Table Of ContentHETEROGENEOUS ENANTIOSELECTIVE HYDROGENATION
Catalysis by Metal Complexes
Volume 31
Editors:
Brian James, University of British Columbia, Vancouver, Canada
Piet W. N. M. van Leeuwen, University of Amsterdam, The Netherlands
Advisory Board:
Albert S.C. Chan, The Hong Kong Polytechnic University, Hong Kong
Robert Crabtee, Yale University, U.S.A.
David Cole-Hamilton, University of St Andrews, Scotland
István Horváth, Eötvös Loránd University, Hungary
Kyoko Nozaki, University of Tokyo, Japan
Robert Waymouth, Stanford University, U.S.A.
The titles published in this series are listed at the end of this volume.
HETEROGENEOUS
ENANTIOSELECTIVE
HYDROGENATION
Theory and Practice
by
EVGENII KLABUNOVSKII
Laboratory of Asymmetric Catalysis. N.D. Zelinskii Institute of Organic Chemistry
Russian Academy of Sciences, Moscow, Russian Federation
GERARD V. SMITH
Southern Illinois University, Carbondale, IL, U.S.A.
and
ÁGNES ZSIGMOND
University of Szeged,Szeged, Hungary
AC.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN-10 1-4020-4294-9 (HB)
ISBN-13 978-1-4020-4294-2 (HB)
ISBN-10 1-4020-4296-5 (e-book)
ISBN-13 978-1-4020-4296-6 (e-book)
Published by Springer,
P.O. Box 17, 3300 AADordrecht, The Netherlands.
www.springer.com
Printed on acid-free paper
All Rights Reserved
© 2006 Springer
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Printed in the Netherlands.
CONTENTS
Preface vii
Abbreviations xi
Chapter 1. Asymmetric adsorption on minerals 1
Abstract 1
1.1. Introduction 1
1.2. Attempts of asymmetric adsorption on clays 2
1.3. Asymmetric adsorption on quartz crystals 4
1.3.1. Properties and morphology of quartz crystals 4
1.3.2. Asymmetric adsorption on quartz crystals 7
1.4. Imprinting chiral adsorbents: specifically modified silica gels 14
References 20
Chapter 2. Heterogeneous hydrogenation catalysts based on quartz 31
Abstract 31
2.1. General 31
2.2. Asymmetric hydrogenation on metal-quartz catalysts 32
2.3. General comments on adsorption and catalysis using quartz crystals 47
2.4. On the mechanism of "Quartz -catalysis" 48
2.5. Evaluation of absolute configuration of molecules using datafrom 50
"Quartz-catalysis"
References 56
Chapter 3. Heterogeneous catalysts supported on chiral carriers 63
Abstract 63
3.1. Pd-silica catalysts 63
3.2. Metal colloids as asymmetric catalysts 64
3.3. Asymmetric template catalysis 66
3.4. Metal catalysts supported on polymers 68
3.4.1. Pd-silk catalysts 69
3.4.2. Polypeptides and polysaccharides as carriers 70
References 73
Chapter 4. Hydrogenation on catalysts based on Ni and bimetals 77
Abstract 77
4.1. Background and elaboration of Ni catalysts modified with amino
and hydroxy acids 77
4.2. Preparation variables for new nickel catalysts modified with tartaric acid 87
4.3. Bimetallic and multimetallic modified hydrogenation catalysts 96
4.3.1. Supported Ni catalysts promoted with noble metals 96
4.3.2. Enantioselective lanthane-nickel intermetallic compounds 105
4.4. Modified nickel and bimetallic catalysts 112
4.4.1. Nickel-Copper catalysts 112
vi Contents
4.4.2. Cobalt and cobalt-nickel catalysts 118
4.4.3. Supported nickel-copper and nickel catalysts 119
4.4.4. Modified ruthenium and ruthenium-copper catalysts 122
4.4.5. Palladium, palladium-copper and palladium-nickel
catalysts 124
4.5. Mechanism of enantioselective hydrogenation 126
4.5.1. Enantioselectivity as a function of the bond strength in
intermediate surface complex 126
References 137
Chapter 5. Asymmetric hydrogenation of 2-oxocarboxylic acid esters
and unsaturated carboxylic acids on modified Pt and Pd
catalysts 161
Abstract 161
5.1. General 161
5.2. Properties of catalysts 170
5.2.1. Nature of metal 170
5.2.2. Nature of carrier 170
5.2.3. Zeolites as carriers 171
5.2.4. Effect of crystalline size on enantioselectivity 175
5.2.5. Enantioselective hydrogenation of C=C bond in unsaturated
carboxylic acids 180
5.3. Structure of the modifiers 186
5.3.1. Modifiers with structures similar to cinchona alkaloids 189
5.3.2. Modifiers with structures different from cinchona alkaloids 195
5.4. Structure of substrate 200
5.4.1. Hydrogenation of ketones 201
5.4.2. Effect of variables on the hydrogenation of ketopantolactone 207
5.5. Effect of solvents and additives 209
5.6. Reaction variables 216
5.7. On the mechanism of hydrogenation 220
Conclusions 238
References 238
Chapter 6. Electrochemical enantioselective reductions 267
Abstract 267
6.1. General 267
References 272
Chapter 7. Practical asymmetric catalytic reactions 275
Abstract 275
7.1. Asymmetric metal complex catalysts in industry 275
7.2. Heterogenized metal complex catalysts 279
7.3. Asymmetric hydrogenation of alpha-keto esters on chiral
metal complexes 283
7.4. Catalytic synthesis of pantolactone and other pharmaceuticals
using chiral homogeneous metal complexes 285
References 290
I n d ex 295
PREFACE
At the present time we observe the second birth of asymmetric
heterogeneous catalysis. During the past 50 years asymmetric heterogeneous
catalysis has developed from very modest results, to highly effective catalytic
systems similar to enantioselective efficiencies of chiral metal-complex
catalysts. This has been particularly true in the hydrogenation of prochiral
compounds containing double bonds, in which were demonstrated only the
principal possibility of realizing in vitro reactions similar to those occurring
in nature by enzymes.
The first attempts to carry out hydrogenation using heterogeneous
catalysts involved metals supported on dissymmetric materials of natural or
synthetic origin, such as crystals of optically active quartz and the chiral
fibers of silk or wool. These showed small asymmetric effects.
Consequently, interest in such efforts died away; moreover, these early results
were sometimes irreproducible and even were criticized as artifacts. Later
however, the early data were reproduced and confirmed as true, especially
during the 1960's, when many effective heterogeneous catalytic systems were
being elaborated using nickel catalysts modified with optically active
compounds.
At the end of the 1960's the new effective rhodium-phosphine catalyst,
the Wilkinson catalyst, was combined with chiral phosphine ligands resulting
in very effective metal-complexes which catalyze hydrogenations of prochiral
compounds (mainly C=C double bond) with optical yields close to 100%.
This success of the elaboration of chiral metal-complex catalysts mimics the
idea taken from heterogeneous asymmetric catalysis that asymmetric
reactions on the surface of metal catalysts occur through catalytic
intermediate complexes involving the molecule of chiral modifier, the
molecule of substrate, and the metal surface atoms. Application of this
concept produced homogeneous metal complex catalysts with broad practical
uses. Over one hundred novel chiral ligands were developed to produce
effective chiral homogeneous catalytic systems with high enantioselectivities
for many reactions besides hydrogenation; for example hydrosilylation,
hydroformylation, epoxidation, and oxidation.
The present interest in asymmetric catalysis was demonstrated by
awarding Nobel prizes to three winners: W. S. Knowles (USA) for elaboration of
rhodium complex catalysts effective in asymmetric synthesis of anti-
Parkinson medicine, R .Noyori (Japan) for elaboration of a new catalytic
system based on chiral ruthenium-phosphine complex catalysts that are very
effective in hydrogenation reactions, and B. Sharpless (USA) for elaboration
of epoxidation and other reactions under the action of chiral titanium
complexes.
viii Preface
These developments were achieved despite the known technological
difficulties associated with the practical use of homogeneous chiral metal-
complex catalysts. They have low durabilities and repeatabilities, the chiral
phosphine ligands are difficult to synthesize, the catalytic complexes are not
recoverable from reaction mixtures, and the most effective catalysts based on
rhodium complexes are very expensive to synthesize.
The latter difficulty could be avoided by using non-precious metals and
by immobilizing complexes onto carrier materials. But this last method did
not always give good results. All these facts encouraged a redoubling of the
efforts to further develop pure heterogeneous chiral catalytic systems.
In the 1960's works of the groups of Izumi (Osaka) and Klabunovskii
(Moscow) elaborated enantioselective heterogeneous catalytic systems
(mainly Raney nickel catalysts and other hydrogenating metal catalysts, such
as Cu, Co, Ru, Pd, bimetals, and multimetalic systems) based on modification
with chiral compounds (mainly with hydroxycarboxylic acids or amino
acids). These new catalysts, especially modified Raney nickel, were studied
in detail and the resulting works became triggers for many studies both in
heterogeneous and homogeneous enantioselective catalytic reactions.
The optical yields obtained in heterogeneous catalysis were at first not
very high and much lower than those from chiral metal complex catalysts;
however, as understanding improved, the ensuing reports, such as in the
session on enantioselective heterogeneous catalysis at the 1978 Gordon
Conference on Catalysis and in the similar session at the 1980 International
Congress on Catalysis, were beginning to show significant progress in
heterogeneous asymmetric catalysis. During that and subsequent periods
promising model compounds were developed to test the effectiveness of
newly emerging enantioselective heterogeneous catalytic systems. These
were based mainly on esters of acetoacetic acid, which, when the beta-
carbonyl group is hydrogenated, produce optically active hydroxybutyrate
esters. Eventually, some of these catalytic systems produced optical yields up
to 90%. In fact, in the case of the Ni based catalytic system modified with
R,R-tartaric acid, beta-ketoesters were hydrogenated to optical yields up to
98%, and it should be noted that this accomplishment, which is close to the
effectiveness of enzymic systems, does not use precious metals
Then during the 1990's a second very effective process of
enantioselective heterogeneous hydrogenation was developed. Using
platinum supported on alumina and modified with optically active alkaloids
of the cinchona group, the keto group of alpha-ketocarboxylic acid esters
were hydrogenated to lactates with optical yields above 95%. Thus in a short
time two types of enantioselective heterogeneous catalytic hydrogenation
systems were developed, each effective only for hydrogenation of mainly
beta- or alpha-keto esters.
Preface ix
The subsequent studies of the properties of substrate specificity and
structure sensivity allowed for elucidation of reaction mechanisms and of
modification processes as well as for the study of the phenomenon of ligand
rate acceleration for producing high enantioselectivity
This book contains many publications which represent analyses of the
steps of elaboration of effective heterogeneous enantioselective hydro-
genation catalysts, of their significant role in the theory of catalysis, and of
their role in the practice of asymmetric catalysis. In addition to reviewing the
first works on catalytic hydrogenation of C=C double bond in prochiral
compounds on metal catalysts supported on chiral carriers, which admittedly
have only historical interest, the Chapters 1-3 review data on asymmetric
adsorption of enantiomers and separation of racemic mixtures on organic and
inorganic adsorbents.
In analyzing more than 250 publications Chapter 4 covers effective
metal catalysts, mainly nickel, but also bimetal- and multimetal-systems, and
their best modifiers, amino acids and tartaric acids. It is noted that it took
more than 25 years to improve the modified nickel catalysts from their
original poorly efficient systems into the modern excellent heterogeneous
catalysts that hydrogenate carbonyl compounds with enantioselectivities of
96-98%.
The studies of platinum supported aluminum oxide modified with
optically active alkaloids of the cinchona group are considered in Chapter 5,
where more than 200 communications on this topic are summarized. The
studies of Pt-alumina catalysts modified with cinchonidine allowed for the
preparation of a number of very important chiral synthons and medicines.
These publications give substantial information for better understanding of
the mechanism of heterogeneous catalysts and of the structure of intermediate
complexes in enantioselective hydrogenation reactions.
Relatively few publications are considered in chapter 6, which is
devoted to electrochemical enentioselective reactions using electrode-
catalysts modified with optically active compounds. This method presents
significant opportunities for practical use in the synthesis of chiral
compounds.
Chapter 7 contains most of the important data on practical
enantioselective processes catalyzed by both heterogeneous enantioselective
metal catalysts and by homogeneous metal-complex catalysts.
LIST OF ABBREVIATIO NS
αt = observed optical rotation at t oC and 589 nm (D-line)
D
[α]tD = specific optical rotation of scalemic product, enantiomer mixture in
solution, determined by αtD / l x c, where l is the length of tube (dm) and
c is the sample concentration (g/ml)
[α]tl = specific optical rotation of pure optical enantiomer at t oC and l nm
wavelength
AA = amino acid
acac = acetylacetone (pentane-2,4-dione)
AcOH = acetic acid
Ala = alanine
BCPM = (2S,4S)-N-(t-butoxycarbonyl)-2-[(diphenylphosphino)methyl]-
4-(dicyclohexyl phosphino)pyrrolidine
BCPP = (2S,4S)-N-(t-butoxycarbonyl)-2-[(dicyclohexylphosphino)methyl]-
4-(diphenylphosphino)pyrrolidine
BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl
BPPM = (2S,4S)-N-(t-butyloxycarbonyl)-4-(diphenylphosphino)-2-
[(diphenylphosphino)methyl)]pyrrolidine
CAMP = cyclohexyl-(o-anisyl)-methylphosphin
COD = cycloocta-1,5-dione
Cn = cinchonine
Cnd = cinchonidine
Cy = cyclohexyl
CyCAPP = N-(N'-R-carbamoyl)-4-dicyclohexylphosphino-2-[(dicyclohexylphosphino)
methyl]pyrrolidine
d = dextrorotatory, (+)
