Enols and Enolates a Type of Reaction with Carbonyl Compounds Is an Α
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Stereoselective Reactions of Enolates: Auxiliaries
1 Stereoselective reactions of enolates: auxiliaries • Chiral auxiliaries are frequently used to allow diastereoselective enolate reactions • Possibly the most extensively studied are the Evan’s oxazolidinones • These are readily prepared from amino acids O O (EtO)2C=O reduction K CO Ph OH 2 3 HN O Ph OH NH2 NH2 Ph (S)-phenylalanine oxazolidinone chiral auxiliary • Enolate formation gives the cis-enolate (remember enolisation of amides) • Two possible conformations exist - but chelation results in one being preferred Li O O O O Me Me N O LDA N O O Me Me Me 1. n-BuLi Me HN O 2. EtCOCl Me Me Me O O Me Li valine LDA derivative O N O O N O Me Me Me Me 123.702 Organic Chemistry 2 Diastereoselective alkylation of Evan’s enolate Li O O O O Me Me N O PhCH2I N O Ph Me Me Me Me I Ph Li O Bn O O O O O H H Me N Me N H Me Me Me Me iso-propyl group blocks bottom face • Clearly (I hope) one face of the enolate is blocked • Chelation results in a rigid structure that provides maximum steric hindrance • The electrophile can only approach from one face 123.702 Organic Chemistry 3 Diastereoselective alkylation of Evan’s enolate Li O O O O Me Me N O PhCH2I N O Ph Me Me Me Me I Ph Li O Bn O O O O O H H Me N Me N H Me Me Me Me iso-propyl group blocks bottom face • Clearly (I hope) one face of the enolate is blocked • Chelation results in a rigid structure that provides maximum steric hindrance • The electrophile can only approach from one face 123.702 Organic Chemistry 4 Diastereoselective functionalisation Li O O O O Br LDA Me Me N O N O H Ph Ph 96% de H O -
Ochem ACS Review 18 Enols and Enolates
ACS Review Enols and Enolates 1. Which of the following have an enol form? I. benzaldehyde, C 6H5CHO II. 2,2-dimethylpropanal, (CH 3)3CCHO III. 2-chloropropanal, CH 3CHClCHO A. only I B. only II C. only III D. all of them have an enol form 2. Which one of the following has two different enol forms? A. cyclohexanone B. 2,2-dimethylcyclohexanone C. 3,3-dimethylcyclohexanone D. 4,4-dimethylcyclohexanone 3. How many alpha hydrogens are there on 2,4-dimethyl-3-pentanone? A. two B. three C. four D. six 4. Identify the most acid hydrogen for the following compound. A. 1 B. 2 C. 3 D. 4 5. What is the product of the reaction below? A. A B. B C. C D. D 6. Arrange the following compounds in order of decreasing acidity. A. I > II > III B. II > III > I C. III > II > I D. III > I > II 7. Identify the keto form of the following enol. A. 1-penten-3-one B. (E)-3-penten-2-one C. 2-pentanone D. (E)-3-pentenal 8. What is the relationship between keto and enol tautomers? A. resonance forms B. stereoisomers C. constitutional isomers D. different conformations of the same compound 9. Which of the following has the highest percentage of enol in a keto-enol equilibrium? A. hexanal B. 2-hexanone C. 2,4-hexanedione D. 2,5-hexanedione 10. Which one of the following optically active compounds racemizes in dilute KOH/CH 3OH solution? A. A B. B C. C D. D 11. -
Alkylation by Enamines for Synthesis of Some Heterocyclic Compounds ﻴﺩ
------J. Raf. Sci., Vol. 20, No.2, pp 92- 101, 2009 ------ Alkylation by Enamines for Synthesis of some Heterocyclic Compounds Jasim A. Abdullah Department of Chemistry College of Education Mosul University (Received 25/ 9/ 2008 ; Accepted 13 / 4 / 2009) ABSTRACT Compounds of 4-phenyl-3-butene-2-one (1) and 4-(4-chlorophenyl)-3-butene-2-one (2) were prepared by reaction of benzaldehyde or 4-chlorobenzaldehyde with acetone. Also 1,3-diphenyl-2-chloropropene-1-one (3) was synthesized from the reaction of benzaldehyde with 2-chloroacetophenone through Claisen-Shmidt condensation. The substituted ∆1(9)- octalone-2 (4,5) was prepared by reaction of the compounds (1and2) with cyclohexanone through Michael addition followed by aldol condensation. Compounds (4,5) were reacted with alkyl halide, as 2-chloroacetophenone or 1,3-diphenyl-2-chloropropene-1-one (3), via enamines formation which then hydrolyzed to give compounds (6-9). Compounds (6,7) were reacted with hydrazine , urea and thiourea to afford compounds (10-15) . The structures of all synthesized compounds were confirmed by available physical and spectral means . Keywords : Enamines , Heterocyclic compounds. ــــــــــــــــــــــــــــــــــــــــــــــــــ ﺍﻻﻟﻜﻠﺔ ﺒﻭﺍﺴﻁﺔ ﺍﻷﻴﻨﺎﻤﻴﻨﺎﺕ ﻟﺘﺸﻴﻴﺩ ﺒﻌﺽ ﺍﻟﻤﺭﻜﺒﺎﺕ ﺍﻟﺤﻠﻘﻴﺔ ﻏﻴﺭ ﺍﻟﻤﺘﺠﺎﻨﺴﺔ ﺍﻟﻤﻠﺨﺹ ﺘﻡ ﺘﺤﻀﻴﺭ ﺍﻟﻤﺭﻜﺒﺎﺕ 4-ﻓﻨﻴل-3-ﺒﻴﻭﺘﻴﻥ-2-ﺍﻭﻥ (1) ﻭ4-(4-ﻜﻠﻭﺭﻭﻓﻨﻴل)-3-ﺒﻴﻭﺘﻴﻥ-2-ﺍﻭﻥ (2) ﻤﻥ ﺘﻔﺎﻋل ﺍﻟﺒﻨﺯﺍﻟﺩﻴﻬﻴﺩ ﺃﻭ 4-ﻜﻠﻭﺭﻭﺍﻟﺒﻨﺯﺍﻟﺩﻴﻬﻴﺩ ﻤﻊ ﺍﻻﺴﻴﺘﻭﻥ . ﺤﻀﺭ ﺍﻟﻤﺭﻜﺏ 3,1-ﺜﻨﺎﺌﻲ ﻓﻨﻴل -2-ﻜﻠـﻭﺭﻭﺒﺭﻭﺒﻴﻥ -1-ﺍﻭﻥ (3) ﻤـﻥ ﺘﻔﺎﻋـل ﺍﻟﺒﻨﺯﺍﻟﺩﻴﻬﻴـﺩ ﻤـﻊ -2 9 1 ﻜﻠﻭﺭﻭﺍﺴﻴﺘﻭﻓﻴﻨﻭﻥ ﺒﻭﺴﺎﻁﺔ ﺘﻜﺎﺜﻑ (ﻜﻠﻴﺯﻥ-ﺸﻤﺩﺕ).ﺤﻀﺭﺕ ﻤﻌﻭﻀﺎﺕ ∆ ( ) –ﺍﻭﻜﺘﺎﻟﻭﻥ-2 ﻤﻥ ﺨﻼل ﺘﻔﺎﻋل ﺍﻟﻤﺭﻜﺒﻴﻥ (2,1) ﻤﻊ ﺍﻟﻬﻜﺴﺎﻨﻭﻥ ﺍﻟﺤﻠﻘﻲ ﺒﻭﺴﺎﻁﺔ ﺍﻀﺎﻓﺔ ﻤﺎﻴﻜل ﺍﻟﺘﻲ ﻴﺘﺒﻌﻬﺎ ﺘﻜﺎﺜﻑ ﺍﻻﻟﺩﻭل . -
Aldehydes and Ketones
12 Aldehydes and Ketones Ethanol from alcoholic beverages is first metabolized to acetaldehyde before being broken down further in the body. The reactivity of the carbonyl group of acetaldehyde allows it to bind to proteins in the body, the products of which lead to tissue damage and organ disease. Inset: A model of acetaldehyde. (Novastock/ Stock Connection/Glow Images) KEY QUESTIONS 12.1 What Are Aldehydes and Ketones? 12.8 What Is Keto–Enol Tautomerism? 12.2 How Are Aldehydes and Ketones Named? 12.9 How Are Aldehydes and Ketones Oxidized? 12.3 What Are the Physical Properties of Aldehydes 12.10 How Are Aldehydes and Ketones Reduced? and Ketones? 12.4 What Is the Most Common Reaction Theme of HOW TO Aldehydes and Ketones? 12.1 How to Predict the Product of a Grignard Reaction 12.5 What Are Grignard Reagents, and How Do They 12.2 How to Determine the Reactants Used to React with Aldehydes and Ketones? Synthesize a Hemiacetal or Acetal 12.6 What Are Hemiacetals and Acetals? 12.7 How Do Aldehydes and Ketones React with CHEMICAL CONNECTIONS Ammonia and Amines? 12A A Green Synthesis of Adipic Acid IN THIS AND several of the following chapters, we study the physical and chemical properties of compounds containing the carbonyl group, C O. Because this group is the functional group of aldehydes, ketones, and carboxylic acids and their derivatives, it is one of the most important functional groups in organic chemistry and in the chemistry of biological systems. The chemical properties of the carbonyl group are straightforward, and an understanding of its characteristic reaction themes leads very quickly to an understanding of a wide variety of organic reactions. -
Aldehydes and Ketones Are Simple Organic Compounds Containing a Carbonyl Group
Aldehydes and Ketones are simple organic compounds containing a carbonyl group. Carbonyl group contains carbon- oxygen double bond. These organic compounds are simple because the carbon atom presents in the carbonyl group lack reactive groups such as OH or Cl. By Dr. Sayed Hasan Mehdi Assistant Professor Department of Chemistry Shia P.G. College, Lucknow Dr. S.Hasan Mehdi 6/13/2020 This is to bring to kind notice that the matter of this e- content is for the B.Sc. IV semester students. It has been taken from the following sources. The students are advised to follow these books as well. •A TEXTBOOK OF ORGANIC CHEMISTRY by Arun Bahl & B.S. Bahl, S. Chand & Company Ltd. Publication. •Graduate Organic Chemistry by M. K. Jain and S.C. Sharma, Vishal Publishing Co. •Pradeep’s Organic Chemistry Vol II by R. N. Dhawan, Pradeep Publication, Jalandhar. Dr. S.Hasan Mehdi 6/13/2020 An aldehyde is one of the classes of carbonyl group- containing alkyl group on one end and hydrogen on the other end. The R and Ar denote alkyl or aryl member respectively. In the condensed form, the aldehyde is written as –CHO. Dr. S.Hasan Mehdi 6/13/2020 Dr. S.Hasan Mehdi 6/13/2020 1. From Alcohols: a. By oxidation of Alcohols: Aldehydes and ketones can be prepared by the controlled oxidation of primary and secondary alcohols using an acidified solution of potassium dichromate or permanganate. Primary alcohol produces aldehydesRef. Last slide. O K Cr O RCH2OH + [O] 2 2 7 + R C H H 10 Alcohol Aldehyde O CH3CH2OH+ [O] K2Cr2O7 + CH3 C H H Ethyl Alcohol Acetaldehyde The aldehydes formed in the above reaction are very easily oxidised to carboxylc acids if allowed to remain in the reaction mixture. -
Esters Introduction Structurally, an Ester Is a Compound That Has an Alkoxy (OR) Group Attached to the Carbonyl Group
Esters Introduction Structurally, an ester is a compound that has an alkoxy (OR) group attached to the carbonyl group. O R C O R' R may be H, alkyl or aryl, while R’ may be alkyl or aryl only. Esters are widespread in nature. Many of the fragrances of flowers and fruits are due to the esters present. Ethyl butanoate is the chief component that accounts for the pineapple-like aroma and flavour of pineapples. 1:18 PM 1 Nomenclature of Esters Names of esters consist of two words that reflect the composite structure of the ester. The first word is derived from the alkyl group of the alcohol component, and the second word from the carboxylate group of the carboxylic acid component of the ester. The name of the carboxylate portion is derived by substituting the -ic acid suffix of the parent carboxylic acid with the –ate suffix. The alkyl group is cited first followed by the carboxylate group separated by a space. An ester is thus named as an alkyl 1:18 PM alkanoate. 2 IUPAC Nomenclature of Esters Examples 1:18 PM 3 Synthesis of Esters Preparative Strategies Highlighted below are some of the most common strategies by which esters are prepared. The esters are commonly prepared from the reaction of carboxylic acids, acid chlorides and acid anhydrides with alcohols. 1:18 PM 4 Synthesis of Esters Acid-Catalysed Esterification of a Carboxylic Acid and an Alcohol The acid-catalysed reaction of carboxylic acids and alcohols provides esters. Typically, a catalytic amount of a strong inorganic (mineral) acid such as H2SO4, HCl and H3PO4 is used. -
Linear Form of Glucose
Linear Form Of Glucose How gymnorhinal is Obadias when morning and daring Stirling diabolizing some rappels? Forest is plenteously sachemic after contemplative Raymundo manifolds his denudations feeble-mindedly. Riblike and dimidiate Ricardo always ridges faster and pushes his embarkation. Please contact us for more information. Glucose is further converted to starch for storage. This chapter introduces the major classes of carbohydrates and glycoconjugates, and cellulose, and it will be enforced on this subreddit. Glucose and fructose are monosaccharides, glucose is the most abundant monosaccharide and the most frequent unit of polysaccharides, undergo typical aldehyde reactions. Fructose is a ketohexose, Yan C, consult your doctor. Medical speaks to Dr. Add our main listener. First, potatoes, each of these is the basis for two ketohexoses. Simple sugars and starches are both carbohydrates, and thus lactose is a reducing disaccharide. The production of SCFA also results in the acidification of the colonic contents. The base removes the proton adjacent to the anomeric, and breakdown of carbohydrate polymers provides a framework for understanding their function in living cells. How to Convert a Trans Alkene into a Cis Alkene? Accessing this course requires a login. How is the structure of the monosaccharide changed from one form to the other in the human body? Sugars, LLC. Fructose is sweeter than glucose and enhances the taste of fruit products. Sheet Of Paper In A Cage. Understand what a reducing sugar and a reducing end are. Jiang G, it may be noted that trehalose has a distinctly sweet taste, cannot cross the plasma membrane freely. Please enable Cookies and reload the page. -
Catalytic Direct Asymmetric Michael Reactions
ORGANIC LETTERS 2001 Catalytic Direct Asymmetric Michael Vol. 3, No. 23 Reactions: Taming Naked Aldehyde 3737-3740 Donors Juan M. Betancort and Carlos F. Barbas III* The Skaggs Institute for Chemical Biology and the Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037 [email protected] Received September 5, 2001 ABSTRACT Direct catalytic enantio- and diastereoselective Michael addition reactions of unmodified aldehydes to nitro olefins using (S)-2-(morpholinomethyl)- pyrrolidine as a catalyst are described. The reactions proceed in good yield (up to 96%) in a highly syn-selective manner (up to 98:2) with enantioselectivities approaching 80%. The resulting γ-formyl nitro compounds are readily converted to chiral, nonracemic 3,4-disubstituted pyrrolidines. The Michael reaction is generally regarded as one of the Typically, carbon nucleophiles that contain an active most efficient carbon-carbon bond forming reactions, and methylene center such as malonic acid esters, â-keto esters, studies concerning this reaction have played an important nitroalkanes, etc. have been studied in the Michael reaction. role in the development of modern synthetic organic Carbonyl compounds, and ketones in particular, have gener- chemistry.1 As the demand for optically active compounds ally only been used as donors following their preactivation has soared in recent years, much progress has been made in by conversion into a more reactive species such as enol or the development of asymmetric variants of this reaction, enamine equivalents.5,6 In these cases, additional synthetic providing for the preparation of Michael adducts with high enantiomeric purity.2 Though remarkable advances have been (3) (a) Chataigner, I.; Gennari, C.; Ongeri, S.; Piarulli, U.; Ceccarelli, S. -
Fermentation and Ester Taints
Fermentation and Ester Taints Anita Oberholster Introduction: Aroma Compounds • Grape‐derived –provide varietal distinction • Yeast and fermentation‐derived – Esters – Higher alcohols – Carbonyls – Volatile acids – Volatile phenols – Sulfur compounds What is and Esters? • Volatile molecule • Characteristic fruity and floral aromas • Esters are formed when an alcohol and acid react with each other • Few esters formed in grapes • Esters in wine ‐ two origins: – Enzymatic esterification during fermentation – Chemical esterification during long‐term storage Ester Formation • Esters can by formed enzymatically by both the plant and microbes • Microbes – Yeast (Non‐Saccharomyces and Saccharomyces yeast) – Lactic acid bacteria – Acetic acid bacteria • But mainly produced by yeast (through lipid and acetyl‐CoA metabolism) Ester Formation Alcohol function Keto acid‐Coenzyme A Ester Ester Classes • Two main groups – Ethyl esters – Acetate esters • Ethyl esters = EtOH + acid • Acetate esters = acetate (derivative of acetic acid) + EtOH or complex alcohol from amino acid metabolism Ester Classes • Acetate esters – Ethyl acetate (solvent‐like aroma) – Isoamyl acetate (banana aroma) – Isobutyl acetate (fruit aroma) – Phenyl ethyl acetate (roses, honey) • Ethyl esters – Ethyl hexanoate (aniseed, apple‐like) – Ethyl octanoate (sour apple aroma) Acetate Ester Formation • 2 Main factors influence acetate ester formation – Concentration of two substrates acetyl‐CoA and fusel alcohol – Activity of enzyme responsible for formation and break down reactions • Enzyme activity influenced by fermentation variables – Yeast – Composition of fermentation medium – Fermentation conditions Acetate/Ethyl Ester Formation – Fermentation composition and conditions • Total sugar content and optimal N2 amount pos. influence • Amount of unsaturated fatty acids and O2 neg. influence • Ethyl ester formation – 1 Main factor • Conc. of precursors – Enzyme activity smaller role • Higher fermentation temp formation • C and N increase small effect Saerens et al. -
Chapter 14 – Aldehydes and Ketones
Chapter 14 – Aldehydes and Ketones 14.1 Structures and Physical Properties of Aldehydes and Ketones Ketones and aldehydes are related in that they each possess a C=O (carbonyl) group. They differ in that the carbonyl carbon in ketones is bound to two carbon atoms (RCOR’), while that in aldehydes is bound to at least one hydrogen (H2CO and RCHO). Thus aldehydes always place the carbonyl group on a terminal (end) carbon, while the carbonyl group in ketones is always internal. Some common examples include (common name in parentheses): O O H HH methanal (formaldehyde) trans-3-phenyl-2-propenal (cinnamaldehyde) preservative oil of cinnamon O O propanone (acetone) 3-methylcyclopentadecanone (muscone) nail polish remover a component of one type of musk oil Simple aldehydes (e.g. formaldehyde) typically have an unpleasant, irritating odor. Aldehydes adjacent to a string of double bonds (e.g. 3-phenyl-2-propenal) frequently have pleasant odors. Other examples include the primary flavoring agents in oil of bitter almond (Ph- CHO) and vanilla (C6H3(OH)(OCH3)(CHO)). As your book says, simple ketones have distinctive odors (similar to acetone) that are typically not unpleasant in low doses. Like aldehydes, placing a collection of double bonds adjacent to a ketone carbonyl generally makes the substance more fragrant. The primary flavoring agent in oil of caraway is just a such a ketone. 2 O oil of carraway Because the C=O group is polar, small aldehydes and ketones enjoy significant water solubility. They are also quite soluble in typical organic solvents. 14.2 Naming Aldehydes and Ketones Aldehydes The IUPAC names for aldehydes are obtained by using rules similar to those we’ve seen for other functional groups (e.g. -
Reactions of Benzene & Its Derivatives
Organic Lecture Series ReactionsReactions ofof BenzeneBenzene && ItsIts DerivativesDerivatives Chapter 22 1 Organic Lecture Series Reactions of Benzene The most characteristic reaction of aromatic compounds is substitution at a ring carbon: Halogenation: FeCl3 H + Cl2 Cl + HCl Chlorobenzene Nitration: H2 SO4 HNO+ HNO3 2 + H2 O Nitrobenzene 2 Organic Lecture Series Reactions of Benzene Sulfonation: H 2 SO4 HSO+ SO3 3 H Benzenesulfonic acid Alkylation: AlX3 H + RX R + HX An alkylbenzene Acylation: O O AlX H + RCX 3 CR + HX An acylbenzene 3 Organic Lecture Series Carbon-Carbon Bond Formations: R RCl AlCl3 Arenes Alkylbenzenes 4 Organic Lecture Series Electrophilic Aromatic Substitution • Electrophilic aromatic substitution: a reaction in which a hydrogen atom of an aromatic ring is replaced by an electrophile H E + + + E + H • In this section: – several common types of electrophiles – how each is generated – the mechanism by which each replaces hydrogen 5 Organic Lecture Series EAS: General Mechanism • A general mechanism slow, rate + determining H Step 1: H + E+ E El e ctro - Resonance-stabilized phile cation intermediate + H fast Step 2: E + H+ E • Key question: What is the electrophile and how is it generated? 6 Organic Lecture Series + + 7 Organic Lecture Series Chlorination Step 1: formation of a chloronium ion Cl Cl + + - - Cl Cl+ Fe Cl Cl Cl Fe Cl Cl Fe Cl4 Cl Cl Chlorine Ferric chloride A molecular complex An ion pair (a Lewis (a Lewis with a positive charge containing a base) acid) on ch lorine ch loronium ion Step 2: attack of -
Page 1 of 108 RSC Advances
RSC Advances This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. This Accepted Manuscript will be replaced by the edited, formatted and paginated article as soon as this is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/advances Page 1 of 108 RSC Advances Applications of oxazolidinones as chiral auxiliaries in the asymmetric alkylation reaction applied to total synthesis Majid M. Heravi,* Vahideh Zadsirjan, Behnaz Farajpour Department of Chemistry, School of Science, Alzahra University, Vanak, Tehran, Iran Email: [email protected] Abstract Various chiral oxazolidinones (Evans' oxazolidinones) have been employed as effective chiral auxiliaries in the asymmetric alkylation of different enolates. This strategy has been found promising and successful when used as key step (steps) in the total synthesis of several biologically active natural products. In this report, we try to underscore the applications of Manuscript oxazolidinones as chiral auxiliary in asymmetric alkylation, and particularly in crucial chiral inducing steps in the total synthesis of natural products, showing biological activities.