DOCSLIB.ORG

Chemical Reviews

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chemical Reviews Chemical Reviews Volume 84, Number 5 October 1984 Three-Carbon Homologating Agents JOHN C. STOWELL aaperhrsnf of chemlsbj'. ulhraslly 01 Flsw (Maam, Lake Fmt, New mns,LOUL&M 70148 Rscslvad NoVembsr 7, 1983 (Uevk4 MamcrW Receivad Juw, 27. 19W contents I. Introduction 409 11. Nucleophilic Reagents 410 A. Reagents Providing Functknal Chains wlth 410 Saturated a-. 8-. and y-Carbons 1. Ethers and Alcohols 410 2. Amines 41 1 3. Bromldes 41 1 4. Propionaldehyde Homoenolate 413 Equivalents 5. Propionate Homenolate Equivalents 419 E. Reagents Rovidlng the Terminal Acetylene 421 Function C. Reagents Rovldlng a.@-Unsatuated 422 Functionality 1. Allylic Alcohols and Halides 422 2. a,@-UnsaturatedAldehydes 422 3. a,@-UnsaturatedCarboxylic Aclds. 424 John C. Stowel was bom in Passaic. NJ. in 1938. and received Esters, and Lactones hls B.S. degee h chemlsby from Rutgers UnivmW in 1960. Hls D. Reagents Providing a.@-Acetylenk 425 W.D. wee in Qganlc chemistry was granted by Massachusetts Functionality Insmule of Tedrmqly h 1964 where he waked WMDr. Frm 1. a.@-Acatylenk Alcohols 425 D. Greene on freeradical termination reactions and prepared the first diaziridinone. He pined the Central Research division of 3M 2. a,@-AcetylenicAldehydes 426 Company in St. Paul. MN. for 4 years. In 1969 he became a 3. a,@-Acetylenic Carboxylic Aclds and 426 postdoctoral fellow at The Ohio State University with Dr. Leo A. Esters Paquette. He prepared and sWIW various (CH),, and benzo (CH),, E. Reagents providing B.yUnsahmted 426 cwnpounds including Umrmal and sihw-catalyred rearrangements. Functionality In 1970 he jokd the faculty of me University of New Ohms. thm known as Lcuiskna State University in New Orleans. His research 1. @.y-Unsaturated Alcohds 426 mere included threecarbon homologating agents. three- and 2. @,y-Unsaturated Halidas 427 four-membered ring heterocycles, formimidoyi halides. sterically 3. @,y-Unsaturated Aldehydes 427 hindered amines and nitroso compounds, and heterogeneous 4. @,y-Unsaturated Acids and DerivaWes 428 concurrent strong acid and base catalysis. 111. Electrophlllc Reagents 429 A. Chlor- and Bromopropylatbn 429 subject is not indexed as such, therefore a thorough B. Hydroxypropylatlon 429 search is not posaible and I expect there are other useful C. &Electrophilic Equivalents of 430 reagents unintentionally omitted here. Nevertheless Ropionaidehyde this review will make the surprisingly large number of D. @-Electrophilic Equivalents of Rophk 430 alternative reagents more readily accessible to the Acid, Propionic Ester. or Propionitrile synthetic organic chemist. The reagents selected here carry only three carbons I. Introduction but there are many other closely related reagents car- rying methyl groups or other structures that operate hy There are over 100 reagents useful for the extension the same principles found here. Thus the reader may of organic molecules hy three carbons with some func- use this review in planning incorporation of branched tionality at the new terminus. The literature on this extensions. 0009-2665/84/0784-0409$06.50/0 0 1984 American Chemical Societv 410 Chemical Reviews, 1984, Vol. 84, NO. 5 Stowell The subject consists of two fundamental classes, the propanol was converted to the Grignard reagent in THF nucleophilic and the electrophilic reagents. Within while cooling to 30-40 "C. This was added to cyclo- these two categories the organization is based on the dodecanone and cleaved with hydrogen to give 3-(1- degree of unsaturation in the chain and the level of hydroxycyclododecyl)-2-methylpropanolin 65 % yield.6 oxidation in the functional group. One should therefore The phenylthio group, in contrast to the oxygen keep in mind that a reagent in any part of the review ethers, does not undergo a 1,3-elimination. Thus, 3- might be useful for a certain synthesis if it is followed bromopropyl phenyl sullide and magnesium in THF or with an oxidation or reduction reaction. ether gives the Grignard reagent which could be acy- lated with a mixed anhydride at low temperature or I I. Nucleophlllc Reagents added to an aldehyde or ketone to give alcohols. The phenylthio group may then be removed by a-halogen- The choice of functionality that may be placed on the ation and hydrolysis with CuO and CuClz to give a third carbon of a nucleophilic reagent is limited owing y-keto or y-hydroxy aldeh~de.~-~ to the facile intramolecular attack leading to cyclo- The analogous lithium reagents containing benzyl or propanes. Groups that would ordinarily be stable to- phenylthio ether groups can be prepared using lithium ward intermolecular attack by Grignard or lithium dispersion or lithium naphthalene.'O 3-Chloropropyl reagents may not withstand the intramolecular attack phenyl sulfide gives [3-(thiophenoxy)propyl]lithium, under similar conditions. For example, simple alkyl and 3-(benzyloxy)propyl phenyl sulfide gives [3-(ben- ethers are stable while phenyl ethers are not. However, zyloxy)propyl]lithium (eq 1). many useful reagents have been devised where the electrophilic character of the @-functionalityis reduced or where the nucleophilic site is rendered less potent by delocalization either allylically in the chain or out- PhCH20MLi PhCH20 ward to other temporary substituents. In other cases 0 the three carbons are delivered with a double or triple bond in the chain that geometrically prevents three- 70% membered ring formation. These may be reduced to Acetal protection of an alcohol function may be re- the saturated chain at a later stage. moved easily with mild acid. Eatonl1J2used ethyl vinyl ether to protect 3-bromo- and 3-chloropropanol. Both A. Reagents Providing Functional Chains with of these halo acetals react rapidly with lithium metal Saturated cy-, @-, and ?-Carbons in ether, starting at room temperature and then cooling to between -15 and -5 "C for most of the reaction. The 1. Ethers and Alcohols organolithium reagent is stable at -30 OC for months In 1904 Hamonetl showed that a Grignard reagent but at room temperature it slowly decomposes to cy- could be prepared from 3-iodopropyl n-pentyl ether and clopropane and other products. The lithium reagent that it would couple with bromomethyl n-pentyl ether adds readily to ketones,11-14 and the acetal may be hy- to give a diether. 1,6Dimethoxybutane could be pre- drolyzed rapidly at room temperature with dilute pared similarly. Yields and other details were not given. aqueous ethanolic hydrochloric acid to afford 1,Cdiols Where a hydroxyl group is the desired functionality, in high yield (eq 2). This hydrolysis is mild enough to various protecting groups have been used during the nucleophilic step. Some ethers were suitable while Li - others were not. 3-Bromopropyl phenyl ether as well sthbr. -10 *C as the iodo compound gave prompt 1,3-elimination to afford cyclopropane plus the phenoxide salt when treated with magnesium in ethe~~8A Grignard reagent could be prepared from the methyl ether, however, and it was added to a nitrile to afford a keto ether in low 96% yield. In this case the ether was cleaved with hot con- leave the tertiary alcohol function undisturbed. This centrated hydrobromic acid at a later stage and ulti- reagent also reacts with y-lactones to give spiroketals mately used to prepare a pyrrolidine ring. Even the (eq 3).15 alkyl ethers show instability at higher temperatures. For example, the Grignard reagent from 3-bromopropyl ethyl ether gives cyclopropane when heated to about 75 "C in ben~ene.~ A tertiary ether is more readily removed. Thus tert-amyl 3-bromopropyl ether gave the Grignard reagent in ether in about 80% yield. This could be carbonated to give 4-(tert-amyloxy)butyric acid (53% 63% yield) or added to benzaldehyde, acetone, or cyclo- The corresponding Grignard reagent would not form hexanone in 90% yield^.^ Heating the hydroxy ether in ether'l but it could be prepared from magnesium products with p-toluenesulfonic acid cleaves the ether turnings in THF at 0-10 "C in about 65% yield.16 but also causes cyclization to the corresponding tetra- Catalytic or larger amounts of copper salts were used hydrofurans in 70-90% yields. with the lithium or magnesium reagent to give coupling A benzyl ether can be removed by mild hydrogenol- and Michael reactions. For instance cuprous iodide and ysis but again the Grignard reagent shows some insta- the lithium reagent gave conjugate addition to cyclo- bility. The benzyl ether of 3-bromo-2-methyl-l- pentenone (50%). It is not effective with highly @- Three-Carbon Homologating Agents Chemical Reviews, 1984, Vol. 84, No. 5 411 substituted substrates but a mixed magnesium cuprate A remarkably simple alternative is now available with will serve as shown in eq 4.17 The mixed cuprate from the discovery that the Grignard reagent can be prepared directly from the chloroalkoxide. Methyl or isopropyl 0 magnesium chloride gives the alkoxide from 3-chloro- 1-propanol at -20 "C in THF. This salt is soluble enough to give 0.3 N solutions at room temperature. It will react with magnesium in refluxing THF with the aid of a small amount of 1,Zdibromoethane to give the Grignard reagent 8). reagent gives all the usual I (4) (eq This Ob reactions" including addition to ketones, coupling with allylic halides,25copper-catalyzed conjugate addition26 and alkylation in 75-90% yields. 60% (1) CH3MpCI copper tert-butylacetylide was used in a conjugate ad- CIMOH Mg9 THF - CIMgMOMgCI (8) dition to an a,@-unsaturated lactone (56%).18 The a 5 - 90% polymeric complex prepared from lithium reagent and 2. Amines an equivalent amount
Load more

Recommended publications
  • 14.8 Organic Synthesis Using Alkynes
    14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 666 666 CHAPTER 14 • THE CHEMISTRY OF ALKYNES The reaction of acetylenic anions with alkyl halides or sulfonates is important because it is another method of carbon–carbon bond formation. Let’s review the methods covered so far: 1. cyclopropane formation by the addition of carbenes to alkenes (Sec. 9.8) 2. reaction of Grignard reagents with ethylene oxide and lithium organocuprate reagents with epoxides (Sec. 11.4C) 3. reaction of acetylenic anions with alkyl halides or sulfonates (this section) PROBLEMS 14.18 Give the structures of the products in each of the following reactions. (a) ' _ CH3CC Na| CH3CH2 I 3 + L (b) ' _ butyl tosylate Ph C C Na| + L 3 H3O| (c) CH3C' C MgBr ethylene oxide (d) L '+ Br(CH2)5Br HC C_ Na|(excess) + 3 14.19 Explain why graduate student Choke Fumely, in attempting to synthesize 4,4-dimethyl-2- pentyne using the reaction of H3C C'C_ Na| with tert-butyl bromide, obtained none of the desired product. L 3 14.20 Propose a synthesis of 4,4-dimethyl-2-pentyne (the compound in Problem 14.19) from an alkyl halide and an alkyne. 14.21 Outline two different preparations of 2-pentyne that involve an alkyne and an alkyl halide. 14.22 Propose another pair of reactants that could be used to prepare 2-heptyne (the product in Eq. 14.28). 14.8 ORGANIC SYNTHESIS USING ALKYNES Let’s tie together what we’ve learned about alkyne reactions and organic synthesis. The solu- tion to Study Problem 14.2 requires all of the fundamental operations of organic synthesis: the formation of carbon–carbon bonds, the transformation of functional groups, and the establish- ment of stereochemistry (Sec.
    [Show full text]
  • “Alkenyl Nonaflates from Carbonyl Compounds: New Synthesis, Elimination Reactions, and Systematic Study of Heck and Sonogashira Cross-Couplings”
    “Alkenyl nonaflates from carbonyl compounds: New synthesis, elimination reactions, and systematic study of Heck and Sonogashira cross-couplings” A thesis submitted to the Freie Universität Berlin for the degree of Dr. rer. nat. Faculty of Chemistry and Biochemistry 2009 Michael Alexander Kolja Vogel Department of Biology, Chemistry and Pharmacy FU Berlin 1. Gutachter: Prof. Dr. C. B. W. Stark 2. Gutachter: Prof. Dr. H.-U. Reißig Promotionsdatum: 19.06.2009 Contents Contents Contents 3 Abbreviations 7 Declaration and Copyright Statement 9 The Author 12 Acknowledgements 13 Abstract / Zusammenfassung 14 Introduction and Objective 16 Chapter 1 Alkenyl nonaflates from enolizable carbonyl precursors – 25 methodology, preparation, and elimination reactions 1.1. Purification of NfF and compatibility experiments with bases 26 1.2. Application of the internal quenching protocol for the 30 preparation of cyclic alkenyl nonaflates 1.3. Reactions of acyclic ketones with NfF and phosphazene bases 36 1.3.1 General remarks 36 1.3.2. Synthesis of alkynes: reactivity and selectivity 38 1.4. The formation of allenes 45 1.5. Conversion of aldehydes with NfF and phosphazene bases 50 1.5.1. Alkenyl nonaflate formation 50 1.5.2. Formation of terminal alkynes 52 1.6. Conclusions 54 Chapter 2 The alkenyl nonaflates in the Heck reaction – 56 methodology and reactivity 3 Contents 2.1. General remarks 57 2.2. Methodology and initial experiments 59 2.3. Systematic investigations 61 2.3.1. The solvent effect 61 2.3.2. The effect of different bases 65 2.3.3. The effect of additives 66 2.3.4. The effect of triphenylphosphine 71 2.3.5.
    [Show full text]
  • United States Patent Office Patiented Jan.5, 1963 2 Evaporation of the Solvent, to Leave Behind a Thin, De 3,073,794 Posited Film of the Polymer
    3,073,794 United States Patent Office Patiented Jan.5, 1963 2 evaporation of the solvent, to leave behind a thin, de 3,073,794 posited film of the polymer. Basically, a suitable poly SPRAYABLE, ANHYDROUS SOLUTION OF -V. mer is a “1-vinyl-2-pyrrolidone polymer" and this is the NYL-2-PYRERODONE POLYMER IN CHELOR principal component. However, the term is also defined FLUORO HYDRO CARBON PROPELLANT George G. Stoner, Easton, Pa., assignor to General herewith to include not only the homopolymers but also a Aniline & Film Corporation, New York, N.Y., a corpor wide range of heteropolymers, copolymers, interpolymers, ration of Delaware terpolymers (three-component polymers) and, in general, No Drawing. Fied May 22, 1959, Ser. No. 814,999 polymers in which vinylpyrrollidone is either the sole com 6 (Cais. (CE. 260-33.8) ponent, a major component or a substantial component. O In the latter two instances the vinylpyrrollidone is copolym This invention relates to film-forming compositions, erized with such substances as vinyl acetate, isopropenyl and relates more particularly to sprayable film-forming acetate, vinyl laurate, vinyl stearate, vinyl oleate, vinyl compositions which are non-flammable and non-alcoholic benzoate, and other vinyl and isopropenyl esters; vinyl and which are eminently suitable for therapeutic pur chloride, 2-chloropropene, and other vinyl and isopropenyl poses. 5 halides; methyl vinyl ether, ethyl vinyl ether, isopropyl This application is a continuation-in-part of my ap vinyl ether, isobutyl vinyl ether, 2-ethoxyethyl vinyl ether, plication Serial No. 580,443, filed April 25, 1956 and now phenyl vinyl ether and other vinyl ethers; acrylic acid and abandoned.
    [Show full text]
  • Chapter 8 - Alkynes: an Introduction to Organic Synthesis
    Chapter 8 - Alkynes: An Introduction to Organic Synthesis Draw structures corresponding to each of the following names. 1. ethynylcyclopropane Answer: CCH 2. 3,10-dimethyl-6-sec-butylcyclodecyne Answer: 3. 4-bromo-3,3-dimethyl-1-hexen-5-yne CH3 Br Answer: H 2C CH C CH C C H CH3 4. acetylene Answer: H CCH Provide names for each compound below. CH3 5. CH3C CCHCH2CH2CH3 Answer: 4-methyl-2-heptyne CH 3 6. CCH Answer: 1-ethynyl-2-methylcyclopentane Test Items for McMurry’s Organic Chemistry, Seventh Edition 59 The compound below has been isolated from the safflower plant. Consider its structure to answer the following questions. H H CCCCCCCC H H3C C C C H H C H H 7. What is the molecular formula for this natural product? Answer: C13H10 8. What is the degree of unsaturation for this compound? Answer: We can arrive at the degree of unsaturation for a structure in two ways. Since we know that the degree of unsaturation is the number of rings and/or multiple bonds in a compound, we can simply count them. There are three double bonds (3 degrees) and three triple bonds (six degrees), so the degree of unsaturation is 9. We can verify this by using the molecular formula, C13H10, to calculate a degree of unsaturation. The saturated 13-carbon compound should have the base formula C13H28, so (28 - 10) ÷ 2 = 18 ÷ 2 = 9. 9. Assign E or Z configuration to each of the double bonds in the compound. Answer: H H E CCCCCCCCE H H3C C C C H H C H H 10.
    [Show full text]
  • The Chemistry of Alkynes
    14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 644 14 14 The Chemistry of Alkynes An alkyne is a hydrocarbon containing a carbon–carbon triple bond; the simplest member of this family is acetylene, H C'C H. The chemistry of the carbon–carbon triple bond is similar in many respects toL that ofL the carbon–carbon double bond; indeed, alkynes and alkenes undergo many of the same addition reactions. Alkynes also have some unique chem- istry, most of it associated with the bond between hydrogen and the triply bonded carbon, the 'C H bond. L 14.1 NOMENCLATURE OF ALKYNES In common nomenclature, simple alkynes are named as derivatives of the parent compound acetylene: H3CCC' H L L methylacetylene H3CCC' CH3 dimethylacetyleneL L CH3CH2 CC' CH3 ethylmethylacetyleneL L Certain compounds are named as derivatives of the propargyl group, HC'C CH2 , in the common system. The propargyl group is the triple-bond analog of the allyl group.L L HC' C CH2 Cl H2CA CH CH2 Cl L L LL propargyl chloride allyl chloride 644 14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 645 14.1 NOMENCLATURE OF ALKYNES 645 We might expect the substitutive nomenclature of alkynes to be much like that of alkenes, and it is. The suffix ane in the name of the corresponding alkane is replaced by the suffix yne, and the triple bond is given the lowest possible number. H3CCC' H CH3CH2CH2CH2 CC' CH3 H3C CH2 C ' CH L L L L L L L propyne 2-heptyne 1-butyne H3C CH C ' C CH3 HC' C CH2 CH2 C' C CH3 L L L L 1,5-heptadiyneLL L "CH3 4-methyl-2-pentyne Substituent groups that contain a triple bond (called alkynyl groups) are named by replac- ing the final e in the name of the corresponding alkyne with the suffix yl.
    [Show full text]
  • The Molecular Level Modification of Surfaces: from Self-Assembled Monolayers to Complex Molecular Assemblies
    University of Wollongong Research Online Australian Institute for Innovative Materials - Papers Australian Institute for Innovative Materials 1-1-2011 The molecular level modification of surfaces: From self-assembled monolayers to complex molecular assemblies J Justin Gooding University of New South Wales, [email protected] Simone Ciampi University of New South Wales, [email protected] Follow this and additional works at: https://ro.uow.edu.au/aiimpapers Part of the Engineering Commons, and the Physical Sciences and Mathematics Commons Recommended Citation Gooding, J Justin and Ciampi, Simone, "The molecular level modification of surfaces: From self- assembled monolayers to complex molecular assemblies" (2011). Australian Institute for Innovative Materials - Papers. 1853. https://ro.uow.edu.au/aiimpapers/1853 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] The molecular level modification of surfaces: From self-assembled monolayers to complex molecular assemblies Abstract The modification of surfaces with self-assembled monolayers (SAMs) containing multiple different molecules, or containing molecules with multiple different functional components, or both, has become increasingly popular over the last two decades. This explosion of interest is primarily related to the ability to control the modification of interfaces with something approaching molecular level control and to the ability to characterise the molecular constructs by which the surface is modified. Over this time the level of sophistication of molecular constructs, and the level of knowledge related to how to fabricate molecular constructs on surfaces have advanced enormously. This critical review aims to guide researchers interested in modifying surfaces with a high degree of control to the use of organic layers.
    [Show full text]
  • Arxiv:1406.7034V1 [Astro-Ph.SR] 26 Jun 2014 Abn PH)Aecmol Noe Stercarrier
    Draft version July 13, 2018 A Preprint typeset using LTEX style emulateapj v. 5/2/11 CARBON-RICH DUST PAST THE ASYMPTOTIC GIANT BRANCH: ALIPHATICS, AROMATICS, AND FULLERENES IN THE MAGELLANIC CLOUDS G. C. Sloan1, E. Lagadec1, A. A. Zijlstra2, K. E. Kraemer3, A. P. Weis4,5, M. Matsuura6, K. Volk7, E. Peeters8,9, W. W. Duley10, J. Cami8,9, J. Bernard-Salas11, F. Kemper12, & R. Sahai13 Draft version July 13, 2018 ABSTRACT Infrared spectra of carbon-rich objects which have evolved off the asymptotic giant branch reveal a range of dust properties, including fullerenes, polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons, and several unidentified features, including the 21 µm emission feature. To test for the presence of fullerenes, we used the position and width of the feature at 18.7–18.9 µm and examined other features at 17.4 and 6–9 µm. This method adds three new fullerene sources to the known sample, but it also calls into question three previous identifications. We confirm that the strong 11 µm features seen in some sources arise primarily from SiC, which may exist as a coating around carbonaceous cores and result from photo-processing. Spectra showing the 21 µm feature usually show the newly defined Class D PAH profile at 7–9 µm. These spectra exhibit unusual PAH profiles at 11–14 µm, with weak contributions at 12.7 µm, which we define as Class D1, or show features shifted to ∼11.4, 12.4, and 13.2 µm, which we define as Class D2. Alkyne hydrocarbons match the 15.8 µm feature associated with 21 µm emission.
    [Show full text]
  • Guidance Document Peroxide-Forming Chemicals
    Guidance Document Peroxide-Forming Chemicals Some chemicals can form peroxides under normal storage conditions. Some of the peroxide chemicals are unstable, especially when dried or concentrated, and can explode violently when subjected to heat, light or mechanical shock. In addition, some of the inadvertently formed peroxides can initiate other unexpected violent reactions (e.g. polymerizations) with other chemicals. When possible and practical for your work, purchase chemicals that have inhibitors added by the manufacturer. Label peroxide-forming chemicals with date received and date opened. Store peroxide-formers in airtight opaque containers with screw caps. Consider oxygen exclusion methods such as purging with inert gas or sealing containers with parafilm. Inspect containers for signs of peroxide formation. Do not open a container which has crystals or a visible cloudiness. Call EHS to come remove it. The friction caused by opening a lid can cause an explosion. Liquids can be tested for presence of peroxide. This is especially important prior to distilation. Most explosions of peroxide forming chemicals occur when a material is distilled to dryness. Peroxide test kits are available from chemical vendors. Contact EHS for additional guidance. Classification Table for Peroxide-Forming Chemicals Class I:: Unsaturated materials, especially those of low molecular weight, may polymerize violently and hazardously due to peroxide initiation. These chemicals can spontaneously decompose, becoming explosive after exposure to air with concentration. Discard unopened containers within 3 months. Opened containers should be tested for peroxides every 2 months. Acrylic acid Tetrafluoroethylene Acrylonitrile Vinyl acetate 1,3-Butadiene Vinyl acetylene Chlorobutadiene (chloroprene) Vinyl chloride Chlorotrifluoroethylene Vinyl pyridine Methyl methacrylate Vinylidiene chloride Styrene Class II: The following chemicals are a peroxide hazard upon concentration (distillation/evaporation).
    [Show full text]
  • Reactions of Alkenes and Alkynes
    05 Reactions of Alkenes and Alkynes Polyethylene is the most widely used plastic, making up items such as packing foam, plastic bottles, and plastic utensils (top: © Jon Larson/iStockphoto; middle: GNL Media/Digital Vision/Getty Images, Inc.; bottom: © Lakhesis/iStockphoto). Inset: A model of ethylene. KEY QUESTIONS 5.1 What Are the Characteristic Reactions of Alkenes? 5.8 How Can Alkynes Be Reduced to Alkenes and 5.2 What Is a Reaction Mechanism? Alkanes? 5.3 What Are the Mechanisms of Electrophilic Additions HOW TO to Alkenes? 5.1 How to Draw Mechanisms 5.4 What Are Carbocation Rearrangements? 5.5 What Is Hydroboration–Oxidation of an Alkene? CHEMICAL CONNECTIONS 5.6 How Can an Alkene Be Reduced to an Alkane? 5A Catalytic Cracking and the Importance of Alkenes 5.7 How Can an Acetylide Anion Be Used to Create a New Carbon–Carbon Bond? IN THIS CHAPTER, we begin our systematic study of organic reactions and their mecha- nisms. Reaction mechanisms are step-by-step descriptions of how reactions proceed and are one of the most important unifying concepts in organic chemistry. We use the reactions of alkenes as the vehicle to introduce this concept. 129 130 CHAPTER 5 Reactions of Alkenes and Alkynes 5.1 What Are the Characteristic Reactions of Alkenes? The most characteristic reaction of alkenes is addition to the carbon–carbon double bond in such a way that the pi bond is broken and, in its place, sigma bonds are formed to two new atoms or groups of atoms. Several examples of reactions at the carbon–carbon double bond are shown in Table 5.1, along with the descriptive name(s) associated with each.
    [Show full text]
  • PALLADIUM CATALYSED OLIGOMERIZATION of 1-ALKYNES by Ann Beal Hunt
    RICE UNIVERSITY PALLADIUM CATALYSED OLIGOMERIZATION OP 1-ALKYNES by Ann Beal Hunt A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS Thesis Director’s Signature: Houston, Texas August 197^ ABSTRACT PALLADIUM CATALYSED OLIGOMERIZATION OF 1-ALKYNES by Ann Beal Hunt The oligomerization of 1-pentyne using palladium acetyl acetonate catalyst with various solvents and ligands was in¬ vestigated. An equimolar mixture of HOAc and Et N proved 3 to be a superior solvent. The major product observed in most cases was the dimer, 6-methylene-nona-^-yne, although both cis and trans-dec-^t-ene-6-yne were observed in most cases. Trimers were formed when phosphines were replaced with bldentate amines or phosphite ligands. A one to one mixture of PPh and (CH 0) P gave the highest yield of 3 3 3 oligomers with 6-methylene-nona-4-yne as the major product. No aromatics were formed with any of the reaction systems studied. 19 The general mechanism proposed, by Meriwether and 15 elaborated by Maitlis is in agreement with these results. ACKNOWLEDGEMENTS I wish to thank Rice University and the Robert A. Welch Foundation for their financial support. to Jerry and my parents TABLE OF CONTENTS Introduction 1 Results and Discussion 15 Experimental 3H Bibliography Ml Appendix: spectra M3 1 INTRODUCTION There has been considerable interest in the metal catalyzed oligomerization of acetylenes since Reppe's initial discovery in 19^8 that nickel catalysed the tetra- 21 merization of acetylene to cyclooctatetraene. 20 Odaira in 1966 observed the formation of conjugated trans-polyacetylene upon addition of PdCl to acetylene in 2 acetic acid.
    [Show full text]
  • Gfsorganics & Fragrances
    Chemicals for Flavors GFSOrganics & Fragrances GFS offers a broad range of specialty organic chemicals Specialized chemistries we as building blocks and intermediates for the manufacture of offer include: flavors and fragrances. • Alkynes Over 5,500 materials, including 1,400 chemicals from natural sources, are used for flavor • Alkynols enhancements and aroma profiles. These aroma chemicals are integral components of • Olefins the continued growth within consumer products and packaged foods. The diversity of products can be attributed to the broad spectrum of organic compounds derived from • Unsaturated Acids esters, aldehydes, lactones, alcohols and several other functional groups. • Unsaturated Esters • DIPPN and other Products GFS Chemicals manufactures a wide range of organic intermediates that have been utilized in a multitude of personal care applications. For example, we support Why GFS? several market leading companies in the manufacture and supply of alkyne based aroma chemicals. • Specialized Chemistries • Tailored Specifications As such, we understand the demanding nature of this fast changing market and are fully • From Grams to Metric Tons equipped to overcome process challenges and manufacture the novel chemical products • Responsive Technical Staff that you need, when you need them. We offer flexible custom manufacturing services to produce high purity products with the assurance of quality and full confidentiality. • Uncompromised Product Quality Our state-of-the-art manufacturing facility, located in Columbus, OH is ISO 9001:2008 certified. As a U.S. based manufacturer we have a proven record of helping you take products from development to commercialization. Our technical sales experts are readily accessible to discuss your project needs and unique product specifications.
    [Show full text]
  • “Inert” Ingredients Used in Organic Production
    “Inert” Ingredients Used in Organic Production Terry Shistar, PhD A Beyond Pesticides Report he relatively few registered pesticides allowed in organic production are contained in product formulations with so-called “inert” ingredients that are not disclosed on the T product label. The “inerts” make up the powder, liquid, granule, or spreader/sticking agents in pesticide formulations. The “inerts” are typically included in products with natural or synthetic active pesticide ingredients recommended by the National Organic Standards Board (NOSB) and listed by the National Organic Program (NOP) on the National List of Allowed and Prohibited Substances. Any of the pesticides that meet the standards of public health and environmental protection and organic compatibility in the Organic Foods Production Act (OFPA) may contain “inert” ingredients. Because the standards of OFPA are different from those used by the U.S. Environmental Protection Agency (EPA) to regulate pesticides and given changes in how the agency categorizes inerts, the NOSB has adopted a series of recommendations since 2010 that established a substance review process as part of the sunset review. NOP has not followed through on the Board’s recommendations and, as a result, there are numerous materials in use that have not been subject to OFPA criteria. This report (i) traces the history of the legal requirements for review by the NOSB, (ii) identifies the universe of toxic and nontoxic materials that make of the category of “inerts” used in products permitted in organic production, and (iii) suggests a path forward to ensure NOSB compliance with OFPA and uphold the integrity of the USDA organic label.
    [Show full text]