DOCSLIB.ORG

Diaryliodonium Salts Development of Synthetic Methodologies and Α-Arylation of Enolates

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Diaryliodonium Salts Development of Synthetic Methodologies and Α-Arylation of Enolates Diaryliodonium Salts Development of Synthetic Methodologies and α-Arylation of Enolates Marcin Bielawski © Marcin Bielawski, Stockholm 2011 Cover picture: Diphenyliodonium lacking an anion! ISBN: 978-91-7447-233-2 Printed in Sweden by US-AB, Stockholm 2011 Distributor: Department of Organic Chemistry, Stockholm University ii The most exciting phrase to hear in science, the one that heralds the most di s- coveries, is not "Eureka!" (I found it!) but "That's funny..." Isaac Asimov (1920–1992) iii iv Abstract This thesis describes novel reaction protocols for the synthesis of diaryl- iodonium salts and also provides an insight to the mechanism of α-arylation of carbonyl compounds with diaryliodonium salts. The first chapter gives a general introduction to the field of hypervalent iodine chemistry, mainly focusing on recent developments and applications of diaryliodonium salts. Chapter two describes the synthesis of electron-rich to electron-poor di- aryliodonium triflates, in moderate to excellent yields from a range of arenes and iodoarenes. In chapter three, it is described that molecular iodine can be used together with arenes in a direct one-pot, three-step synthesis of symmetric diaryl- iodonium triflates. A large scale synthesis of bis(4-tert -butylphenyl)- iodonium triflate is also described, controlled and verified by an external research group, further demonstrating the reliability of this methodology. The fourth chapter describes the development of a sequential one-pot syn- thesis of diaryliodonium salts from aryl iodides and boronic acids, furnishing symmetric and unsymmetric, electron-rich to electron-poor diaryliodonium tetrafluoroborates in moderate to excellent yields. This method was devel- oped to overcome the regiochemical limitations imposed by the reaction mechanism in the protocols described in the preceding chapters. Chapter five describes a one-pot synthesis of heteroaromatic iodonium salts under similar conditions described in chapter two. The final chapter describes the reaction of enolates with chiral diaryliodo- nium salts or together with a phase transfer catalyst yielding racemic prod- ucts. DFT calculations were performed, which revealed a low lying energy transition state (TS) between intermediates, which is believed to be respon- sible for the lack of selectivity observed in the experimental work. It is also proposed that a [2,3] rearrangement is preferred over a [1,2] rearrangement in the α-arylation of carbonyl compounds. The synthetic methodology described in this thesis is the most generally applicable, efficient and high-yielding to date for the synthesis of diaryl- iodonium salts, making these reagents readily available for various applica- tions in synthesis. v vi List of Publications This thesis is based on the following publications, in the text referred to by their Roman numerals I-V and Appendix B. My contribution to these papers is summarized in Appendix A. I. High-Yielding One-Pot Synthesis of Diaryliodonium Triflates from Arenes and Iodine or Aryl Iodides Marcin Bielawski and Berit Olofsson Chem. Commun. 2007 , 2521-2523. Reproduced by permission of The Royal Society of Chemistry (RSC). II. Efficient and General One-Pot Synthesis of Diaryliodonium Triflates: Optimization, Scope and Limitations Marcin Bielawski, Mingzhao Zhu and Berit Olofsson Adv. Synth. Catal. 2007 , 349 , 2610-2618. Copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission. III. Efficient One-pot Synthesis of Bis(4-tert -Butylphenyl)Iodonium Triflate Marcin Bielawski and Berit Olofsson Org. Synth. 2009 , 86 , 308-314. IV. Reproduced with permission from Regiospecific One-Pot Synthesis of Diaryliodonium Tetrafluoroborates from Arylboronic Acids and Aryl Iodides Marcin Bielawski, David Aili and Berit Olofsson J. Org. Chem. 2008 , 73 , 4602-4607. Copyright 2011 American Chemical Society. vii V. α-Arylation by Rearrangement: On the Reaction of Enolates with Diaryliodonium Salts Per-Ola Norrby, Tue B. Petersen, Marcin Bielawski and Berit Olofsson Chem. Eur. J. 2010 , 16 , 8251-8254. Copyright Wiley-VCH Verlag GmbH & Co. KGaA. Reproduced with permission. One-Pot Synthesis of Heteroaromatic Iodonium Salts Marcin Bielawski, Leticia M. Pardo, Ylva Wikmark and Berit Olofsson Appendix B. Paper not included in the thesis: Metal-Free Synthesis of Indanes by Iodine(III)-Mediated Ring Contraction of 1,2-Dihydronaphthalenes Fernanda A. Siqueira, Eloisa E. Ishikawa, André Fogaça, Andréa T. Faccio, Vânia M. T. Carneiro, Rafael R. S. Soares, Marcin Bielawski, Berit Olofsson and Luiz F. Silva, Jr. Submitted to Tetrahedron. viii Contents Abstract ......................................................................................................... v List of Publications .................................................................................... vii Contents ....................................................................................................... ix Abbreviations ............................................................................................... xi Chapter 1 Introduction to Hypervalent Iodine Compounds .............. 1 1.1 Nomenclature, Oxidation State and Bonding ................................................ 3 1.2 Some λ3- and λ5-Iodanes and their Applications .......................................... 4 1.3 Diaryliodonium Salts .......................................................................................... 5 1.3.1 Synthesis ..................................................................................................... 6 1.3.2 Mechanistic Limitations ............................................................................ 9 1.3.3 Application Areas ..................................................................................... 10 1.4 Objectives of This Thesis ................................................................................ 13 Chapter 2 One-Pot Synthesis of Diaryliodonium Triflates from Aryl Iodides and Arenes (Paper I & II) ................................................. 15 2.1 Initial Experiments ........................................................................................... 15 2.2 Optimization Studies ........................................................................................ 17 2.3 Arene Scope ...................................................................................................... 19 2.4 Aryl Iodide Scope ............................................................................................. 22 2.5 Limitations to the Developed Protocol .......................................................... 25 2.5.1 Electron-Rich Aryl Iodides ...................................................................... 25 2.5.2 Electron-Poor Arenes .............................................................................. 26 2.6 Conclusions ........................................................................................................ 27 Chapter 3 One-Pot Synthesis of Diaryliodonium Triflates from Iodine and Arenes (Paper I, II & III) .................................................... 29 3.1 Optimization ...................................................................................................... 29 3.2 Substrate Scope ............................................................................................... 31 3.3 Large Scale Synthesis ...................................................................................... 33 3.3.1 Selection of a Suitable Substrate ......................................................... 33 3.3.2 Scale-up, Isolation and Results ............................................................ 34 3.4 Conclusions ........................................................................................................ 37 ix Chapter 4 Regiospecific Synthesis of Diaryliodonium Tetrafluoroborates (Paper IV) ................................................................. 39 4.1 Initial Experiments ........................................................................................... 40 4.2 Optimization ...................................................................................................... 40 4.3 Arylboronic Acid Scope .................................................................................... 42 4.4 Aryl Iodide Scope ............................................................................................. 44 4.5 Conclusions ........................................................................................................ 46 Chapter 5 Synthesis of Heteroaromatic Iodonium Salts (Appendix B) ............................................................................................... 47 5.1 Initial Experiments and Optimization ........................................................... 48 5.2 Substrate Scope and the Identity of the Products ..................................... 48 5.3 Future Work and Conclusions ......................................................................... 53 Chapter 6 α-Arylation of Enolates by Rearrangement (Paper V) ..................................................................................................... 55 6.1 α-Arylation of Carbonyl Compounds ............................................................. 55 6.1.1 Aim of the Project .................................................................................... 58 6.2 Approaching α-Arylation– the Asymmetric Way ......................................... 58 6.2.1 α-Arylation with Diaryliodonium Salts having a Chiral Counterion
Load more

Recommended publications
  • Optimizing the Least Nucleophilic Anion. a New, Strong Methyl+ Reagent Daniel Stasko and Christopher A
    Published on Web 01/25/2002 Optimizing the Least Nucleophilic Anion. A New, Strong Methyl+ Reagent Daniel Stasko and Christopher A. Reed* Department of Chemistry, UniVersity of California, RiVerside, California 92521-0304 Received August 3, 2001 The ideal weakly coordinating counterion for reactive cations would be the least nucleophilic, least basic, most inert anion available. It should also be inexpensive, have useful spectroscopic handles, and confer good solubility and crystallizing properties on - its salts. Triflate anion, CF3SO3 , has served chemistry well in this regard but larger size, absence of lone pairs, and extreme chemical inertness have recently made carboranes1 or fluorinated tetraphe- nylborates the preferred choice for many applications.2 These anions have led to the solution of the silylium ion problem,3 enhanced Lewis acid catalysis by Li+ ion,4-6 new “strong-but-gentle” superacids,7 commercially viable olefin polymerization catalysts,8 new possibilities for electrolytes9,10 and ionic liquids,11 and the •+ 7 + 12 isolation of new reactive cations such as C60 , Bu3Sn , Cu- + 13 (CO)4 , etc. Figure 1. The 1-H-2,3,4,5,6-pentamethyl-7,8,9,10,11,12-hexahalo-CB11 - ) The perfluorinated tetraphenylborate anion is the preferred choice carborane anions, 1-H-CB11Me5X6 (X Cl, Br, I), used in this work. for price and solubility reasons but its salts frequently form liquid 29 Table 1. Selected Si Chemical Shifts (ppm) for i-Pr3SiY clathrates and fail to crystallize. The boron-phenyl bond is rather 29 easily cleaved by strong Brønsted14 or Lewis15 acids. Halogenated compd Si conditions carborane anions are much more inert than tetraphenylborates, their i-Pr3Si(1-H-CB11H5Br6) 100 C6D6 salts crystallize well, but they are more expensive and their salts i-Pr3Si(1-H-CB11H5Cl6) 103 C6D6 i-Pr Si(F -BPh )a 108 solid state less soluble.
    [Show full text]
  • Aldol Reactions: E-Enolates and Anti-Selectivity
    Utah State University DigitalCommons@USU All Graduate Plan B and other Reports Graduate Studies 5-2005 Aldol Reactions: E-Enolates and Anti-Selectivity Matthew Grant Anderson Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/gradreports Part of the Organic Chemistry Commons Recommended Citation Anderson, Matthew Grant, "Aldol Reactions: E-Enolates and Anti-Selectivity" (2005). All Graduate Plan B and other Reports. 1312. https://digitalcommons.usu.edu/gradreports/1312 This Report is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Plan B and other Reports by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. ALDOL REACTIONS: E-ENOLATES AND ANTI-SELECTIVITY Prepared By: MATTHEW GRANT ANDERSON A non-thesis paper submitted in partial fulfillment of the requirement for a Plan B Degree of Masters of Science in Organic Chemistry UTAH STATE UNIVERSITY Logan, Utah 2005 Contents Page CONTENTS ...................................................................................... .i LIST OF TABLES, FIGURES AND SCHEMES ....................................... ii,iii ABSTRACT .................................................................................... iv CHAPTER I. ALDOL REACTIONS:E-ENOLATES AND ANTI SELECTIVITY ......... 1 CHAPTER II. SECTION 1. MODELS OF E-ENOLATE FORMATION ...... .... ....... ... 12 SECTION 2. PATERSON ENOLATE PAPER ..... .........................
    [Show full text]
  • Probing Ion Exchange in the Triflic Acid-Guanidinium Triflate System: a Solid- State Nuclear Magnetic Resonance Study
    Probing ion exchange in the triflic acid-guanidinium triflate system: a solid- state nuclear magnetic resonance study Citation: Zhu, Haijin, MacFarlane, Douglas and Forsyth, Maria 2014, Probing ion exchange in the triflic acid-guanidinium triflate system: a solid-state nuclear magnetic resonance study, Journal of Physical Chemistry C, vol. 118, no. 49, pp. 28520-28526. This is the accepted manuscript. ©2014, American Chemical Society This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/jp5101472 Downloaded from DRO: http://hdl.handle.net/10536/DRO/DU:30070195 DRO Deakin Research Online, Deakin University’s Research Repository Deakin University CRICOS Provider Code: 00113B Page 1 of 19 The Journal of Physical Chemistry 1 2 3 4 Probing Ion Exchange in the Triflic Acid - Guanidinium Triflate System: a 5 6 Solid-State NMR Study 7 8 9 Haijin Zhu,*,a Douglas MacFarlaneb and Maria Forsytha 10 11 a Institute for Frontier Materials and the ARC Centre of Excellence for Electromaterials 12 Science, Deakin University, Geelong, VIC 3216, Australia. E-mail: [email protected]; 13 Fax: 61 (03) 92446868; Tel: +61 (03) 52273696 14 15 b Department of Chemistry and the ARC Centre of Excellence for Electromaterials 16 Science, Monash University, Clayton, VIC 3800, Australia 17 18 19 * Corresponding author, Tel: 61 (03) 52273696; Fax: 61 (03) 92446868; Email: 20 [email protected] (H.
    [Show full text]
  • (And In-Betweens) of Solubility Measurements of Solid Electrolytes*
    Pure Appl. Chem., Vol. 85, No. 11, pp. 2077–2087, 2013. http://dx.doi.org/10.1351/PAC-CON-12-11-06 © 2013 IUPAC, Publication date (Web): 20 May 2013 Some highs and lows (and in-betweens) of solubility measurements of solid electrolytes* Glenn Hefter Chemistry Department, Murdoch University, Murdoch, WA 6150, Australia Abstract: Recent solubility measurements of a variety of solid electrolytes in water and aque- ous solutions in the author’s laboratories are reviewed. The experimental challenge of per- forming such measurements with high accuracy is demonstrated using the solubility of solid sodium chloride in water at near-ambient temperatures as a paradigm. The special difficul- ties of measuring low solubilities are demonstrated using Pb(II) sulfate in various aqueous solutions and Pb(II) oxide in sodium hydroxide solutions, and the usefulness of such meas- urements for obtaining reliable information on homogeneous reactions in solution is briefly discussed. It is also shown, using the alkali metal triflate salts as examples, that determina- tion of the solubilities of even highly soluble salts can be problematic. Lastly, data for the sol- ubilities of a series of sodium carboxylate salts of industrial relevance are discussed and are used to illustrate why the theoretical prediction of solid electrolyte solubilities remains such a challenge. Keywords: aqueous solutions; carboxylate; electrolytes; lead(II); salts; sodium chloride; sol- ubility; triflate. INTRODUCTION The solubilities of substances in solvents are among the oldest of physicochemical measurements [1]. While they would not have been recognized as such at the time, these measurements certainly included the solubilities of solid electrolytes (“salts”) in water.
    [Show full text]
  • Catalytic Silane Nanopatterning Using Scandium Triflate Functionalised PPL Arrays
    Catalytic Silane Nanopatterning using Scandium Triflate Functionalised PPL Arrays A dissertation submitted to the University of Manchester for the degree of Master of Chemistry by Research in the Faculty of Science and Engineering 2017 David T. Arrowsmith School of Chemistry Table of Contents Title Page ....................................................................................................................................... 1 Table of Contents .......................................................................................................................... 2 Word Count .................................................................................................................................... 4 List of Figures ................................................................................................................................ 5 List of Schemes ............................................................................................................................. 7 List of Tables ................................................................................................................................. 8 List of Abbreviations ...................................................................................................................... 9 Abstract ........................................................................................................................................ 11 Declaration ..................................................................................................................................
    [Show full text]
  • Formal Synthesis of (+/-) Morphine Via an Oxy-Cope/Claisen/Ene Reaction Cascade
    Formal Synthesis of (+/-) Morphine via an Oxy-Cope/Claisen/Ene Reaction Cascade by Joel Marcotte Submitted to the Faculty of Graduate and Postdoctoral Studies In partial fulfillment of the requirements for the degree of Master of Science The University of Ottawa August, 2012 © Joel Marcotte, Ottawa, Canada, 2012 ABSTRACT For years now, opium alkaloids and morphinans have been attractive synthetic targets for numerous organic chemists due to their important biological activity and interesting molecular architecture. Morphine is one of the most potent analgesic drugs used to alleviate severe pain. Our research group maintains a longstanding interest in tandem pericyclic reactions such as the oxy-Cope/Claisen/ene reaction cascade and their application to the total synthesis of complex natural products. Herein we report the ventures towards the formal synthesis of (+/-)-morphine based on the novel tandem oxy- Cope/Claisen/ene reaction developed in our laboratory. These three highly stereoselective pericyclic reactions occurring in a domino fashion generate the morphinan core structure 2 via precursor 1 after only 7 steps. The formal synthesis culminated in the production of 3 after a total of 18 linear steps, with an overall yield of 1.0%, successfully intersecting two previous syntheses of the alkaloids, namely the ones of Taber (2002) and Magnus (2009). ii À ma famille, sans qui rien de cela n’aurait été possible iii ACKNOWLEDGEMENTS I would like to start by thanking my supervisor Dr. Louis Barriault, who has been my mentor in chemistry for the past three years. I am grateful for his guidance, patience and encouragements, especially when facing the many challenges that awaited me on this project.
    [Show full text]
  • Functional Group Interconversions 119
    FUNCTIONAL GROUP INTERCONVERSIONS 119 Functional Group Interconversions C&S Chapter 3 #1; 2; 4a,b, e; 5a, b, d; 6a,b,c,d; 8 1 sulfonates 2 halides 3 nitriles 4 azides 5 amines 6 esters and lactones 7 amides and lactams Sulfonate Esters - reaction of an alcohols (1° or 2°) with a sulfonyl chloride O R'= R'SO2Cl CH3 mesylate R OH R O S R' triflate O CF3 sulfonate ester CH3 tosylate - sulfonate esters are very good leaving groups. Elimination is often a competing side reaction Halides - halides are good leaving groups with the order of reactivity in SN2 reactions being I>Br>Cl. Halides are less reactive than sulfonate esters, however elimination as a competing side reaction is also reduced. - sulfonate esters can be converted to halides with the sodium halide in acetone at reflux. Chlorides are also converted to either bromides or iodides in the same fashion (Finkelstein Reaction). O X- R O S R' R X X= Cl, Br, I O NaI, acetone reflux R Cl R I - conversion of hydroxyl groups to halides: Organic Reactions 1983, 29, 1 R OH R X - R-OH to R-Cl - SOCl2 - Ph3P, CCl4 - Ph3P, Cl2 - Ph3P, Cl3CCOCCl3 FUNCTIONAL GROUP INTERCONVERSIONS 120 - R-OH to R-Br - PBr3, pyridine - Ph3P, CBr4 - Ph3P, Br2 - R-OH to R-I - Ph3P, DEAD, MeI Nitriles - displacement of halides or sulfonates with cyanide anion KCN, 18-C-6 DMSO R X R C N - dehydration of amides O R C N R NH2 - POCl3, pyridine - TsCl, pyridine - P2O5 - SOCl2 - Reaction of esters and lactones with dimethylaluminium amide TL 1979, 4907 Me H3C Me2AlNH2 OH JOC 1987, 52, 1309 O NC Ar O Ar - Dehydration of oximes OH N H2NOH•HCl P2O5 R CHO R C N R H - Oxidation of hydrazones O O N C Tetrahedron Lett.
    [Show full text]
  • Synthesis of Lycodine-Type Lycopodium Alkaloids Using C-H Functionalization Tactics by James Neel Newton a Dissertation Submitte
    Synthesis of Lycodine-Type Lycopodium Alkaloids Using C-H Functionalization Tactics by James Neel Newton A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Chemistry in the GRADUATE DIVISION of the UNIVERISTY OF CALIFORNIA, BERKELEY Committee in charge: Professor Richmond Sarpong, Chair Professor F. Dean Toste Professor Leonard Bjeldanes Spring 2015 Abstract Synthesis of Lycodine-Type Lycopodium Alkaloids Using C-H Functionalization Tactics By James Neel Newton Doctor of Philosophy in Chemistry University of California, Berkeley Professor Richmond Sarpong, Chair This dissertation describes our syntheses of several lycodine-type Lycopodium alkaloids by the late-stage C-H functionalization of lycodine derivatives. Lycodine-type alkaloids are well-known for their neurological activity. For example, huperzine A is a potent acetylcholinesterase inhibitor and the complanadine family of molecules has been shown to induce the secretion of Nerve Growth Factor. Due to these properties, lycodine-type alkaloids serve as interesting lead compounds for the development of new therapies for neurodegenerative disorders, such as Alzheimer’s disease. Unsurprisingly, these molecules have attracted the attention of the synthetic community. Chapter 1 reviews syntheses of lycodine-type Lycopodium alkaloids with particular emphasis on the syntheses of biologically active congeners. Chapter 2 describes our synthesis of complanadine B, an unsymmetrical dimer of lycodine, using two approaches. In the first, the requisite skeletal oxygenation was installed early in the synthetic sequence. Our second approach utilized a blocking group strategy to enable the late-stage oxygenation of the complanadine skeleton by preventing oxygenation at undesired sites. Chapter 3 describes our efforts toward the synthesis of the casuarinine family of Lycopodium alkaloids by the late-stage C-H functionalization of lycodine derivatives.
    [Show full text]
  • Synthesis of (+)-Lineariifolianone and Related Cyclopropenone- Containing Sesquiterpenoids Keith P
    Article Cite This: J. Org. Chem. 2019, 84, 5524−5534 pubs.acs.org/joc Synthesis of (+)-Lineariifolianone and Related Cyclopropenone- Containing Sesquiterpenoids Keith P. Reber,*,† Ian W. Gilbert,† Daniel A. Strassfeld,‡ and Erik J. Sorensen§ † Department of Chemistry, Towson University, Towson, Maryland 21252, United States ‡ Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States § Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States *S Supporting Information ABSTRACT: A synthesis of the proposed structure of lineariifolianone has been achieved in eight steps and 9% overall yield starting from (+)-valencene, leading to a reassignment of the absolute configuration of this unusual cyclopropenone-containing natural product. Key steps in the synthetic route include kinetic protonation of an enolate to epimerize the C7 stereocenter and a stereoconvergent epoxide opening to establish the trans-diaxial diol functionality. The syntheses of the enantiomers of two other closely related natural products are also reported, confirming that all three compounds belong to the eremophilane class of sesquiterpenoids. ■ INTRODUCTION derivatives,10 and the parent compound has even been 11 Plants of the genus Inula have been widely used in traditional detected in interstellar space. Chinese medicine for their anti-inflammatory properties and to Natural products containing the cyclopropenone group are 1 quite rare, and to date only six other examples have been treat bacterial infections. In 2010, Zhang and Jin reported the 12 isolation of the sesquiterpenoid lineariifolianone (1), which isolated (Figure 2). Penitricin (2) and alutacenoic acids A was obtained from the aerial parts of the flowering plant Inula lineariifolia (Figure 1).2 The structure of this natural product Downloaded via TOWSON UNIV on July 13, 2020 at 20:20:52 (UTC).
    [Show full text]
  • A Convenient Synthesis of Triflate Anion Ionic Liquids and Their Properties
    Molecules 2012, 17, 5319-5338; doi:10.3390/molecules17055319 OPEN ACCESS molecules ISSN 1420-3049 www.mdpi.com/journal/molecules Article A Convenient Synthesis of Triflate Anion Ionic Liquids and Their Properties Nikolai V. Ignat’ev 1,*, Peter Barthen 2, Andryi Kucheryna 3, Helge Willner 3 and Peter Sartori 4 1 Merck KGaA, PM-ABE, Ionic Liquids Research Laboratory, Frankfurter Str. 250, Darmstadt D-64293, Germany 2 Inorganic Chemistry, Henrich-Heine-University Düsseldorf, Universitätsstrasse 1, Düsseldorf D-40225, Germany; E-Mail: [email protected] 3 Inorganic Chemistry, Bergische University Wuppertal, Gauss Str. 20, Wuppertal D-42119, Germany; E-Mails: [email protected] (A.K.); [email protected] (H.W.) 4 Professor Emeritus, Inorganic Chemistry, University Duisburg-Essen, Lotharstrasse 1, Duisburg D-47048, Germany; E-Mail: [email protected] * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +49-151-1454-3102; Fax: +49-6151-728-587. Received: 7 March 2012; in revised form: 13 April 2012 / Accepted: 13 April 2012 / Published: 7 May 2012 Abstract: A solvent- and halogen-free synthesis of high purity triflate ionic liquids via direct alkylation of organic bases (amines, phosphines or heterocyclic compounds) with methyl and ethyl trifluoromethanesulfonate (methyl and ethyl triflate) has been developed. Cheap and non-toxic dimethyl and diethyl carbonate serve as source for the methyl and ethyl groups in the preparation of methyl and ethyl triflate by this invented process. The properties of ionic liquids containing the triflate anion are determined and discussed. Keywords: methyl triflate; ethyl triflate; ionic liquids; viscosity 1.
    [Show full text]
  • Enolate Chemistry
    Prof. Dr. Burkhard König, Institut für Organische Chemie, Uni Regensburg 1 Enolate Chemistry 1. Some Basics In most cases the equilibrium lies almost completely on the side of the ketone. The ketone tautomer is electrophilic and reacts with nucleophiles: The enol tautomer is nucleophilic and reacts with electrophiles. There are two possible products - enols are ambident nucleophiles: The nucleophilic enol tautomer (and especially the enolate variant) is one of the most important reactive species for C-C bond formation. Treat a ketone with an appropriate base and can get deprotonation at the α-position to form an enolate: Enolates are synthetically much more useful than enols (although they react analogously). Imine anions and eneamines are synthetic equivalents of enolate anions. Li N N H H Imine anion eneamine By knowing the pKa values of the relevant acidic protons it is possible to predict suitable bases for forming the corresponding enolates. Prof. Dr. Burkhard König, Institut für Organische Chemie, Uni Regensburg 2 Some Important pKa Values - - - O O HC N HC3 NO2 H2CN+ 2 + O O pKa ~ 10 - Enolates are nucleophiles and ketones are electrophiles - therefore there is always the potential problem for self condensation. If this is desirable we need to use a base which does not completely deprotonate the carbonyl compound i.e. set up an equilibrium. This is best achieved when the pKa of the carbonyl group and conjugate acid (of the base) are similar: Prof. Dr. Burkhard König, Institut für Organische Chemie, Uni Regensburg 3 pKa (tBuOH) ~ 18. A stronger base. pKa difference of 2. Ratio of ketone to enolate will be of the order 100:1 i.e.
    [Show full text]
  • Boron Enolate of Tert-Butyl Methyl Ketone
    5834 Organometallics 2007, 26, 5834-5839 Synthesis and Structural Characterization of the Bis(diisopropylamino)boron Enolate of tert-Butyl Methyl Ketone Lili Ma,† Russell Hopson,† Deyu Li,† Yong Zhang,‡ and Paul G. Williard*,† Department of Chemistry, Brown UniVersity, ProVidence, Rhode Island 02912 and Department of Chemistry, Boston UniVersity, 590 Commonwealth AVenue, Boston, Massachusetts 02215 ReceiVed July 5, 2007 Lithium, sodium, and potassium enolates reacted with bisaminoboron halides to give bisaminoboron enolates 1a-5c. Specifically, the potassium enolate of tert-butyl methyl ketone reacted with bis- (diisopropylamino)boron chloride in THF at room temperature within1htogive the bis(diisopropylamino)- boron enolate of tert-butyl methyl ketone (3b)in61-84% isolated yields. Under similar conditions, the reactivity is highly dependent on the metal employed to generate enolates (K > Na > Li) as well as the nitrogen substituents in the bisaminoboron halides (iPr > Et > TMS). This latter observation is a compromise between the boron-nitrogen resonance and the steric effect. The structural information of enolate 3b was studied in detail. Unlike the aggregated alkali-metal enolates, this boron enolate exists exclusively as a monomer in both the solid and solution states, as identified by X-ray and diffusion- ordered NMR. Introduction Table 1. Conditions for Bisaminoboron Enolates from Bisaminoboron Chlorides and Metal Enolates Boron enolates enjoy widespread use in synthetic organic chemistry due to the relatively mild conditions used to generate these intermediates and the stereoselectivity observed in both the enolization reaction and the subsequent aldol reactions.1 The most widely utilized asymmetric synthetic methodology involv- ing boron enolates developed from the extensive studies of Evans and co-workers beginning 30 years ago.2 H.
    [Show full text]