PHASE~ TRANSFER CATALYSIS

Charles L. Liotta Department of Chemistry Georgia Institute of Technology Atlanta, GA 30332

Charles M. Starks Cimmaron Technical Associates Tulsa, OK 74119

Marc E. Halpern Sybron Chemicals Cherry Hill, NJ 08002

PHASE-TRANSFER CATALYSIS

Fundamentals, Applications, and Industrial Perspectives

CHARLES M. STARKS CHARLES L. LIOTTA

MARC HALPERN

SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

© 1994 Springer-Science+Business Media Dordrecht Originally published by Chapman & Hall in 1994 Softcover reprint of the hardcover 1st edition 1994

Ali rights reserved. No part of this book may be reprinted or reproduced or utilized in any form or by any electronic, mechanical or other means, now known or hereafter invented, including pho­tocopying and recording, or by an information storage or retrieval system, without permission in writing from the publishers.

Library of Congress Cataloging in Publication Data

Starks, Charles M., 1934-Phase-transfer catalysis : fundamentals, applications & industrial

perspectives 1 Charles Starks, Charles Liotta, and Mare Halpern. p. cm.

Includes bibliographical references and index. ISBN 978-94-010-4297-0 ISBN 978-94-011-0687-0 (eBook) DOI 10.1007/978-94-011-0687-0 l. Phase-transfer catalysis. 1. Liotta, Charles L., 1937-

Il. Halpern, Mare, 1954- III. Title. QD505.L56 1993 661'.8-dc20 93-19659

CIP

British Library Cataloguing in Publication Data available

Contents

Preface

Chapter 1: Basic Concepts in Phase-Transfer Catalysis A. Phase-Transfer-Catalyzed Reactions B. Basic Steps of Phase-Transfer Catalysis C. The PTC Reaction Rate Matrix D. Anion Transfer and Anion Activation

1. Transfer 2. Anion Activation

E. Effect of Reaction Variables on Transfer and Intrinsic Rates 1. Catalyst Structure 2. Agitation 3. Kind and Concentration of Inorganic Reagent; Amount of Water

Added 4. Amount and Kind of Organic Solvent Used, If Any 5. Temperature and Microwave Heating 6. Cocatalysts

F. Outline of Compounds Used as Phase-Transfer Catalysts 1. Soluble Catalysts 2. Insoluble Catalysts 3. Catalysts for Vapor-Phase Reactions

xiii

1 2 5 6 6

11 12 13 14 15

16 17 17 18 18 20 21

Chapter 2: Phase-Transfer Catalysts: Fundamentals I 23 A. Introduction 23 B. Structural Factors Affecting the Distribution of Anions Between 24

Aqueous and Organic Phases C. Structural Factors Affecting the Distribution of Phase-Transfer Catalyst 26

Cations Between the Aqueous and Organic Phases D. Effects of the Organic Phase Polarity on the Distribution of Phase- 29

Transfer Cation-Anion Pairs

v

vi / Contents

E. Effects of Changes in Organic Phase Polarity During Reaction 31 F. Factors Affecting the Distribution of Phase-Transfer Catalyst Cation- 32

Anion Pairs Between an Organic Phase and an Aqueous Phase Containing Hydroxide Ion

G. Effect of Hydration of the Transferred Anion and the Effect of Inorganic 40 Salt and/or Hydroxide Concentration in the Aqueous Phase

Chapter 3: Phase-Transfer Catalysis: Fundamentals II 48 A. Introduction 48 B. Liquid-Liquid PTC 49

I. Simple Displacement Reactions 49 2. Hydroxide-Promoted Reactions of Organic Acids 89 3. Alternative PTC Mechanisms Involving Hydroxide Ion 106

C. Solid-Liquid PTC 108 I. Complexation and Solubilization of Potassium Salts with 18-Crown-6 III 2. Simple Displacement Reactions 113

Chapter 4: Phase-Transfer Catalysts 123 A. Introduction 123 B. Use of Quaternary Salts as Phase-Transfer Catalysts 125

1. Simple Tetraalkyl-Onium Salts as Phase-Transfer Catalysts 125 2. Special Quaternary Salts as Phase-Transfer Catalysts 142

C. Macrocyclic and Macrobicyclic Ligands 153 1. Simple Crown Ethers 153 2. Cryptands 155 3. Special Crowns 156

D. PEGs, Tris (3,6-dioxaheptyl)amine (TDA-I), and Related Ethoxylated 158 Compounds as Phase-Transfer Catalysts 1. Synthesis of PEGs 158 2. Phase Distribution Behavior of PEGs 159 3. PEGs and Ethers as Phase-Transfer Catalysts 162 4. Special Ethoxylate Structures: Ethoxylate Derivatives as PTC 165

Catalysts E. Other Soluble Polymers and Related Multifunctional Compounds as 171

Phase-Transfer Catalysts F. Use of Dual PTC Catalysts or Use of Cocatalysts in Phase-Transfer 175

Systems I. Use of Dual PTC Catalysts 176 2. Use of Alcohols and Other Weak Acids as Cocatalysts in Hydroxide 177

Transfer Reactions 3. Use of Metal Compounds and Salts as PTC Cocatalysts 178 4. Use of Iodide as a Cocatalyst 179

G. Catalysts for Transfer of Species Other Than Anions 179 I. Inverse PTC: Transfer of Organic Reagents into Aqueous Solutions 179 2. Transfer of Acids 183 3. Transfer of Water 184 4. Transfer of Metals and Metal Hydrides 185

Contents / vii

5. Transfer of Anhydrous Aluminum Chloride 185 6. Transfer of Formaldehyde 186 7. Cation Transfer 186 8. Transfer of Radical Anions 186 9. Transfer of Ammonia 187

10. Transfer of Oxygen 187 H. Separation and Recovery of Phase-Transfer Catalysts 188

I. Extraction Methods 188 2. Distillation Methods 189

Chapter 5: Insoluble Phase-Transfer Catalysts 207 A. Introduction 207 B. PTC Catalysts Bound to Insoluble Resins 208

I. Basic Differences Between Soluble and Insoluble PTC Catalysts: The 208 Importance of Diffusion Processes

2. Some Examples of Use of Resin-Bound PTC Catalysts and 210 Comparisons with Soluble Catalysts

3. Preparation of Resin-Bound PTC Catalysts 210 4. Effects of Reaction and Catalyst Parameters on Triphase Catalyst 221

Effecti veness 5. Kinetics of Reactions Catalyzed by Resin-Bound PTC Groups 247

C. Phase-Transfer Catalysts Bound to Inorganic Solid Supports 248 I. PTC Catalysts Adsorbed on Inorganic Supports 249 2. Catalysts with PTC Function Chemically Bonded to Inorganic 250

Supports D. PTC Catalysts Contained in a Separate Liquid Phase (Third-Liquid- 252

Phase Catalyst)

Chapter 6: Variables in Reaction Design for Laboratory and Industrial 266 Applications of Phase-Transfer Catalysis A. Choice of Catalyst 266

I. Structure-Activity Relationships of Quaternary Ammonium Catalysts 267 2. Structure-Activity Relationships-Other Catalysts 286 3. Catalyst Stability 288 4. Catalyst Separation and Recycle 291 5. Commercial Catalyst Reference 303

B. Choice of Solvent 303 I. Choice of Solvent and the Nature of the Chemical Reaction 305 2. Stabilization of the Transition State and Solvation of the Anion 306 3. Solubility of the Catalyst-Anion Pair/Complex in the Organic Phase 307 4. Rate of Transfer 307 5. Solvent and the Nature of the Two Phases 6. Examples of Effect of Solvent 7. "Solvent-Free" PTC 8. Choice of Solvent and Process Aspects

C. Presence of Water D. Agitation

310 311 314 315 318 319

viii / Contents

E. Choice of Anion, Leaving Group, and Counteranion F. Choice of Base G. Guidelines for Exploring New PTC Applications

322 325 326

Chapter 7: Phase-Transfer Catalysis Displacement Reactions with Simple 339 Anions A. General Considerations

I. Important Factors in PTC Displacement Reactions 2. Characteristics of Various Anions for Simple PTC Displacement

Reactions 3. PTC Catalysts for Simple Displacement Reactions

B. Behavior of Various Anions in PTC Displacement Reactions I. Cyanide Displacements 2. Halide Displacement and Exchange Reactions 3. Displacements with Carboxylate Anions 4. Azide Displacements 5. Sulfide and Disulfide Displacements 6. Thiocyanate Displacement 7. Sulfite Displacement 8. Nitrite Displacement 9. Hydroxide Anion Displacements

10. Carbonate and Bicarbonate Anion Displacement II. Displacement with Peroxide and Superoxide Anions 12. Phosphide and Phosphinite Anion Displacements 13. Cyanate Anion Displacements

Chapter 8: Phase-Transfer Catalysis Reaction with Strong Bases A. C-Alkylation

1. Ketones 2. Aldehydes 3. Esters and Carboxylic Acids 4. Imines 5. Nitriles 6. Sulfones 7. Hydrocarbons

B. N-Alkylation I. Nitrogen-Containing Heterocycles 2. Amides 3. Amines

C. 0-Alkylation-Etherification I. Etherification of Alkoxides 2. Etherification of Phenoxides

D. S-Alky lation-Thioetherification E. Dehydrohalogenation F. Carbene Reactions

1. Dichlorocarbene Addition 2. Dibromocarbene Addition

339 340 342

342 343 343 347 355 358 362 364 366 366 367 368 369 370 370

383 384 384 391 392 392 395 397 398 400 400 406 408 410 410 413 418 420 424 424 426

Contents / ix

3. Mixed Dihalocarbene Addition 427 4. Other Reactions of Chloroform or Alternate Methods of Generating 427

Carbenes Under PTC/OH Conditions G. Condensation Reactions 430

I. Michael Addition 430 2. Aldol Condensation 431 3. Wittig 433 4. Darzens 435 5. Other Condensations 437

H. Deuterium Exchange, Isomerization, and Oxidation 438

Chapter 9: Phase-Transfer Catalysis: Polymerization and Polymer 452 Modification A. Introduction 452 B. Polymer Synthesis 452

I. Condensation Polymerization 452 2. Anionic Polymerizations 479 3. Radical-Initiated Polymerizations 481

C. Chemical Modification of Polymers 484 1. Chemical Modification of Polymer Backbone 484 2. Chemical Modification of Polymer Terminal Positions 489 3. Chemical Modification of Pendant Groups Attached to Polymer 490

Backbone

Chapter 10: Phase-Transfer-Catalyzed Oxidations 500 A. Introduction 500 B. Permanganate Oxidations 500

1. General Comments 500 2. Transfer of Permanganate into Organic Phases 501 3. PTC Permanganate Oxidations 503

C. Oxidations with Hypochlorite and Hypobromite 508 I. Hypochlorite Compositions in Aqueous Solutions 508 2. Oxidation of Alcohols and Carbonyl Compounds 508 3. Oxidation of Amines, Amides, Thioamides, and Related Compounds 512 4. Oxidation of Sulfides and Related Compounds 514 5. Oxidation of Olefins 514 6. Oxidation of Nonolefinic Hydrocarbons 518

D. PTC Oxidations with Hydrogen Peroxide 521 1. Hydrogen Peroxide Transfer into Organic Solutions 521 2. Hydrogen Peroxide Oxidations 522

E. PTC Air or Oxygen Oxidations 534 1. Carbanion Oxidations 534 2. PTC Involvement in Free-Radical Oxidations 538 3. PTC Oxidation with "Activated" Oxygen Carriers 538 4. PTC with Singlet Oxygen Generation 539 5. Transition-Metal-Mediated Oxidations Involving PTC 540

F. Oxidations by Persulfates 540

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2. Electrochemical Regeneration of Chromium Oxidants in Combination 547 with PTC Systems

H. PTC Oxidations with Nitric Acid 547 I. PTC Carbon Tetrachloride/Sodium Hydroxide Oxidations 548 J. PTC Oxidations with Periodate and Related Oxidizing Anions 549

1. Osmium as Cocatalyst 549 2. Ruthenium as Cocatalyst 550

K. PTC Oxidations with Perborate 550 L. PTC Oxidations with Ferrate and Ferricyanide 550 M. PTC Oxidations with Superoxide 551 N. PTC Electrochemical Oxidations 551 O. PTC Oxidations with Other Oxidants 552

Chapter II: Phase-Transfer-Catalyzed Reductions 565 A. Sodium Borohydride Reductions 565

1. Reduction of Carbonyl Compounds 565 2. Azide Reductions 566 3. Other PTC Borohydride Reductions 567

B. Lithium Aluminum Hydride Reductions 568 C. Reductions with Sodium Formate 568 D. Reductions with Sulfur-Containing Anions 569 E. Hydrogenation 570 F. Reductions with Formaldehyde 571 G. Electrochemical Reduction 571 H. Photochemical Reduction 572 I. Wolff-Kishner Reduction 572 J. Reduction by Dodecarbonyltriiron and Related Species 572

Chapter 12: Phase-Transfer Catalysis: Chiral Phase-Trans fer-Catalyzed 576 Formation of Carbon-Carbon Bonds A. Introduction 576 B. Alkylation Reactions 577

1. Methylation of 6.7-Dichloro-5-methoxy-2-phenyl-I-indanone 577 2. Alkylation of 2.3-Dichloro-5-methoxy-2-n-propyl-I-indanone with 584

1.3-Dichloro-2-butene in Toluene-50% Aqueous Sodium Hydroxide 3. Asymmetric Alkylation of Oxindoles 586 4. Synthesis of Chiral Amino Acids 587 5. Michael Addition Reactions 589

Chapter 13: Phase Transfer Catalysis-Transition Metal Cocatalyzed 594 Reactions A. Introduction 594 B. Carbonylation and Reactions with Carbon Monoxide 595

I. Formation of Metal Carbonyl Anions 595 2. Carbonylation of Alkyl Halides and Aryl Halides 595 3. Carbonylation of Olefins 600 4. Carbonylation of Acetylenes 602

Contents / xi

5. Carbonylation of Aziridines and Azobenzenes 604 6. Carbonylation of Thiiranes 605 7. Carbonylation Reaction with Phenol 605

B. PTC Reduction and Hydrogenation with Metal Cocatalysts 605 1. Hydrogenolysis of Aryl and Alkyl Halides 605 2. Reduction of Acid Chloride Groups to Aldehydes 609 3. Hydrogenation of Arenes, Olefins, and Carbonyl Compounds 609 4. Reduction of Nitrogen Compounds 610 5. Other Reductions and Hydrogenations 613

C. Coupling Reactions of Alkenes, Alkynes, and Alkyl Halides 613 1. Acetylene and Olefin Reactions with Halo-compounds 613 2. Acetylene and Olefins Coupling Reactions 616

D. Other Reactions 617

Chapter 14: Phase-Transfer Catalysis in Analytical Chemistry 622 A. The PTCI Analytical Chemistry Match 622 B. Esterification, Etherification, and Other Nucleophilic Derivatizations 622 C. Non-Nucleophilic PTC Reactions Used in Analytical Chemistry 623

Chapter 15: Phase-Transfer Catalysis: Industrial Perspectives 626 A. Industrial Background 626 B. Evaluation of PTC as a Commercial Manufacturing Process Technology 626

1. General Considerations 626 2. Advantages of PTC-Industrial Viewpoint 627 3. Limitations of PTC and Barriers to Commercialization 631 4. Identifying Future Opportunities for Making Economic Impact Using 635

PTC 5. Conclusion 637

Index 639

Preface

Since 1971 when useful working concepts for the technique of phase-transfer catalysis (PTC) were introduced, the understanding, development, and applica­tions of this method for conducting organic reactions has expanded exponentially. PTC has brought vast new dimensions and options to chemists and chemical engineers. From its use in less than ten commercial processes in 1975, PTC use has increased so that in the early 1990s it is involved in more than 600 industrial applications to manufacture products valued at between 10 and 20 billion U.S. dollars. PTC is widely used for simple organic reactions, steps in synthesis of pharmaceuticals, agricultural chemicals, perfumes, ftavorants, and dyes; for specialty polymerization reactions, polymer modifications, and monomer synthe­sis; for pollution and environmental control processes; for analysis oftrace organic and inorganic compounds; and for many other applications. Often, PTC offers the best (and sometimes only) practical technique to obtain certain products.

The authors experience in teaching a short course on phase-transfer catalysis has shown to us that a newcomer to PTC can easily be frustrated and confused by the large amount of information available in the literature and in patents. The purpose of this book, therefore, was to bring this information together in a logical and user-friendly way, without sacrificing matters of scholarly and fundamental importance.

Concurrently with the proliferation of PTC applications, many advances in understanding of the mechanistic aspects of PTC have been made. These are extremely important to understand if one is to devise optimal reactions based on phase-transfer catalysis. Of particular value for understanding the fundamental steps within the PTC technique has been the recent elaboration of how the detailed kinetics of the various PTC steps affect the overall rates of conversion within PTC reactions, a topic fully described for the first time in this book. Although these kinetics can be very complex, one of the authors (CLL) has devised simple

xiii

xiv I Preface

computer routines that easily handle the most complicated of PTC processes for chemists who have not had extensive experience in using kinetic data.

Selection of catalyst and other reaction conditions in PTe reactions is often found to be the most confusing aspect in the use of the PTe technique. This confusion results from the wide array of different catalysts that have been reported in the chemical literature, further complicated by the fact that sometimes the choice of catalyst is of extreme importance while in other situations the reaction proceeds very well with almost any PTC catalyst. Use of insoluble PTC catalysts, either solid or liquid, greatly expands the scope of PTe reactions. While they simplify procedures because they are easy to remove and reuse, their use usually demands great care in development and selection of catalysts and reaction condi­tions. Aspects of catalyst selection, including not only activity but toxicity, cost, recovery, reuse, and stability appear in almost every chapter of this book. Considerable attention has been devoted in Chapters 4,5, and 6 toward reviewing and comparison of various materials used as phase transfer catalysts, and toward selection criteria for catalysts.

Other variables are also of concern in phase-transfer catalysis, and these are outlined in Chapter 6 along with some guidelines about exploration of new PTC reactions. One of the most beneficial features of phase-transfer catalysis is the ability greatly to expand the list of solvents that can be used in a given reaction, or even in many cases to omit a solvent altogether. Chapter 6 discusses aspects of solvent choice on PTC reactions, along with other practical concerns, such as the presence of water, agitation, choice of bases in base reactions, and commercial sources and relative costs of PTC catalysts.

The last half of this book is devoted to the chemistry and application of the PTC technique toward specific kinds of commonly used PTC reactions and processes. These chapters are not intended to review exaustively all the PTC chemistry reported in the chemical literature, but rather to illustrate with specific examples how the technique has been used with basic reactions as well as with subtle and advanced ideas on how to use PTC in special ways.

It is our belief that phase-transfer catalysis will continue to grow and be used extensively by organic chemists and engineers in both new developments and in improving old processes. Over the last 15 years, no decrease has been found in the frequency which phase-transfer catalysis is indexed in Chemical Abstracts. PTCs ability to be used beneficially in conjunction with polymers, electrochemis­try, photochemistry, and various co-catalysts is still accelerating, and its substan­tial cost-reductions and avoidance of noxious and expensive reagents and solvents continues to find increasing use in a wide variety of processes. Although design and development of PTe-based processes is more difficult than use of classical chemical procedures, profitable results usually repay the extra development effort many times over.