DOCSLIB.ORG

Sem-Iii, Core Course-7 Organic Chemistry-3 Topic

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Sem-Iii, Core Course-7 Organic Chemistry-3 Topic SEM-III, CORE COURSE-7 ORGANIC CHEMISTRY-3 TOPIC: CARBONYL AND RELATED COMPOUNDS Dr. Kalyan Kumar Mandal Associate Professor St. Paul’s C. M. College Kolkata PPT: 4 • OPPENAUER OXIDATION • OXIDATION OF ALCOHOLS WITH PDC AND PCC • PERIODIC ACID AND LEAD TETRAACETATE OXIDATION OF 1,2-GLYCOLS OPPENAUER OXIDATION Oxidation of primary and secondary alcohols to aldehydes and ketones respectively using aluminium tertiary butoxide in presence of a hydride ion acceptor like acetone, cyclohexanone, benzophenone p-benzoquinone, etc., is called Oppenauer oxidation. Facts • In case of oxidation of primary alcohol, non-enolisable ketones with a relatively low reduction potential such as p-benzoquinone is used. • Tertiary butoxide is used as the reagent, since tertiary butanol produced is not oxidised under these conditions. • This reagent is particularly useful for oxidising unsaturated secondary alcohols because it does not affect the double bond. • Primary alcohols including the unsaturated alcohols may also be oxidised to aldehydes if acetone is replaced by p-benzoquinone. • In general, quinones and aromatic ketones are better hydrogen acceptors than acetone. • The reaction is completely reversible and therefore, to shift the reaction towards the product-side, addition of large excess of the hydride acceptor is used. Mechanism • Initially the starting alcohol reacts with aluminium t-butoxide to form a new alkoxide. • This intermediate alkoxide then reacts with acetone or other acceptor molecule and a hydride ion (H-) from the substrate alcohol is transferred to the carbonyl carbon atom of acetone. • The reaction proceeds through the formation of a six-membered cyclic transition state. • The specific (H-) ion transfer from the carbon atom of alcohol molecule to carbonyl carbon atom of acetone has been demonstrated by using RCD(OH)R type labelled alcohol which led to the formation of CH3CD(OH)CH3. Mechanism Oxidation of Primary Alcohols FACTS • The outcome of oxidation reactions of alcohols depends on the substituents on the carbinol carbon and in order for each oxidation step to occur, there must be at least one hydrogen atom on the carbinol carbon. • Primary alcohols can be oxidised to aldehydes or further to carboxylic acids. • Oxidation of alcohols is normally carried out with Cr(VI) reagents but these, like the Jones’ reagent (Na2Cr2O7 in H2SO4), are usually acidic. – In aqueous media, the carboxylic acid is usually the major product. – Some pyridine complexes of Cr(VI) compounds solve this problem by having the pyridinium ion (pKa 5) as the only acid. – Both PDC and PCC can convert alcohols into aldehydes and ketones, especially in dichloromethane at room temperature and allow the oxidation to be stopped at the intermediate aldehyde. – PDC is less acidic than PCC and is therefore more suitable for the oxidation of acid-sensitive substrates. OVER-OXIDATION OF ALDEHYDES • Aqueous methods like the Jones oxidation are no good for this, since the aldehyde that forms is further oxidized to acid via its hydrate. The oxidizing agent treats the hydrate as an alcohol and oxidizes it to the acid. • The key thing is to avoid water—so PCC in dichloromethane works quite well. The related reagent PDC (pyridinium dichromate) is particularly suitable for oxidation to aldehydes Pyridinium Chlorochromate (PCC) Corey-Suggs Reagent • Pyridinium chlorochromate is used as an oxidising agent in organic chemistry. • The reagent is useful to oxidise primary and secondary alcohols to the corresponding aldehydes and ketones respectively. • The oxidation of primary alcohols to aldehydes is advantageous in that sense that over oxidation to the corresponding carboxylic acid does not occur. • PCC is also important for its high selectivity. For example, when an allyl alcohol is oxidized, unsaturated aldehyde is formed as sole product. This oxidation is known as Babler oxidation. Preparation • Chlorochromic acid can by prepared by the dissolution of chromium trioxide in 6 M aqueous hydrochloric acid. Addition of pyridine gives pyridinium chlorochromate as orange crystals. • PCC is soluble in many organic solvents, and especially dichloromethane at room temperature has been used in most cases, whereas DMF promotes the over-oxidation of primary alcohols into carboxylic acids. Mechanism Pyridinium Dichromate (PDC) Pyridinium dichromate is the pyridinium salt of dichromate that can be obtained by addition of pyridine to a solution of chromium trioxide in water. FACTS • Initially, PDC was used either as a solution in DMF or as a suspension in dichloromethane. In DMF solution, PDC oxidizes primary and secondary allylic alcohols to the corresponding α,β- unsaturated carbonyl compounds. • Over-oxidation of primary allylic alcohols is not observed and (E,Z) isomerization does not take place. Mechanism with PDC OXIDATION OF 1,2-DIOLS USING • PERIODIC ACID (HIO4) • LEAD TETRAACETATE [Pb(OAc)4] • Cleavage of 1,2-diols to carbonyl compounds can be accomplished by periodic acid (HIO4) or lead tetraacetate (Pb(OAc)4]. The nature of the products depends on the nature of the substituents in the diol used. FACTS • Oxidation of 1,2-glycols occurs more rapidly with syn-diol than with the corresponding anti-isomers and this fact indicates the formation of cyclic intermediates. • The fact that anti-isomers are oxidized suggest that the reaction proceeds through a non-cyclic intermediate for these compounds. This could be the non-cyclic ester formed in the first step. • These oxidations are also subject to steric hindrance, e.g., glycol is oxidised much faster than pinacol by periodic acid. • The rate determining step for glycol oxidation is the fission of the complex, whereas that for pinacol is the formation of the complex. • The alcohol reacts to form a cyclic intermediate. The intermediate then undergoes a rearrangement of the electrons, cleaving the C-C bond and forming two C=O bonds. Mechanism with HIO4 Mechanism for the ANTI-DIOL Mechanism with Pb(OAc)4 QUESTION Write the order of rates of oxidation of the following 1,2-diols and give reasons: (i) HOCH2CH2OH (ii) MeCH(OH)CH(OH)Me (iii) Me2C(OH)C(OH)Me2 (iv) Me2C(OH)CH(OH)Me .
Load more

Recommended publications
  • United States Patent (19) (11) 4,055,601 Ehmann 45) Oct
    United States Patent (19) (11) 4,055,601 Ehmann 45) Oct. 25, 1977 (54) PROCESS FOR THE OXDATION OF PRIMARY ALLYLCALCOHOLS OTHER PUBLICATIONS Djerassi, "Organic Reactions', vol. VI, chapt. 5, pp. 75 Inventor: William J. Ehmann, Orange Park, 207-234. Fla. Adkins, et al., "J. Amer. Chem. Soc.' vol. 71, pp. (73) Assignee: SCM Corporation, New York, N.Y. 3622-3629. Batty et al., "Chem. Society Journal' (1938), pp. 21 Appl. No.: 582,114 175-179. Filed: May 30, 1975 22 Primary Examiner-Bernard Helfin Related U.S. Application Data Attorney, Agent, or Firm-Richard H. Thomas 63) Continuation-in-part of Ser. No. 437,188, Jan. 28, 1974, 57 ABSTRACT abandoned. Improved conversions of 3-substituted and 3,3-disub (51) Int. Cl’.............................................. CO7C 45/16 stituted allyl alcohols to the corresponding aldehydes (52) U.S. C. ............................ 260/593 R, 260/603 C, are obtained in an Oppenauer oxidation process, under 260/347.8; 260/599; 260/600 R; 260/598 Oppenauer oxidation conditions, by carrying out the (58) Field of Search ............ 260/603 HF, 599, 603 C, oxidation employing furfural as the hydrogen acceptor. 260/593 R, 600 R, 598 The invention is particularly applicable to the oxidation of geraniol and nerol to citral, which can be converted (56) References Cited directly to pseudoionone without purification. U.S. PATENT DOCUMENTS 2,801,266 7/1957 Schinz ........................... 260/603 HF 13 Claims, No Drawings 4,055,601 1. tion produces water as a by-product which hydrolyzes PROCESS FOR THE OXDATION OF PRIMARY and consumes the aluminum catalyst. This requires ALLYLCALCOHOLS nearly stoichiometric quantities (as compared to cata lytic quantities) of the aluminum catalyst (notice page This application is a continuation-in-part of prior 224 of Djerassi, supra).
    [Show full text]
  • Oxidation of Secondary Alcohols to Ketones
    Oxidation of secondary alcohols to ketones The oxidation of secondary alcohols to ketones is an important oxidation reaction in organic chemistry. Where a secondary alcohol is oxidised, it is converted to a ketone. The hydrogen from the hydroxyl group is lost along with the hydrogen bonded to the second carbon. The remaining oxygen then forms double bonds with the carbon. This leaves a ketone, as R1–COR2. Ketones cannot normally be oxidised any further because this would involve breaking a C–C bond, which requires too much energy.[1] The reaction can occur using a variety of oxidants. Contents Potassium dichromate PCC (Pyridinium chlorochromate) Dess–Martin oxidation Swern oxidation Oppenauer oxidation Fétizon oxidation See also References Potassium dichromate A secondary alcohol can be oxidised into a ketone using acidified potassium dichromate and heating under 2− 3+ reflux. The orange-red dichromate ion, Cr2O7 , is reduced to the green Cr ion. This reaction was once used in an alcohol breath test. PCC (Pyridinium chlorochromate) PCC, when used in an organic solvent, can be used to oxidise a secondary alcohol into a ketone. It has the advantage of doing so selectively without the tendency to over-oxidise. Dess–Martin oxidation The Dess–Martin periodinane is a mild oxidant for the conversion of alcohols to aldehydes or ketones.[2] The reaction is performed under standard conditions, at room temperature, most often in dichloromethane. The reaction takes between half an hour and two hours to complete. The product is then separated from the spent periodinane.[3] Swern oxidation Swern oxidation oxidises secondary alcohols into ketones using oxalyl chloride and dimethylsulfoxide.
    [Show full text]
  • Alcohol Oxidation
    Alcohol oxidation Alcohol oxidation is an important organic reaction. Primary alcohols (R-CH2-OH) can be oxidized either Mechanism of oxidation of primary alcohols to carboxylic acids via aldehydes and The indirect oxidation of aldehyde hydrates primary alcohols to carboxylic acids normally proceeds via the corresponding aldehyde, which is transformed via an aldehyde hydrate (R- CH(OH)2) by reaction with water. The oxidation of a primary alcohol at the aldehyde level is possible by performing the reaction in absence of water, so that no aldehyde hydrate can be formed. Contents Oxidation to aldehydes Oxidation to ketones Oxidation to carboxylic acids Diol oxidation References Oxidation to aldehydes Oxidation of alcohols to aldehydes is partial oxidation; aldehydes are further oxidized to carboxylic acids. Conditions required for making aldehydes are heat and distillation. In aldehyde formation, the temperature of the reaction should be kept above the boiling point of the aldehyde and below the boiling point of the alcohol. Reagents useful for the transformation of primary alcohols to aldehydes are normally also suitable for the oxidation of secondary alcohols to ketones. These include: Oxidation of alcohols to aldehydes and ketones Chromium-based reagents, such as Collins reagent (CrO3·Py2), PDC or PCC. Sulfonium species known as "activated DMSO" which can result from reaction of DMSO with electrophiles, such as oxalyl chloride (Swern oxidation), a carbodiimide (Pfitzner-Moffatt oxidation) or the complex SO3·Py (Parikh-Doering oxidation). Hypervalent iodine compounds, such as Dess-Martin periodinane or 2-Iodoxybenzoic acid. Catalytic TPAP in presence of excess of NMO (Ley oxidation). Catalytic TEMPO in presence of excess bleach (NaOCl) (Oxoammonium-catalyzed oxidation).
    [Show full text]
  • Short-Step Synthesis of Chenodiol from Stigmasterol
    Biosci. Biotechnol. Biochem., 68 (6), 1332–1337, 2004 Short-step Synthesis of Chenodiol from Stigmasterol y Toru UEKAWA, Ken ISHIGAMI, and Takeshi KITAHARA Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan Received February 3, 2004; Accepted March 11, 2004 Chenodiol is an important bile acid widely used for the hydroxyl group (C-3 position), 2) construction of gallstone dissolution and cholestatic liver diseases. We cis-fused rings by hydrogenation (C-5 position), 3) succeeded in a short-step synthesis of chenodiol, starting allylic oxidation and stereoselective reduction (C-7 from the safer phytosterol, stigmasterol. position), and 4) ozonolysis of the side chain and subsequent transformation, including the Wittig reac- Key words: chenodiol; stigmasterol; gallstone dissolu- tion. tion; bovine spongiform encephalopathy Our first synthetic route is outlined in Scheme 2. The hydroxyl group of stigmasterol (2) was inverted by Chenodiol is an important bile acid contained in many mesylation4,5) and the subsequent treatment with cesium vertebrates. This compound is widely used in clinical acetate.6) Inversion under Mitsunobu conditions gave a applications for the dissolution of cholesterol gallstones diastereomixture at the C-3 position, and elimination of and cholestatic liver diseases.1) At present, chenodiol is the hydroxyl group was also observed. Allylic oxidation industrially synthesized from cholic acid,2,3) a major of the C-7 position was accomplished by N-hydroxy- component of bovine bile. BSE (bovine spongiform phthalimide-catalyzed air oxidation, using benzoyl per- encephalopathy) has recently become a global problem oxide as a radical initiator.7,8) The resulting hydroper- and it is now prohibited to use the specified bovine risk oxide was dehydrated to give enone 4.
    [Show full text]
  • Transfer Hydrogenations and Kinetic Resolutions Van Dirk Klomp
    transferhydrogenations and kineticresolutions DirkKlomp transferhydrogenationsandkineticresolutions DirkKlomp Uitnodiging voorhetbijwonenvande openbareverdedigingvan hetproefschriften destellingenop maandag 13maart2006 13.00uur endedaaraan voorafgaandetoelichting voorniet-chemiciom 12.30uur indeSenaatszaalvande TechnischeUniversiteitDelft Mekelweg5teDelft Naafloopvande plechtigheidbentuookvan hartewelkomopdereceptie inhetzelfdegebouw. DirkKlomp Esdoornlaan32 1521EBWormerveer 075-6223403 [email protected] Stellingen behorende bij het proefschrift transfer hydrogenations and kinetic resolutions van Dirk Klomp 1- De door Kao et al. gebruikte structuurbepalende verbinding fructose voor de synthese van de mesoporeuze silica SBA-1 bepaalt niet de structuur van het materiaal. H.-M. Kao, C.-C. Ting, A. S. T. Chiang, C.-C. Teng, C.-H. Chen, Chem. Commun. 2005 ,1058-1060. 2- Het door Kim et al. gesuggereerde mechanisme voor de deactivering van het enzym α-CT in de hydrolyse van β-lactonen, waarbij het lacton opent op de 4-positie, is zeer onwaarschijnlijk. D. H. Kim, J. Park, S. J. Chung, J. D. Park, N.-K. Park, J. H. Han, Bioorg. Med. Chem. 2002 , 10 , 2553-2560. 3- Psychologisch gezien betekent de omschakeling door wetenschappelijke tijdschriften van papieren versies naar elektronische, een verlies aan kennis voor de wetenschapper. 4- Omdat de aarde langzamer gaat draaien is soms de toevoeging van schrikkelsecondes noodzakelijk. Wetenschappers die deze secondes pas willen toevoegen op het moment dat ze zijn opgespaard tot een schrikkeluur, omdat de toevoegingen storingen kunnen veroorzaken in elektronische apparatuur, hebben de menselijke factor uit het oog verloren. 5- In de weekeindes waarin een nieuw boek over Harry Potter uitkomt, is het aantal kinderen dat op de eerstehulpafdeling van het ziekenhuis belandt bijna half zo groot als in andere weekeindes. Gwilym et al. hebben de afname over de lange termijn waarschijnlijk onderschat.
    [Show full text]
  • Chromic Acid Oxidation of Hydrocarbons at The
    CHROMIC ACID OXIDATION OF HYDROCARBONS AT THE BENZYLIC POSITION USING THE JONES REAGENT AND C-13 NMR STUDIES OF GEM-DIMETHYL­ INDANS AND -INDANONES By Radhika Rangarajan Ii Bachelor of Science Annamalai University Annamalai Nagar, India 1979 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY December, 1984 1hes\s )ti84 D ~ \°' U,£!-­ c.o p, ~ BENZYLIC POSITION USING THE JONES REAGENT AND C-13 NMR STUDY OF GEM-DIMTHYL­ INDANS AND -INDANONES Thesis Approved: (] . Dean of the Graduate College ii 1218538 •t ACKNOWLEDGMENTS I wish to begin with expressing my whole-hearted gratitude to Dr. E. J. Eisenbraun for his care and guidance during the course of this research. My committee members Dr. R. A. Bunce, Dr. E. M. Holt and Dr. E. C. Nelson have been very helpful in carefully evaluating this work. I appreciate all their help. I would like to thank Dr. T. Rangarajan, Dr. Pourahmady, Mr. Stan Sigle and Mr. Norm Perreira, who played an important role in this investigation. I acknowledge the financial support provided by the Oklahoma State University, Department of Chemistry, Department of Energy and Dow Chemical Company during my graduate tenure. I extend my deepest appreciation to my parents, Rangarajan and Shantha Rangarajan, without whose encouragement this study would not have been possible. A special thanks is due to Mrs. Lisa Thompson for typing my manuscript. iii TABLE OF CONTENTS Chapter Page I. INTRODUCTION AND HISTORICAL. 1 II. RESULTS AND DISCUSSION •• . 15 General •••••• . 15 Oxidation of Hydrocarbons •••••••• 19 Estimation of Solvent Consumption.
    [Show full text]
  • Still More Carbonyl Chemistry
    Lecture 17 Still More Carbonyl Chemistry March 26, 2019 Chemistry 328N Second Midterm Exam ⚫ When: Tomorrow, Wednesday, 3/27 ⚫ When: 7-9 PM (please do not be late) ⚫ Where: Painter 3.02!!! ⚫ What: Covers through last Thursday’s lecture ⚫ Remember: Homework problems!! ⚫ Please…bring pencils and an eraser no calculator and no phones …….Do a good job!!! Chemistry 328N Early Exam ⚫ Authorized students with exam conflict ⚫ When: 5-7 PM Tomorrow, 3/27 ⚫ Where: ETC 2.136 ⚫ Pencil and eraser no calculator and no phone ⚫ You must stay in the exam room until 7 PM Chemistry 328N Chromic Acid Oxidations Chemistry 328N Chemistry 328N Erin Brokovich ⚫ Hexavalent chromium compounds (including chromium trioxide, chromic acids, chromates, chlorochromates) are toxic and carcinogenic. Chemistry 328N Oxidation at Benzylic Positions O H H C OH H2SO4, K2CrO4 Heat KMnO4 in Base also works Chemistry 328N Selective Chromate Oxidations ⚫ Chromic acid and heat Oxidizes benzylic positions bearing at least one hydrogen to acids ⚫ Jones Reagent (H2CrO4 in acetone) takes primary alcohols to acids and secondary alcohols to ketones…The acetone keeps the reaction cool. Jones oxidation does not oxidize benzylic positions even with a hydrogen. ⚫ PCC (pyridinium chlorochromate) is weaker yet, it only oxidizes primary alcohols to aldehydes (!) and seconday alcohols to ketones. Chemistry 328N The Jones Oxidation Examples H2 SO4 H2 CrO4, Acetone OH OH O O O C C H2SO4 H OH H 2CrO4,Acetone H3C H3C OH O H2 CrO4, Acetone Chemistry 328N PCC Oxidations C5H5N + HCl + CrO3 → [C5H5NH][CrO3Cl]
    [Show full text]
  • Alcohol Oxidations – Beyond Labz Virtual Chemlab Activity
    Alcohol Oxidations – Beyond Labz Virtual ChemLab Activity Purpose: In this virtual experiment, you will be performing two oxidation reactions of benzyl alcohol, a primary alcohol. Primary alcohols can be oxidized to aldehydes or carboxylic acids, depending on the reagents used. You will be setting up oxidation reactions using chromic acid (H2CrO4) and pyridinium chlorochromate (PCC), and comparing the products of the two reactions. You will be monitoring the reactions using thin-layer chromatography (TLC) and analyzing IR and NMR spectra of the reactants and products. O further O OH oxidation oxidation H OH benzyl alcohol benzaldehyde benzoic acid Figure 1. Oxidation reactions of benzyl alcohol Introduction: Primary alcohols can be oxidized to aldehydes or carboxylic acids, depending on the reagents used. For many years, chromium reagents were commonly used for alcohol oxidations. Because of the toxicity of chromium-based reagents, many safer oxidizing agents have been developed and are more commonly used. As this lab is virtual, we can safely explore the reactivity trends for the older, chromium-based reagents. The two reaction conditions we will be exploring in this virtual experiment are: • Jones oxidation: This reaction uses chromic acid (H2CrO4) as the oxidizing agent. Chromic acid can be formed by dissolving sodium dichromate (Na2Cr2O7) or chromium trioxide (CrO3) in aqueous sulfuric acid (H2SO4). • PCC oxidation: This reaction uses pyridinium chlorochromate (PCC) in an anhydrous solvent, typically dichloromethane (CH2Cl2). The virtual lab does not give us CH2Cl2 as an option for a solvent, so we will substitute diethyl ether (CH3CH2OCH2CH3, or Et2O). Once your two virtual experiments are complete, you will decide which set of conditions oxidizes primary alcohols to aldehydes, and which oxidizes primary alcohols to carboxylic acids.
    [Show full text]
  • 17. Oxidation and Reduction Reactions 18
    (11,12/94)(4,5/97)(02,3/07)(01/08) Neuman Chapter 17 Chapter 17 Oxidation and Reduction from Organic Chemistry by Robert C. Neuman, Jr. Professor of Chemistry, emeritus University of California, Riverside [email protected] <http://web.chem.ucsb.edu/~neuman/orgchembyneuman/> Chapter Outline of the Book ************************************************************************************** I. Foundations 1. Organic Molecules and Chemical Bonding 2. Alkanes and Cycloalkanes 3. Haloalkanes, Alcohols, Ethers, and Amines 4. Stereochemistry 5. Organic Spectrometry II. Reactions, Mechanisms, Multiple Bonds 6. Organic Reactions *(Not yet Posted) 7. Reactions of Haloalkanes, Alcohols, and Amines. Nucleophilic Substitution 8. Alkenes and Alkynes 9. Formation of Alkenes and Alkynes. Elimination Reactions 10. Alkenes and Alkynes. Addition Reactions 11. Free Radical Addition and Substitution Reactions III. Conjugation, Electronic Effects, Carbonyl Groups 12. Conjugated and Aromatic Molecules 13. Carbonyl Compounds. Ketones, Aldehydes, and Carboxylic Acids 14. Substituent Effects 15. Carbonyl Compounds. Esters, Amides, and Related Molecules IV. Carbonyl and Pericyclic Reactions and Mechanisms 16. Carbonyl Compounds. Addition and Substitution Reactions 17. Oxidation and Reduction Reactions 18. Reactions of Enolate Ions and Enols 19. Cyclization and Pericyclic Reactions *(Not yet Posted) V. Bioorganic Compounds 20. Carbohydrates 21. Lipids 22. Peptides, Proteins, and α−Amino Acids 23. Nucleic Acids **************************************************************************************
    [Show full text]
  • The Oxidation of Terminal Olefins to Methyl Ketones by Jones Reagent Is Catalyzed, by Mercury(Il)
    [Reprinted from the .Journalof Organic Chemistry'.{0. i]r77 ( 1975).l Copvright 19?5by the American Chemical Societvand reprinted bv permissionof the copyright owner. The Oxidation of Terminal Olefins to Methyl Ketones by Jones Reagent Is Catalyzed,by Mercury(Il)t Harold R. Rogers, Joseph X. McDermott,2 and George M. Whitesides* Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 ReceiuedJune 11. 1975 The oxidation of terminal olefins by Jones reagent in the presence of a catalytic quantity of mercury(II) affords good yields (>lO"t") of the corresponding methyl ketones. Similar oxidations of 1,2-disubstituted olefins gives fair (20-70%) yields; in the caseof unsymmetrically substituted olefins, mixtures of ketones are produced. The Wacker process for oxidation of olefins to ketones products) different from those of the Wacker oxidation. has three mechanistically distinct parts:3 first, activation of Mercury(Il) is an obvious candidate for the catalyst for the olefinic double bond toward nucleophilic attack by new oxidation reactions: it resembles palladium(Il) in its coordination with Pd(II) and addition of a hydroxide moi- ability to activate olefins for nucleophilic attack,a but dif- ety to this electrophilic double bond; second, conversion of fers in that decomposition of the oxymercuration products the resulting 2-hydroxyethylpalladium(Il) compound to normally generates cations by loss of mercury(0) rather ketone and a (formally) Pd(O) atom by a series of palladi- than olefins by loss of mercury hydride.s Unfortunately, um(II) hydride addition-eliminations involving vinylic al- neither we nor others6 have been able to discover a satisfac- cohol intermediates; third, reoxidation of the palladium(0) tory solution to the principal problem in developing a mer- to palladium(Il) by copper(Il).
    [Show full text]
  • Design, Synthesis and Structure-Activity
    CARLA LOPES VARELA DESIGN, SYNTHESIS AND STRUCTURE-ACTIVITY RELATIONSHIPS STUDIES ON STEROIDAL AROMATASE AND 5α-REDUCTASE INHIBITORS AS ANTI-TUMORS Faculty of Pharmacy University of Coimbra 2013 CARLA LOPES VARELA DESIGN, SÍNTESE E ESTUDOS DE RELAÇÃO ESTRUTURA- ATIVIDADE DE ESTERÓIDES INIBIDORES DA AROMATASE E DA 5α-REDUCTASE COMO ANTI-TUMORAIS Faculdade de Farmácia Universidade de Coimbra 2013 Dissertação de candidatura ao Grau de Doutor em Farmácia, Especialidade em Química Farmacêutica, apresentada à Faculdade de Farmácia da Universidade de Coimbra Aos meus pais, Guiomar e Carlos À minha avó Trindade, in memoriam Trabalho realizado sob a orientação do(a) Professor(a) Doutor Elisiário José Tavares da Silva, Faculdade de Farmácia da Universidade de Coimbra Doutora Fernanda Maria Fernandes Roleira, Faculdade de Farmácia da Universidade de Coimbra Doutora Natércia Aurora Almeida Teixeira, Faculdade de Farmácia da Universidade do Porto O presente trabalho foi realizado no Grupo de Química Farmacêutica da Faculdade de Farmácia da Universidade de Coimbra sobre a supervisão do Professor Doutor Elisiário Tavares da Silva e da Professora Doutora Fernanda Roleira, em colaboração com o Departamento de Ciências Biológicas – Laboratório de Bioquímica da Faculdade de Farmácia da Universidade do Porto e com o Grupo de Biologia da Inflamação e Repodução do Instituto de Biologia Molecular e Celular (IBMC) sob a supervisão da Professora Doutora Natércia Teixeira. Uma parte foi realizada no Departmento de Química Orgânica da Faculdade de Farmácia da Universidade de Santiago de Compostela, Espanha. Este trabalho teve o apoio financeiro da Fundação para a Ciência e Tecnologia (FCT) através da atribuição de uma bolsa de doutoramento (SFRH/BD/44872/2008) co-financiada pelo Fundo Social Europeu (FSE) e através da atribuição de um projeto FCOMP-01-0124-FEDER-020970 (PTDC/QUI- BIQ/120319/2010) financiado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do Programa Operacional Factores de Competitividade (COMPETE) e por fundos nacionais através da FCT.
    [Show full text]
  • Module I Oxidation Reactions
    NPTEL – Chemistry – Reagents and Organic reactions Module I Oxidation Reactions Lecture 1 1.1 Osmium Oxidants 1.1.1 Introduction Osmium is the densest (density 22.59 gcm-3) transition metal naturally available. It has seven naturally occurring isotopes, six of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and 192Os. It forms compounds with oxidation states ranging from -2 to +8, among them, the most common oxidation states are +2, +3, +4 and +8. Some important osmium catalyzed organic oxidation reactions follow: 1.1.2 Dihydroxylation of Alkenes Cis-1,2-dihydroxylation of alkenes is a versatile process, because cis-1,2-diols are present in many important natural products and biologically active molecules. There are several methods available for cis-1,2-dihydroxylation of alkenes, among them, the OsO4-catalzyed reactions are more valuable (Scheme 1). OsO4 vapours are poisonous and result in damage to the respiratory tract and temporary damage to the eyes. Use OsO4 powder only in a well-ventilated hood with extreme caution. Y. Gao, Encylcopedia of Reagents for Organic Synthesis, John Wiley and Sons, Inc., L. A. Paquette, New York, 1995, 6, 380. OH OsO4 Na2SO3 Et2O, 24 h OH OH OsO4 OH Na2SO3 Et O, 24 h 2 Scheme 1 Joint initiative of IITs and IISc – Funded by MHRD Page 1 of 122 NPTEL – Chemistry – Reagents and Organic reactions The use of tertiary amine such as triethyl amine or pyridine enhances the rate of reaction (Scheme 2). OH OsO4, Pyridine K2CO3, KOH OH Et O, 30 min 2 Scheme 2 Catalytic amount of OsO4 can be used along with an oxidizing agent, which oxidizes the reduced osmium(VI) into osmium(VIII) to regenerate the catalyst.
    [Show full text]