Suzuki-Miyaura reactions of aryl chloride derivatives with arylboronic acids using mesoporous silica-supported aryldicyclohexylphosphine

Article abstract of DOI:10.1002/adsc.200600286

The Suzuki-Miyaura reactions using mesoporous-supported aryldicyclohexylphosphine as ligand have been investigated. The catalysts were based on SBA-15 type mesoporous silica which was transformed in a four-step synthesis leading to a phosphine-containing hybrid material The most productive catalytic system studied was generated in situ from this material and the homogeneous palladium complex, Pd(OAc)₂. Other catalytic systems were studied for comparison [homogeneous cataysts, a "preformed" catalyst obtained by reaction of PdCl₂ (PhCN)₂ and the phosphine-containing material]. Variations involving the solvent system, the substrate aryl chloride and the arylboronic acid reactant were also studied. For both in situ and preformed cataiyst systems, high conversions and yields are obtained for activated aryl chlorides. Success of the reaction for unactivated aryl chlorides was limited to the catalyst formed in situ. The catalyst formed in situ was also shown to be reactive under aqueous reaction conditions in the cross-coupling of 1-(4-chlorophenyl)ethanone with phenylboronic acid.

Full text of DOI:10.1002/adsc.200600286

FULL PAPERS
DOI: 10.1002/adsc.200600286
Suzuki–Miyaura Reactions of ArylChol ride Derivatives with
Arylboronic Acids using Mesoporous Silica-Supported Aryl-
dicyclohexylphosphine
Reine Sayah,a,b Katarzyna Glegoła,b Eric Framery,b,* and VØronique Dufauda,*
a
Laboratoire de Chimie, UMR 5182 ENS/CNRS, Ecole Normale SupØrieure de Lyon, 46 allØe d’Italie,
69364 Lyon Cedex 07, France
Fax : (+33)-4-7272-8860; e-mail: vdufaud@ens-lyon.fr
Laboratoire de Synth›se AsymØtrique, UMR 5181 UCBL/CNRS, UniversitØ Claude Bernard Lyon 1,
b
43 boulevard du 11 Novembre 1918, 69622 Villeurbanne cedex, France
Fax : (+33)-4-7244-8160; e-mail: framery@univ-lyon1.fr
Received: June 23, 2006; Published online: January 8, 2007
Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/.
Abstract: The Suzuki–Miyaura reactions using meso- aryl chloride and the arylboronic acid reactant were
porous-supported
aryldicyclohexylphosphine
as also studied. For both in situ and preformed catalyst
ligand have been investigated. The catalysts were systems, high conversions and yields are obtained for
based on SBA-15 type mesoporous silica which was activated aryl chlorides. Success of the reaction for
transformed in a four-step synthesis leading to a unactivated aryl chlorides was limited to the catalyst
phosphine-containing hybrid material The most pro- formed in situ. The catalyst formed in situ was also
ductive catalytic system studied was generated in situ shown to be reactive under aqueous reaction condi-
from this material and the homogeneous palladium tions in the cross-coupling of 1-(4-chlorophenyl)etha-
complex, Pd(OAc)2. Other catalytic systems were none with phenylboronic acid.
G
studied for comparison [homogeneous cataysts, a
“preformed” catalyst obtained by reaction of PdCl2 Keywords: aryl chloride derivatives; organic-inorgan-
ACHTREUNG
Introduction
been recently reported and represent attractive alter-
natives to the homogeneous systems. Various methods
Biaryl derivatives are important substructures in fine are available for the anchoring of transition metal
chemistry and are of industrial interest in a wide complexes onto organic or inorganic carriers: includ-
range of applications including the preparation of ing entrapment, adsorption, ion-pair formation and
pharmaceuticals, herbicides, polymers, materials, covalent binding. Several examples of non-covalent
liquid crystals and ligands for catalysis.[1] Among the immobilization on a silica matrix can be cited: the flu-
different methodologies available for the formation of orous reversed-phase silica gel described by Bann-
C C bonds, the palladium-catalyzed cross-coupling warth,[24–26] the heterogeneous detergents based on
À
reaction of aryl halides with boronic acids, the so- silica gel obtained by Oehme[27] and zeolites contain-
called Suzuki–Miyaura reaction,[2–9] is one of the most ing PdCl2 studied by Garcia.[28] Nevertheless, the at-
general and powerful routes for the preparation of tachment of the metal complex to the support by co-
biaryl compounds.
valent bond formation provides many advantages
Because of economic and environmental concerns, over the non-covalent approach, the main one being
numerous efforts have been devoted to the develop- to reduce leaching and thus palladium contamination
ment of catalytic systems which can be efficiently re- of the products. In the last five years, several palladi-
covered and recycled while keeping the intrinsic activ- um complexes based on a silica matrix have been de-
ity and selectivity of the active center. Heterogeneous veloped by sol-gel processes or by anchoring proce-
palladium catalysts immobilized on activated dures onto mesoporous silica (SBA, MCM type, etc).
carbon,[10–15] silica[16–19] or organic polymers[20–23] have Oxime[29,30] or imine[31] carbapalladacycle complexes,
Adv. Synth. Catal. 2007, 349, 373 – 381
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373

Reine Sayah et al.
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carbene-bearing palladium complexes,[32] Pd(II) com-
In the present contribution, we report on the prepa-
plexes with N-N[33–38] or N-X (X=O, S)[39] chelation ration of aryldicyclohexylphosphine anchored onto
and triolefinic Pd(0) complex[40,41] have been de- mesoporous SBA-15 type silica material using a step-
scribed and their performances examined in the wise patterning approach. The applicability of the two
cross-coupling reactions of aryl iodides or aryl bro- supported metal complexes obtained from the silica-
mides with arylboronic acids. Generally, yields up modified phosphine, respectively, Pd
ACHTREUNG
to 90% were obtained for the desired coupling prod-
uct.
ACHTREUNG
From an industrial point of view, aryl chlorides, de- scribed.
spite their lack of reactivity, are more interesting sub-
strates as they are cheaper and readily accessible raw
materials. Only few examples of palladium catalysts Results and Discussion
on silica supports capable of activating chloroarenes
À
towards C C bonds formation reactions have been Stepwise Synthesis of Phosphine-Functionalized SBA-
described in the literature.[29,30,32,34,38] Generally, the 15 Silica Material
yields vary in a range situated between 60 and 90%
in the case of activated aryl chlorides. The recyclabili- The general approach used for heterogeneous catalyst
ty of these catalytic solids, which is a key point in the synthesis was the immobilization of the phosphine li-
development of heterogeneous catalysts, was not sys- gands on the surface of preformed mesoporous SBA-
tematically addressed by all authors. Corma et al.,[29,30] 15 type silica. As mentioned above, numerous exam-
however, have demonstrated that the oxime carbapal- ples of phosphine ligands tethered to oxide surfaces
ladacycle complex anchored onto a mercaptopropyl- have been reported, and a common drawback to that
modified silica surface could be reused eight times in approach is the reaction of the grafted phosphine
the Suzuki reaction of p-chloroacetophenone and functional groups with the oxide surface leading to
phenylboronic acid in water without noticeable de- non-coordinative phosphine oxides and consequently
creases in activity. Pleixats et al.,[38] on the other to catalyst leaching.[56] Thus, we adopted a multi-step
hand, have shown a significant decreases of conver- tethering protocol in which an initial functional
sion of m-chlorobenzonitrile upon recycling for each anchor is introduced, the surface is then deactivated
of the five consecutive cycles performed, using silica by silylation, and the phosphine is then generated in
materials containing di(2-pyridyl)methylamine-palla- two steps. Jones had previously demonstrated the pos-
dium dichloride complex as heterogeneous catalyst.
sibility of obtaining patterned surface modified by
In homogeneous catalytic systems, electron-rich aminopropyl functional groups.[57,58] In this study, the
and sterically hindered phosphines[42–52] seem to be functional group is introduced in a protected form as
the best ligands for the cross-coupling reactions of an imine, the structure of which determines the pat-
aryl chlorides with arylboronic acids.
terning of the eventual functional groups on the sur-
Recently, one of the authors has described the use face. The proof-of-concept studies cited above used a
of a new bulky and basic aryldicyclohexylphosphine very bulky trityl-containing patterning agent, and thus
based on d-glucosamine[53] or immobilized on poly- the amino groups were relatively widely spaced on
styrene or polystyrene/polyethyleneglycol copoly- the surface. In our case, we wished to generate chelat-
mer[54] as an effective ligand for the palladium-cata- ing ligand systems, and so we chose a less bulky pat-
lyzed cross-coupling reaction of activated aryl chlor- terning agent containing a benzyl group (Figure 1).
ides with arylboronic acid in organic or organic-aque- The benzylimine silane, 1, was easily obtained by con-
ous mixtures. To extend the scope of these initial densation of benzaldehyde and 3-aminopropyltrime-
studies, and potentially prepare mechanically and thoxysilane in methanol at room temperature. Note
chemically more stable heterogeneous catalysts, we that Jones has very recently published the utilization
chose to tether the aryldicyclohexylphosphine on an of this patterning agent to produce higher loadings
inorganic oxide. It is well known that the type of sup-
port material used may be a crucial factor in the per-
formance of the supported catalyst,[55] whether for its
mechanical properties, inductive electronic effects or
chemical stabilization of active species. Mesostruc-
tured porous silicas (e.g., MCM-41, MCM-48, SBA-
15) attained our attention as catalytic support due to
their specific surface (which can reach 1000 m2·gÀ1)
and the possibility of tuning pore size between 2–
10 nm, properties which are also accompanied by very
high thermal and mechanical stability.
Figure 1. Patterning agent for silica surface modification.
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Suzuki–Miyaura Reactions of Aryl Chloride Derivatives with Arylboronic Acids
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while maintaining site isolation between amine sites
on an SBA-15 silica surface.[59]
The hybrid material was produced by post-synthetic
modification of an SBA-15 type mesoporous
silica.[60–62] This class of support was chosen for the
very large pore aperture, which would facilitate the
introduction of bulky ligands, metal complexes and
substrates. The patterning agent, 1, was reacted with a
suspension of calcined SBA-15 in dry toluene at 808C
overnight. The reaction likely proceeds via the con-
densation of surface silanols of the oxide support with
the siloxane groups of 1. After the reaction period,
the solid was washed by Soxhlet extraction with
CH2Cl2 for 15 h, which assured the total removal of
physisorbed organic precursor to give 1.SBA-15.
We characterized 1.SBA-15 by a battery of spectro-
scopic and quantitative methods (thermogravimetric
analysis, elemental analysis, solid state 29Si, and
13C NMR, infrared spectroscopy, nitrogen sorption,
and powder XRD). These data are in good accord
with the recent Jones publication of a nearly identical
species prepared at room temperature (see Support-
ing Information for data not included in this discus-
sion).[59]
A highly ordered mesostructured hybrid material
was obtained with an organic content of 1.7 mmol/g
dry SiO2 (from elemental analysis). The 29Si CP-MAS
NMR (Supporting Information) exhibited peaks at
À53, À60 and À69 ppm (T1 T2 and T3 sites, respec-
,
tively) confirming the formation of a covalent bond
between the organosilane silicon and the surface. One
should note that there is a peak at 48 ppm in the 13C
CP-MAS NMR (Figure 2; bottom) of 1.SBA-15 indi-
cating the presence of residual methoxy groups at the
point of attachment with the surface, which is also
consistent with the presence of not fully condensed T1
and T2 sites.
Figure 2. Mesoporous silica-supported dicyclohexylarylphos-
phine, stepwise synthesis followed by CP-MAS 13C NMR
spectroscopy.
The overall synthetic process after the initial graft-
ing of the patterning agent employed is given in
Scheme 1. At each stage, the chemical transforma-
tions were monitored by CP-MAS 13C NMR spectros-
copy (Figure 2).
The residual surface silanol groups were first
capped with chlorotrimethylsilane (resulting in mate-
rial 2.SBA-15) in order to avoid interactions with the
silica surface in later steps. This was confirmed by the
appearance, in the 13C NMR spectrum of 2.SBA-15
(Figure 2), of a new resonance at À1.25 ppm charac-
teristic of the carbons of the trimethylsilyl group in
addition to the peaks attributed to the propyl-imino-
benzyl fragment. The nitrogen analysis of this materi-
al was not significantly different from that of 1.SBA-
15 (1.65 mmolgÀ1 vs. 1.7 mmolgÀ1).
The imine-grafted fragment was then transformed
into the corresponding amine by acid hydrolysis
(3.SBA-15, nitrogen microanalysis, 1.3 mmolgÀ1). The
Scheme 1. Mesoporous silica-supported dicyclohexylaryl-
phosphine prepared by stepwise transformation of a benzyl-
clean conversion to the amine was evidenced by the imino-grafted species.
Adv. Synth. Catal. 2007, 349, 373 – 381
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375

Reine Sayah et al.
FULL PAPERS
total disappearance of the aromatic (123–134 ppm) ligand in the final material may be present. An inde-
and the imine (162 ppm) carbons in the 13C NMR pendent route in which the fully developed ligand
(Figure 2) with the concomitant appearance of a new system is synthesized and isolated prior to grafting is
resonance at 40 ppm typical of the carbon adjacent to under way.
an amine functionality. Note that most of the amines
Physicochemical (X-ray powder diffraction) and
in 3.SBA-15 were obtained as their corresponding textural property data (nitrogen sorption isotherms)
salts due to the protonation of the nitrogen by HCl for the different hybrid materials have been gathered
(Cl/N molar ratio of 0.86) under the deprotection con- in the Supporting Information. X-ray diffraction pat-
ditions.
Finally, the direct condensation of 2’-(dicyclohexyl- clear peaks in the 2q-range of 0.6–38, typical of or-
phosphino)biphenyl-4-carboxylic acid, 2, with the dered hexagonal mesophases with d(100) spacing
amine functionalities of 3.SBA-15 in the presence of varying from 90 to 105 Š. This result indicates that
1-[3-dimethylaminopropyl]-3-ethylcarbodiimide hy- the ordered structure of the organic-inorganic hybrids
drochloride (EDC·HCl), 1-hydroxybenzotriazole has been maintained throughout the post-synthetic
(HOBT) and NaHCO3 as the base afforded the de- transformations. Nitrogen adsorption-desorption
terns of the supported organic species show three
AHCTREUNG
sired SBA-15 silica supported dicyclohexylphosphine measurements show a type IV isotherm typical of
material (4.SBA-15). The presence of a base was nec- mesoporous solids. Relatively narrow pore diameter
essary to trap the hydrochloric acid of the coupling distributions were observed for all materials with
reagent (EDC) and to neutralize the protonated median pore diameters between 49 and 58 Š. The sur-
amines of 3.SBA-15.
face area was determined by BET at each step of the
In the 13C CP-MAS NMR of 4.SBA-15 (Figure 2, synthesis. In accordance with the Jones observation,
top) one observes clear evidence for a condensation the grafting of the patterning agent 1 resulted in a
reaction in the appearance of a broad, very intense sharp decrease in surface area (to 350 m2·gÀ1). This
resonance in the aromatic region of the spectrum parameter was relatively unaffected by the methyla-
(127 ppm). Interpretation of the alkyl region is impos- tion and deprotection steps (2.SBA-15, 395 m2·gÀ1;
sible due to the broadening of peaks and overlap be- 3.SBA-15, 410 m2·gÀ1) whereas the final condensation
tween the different alkyl species peaks present. More step leading to the incorporation of the bulky phos-
significantly, one discerns the appearance of a weak phine ligand produces another sharp decrease in spe-
peak which can be interpreted as a carbonyl reso- cific surface area (4.SBA-15, 200 m2·gÀ1).
nance at 169 ppm.
This phosphine-containing mesoporous hybrid ma-
The 31P CP-MAS NMR of 4.SBA-15 (Figure 3) ex- terial, 4.SBA-15, was used as a support for the palla-
hibits an intense signal at À15.0 ppm, which can be at- dium catalyzed Suzuki cross-coupling of various aryl
tributed to the grafted phosphine ligand (the chlorides with boronic acids. Thus, PdCl2(PhCN)2 (0.5
G
31P NMR spectrum of 2 exhibits a single peak at equivalents per phosphine as determined by micro-
À12.0 ppm), and a weak resonance at 52.9 ppm, analysis) was introduced into a dichloromethane
which may be due to some oxidation of the phospho- slurry of 4.SBA-15 at room temperature. After sever-
rus species. The phosphorus analysis (0.7%wt) corre- al hours, the new material 5.SBA-15 was recovered by
sponds to a 4.SBA-15 loading of only 0.3 mmol/g filtration and washed several times with CH2Cl2. The
SiO2 suggesting that the condensation reaction resultant yellow solid was analyzed by microanalysis
(Figure 3) between the carboxylic acid-derived phos- (1%wt Pd, P:Pd ratio of 1.8:1). In the catalytic stud-
phine and the aminopropyl-functionalized silica was ies, this pre-made catalyst is compared to relevant ho-
not complete (~20% yield). This yield is somewhat mogeneous and heterogeneous model species, includ-
disappointing, and a potentially coordinating amino ing in situ systems based on 4.SBA-15 with different
palladium sources.
Catalysis
The cross-coupling Suzuki–Miyaura reactions of vari-
ous aryl chlorides with arylboronic acids (Scheme 2)
were examined under different reaction conditions
and the results are shown in Table 1.
Since water is known to increase the activity of the
Suzuki–Miyaura catalyst,[63] three kinds of solvents
were used: toluene, water or a 3/2/2 toluene/EtOH/
H2O mixture. (Note that it is necessary to change the
nature of the base in each case due to solubility and
Figure 3. CP-MAS 31P NMR of mesoporous silica-supported
dicyclohexylarylphosphine.
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Suzuki–Miyaura Reactions of Aryl Chloride Derivatives with Arylboronic Acids
FULL PAPERS
0.6% M of supported phosphine 4.SBA-15 and the
supported palladium-catalyst 5.SBA-15 with no addi-
tional phosphine. (Note that, as mentioned in the
characterization section of the paper, as the yield of
the 3.SBA-15 to 4.SBA-15 coupling reaction was low,
one cannot rule out coordination of some palladium
to surface amino ligand moieties. We therefore ran a
control experiment using 3.SBA-15 under optimized
conditions ( entry 8). Very low yield was observed in
this experiment suggesting that the surface amino li-
gands are not involved in a major way in the catalyst
activity discussed below.)
Scheme 2. Palladium-catalyzed Suzuki–Miyaura cross-cou-
pling of aryl chlorides and boronic acids.
stability issues.) The reactions were catalyzed with
For comparison, some homogeneous model reac-
0.2% M of palladium-catalyst in the presence of 3 tions were investigated. Given that ligand-free Pd-
equivalents of base and with an aryl chloride/arylbor-
C
base at 1008C; and in the case of a 3/2/2 toluene/ runs were performed with Pd(OAc)2. Regardless of
U
EtOH/H2O solvent mixture, Na2CO3 was used as the the solvent system, no conversion was observed
base at 808C (the reaction temperature is limited by (Table 1, entries 1–3). The addition of three equiva-
the boiling point of ethanol). Two heterogeneous pal- lents of phosphine, 2’-(dicyclohexylphosphino)bi-
ladium catalysts were used: the catalyst formed in situ phenyl-4-carboxylic acid 2, leads to complete conver-
from 0.2% M of Pd
N
N
Table 1. Suzuki-Miyaura reactions of various aryl chlorides with arylboronic acids.[a]
Entry
R1
R2
R3
Catalytic system
Solvent[b]
Conversion[c] (Yield[d]) [%]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
H
H
H
H
H
H
H
H
H
H
Me
H
H
H
H
H
H
H
H
H
Me
H
H
H
H
H
H
H
H
H
H
H
H
Me
H
H
H
H
H
H
H
H
H
H
NO2
NO2
Ac
Pd
Pd
Pd
Pd
Pd
Pd
Pd
Pd
Pd
C
Toluene
Toluene/EtOH/H2O (3/2/2)
Water
Toluene/EtOH/H2O (3/2/2)
Toluene
Toluene/EtOH/H2O (3/2/2)
Toluene
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Water
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Toluene/EtOH/H2O (3/2/2)
Water
0
0
0
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
NO2
CHO
CN
Me
Ac
NO2
CHO
CN
100 (96)
6
98
20
3
100 (95)
99 (98)
91 (90)
95
[e]
PdCl2
ACHTREUNG
Pd
Pd
Pd
Pd
Pd
Pd
53
97 (68)
90 (81)
78 (62)
94 (92)
27
100 (89)
0
100 (90)
0
5.SBA-15[e]
5.SBA-15[e]
5.SBA-15[e]
5.SBA-15[e]
5.SBA-15[e]
5.SBA-15[e]
Me
NO2
Ac
[a]
Reaction conditions: [Ar-Cl]=0.07M; [Ar-Cl]/[arylboronic acid]/[base]/[Pd system]=1/1.1/3/0.002 (the ratio of added
A
phosphine/Pd was 3/1); 20 h.
[b]
In the case of toluene, the base was K3PO4, and the reaction temperature was 1008C; in the case of water, the base was
K2CO3, and the reaction temperature was 1008C; in the case of toluene/EtOH/H2O, the base was Na2CO3 and the reac-
tion temperature was 808C.
The conversions were determined by GC.
Isolated chemical yield after column chromatography.
[c]
[d]
[e]
No additional phosphine.
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377

Reine Sayah et al.
FULL PAPERS
with phenylboronic acid in the mixed solvent system chloro-4-nitrobenzene and 4-chlorobenzonitrile, the
(Table 1, entry 4). In the same way, we studied the re- Suzuki–Miyaura reactions with phenylboronic acid
actions catalyzed from Pd(PPh3)2Cl2 without addition- led to excellent conversions and very good yields
A
al phosphine. A very low conversion (6%) was ob- (Table 1, entries 17 and 19). As seen with the catalyst
tained when toluene was employed as solvent formed in situ, the aldehyde substituted substrate, 4-
(Table 1, entry 5), and an almost quantitative conver- chlorobenzaldehyde, led to poor conversion (27%)
sion (98%) when the 3/2/2 toluene/EtOH/H2O mix- (Table 1, entry 18). Contrary to the result with the
ture was used as solvent (Table 1, entry 6). Thus, catalyst formed in situ, the unactivated substrate, 1-
Suzuki–Miyaura reactions are quite dependent on the chloro-4-methylbenzene underwent no measurable re-
experimental conditions, and especially on solvents action with phenylboronic acid at 808C (Table 1,
and palladium complexes used.
entry 20). Again, the 4-methylphenylboronic acid re-
In the study of heterogeneous catalysts prepared in actant was shown to be effective when coupled with
situ, we first examined the influence of solvents and 1-chloro-4-nitrobenzene (Table 1, entry 21), as full
palladium precursors (Table 1, entries 7, 9, 10). In the conversion and a 90% of yield were obtained.
case of catalysts formed from Pd
A
Finally, for economic and environmental concerns,
conversion was obtained in toluene (Table 1, entry 7), we have tested the performance of the catalysts in the
whereas full conversion and a 95% yield were deter- cross-coupling reaction between 1-(4-chlorophenyl)-
mined when the mixed toluene/EtOH/H2O medium ethanone and phenylboronic acid using water as sol-
was used (Table 1, entry 9). Changing to PdCl2 vent (Table 1, entries 16 and 22). In the case of pre-
ACHTREUNG
AHCTREUNG
Different substrates, three activated aryl chlorides sion of 78% was obtained with an isolated chemical
and one unactivated aryl chloride, were studied in the yield in 1-biphenyl-4-ylethanone of 62%. These first
mixed solvent system using Pd(OAc)2 (Table 1, en- results seem to show that the silica-supported palladi-
A
tries 9, 11–15). Differences were observed between um catalyst prepared in situ is more active and/or
activating groups in three runs involving aryl chlor- stable than the preformed catalyst for the Suzuki–
ides bearing electron-withdrawing groups (R3 =NO2, Miyaura reaction.
CHO and CN) (Table 1, entries 9, 13 and 14). Nitro
and cyano substitution of the aryl chloride leads to
the corresponding biaryl compounds in high conver- Conclusions
sion (>97%) whereas the aldehyde substituted aryl
chloride gave only 53% conversion.
Most surprisingly, the in situ catalyst formed from of an aryldicyclohexylphosphine functionalized SBA-
4.SBA-15 and Pd(OAc)2 effectively catalyzed the re- 15 silica material using a patterning approach and
In summary, we have described the stepwise synthesis
AHCTREUNG
action of an unactivated susbstrate, 1-chloro-4-methyl- demonstrated its efficiency as a support for the palla-
benzene, which bears an electron-donating group, dium-catalyzed Suzuki–Miyaura cross-coupling of var-
with phenylboronic acid (Table 1, entry 15), leading to ious substituted aryl chlorides with arylboronic acids.
very high conversion (90%) and a good yield (81%). The novel supported catalyst systems were studied
Note that in the case of the same aryldicyclohexyl- under a variety of reaction conditions with varying
phosphine supported on organic polymer (polystyrene substrates and reactants. Two principle new catalysts
or polystyrene/polyethylene glycol copolymer),[54] no were studied, that obtained in situ from the phos-
yield or a very low yield (<30%) were obtained phine-modified SBA-15 mesoporous hybrid material,
under the same reaction conditions. Thus, the support 4.SBA-15, and a palladium precursor, and that ob-
seems to have a great influence on the activity of the tained and isolated from the prior reaction of the pre-
palladium complex on the Suzuki–Miyaura reaction.
cursor with 4.SBA-15. For both systems, high conver-
The effect of the structure of the boronic acid reac- sions and yields are obtained for activated aryl chlor-
tant was studied. The reaction of 1-chloro-4-nitroben- ides. Success for the reaction of unactivated aryl
zene with 4-methylphenylboronic acid was compared chlorides was limited to the catalyst formed in situ.
to that with the more sterically encumbered reactant The catalyst formed in situ was also shown to be reac-
2, 6-dimethylphenylboronic acid (Table 1, entries 11 tive under aqueous reaction conditions in the cross-
and 12): very similar conversions of 91% or 95%, re- coupling of 1-(4-chlorophenyl)ethanone with phenyl-
spectively, were obtained indicating little or no effect. boronic acid. Further studies are conducted and will
The use of the preformed supported palladium-cat- be reported in due course to address the recyclability
alyst 5.SBA-15 was studied in five cross-coupling re- of these novel catalytic systems especially in water.
actions in the mixed solvent system. In the case of
aryl chlorides bearing electron-withdrawing groups, 1-
378
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Adv. Synth. Catal. 2007, 349, 373 – 381

Suzuki–Miyaura Reactions of Aryl Chloride Derivatives with Arylboronic Acids
FULL PAPERS
ExperimentalSection
Synthesis of 3-N-Benzylideneaminopropyltrimeth-
oxysilane Patterning Agent (1)
GeneralRemarks
A slight excess of benzaldehyde (2.13 g, 0.02 mol) was stir-
red at room temperature with 3-aminopropyltrimethoxysi-
lane (3 g, 0.016 mol) in dry methanol overnight. The reac-
tion mixture was then filtered and methanol was removed
under vacuum. The crude benzylimine product was obtained
All manipulations were conducted under strict inert atmos-
phere or vacuum conditions using Schlenk techniques. The
solvents were dried using standard methods and stored over
activated 4 Š molecular sieves. Methanol was dehydrated by
reaction with magnesium ethoxide prepared from magnesi-
um turnings and iodine. Tetraethoxysilane (TEOS), poly-
(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)
block copolymer (Pluronic 123, MW: 5000), redistilled ben-
zaldehyde, 4-chlorobenzonitrile, 1-chloro-4-nitrobenzene, 1-
chloro-4-methylbenzene were purchased from Aldrich
Chemical and used without further purification. 4-chloro-
benzaldehyde, phenylboronic acid, 4-methylphenylboronic,
2, 6-dimethylphenylboronic acid, 1-iodo 2-bromobenzene, n-
butyllithium 1.6M in hexanes were obtained from Acros
1
in 70% yield. H NMR (CD2Cl2, 200 MHz): d=0.76 (m, 2H,
SiCH2), 1.86 (m, 2H, SiCH2CH2), 3.64 (11H, N-CH2 and
CH3O), 7.4 (3H, phenyl), 7.8 (2H, phenyl), 8.3 (1H, N=
CH-Ph); 13C NMR (CD2Cl2, 50 MHz): d=6.8 (CH2Si), 24.2
(CH2CH2-Si), 50.8 (CH3O), 64.0 (N-CH2), 128.0, 128.5,
130.4, 136.7 (phenyl), 160.6 (N=CH).
Preparation of Silica-Supported Aryldicyclohexyl-
phosphine
Mesoporous SBA-15 type silica was used as support and was
prepared by the acid-catalyzed, non-ionic assembly pathway
described by Margolese et al.[75] The structure directing
agent (Pluronic 123) was removed quantitatively from the
as-synthesized material by calcination at 5008C overnight
under air as evidenced by TGA analysis and infrared spec-
troscopy. Prior to the grafting reaction, the surfactant-free
mesoporous silica was rigorously dried under a flow of nitro-
gen at 2008C. The aryldicyclohexylphosphine functionalized
SBA-15 was prepared in four steps:
and palladium chloride from Alfa. PdCl2(PhCN)2 was pre-
C
Characterization
All solid-state NMR spectra were recorded on Bruker DSX-
300 or Avance-500 spectrometers equipped with a standard
4 mm probehead. The spinning rate was typically 10 kHz.
13C, 29Si and 31P NMR spectra were obtained by use of cross-
polarization (contact time 5 ms). To achieve a good polariza-
tion transfer, a ramp was used on the X channel. Recycle
Synthesis of Benzyliminopropyl Functionalized SBA-
15 Silica, 1.SBA-15
1
delays were typically 1 s (a study on the H nucleus showed
1
that it was sufficient to allow all protons to fully relax). H,
Compound 1 (1.0 g, 3.74 mmol) was added to a suspension
of SBA-15 silica (2 g) in dry toluene and stirred at 258C for
two hours to allow the diffusion of the molecular precursor
into the channels of the pores. The reaction mixture was
then heated at 808C overnight. The resulting solid was fil-
tered under nitrogen, washed thoroughly with a small
amount of toluene followed by Soxhlet extraction with
CH2Cl2 and finally dried at 308C under vacuum. ICP-AES
analysis: 15.40%wt C, 2.07%wt H, 1.82%wt N. The organic
content of 1.SBA-15 was found to be 1.7 mmolgÀ1SiO2 de-
rived from nitrogen analysis (see Supporting Information).
13C and 29Si MAS spectra were referenced to tetramethylsi-
lane. 31P MAS spectra were referenced to 85% H3PO4.
X-ray powder diffraction (XRD) data were acquired on a
Bruker D5005 diffractometer using Cu Ka radiation (l=
1054184 Š). A Netzsch thermoanalyser STA 409PC was
used for simultaneous thermal analysis combining thermog-
ravimetric (TGA) and differential thermoanalysis (DTA) at
a heating rate of 58CminÀ1 in air. Nitrogen adsorption and
desorption isotherms were measured at 77 K. The organic-
inorganic hybrids were evacuated at 1608C for 24 h before
the measurements. Specific surface areas were calculated
following the BET procedure. Pore size distribution was ob-
tained by using the BJH pore analysis applied to the desorp-
tion branch of the nitrogen adsorption/desorption isotherm.
The palladium content determinations for 5.SBA-15 cata-
lyst were performed by ICP-AES spectroscopy from a solu-
tion obtained by treatment of the catalyst with a mixture of
HBF4, HNO3 and HCl in a Teflon reactor at 1808C.
ResidualSial no-lCapping Reaction, 2.SBA-15
The remaining silanol groups in 1.SBA-15 were capped by
silylation with chlorotrimethylsilane at 608C in toluene for
3 h. The excess of silane was removed by washing the solid
with dry toluene. ICP-AES analysis: 12.71%wt C, 2.35%wt
H, 1.74%wt N. The organic content of 2.SBA-15 was found
to be 1.65 mmolgÀ1SiO2 derived from nitrogen analysis (see
Supporting Information).
Liquid NMR spectra were recorded on a Bruker AC-300
spectrometer and referenced as following: 1H (300 MHz),
internal SiMe4 at d=0.00 ppm, 13C (75 MHz), internal
CDCl3 at d=77.2 ppm, and 31P (121 MHz), external 85%
H3PO4 at d=0.00 ppm. Flash chromatography was per-
formed at a pressure slightly higher than atmospheric pres-
sure using silica (Merck Silica Gel 60, 230–240 mesh).
GC analyses were performed on a Shimadzu GC-14B
chromatograph equipped with a FID detector, a C-R6A in-
tegrator and a Quadrex OV1 column (30 m”0.25 mm).
Helium was used as carrier gas (initial temperature1208C,
heating rate 108CminÀ1 up to 2508C).
Aminopropyl-Functionalized SBA-15 Silica, 3.SBA-15
Aminopropyl-grafted fragments were generated by acid hy-
drolysis of the imino functionalities in 2.SBA-15. Typically,
1 g of 2.SBA-15 was suspended in a 2/2/1 solution of H2O/
MeOH/HCl (37% wt) and stirred at room temperature
overnight. The solid was filtered, washed thoroughly with
water, methanol and THF and then dried under vacuum at
room temperature. ICP-AES analysis: 5.74%wt C, 2.06%wt
Adv. Synth. Catal. 2007, 349, 373 – 381
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.asc.wiley-vch.de
379

Reine Sayah et al.
FULL PAPERS
H, 1.51%wt N, 3.33%wt Cl. Note that most of the primary
amines (>85%) were protonated by HCl. The organic con-
tent of 3.SBA-15 was found to be 1.3 mmolgÀ1SiO2 derived
from nitrogen analysis (see Supporting Information).
analysis 0.7%wt P) or 5.SBA-15 (21.28 mg, 2 mmol, based
on palladium analysis 1%wt Pd)] and toluene (3 mL) were
placed in a flask under argon. The solution was stirred for
30 min at room temperature. Aryl halide (1 mmol) and aryl-
boronic acid (1.1 mmol) dissolved in a mixture of toluene
(3 mL) and EtOH (4 mL) were then added in the flask, fol-
lowed by addition of Na2CO3 (317.97 mg, 3 mmol) in water
(4 mL). The resulting mixture was stirred at 808C for 20 h.
After cooling to room temperature, the heterogeneous solu-
tion was filtered, and the two phases of the filtrate were sep-
arated. The EtOH/H2O layer was washed twice with tolu-
ene, and the combined organic phases were dried over
Na2SO4. Evaporation of the solvent under reduced pressure
gives the corresponding crude biaryl compound, which was
purified by flash chromatography on silica gel to give the
pure coupling product. (AcOEt/petroleum ether: 1/30).
Aryldicyclohexylphosphine Functionalized SBA-15
Silica, 4.SBA-15
Phosphino-binding sites were introduced through the con-
densation of carboxylic acid-derived aryldicyclohexylphos-
phine, 2, with aminopropyl-functionalized SBA-15 silica in
the presence of coupling reagents. Typically, a mixture of
3.SBA-15 (192.3 mg, 1.3 mmolgÀ1SiO2 of NH2 groups), car-
boxylic acid, 2 (100 mg, 0.253 mmol), EDC.HCl (78 mg,
0.405 mmol), HOBT (68 mg, 0.506 mmol) and NaHCO3 as
the base (55 mg, 0.655 mmol) in DMF (20 mL) was stirred
at room temperature for 48 h. The solid was collected by fil-
tration under nitrogen, washed with deaerated DMF, metha-
nol and water and Soxhlet extracted with dichloromethane.
Finally, the solid was dried under reduced pressure at 258C
overnight. ICP-AES analysis: 0.7%wt P. The organic con-
tent of 4.SBA-15 was found to be 0.3 mmolgÀ1SiO2 derived
from phosphorus analysis (see Supporting Information).
Acknowledgements
KG and RS thank the French Ministry of Education for a fel-
lowship.
Palladium-Bound Aryldicyclohexylphosphine
Functionalized SBA-15 Silica, 5.SBA-15
Two equivalents of 4.SBA-15 (0.3 mmolgÀ1SiO2 of phos-
phine ligand) were reacted with one equivalent of bis(ben-
zonitrile)palladium dichloride at room temperature in di-
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