DOCSLIB.ORG

Phase Transfer Catalysis of Henry and Darzens Reactions

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Phase Transfer Catalysis of Henry and Darzens Reactions International Journal of Organic Chemistry, 2011, 1, 119-124 doi:10.4236/ijoc.2011.13018 Published Online September 2011 (http://www.SciRP.org/journal/ijoc) Phase Transfer Catalysis of Henry and Darzens Reactions Layla Mhamdi1, Hafedh Bohli1, Younes Moussaoui1,2, Ridha ben Salem1* 1Physical Organic Chemistry Laboratory, Science Faculty of Sfax, Sfax University, Sfax, Tunisia 2Science Faculty of Gafsa, Gafsa University, Zarroug City, Gafsa, Tunisia E-mail: [email protected], [email protected] Received April 28, 2011; revised June 23, 2011; accepted August 16, 2011 Abstract We describe in this work the influence of the addition of phase transfer catalyst in heterogeneous medium liquid/liquid on the output of the reactions of Darzens and Henry. It proves that the reaction of Darzens is favoured in the presence of low base such as K2CO3 and Et3N. Phase transfer catalysis is an efficient activa- tion method in Darzens and Henry reactions. Thus, the Ethylene Diammonium Diacetate (EDD) has a com- parable catalytic activity has that of quaternary ammonium salts in the reaction of Darzens. Keywords: Darzens, Henry, Phase Transfer Catalysis, Mechanism 1. Introduction group [28] introduced a phase transfer catalyst derived from cinchonine to synthetize Darzens products. In the The formation of a carbon-carbon bond is the fundamen- same way, Ku et al. [29] reported the asymmetric syn- tal reaction in organic synthesis [1-5]. To this respect, thesis of trans-α,β-epoxysulfones by the catalytic phase- Henry [6-9] and Darzens [10-12] reactions can be con- transfer Darzens reaction of chloromethyl phenyl sulfone sidered as excellent tools to give access to multifunc- with various aromatic aldehydes in the presence of the tional compounds [13,14]. The Darzens reaction gives cinchona alkaloid-derived chiral phase-transfer catalysts. α,β-epoxy carbonyl compounds, whereas the Henry reac- In the goal to continue our works on the activation by tion leads to nitroaldols. the phase transfer catalysis of organic reactions such as: The Henry reaction [15] consists of the addition of a Wittig reaction [30], Baylis-Hillman reaction [31,32], nitronate nucleophile on the double bond of a carbonyl Michael reaction [32,33], Knoevenagel reaction [34], compound. It proceeds usually at room temperature in Heck reaction [35,36]. In this work, we study the activa- the presence of a base to afford a β-nitroalcool. The pre- tion of Henry and Darzens reactions by means of phase ferred bases are alcali hydroxides [16], carbonates [17], transfer catalysis (PTC). bicarbonates [18] and alkali oxides. The reaction, how- ever, is often carried out in protic media such as metha- 2. Experimental nol or, even, water [19]. Henry adducts are very useful in organic synthesis as precursors for pharmaceutical and 2.1. Henry Reaction biological purposes [20,21]. In order to improve the effi- ciency of the reaction, new catalytic or non-catalytic Procedure A: A solution of nitroalkane (7.5 mmol), methods have been divised such as alumina [22], potas- solvent (15 mL), and base (5 mmol) was introduced in a sium fluoride on alumina as support [23], lanthanides 25 mL flask equipped with a magnetic stirrer. 5 mmol of [24], high pressures [25] and microwaves [26]. In the carbonyl compound was added. The mixture was stirred same way, the Darzens reaction permits the synthesis of during 24 h at ambient temperature. The organic phase adducts simultaneously involving the formation of a was extracted with diethyl ether. When the carbonyl carbon-carbon bond and a carbon-oxygen bond [12]. compound was an aldehyde, the organic phase was wash- Several authors have tried to improve the enantioselec- ed with a saturated solution of anhydrous sodium hydro- tivity and the yields. Arai et al. [27] showed that the en- genosulfite to remove the unreacted aldehyde. The or- antioselectivity of the Darzens reaction can be excellent ganic phase was dried over anhydrous sodium sulphate. when using a chiral auxiliary such as cinchonine, an al- After evaporation of the solvent the product was purified caloid structurally close to quinine. Later on, the same on silicagel column chromatography with hexane-ether Copyright © 2011 SciRes. IJOC 120 L. MHAMDI ET AL. mixtures as eluent. reaction involving benzaldehyde and various nitroal- Procedure B: As procedure A with addition of 2 kanes in aqueous solution (Table 1). mmol of the phase transfer catalyst. Inspection of the results of Table 1 shows that the re- activity is modest in the presence of bases such as 2.2 Darzens Reaction triethylamine and weak in the presence of carbonate anions such as K2CO3. There is no reaction with sodium Procedure C: A solution of α-chloroester or α-chl- alcoolates. oroaacid or α-chloronitrile (3.6 mmol), solvent (15 mL), This may be explained by the formation of secondary base (3.6 mmol) was introduced in a 25 mL flask eq- products issued from Cannizzaro reactions or hydrolysis uipped with a magnetic stirrer. 3 mmol of carbonyl com- in the presence of alcoolates on the contrary of reactions pound was added. The mixture was stirred during 24h at involving triethylamine or alkali carbonates. The results ambient temperature. The organic phase was extracted are in agreement with those of Zhou et al. [39] who with diethyl ether and dried over anhydrous sodium sul- found that Henry reaction of aromatic and aliphatic al- phate. After evaporation of the solvent the product was dehydes with nitromethane is promoted by triethylamine purified on silicagel column chromatography with hex- in water.(Figure 1.) ane-ether mixtures as eluent. Effect of the carbonyl compound: Procedure D: As procedure C with tetrahydrofurane The effect of the carbonyl compound was studied in a as solvent and potassium hydroxide as the base with ad- next step using nitromethane and various carbonyl com- dition of 2mmol of the phase transfer catalyst. pounds (Figure 2, Table 2). 2.3. Synthesis of Ethylene Diammonium As shown in Table 2, the reaction does not occur with Diacetate (EDD) ketones. Apparently this is due to the very weak reactiv- ity of ketones toward the carbanion formed by deproto- Ethylene diamine (3 g) in anhydrous diethylether was nation of nitromethane. Steric effects and the positive in- introduced in a 50mL flask. The flask was immersed into ductive effect lead in the case of ketones to a reduction a liquid bath maintained at 35˚C. Then, glacial acetic acid (6 g) was added. The mixture was stirred until boil- Table 1. Effect of the base in the Henry reaction. ing of ether. After 24 h cristallization occurred. The solid R1 R2 Product Base Yield (%) product was filtered and washed with ether. Finally, it CH3ONa 0 EtONa 0 was recrystallized in methanol. H 1a Et3N 46 K2CO3 21 2.4. Recording of Spectra CH3ONa 0 EtONa 0 1 13 H CH3 1b H (300 MHz) and C (75 MHz) NMR spectra are re- Et3N 42 K2CO3 18 corded on a Bruker spectrometer in DMSO-d6, with CH3ONa 0 tetramethysilane as internal reference. EtONa 0 C2H5 1c The products were analysed by GC-MS (Hewlett- Et3N 47 Packard computerised system consisting of a 5890 gas K2CO3 24 chromatograph coupled to a 5971A mass spectrometer) CH3ONa 0 EtONa 0 ionisation mode used was electronic impact at 70 eV. CH3 CH3 1d Microanalyses were performed using a C, H, N Ana- Et3N 32 K2CO3 17 lyzer Model 185 from Hewlett-Packard. I.R. spectra are Procedure A recorded in KBr on a Bruker Tensor 27 spectrometer in –1 the range 4000 - 400 cm . R1 R1 Base (1eq) All the products were confirmed by comparing their C H CHO + CH NO C H CH C NO 1 13 6 5 2 6 5 2 IR, MS, H NMR and C NMR data with literature data H2O ; 25°C ; 24h 2 2 [9,10,12,37,38]. R OH R Figure 1. Henry reaction of benzaldehyde with nitroalkane. 3. Results and Discussion 1 O R Et N (1eq) 3 2 C + H3CNO2 R C CH2 NO2 3.1. Henry Reaction H O ; 25°C ; 24h R1 R2 2 OH Effect of the base: Figure 2. Henry reaction of nitromethane with carbonyl We have examined the nature of the base in the Henry compound. Copyright © 2011 SciRes. IJOC L. MHAMDI ET AL. 121 Table 2. Effect of the carbonyl compound in the Henry re- the structure of the alkyl or aryl groups on the nitrogen action. atom and, also, on the nature of the counter-ion. It may R1 R2 Product Yield (%) also be noticed that the presence of a lipophilic group H C6H5 1a 46 (this is the case of Aliquat-336) is beneficial for the for- H C3H7 1e 48 mation of the Henry adduct as it facilitates the nucleo- H Cl-C6H4 1f 54 CH3 C2H5 1g 0 philic attack on the aldehyde [31]. CH3 C6H5 1h 0 4) At last, the yield depends on the nature of the anion -(CH2)5- 1i 0 associated with the ammonium cation. It is higher with -(CH ) - 1j 0 2 4 tetrabutylammonium chloride than with the correspond- Procedure A. ing bromide. The same result was also found by D’Incan in his study examining the effect of the phase transfer of the electrophilicity of the carbon in the carbonyl group. agent on the Horner-Emmons reaction between benzal- This makes the attack of the resulting carbanion more dehyde and 1-cyanoethyl diethyphosphonate [40]. difficult. We propose the following mechanism of the Henry Effect of phase transfer catalysis: reaction involving benzaldehyde and nitromethane under In the following step we examined the nature of the PTC conditions (Figure 4). phase transfer catalyst in Henry reactions involving various aldehydes and ketones.(Figure 3.) 3.2.
Load more

Recommended publications
  • The Chemistry of 3-Acetyl-3, 4-Phenacylidenecoumarin Gerald Eugene Risinger Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1961 The chemistry of 3-acetyl-3, 4-phenacylidenecoumarin Gerald Eugene Risinger Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons Recommended Citation Risinger, Gerald Eugene, "The chemistry of 3-acetyl-3, 4-phenacylidenecoumarin " (1961). Retrospective Theses and Dissertations. 1983. https://lib.dr.iastate.edu/rtd/1983 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been 62-1367 microfilmed exactly as received RISINGER, Gerald Eugene, 1932- THE CHEMISTRY OF 3-ACETYL-3,4-PHENACYLI- DENECOUMARIN. Iowa State University of Science and Technology Ph.D., 1961 Chemistry, organic University Microfilms, Inc., Ann Arbor, Michigan THE CHEMISTRY OF 3-ACETYL-3 , ^-PI-ENACYLIDENECOUKARIN by Gerald Eugene Risinger A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject : Organic Chemistry Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. head of Major Department Signature was redacted for privacy. Iowa State University Of Science and Technology Ames, Iowa 1961 il TABLE OF CONTENTS PAGE I INTRODUCTION 1 II HISTORICAL 2 III DISCUSSION 49 IV SPECTRA 87 V EXPERIMENTAL 100 VI SUMMARY 116 VII LITERATURE CITED .
    [Show full text]
  • Design, Synthesis and Testing of New Chiral Sulfide Catalysts for Corey- Chaykovsky Reaction
    DESIGN, SYNTHESIS AND VESA TESTING OF NEW CHIRAL MYLLYMÄKI SULFIDE CATALYSTS FOR Department of Chemistry, COREY-CHAYKOVSKY University of Oulu REACTION OULU 2001 VESA MYLLYMÄKI DESIGN, SYNTHESIS AND TESTING OF NEW CHIRAL SULFIDE CATALYSTS FOR COREY- CHAYKOVSKY REACTION Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, for public discussion in Raahensali (Auditorium L10), Linnanmaa, on December 5th, 2001, at 12 noon. OULUN YLIOPISTO, OULU 2001 Copyright © 2001 University of Oulu, 2001 Manuscript received 16 November 2001 Manuscript accepted 19 November 2001 Communicated by Professor Liisa Kanerva Professor Tapio Hase ISBN 951-42-6571-8 (URL: http://herkules.oulu.fi/isbn9514265718/) ALSO AVAILABLE IN PRINTED FORMAT ISBN 951-42-6570-X ISSN 0355-3191 (URL: http://herkules.oulu.fi/issn03553191/) OULU UNIVERSITY PRESS OULU 2001 Myllymäki, Vesa, Design, synthesis and testing of new chiral sulfide catalysts for Corey-Chaykovsky reaction Department of Chemistry, University of Oulu, P.O.Box 3000, FIN-90014 University of Oulu, Finland 2001 Oulu, Finland (Manuscript received 16 November 2001) Abstract The first part of this monograph discusses the asymmetric, ylide based, reagent controlled epoxidations. Both different chiral ylides and epoxidation processes, stoichiometric and catalytic, are reviewed. In the following part, new chiral sulfide catalysts were discovered as enantioselective catalysts for the Corey-Chaykovsky reaction (epoxidation of aldehydes via sulfonium ylides). Using a crystal structure of an oxazolidine derivative as a starting point, a thiazolidine ligand family was designed, synthesized and finally employed as catalysts in the asymmetric epoxidation of benzaldehyde. The ligands were prepared starting from L-valine, L-tert-leucine, D-penicillamine and L-cysteine.
    [Show full text]
  • The Anti Selective Aldol Addition of Ketones to Aldehydes Via N-Amino Cyclic
    The Anti Selective Aldol Addition of Ketones to Aldehydes via N-Amino Cyclic Carbamate Chiral Auxiliaries and the Asymmetric Total Synthesis of (+)- and (-)- Mefloquine Hydrochloride by John Derrick Knight Department of Chemistry Duke University Date:_______________________ Approved: ___________________________ Don M. Coltart, Co-Supervisor ___________________________ Steven W. Baldwin, Co-Supervisor ___________________________ Jiyong Hong ___________________________ Dewey G. McCafferty Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry in the Graduate School of Duke University 2012 ABSTRACT The Anti Selective Aldol Addition of Ketones to Aldehydes via N-Amino Cyclic Carbamate Chiral Auxiliaries and the Asymmetric Total Synthesis of (+)- and (-)- Mefloquine Hydrochloride by John Derrick Knight Department of Chemistry Duke University Date:_______________________ Approved: ___________________________ Don M. Coltart, Co-Supervisor ___________________________ Steven W. Baldwin, Co-Supervisor ___________________________ Jiyong Hong ___________________________ Dewey G. McCafferty An abstract of a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry in the Graduate School of Duke University 2012 Copyright by John Derrick Knight 2012 Abstract In the first part of this dissertation, the first asymmetric anti selective aldol addition of a ketone-derived donor that is independent of the structure of the ketone is described. This transformation is facilitated by the use of chiral N-amino cyclic carbamate (ACC) auxiliaries. Under certain conditions, this transformation not only exhibits near perfect anti selectivity and enantioselectivity but also does so via thermodynamic control. Simple manipulation of the reaction conditions allows for the O-benzylation of the prepared aldol products and the subsequent removal of the ACC auxiliary to give the β-benzyloxy ketone.
    [Show full text]
  • Asymmetric Synthesis of Spirooxindoles Via Nucleophilic Epoxidation Promoted by Bifunctional Organocatalysts
    molecules Article Asymmetric Synthesis of Spirooxindoles via Nucleophilic Epoxidation Promoted by Bifunctional Organocatalysts Martina Miceli 1, Andrea Mazziotta 1, Chiara Palumbo 1, Elia Roma 1, Eleonora Tosi 1, Giovanna Longhi 2 ID , Sergio Abbate 2, Paolo Lupattelli 3, Giuseppe Mazzeo 2 ID and Tecla Gasperi 1,* ID 1 Dipartimento di Scienze- Sezione di Nanoscienze e Nanotecnologie, Università degli Studi di Roma Tre, V.le G. Marconi 446, I-00146 Rome, Italy; [email protected] (M.M.); [email protected] (A.M.); [email protected] (C.P.); [email protected] (E.R.); [email protected] (E.T.) 2 Dipartimento di Medicina Molecolare e Traslazionale (DMMT), Università di Brescia, viale Europa 11, 25123 Brescia, Italy; [email protected] (G.L.); [email protected] (S.A.); [email protected] (G.M.) 3 Dipartimento di Scienze, Università degli Studi della Basilicata, via dell0Ateneo Lucano 10, I-85100 Potenza, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-3386711045 Received: 5 February 2018; Accepted: 12 February 2018; Published: 16 February 2018 Abstract: Taking into account the postulated reaction mechanism for the organocatalytic epoxidation of electron-poor olefins developed by our laboratory, we have investigated the key factors able to positively influence the H-bond network installed inside the substrate/catalyst/oxidizing agent. With this aim, we have: (i) tested a few catalysts displaying various effects that noticeably differ in terms of steric hindrance and electron demand; (ii) employed α-alkylidene oxindoles decorated with different substituents on the aromatic ring (11a–g), the exocylic double bond (11h–l), and the amide moiety (11m–v).
    [Show full text]
  • Enantioselective Epoxidation Reactions Using Chiral Ammonium Salts
    JOHANNES KEPLER UNIVERSITÄT LINZ JKU Faculty of Engineering and Natural Sciences Enantioselective epoxidation reactions using chiral ammonium salts Master‘s Thesis to confer the academic degree of Diplom-Ingenieurin in the Master‘s program Technical Chemistry Submitted by: Katharina Zielke At the: Institute of Organic Chemistry Advisor: Assoc. Univ.-Prof. Dr. Mario Waser Linz, October 2015 1 Contents Eidesstattliche Erklärung 5 Acknowledgements 6 Curriculum Vitae 7 Abstract 9 Zusammenfassung 10 1 Introduction 11 1.1 Epoxides ..................................... 11 1.2 Epoxides from alkenes ............................. 11 1.2.1 Prilezhaev epoxidation ......................... 12 1.2.2 Sharpless epoxidation ......................... 13 1.2.3 Jacobsen-Katsuki epoxidation ..................... 15 1.2.4 Shi asymmetric epoxidation ....................... 17 1.3 Epoxides from carbonyl compounds ...................... 18 1.3.1 The Darzens glycidic ester condensation ............... 19 1.3.2 The Corey-Chaykovsky reaction .................... 20 1.3.2.1 Diastereoselectivity in Sulfur-ylide-mediated reactions . 21 1.3.2.2 Enantioselectivity in sulfur-ylide-mediated reactions ..... 23 1.3.2.3 Catalytic use of sulfur ylides ................. 24 1.4 Ammonium ylides in epoxidation reactions ................... 27 1.4.1 Investigations by Jonczyk et al. and Kimachi et al. .......... 27 1.4.2 Diastereoselectivity in reactions of ammonium ylides with aldehydes 29 2 Results and Discussion 30 2.1 Motivation of this work .............................. 30 2.2 Previous experiments from our group members ................ 30 2.3 DABCO-derived chiral ammonium acetamides ................ 33 2.3.1 Reactions using the DABCO-derivative 62 ............... 33 2.3.2 Reactions using the camphor-derivative 68 .............. 34 2 2.4 Proline-derived chiral ammonium acetamides ................. 35 2.4.1 Synthesis of different proline-based ammonium salts and their use .
    [Show full text]
  • Catalytic, Asymmetric Sulfur Ylide-Mediated Epoxidation of Carbonyl Compounds: Scope, Selectivity, and Applications in Synthesis VARINDER K
    Acc. Chem. Res. 2004, 37, 611-620 Catalytic, Asymmetric Sulfur Ylide-Mediated Epoxidation of Carbonyl Compounds: Scope, Selectivity, and Applications in Synthesis VARINDER K. AGGARWAL* AND FIGURE 1. CAROLINE L. WINN While there are many examples of the two-step process School of Chemistry, Cantock's Close, University of Bristol, involving a Wittig reaction followed by asymmetric oxida- Bristol BS8 1TS, U.K. tion, the one-step sulfur ylide route had not been widely Received December 8, 2003 used. We felt that if we could render the process both catalytic and asymmetric, the advantages of the new one- step route could begin to compete with the more tradi- ABSTRACT The reaction of sulfur ylides with carbonyl compounds to give tional oxidative approach. epoxides is an important synthetic method. This Account charts the recent advances in rendering this process both asymmetric and catalytic. Two catalytic methods have been developed: the first Introduction to Sulfur Ylide-Mediated involving the reaction of a sulfide with an alkyl halide in the Epoxidation presence of a base and aldehyde and the second involving the Johnson reported the first literature example of a sulfur reaction of a sulfide with a diazo compound or diazo precursor in 6 the presence of a metal catalyst and aldehyde. These catalytic ylide-mediated epoxidation reaction in 1958. Reaction of methods coupled with suitable chiral sulfides provide a new the stable and isolable 9-dimethylsulfonium fluorenylide catalytic asymmetric epoxidation process for the preparation of 1 (Figure 2) with 4-nitrobenzaldehyde did not afford an epoxides. The scope of the two catalytic processes is discussed alkene, which had been expected on the basis of the together with the factors that influence both relative and absolute stereochemistry.
    [Show full text]
  • Specialization: Applied Chemistry)
    Central University of Punjab Bathinda M.Sc. Chemistry (Specialization: Applied Chemistry) Session: 2020-22 Department of Chemistry School of Basic and Applied Sciences Program Outcomes Upon successful completion of the course work, student will be able to equip with state of art of knowledge of different areas of chemistry develop the employability skills required for chemical industry and pharmaceutical companies 1 SEMESTER-I S. Paper Course Title Course L T P Cr No. Code Type 1 CHM.509 Inorganic Chemistry-1 CC 3 0 0 3 2 CHM.510 Organic Chemistry-I CC 4 0 0 4 3 CHM.511 Physical Chemistry-I CC 3 0 0 3 4 CHM.512 Quantum Chemistry CC 3 0 0 3 5 CAC.513 Applied Practical Inorganic SB 0 0 4 2 Chemistry-I 6 CAC.514 Applied Practical Organic SB 0 0 4 2 Chemistry-I 7 CHM.506 Fundamental Biology (Non-medical CF group) 2 0 0 2 8 CHM.507 Fundamental Mathematics (Medical group) Opt any one of the following elective/MOOC courses 9 CHM.508 Analytical Chemistry and EC 4 0 0 4 Instrumental Methods 10 CHM.577 Environmental Chemistry 4 0 0 4 11 CHM.520 Green Chemistry 4 0 0 4 12 CAC.541 Seminar SB 1 0 0 1 13 XXX Inter-Disciplinary Course ID (Departments) 2 0 0 2 Total 22 0 8 26 Inter-Disciplinary Course for other Departments 14 CHM.515 Basics perspective in Inorganic ID 2 0 0 2 Chemistry 15 CHM.516 Introduction to Green Chemistry ID 2 0 0 2 and Sustainability 16 CHM.519 Chemicals of Everyday Life ID 2 0 0 2 CC: Core Course, EC: Elective Course, CF: Compulsory Foundation, EF: Elective Foundation, SB: Skill Based L: Lectures T: Tutorial P: Practical Cr: Credits Criteria for evaluation of theory exams: Internal 75% (Quiz – 10%, Assignment and Term Paper – 15%, MST – 25%, EST I- 25%); EST II- 25%.
    [Show full text]
  • Darzens Reaction
    Darzens reaction The Darzens reaction (also known as the Darzens condensation or glycidic ester Darzens reaction condensation) is the chemical reaction of a ketone or aldehyde with an α-haloester in the Named after Auguste Georges presence of a base to form an α,β-epoxy ester, also called a "glycidic ester".[1][2][3] This Darzens reaction was discovered by the organic chemist Auguste Georges Darzens in 1904.[4][5][6] Reaction type Ring forming reaction Identifiers Organic darzens-reaction Chemistry Portal RSC ontology RXNO:0000077 ID Contents Reaction mechanism Stereochemistry Alternative reactions Subsequent reactions See also References Reaction mechanism The reaction process begins when a strong base is used to form a carbanion at the halogenated position.[3] Because of the ester, this carbanion is a resonance-stabilized enolate, which makes it relatively easy to form. This nucleophilic structure attacks another carbonyl component, forming a new carbon–carbon bond. These first two steps are similar to a base-catalyzed aldol reaction. The oxygen anion in this aldol-like product then does an intramolecular SN2 attack on the formerly-nucleophilic halide-bearing position, displacing the halide to form an epoxide.[2] This reaction sequence is thus a condensation reaction since there is a net loss of HCl when the two reactant molecules join. The primary role of the ester is to enable the initial deprotonation to occur, and other carbonyl functional groups can be used instead. If the starting material is an α-halo amide, the product is an α,β-epoxy amide.[7] If an α-halo ketone is used, the product is an α,β- epoxy ketone.[2] Any sufficiently strong base can be used for the initial deprotonation.
    [Show full text]
  • CY-101 : Stoichiometry, Solutions and Gases (3 Credits)
    CY-101 : Stoichiometry, Solutions and Gases (3 credits) Prerequisite : None Experimental evidence for the atomic hypothesis. Chemical compounds and their composition - introduction to nomenclature. Chemical reactions and stoichiometric calculations. (8 h) Solution chemistry - electrolytes and non-electrolytes. Colligative properties. Ideal and non-ideal solutions. Reactions in solution - redox, acid-base, precipitation, ionexchange. Colloids. (14 h) Properties of gases - Avogadro's hypothesis, the ideal gas law. Kinetic molecular theory. Gas mixtures. Solubility of gases. Gases at high pressure and low temperatures - critical phenomena. (14 h) Suggested reading : Will be prescribed by the instructor. CY-102 : Qualitative Analysis Lab. (1.5 credits) Prerequisite : None Reactions of common cations and anions. Semimicro analysis of mixtures. Suggested reading : Lab Manual CY-151 : Energetics and kinetics (3 credits) Prerquisite : None Thermochemistry - enthalpy and enthalpy change - calorimetry - enthalpies of formation and of reactions. Entropy and free energy. State functions. (8 h) Chemical kinetics - reaction rates - effect of concentration and temperatures. Steady state approximation. Reaction mechanism from rate laws. (8 h) Chemical equilibrium in the gas phase - equilibrium constants and their relation to free energy - temperature dependence. (6 h) Equilibrium in the aqueous phase - pH, buffers and indicators - complex ions. Heterogeneous equilibria - adsorption. (6 h) Electrochemistry - voltage and free energy - standard potentials
    [Show full text]
  • The Chemistry of the Carbonyl Group
    THE CHEMISTRY OF THE CARBONYL GROUP Professor Tim Donohoe 8 lectures, HT, weeks 1-4, 2006 Handout B O NC O CN R R R R O O H OH You will be able to download copies of the handouts from this course at http://users.ox.ac.uk/%7Emagd1571/finalpage/teaching.html 1 4) Enolisation of carbonyl compounds A) keto-enol tautomerism If one looks at the NMR spectrum of dimedone, it contains peaks for TWO different compounds. O O HO O The two forms of dimedone are known as the keto and They are known as TAUTOMERS (isomers that are interchangeable via the transfer of a proton): and the process of exchange between them is called However, if we look at the NMR spectra of simple aldehydes and ketones they have % enol in neat liquid % enol in neat liquid O O O O O O OEt If we look at the bond strengths, we can see why Sum (KJMol-1) Keto (C-H) (C=O) Enol (C-H) (C=C) 2 Clearly, the presence of extra conjugation in the enol form is enough O O O O Another factor There is another way that we can detect the presence of enols in aldehydes and ketones. When acetone is dissolved in D2O it becomes CD3COCD3 over a long period of time: moreover, this reaction is catalysed by both This process occurs through IN BASE O O IN ACID O O 3 + Q. What would happen to CH3CH2COCH2CH2Ph in D2O with cat. H ? Think of a carbonyl compound that exists in 100% enol form? Remember that th acid (or base) speeds up the rate at which the reaction proceeds ie equilibrium is reached, it does NOT ENOLATES You have just seen that protons adjacent to a carbonyl are acidic: quantify this property by O O Cl OMe O O H NMe2 O Obviously, two carbonyl groups in a 1-3 array activate the protons in between even more.
    [Show full text]
  • 2012 Book Halogenatedhetero
    27 Topics in Heterocyclic Chemistry Series Editor: Bert U. W. Maes Editorial Board: J. Cossy l D. Enders l S.V. Ley l G. Mehta l K.C. Nicolaou l R. Noyori l L.E. Overman l A. Padwa l S. Polanc Topics in Heterocyclic Chemistry Series Editor: Bert U.W. Maes Recently Published and Forthcoming Volumes Halogenated Heterocycles Bioactive Heterocycles VI Volume Editor: J. Iskra Flavonoids and Anthocyanins in Plants, Volume 27, 2012 and Latest Bioactive Heterocycles I Volume Editor: N. Motohashi Heterocyclic Scaffolds II: Reactions Volume 15, 2008 and Applications of Indoles Volume Editor: G.W. Gribble Heterocyclic Polymethine Dyes Volume 26, 2010 Synthesis, Properties and Applications Volume Editor: L. Strekowski Synthesis of Heterocycles via Volume 14, 2008 Multicomponent Reactions II Synthesis of Heterocycles via Volume Editors: R.V.A. Orru, E. Ruijter Cycloadditions II Volume 25, 2010 Volume Editor: A. Hassner Volume 13, 2008 Anion Recognition in Supramolecular Chemistry Synthesis of Heterocycles via Volume Editors: P.A. Gale, W. Dehaen Cycloadditions I Volume 24, 2010 Volume Editor: A. Hassner Volume 12, 2008 Synthesis of Heterocycles via Multicomponent Reactions I Bioactive Heterocycles V Volume Editors: R.V.A. Orru, E. Ruijter Volume Editor: M.T.H. Khan Volume 23, 2010 Volume 11, 2007 Bioactive Heterocycles IV Heterocyclic Scaffolds I: b-Lactams Volume Editor: M.T.H. Khan Volume Editor: B. Banik Volume 10, 2007 Volume 22, 2010 Bioactive Heterocycles III Phosphorous Heterocycles II Volume Editor: M.T.H. Khan Volume Editor: R.K. Bansal Volume 9, 2007 Volume 21, 2009 Bioactive Heterocycles II Phosphorous Heterocycles I Volume Editor: S.
    [Show full text]
  • GEORGES DARZENS (1867-1954): INVENTOR and ICONOCLAST
    ll. Hist. Ch. 6 (4 I GEORGES DARZENS (1867-1954): INVENTOR and ICONOCLAST rr zl, Él plthn Georges Darzen's name is absent from the Dictionary less a student completed the École polytechnique cur- of Scientific Biography. This is a regrettable omission, riculum with a very high ranking (the first 15 or 20 on three grounds. He was a creative organic chemist, to would enter government service as high-level technical whom we owe both the thionyl chloride conversion of councilors), he would be inducted into the French alcohols into chlorides and the "Darzens reaction"—an Army. Most Polytechniciens became Army captains and addition-fragmentation which can be seen as the forerun- served out life-long careers within the military. Not so ner to the Wittig reaction. He was a perceptive observer with Darzens—even though his final rank was 39th out of the scientific scene, keen on informing his students of a class of 226, his poor eyesight spared him from an of the latest scientific developments during the first Army commission. quarter of this century regarding the structure of the Turned away from astronomy, Darzens embraced atom and the quantum theory of spectra. And this genu- chemistry. His mentor at the École polytechnique, ine Renaissance man, by his multi-faceted talents, by the Édouard Grimaux (1835-1900), was at the time of diverse degrees he took, by his prolific academic and in- Darzens's studies (1886-1888) one of the few French dustrial activities, was also endowed with a remarkable organic chemists to disobey the decree of Marcelin independence of spirit.
    [Show full text]