1
|
Jansen-van Vuuren RD, Liu S, Miah MAJ, Cerkovnik J, Košmrlj J, Snieckus V. The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update. Chem Rev 2024; 124:7731-7828. [PMID: 38864673 PMCID: PMC11212060 DOI: 10.1021/acs.chemrev.3c00923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 04/26/2024] [Accepted: 05/08/2024] [Indexed: 06/13/2024]
Abstract
The aryl O-carbamate (ArOAm) group is among the strongest of the directed metalation groups (DMGs) in directed ortho metalation (DoM) chemistry, especially in the form Ar-OCONEt2. Since the last comprehensive review of metalation chemistry involving ArOAms (published more than 30 years ago), the field has expanded significantly. For example, it now encompasses new substrates, solvent systems, and metalating agents, while conditions have been developed enabling metalation of ArOAm to be conducted in a green and sustainable manner. The ArOAm group has also proven to be effective in the anionic ortho-Fries (AoF) rearrangement, Directed remote metalation (DreM), iterative DoM sequences, and DoM-halogen dance (HalD) synthetic strategies and has been transformed into a diverse range of functionalities and coupled with various groups through a range of cross-coupling (CC) strategies. Of ultimate value, the ArOAm group has demonstrated utility in the synthesis of a diverse range of bioactive and polycyclic aromatic compounds for various applications.
Collapse
Affiliation(s)
- Ross D. Jansen-van Vuuren
- Department
of Chemistry, Queen’s University, Chernoff Hall, 9 Bader Lane, Kingston, Ontario K7K 2N1, Canada
- Faculty
of Chemistry and Chemical Technology, University
of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia
| | - Susana Liu
- Department
of Chemistry, Queen’s University, Chernoff Hall, 9 Bader Lane, Kingston, Ontario K7K 2N1, Canada
| | - M. A. Jalil Miah
- Department
of Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh
| | - Janez Cerkovnik
- Faculty
of Chemistry and Chemical Technology, University
of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia
| | - Janez Košmrlj
- Faculty
of Chemistry and Chemical Technology, University
of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia
| | - Victor Snieckus
- Department
of Chemistry, Queen’s University, Chernoff Hall, 9 Bader Lane, Kingston, Ontario K7K 2N1, Canada
| |
Collapse
|
2
|
Ermolovich Y, Barysevich MV, Adamson J, Rogova O, Kaabel S, Järving I, Gathergood N, Snieckus V, Kananovich DG. Site-Selective and Stereoselective C-H Functionalization of N-Cyclopropylamides via a Directed Remote Metalation Strategy. Org Lett 2019; 21:969-973. [PMID: 30715898 DOI: 10.1021/acs.orglett.8b03955] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A new methodology for site-selective and stereoselective C-H functionalization of aminocyclopropanes via directed remote lithiation has been developed. Treatment of N-directing group (DG = pivaloyl, tetramethylsuccinimidoyl) arylcyclopropanes with t-BuLi results in a clean β-lithiation and, following quench with electrophiles, leads to a range of cyclopropane derivatives. Sequential double lithiation-methylation to give a dimethylated cyclopropane has been achieved. X-ray, NMR, and computational studies allow rationalization of syn-DG β-deprotonation selectivity via a DG-lithium base coordinated complex.
Collapse
Affiliation(s)
- Yuri Ermolovich
- Department of Chemistry and Biotechnology, School of Science , Tallinn University of Technology , Tallinn 12618 , Estonia.,Department of Drug Design and Pharmacology , University of Copenhagen , DK-2100 Copenhagen , Denmark
| | - Maryia V Barysevich
- Department of Chemistry and Biotechnology, School of Science , Tallinn University of Technology , Tallinn 12618 , Estonia.,Laboratory of Steroids, Institute of Bioorganic Chemistry , National Academy of Sciences of Belarus , Minsk 220141 , Belarus
| | - Jasper Adamson
- National Institute of Chemical Physics and Biophysics , Tallinn 12618 , Estonia
| | - Oksana Rogova
- Department of Drug Design and Pharmacology , University of Copenhagen , DK-2100 Copenhagen , Denmark
| | - Sandra Kaabel
- Department of Chemistry and Biotechnology, School of Science , Tallinn University of Technology , Tallinn 12618 , Estonia
| | - Ivar Järving
- Department of Chemistry and Biotechnology, School of Science , Tallinn University of Technology , Tallinn 12618 , Estonia
| | - Nicholas Gathergood
- Department of Chemistry and Biotechnology, School of Science , Tallinn University of Technology , Tallinn 12618 , Estonia
| | - Victor Snieckus
- Department of Chemistry , Queen's University , Kingston , ON K7L 3N6 , Canada
| | - Dzmitry G Kananovich
- Department of Chemistry and Biotechnology, School of Science , Tallinn University of Technology , Tallinn 12618 , Estonia
| |
Collapse
|
3
|
Noroozi Pesyan N, Rashidnejad H. Decades of synthesis and application of spiro cyclopropanes. JOURNAL OF THE IRANIAN CHEMICAL SOCIETY 2017. [DOI: 10.1007/s13738-017-1086-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
4
|
Úr G, Kálai T, Hideg K. Facile syntheses of 3,4-disubstituted pyrroline nitroxides and their further synthetic applications. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.01.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|
5
|
Strueben J, Lipfert M, Springer JO, Gould CA, Gates PJ, Sönnichsen FD, Staubitz A. High-yield lithiation of azobenzenes by tin-lithium exchange. Chemistry 2015; 21:11165-73. [PMID: 26118826 DOI: 10.1002/chem.201500003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Indexed: 11/05/2022]
Abstract
The lithiation of halogenated azobenzenes by halogen-lithium exchange commonly leads to substantial degradation of the azo group to give hydrazine derivatives besides the desired aryl lithium species. Yields of quenching reactions with electrophiles are therefore low. This work shows that a transmetalation reaction of easily accessible stannylated azobenzenes with methyllithium leads to a near-quantitative lithiation of azobenzenes in para, meta, and ortho positions. To investigate the scope of the reaction, various lithiated azobenzenes were quenched with a variety of electrophiles. Furthermore, mechanistic (119) Sn NMR spectroscopic studies on the formation of lithiated azobenzenes are presented. A tin ate complex of the azobenzene was detected and characterized at low temperature.
Collapse
Affiliation(s)
- Jan Strueben
- Otto-Diels-Institute for Organic Chemistry, University of Kiel, Otto-Hahn-Platz 3-4, 24098 Kiel (Germany)
| | - Matthias Lipfert
- Otto-Diels-Institute for Organic Chemistry, University of Kiel, Otto-Hahn-Platz 3-4, 24098 Kiel (Germany)
| | - Jan-Ole Springer
- Otto-Diels-Institute for Organic Chemistry, University of Kiel, Otto-Hahn-Platz 3-4, 24098 Kiel (Germany)
| | - Colin A Gould
- Otto-Diels-Institute for Organic Chemistry, University of Kiel, Otto-Hahn-Platz 3-4, 24098 Kiel (Germany)
| | - Paul J Gates
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS7 1TS (UK)
| | - Frank D Sönnichsen
- Otto-Diels-Institute for Organic Chemistry, University of Kiel, Otto-Hahn-Platz 3-4, 24098 Kiel (Germany)
| | - Anne Staubitz
- Otto-Diels-Institute for Organic Chemistry, University of Kiel, Otto-Hahn-Platz 3-4, 24098 Kiel (Germany).
| |
Collapse
|
6
|
Koller SG, Kroesen U, Strohmann C. A Route to Stereochemically Pure Benzyllithium Reagents by Stereocontrolled Epimerisation. Chemistry 2014; 21:641-7. [DOI: 10.1002/chem.201405152] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Indexed: 11/07/2022]
|
7
|
Ghalib M, Jones PG, Lysenko S, Heinicke JW. Enantiomerically Pure N Chirally Substituted 1,3-Benzazaphospholes: Synthesis, Reactivity toward tBuLi, and Conversion to Functionalized Benzazaphospholes and Catalytically Useful Dihydrobenzazaphospholes. Organometallics 2014. [DOI: 10.1021/om401184n] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mohammed Ghalib
- Institut für Chemie und Biochemie, Ernst-Moritz-Arndt-Universität Greifswald, 17487 Greifswald, Germany
| | - Peter G. Jones
- Institut für Anorganische
und Analytische
Chemie der Technischen Universität Braunschweig, 38023 Braunschweig, Germany
| | - Sergej Lysenko
- Institut für Anorganische
und Analytische
Chemie der Technischen Universität Braunschweig, 38023 Braunschweig, Germany
| | - Joachim W. Heinicke
- Institut für Chemie und Biochemie, Ernst-Moritz-Arndt-Universität Greifswald, 17487 Greifswald, Germany
| |
Collapse
|
8
|
Reich HJ. Role of Organolithium Aggregates and Mixed Aggregates in Organolithium Mechanisms. Chem Rev 2013; 113:7130-78. [DOI: 10.1021/cr400187u] [Citation(s) in RCA: 248] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Hans J. Reich
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| |
Collapse
|
9
|
Sämann C, Schade MA, Yamada S, Knochel P. Functionalized Alkenylzinc Reagents Bearing Carbonyl Groups: Preparation by Direct Metal Insertion and Reaction with Electrophiles. Angew Chem Int Ed Engl 2013; 52:9495-9. [DOI: 10.1002/anie.201302058] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Indexed: 11/06/2022]
|
10
|
Sämann C, Schade MA, Yamada S, Knochel P. Alkenylzinkreagentien mit Carbonylgruppen: Synthese durch direkte Metallinsertion und Umsetzungen mit Elektrophilen. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201302058] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
11
|
Coppi DI, Salomone A, Perna FM, Capriati V. Exploiting the Lithiation-Directing Ability of Oxetane for the Regioselective Preparation of Functionalized 2-Aryloxetane Scaffolds under Mild Conditions. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201109113] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
12
|
Coppi DI, Salomone A, Perna FM, Capriati V. Exploiting the Lithiation-Directing Ability of Oxetane for the Regioselective Preparation of Functionalized 2-Aryloxetane Scaffolds under Mild Conditions. Angew Chem Int Ed Engl 2012; 51:7532-6. [DOI: 10.1002/anie.201109113] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 03/15/2012] [Indexed: 11/10/2022]
|
13
|
Gessner VH, Koller SG, Strohmann C, Hogan AM, O'Shea DF. Mechanistic insight into stereoselective carbolithiation. Chemistry 2011; 17:2996-3004. [PMID: 21294193 DOI: 10.1002/chem.201000814] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 10/05/2010] [Indexed: 11/07/2022]
Abstract
This article addresses the mechanistic features of asymmetric carbolithiation of β-methylstyrenes. While often the presence of functional groups is required to obtain high enantioselectivities in carbolithiation reactions, simple β-methylstyrene also gives high selectivities in (-)-sparteine-mediated addition of alkyl lithium compounds. Computational studies on the carbolithiation of β-methylstyrene with (-)-sparteine show that the observed selectivities are the result of repulsion effects in the diastereomeric transition states between the (-)-sparteine⋅alkyl lithium adduct and the β-methylstyrene, upon approximation of the two reactants. In contrast, for the ortho-amino β-methylstyrene (E)-benzyl(2-propenylphenyl)amine (4) X-ray structure analyses of intermediate lithium amides indicate a carbolithiation mechanism in which one side of the double bond is shielded by the amide moiety, leaving only one side free for approach of the chiral alkyl lithium adduct.
Collapse
Affiliation(s)
- Viktoria H Gessner
- Anorganische Chemie, Technische Universität Dortmund, Otto-Hahn-Strasse 6, 44227 Dortmund, Germany
| | | | | | | | | |
Collapse
|
14
|
Däschlein C, Bauer SO, Strohmann C. Mechanistic Insights into the Reaction of Enantiomerically Pure Lithiosilanes and Electrophiles: Understanding the Differences between Aryl and Alkyl Halides. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201000834] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
15
|
Klumpp GW, Geurink PJA, van Eikema Hommes NJR, de Kanter FJJ, Vos M, Spek AL. X-Ray structure of tetrameric 1-lithio-3-methoxypropane. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/recl.19861051014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
16
|
van der Zeijden AAH, van Koten G. Synthesis and structure of a bis-ortho
-chelated aryllithium compound: 2,3,5,6-tetrakis[(dimethylamino)methyl]phenyllithium dimer. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/recl.19881070607] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
17
|
Däschlein C, Gessner V, Strohmann C. Preparation of “Si-Centered” Chiral Silanes by Direct α-Lithiation of Methylsilanes. Chemistry 2010; 16:4048-62. [DOI: 10.1002/chem.200902551] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
18
|
Gorecka-Kobylinska J, Schlosser M. Relative Basicities of ortho-, meta-, and para-Substituted Aryllithiums. J Org Chem 2008; 74:222-9. [DOI: 10.1021/jo8020083] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joanna Gorecka-Kobylinska
- Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale (EPFL−BCh), CH-1015 Lausanne, Switzerland
| | - Manfred Schlosser
- Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale (EPFL−BCh), CH-1015 Lausanne, Switzerland
| |
Collapse
|
19
|
Fleming FF, Gudipati S. Cyclic Metalated Nitriles: Stereoselective Cyclizations to cis- and trans-Hydrindanes, Decalins, and Bicyclo[4.3.0]undecanes. European J Org Chem 2008; 2008:10.1002/ejoc.200800715. [PMID: 24260015 PMCID: PMC3831376 DOI: 10.1002/ejoc.200800715] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Indexed: 11/07/2022]
Abstract
Metalated nitriles are nucleophilic chameleons whose precise identity is determined by the nature of the metal, the solvent, the temperature, and the structure of the nitrile. The review surveys the different structural types and their cyclization trajectories to show how to selectively tune the metalated nitrile geometry for stereoselective cyclizations to a variety of cis or trans hydrindanes, decalins, and bicyclo[4.3.0]undecanes.
Collapse
Affiliation(s)
- Fraser F. Fleming
- Department of Chemistry and Biochemistry, Mellon Hall, Duquesne University, Pittsburgh PA 15282-1530, USA
| | - Subramanyham Gudipati
- Schering-Plough Research Institute, 2015 Galloping Hill Road, Kenilworth, N.J. 07033-0530, USA Fax: +1-908-740-7441
| |
Collapse
|
20
|
Ott H, Däschlein C, Leusser D, Schildbach D, Seibel T, Stalke D, Strohmann C. Structure/Reactivity Studies on an α-Lithiated Benzylsilane: Chemical Interpretation of Experimental Charge Density. J Am Chem Soc 2008; 130:11901-11. [DOI: 10.1021/ja711104q] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Holger Ott
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany, and Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christian Däschlein
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany, and Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Dirk Leusser
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany, and Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Daniel Schildbach
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany, and Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Timo Seibel
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany, and Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Dietmar Stalke
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany, and Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Carsten Strohmann
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany, and Institut für Anorganische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| |
Collapse
|
21
|
Fleming FF, Wei Y, Liu W, Zhang Z. Metalated Nitriles: Stereodivergent Cation-Controlled Cyclizations1. Tetrahedron 2008; 64:7477-7488. [PMID: 19657380 PMCID: PMC2597827 DOI: 10.1016/j.tet.2008.05.110] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Stereodivergent cyclizations of gamma-hydroxy cyclohexanecarbonitriles are controlled simply through judicious choice of cation in the alkylmetal base. Deprotonating a series of cyclic gamma-hydroxy nitriles with i-PrMgBr generates C-magnesiated nitriles that cyclize under stereoelectronic control to cis-fused hydrindanes, decalins, and bicyclo [5.4.0] undecanes. An analogous deprotonation with BuLi triggers cyclization to trans-fused hydrindanes, decalins, and bicyclo [5.4.0] undecanes consistent with a sterically controlled electrophilic attack on an equatorial nitrile anion. Using cations to control the geometry of metalated nitriles provides a versatile, stereodivergent cyclization to cis- and trans-hydrindanes, decalins, and [5. 4. 0] undecanes, and reveals the key geometric requirements for intramolecular S(N)2 and S(N)2' displacements.
Collapse
Affiliation(s)
- Fraser F. Fleming
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530,
| | - Yunjing Wei
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530,
| | - Wang Liu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530,
| | - Zhiyu Zhang
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530,
| |
Collapse
|
22
|
Godenschwager P, Collum DB. Lithium hexamethyldisilazide-mediated enolizations: influence of triethylamine on E/Z selectivities and enolate reactivities. J Am Chem Soc 2008; 130:8726-32. [PMID: 18557616 PMCID: PMC3021125 DOI: 10.1021/ja800250q] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lithium hexamethyldisilazide (LiHMDS) in triethylamine (Et 3N)/toluene is shown to enolize acyclic ketones and esters rapidly and with high E/ Z selectivity. Mechanistic studies reveal a dimer-based mechanism consistent with previous studies of LiHMDS/Et 3N. E/ Z equilibration occurs when <2.0 equiv of LiHMDS are used. Studies of the aldol condensation and Ireland-Claisen rearrangement of the resulting Et 3N-solvated enolates show higher and often complementary diastereoselectivities when compared with analogous reactions in THF. The Et 3N-solvated enolates also display a marked (20-fold) acceleration of the Ireland-Claisen rearrangement with evidence of autocatalysis. A possible importance of amine-solvated enolates is discussed.
Collapse
Affiliation(s)
- Peter Godenschwager
- Contribution from the Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301
| | - David B. Collum
- Contribution from the Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301
| |
Collapse
|
23
|
Chase PA, Lutz M, Spek AL, Gossage RA, van Koten G. Solid-state and solution structures of hetero-aggregates formed between nBuLi and NCN pincer aryl lithium. Dalton Trans 2008:5783-90. [DOI: 10.1039/b805092a] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
24
|
Fleming FF, Gudipati S, Vu VA, Mycka RJ, Knochel P. Grignard Reagents: Alkoxide-Directed Iodine−Magnesium Exchange at sp3 Centers. Org Lett 2007; 9:4507-9. [DOI: 10.1021/ol701947y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Fraser F. Fleming
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530 and Department Chemie, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377, München, Germany
| | - Subrahmanyam Gudipati
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530 and Department Chemie, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377, München, Germany
| | - Viet Anh Vu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530 and Department Chemie, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377, München, Germany
| | - Robert J. Mycka
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530 and Department Chemie, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377, München, Germany
| | - Paul Knochel
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282-1530 and Department Chemie, Ludwig-Maximilians-Universität, Butenandtstrasse 5-13, 81377, München, Germany
| |
Collapse
|
25
|
He X, Morris JJ, Noll BC, Brown SN, Henderson KW. Kinetics and mechanism of ketone enolization mediated by magnesium bis(hexamethyldisilazide). J Am Chem Soc 2007; 128:13599-610. [PMID: 17031975 DOI: 10.1021/ja064927w] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Magnesium bis(hexamethyldisilazide), Mg(HMDS)(2), reacts with substoichiometric amounts of propiophenone in toluene solution at ambient temperature to form a 74:26 mixture of the enolates (E)- and (Z)-[(HMDS)(2)Mg(2)(mu-HMDS){mu-OC(Ph)=CHCH(3)}], (E)-1 and (Z)-1, which contain a pair of three-coordinate metal centers bridged by an amide and an enolate group. The compositions of (E)-1 and (Z)-1 were confirmed by solution NMR studies and also by crystallographic characterization in the solid state. Rate studies using UV-vis spectroscopy reveal the rapid and complete formation of a reaction intermediate, 2, between the ketone and magnesium, which undergoes first-order decay with rate constants independent of the concentration of excess Mg(HMDS)(2) (DeltaH++ = 17.2 +/- 0.8 kcal/mol, DeltaS++ = -11 +/- 3 cal/mol.K). The intermediate 2 has been characterized by low-temperature (1)H NMR, diffusion-ordered NMR, and IR spectroscopy and investigated by computational studies, all of which are consistent with the formulation of 2 as a three-coordinate monomer, (HMDS)(2)Mg{eta(1)-O=C(Ph)CH(2)CH(3)}. Further support for this structure is provided by the synthesis and structural characterization of two model ketone complexes, (HMDS)(2)Mg(eta(1)-O=C(t)Bu(2)) (3) and (HMDS)(2)Mg{eta(1)-O=C((t)Bu)Ph} (4). A large primary deuterium isotope effect (k(H)/k(D) = 18.9 at 295 K) indicates that proton transfer is the rate-limiting step of the reaction. The isotope effect displays a strong temperature dependence, indicative of tunneling. In combination, these data support the mechanism of enolization proceeding through the single intermediate 2 via intramolecular proton transfer from the alpha carbon of the bound ketone to the nitrogen of a bound hexamethyldisilazide.
Collapse
Affiliation(s)
- Xuyang He
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA
| | | | | | | | | |
Collapse
|
26
|
Godenschwager PF, Collum DB. Lithium Hexamethyldisilazide-Mediated Enolizations: Influence of Chelating Ligands and Hydrocarbon Cosolvents on the Rates and Mechanisms. J Am Chem Soc 2007; 129:12023-31. [PMID: 17850084 DOI: 10.1021/ja074018m] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enolizations of 2-methylcyclohexanone by lithium hexamethyldisilazide (LiHMDS) in the presence of three chelating ligands--trans-N,N,N',N'-tetramethylcyclohexanediamine, N,N,N',N'-tetramethylethylenediamine, and dimethoxyethane--reveal an approximate 40-fold range of rates. NMR spectroscopic analyses and rate studies reveal isostructural transition structures based on monomeric LiHMDS for the diamines. Rate studies of LiHMDS/dimethoxyethane-mediated enolizations implicate a substantial number of monomer- and dimer-based mechanisms. The rate laws vary for the three ligands because of ligand-dependent structural differences in both the reactants and the transition structures. The importance of LiHMDS-ketone complexes and the role of hydrocarbon cosolvents are discussed.
Collapse
Affiliation(s)
- Peter F Godenschwager
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University Ithaca, New York 14853-1301, USA
| | | |
Collapse
|
27
|
Reich HJ, Sikorski WH, Thompson JL, Sanders AW, Jones AC. Interconversion of contact and separated ion pairs in silyl- and arylthio-substituted alkyllithium reagents. Org Lett 2007; 8:4003-6. [PMID: 16928059 DOI: 10.1021/ol061489p] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ether-solvated contact and separated ion pairs (CIP and SIP) for two lithium reagents, tris(trimethylsilyl)methyllithium (1) and bis(3,5-bistrifluoromethylphenylthio)methyllithium (2), have been characterized and observed for the first time under conditions of slow exchange by NMR spectroscopy, and barriers to interconversion have been measured. A Saunders isotope perturbation experiment was used to support identification of the CIP and SIP species for 2.
Collapse
Affiliation(s)
- Hans J Reich
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, WI 53706, USA.
| | | | | | | | | |
Collapse
|
28
|
Fraenkel G, Gallucci J, Liu H. Perturbation of Conjugation in Internally Solvated Allylic Lithium Compounds: Variation of Ligand Structure. NMR and X-ray Crystallography. J Am Chem Soc 2006; 128:8211-6. [PMID: 16787085 DOI: 10.1021/ja060272n] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several allyic lithium compounds were prepared with different potential ligands tethered at C2. These are with CH3OCH2CH2NCH3CH2-, 5 and 1-TMS 6, with (CH3)2NCH2CH2NCH3CH2-, 1-TMS 7, and with ((CH3)2NCH2CH2)2NCH2-, 8 and 1-TMS 9. In all these compounds Li is fully coordinated to the pendant ligand and is sited off the axis perpendicular to the allyl plane at one of the allyl termini as indicated by a combination of X-ray crystallography and NMR spectra. Compounds 5 and 8 are Li-bridged dimers as shown by X-ray crystallography and also dimeric in benzene solution as determined from freezing point determinations. Compounds 6, 7, and 9 are monomeric in THF-d8 or diethyl ether-d10 solution and exhibit one bond 13C1, 6Li scalar coupling at low temperature. Taken together the crystallographic and NMR data indicate that all of these compounds incorporate partially delocalized allylic moieties. Compounds 5 and 8 undergo fast 1,3-Li-sigmatropic shifts that are proposed to take place within low concentrations of monomers in fast equilibrium with prevalent dimers. Averaging with increasing temperature of the one-bond 13C, 6Li coupling constant in 6, 7, and 13 provided the dynamics of bimolecular C-Li exchange with Delta H++ values of 6.7, 12, and 13 kcal x mol(-1), respectively. Averaging of the diastereotopic N(CH3)2 13C resonances of 7 is indicative of fast transfer of coordinated ligand between faces of the allyl plane Delta H++ = 5.3 kcal x mol(-1) combined with slower inversion at nitrogen. Compound 8 exhibits similar effects. It is concluded that variation of the ligand structure changes dynamic behavior of the compounds but has little influence of their degrees of delocalization.
Collapse
Affiliation(s)
- Gideon Fraenkel
- Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
| | | | | |
Collapse
|
29
|
Barr D, Berrisford DJ, Jones RVH, Slawin AMZ, Snaith R, Stoddart JF, Williams DJ. Ein neues, chirales, koordinationsfähiges Lithiumamid. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.19891010815] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
30
|
Jacobson MA, Keresztes I, Williard PG. On the mechanism of THF catalyzed vinylic lithiation of allylamine derivatives: structural studies using 2-D and diffusion-ordered NMR spectroscopy. J Am Chem Soc 2005; 127:4965-75. [PMID: 15796563 DOI: 10.1021/ja0479540] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
N-Lithio-N-(trialkylsilyl)allylamines can be deprotonated in the presence of ethereal solvents exclusively at the cis-vinylic position to yield 3,N-dilithio-N-(trialkylsilyl)allylamines under mild conditions. Low temperature (1)H and (7)Li NMR ((1)H NOESY, TOCSY, (1)H/(7)Li HSQC, and DO-NMR) studies on the solution structure of 3,N-dilithio-N-(tert-butyldimethylsilyl)allylamine identified three major aggregates in THF (monomer, dimer and tetramer), but the aggregate structures failed to explain the solvent dependence and regiochemical outcome of the reaction. Low temperature (1)H NMR (NOESY, TOCSY, DO-NMR) studies on the solution structure of N-lithio-N-(tert-butyldimethylsilyl)allylamine in the presence of nBuLi identified amide/nBuLi mixed aggregates in both the ethereal solvent THF (1:1 dimer) and the hydrocarbon solvent toluene (1:3 tetramer). Addition of 2 equiv of THF to toluene solutions induces the formation of the same THF solvated 1:1 dimer as observed in neat THF. NMR evidence suggests that in THF the mixed aggregate has close contact between the olefin and the beta-CH(2) of nBuLi, while in the absence of THF, the allyl chain appears to be pointed away from the nearest nBuLi residues.
Collapse
|
31
|
Bookser BC, Matelich MC, Ollis K, Ugarkar BG. Adenosine Kinase Inhibitors. 4. 6,8-Disubstituted Purine Nucleoside Derivatives. Synthesis, Conformation, and Enzyme Inhibition. J Med Chem 2005; 48:3389-99. [PMID: 15857145 DOI: 10.1021/jm048968j] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
6,8-Disubstituted purine nucleosides were synthesized and evaluated as adenosine kinase inhibitors (AKIs). A method was developed to selectively substitute arylamines for halogens at C6 and C8 which utilizes alkali salts of arylamino anions. Regioselectivity was found to be counterion dependent. Potassium and sodium salts add selectively to C6 of 6-chloro-8-iodo-9-(2,3,5-tris-O-tert-butyldimethylsilyl-beta-d-ribofuranosyl)purine (7a) while lithium salts add to C6 and C8 positions. Differential 6,8-bisarylamin-N,N'-diylpurine nucleosides such as 8-anilin-N-yl-6-indolin-N-yl-9-(beta-d-ribofuranosyl)purine (10b) can be prepared by employing stepwise reactions of potassium and then lithium salts of different arylamino anions followed by fluoride ion-induced desilylation. Other C8-substituted compounds were prepared by way of either C8 lithiation chemistry or palladium cross-coupling reactions. Several of these compounds were potent AKIs (e.g. 10b, AK IC(50) = 0.019 microM) and are more potent than the previous best purine-based AKI 5'-deoxy-5'-aminoadenosine (AK IC(50) = 0.170 microM). AK inhibitory potency was greatest for those compounds with (1)H NMR evidence of a predominant anti glycosyl bond conformation, whereas most analogues adopt a syn conformation because of steric repulsions between the C8 substituent and the ribose group. The inhibitors are proposed to bind in the anti conformation with the hydrophobic C6 and C8 substituents contributing to AK affinity in a manner similar to the C4 and C5 aryl substituents of the potent diaryltubercidin nucleoside inhibitor series.
Collapse
Affiliation(s)
- Brett C Bookser
- Metabasis Therapeutics, Inc., 9390 Towne Centre Drive, San Diego, California 92121, USA. bookser@ mbasis.com
| | | | | | | |
Collapse
|
32
|
Stereochemistry of the cyclization of alkoxy-substituted 5-hexenyllithiums: effect of solvent and lithium iodide on diastereoselectivity. Tetrahedron 2005. [DOI: 10.1016/j.tet.2005.01.042] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
33
|
Gohier F, Castanet AS, Mortier J. The First Regioselective Metalation and Functionalization of Unprotected 4-Halobenzoic Acids. J Org Chem 2005; 70:1501-4. [PMID: 15704996 DOI: 10.1021/jo0483365] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] By treatment with s-BuLi, s-BuLi/TMEDA, or t-BuLi at approximately -78 degrees C, 4-fluoro- and 4-chlorobenzoic acids (1a,b) are metalated preferentially in the position adjacent to the carboxylate. A complete reversal in regioselectivity is observed for 1a when treated with LTMP; a sequential process involving a rapid intraaggregate lithiation through a quasi dianion complex "QUADAC" is postulated to explain the unusual reactivity of Me(2)S(2) and I(2).
Collapse
Affiliation(s)
- Frédéric Gohier
- Université du Maine and CNRS, Unité de chimie organique moléculaire et macromoléculaire (UMR 6011), Faculté des sciences, avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France
| | | | | |
Collapse
|
34
|
Fernández I, González J, López-Ortiz F. Deuterium-Labeling and NMR Study of the Dearomatization of N-Alkyl-N-benzyldiphenylphosphinamides through Anionic Cyclization: Ortho and Benzylic Lithiation Directed by Complex-Induced Proximity Effects. J Am Chem Soc 2004; 126:12551-64. [PMID: 15453788 DOI: 10.1021/ja039863t] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism of the anionic cyclization dearomatizing reaction of N-benzyl-N-methyldiphenylphosphinamide (1) upon treatment with s-BuLi in tetrahydrofuran (THF) at -90 degrees C has been analyzed by deuterium-labeling and natural abundance multinuclear magnetic resonance ((1)H, (2)H, (7)Li, (13)C, (31)P) studies. In the absence of coordinating cosolvents such as hexamethylphosphoramide (HMPA), eight major anionic species were identified, which allowed us to unravel the pathway of the metalation reaction. In agreement with the complex-induced proximity effect (CIPE) mechanism, the sequence of transformations emerging from this study involves the coordination of the lithium base to the P=O group of 1 to give four dimeric precomplexes whose NMR data are consistent with structures Va/Vb and VIIIa/VIIIb. The diastereomers Va/Vb are the precursors of the monomeric benzylic anion II, whereas the VIIIa/VIIIb diastereomers are assumed to undergo ortho deprotonation leading to anions I. Translocation from the ortho anion to the benzylic one is not observed. Intramolecular conjugate addition of anion II to the P-phenyl rings happens in a reversible way, affording the monomeric dearomatized anions III, IV, VI, and VII. The reaction progresses to yield a mixture containing only the species I, III, and IV. HMPA acts as a catalyst for the ortho-to-benzylic translocation and anionic cyclization reactions. Two-dimensional (2D) (7)Li,(31)P[(1)H] shift correlations and (7)Li[(31)P] NMR spectra proved to be crucial for the structural assignment of the anionic species. These techniques also demonstrated the diastereotopicity of the two achiral ligands involved in a dimer with s-BuLi (Vb) owing to the slow configuration inversion of the carbanion center.
Collapse
Affiliation(s)
- Ignacio Fernández
- Area de Química Orgánica, Universidad de Almería, Carretera de Sacramento s/n, Almería, Spain
| | | | | |
Collapse
|
35
|
Xu J, Jain N, Sui Z. Halogen–magnesium exchange of m- and p-iodo or bromo-arenes bearing ortho-directing groups through ate complexes. Tetrahedron Lett 2004. [DOI: 10.1016/j.tetlet.2004.07.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
36
|
Rebstock AS, Mongin F, Trécourt F, Quéguiner G. Regioselectivities in deprotonation of 2-(4-chloro-2-pyridyl)benzoic acid and corresponding ester and amide. Tetrahedron 2004. [DOI: 10.1016/j.tet.2004.01.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
37
|
Zhao P, Condo A, Keresztes I, Collum DB. Reaction of Ketones with Lithium Hexamethyldisilazide: Competitive Enolizations and 1,2-Additions. J Am Chem Soc 2004; 126:3113-8. [PMID: 15012141 DOI: 10.1021/ja030582v] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction of 2-methylcyclohexanone with lithium hexamethyldisilazide (LiHMDS, TMS(2)NLi) displays highly solvent-dependent chemoselectivity. LiHMDS in THF/toluene effect enolization. Rate studies using in situ IR spectroscopy are consistent with a THF concentration-dependent monomer-based pathway. LiHMDS in pyrrolidine/toluene affords exclusively 1,2-addition of the pyrrolidine fragment to form an alpha-amino alkoxide-LiHMDS mixed dimer shown to be a pair of conformers by using (6)Li, (15)N, and (13)C NMR spectroscopies. Rate studies are consistent with a monomer-based transition structure [(TMS(2)NLi)(ketone)(pyrrolidine)(3)](). The partitioning between enolization and 1,2-addition is kinetically controlled.
Collapse
Affiliation(s)
- Pinjing Zhao
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
| | | | | | | |
Collapse
|
38
|
Rebstock AS, Mongin F, Trécourt F, Quéguiner G. Metallation of pyridines and quinolines in the presence of a remote carboxylate group. New syntheses of heterocyclic quinones. Org Biomol Chem 2004; 2:291-5. [PMID: 14747855 DOI: 10.1039/b312723k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2-(3- and 2-Pyridylcarbonyl)benzoic acids (2,3), 2-(2-pyridylcarbonyl)thiophene-3-carboxylic acid (6), 2-(3-quinolylcarbonyl)benzoic acid (10), and most of the corresponding esters (compounds 1,7 and 9 ) are readily synthesized and involved in a deprotonation-condensation sequence. Biologically active aza-anthraquinones such as benzo[g]isoquinoline-5,10-dione (2-azaanthraquinone, 4 ) and benzo[g]quinoline-5,10-dione (1-azaanthraquinone, 5) are prepared using the strategy. Extension to other heterocyclic quinones such as thieno[3,2-g]quinoline-4,9-dione (8) and benzo[j]phenanthridine-7,12-dione (11) is also investigated.
Collapse
Affiliation(s)
- Anne-Sophie Rebstock
- Laboratoire de Chimie Organique Fine et Hétérocyclique, IRCOF, UMR 6014, Place E. Blondel, BP 08, 76131 Mont-Saint-Aignan, France.
| | | | | | | |
Collapse
|
39
|
Ramírez A, Lobkovsky E, Collum DB. Hemilabile Ligands in Organolithium Chemistry: Substituent Effects on Lithium Ion Chelation. J Am Chem Soc 2003; 125:15376-87. [PMID: 14664582 DOI: 10.1021/ja030322d] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The lithium diisopropylamide-mediated 1,2-elimination of 1-bromocyclooctene to provide cyclooctyne is investigated using approximately 50 potentially hemilabile polyethers and amino ethers. Rate laws for selected ligands reveal chelated monomer-based pathways. The dependence of the rates on ligand structure shows that anticipated rate accelerations based on the gem-dimethyl effect are nonexistent and that substituents generally retard the reaction. With the aid of semiempirical and DFT computational studies, the factors influencing chelation are discussed. It seems that severe buttressing within chelates of the substitutionally rich ligands precludes a net stabilization of the chelates relative to nonchelated (eta(1)-solvated) forms. One ligand-MeOCH(2)CH(2)NMe(2)-appears to promote elimination uniquely by a higher-coordinate monomer-based pathway.
Collapse
Affiliation(s)
- Antonio Ramírez
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA
| | | | | |
Collapse
|
40
|
Zhao P, Lucht BL, Kenkre SL, Collum DB. Lithium Hexamethyldisilazide-Mediated Ketone Enolization: The Influence of Hindered Dialkyl Ethers and Isostructural Dialkylamines on Reaction Rates and Mechanisms. J Org Chem 2003; 69:242-9. [PMID: 14725435 DOI: 10.1021/jo030221y] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mechanistic studies of the enolization of 2-methylcyclohexanone mediated by lithium hexamethyldisilazide (LiHMDS; TMS(2)NLi) solvated by hindered dialkyl ethers (ROR') are described. Rate studies using in situ IR spectroscopy show that enolizations in the presence of i-Pr(2)O, 2,2,5,5-tetramethyltetrahydrofuran, and cineole proceed via dimer-based transition structures [(TMS(2)NLi)(2)(ROR')(ketone)]. Comparing the relative solvation energies and the corresponding solvent-dependent activation energies shows that the highly substituted ethers accelerate the enolizations by sterically destabilizing the reactants and stabilizing the transition structures. Comparisons of hindered dialkyl ethers with their isostructural dialkylamines reveal that the considerably higher rates elicited by the amines derive from an analogous relative destabilization of the reactants and relative stabilization of the transition structures.
Collapse
Affiliation(s)
- Pinjing Zhao
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
| | | | | | | |
Collapse
|
41
|
Zhao P, Collum DB. Ketone Enolization by Lithium Hexamethyldisilazide: Structural and Rate Studies of the Accelerating Effects of Trialkylamines. J Am Chem Soc 2003; 125:14411-24. [PMID: 14624589 DOI: 10.1021/ja030168v] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mechanistic studies of the enolization of 2-methylcyclohexanone mediated by lithium hexamethyldisilazide (LiHMDS; TMS2NLi) in toluene and toluene/amine mixtures are described. NMR spectroscopic studies of LiHMDS/ketone mixtures in toluene reveal the ketone-complexed cyclic dimer (TMS2NLi)2(ketone). Rate studies using in situ IR spectroscopy show the enolization proceeds via a dimer-based transition structure, [(TMS2NLi)2(ketone)]++. NMR spectroscopic studies of LiHMDS/ketone mixtures in the presence of relatively unhindered trialkylamines such as Me2NEt reveal the quantitative formation of cyclic dimers of general structure (TMS2NLi)2(R3N)(ketone). Rate studies trace a >200-fold rate acceleration to a dimer-based transition structure, [(TMS2NLi)2(R3N)(ketone)]++. Amines of intermediate steric demand, such as Et3N, are characterized by recalcitrant solvation, saturation kinetics, and exceptional (>3000-fold) accelerations traced to the aforementioned dimer-based pathway. Amines of high steric demand, such as i-Pr2NEt, do not observably solvate (TMS2NLi)2(ketone) but mediate enolization via [(TMS2NLi)2(R3N)(ketone)]++ with muted accelerations. The most highly hindered amines, such as i-Bu3N, do not influence the LiHMDS structure or the enolization rate. Overall, surprisingly complex dependencies of the enolization rates on the structures and concentrations of the amines derive from unexpectedly simple steric effects. The consequences of aggregation, mixed aggregation, and substrate-base precomplexation are discussed.
Collapse
Affiliation(s)
- Pinjing Zhao
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14853-1301, USA
| | | |
Collapse
|
42
|
Fort Y, Rodriguez AL. First regioselective ortho-lithiation induced by a 2-chloropyridyl group complexation. J Org Chem 2003; 68:4918-22. [PMID: 12790600 DOI: 10.1021/jo026788g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It is shown that t-BuLi in Et(2)O promotes an exclusive regioselective metalation of 2-aryl-6-chloropyridine compounds at the aromatic ortho position demonstrating that the 2-chloropyridyl moiety may be considered as a directing group. This functionally directed metalation group was successfully used for the selective lithiation of substituted aromatics and for the straightforward preparation of new N,P ligands.
Collapse
Affiliation(s)
- Yves Fort
- Synthèse Organique et Réactivité, UMR CNRS-UHP 7565, Faculté des Sciences, Université Henri Poincaré-Nancy I, BP 239, 54506 Vandoeuvre-Lès-Nancy, France.
| | | |
Collapse
|
43
|
Synthesis and metallation of 2-(pyridyl)benzoic acids and ethyl 2-(pyridyl)benzoates: a new route to azafluorenones. Tetrahedron 2003. [DOI: 10.1016/s0040-4020(03)00761-0] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
44
|
Gohier F, Castanet AS, Mortier J. Selectivities in reactions of organolithium reagents with unprotected 2-halobenzoic acids. Org Lett 2003; 5:1919-22. [PMID: 12762686 DOI: 10.1021/ol034491e] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] Exposing 2-fluorobenzoic acid (1a) to 2.2 equiv of LTMP at ca. -78 degrees C leads to deprotonation at the 3-position whereas 2-chloro/bromobenzoic acids (1b,c) are lithiated adjacent to the carboxylate. The resulting dianions 3Li-1a and 6Li-1b,c are trapped as such by chlorotrimethylsilane. In the absence of internal quench, 6Li-1b,c isomerize to the more stable 3Li-1b,c. The latter eliminate lithium halide and set free benzyne-3-carboxylate (2) that reacts regioselectively with LTMP to give 3-tetramethylpiperidinobenzoic acid (3).
Collapse
Affiliation(s)
- Frédéric Gohier
- Université du Maine and CNRS, Unité de chimie organique moléculaire et macromoléculaire (UMR 6011), Faculté des sciences, avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France
| | | | | |
Collapse
|
45
|
Reich HJ, Goldenberg WS, Sanders AW, Jantzi KL, Tzschucke CC. Amine- and ether-chelated aryllithium reagents-structure and dynamics. J Am Chem Soc 2003; 125:3509-21. [PMID: 12643713 DOI: 10.1021/ja028301r] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chelation and aggregation in phenyllithium reagents with potential 6- and 7-ring chelating amine (2, 3) and 5-, 6-, and 7-ring chelating ether (4, 5, 6) ortho substituents have been examined utilizing variable temperature (6)Li and (13)C NMR spectroscopy, (6)Li and (15)N isotope labeling, and the effects of solvent additives. The 5- and 6-ring ether chelates (4, 5) compete well with THF, but the 6-ring amine chelate (2) barely does, and 7-ring amine chelate (3) does not. Compared to model compounds (e.g., 2-ethylphenyllithium 7), which are largely monomeric in THF, the chelated compounds all show enhanced dimerization (as measured by K = [D]/[M](2)) by factors ranging from 40 (for 6) to more than 200 000 (for 4 and 5). Chelation isomers are seen for the dimers of 5 and 6, but a chelate structure could be assigned only for 2-(2-dimethylaminoethyl)phenyllithium (2), which has an A-type structure (both amino groups chelated to the same lithium in the dimer) based on NMR coupling in the (15)N, (6)Li labeled compound. Unlike the dimer, the monomer of 2 is not detectably chelated. With the exception of 2-(methoxymethyl)phenyllithium (4), which forms an open dimer (12) and a pentacoordinate monomer (13), the lithium reagents all form monomeric nonchelated adducts with PMDTA.
Collapse
Affiliation(s)
- Hans J Reich
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
| | | | | | | | | |
Collapse
|
46
|
Rebstock AS, Mongin F, Trécourt F, Quéguiner G. Synthesis and deprotonation of 2-(pyridyl)phenols and 2-(pyridyl)anilines. Org Biomol Chem 2003; 1:3064-8. [PMID: 14518130 DOI: 10.1039/b305043b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2-(2- and 3-Pyridyl)anilines (1, 2), 2,2-dimethyl-N-[2-(2- and 3-pyridyl)phenyl]propanamides (3, 4), and 2-, 3- and 4-(2-methoxyphenyl)pyridines (7-9) are readily synthesized using cross-coupling reactions. Whereas the amines 1, 2 undergo side reactions, the corresponding amides 3, 4 are deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LTMP): the compound 3 at C6' under in situ quenching, and the compound 4 at C4'. When the ether 7 is subjected to the same reagent, lithiation occurs at C6'.
Collapse
Affiliation(s)
- Anne-Sophie Rebstock
- Laboratoire de Chimie Organique Fine et Hétérocyclique, IRCOF, UMR 6014, Place E. Blondel, BP 08, 76131 Mont-Saint-Aignan, France
| | | | | | | |
Collapse
|
47
|
Yus M, Ramón DJ, Gómez I. Six- and five-membered 3-alkoxy-2-lithiocycloalkenes: new stable non-anionic β-functionalised organolithium compounds. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(02)00454-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
48
|
Bailey WF, Beak P, Kerrick ST, Ma S, Wiberg KB. An experimental and computational investigation of the enantioselective deprotonation of Boc-piperidine. J Am Chem Soc 2002; 124:1889-96. [PMID: 11866600 DOI: 10.1021/ja012169y] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The asymmetric deprotonation of N-Boc-piperidine (3) by the 1:1 complex of a sec-alkyllithium and (-)-sparteine has been investigated both experimentally and computationally. The lithiation of 3 with sec-BuL-(-)-sparteine at -78 degrees C, which is a much slower process than is the analogous deprotonation of N-Boc-pyrrolidine (1) and a minor reaction relative to the competing addition of sec-BuLi to the carbamate, proceeds with a moderate degree of selectivity (er = 87:13) for removal of the pro-S hydrogen of 3. The related deprotonation of N-Boc-4-tosyloxypiperidine (6) with two molar equiv of sec-BuL-(-)-sparteine also involves preferential transfer of the pro-S hydrogen. The computational study of the deprotonation of (3) by i-PrL-(-)-sparteine found that the proton that is preferentially transferred within three-component intermediate complex is the thermodynamically least acidic alpha-hydrogen of 3. The asymmetric deprotonation of 3 is calculated to proceed with poor enantioselectivity and to have an activation energy considerably higher than that calculated for deprotonation of N-Boc-pyrrolidine (1). The experimental and computational results are in good agreement.
Collapse
Affiliation(s)
- William F Bailey
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, USA
| | | | | | | | | |
Collapse
|
49
|
Bailey WF, Zarcone LMJ. Regioselective and stereoselective cleavage of cis-4-methyl-2-vinyl-l,3-dioxane by alkyllithiums. Chirality 2002; 14:163-5. [PMID: 11835559 DOI: 10.1002/chir.10063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The reaction of alkyllithiums with cis-4-methyl-2-vinyl-1,3-dioxane proceeds in virtually quantitative yield via a formal S(N)2' ring opening that proceeds in a regioselective manner to give preferential cleavage of the C(2)-O(l) bond remote from the 4-methyl substituent, affording the E-enol ether as the major stereoisomer. A two-step mechanism, involving addition of the alkyllithium followed by syn-elimination of lithium alkoxide, is suggested to account for the stereochemical outcome.
Collapse
Affiliation(s)
- William F Bailey
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, USA. bailey@uconnvm.-uconn.edu
| | | |
Collapse
|
50
|
Regio- and Stereoselective Addition Reactions of Organolithiums. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1460-1567(02)80038-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
|