Oxidation of Primary Alcohols to Carboxylic Acids
BASIC REACTIONS IN ORGANIC SYNTHESIS EDITOR-IN-CHIEF: GABRIEL TOJO DEPARTMENT OF ORGANIC CHEMISTRY FACULTY OF CHEMISTRY UNIVERSITY OF SANTIAGO DE COMPOSTELA 15872-SANTIAGO DE COMPOSTELA SPAIN qogatojo@usc.es Oxidation of Alcohols to Aldehydes and Ketones: A Guide to Current Common Practice, by Gabriel Tojo and Marcos Fernández Oxidation of Primary Alcohols to Carboxylic Acids: A Guide to Current Common Practice, by Gabriel Tojo and Marcos Fernández
Oxidation of Primary Alcohols to Carboxylic Acids A Guide to Current Common Practice GABRIEL TOJO and MARCOS FERNÁNDEZ
Authors: Gabriel Tojo Department of Organic Chemistry Faculty of Chemistry University of Santiago de Compostela 15872-Santiago de Compostela Spain Marcos Fernández Department of Organic Chemistry Faculty of Chemistry University of Santiago de Compostela 15872-Santiago de Compostela Spain Editor-in-Chief Gabriel Tojo Department of Organic Chemistry Faculty of Chemistry University of Santiago de Compostela 15872-Santiago de Compostela Spain Library of Congress Control Number: 2006929452 ISBN-10: 0-387-35431-X ISBN-13: 978-0387-35431-6 e-isbn-10: 0-387-35432-8 e-isbn-13: 978-0387-35432-3 Printed on acid-free paper. 2007 Springer Science+Business Media, LLC All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. 10987654321 springer.com
This book is dedicated to the thousands of scientists cited in the references who constructed our present knowledge on the oxidation of primary alcohols to carboxylic acids. Thanks to their collective effort, the preparation of medicines, pesticides, colorants, and a variety of chemicals that make life more enjoyable, is greatly facilitated.
Preface to the Series There is natural selection in the synthetic organic laboratory. Successful reagents find their way into specialized journals and tend to populate researchers benches. Sometimes, old species like active manganese dioxide in the oxidation of unsaturated alcohols are so well adapted to a certain reaction niche that they remain unchallenged for a long time. On other occasions, a successful new species like Dess Martin periodinane enjoys a population explosion and very quickly inhabits a great number of laboratories. On the other hand, the literature is filled with promising new reagents that fell into oblivion because nobody was able to replicate the initial results on more challenging substrates. This series, which consists of a collection of monographs on basic reactions in organic synthesis, is not primarily aimed at specialized researchers interested in the development of new reagents. Rather, it is written with the objective of being a practical guide for any kind of scientist, be it a chemist of whatever sort, a pharmacologist, a biochemist, or whoever has the practical need to perform a certain basic synthetic operation in the quickest and most reliable way. Therefore, great emphasis is given to those reagents that are employed most often in laboratories, because their ubiquity proves that they possess a greater reliability. Reagents appearing in only a few publications, regardless of promising potential, are only briefly mentioned. We prefer to err on the side of ignoring some good reagents, rather than including bad reagents that would lead researchers to lose precious time. The books from this series are meant to be placed near working benches in laboratories, rather than on the shelves of libraries. That is why full experimental details for important reactions are provided. Although many of references from the literature are facilitated, this series is written with the aim of avoiding as much as possible the need to consult original research articles. Many researchers do not have scientific libraries possessing numerous chemical journals readily available, and, many times, although such libraries might be on hand, it is inconvenient to leave the laboratory in order to consult some reference. Our aim is to facilitate practical help for anybody preparing new organic compounds. vii
Preface There is a common view among organic chemists that simple functional group transformations are a mature technology away from the forefront in the Art of Organic Synthesis. This is undoubtedly not the case in the conversion of primary alcohols into carboxylic acids. An ideal reagent for such transformation should be (1) reliable and efficient with regard to all molecules, including complex structures possessing oxidation-sensitive functional groups, (2) cheap, and (3) environmentally friendly. There is no such reagent, even if we limit ourselves to the more mundane need of anything able to provide a certain muchneeded carboxylic acid, regardless of price and ecology. This state of affairs is highlighted by the fact that in forty percent of cases the oxidation of primary alcohols to acids is performed using a two-step procedure via the corresponding aldehydes; something that proves that the oxidation of alcohols to aldehydes is a much more mature technology than the oxidation of alcohols to carboxylic acids. This monograph is a laboratory guide for the transformation of primary alcohols into carboxylic acids. It displays a panorama of the state of the art for this functional group transformation, highlighting the weaponry currently available for scientists and areas where further progress is needed. In conformity with the rest of the series, a selection is made to include those procedures that have proved more reliable in many laboratories around the globe. ix
Abbreviations Ac Alloc BAIB Bn Boc b.p. Bu t-bu Bz ca. CA cat. Cbz DCAA DCC DMF DMP DMSO ee EE eq. Et Fmoc g h i-pr L m M MCPBA acetyl allyloxycarbonyl bis(acetoxy)iodobenzene benzyl t-butoxycarbonyl boiling point n-butyl tert-butyl benzoyl circa Chemical Abstracts catalytic benzyloxycarbonyl dichloroacetic acid N N -dicyclohexyl carbodiimide dimethylformamide Dess-Martin periodinane dimethyl sulfoxide enantiomeric excess 1-ethoxyethyl equivalent ethyl 9-fluorenyl methoxycarbonyl gram hour isopropyl liter multiplet mol/l m-chloroperoxybenzoic acid Me MEM min. MOM MS MTBE MW NCS NMO NMR PCC PDC Ph PhF Pht PMB ppm Pr Py ref. r.t. sat. T TBDPS TBS TEMPO TFA TFAA methyl (2-methoxyethoxy)methyl minute methoxymethyl molecular sieves methyl t-butyl ether molecular weight N -chlorosuccinimide N -methylmorpholine N -oxide nuclear magnetic resonance pyridinium chlorochromate pyridinium dichromate phenyl 9-phenylfluorenyl phthaloyl p-methoxybenzyl parts per million propyl pyridine reflux room temperature saturated temperature t-butyldiphenylsilyl t-butyldimethylsilyl 2,2,6,6-tetramethyl- 1-piperidinyloxy free radical trifluoroacetic acid trifluoroacetic anhydride xi
xii Abbreviations THF THP T i TIPS TMS tetrahydrofuran tetrahydropyran-2-yl internal temperature triisopropylsilyl trimethylsilyl TPAP v w Z tetrapropylammonium perruthenate volume weight benzyloxycarbonyl
Contents 1. Permanganate... 1 1.1. Introduction... 1 1.2. General Procedure for Oxidation of Primary Alcohols to Carboxylic Acids with Potassium Permanganate... 5 1.3. Functional Group and Protecting Group Sensitivity to Potassium Permanganate... 7 1.4. Side Reactions... 9 1.5. References... 10 2. Jones and Other CrO 3 -Based Oxidations... 13 2.1. Introduction... 13 Mechanism... 13 Inverse Addition... 15 Solvent... 16 Acidity... 17 Zhao s Catalytic CrO 3 Oxidation... 18 2.2. General Procedure for Oxidation of Primary Alcohols to Carboxylic Acids with Jones Reagent... 19 2.3. Functional Group and Protecting Group Sensitivity to Jones Oxidation... 21 2.4. Side Reactions... 25 2.5. References... 28 3. Pyridinium Dichromate (PDC) in Dimethylformamide. The Method of Corey and Schmidt... 33 3.1. Introduction... 33 3.2. General Procedure for Oxidation of Aliphatic Primary Alcohols to Carboxylic Acids with Pyridinium Dichromate in Dimethylformamide. Method of Corey and Schmidt... 34 3.3. Functional Group and Protecting Group Sensitivity to PDC in DMF 36 3.4. Side Reactions... 38 3.5. References... 39 xiii
xiv Contents 4. Heyns Oxidation... 43 4.1. Introduction... 43 Solvent... 45 ph... 46 Oxygen... 48 Platinum... 48 Poisons... 49 Selectivity... 50 Application... 52 4.2. General Procedure for Heyns Oxidation of Primary Alcohols to Carboxylic Acids... 52 4.3. Functional Group and Protecting Group Sensitivity to Heyns Oxidation... 55 4.4. Side Reactions... 56 4.5. References... 58 5. Ruthenium Tetroxide and Other Ruthenium Compounds... 61 5.1. Introduction... 61 Procedure of Pappo and Becker... 61 Sharpless Modification... 62 Mechanism... 63 Solvent... 63 Buffering... 65 RuO 4 Source... 65 Secondary Oxidant... 66 Ruthenate and Perruthenate Oxidations... 66 Application... 68 5.2. General Procedure for Oxidation of Primary Alcohols to Carboxylic Acids with Catalytic RuO 4... 68 5.3. Functional Group and Protecting Group Sensitivity to Oxidation with Catalytic RuO 4... 70 5.4. Side Reactions... 74 5.5. References... 76 6. TEMPO-Mediated Oxidations... 79 6.1. Introduction... 79 Mechanism... 81 Stoichiometric Oxidants... 83 Amino 1-Oxyl Radicals... 83 6.2. Anelli s Oxidation... 83 Solvent... 85 Catalyst... 86 Phase-Transfer Catalyst... 87
Contents xv ph... 87 Selectivity... 88 6.2.1. General Procedure for Oxidation of Primary Alcohols to Carboxylic Acids by Anelli s Oxidation... 90 6.3. Zhao s Modification of Anelli s Oxidation... 93 6.3.1. General Procedure for Oxidation of Primary Alcohols to Carboxylic Acids by Zhao s Modification of Anelli s Oxidation... 94 6.4. Oxidation of Epp and Widlanski... 96 Mechanism... 96 Selectivity... 97 6.4.1. General Procedure for Oxidation of Primary Alcohols to Carboxylic Acids by the Protocol of Epp and Widlanski... 98 6.5. Functional Group and Protecting Group Sensitivity to TEMPO-Mediated Oxidations... 99 6.6. Side Reactions... 100 6.7. References...101 7. Oxidation of Alcohols to Carboxylic Acids via Isolated Aldehydes...105 7.1. Introduction...105 7.2. References...109 Index...111