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Martins FA, Chagas P, Thomasi SS, Oliveira LCA, Diniz R, Freitas MP. Theoretical and X-ray evidence of electrostatic phosphonium anti and gauche effects. Chemphyschem 2022; 23:e202100856. [PMID: 34995018 DOI: 10.1002/cphc.202100856] [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: 12/01/2021] [Revised: 12/21/2021] [Indexed: 11/12/2022]
Abstract
Sulfur, not phosphorus, is the only known third-row element capable of experiencing an electrostatic gauche effect with fluorine. Some six-membered rings containing an endocyclic phosphorus atom and a β-fluorine substituent that can interconvert to axial ( gauche relative to phosphorus) and equatorial positions were then analysed. While phosphines do not establish an electrostatic attraction between fluorine and phosphorus, some oxidised forms exhibit surprising stability for the sterically disfavoured axial orientation. Because the nature of this behaviour was not obvious, since an intramolecular hydrogen bond can appear, a phosphonium derivative was further studied and its axial conformation was found to be highly stable. A preference for the gauche arrangement appears even for the acyclic and sterically hindered (2-fluoroethyl)triphenylphosphonium cation. On the other hand, (ethane-1,2-diyl)bis(phosphonium) cations are exclusively in anti conformation due to an (+/+)-electrostatic repulsion between the positively charged phosphonium groups.
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Affiliation(s)
- Francisco A Martins
- Federal University of Lavras: Universidade Federal de Lavras, Chemistry, Av. Lagoa Azul, Casa, Lavras, 37200-900, Lavras, BRAZIL
| | | | - Sérgio S Thomasi
- Federal University of Lavras: Universidade Federal de Lavras, Chemistry, BRAZIL
| | | | - Renata Diniz
- Universidade Federal de Minas Gerais, Chemistry, BRAZIL
| | - Matheus P Freitas
- Federal University of Lavras, Department of Chemsitry, Campus UFLA, CP 3037, 37200-000, Lavras, BRAZIL
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2
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Mondal R, Agbaria M, Nairoukh Z. Fluorinated Rings: Conformation and Application. Chemistry 2021; 27:7193-7213. [PMID: 33512034 DOI: 10.1002/chem.202005425] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Indexed: 12/16/2022]
Abstract
The introduction of fluorine atoms into molecules and materials across many fields of academic and industrial research is now commonplace, owing to their unique properties. A particularly interesting feature is the impact of fluorine substitution on the relative orientation of a C-F bond when incorporated into organic molecules. In this Review, we will be discussing the conformational behavior of fluorinated aliphatic carbo- and heterocyclic systems. The conformational preference of each system is associated with various interactions introduced by fluorine substitution such as charge-dipole, dipole-dipole, and hyperconjugative interactions. The contribution of each interaction on the stabilization of the fluorinated alicyclic system, which manifests itself in low conformations, will be discussed in detail. The novelty of this feature will be demonstrated by presenting the most recent applications.
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Affiliation(s)
- Rajarshi Mondal
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Mohamed Agbaria
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Zackaria Nairoukh
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
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3
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Scattolin T, Bortolamiol E, Caligiuri I, Rizzolio F, Demitri N, Visentin F. Synthesis and comparative study of the anticancer activity of η3-allyl palladium(II) complexes bearing N-heterocyclic carbenes as ancillary ligands. Polyhedron 2020. [DOI: 10.1016/j.poly.2020.114607] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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4
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Silva DR, Zeoly LA, Cormanich RA, Guerra CF, Freitas MP. Evaluation of the Alicyclic Gauche
Effect in 2-Fluorocyclohexanone Analogs: a Combined NMR and DFT Study. European J Org Chem 2020. [DOI: 10.1002/ejoc.201901815] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Daniela Rodrigues Silva
- Departamento de Química; Universidade Federal de Lavras; 37200-900 Lavras - MG Brazil
- Theoretical Chemistry; Department of Chemistry and Pharmaceutical Sciences; AIMMS, Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
| | - Lucas A. Zeoly
- Chemistry Institute; University of Campinas; 13083- 970 Campinas - SP Brazil
| | | | - Célia Fonseca Guerra
- Theoretical Chemistry; Department of Chemistry and Pharmaceutical Sciences; AIMMS, Vrije Universiteit Amsterdam; De Boelelaan 1083 1081 HV Amsterdam The Netherlands
- Leiden Institute of Chemistry; Gorlaeus Laboratories; Leiden University; Einsteinweg 55 2333 CC Leiden The Netherlands
| | - Matheus P. Freitas
- Departamento de Química; Universidade Federal de Lavras; 37200-900 Lavras - MG Brazil
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Selg C, Kraft FB, Welcke L, Zeitler K. A Catalytic Strategy for α,ω‐Functionalization: NHC‐Mediated Fragmentation/Umpolung Cascades to Access Hydroxytrifluoromethyl Ynones and Allenones. ChemCatChem 2018. [DOI: 10.1002/cctc.201801454] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Christoph Selg
- Institut für Organische ChemieUniversität Leipzig Johannisallee 29 04103 Leipzig Germany
| | - Fabian B. Kraft
- Institut für Organische ChemieUniversität Leipzig Johannisallee 29 04103 Leipzig Germany
| | - Linda Welcke
- Institut für Organische ChemieUniversität Leipzig Johannisallee 29 04103 Leipzig Germany
| | - Kirsten Zeitler
- Institut für Organische ChemieUniversität Leipzig Johannisallee 29 04103 Leipzig Germany
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Onar G, Karataş MO, Balcıoğlu S, Tok TT, Gürses C, Kılıç-Cıkla I, Özdemir N, Ateş B, Alıcı B. Benzotriazole functionalized N-heterocyclic carbene–silver(I) complexes: Synthesis, cytotoxicity, antimicrobial, DNA binding, and molecular docking studies. Polyhedron 2018. [DOI: 10.1016/j.poly.2018.06.052] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Aufiero M, Gilmour R. Informing Molecular Design by Stereoelectronic Theory: The Fluorine Gauche Effect in Catalysis. Acc Chem Res 2018; 51:1701-1710. [PMID: 29894155 DOI: 10.1021/acs.accounts.8b00192] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The axioms of stereoelectronic theory constitute an atlas to navigate the contours of molecular space. All too rarely lauded, the advent and development of stereoelectronic theory has been one of organic chemistry's greatest triumphs. Inevitably, however, in the absence of a comprehensive treatise, many of the field's pioneers do not receive the veneration that they merit. Rather their legacies are the stereoelectronic pillars that persist in teaching and research. This ubiquity continues to afford practitioners of organic chemistry with an abundance of opportunities for creative endeavor in reaction design, in conceiving novel activation modes, in preorganizing intermediates, or in stabilizing productive transition states and products. Antipodal to steric governance, which mitigates destabilizing nonbonding interactions, stereoelectronic control allows well-defined, often complementary, conformations to be populated. Indeed, the prevalence of stabilizing hyperconjugative interactions in biosynthetic processes renders this approach to molecular preorganization decidedly biomimetic and, by extension, expansive. In this Account, the evolution and application of a simple donor-acceptor model based on the fluorine gauche effect is delineated. Founded on reinforcing hyperconjugative interactions involving C(sp3)-H bonding orbitals and C(sp3)-X antibonding orbitals [σC-H → σC-X*], this general stratagem has been used in conjunction with an array of secondary noncovalent interactions to achieve acyclic conformational control (ACC) in structures of interest. These secondary effects range from 1,3-allylic strain (A1,3) through to electrostatic charge-dipole and cation-π interactions. Synergy between these interactions ensures that rotation about strategic C(sp3)-C(sp3) bonds is subject to the stereoelectronic requirement for antiperiplanarity (180°). Logically, in a generic [X-CH2-CH2-Y] system (X, Y = electron withdrawing groups) conformations in which the two C(sp3)-X bonds are synclinal (i.e., gauche) are significantly populated. As such, simple donor-acceptor models are didactically and predictively powerful in achieving topological preorganization. In the case of the gauche effect, the low steric demand of fluorine ensures that the remaining substituents at the C(sp3) hybridized center are placed in a predictable area of molecular space: An exit vector analogy is thus appropriate. Furthermore, the intrinsic chemical stability of the C-F bond is advantageous, thus it may be considered as an inert conformational steering group: This juxtaposition of size and electronegativity renders fluorinated organic molecules unique among the organo-halogen series. Cognizant that the replacement of one fluorine atom in the difluoroethylene motif by another electron withdrawing group preserves the gauche conformation, it was reasoned that β-fluoroamines would be intriguing candidates for investigation. The burgeoning field of Lewis base catalysis, particularly via iminium ion activation, provided a timely platform from which to explore a postulated fluorine-iminium ion gauche effect. Necessarily, activation of this stereoelectronic effect requires a process of intramolecularization to generate the electron deficient neighboring group: Examples include protonation, condensation to generate iminium salts, or acylation. This process, akin to substrate binding, has obvious parallels with enzymatic catalysis, since it perturbs the conformational dynamics of the system [ synclinal-endo, antiperiplanar, synclinal-exo]. This Account details the development of conformationally predictable small molecules based on the [X-Cα-Cβ-F] motif through a logical process of molecular design and illustrates their synthetic value in enantioselective catalysis.
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Affiliation(s)
- Marialuisa Aufiero
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Ryan Gilmour
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
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Teschers CS, Daniliuc CG, Kehr G, Gilmour R. Conformational control enabled by the fluorine gauche effect in a model of the β2-AR agonist salbutamol (Ventolin™). J Fluor Chem 2018. [DOI: 10.1016/j.jfluchem.2018.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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9
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Zr-mediated synthesis of chiral cyclic imines and their application in Betti reactions. Chem Heterocycl Compd (N Y) 2018. [DOI: 10.1007/s10593-018-2268-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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10
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Price GA, Brisdon AK, Randall S, Lewis E, Whittaker DM, Pritchard RG, Muryn CA, Flower KR, Quayle P. Some insights into the gold-catalysed A 3 -coupling reaction. J Organomet Chem 2017. [DOI: 10.1016/j.jorganchem.2017.06.019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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11
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Coinage Metal Complexes of the Carbenic Tautomer of a Conjugated Mesomeric Betaine Akin to Nitron. Molecules 2017; 22:molecules22071133. [PMID: 28686202 PMCID: PMC6152182 DOI: 10.3390/molecules22071133] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 07/06/2017] [Accepted: 07/06/2017] [Indexed: 01/25/2023] Open
Abstract
This study was motivated by our recent observation that the analytical reagent Nitron (2) is an “instant carbene”, whose reaction with coinage metal salts MX afforded complexes of its carbenic tautomer 1,4-diphenyl-3-phenylamino-1,2,4-triazol-5-ylidene (2′). Our aim was to establish an alkyl homologue of 2 in order to achieve a carbenic tautomer of higher donicity. For this purpose 1-tert-butyl-4-methyl-1,2,4-triazol-4-ium-3-tert-butylaminide (6) was synthesized. Its reactions with MX afforded complexes of the carbenic tautomer 1-tert-butyl-3-tert-butylamino-4-methyl-1,2,4-triazol-5-ylidene (6′). With a stoichiometric ratio of 1:1 complexes of the type [MX(6′)] were obtained. A ratio of 2:1 furnished complexes of the type [MX(6′)2] or [M(6′)2]X. 6′ is a better σ-donor and less electrophilic than 2′ according to NMR spectroscopic data of 6H[BF4] and 6′ = Se, respectively, and IR spectroscopic data of [RhCl(6′)(CO)2] confirm that its net electron donor capacity is superior to that of 2′. A comparison of the complexes of 2′ and 6′ reveals two pronounced structural differences. [CuX(6′)2] (X = Cl, Br) exhibit more acute C–Cu–C bond angles than [CuX(2′)2]. In contrast to [CuCl(2′)], [CuCl(6′)] aggregates through Cu···Cu contacts of ca. 2.87 Å, compatible with cuprophilic interactions. These differences may be explained by the complementary steric requirements of the t-Bu and the Me substituent of 6′.
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12
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Gibard C, Fauché K, Guillot R, Jouffret L, Traïkia M, Gautier A, Cisnetti F. Access to silver-NHC complexes from soluble silver species in aqueous or ethanolic ammonia. J Organomet Chem 2017. [DOI: 10.1016/j.jorganchem.2017.04.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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13
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Affiliation(s)
- Christian Thiehoff
- Institute for Organic Chemistry; Westfälische Wilhelms-Universität Münster; Corrensstr. 40 48149 Münster Germany
| | - Yannick P. Rey
- Institute for Organic Chemistry; Westfälische Wilhelms-Universität Münster; Corrensstr. 40 48149 Münster Germany
| | - Ryan Gilmour
- Institute for Organic Chemistry; Westfälische Wilhelms-Universität Münster; Corrensstr. 40 48149 Münster Germany
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14
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Le Guen C, Tran Do ML, Chardon A, Lebargy C, Lohier JF, Pfund E, Lequeux T. Access to Fluoropyrrolidines by Intramolecular Aza-Michael Addition Reaction. J Org Chem 2016; 81:6714-20. [DOI: 10.1021/acs.joc.6b01363] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Clothilde Le Guen
- Normandie University, LCMT, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France
| | - Minh-Loan Tran Do
- Normandie University, LCMT, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France
| | - Aurélien Chardon
- Normandie University, LCMT, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France
| | - Cyril Lebargy
- Normandie University, LCMT, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France
| | | | - Emmanuel Pfund
- Normandie University, LCMT, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France
| | - Thierry Lequeux
- Normandie University, LCMT, ENSICAEN, UNICAEN, CNRS, 14000 Caen, France
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16
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Wang X, Wu Z, Wang J. α-Fluoroallenoate Synthesis via N-Heterocyclic Carbene-Catalyzed Fluorination Reaction of Alkynals. Org Lett 2016; 18:576-9. [DOI: 10.1021/acs.orglett.5b03615] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xu Wang
- Department of Pharmacology and
Pharmaceutical Science, School of Medicine, Tsinghua University, Beijing 117543, China
| | - Zijun Wu
- Department of Pharmacology and
Pharmaceutical Science, School of Medicine, Tsinghua University, Beijing 117543, China
| | - Jian Wang
- Department of Pharmacology and
Pharmaceutical Science, School of Medicine, Tsinghua University, Beijing 117543, China
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Hollóczki O, Macchiagodena M, Weber H, Thomas M, Brehm M, Stark A, Russina O, Triolo A, Kirchner B. Triphilic Ionic-Liquid Mixtures: Fluorinated and Non-fluorinated Aprotic Ionic-Liquid Mixtures. Chemphyschem 2015; 16:3325-33. [PMID: 26305804 PMCID: PMC4641458 DOI: 10.1002/cphc.201500473] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 07/16/2015] [Indexed: 11/20/2022]
Abstract
We present here the possibility of forming triphilic mixtures from alkyl- and fluoroalkylimidazolium ionic liquids, thus, macroscopically homogeneous mixtures for which instead of the often observed two domains-polar and nonpolar-three stable microphases are present: polar, lipophilic, and fluorous ones. The fluorinated side chains of the cations indeed self-associate and form domains that are segregated from those of the polar and alkyl domains. To enable miscibility, despite the generally preferred macroscopic separation between fluorous and alkyl moieties, the importance of strong hydrogen bonding is shown. As the long-range structure in the alkyl and fluoroalkyl domains is dependent on the composition of the liquid, we propose that the heterogeneous, triphilic structure can be easily tuned by the molar ratio of the components. We believe that further development may allow the design of switchable, smart liquids that change their properties in a predictable way according to their composition or even their environment.
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Affiliation(s)
- Oldamur Hollóczki
- Mulliken Center for Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität BonnBeringstr. 4+6, 53115, Bonn (Germany) E-mail:
| | - Marina Macchiagodena
- Mulliken Center for Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität BonnBeringstr. 4+6, 53115, Bonn (Germany) E-mail:
| | - Henry Weber
- Mulliken Center for Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität BonnBeringstr. 4+6, 53115, Bonn (Germany) E-mail:
| | - Martin Thomas
- Mulliken Center for Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität BonnBeringstr. 4+6, 53115, Bonn (Germany) E-mail:
| | - Martin Brehm
- Helmholtz-Zentrum für Umweltforschung Leipzig, Department Ökologische ChemiePermoserstrasse 15, 04318, Leipzig (Germany)
| | - Annegret Stark
- SMRI Sugarcane Biorefinery Research Chair, University of KwaZulu-Natal, College of Agriculture, Engineering and Science School of EngineeringHoward College Campus, Durban (South Africa)
| | - Olga Russina
- Department of Chemistry, Sapienza University of Rome00185, Rome (Italy)
| | - Alessandro Triolo
- Laboratorio Liquidi Ionici, Istituto Struttura della Materia, Consiglio Nazionale delle Ricerche00133, Rome (Italy)
| | - Barbara Kirchner
- Mulliken Center for Theoretical Chemistry, Rheinische Friedrich-Wilhelms-Universität BonnBeringstr. 4+6, 53115, Bonn (Germany) E-mail:
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Aleksić J, Stojanović M, Baranac-Stojanović M. Origin of Fluorine/Sulfur Gauche Effect of β-Fluorinated Thiol, Sulfoxide, Sulfone, and Thionium Ion. J Org Chem 2015; 80:10197-207. [DOI: 10.1021/acs.joc.5b01779] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Jovana Aleksić
- Center
for Chemistry ICTM, University of Belgrade, P.O. Box 473, 11000 Belgrade, Serbia
| | - Milovan Stojanović
- Center
for Chemistry ICTM, University of Belgrade, P.O. Box 473, 11000 Belgrade, Serbia
| | - Marija Baranac-Stojanović
- Faculty
of Chemistry, University of Belgrade, Studentski trg 12-16, P.O. Box 158, 11000 Belgrade, Serbia
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Thiehoff C, Holland MC, Daniliuc C, Houk KN, Gilmour R. Can acyclic conformational control be achieved via a sulfur-fluorine gauche effect? Chem Sci 2015; 6:3565-3571. [PMID: 29511517 PMCID: PMC5659174 DOI: 10.1039/c5sc00871a] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 04/16/2015] [Indexed: 01/04/2023] Open
Abstract
The gauche conformation of the 1,2-difluoroethane motif is known to involve stabilising hyperconjugative interactions between donor (bonding, σC-H) and acceptor (antibonding, σ*C-F) orbitals. This model rationalises the generic conformational preference of F-Cβ-Cα-X systems (φFCCX ≈ 60°), where X is an electron deficient substituent containing a Period 2 atom. Little is known about the corresponding Period 3 systems, such as sulfur and phosphorus, where multiple oxidation states are possible. Conformational analyses of β-fluorosulfides, -sulfoxides and -sulfones are disclosed here, thus extending the scope of the fluorine gauche effect to the 3rd Period (F-C-C-S(O) n ; φFCCS ≈ 60°). Synergy between experiment and computation has revealed that the gauche effect is only pronounced in structures bearing an electropositive vicinal sulfur atom (S+-O-, SO2).
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Affiliation(s)
- C Thiehoff
- Organisch Chemisches Institut, and Excellence Cluster EXC 1003 , Cells in Motion , Westfälische Wilhelms-Universität Münster , Corrensstrasse 40 , Münster , Germany .
| | - M C Holland
- Organisch Chemisches Institut, and Excellence Cluster EXC 1003 , Cells in Motion , Westfälische Wilhelms-Universität Münster , Corrensstrasse 40 , Münster , Germany .
- Department of Chemistry and Biochemistry , University of California Los Angeles , 607 Charles E. Young Drive East , Los Angeles 90095-1569 , USA .
| | - C Daniliuc
- Organisch Chemisches Institut, and Excellence Cluster EXC 1003 , Cells in Motion , Westfälische Wilhelms-Universität Münster , Corrensstrasse 40 , Münster , Germany .
| | - K N Houk
- Department of Chemistry and Biochemistry , University of California Los Angeles , 607 Charles E. Young Drive East , Los Angeles 90095-1569 , USA .
| | - R Gilmour
- Organisch Chemisches Institut, and Excellence Cluster EXC 1003 , Cells in Motion , Westfälische Wilhelms-Universität Münster , Corrensstrasse 40 , Münster , Germany .
- Excellence Cluster EXC 1003 , Cells in Motion , Westfälische Wilhelms-Universität Münster , Münster , Germany
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Turek J, Růžičková Z, Růžička A. Structural diversity of two 1,2,4-triazole based N -heterocyclic carbene complexes of silver(I). INORG CHEM COMMUN 2014. [DOI: 10.1016/j.inoche.2014.08.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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21
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Rey YP, Gilmour R. Modulating NHC catalysis with fluorine. Beilstein J Org Chem 2013; 9:2812-20. [PMID: 24367445 PMCID: PMC3869272 DOI: 10.3762/bjoc.9.316] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/08/2013] [Indexed: 11/23/2022] Open
Abstract
Fluorination often confers a range of advantages in modulating the conformation and reactivity of small molecule organocatalysts. By strategically introducing fluorine substituents, as part of a β-fluoroamine motif, in a triazolium pre-catalyst, it was possible to modulate the behaviour of the corresponding N-heterocyclic carbene (NHC) with minimal steric alterations to the catalyst core. In this study, the effect of hydrogen to fluorine substitution was evaluated as part of a molecular editing study. X-ray crystallographic analyses of a number of derivatives are presented and the conformations are discussed. Upon deprotonation, the fluorinated triazolium salts generate catalytically active N-heterocyclic carbenes, which can then participate in the enantioselective Steglich rearrangement of oxazolyl carbonates to C-carboxyazlactones (e.r. up to 87.0:13.0).
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Affiliation(s)
- Yannick P Rey
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
- Department of Chemistry and Applied Biosciences, ETH Zürich, Wolfgang-Pauli-Str. 10, 8093 Zürich, Switzerland
| | - Ryan Gilmour
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
- Excellence Cluster EXC 1003, Cells in Motion, Münster, Germany
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