First heterogeneously palladium catalysed α-arylation of diethyl malonate

Article abstract of DOI:10.1016/S0022-328X(00)00204-7

Pd exchanged NaY zeolites ([Pd(0)]-, [Pd(II)]- and entrapped [Pd(NH₃)₄]) exhibit a good activity towards the α-arylation of carbonyl compounds using different para-substituted aryl bromides. Low Pd-concentrations (only 2 mol%) are required to observe interesting activity. The catalysts can easily be separated from the reaction mixture and reused without any loss in activity. For large-scale applications the alternative use of an insoluble base as K₂CO₃ seems to be promising. The electronic nature of the aryl halides plays a limited role concerning the rate of the reaction.

Full text of DOI:10.1016/S0022-328X(00)00204-7

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 606 (2000) 101–107
First heterogeneously palladium catalysed a-arylation of diethyl
malonate
Laurent Djakovitch *, Klaus Ko¨hler
Technische Uni6ersita¨t Mu¨nchen, Anorganisch-Chemisches Institut, Lichtenbergstrasse 4, D-85748 Garching b. Munchen, Germany
Received 3 February 2000; received in revised form 29 March 2000
Abstract
Pd exchanged NaY zeolites ([Pd(0)]–, [Pd(II)]– and entrapped [Pd(NH3)4]) exhibit a good activity towards the a-arylation of
carbonyl compounds using different para-substituted aryl bromides. Low Pd-concentrations (only 2 mol%) are required to observe
interesting activity. The catalysts can easily be separated from the reaction mixture and reused without any loss in activity. For
large-scale applications the alternative use of an insoluble base as K2CO3 seems to be promising. The electronic nature of the aryl
halides plays a limited role concerning the rate of the reaction. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Heterogeneous catalytic a-arylation; Carbonyl derivatives; Zeolite supported palladium; Aryl halides
We have previously shown that Pd supported in
zeolites (Pd(0)-, Pd(II)- and Pd-complexes) are efficient
1. Introduction
heterogeneous catalysts for C–C coupling reactions
between aryl halides and alkenes (Heck reaction) [4].
The synthesis of a-aryl carbonyl compounds has
received much attention during the last decades [1].
More recently we reported, for the first time, the het-
Numerous stoichiometric arylating reagents have been
erogeneously Pd-catalysed direct synthesis of aryl
developed, but their interest remains limited since the
amines from aryl halides [5]. Due to the similarities
production of each a-aryl carbonyl compound required
the preparation of different reagents [2]. Recently, in
order to overcome this situation, the homogeneous
Pd-catalysed arylation of ketones has been developed,
between these reactions with the reaction considered
here [6], we decided to investigate the potential of
Pd-loaded zeolites as heterogeneous catalysts for the
a-arylation of carbonyl compounds.
leading thus to a useful direct synthesis [3]. To our
We describe that Pd-loaded zeolites are active and
knowledge no reports concerning the use heterogeneous
selective heterogeneous catalysts for the direct arylation
catalysts have appeared up to now.
of carbonyl derivatives via an enolate.
While the use of homogeneous catalysts constitutes
today an inestimable choice (high activity and selectiv-
ity, good comprehension of the reaction paths), these
catalysts are connected with problems of separation,
recovery and regeneration. For industrial applications
these difficulties are of economic importance (costs of
the catalysts and of the purification process). Such
problems could be principally minimised by the use of
heterogeneous catalysts.
2. Results and discussion
2.1. Preparation of the catalysts
[Pd(NH3)4]2+ –, Pd(II)– and the Pd(0)–NaY zeolites
were prepared according to the literature by an ion
exchange procedure [7]. Using an aqueous solution of
[Pd(NH3)4]Cl2, a 1 wt% [Pd(NH3)4]-zeolite was ob-
tained. Calcination under O2 of exchanged
[Pd(NH3)4]2+ –NaY gave the Pd(II)–NaY zeolite and
subsequent reduction under H2 lead to the formation of
the Pd(0)–NaY zeolite (see Section 4).
* Corresponding author. Tel.: +49-89-2891 3074; fax: +49-89-
2891 3473.
E-mail address: laurent.djakovitch@ch.tum.de (L. Djakovitch).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00204-7

102
L. Djako6itch, K. Ko¨hler / Journal of Organometallic Chemistry 606 (2000) 101–107
Analogously, the [Pd(OAc)2] loaded zeolite was pre-
pared by immobilisation of the complex in the zeolite.
Since the diameter of the zeolite channels is limited (for
reaction products due to a mixture of regio-isomers. As
was already mentioned in the literature [3d], results thus
obtained can be extended to a larger family of carbonyl
derivatives.
,
the Y zeolite: ¥=7.4 A) [8], molecular modelling
calculations were performed in order to check whether
the complexes can pass through the zeolite window.
The results obtained using the MM2 augmented
parameters provided with the CACHE™ software from
Oxford Molecular Ltd were reported elsewhere [4b].
Experimentally, we found that a 0.7 wt% [Pd(OAc)2]–
NaY zeolite was obtained after an exchange period of 3
days from a THF solution. This catalyst was then
characterised by MAS-NMR, which has shown that the
Pd(OAc)2 complex immobilised into the zeolite su-
percage was intact and gave compatible 1H and 13C
spectra with the solution NMR spectrum of the free
Pd-complex [4b].
The choice of aryl bromides for the test of the
catalytic activity was directed both by the real availabil-
ity of these compounds and on the basis of the litera-
ture. Aryl bromides exist with a large variety of
substituents on the aromatic ring, which can be used to
test the tolerance of the reaction towards different
functional groups. The variety of derivatives used rep-
resents a good basis for comparison of the heteroge-
neously (this paper) and the homogeneously catalysed
arylation of carbonyl derivatives.
According to the literature, the Pd-catalysed aryla-
tion of carbonyl compounds can be described as a C–C
coupling reaction between an aryl halide and an enolate
(Scheme 2), which is produced in situ in presence of a
base [3a].
2.2. Tests of the catalytic acti6ity
One focus of our investigations of the new heteroge-
neously catalysed reaction, concerns the comparisons
between homogeneous and heterogeneous systems. In
order to obtain comparable data, we decided to run
parallel experiments using as a ‘standard’ homogeneous
As a model reaction we chose the arylation of the
diethyl malonate (EtO2CCH2CO2Et) using aryl bro-
mides (Scheme 1). Since this carbonyl derivative is
symmetric, it limits the difficulties in the analysis of the
Scheme 1. Pd-catalysed a-arylation of diethylmalonate. Reaction conditions: 15 mmol aryl bromide, 10 mmol diethyl malonate, 20 mmol of base,
2 mol% [Pd]-catalyst, 6 ml solvent, 110°C, 20 h.
Scheme 2. Proposed reaction pathway for the Pd-catalysed a-arylation of carbonyl derivatives (M=Na, K, Li).

L. Djako6itch, K. Ko¨hler / Journal of Organometallic Chemistry 606 (2000) 101–107
103
Table 1
species that are created during the reaction, since the
thermal treatments made for the preparation of the
Pd(II)– and the Pd(0)–NaY catalysts tend to reduce
the effective dispersion of the Pd-centres by an aggrega-
tion process.
The lower activity observed for the [Pd(OAc)2]–NaY
compared to the Pd(II)– or the [Pd(NH3)4]–NaY cata-
lyst can be explained in terms of a reduced diffusion of
the educts and/or the product into the zeolite channels
due to the larger size of the Pd-complex compared to
the other immobilised Pd-species. Alternatively, it could
be the difficulty to create Pd-active species at the reac-
tion temperature (110°C) as was described elsewhere
[4b].
Results obtained for the arylation of diethyl malonate with para-bro-
motoluene (Scheme 1, R=CH3) using 1 mol% Pd-catalyst as differ-
ent [Pd]–NaY zeolite or as
a standard homogeneous catalyst
[Pd(OAc)2/PPh3 (four equivalents)] in presence of NaOtBu in THF a
Entry Catalyst
GLC yield
Isolated yield
1
2
3
4
5
Pd(0)–NaY
Pd(II)–NaY
[Pd(NH3)4]–NaY
[Pd(OAc)2]–NaY
31
41
51
41
21
32
38
29
56
[Pd(OAc)2]/PPh3 (four 65
equivalents)
a The GLC yields (Drel5910%) and the isolated yields are given
with regard to the diethyl malonate (carbonyl compound).
In addition to these experiments, we investigated
whether the presence of Pd-species in zeolites was re-
sponsible for the activity. Thus, running an experiment
in the presence of naked zeolite (Pd-free NaY) the
formation of products resulting from the arylation of
the diethyl malonate was never observed and in some
cases degradation products (black mass) were obtained.
One should note that at the end of the reaction the
remaining aryl bromide does not compensate the quan-
titative analysis (with regard to the starting para-bromo
toluene) and that as side products of the reaction
biphenyl derivatives were observed (typically 10–15%
yields).
catalyst, the Pd(OAc)2/PPh3 system, although it is not
known as the most active [3].
In the following we will describe and discuss the
results obtained with respect to: the nature of the
Pd-species immobilised into the NaY zeolite; the nature
of the para-aryl substituent; the variation of the base
and the solvent; and the recovery of the catalysts.
2.3. Influence of the nature of the Pd-species entrapped
into the NaY zeolite
It has been previously described that the activity of
the Pd-loaded zeolites used for C–C coupling reactions
between aryl bromides and olefins was strongly depen-
dent on the nature of the Pd-species entrapped in the
cages at the beginning of the reaction [4,5]. Thus, a
relation between the activity of the catalysts and the
nature of the Pd-species was observed in terms of
variation in Pd-dispersion attained during the prepara-
tion of the catalysts and in terms of different active
Pd-species generated before and during the reaction [4].
Analogous to these works, we were interested to study
such influence for the arylation of carbonyl
compounds.
For these investigations we chose the reaction of
diethyl malonate with the para-bromo toluene as ary-
lating agent in presence of NaOtBu as base (Scheme 1,
R=CH3, Base=NaOtBu in THF).
Table 1 shows that the homogeneous catalyst is
slightly more active than the heterogeneous catalysts
used in this study. That can be a direct consequence of
the reduced diffusion of the educts and products to and
from the catalytic centres using zeolites as a support for
heterogeneous catalysts.
2.4. Influence of the para-aryl substituent
As for many organic reactions, it was interesting to
study the generalisation of the heterogeneously Pd-
catalysed arylation of carbonyl compounds, i.e. its tol-
erance towards a variety of functional groups. Thus, we
studied the reaction between differently para-substi-
tuted aryl bromides and the diethyl malonate in the
presence of NaOtBu as base in THF (Scheme 1).
The results reported in Table 2 show that the para-
aryl substituent has a ‘limited’ effect on the reaction
yield. As expected from the reaction mechanism pro-
posed in Scheme 2, the limiting steps of the reaction
should be (1) the oxidative addition of the arylating
agent to the Pd(0)-centre, in which the nature of the
para-aryl substituent plays a role and (2) the reductive
elimination of the product in which, as already re-
ported, the ligands present on the Pd(0)-centre are
important. In the heterogeneous systems used in this
study, the second limiting step can not be minimised.
As for other Pd-catalysed C–C coupling reactions, the
electronic nature of the aryl halide is crucial. Better
results are obtained when the aryl halide presents in
para-position an electron-withdrawing group (easiest
oxidative addition). At this date, we could not explain
the high yield obtained when the para-nitro bromoben-
zene is used as arylating agent since it could not be
rationalised only in term of electronic effects. A possi-
As was previously described, the nature of the Pd-
species entrapped into the zeolite at the beginning of
the reaction has an influence onto the activity of the
catalyst. Thus, as already observed, the [Pd(NH3)4]–
NaY zeolite presents the highest activity [4b]. This can
be correlated to a higher dispersion of the Pd-active

104
L. Djako6itch, K. Ko¨hler / Journal of Organometallic Chemistry 606 (2000) 101–107
Table 2
Results obtained for the arylation of diethyl malonate with different para-substituted aryl bromides using 1 mol% {[Pd(NH3)4]–NaY} as catalyst,
or for the homogeneous runs, the system [Pd(OAc)2]/PPh3 (four equivalents)] in the presence of NaOtBu in THF (Scheme 1) a
Entry
R
Yield for heterogeneous catalyst
Yield for homogeneous catalyst
1
2
3
4
5
6
OCH3
CH3
H
57 (45)
51 (38)
47 (41)
64 (50)
70 (62)
98 (84)
62 (48)
65 (56)
58 (50)
72 (60)
71 (64)
96 (78)
F
CH3CO
NO2
a The GLC yields (Drel5910%) and the isolated yields (in parenthesis) are given with regard to the diethyl malonate (carbonyl compound).
Table 3
Results obtained for the arylation of diethyl malonate with para-bromotoluene (Scheme 1, R=CH3) using 1 mol% Pd-catalyst as [Pd]–NaY
zeolite or [Pd(OAc)2/PPh3 (four equivalents)] in the presence of different bases in a given solvent a
Entry
Base
Solvent
GLC yield for heterogenous catalyst
GLC yield for homogeneous catalyst
1
2
3
4
5
6
NaOtBu
NaOtBu
KotBu
KotBu
K2CO3
K2CO3
THF
DMF
THF
DMF
THF
DMF
41
45
39
46
6
65
67
40
60
8
24
32
a The GLC yields (Drel5910%) and the isolated yields are given with regard to the diethyl malonate (carbonyl compound).
ble explanation is that this compound, due to its
highest polarity and its strong dipole moment, diffuses
better into the zeolite.
2.6. Reco6ery of the catalysts
An important point concerning the use of an hetero-
geneous catalyst is its lifetime, particularly for indus-
trial applications.
2.5. Influence of the base and the sol6ent
After separation and washing, the heterogeneous cat-
alysts were used for the same reactions (Scheme 1)
under the same reaction conditions as for the initial run
without any regeneration procedure. Table 4 shows that
all the catalysts still showed a comparable activity as
for fresh catalysts.
In addition to these experiments selected investiga-
tions concerning the leaching (residual activity of the
supernatant solution after separation of the solid) were
As suggested by the reaction pathway (Scheme 2), the
nature of the base could influence the formation of the
intermediate enolate and thus influence the overall ac-
tivity observed for the reaction. Thus, we were inter-
ested in a study concerning the effect of the base in a
given solvent medium.
Table 3 shows that using a ‘soluble base’ as Na– or
K–OtBu in THF or DMF at 110°C only a little effect
is observed. On the contrary, when the base is not
soluble in the medium (as K2CO3 in THF), no or little
product was formed. This could be partially minimised
by using a more convenient medium such as DMF.
This promising result could be enhanced by increasing
the reaction temperature to 130°C, for which a reaction
yield of 34.7% using the [Pd(NH3)4]–NaY was
obtained.
These results are promising for industrial applica-
tions of this reaction, since the low solubility of the
K2CO3 in DMF at standard temperature allows its
separation easily from the reaction mixture together
with the catalyst. Unfortunately, the increase of the
reaction temperature to 140°C results only in the for-
mation of undefined products (black mass) with a
dramatic decrease of the reaction yields.
Table 4
Results obtained for the arylation of diethyl malonate with para-bro-
motoluene (Scheme 1, R=CH3) using recovered [Pd]–NaY catalysts
in presence of NaOtBu in THF a
Entry
Catalyst
GLC yield
first run
GLC yield
second run
1
2
3
4
Pd(0)–NaY
Pd(II)–NaY
[Pd(NH3)4]–NaY
[Pd(OAc)2]–NaY
31
41
51
41
33
38
49
39
a The GLC yields (Drel5910%) are given with regard to diethyl
malonate (carbonyl compound).

L. Djako6itch, K. Ko¨hler / Journal of Organometallic Chemistry 606 (2000) 101–107
105
made. Using a specific filtration procedure (What-
man+nitrate-cellulose filters) for the separation of the
solid catalyst, no activity at all was observed for most
supernatant solutions. In the case of Pd(0)–NaY zeo-
lites, a limited ‘leaching’ could be observed, but it can
by far not explain the overall activity of the catalysts
(see also recovery of the catalyst).
advantages of the homogeneous catalysts with the ad-
vantages of the heterogeneous ones.
4. Experimental
All preparations, manipulations and reactions were
carried out under argon, including the transfer of the
catalysts to the reaction vessel. All glassware was base-
and acid-washed and oven dried. The other chemicals
(organic reagents) were deaerated by an argon flow
before they were used. The THF used for the catalytic
experiments was distilled under argon over sodium
from purple benzophenone ketyl and stored over acti-
3. Conclusion
The heterogeneous [Pd]–NaY zeolite catalysts pre-
sented in this contribution show a good activity to-
wards the arylation of diethyl malonate using
differently para-substituted aryl bromides. While they
do not rival with the best homogeneous catalysts devel-
oped recently principally by Hartwig et al. [3b,d,h] and
Buchwald et al. [3a,e], they gave an alternative to the
use of homogeneous catalysts for industrial applica-
tions where the cost of the catalysts are of importance.
Remarkable is the comparatively low Pd-concentration
(only 2 mol%) required to observe a reasonable activity.
In addition, these catalysts can be easily separated from
the reaction mixture (filtration) and reused without loss
of activity.
As for other Pd-catalysed C–C coupling reactions,
we found that the electronic effect of the aryl halide
plays a role. Better results are observed when the
arylating agent wear an electron-withdrawing group in
the para-position. However, this effect was found to be
limited since one of the limiting steps of the reaction is
the reductive elimination of the product from the active
Pd-centre.
In some cases, it was reported that the reaction tends
to form some bis-arylated compounds. We never ob-
served such derivatives using [Pd]–NaY catalysts, pos-
sibly due to the well-established ‘shape-selectivity’.
However, in some cases we observed secondary prod-
ucts for the reaction, mainly some biphenyl derivatives.
Using an alternative base (K2CO3), promising results
were obtained. Since one of the motivations for using
heterogeneous catalysts instead of homogeneous ana-
logues is the easier separation procedure, the use of the
badly soluble K2CO3 as the base tends to achieve this
objective. However, the results presented in this paper
should be confirmed, and particularly the activity of the
[Pd]–NaY/K2CO3/DMF (or an alternative solvent) sys-
tem has to be enhanced.
Current investigations focus on the kinetic, the mech-
anism of the heterogeneously catalysed arylation of
carbonyl compounds and the extension of this reaction
to other industrially interesting substrates. New hetero-
geneous systems based on zeolites, carbon and metal
oxide supports are under development. Thus, the graft-
ing of Pd-complexes onto a surface or in a zeolite cages
seems a to be a promising approach for combining the
,
vated molecular sieves (4 A) and the DMF (stored
under nitrogen) was purchased from Sigma–Aldrich
Chemicals as a Sure-Sealed Bottle. The NaY zeolite
(LZ-Z-52) was purchased from Sigma–Aldrich Chemi-
cals and the PdCl2 used as precursor for the prepara-
tion of the catalyst was donated by Degussa-Huels Ag.
The catalyst support was dried before use at 120°C for
48 h under 5×10−2 mmHg. All other chemicals were
used as received. NMR spectra were recorded with a
Bruker AM 400 spectrometer (1H-NMR were refer-
enced to the residual protio-solvent: CDCl3, l=7.25
ppm; 13C-NMR were referenced to the C-signal of the
deutero solvent: CDCl3, l=77ppm). The palladium
content determination of the catalysts was performed
by AAS from a solution obtained by treatment of the
catalysts with a mixture of HBF4, HNO3 and HCl in a
Teflon reactor at 180°C. Gas-liquid chromatograms
were performed on a HP 6890 series chromatograph
equipped with a FID detector and a HP-1 column
(cross-linked methylsiloxane, 30 m×0.25 mm×0.25
mm film thickness) using He as carrier gas. Alterna-
tively, a HP 5970 series chromatograph equipped with a
selective mass-spectrometer detector HP 5970 and a
BGB-1 column from SCP-Seitz GmbH (95% methyl-
polysiloxane+5% phenylpolysiloxane, 25 m×0.32
mm×0.52 mm) using He as carrier gas was used.
4.1. Preparation of the catalysts
4.1.1. Procedure for the preparation of the
[Pd(NH3)4]–NaY
A 0.1 M ammoniac solution of [Pd(NH3)4]Cl2, pre-
pared from PdCl2 and a commercial ammoniac solution
(0.95 ml g−1 zeolite, corresponding approximately to
1% Pd in the final catalyst) was added drop wise to a
suspension of the zeolite NaY in bidistilled water (100
ml g−1 zeolite). The mixture was stirred for 24 h at
room temperature (r.t.) and the exchanged zeolite was
filtered off and washed until no trace of chloride was
detected in the filtrate (AgNO3 test). Then the zeolite
was allowed to dry at r.t. to give the entrapped
[Pd(NH3)4]2+ zeolite as a slightly yellow material. The
AAS gave 1.090.2 wt% Pd.

106
L. Djako6itch, K. Ko¨hler / Journal of Organometallic Chemistry 606 (2000) 101–107
4.1.2. Procedure for the preparation of the
[Pd(II)]–NaY
in a pressure tube under argon. A total of 6 ml of dry
solvent previously deaerated was added and the mixture
was further deaerated by an argon flow for 5 min. The
reactor was then placed in a pre-heated oil bath at
110°C for 20 h with vigorous stirring and then cooled
to r.t. before the reaction mixture was analysed by
GLC.
For the recycling studies, a catalyst issue from a first
run was used. After separation of the reaction mixture,
it was washed with toluene and CH2Cl2 in order to
remove all adsorbed organic substrates and dried at r.t.
The Pd(II) exchanged zeolite was obtained by calci-
nation of the [Pd(NH3)4]–NaY in a U-tube reactor
under a pure oxygen flow (180 ml min−1) using a
heating rate of 2 K min−1 from r.t. to 500°C. The
temperature was maintained at 500°C for 30 min and
the reactor was cooled to r.t. under a flow of argon to
give the Pd(II) zeolite as a tabac-coloured powder. The
AAS gave 1.090.2 wt% Pd.
4.1.3. Procedure for the preparation of the
[Pd(II)]–NaY
4.3. GLC analysis
The Pd(0) exchanged zeolite was obtained by reduc-
tion of the [Pd(II)]–NaY in a U-tube reactor under a
pure hydrogen flow (70 ml min−1) using a heating rate
of 8 K min−1 from r.t. to 350°C. The temperature was
maintained at 350°C for 15 min and the reactor was
cooled to r.t. under a flow of argon to give the Pd(0)
zeolite as a black powder. The AAS gave 1.090.2 wt%
Pd.
A homogeneous 3-ml sample of the reaction mixture
was sampled and quenched with 5 ml of water in a test
tube. A total of 3 ml of CH2Cl2 was added and the
layers were shortly but vigorously mixed before the
organic layer was separated. It was dried over MgSO4
and filtered through a cotton pad. The resulting dry
organic layer was then analysed by GLC or GLC-MS.
GLC-rate program: AS 100 constant-pressure (130
KPa): 2 min at 100°C, heating at 15°C min−1 up to
170°C, 2 min at 170°C, heating at 35°C min−1 up to
240°C, 10 min at 240°C, heating at 50°C min−1 up to
270°C and 2 min at 270°C.
4.1.4. Procedure for the preparation of the
[Pd(OAc)2]–NaY
A solution of the Pd(OAc)2 (110.2 mg, 0.47 mmol,
corresponding approximately to 1% Pd in the final
catalyst) in THF was added drop wise to a suspension
of the zeolite NaY (4.95 g) in THF (20 ml g−1 zeolite).
The mixture was stirred for 3 days at r.t. and the
[Pd(OAc)2] loaded zeolite was filtered off and washed
with THF until no trace of non-immobilised complex
was detected in the filtrate. Then the zeolite was al-
lowed to dry at r.t. to give the entrapped [Pd(OAc)2]
zeolite as a slightly brown material. The AAS gave
4.4. Purification of the malonate deri6ati6es
When possible, the products of the arylation reac-
tions were isolated and analysed by standard methods
(1H- and 13C-NMR). We give here the purification
methods used, followed by the characterisation data.
After separation of the heterogeneous catalyst, the
reaction mixture was evaporated. The residue was dis-
solved in CH2Cl2 (50 ml) and washed with water (3×
20 ml). The organic layer was then dried over activated
MgSO4 and evaporated. The residue was then purified
by chromatography over silica gel (50 g SiO2 g−1
organic mixture, SiO2 Merck Type 7754 70-230 mesh,
0.790.2 wt% Pd.
1
MAS-NMR: H-NMR, ppm: 2.10 (CH3
6
CO).
MAS-NMR: 13C-NMR, ppm: 186,84 (CH3C
23.04 (CH3CO).
6 O);
6
4.2. Test of the catalytic acti6ity
,
60 A) eluting with CH2Cl2 to give the malonate deriva-
tive. Additional chromatography on silica was realised
in order to obtain a higher purity. The purity of the
products was estimated by GLC to be ]90%.
Catalytic reactions were carried out in pressure tubes
under argon. The Pd-catalysts were transferred under
Ar. The qualitative and quantitative analyses of the
reactants and the products were made by GLC. Con-
version and selectivity are represented by GLC yields
(=relative area of GLC signals referred to an internal
standard calibrated to the corresponding pure com-
pound, Drel= 910%).
4.5. Characterisation of the malonate deri6ati6es
4.5.1. Data for the 2-Phenyl-malonic acid diethyl ester
(R=H), colourless oil
3
1H-NMR, CDCl3, 400.13 MHz: 7.39 (pseudo-d, J=
6.7 Hz, 2H, m-C6H5
C6H5); 4.64 (s, 1H, CH
OCH2
13C-NMR, CDCl3, 100.62 MHz: 168.80 (CꢀO);
133.76 (ipso-C6H5–CH); 130.05 (o-C6H5–CH); 129.27
(m-C6H5–CH); 128.88 (p-C6H5–CH); 62.38
(CH2OCO); 58.64 (CH); 14.67 (CH3CH2O).
6
); 7.29 (m, 3H, o-C6H5
6
and p-
4.2.1. General procedure for the first run and the
recycling of the catalysts
A total of 15 mmol of aryl bromide, 10 mmol of
diethyl malonate, 20 mmol of base and 2 mol% of Pd
(as heterogeneous catalyst, the amount in grams of
catalyst depending on the Pd loading) were introduced
6
6
3
); 4.15 (q, 4H, 3J=8.0 Hz,
6
CH3); 1.19 (t, 6H, J=8.0 Hz, OCH2CH6 3).
6
6
6
6
6
6
6

L. Djako6itch, K. Ko¨hler / Journal of Organometallic Chemistry 606 (2000) 101–107
107
4.5.2. Data for the 2-p-tolyl-malonic acid diethyl ester
13C-NMR, CDCl3, 100.62 MHz: 196.58 (C
172.24 (CꢀO); 139.58 (ipso-C6
CH); 130.02 (o-C6H4–CH); 129.09 (m-C6
61.72 (CH2OCO); 58.42 (CH); 22.76 (CH3CO); 14.08
(CH3CH2O).
6
O–CH3);
(R=CH3), colourless oil
6
H4-CH); 136.39 (p-C6
6 H4–
1H-NMR, CDCl3, 400.13 MHz: 6.94 (br. m, 4H,
6
6
H5–CH);
C6H4
OCH2
8.0 Hz, OCH2CH3
13C-NMR, CDCl3, 100.62 MHz: 169.02 (CꢀO);
136.52 (p-C6H4-CH); 132.21 (ipso-C6H4–CH); 129.86
(o-C6H4–CH); 129.65 (m-C6H4–CH); 61.86
(CH2OCO); 56.72 (CH); 21.6 (CH3C6H4); 14.09
(CH3CH2O).
6
); 4.64 (s, 1H, CH
CH3); 2.32 (s, 3H, C6H4CH3
6
); 4.14 (q, 4H, 3J=8.0 Hz,
6
6
6
3
6
6
); 1.24 (t, 6H, J=
6
6
).
6
6
Acknowledgements
6
6
6
6
6
6
We are grateful to the European Community (Marie-
Curie, TMR programme) for a research grant to L.D.,
the Technische Universita¨t of Mu¨nchen and the Fonds
der Chemischen Industrie (Germany) for support. We
acknowledge Degussa AG (Germany) for the donation
of PdCl2 and catalyst support.
4.5.3. Data for 2-(4-methoxy-phenyl)-malonic acid
diethyl ester (R=CH3O), colourless oil
3
1H-NMR, CDCl3, 400.13 MHz: 6.98 (d, J=7.1 Hz,
3
2H, o-C6H4
(s, 1H, CH
(s, 3H, CH3
13C-NMR, CDCl3, 100.62 MHz: 170.12 (CꢀO);
160.86 (p-C6H4–CH); 132.21 (ipso-C6H4–CH); 129.86
(o-C6H4–CH); 117.76 (m-C6H5–CH);
(CH2OCO); 56.86 (CH); 55.29 (C
(CH3CH2O).
6
); 6.69 (d, J=7.1 Hz, 2H, m-C6H4
6
); 4.59
CH3); 3.76
3
6
); 4.36 (q, 4H, J=8.0 Hz, OCH2
6
3
6
O); 1.30 (t, 6H, J=8.0 Hz, OCH2CH6 3).
References
[1] R.A. Abramovitch, D.H.R. Barton, J.-P. Finet, Tetrahedron 44
(1988) 3039.
6
6
6
6
62.08
[2] (a) J. Morgan, J.T. Pinhey, B.A. Rowe, J. Chem. Soc. Perkin
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M.E. Browne, J. Org. Chem. 53 (1988) 4149 .(j) M.W. Rathke, D.
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242.
6
6
6
6
H3O); 14.11
4.5.4. Data for 2-(4-fluoro-phenyl)-malonic acid diethyl
ester (R=F), colourless oil
3
1H-NMR, CDCl3, 400.13 MHz: 7.04 (d, J=8.0 Hz,
3
2H, o-C6H4
6
); 6.89 (d, J=8.0 Hz, 2H, m-C6H4
6
); 4.51
3
(s, 1H, CH
6
); 4.21 (q, 4H, J=8.0 Hz, OCH2
(t, 6H, J=8.0 Hz, OCH2CH3).
13C-NMR, CDCl3, 100.62 MHz: 171.24 (CꢀO);
160.92 (p-C6H4–CH); 132.52 (o-C6H4–CH); 131.63
(ipso-C6H4–CH); 116.29 (m-C6H5–CH); 61.28
(CH2OCO); 57.92 (CH); 14.08 (CH3CH2O).
6
CH3); 1.29
3
6
6
6
6
6
6
6
6
[3] (a) M. Palucki, S.L. Buchwald, J. Am. Chem. Soc. 119 (1997)
11 108. (b) B.C. Hamman, J.F. Hartwig, J. Am. Chem. Soc. 119
(1997) 12 382. (c) T. Satoh, Y. Kawamura, M. Miura, M.
Nomura, Angew. Chem. Int. Ed. Engl. 36 (1997) 1740. (d) K.H.
Shaughnessy, B.C. Hamman, J.F. Hartwig, J. Org. Chem. 63
4.5.5. Data for 2-(4-nitro-phenyl)-malonic acid diethyl
ester (R=NO2), yellow 6iscous oil
3
1H-NMR, CDCl3, 400.13 MHz: 8.15 (d, J=9.0 Hz,
3
,
(1998) 6546. (e) J. Ahman, J.P. Wolfe, M.V. Troutman, M.
2H, o-C6H4
6
); 7.41 (d, J=9.0 Hz, 2H, m-C6H4
6
); 4.58
Palucki, S.L. Buchwald, J. Am. Chem. Soc. 120 (1998) 1918. (f)
Y. Kawamura, T. Satoh, M. Miura, M. Nomura, Chem. Lett.
(1999) 961. (g) T. Satoh, Y. Kametani, Y. Terao, M. Miura, M.
Nomura, Tetrahedron Lett. 40 (1999) 5345. (h) M. Kawatsura,
J.F. Hartwig, J. Am. Chem. Soc. 121 (1999) 1473.
3
(s, 1H, CH
6
); 4.25 (q, 4H, J=8.0 Hz, OCH2
(t, 6H, J=8.0 Hz, OCH2CH3).
13C-NMR, CDCl3, 100.62 MHz: 172.04 (CꢀO);
147.22 (p-C6H4–CH); 141.23 (ipso-C6H4–CH); 130.82
(o-C6H4–CH); 124.19 (m-C6H5–CH); 61.68
(CH2OCO); 58.22 (CH); 14.18 (CH3CH2O).
6
CH3); 1.32
3
6
6
6
[4] (a) L. Djakovitch, K. Ko¨hler, J. Mol. Catal. A: Chem. 142 (1999)
275. (b) L. Djakovitch, H. Heise, K. Ko¨hler, J. Organomet.
Chem. 584 (1999) 16.
6
6
6
6
6
[5] L. Djakovitch, K. Ko¨hler, J. Organomet. Chem. 592 (1999) 225.
[6] F.G. Bordwell, Acc. Chem. Res. 21 (1988) 456.
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4553. (b) W.M.H. Sachtler, F.A.P. Cavalcanti, Catal. Lett. 9
(1991) 261.
[8] Structures of the zeolite Y were obtained from: W.M. Meier,
D.H. Olson, Ch. Baerlocher (Eds.) The Atlas of Zeolite Structure
Type, Elsevier, Amsterdam, 1996, p. 104.
4.5.6. Data for 2-(4-acetyl-phenyl)-malonic acid diethyl
ester (R=CH3CO), pale yellow 6iscous oil
3
1H-NMR, CDCl3, 400.13 MHz: 7.72 (d, J=8.1 Hz,
3
2H, m-C6H4
(s, 1H, CH
(s, 3H, CH3
6
); 7.17 (d, J=8.1 Hz, 2H, o-C6H4
6
); 4.61
3
6
); 4.28 (q, 4H, J=8.0 Hz, OCH2
6
CH3); 2.58
3
6
CO); 1.28 (t, 6H, J=8.0 Hz, OCH2CH6 3).
.