travis Dudding
- Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
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Formica M, Rozsar D, Su G, Farley AJM, Dixon DJ. Bifunctional Iminophosphorane Superbase Catalysis: Applications in Organic Synthesis. Acc Chem Res 2020; 53:2235-2247. [PMID: 32886474 DOI: 10.1021/acs.accounts.0c00369] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To improve the field of catalysis, there is a substantial and growing need for novel high-performance catalysts providing new reactivity. To date, however, the set of reactions that can be reliably performed to prepare chiral compounds in largely one enantiomeric form using chiral catalysts still represents a small fraction of the toolkit of known transformations. In this context, chiral Brønsted bases have played an expanding role in catalyzing enantioselective reactions between various carbon- and heteroatom-centered acids and a host of electrophilic reagents. This Account describes our recent efforts developing and applying a new family of chiral Brønsted bases incorporating an H-bond donor moiety and a strongly basic iminophosphorane, which we have named BIMPs (Bifunctional IMinoPhosphoranes), as efficient catalysts for reactions currently out of reach of more widespread tertiary amine centered bifunctional catalysts. The iminophosphorane Brønsted base is easily generated by the Staudinger reaction of a chiral organoazide and commercially available phosphine, which allows easy modification of the catalyst structure and fine-tuning of the iminophosphorane pKBH+. We have demonstrated that BIMP catalysts can efficiently promote the enantioselective addition of nitromethane to low reactivity N-diphenylphosphinoyl (DPP)-protected imines of ketones (ketimines) to access valuable chiral diamine and α-quaternary amino acid building blocks, and later extended this methodology to phosphite nucleophiles. Subsequently, the reaction scope was expanded to include the Michael addition of high pKa alkyl thiols to α-substituted acrylate esters, β-substituted α,β-unsaturated esters, and alkenyl benzimidazoles as well as the challenging direct aldol addition of aryl ketones to α-fluorinated ketones. Finally, BIMP catalysts were shown to be used in key steps in the synthesis of complex alkaloid natural products (-)-nakadomarin A and (-)-himalensine A, as well as in polymer synthesis. In most cases, the predictable nature of the BIMP promoted reactions was demonstrated by multigram scale-up while employing low catalyst loadings (down to 0.05 mol%). Furthermore, it was shown that BIMP catalysts can be easily immobilized onto a solid support in one-step for increased catalyst recycling and flow chemistry applications. Alongside our own work, this Account also includes elegant work by Johnson and co-workers utilizing the BIMP catalyst system, when alternative catalysts proved suboptimal.
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Affiliation(s)
- Michele Formica
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Daniel Rozsar
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Guanglong Su
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Alistair J. M. Farley
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
| | - Darren J. Dixon
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, OX1 3TA Oxford, United Kingdom
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Saadat K, Shiri A, Kovačević B. Step Forward to Stronger Neutral Organic Superbases: Fused Troponimines. J Org Chem 2020; 85:11375-11381. [DOI: 10.1021/acs.joc.0c01466] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kayvan Saadat
- Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, 91775-1436 Mashhad, Iran
| | - Ali Shiri
- Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, 91775-1436 Mashhad, Iran
| | - Borislav Kovačević
- Group for Computational Life Science, Division of Chemistry, Ruder Boskovic Institute, Bijenicka 54, 10000 Zagreb, Croatia
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48
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Guest M, Le Sueur R, Pilkington M, Dudding T. Development of an Unsymmetrical Cyclopropenimine-Guanidine Platform for Accessing Strongly Basic Proton Sponges and Boron-Difluoride Diaminonaphthalene Fluorophores. Chemistry 2020; 26:8608-8620. [PMID: 32319110 DOI: 10.1002/chem.202001227] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 04/18/2020] [Indexed: 01/06/2023]
Abstract
An unsymmetrical guanidine-cyclopropenimine proton sponge DAGUN and the related BF2 -chelate DAGBO are reported. Insight into the structural, electronic, bonding and photophysical properties of these two molecules are presented. Joint experimental and theoretical studies reveal the protonated form of DAGUN possesses an intramolecular N⋅⋅⋅H-N hydrogen bond which affords a high experimental pKBH+ of 26.6 (computed=26.3). Photophysical studies show that in solution DAGUN displays a green emission at 534 nm, with a large Stokes shift of 235 nm (14,718 cm-1 ). In contrast, the conjugate acid DAGUN-H+ is only weakly emissive due to attenuated intramolecular charge transfer. X-ray diffraction studies reveal that DAGBO contains a stable tetracoordinate boronium cation, reminiscent of the well-established BODIPY family of dyes. In solution, DAGBO exhibits a strong blue emission at 450 nm coupled with a large Stokes shift (Δλ=158 nm, Δν=11,957 cm-1 ) and quantum yield of 62 %, upon excitation at 293 nm. DAGBO sets the stage as the first entry into a new class of boron-difluoride diaminonaphthalenes (BOFDANs) that represent highly fluorescent and tunable next-generation dyes with future promise for biosensing and bioimaging applications.
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Affiliation(s)
- Matt Guest
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
| | - Richard Le Sueur
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
| | - Melanie Pilkington
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
| | - Travis Dudding
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, ON, L2S 3A1, Canada
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Harnessing aromaticity and intramolecular hydrogen bonding to tailor organosuperbases by using 2,4,6-cycloheptatriene-1-imine scaffold. Struct Chem 2020. [DOI: 10.1007/s11224-020-01520-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Kondoh A, Oishi M, Tezuka H, Terada M. Development of Chiral Organosuperbase Catalysts Consisting of Two Different Organobase Functionalities. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202001419] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Azusa Kondoh
- Research and Analytical Center for Giant MoleculesGraduate School of ScienceTohoku University, Aramaki, Aoba-ku Sendai 980–8578 Japan
| | - Masafumi Oishi
- Department of ChemistryGraduate School of ScienceTohoku University, Aramaki, Aoba-ku Sendai 980–8578 Japan
| | - Hikaru Tezuka
- Department of ChemistryGraduate School of ScienceTohoku University, Aramaki, Aoba-ku Sendai 980–8578 Japan
| | - Masahiro Terada
- Department of ChemistryGraduate School of ScienceTohoku University, Aramaki, Aoba-ku Sendai 980–8578 Japan
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