Nanocrystalline magnesium oxide-stabilized palladium(0): An efficient and reusable catalyst for Suzuki and stille cross-coupling of aryl halides

Article abstract of DOI:10.1002/adsc.200505198

A nanocrystalline magnesium oxide-stabilized palladium(0) catalyst is prepared by counterion stabilization of PdCl₄^2- with nanocrystalline MgO followed by reduction. This ligand-free heterogeneous nanocrystalline MgO-stabilized nanopalladium [NAP-Mg-Pd(0)] catalyst using the basic MgO in place of basic ligands exhibits excellent activity in Suzuki and Stille cross-coupling of haloarenes (chloro, bromo and iodo) to afford the unsymmetrical biaryls. The catalyst is quantitatively recovered by simple filtration and reused for four cycles with almost consistent activity.

Full text of DOI:10.1002/adsc.200505198

FULL PAPERS
DOI: 10.1002/adsc.200505198
Nanocrystalline Magnesium Oxide-Stabilized Palladium(0):
An Efficient and Reusable Catalyst for Suzuki and Stille
Cross-Coupling of Aryl Halides
M. Lakshmi Kantam,a,* Sarabindu Roy,a Moumita Roy,a B. Sreedhar,a
B. M. Choudaryb,*
a
Indian Institute of Chemical Technology, Hyderabad 500007, India
Fax: (þ91)-40-27160921, e-mail: lkmannepalli@yahoo.com, mlakshmi@iict.res.in
b
Ogene Systems(I) Pvt. Ltd, Hyderabad, 500 037, India, e-mail: bmchoudary@yahoo.com
Received: May 16, 2005; Accepted: September 19, 2005
Abstract: A nanocrystalline magnesium oxide-stabi- bromo and iodo) to afford the unsymmetrical biaryls.
lized palladium(0) catalyst is prepared by counterion The catalyst is quantitatively recovered by simple fil-
2ꢀ
stabilization of PdCl4 with nanocrystalline MgO fol- tration and reused for four cycles with almost consis-
lowed by reduction. This ligand-free heterogeneous tent activity.
nanocrystalline
[NAP Mg Pd(0)] catalyst using the basic MgO in
place of basic ligands exhibits excellent activity in Su- Keywords: nanocrystalline magnesium oxide; palladi-
MgO-stabilized
nanopalladium
ꢀ
ꢀ
zuki and Stille cross-coupling of haloarenes (chloro, um(0); Stille cross-coupling; Suzuki cross-coupling
Introduction
nanostructured MgO materials to possess a high concen-
tration of reactive surface ions. The reactive sites on the
Thepalladium-catalyzedSuzukiandStillecross-coupling surface of MgO are as follows:[5] 1) Mg2þ site, which is
reactions represent two very well established methodol- of the Lewis acid type, 2) O2ꢀ site which is of the Lewis
ogies[1,2] inmodern organic synthesis tomake C C bonds. basetype, 3)latticeboundand4)isolatedhydroxygroups
ꢀ
Most of the catalytic systems, mainly the combination of and anionic and cationic vacancies. An edge or even
palladium salts with various phosphine ligands or N-het- more so, a corner O2ꢀ anion is coordinatively unsaturat-
erocyclic carbene ligands, result in excellent yields with ed and is seeking Lewis acids to help stabilize and deloc-
high efficiency. Despite the synthetic elegance and high alize its negative charge. Conversely, an Mg2þ ion on an
turnover numbers, the non-reusability of the precious edge or corner is seeking Lewis bases to stabilize and de-
palladium precludes wide synthetic applications in the localize its positive charge. Therefore, these coordina-
pharmaceutical industry. In view of the above, it is desir- tively unsaturated O2ꢀ and Mg2þ ions readily accept in-
able to develop a ligand-free[3] and reusable catalytic sys- coming reagents with Lewis acid or Lewis base character.
tem to dispense with the use of expensive and air-sensi- HereinwereporttheSuzukiandStillecross-couplingofa
tive ligands. Earlier, we reported the effective Heck-, Su- broad range of aryl halides with arylboronic acids and
zuki-, Sonogashira-, and Stille-type coupling reactions of phenyltributyltin, respectively, in moderate to excellent
chloroarenes using Mg-Al layer hydroxides-supported yields using the ligand-free nanocrystalline MgO-stabi-
nanopalladium catalyst.[3d] In an effort to develop a new lized palladium(0) catalyst.
heterogeneous system, we turned our attention towards
the exploration of highly basic nanocrystalline magnesi-
ꢀ
umoxide (NAP MgO)assupport. Recentlywereported Results and Discussion
the enhanced activity of NAP MgO[4] stabilized osmate,
ꢀ
palladate, and tungstate systems in tandem dihydroxyla-
Preparation of Nanocrystalline MgO-Stabilized Pd(0)
Catalyst
tion of alkenes, Heck vinylation, and N-oxidation over
their homogeneous counterparts. Due to the high surface
areaandbasicity of the nanocrystallinemagnesium oxide
support, these catalysts exhibit high activity. The pres- The peculiar characteristics of the nanomaterials pres-
ence of edge-corner and other defect sites allows the ent an opportunity to prepare new and unusual materi-
2002
ꢀ 2005 Wiley-VCHVerlag GmbH& Co. KGaA, Weinheim
Adv. Synth. Catal. 2005, 347, 2002 – 2008

Reusable Catalyst for Suzuki and Stille Cross-Coupling of Aryl Halides
FULL PAPERS
Scheme 1. Preparation of nanocrystalline MgO-stabilized
palladium catalyst.
ꢀ
Figure 1. FTIR
NAP Mg PdCl4, and c) NAP Mg Pd(0).
spectra
of
ꢀ
a)
NAP MgO,
b)
ꢀ
ꢀ
ꢀ
als, wherein the highly reactive ions could be stabilized
by forming adducts with the reactive-accepting surface
sites on the MgO. In an effort to obtain counterionic sta-
bilization of PdCl4 with the Mg2þ of the MgO, com-
2ꢀ
mercially available CM-MgO [surface area (SA)
30 m2/g)], and aerogel prepared nanocrystalline MgO
(NAP MgO) (SA 600 m2/g) were treated with
ꢀ
ꢀ
ꢀ
Na2PdCl4
to
afford
CM Mg PdCl4
and
ꢀ
ꢀ
ꢀ
ꢀ
NAP Mg PdCl4. NAP Mg PdCl4 was further reduced
with excess hydrazine hydrate to produce
ꢀ
ꢀ
ꢀ
NAP Mg Pd(0). In the reaction with NAP MgO,
(SA 600 m2/g) the entire amount of Na2PdCl4 used was
consumed. On the other hand, a small amount
(<0.3%) of palladate was detected in the treated samples
ꢀ
of CM MgO. During the preparation of the catalyst,
which involves the reaction with Na2PdCl4, the Naþ ion
will interact with the Oxꢀ sites/anionic vacancies and
the PdCl42ꢀ will interact with the Mg2þ sites/cationic va-
cancies present on corners or edges of nanocrystalline
MgO to form the catalyst as described in Scheme 1.
ꢀ
ꢀ
ꢀ
ꢀ
Figure 2. XRD of a) NAP Mg Pd(0), b) NAP Mg PdCl4,
and c) NAP MgO.
ꢀ
ꢀ
ꢀ
Characterization of NAP Mg Pd(0)
ꢀ
ꢀ
The NAP Mg Pd(0) catalyst developed was well char-
acterized by FTIR, XRD, XPS, SEM-EDX, TEM and
The X-ray photoelectron spectroscopic (XPS) investi-
ꢀ
ꢀ
UV/Vis-DRS. During the preparation of this catalyst gation of the NAP Mg Pd(0) at the Pd 3d level shows a
the surface of nanocrystalline MgO was hydroxylated 3d5/2 line at 335.02 eV, which clearly indicates that the
as indicated by non-H-bonded OH groups at 3697 cmꢀ1 metal is in the zero oxidation state.[8] The SEM-EDX
in the FTIR spectra (Figure 1).
This is consistent with the reactive profile of NAP
MgO with water.[6] The surface of the nano-MgO is ladium (10.57%) in the sample. The TEM image of the
(scanning electron microscopy-energy dispersive X-ray
analysis) of NAP Mg Pd(0) shows the presence of pal-
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
only hydroxylated to Mg(OH)n, and it takes a longer NAP Mg Pd(0) catalyst shows the average size of the
time and heating to transform the bulk nano-MgO. nanopalladium particles in the range of 30–40 nm.
ꢀ
ꢀ
ꢀ
ꢀ
The XRD of the NAP Mg PdCl4 and NAP Mg Pd(0) The
samples also indicate the formation of Mg(OH)n during NAP Mg Pd(0) was further confirmed by diffuse-re-
complete
reduction
of
palladium
in
ꢀ
ꢀ
preparative protocol (Figure 2).[7]
flectance UV/Vis spectra, in which the peak at 290 nm
Adv. Synth. Catal. 2005, 347, 2002 – 2008
ꢀ 2005 Wiley-VCHVerlag GmbH& Co. KGaA, Weinheim
asc.wiley-vch.de
2003

M. Lakshmi Kantam et al.
FULL PAPERS
2ꢀ
corresponding to PdCl4 disappeared on reduction
(Figure 3).[3d]
Catalytic Suzuki Coupling of Chloroarenes
A variety of chloroarenes reacted in the presence of
ꢀ
ꢀ
3 mol % of NAP Mg Pd(0) catalyst with different aryl-
boronic acids in the presence of a catalytic amount of
tetrabutylammonium bromide (TBAB, 20 mol %) at
1308C in dimethylacetamide (DMA) solvent for 2–6 h
to afford the corresponding cross-coupling product in
moderate to excellent yields. The results are summar-
ized in Table 1.
The presence of electron-withdrawing or electron-do-
nating group in the chloroarene system significantly in-
fluences the reaction rate. The chloroarenes with elec-
tron-withdrawing group gave excellent yields, whereas
Figure 3. Diffuse-reflectance UV/Vis spectra of a)
NAP Mg PdCl4 and b) NAP Mg Pd(0).
2ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
[a]
ꢀ
ꢀ
Table 1. Suzuki coupling reactions of chloroarenes with NAP Mg Pd(0) catalysts.
2004
asc.wiley-vch.de
ꢀ 2005 Wiley-VCHVerlag GmbH& Co. KGaA, Weinheim
Adv. Synth. Catal. 2005, 347, 2002 – 2008

Reusable Catalyst for Suzuki and Stille Cross-Coupling of Aryl Halides
FULL PAPERS
[a]
ꢀ
ꢀ
Table 2. Suzuki coupling of bromo- and iodoarenes with NAP Mg Pd(0) catalysts.
the electron-rich chloroarenes led to moderate yields. NaOHwere found to be of almost equal activity. Here
Conversely, arylboronic acids with electron-donating we performed all the reactions with 0.5 mol % of Pd cat-
groups afforded higher yields than those with electron- alyst but we can also use 0.1 or 0.01 mol % of catalyst
withdrawing groups. The catalyst was reused for four with longer reaction times (Table 2, entry 1).
ꢀ
ꢀ
times (Table 1, entry 1). It was interesting to find out NAP Mg PdCl4 also catalyzed the reaction, but less ef-
ꢀ
ꢀ
ꢀ
ꢀ
that this NAP Mg Pd(0) catalyst can efficiently pro- fectively than NAP Mg Pd(0) (Table 2, entry 1). The
ꢀ
ꢀ
mote the coupling of a variety of iodo- and bromoarenes used NAP Mg PdCl4 catalyst in XPS did not show
with different arylboronic acids at room temperature in any signal for Pd(0) and the reaction after 5 h virtually
aqueous medium with only 0.5 mol % loading without stops without any improvement in yield even on pro-
any additive. The results are summarized in Table 2.
Screening of different solvents for the Suzuki coupling NAP Mg Pd(0)
longed stirring (24 h). These facts suggest that
ꢀ
ꢀ
is
more
active
than
the
ꢀ
ꢀ
of p-Me-C6H4-Br and PhB(OH)2 revealed that water NAP Mg PdCl4 probably due to the presence of nano-
(GC yield: 98%) is an excellent solvent for this reaction palladium particles having higher electron density
although methanol (95%), 2-propanol (97%) and tol- prompted by strong interaction with basic nano-MgO
uene (95%) were also equally effective, but the yields support, which in turn facilitates the oxidative addition
with acetonitrile (20%) and DMF (15%) were poor. of the haloarenes and subsequently enhancing the cou-
Among the different bases screened[9] K2CO3, KF, and pling reaction. The NAP Mg Pd(0) also differs from
ꢀ
ꢀ
Adv. Synth. Catal. 2005, 347, 2002 – 2008
ꢀ 2005 Wiley-VCHVerlag GmbH& Co. KGaA, Weinheim
asc.wiley-vch.de
2005

M. Lakshmi Kantam et al.
FULL PAPERS
ꢀ
ꢀ
Table 3. Stille coupling of haloarenes with NAP Mg Pd(0)
in excellent yields in presence of 1 mol % of the catalyst
(Table 3). However, the coupling of chloroarenes with
phenyltributyltin took a much longer reaction time de-
spite using high catalyst loading (3 mol %). As in the Su-
zuki reactions, chloroarenes bearing electron-withdraw-
ing groups gave greater yields than the chloroarenes
with electron-donating groups (Table 3, entries 6–9).
catalyst.[a]
Heterogeneity and Reusability of the Catalyst
The heterogeneity of the catalyst is also evaluated to
study whether the reaction using solid Pd catalysts oc-
curred on the solid surface[3d, f,g] or were catalyzed by Pd
species in the liquid phase.[10] To address this issue, we
conducted two separate experiments with 4-nitrochloro-
benzene and phenylboronic acid. In the first experiment,
the reaction was terminated after 1 h, and the conversion
was found to be 55%. At this juncture, the catalyst was
separated from the reaction mixture at the reaction tem-
perature and the reaction was continued with the filtrate
for an additional 5 h. In the second experiment, the reac-
tion was terminated after 2 h at 82% conversion and the
catalyst was removed. The reaction was continued with
thefiltrateforanadditional5 h.Inboththecases,thecon-
version remained almost unchanged. Palladium was not
detected in the filtrate in both the experiments by ICP-
AES. These studies demonstrate that the palladium
bound to nanocrystalline MgO during the reaction is
only active and the reaction proceeds on the heterogene-
ous surface. Furthermore, we checked the recyclability of
the catalyst and almost consistent activity was noticed
even after five cycles in all reactions (Table 1, entry 1; Ta-
ble 2, entry 1; Table 3, entries 3, 8).
Conclusion
the classical systems like Pd(OAc)2 and other simple
palladium(II) salts in its easy recovery by simple filtra-
tion and showing consistent activity for five cycles.
Moreover these simple salts,[3h] Pd(OAc)2 and PdCl2 ·
(SEt)2 required 62–96 h for the completion of reaction
(bromoarenes) at room temperature compared to the
Insummary, we used a counterionstabilizationtechnique
for the development of a recoverable and reusable li-
gand-free nanocrystalline MgO-stabilized palladium(0)
catalyst and successfully employed the catalyst in the Su-
zuki and Stille cross-couplings of haloarenes. Moreover,
the catalyst was recovered by simple filtration and reused
for several cycles with almost consistent activity. The sim-
ple procedure, easy recovery and reusable catalytic sys-
tems are expected to contribute to the development of
benign chemical processes and products.
ꢀ
ꢀ
NAP Mg Pd(0) requiring only 5–6 h.
Catalytic Stille Coupling of Haloarenes with
Phenyltributyltin
Impressed with the results for the Suzuki coupling reac-
tion, we further tried to extend the scope of the
NAP Mg Pd(0) catalyst in another important C C
bond forming reaction, namely Stille cross-coupling of
haloarenes with phenyltributyltin.
Experimental Section
ꢀ
ꢀ
ꢀ
General Remarks
FT-IR spectra were recorded on a Perkin-Elmer spectropho-
tometer. 1HNMR spectra were recorded on Bruker
Under our optimized conditions, iodo- and bromoar-
enes afforded the corresponding unsymmetrical biaryls (300 MHz) and Varian Gemini 200 MHz spectrophotometer
2006
asc.wiley-vch.de
ꢀ 2005 Wiley-VCHVerlag GmbH& Co. KGaA, Weinheim
Adv. Synth. Catal. 2005, 347, 2002 – 2008

Reusable Catalyst for Suzuki and Stille Cross-Coupling of Aryl Halides
FULL PAPERS
ꢀ
ꢀ
using CDCl3 as solvent and TMS as the internal standard. XPS
spectra were recorded on a Kratos AXIS 165 with a dual anode
(Mg and Al) apparatus using the Mg Ka anode. X-ray powder
diffraction (XRD) data were collected on a Simens/D-5000 dif-
fractometer using Cu Ka radiation. The particle size and exter-
nal morphology of the samples were observed on a Philips
TECNAI F12 FEI transmission electron microscope (TEM).
SEM-EDX was performed on a Hitachi SEM S-520, EDX-Ox-
ford Link ISIS-300 instrument. Diffuse reflectance UV/Vis
spectra for samples as KBr pellets were recorded on a GBC
Cintra 10e UV-VIS spectrometer in the range 200 to 800 nm
with a scan speed 400 nm per minute. GC analysis was per-
formed using Shimadzu GC-2010 and ZB-5 capillary column.
All known compounds were characterized by comparing their
physical data with those in the literature. Solvents used for ex-
periments were dried and distilled according to literature pro-
cedures. All the reactants were commercially available and
(2 mmol), NAP Mg Pd(0) (0.5 mol %), and water (1 mL)
and stirred at room temperature and reaction was monitored
by TLC. After the completion of the reaction as judged by
TLC, the catalyst was filtered and reused. The filtrate was dilut-
ed with ethyl acetateand washed with 10% aqueous NaOHsol-
ution and finally with saturated aqueous NaCl solution. The or-
ganic layer was dried with Na2SO4 and concentrated to afford
the crude product. The crude reaction mixture was chromato-
graphed on silica gel using hexane/ethyl acetate (10:1) as an
eluent to afford the pure product.
Experimental Procedure for Stille Coupling of
Haloarenes
In an oven-dried, 10-mL, round-bottom flask were charged
haloarene (1 mmol), phenyltributyltin (1.5 mmol), NaOAc
ꢀ
ꢀ
ꢀ
(2 mmol), NAP Mg Pd(0) (1–3 mol %), and NMP (2 mL)
and stirred at 1008C under an N2 atmosphere and reaction
was monitored by TLC. After the completion of the reaction
as judged by TLC, the catalyst was filtered and reused. The fil-
trate was diluted with ethyl acetate and washed with saturated
aqueous NaCl solution. The organic layers were combined and
dried with Na2SO4 and concentrated to get the crude product.
The crude reaction mixture was chromatographed on silica gel
using hexane/ethyl acetate (10:1) as an eluent to afford the
pure product.
used without purification. NAP MgO (commercial name:
NanoActiveTM Magnesium Oxide Plus, Specific surface area
(BET)ꢁ600 m2/g) was purchased from NanoScaleMaterials,
Inc. (Manhattan, USA).
Preparation of Nanocrystalline MgO Stabilized
Palladium Catalyst
2
ꢀ
ꢀ
ꢀ
NAP Mg PdCl4: NAP MgO (BET 600 m /g, 1 g) was treat-
ed with Na2PdCl4 (294 mg, 1 mmol) dissolved in 100 mL decar-
bonated water with stirring for 12 h under a nitrogen atmos-
Acknowledgements
ꢀ
ꢀ
phere to afford the brown colored NAP Mg PdCl4. Then
the catalyst was filtered, and washed with deionized water, ace-
tone, and dried.
S. Roy thanks the Council of Scientific and Industrial Research
(CSIR) India, and M. Roy thanks University Grants Commis-
sion (UGC), New Delhi for the award of a research fellowship.
ꢀ
ꢀ
ꢀ
ꢀ
NAP Mg Pd(0): NAP Mg PdCl4 (1 g) was reduced with
hydrazine hydrate (1 g, 20 mmol) in 20 mL dry ethanol for 3 h
under a nitrogen atmosphere to get the black-colored, air-sta-
ꢀ
ꢀ
ble NAP Mg Pd(0) (Pd 0.99 mmol/g).
References and Notes
[1] Recent papers on Suzuki coupling, see: a) N. Miyaura,
Top. Curr. Chem. 2002, 219, 11; b) J. Hassan, M. Sev-
ignon, C. Gozzi, E. Schulz, M. Lemaire, Chem. Rev.
2002, 102, 1359; c) S. Kotha, K. Lahiri, D. Kashinath, Tet-
rahedron 2002, 58, 9633; d) A. Zapf, R. Jackstell, F. Ra-
taboul, T. Riermeier, A. Monsees, C. Fuhrmann, N.
Shaikh, U. Dingerdissen, M. Beller, Chem. Commun.
2004, 38; e) N. Leadbeater, M. Marco, Angew. Chem.
2003, 115, 1445; Angew. Chem. Int. Ed. 2003, 42, 1407;
f) R. B. Bedford, M. E. Blake, C. P. Craig, D. Holder,
Chem. Commun. 2003, 466; g) R. B. Bedford, C. S. J. Ca-
zin, S. J. Coles, T.Gelbrich, P. N. Horton, M. B. Hurst-
house, M. E. Light, Organometallics 2003, 22, 987;
h) J. P. Stambuli, R. Kuwano, J. F.Hartwig, Angew.
Chem. 2002,114, 940; Angew. Chem. Int. Ed. 2002, 41,
4746; i) A. Zapf, A. Ehrentraut, M. Beller, Angew.
Chem. 2000, 112, 4315; Angew. Chem. Int. Ed. 2000,39,
4153; j) S. D. Walker, T. E. Barder, J. R. Martinelli,
S. L. Buchwald, Angew. Chem. Int. Ed. 2004, 43, 1871.
[2] Recent papers on Stille coupling reaction: see: a) W. Su,
S. Urgaonkar, J. G. Verkade, Org. Lett. 2004, 6, 1421; b) J.
Li, Y. Liang, D. Wang, W. Liu, Y. Xie, D. Yin, J. Org.
Chem. 2005, 70, 2832; c) C. Wolf, R. Lerebours, J. Org.
Experimental Procedure for Suzuki Coupling of
Chloroarenes
In an oven-dried, 10-mL, round-bottom flask were charged
chloroarene (1 mmol), phenylboronic acid (1.5 mmol), K3PO4
ꢀ
ꢀ
(3 mmol), NAP Mg Pd(0) (3 mol %), TBAB (0.2 mmol)
and dimethylacetamide (2 mL) and stirred at 1308C under an
N2 atmosphere and the reaction was monitored by TLC. After
the completion of the reaction as judged by TLC, the catalyst
was filtered and reused. The filtrate was diluted with ethyl ace-
tate and washed with 10% aqueous NaOHsolution and finally
with saturated aqueous NaCl solution. The organic layer was
dried with Na2SO4 and concentrated under reduced pressure.
The crude reaction mixture was chromatographed on silica
gel using hexane/ethyl acetate (10:1) as an eluent to afford
the pure product. NMR and mass spectrometry were used to
identify the purity of the products.
Experimental Procedure for Room Temperature
Suzuki Coupling of Iodo- and Bromoarenes
In an oven-dried, 10-mL, round-bottom flask were charged
aryl halide (1 mmol), phenylboronic acid (1.5 mmol), K2CO3
Adv. Synth. Catal. 2005, 347, 2002 – 2008
ꢀ 2005 Wiley-VCHVerlag GmbH& Co. KGaA, Weinheim
asc.wiley-vch.de
2007

M. Lakshmi Kantam et al.
FULL PAPERS
Chem. 2003, 68, 7551; d) W. Su, S. Urgaonkar, P. A.
McLaughlin, J. G. Verakade, J .Am .Chem. Soc. 2004,
126, 16433.
[6] R. M. Narske, K. J. Klabunde, S. Fultz, Langmuir 2002,
18, 4819.
[7] S. Utamapanya, K. J. Klabunde, J. R. Schlup, Chem. Ma-
ter. 1991, 3, 175.
[8] ESCA of Pd: a) G. Kumar, J. R. Blackburn, R. G. Al-
bridge, W. E. Moddeman, M. M, Jones, Inorg. Chem.
1972, 11, 296; b) K. Kili, L. Hilaire, F. L. Normand,
Phys. Chem. Chem. Phys. 1999, 1, 1623; c) F. B. Verduraz,
A. Omar, J. Escard, B. Pontvianne, J. Catal. 1978, 53, 126.
[3] Recent examples on external ligand free catalytic sys-
tem, see: a) C. R. LeBlond, A. T. Andrews, J. R. Sowa,
Y. Sun, Org. Lett. 2001, 3, 1555; b) M. Pittelkow, K.
Moth-Poulsen, U. Boas, J. B. Christensen, Langmuir
2003, 19, 7682; c) E. B. Mubofu, J. H. Clark, D. J. Mac-
quarrie, Green Chem. 2001, 3, 23; d) B. M. Choudary, S.
Madhi, N. S. Chowdari, M. L. Kantam, B. Sreedhar, J.
Am. Chem. Soc. 2002, 124, 14127; e) H. Sajiki, T. Kurita,
A. Kozaki, G. Zhang, Y. Kitamura, T. Maegawa, K. Hir-
ota, Synthesis 2005, 04, 537; f) K. Mori, T. Hara, M. Osh-
iba, T. Mizugaki, K. Ebitani, K. Kaneda, New J. Chem.
2005, 29, 1174; g) A. Molnar, A. Papp, K. Miklos, P. For-
go, Chem. Commun. 2003, 2626; h) D. Zim, A. L. Mon-
teiro, J. Dupont, Tetrahedron Lett. 2000, 41, 8199.
[4] a) B. M. Choudary, K. Jyothi, M. L. Kantam, B. Sreed-
har, Adv. Synth. Catal. 2004, 346, 45; b) B. M. Choudary,
K. Jyothi, M. Roy, M. L. Kantam, B. Sreedhar, Adv.
Synth. Catal. 2004, 346, 1471.
ꢀ
ꢀ
[9] For p Me C6H4Br and PhB(OH)2 coupling using
ꢀ
ꢀ
NAP Mg Pd(0) (0.5 mol %) in water at ambient tem-
perature; GC yield of 4-methylbiphenyl for K2CO3
(98%), K3PO4 (88%), KF (92%), NaOH(94%), Et 3N
(83%), Cs2CO3 (75%).
ꢀ
[10] Recent papers on C C coupling reactions catalyzed by
Pd species in the liquid phase coming from a solid Pd cat-
alyst: a) F. Zhao, B. M. Bhanage, M. Shirai, M. Arai,
Chem. Eur. J. 2000, 6, 843; b) F. Zhao, M. Shirai, Y.
Ikushima, M. Arai, J. Mol. Catal. A: Chem. 2002, 180,
211; c) S. S. Prockl, W. Kleist, M. A. Gruber, K. Kohler
Angew. Chem. Int. Ed. 2004, 43, 1881; d) S. P. Andrews,
A. F. Stepan, H. Tanaka, S. V. Ley, M. D. Smith, Adv.
Synth. Catal. 2005, 347, 647.
[5] a) P. Jeevanandam, K. J. Klabunde, Langmuir 2002, 18,
5309; b) K. J. Klabundae, R. Mulukutla, Nanoscale Mate-
rials in Chemistry, Wiley Interscience, New York, 2001,
Chapter 7, p 223.
2008
asc.wiley-vch.de
ꢀ 2005 Wiley-VCHVerlag GmbH& Co. KGaA, Weinheim
Adv. Synth. Catal. 2005, 347, 2002 – 2008