PEG-supported dipyridyl ligand for palladium-catalyzed Suzuki and Suzuki-type reactions in PEG and aqueous media

Article abstract of DOI:10.1055/s-2006-951488

An air- and water-stable PEG-supported bidentate nitrogen ligand is prepared and its applications in the palladium-catalyzed Suzuki reaction of aryl halides with arylboronic acids in PEG and Suzuki-type reaction of aryl halides with sodium tetraphenylborate in aqueous media are reported. The homogeneous catalyst system is environmentally friendly and offers the advantages of high activity, reusability and easy separation. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2006-951488

LETTER
2553
PEG-Supported Dipyridyl Ligand for Palladium-Catalyzed Suzuki and
Suzuki-Type Reactions in PEG and Aqueous Media
P
EG-SupportedDipyrid
e
yl Ligand
f
n
or Palladium
p
-CatalyzedS
e
uzuki
R
eac
n
tions g Mai, Lianxun Gao*
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
Graduate School of Chinese Academy of Sciences, Changchun 130022, P. R. of China
Fax +86(431)5685653; E-mail: lxgao@ciac.jl.cn
Received 27 June 2006
to replace ILs in catalytic systems.13 Li and co-workers
Abstract: An air- and water-stable PEG-supported bidentate nitro-
have reported Pd(OAc)2/DABCO/PEG-400 system for
gen ligand is prepared and its applications in the palladium-cata-
lyzed Suzuki reaction of aryl halides with arylboronic acids in PEG
and Suzuki-type reaction of aryl halides with sodium tetraphenyl-
Suzuki–Miyaura reaction recently.14 Though the system
could be recycled and reused five times without any loss
borate in aqueous media are reported. The homogeneous catalyst of catalytic activity, it is difficult to avoid the leaching of
system is environmentally friendly and offers the advantages of
high activity, reusability and easy separation.
DABCO every time. Corma et al reported an oxime
carbapalladacycle that was covalently anchored on PEG
for carbon–carbon coupling reactions.15 The activity of
Key words: Suzuki reaction, ligand, reusability, PEG
their catalytic system was moderate. In view of our previ-
ous report on the synthesis of imidazolium ionic liquid
grafted 2,2¢-bipyridine,16 herein, we report the synthesis
The Suzuki–Miyaura cross-coupling reaction has
of the PEG-supported dipyridyl ligand and its application
in Suzuki and Suzuki-type reactions using PEG and PEG–
water as solvents.
emerged as an extremely powerful, attractive, and widely
utilized method for the construction of carbon–carbon
bonds.1 The reaction has been applied to many areas,2
including natural product synthesis.3 A wide variety of
palladium catalysts efficiently promote the couplings of
aryl halides and other electrophiles with organoboron
compounds, usually combinations of palladium salts or
complexes with phosphorus ligands, such as phosphines,4
phosphites,5 and phosphine oxides.6 However, phos-
phorus ligands, especially the electron-rich phosphine
ligands, are often toxic, water-, and air-sensitive and
therefore require water-, and air-free handling to mini-
mize ligand oxidation. In such case, reuse of these cata-
lysts is difficult.7 Therefore, the development of
phosphine-free recycling catalytic systems is focused in
organic chemistry.8
We selected PEG with a molecular weight of 2000 Da as
the support. The preparation of ligand 1 was easily
achieved by starting with mesylation of the PEG-2000’s
terminal alcohol groups. Mesylation of PEG proceeded in
high yields (97%). The procedure commonly used17 was
modified by using trioctylamine (TOA) in place of tri-
ethylamine (TEA). The use of the less polar trioctylamine
(TOA) was better because the by-product triethylamine
hydrogen chloride was difficult to separate from PEG
dimesylate. Replacement of TEA with the much more
lipophilic TOA is an efficient solution to this problem,
since TOA·HCl unlike TEA·HCl, is soluble in diethyl
ether, the common solvent used for precipitating PEGs.
In view of economical and environmental reasons, the
development of recyclable catalytic systems is one of the
most challenging fields in laboratory and industry. A
more facile method is to immobilize the catalyst in a
liquid phase such as ionic liquids (ILs).9 Though ionic
liquids have been adopted as a reaction media for the
recycling of catalysts in a broad range of catalytic reac-
tions,10 they are very expensive and their toxicity and en-
vironmental burden data are for the most part unknown.
OH
HO
PEG
a
O
S
O
S
O
O
PEG
O
O
b
Poly(ethylene glycol) (PEG) and its monomethyl ethers
are known to be inexpensive, thermally stable, recover-
able, and non-toxic media for catalysts.11 Furthermore, as
a water-soluble polymer, it could be used to recover cata-
lysts and ligands in organic synthesis.12 More recently,
PEG has been successfully used as an alternative solvent
N
N
N
N
O
O
PEG
1
Scheme 1 Reagents and conditions: a) PEG-2000, MeSO2Cl, TOA,
CH2Cl2, 0 °C, 97%; b) bis(2-pyridyl)methanol, NaH, THF, reflux,
61%.
SYNLETT 2006, No. 16, pp 2553–2558
0
4
.1
0
.2
0
0
6
Advanced online publication: 22.09.2006
DOI: 10.1055/s-2006-951488; Art ID: W12706ST
© Georg Thieme Verlag Stuttgart · New York

2554
W. Mai, L. Gao
LETTER
As shown in Scheme 1, the first step proceeded smoothly
in 97% isolated yield. For the second step, the 61% yield
of bis(2-pyridyl)methanol anchored on PEG was deter-
Table 1 Pd-Catalyzed Suzuki–Miyaura Reaction of 4-Bromoani-
sole with Phenylboronic Acid in PEGa
Pd(OAc)2/1
MeO
Br
+
B(OH)2
MeO
1
mined by H NMR. Nevertheless, we found that the
base,
PEG-2000
110 °C, 15 h
presence of incompletely functionalized PEG was not det-
rimental for the catalytic activity of the new ligand. In
fact, we later used PEG as solvent for our reaction. Inter-
estingly, though PEG is highly hygroscopic, the yellow
solid 1 is air and moisture stable when left in air for three
months.
2a
4a
3a
Entry
Pd(mol%)
0.2
Base
Solvent
Yield (%)b
1
2
3
4
5
6
7
8
K2CO3
PEG-2000
PEG-2000
PEG-2000
PEG-2000
H2O
44c
91
70
85
52d
86
74
68
0.2
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
NaOAc
NaOH
With ligand 1 in hand, we first tested the catalytic activity
of Pd(OAc)2/1 in PEG-2000 for the Suzuki–Miyaura reac-
tion between 4-bromoanisole (2a) and phenylboronic acid
(3a), and the results are summarized in Table 1. High
yields were observed for the coupling reaction when 1
was used as the ligand. In the absence of 1, only 44% yield
of the coupling product 4a was obtained (Table 1, entry
1), whereas in the presence of 1, the yield of 4a was in-
creased to 91% (Table 1, entry 2). When Pd loading was
decreased, the yield of 4a also decreased (Table 1, entry 3
and 4). Other bases such as sodium carbonate, sodium
acetate and sodium hydroxide were no better choices for
this coupling reaction under the same conditions (Table 1,
entry 6, 7 and 8). Ligand 1 is soluble in water, but when
water was used as solvent, only 52% yield of 4a was
isolated after 24 hours (Table 1, entry 5), because the sub-
strates were not well soluble in water.
0.02
0.1
0.2
0.2
PEG-2000
PEG-2000
PEG-2000
0.2
0.2
a Reaction conditions: Pd(OAc)2/1 (1:1), 4-bromoanisole (2 mmol),
phenylboronic acid (2.2 mmol), base (4 mmol), PEG (3 g), 110 °C, 15
h.
b Isolated yield.
c Prepared without 1.
d Reaction time was 24 h.
reaction was performed without the protection of an inert
gas. It was interesting that Pd black emerged quickly after
2 hours in the absence of 1, but it did not appear in the
presence of 1. It indicated that 1 could stabilize the metal
during the reaction. Unfortunately, the Pd(OAc)2/1/PEG
catalytic system was less effective for the reaction of aryl
chlorides. The reaction of activated aryl chloride 2j with
3a afforded 69% yield of corresponding coupled product
5 after 30 hours using Pd(OAc)2 (3.0 mol%) (Table 2,
entry 15). For the chlorobenzene, only 45% yield was
obtained (Table 2, entry 14).
Using the optimized reaction conditions, we next exam-
ined the application of Pd(OAc)2/1/PEG system to the
cross-coupling of a variety of aryl halides with several
arylboronic acids and the results are summarized in
Table 2. Under standard conditions, PEG-2000 as solvent,
potassium carbonate as base, and Pd(OAc)2/1 at 110 °C,
both electron-poor and electron-rich aryl bromides were
cleanly coupled to give products in high yields (85–98%).
Several arylboronic acids 3a–d were tested and they all
reacted with aryl bromides smoothly even with the steri-
cally more hindered 2-methoxyphenylboronic acid (3b)
(Table 2, entry 8 and 9). It was worth noting that this
Table 2 Pd(OAc)2/1/PEG-Catalyzed Cross-Coupling of Aryl Halides with Arylboronic Acidsa
Pd(OAc)2/1
X
+
R'
B(OH)2
R
K2CO3 (2 equiv)
R
R'
PEG-2000, 110 °C
Entry
1
RArX
R¢ArB(OH)2
Time (h)
15
Products
Yield (%)b
87
Br
B(OH)2
2a
3a
3a
3a
4
O
O
B(OH)2
B(OH)2
Br
2
3
18
15
98
95
2b
5
OHC
2c
Br
OHC
6
Synlett 2006, No. 16, 2553–2558 © Thieme Stuttgart · New York

LETTER
PEG-Supported Dipyridyl Ligand for Palladium-Catalyzed Suzuki Reactions
2555
Table 2 Pd(OAc)2/1/PEG-Catalyzed Cross-Coupling of Aryl Halides with Arylboronic Acidsa (continued)
Pd(OAc)2/1
X
+
R'
B(OH)2
R
K2CO3 (2 equiv)
R
R'
PEG-2000, 110 °C
Entry
4
RArX
R¢ArB(OH)2
Time (h)
18
Products
Yield (%)b
MeO
Br
MeO
B(OH)2
91
2d
3a
3a
7
B(OH)2
Br
5
6
18
24
92
92
2e
Br
2f
8
9
Br
B(OH)2
B(OH)2
3a
3a
Br
7
24
98
2g
10
HO
HO
Br
B(OH)2
8
9
24
24
85
90
MeO
MeO
OMe
2h
3b
11
O
HO
B(OH)2
OMe
Br
Br
2b
3b
F3C
3c
12
O
O
B(OH)2
CF3
10
11
12
15
18
15
95
89
93
13
2b
F3C
B(OH)2
MeO
Br
MeO
CF3
2d
3c
14
O
O
B(OH)2
Br
3d
3d
15
16
2b
2g
Br
B(OH)2
13
15
97
45c
69c
B(OH)2
Cl
14
15
30
30
2i
O
3a
3a
4
O
B(OH)2
Cl
2j
5
a Reaction conditions: ArX (2 mmol), ArB(OH)2 (2.2 mmol), K2CO3 (4 mmol), PEG-2000 (3 g), Pd(OAc)2 (0.004 mmol), 110 °C (bath
temperature).
b Isolated yield.
c Catalyst loading: 3.0 mmol% Pd.
Synlett 2006, No. 16, 2553–2558 © Thieme Stuttgart · New York

2556
W. Mai, L. Gao
LETTER
To extend the application scope of the catalytic system,
we carried out Suzuki-type reaction of aryl halides with
sodium tetraphenylborate (NaBPh4) in the system using
water as co-solvent. As a new type of borate source,
NaBPh4 is a stable and commercially available reagent for
the Suzuki reaction. Recently, Bumagin18 and Xu19 report-
ed palladium-catalyzed Suzuki reaction by using NaBPh4
in water. But the aryl halides they used had limited advan-
tages; these aryl halides must be soluble or partly soluble
in water. Herein, we used PEG–H2O as solvent and many
insoluble aryl halides could react with NaBPh4 smoothly.
Initially, we explored the conditions for the reaction by
using Pd(OAc)2–1–PEG–H2O catalytic system. We found
that sodium hydroxide as base was the best choice for the
reaction and potassium carbonate, sodium acetate and
sodium carbonate were less effective. In view of Zhang’s
report on Suzuki coupling in PEG–H2O recently20, we
found that when the amount of PEG in water was 1.2 g/
mL and Pd loading was 0.5 mol%, the reaction was the
most efficient and the detailed results are summarized in
Table 3. We found that the reaction proceeded much more
smoothly when sodium tetraphenylborate was used in-
stead of arylboronic acids. Many aryl bromides including
electron-poor and electron–rich substrates 2a–g could
react with NaBPh4 in the Pd(OAc)2/1/PEG–H2O catalytic
system within two to five hours and the yields of corre-
sponding coupling products 4–10 were higher than those
shown in Table 2. It was worth noting that only 0.25
equivalent of NaBPh4 was enough for this reaction. The
concise mechanism had been reported in literature.19 In
order to test the activity of the catalytic system, we select-
ed three aryl chlorides for the reaction. Unfortunately, the
attempt to couple 4-chlorobiphenyl (2l) with NaBPh4 was
not successful even though extended reaction time and 3.0
mmol% Pd loading were employed (Table 3, entry 10). A
moderate yield could be obtained with 4-chlorobenzalde-
hyde (2k) whereas the yield of the coupling product with
chlorobenzene (2i) was just 14% (Table 3, entry 9 and 8).
Table 3 Pd(OAc)2/1/PEG–H2O-Catalyzed Suzuki-Type Reaction
of Aryl Halides with Sodium Tetraphenylboratea
Pd(OAc)2/1
X
+ NaBPh4
NaOH, (2 equiv)
R
R
PEG–H2O, 110 °C
Entry ArX
1
Time (h) Product Yield (%)b
Br
2
2
2
5
4
5
6
7
99
99
99
93
2a
O
Br
2
2b
OHC
Br
3
2c
MeO
Br
4
2d
Br
5
5
5
8
9
90
95
2e
Br
Br
6
2f
Br
7
2
10
98
2g
Cl
8
15
15
4
6
14c
67c
2i
OHC
Cl
9
Having established the scope of the new reaction system,
our attention was focused on the recycling of the system.
In order to evaluate the recycling potential of the catalytic
system, we chose two methods (A and B). For method A,
the coupling of 4-bromoacetophenone (2b) with phenyl-
boronic acid (3a) was used as a model Suzuki reaction.
2k
Cl
c
10
15
9
–
2l
a Reaction conditions: ArX (2 mmol), NaBPh4 (0.6 mmol), NaOH (4
For method B, different substrates including low activity mmol), Pd(OAc)2 (0.01 mmol), PEG-2000–H2O (3.5 g/3 mL), 110 °C
(bath temperature).
substrates were tested in the same catalytic system. As
shown in Table 4, we were gratified to observe that the
Pd(OAc)2/1/PEG-2000 system could be reused six times
b Isolated yield.
c Catalyst loading: 3.0 mmol%.
for Suzuki reaction (Table 4, method A). Furthermore, no
Pd black emerged until the sixth run in method A. In
method B, the system could be reused five times using
In summary, we have ligated a dipyridyl ligand to a PEG
support and have demonstrated its utility in palladium-
different substrates without product contamination. In
catalyzed Suzuki and Suzuki-type reactions in PEG and
both methods, even though TON was similar, the TOF
aqueous media. In combination with a palladium source,
ligand 1 forms an active resin-bound catalyst for Suzuki
and Suzuki-type reactions, allowing for simplified prod-
uct separation and purification. A number of aryl halides,
values decreased in the last two runs. It indicated that the
catalytic efficiency of the system was decreased. Unfortu-
nately, for Suzuki-type reaction, the system could be only
reused for two runs with 99% and 93% yields using 1b
including aryl bromides and chlorides were coupled to
and NaBPh4 as substrates because Pd black was observed
arylboronic acids or sodium tetraphenylborate smoothly
in the second run.
Synlett 2006, No. 16, 2553–2558 © Thieme Stuttgart · New York

LETTER
PEG-Supported Dipyridyl Ligand for Palladium-Catalyzed Suzuki Reactions
2557
Table 4 Reuse of the Pd(OAc)2/1/PEG for the Suzuki Reactiona
Run
1
2
3
4
5
6
(A) Substrates
Yield (%)c
TON
2b + 3a
98
2b + 3a
98
2b + 3a
96
2b + 3a
95
2b + 3a
92b
2b + 3a
95b
475
18
–
490
27
490
27
480
26.6
2d + 3d
93d
475
26
460
19
TOF (h–1)
(B) Substrates
Yield (%)c
TON
2a + 3a
91d
2b + 3d
96d
2g + 3a
94b
2d + 3a
86b
–
455
30
480
32
465
31
470
20
430
18
–
TOF (h–1)
–
a Unless otherwise indicated, the reaction conditions were as follows: 2 (2 mmol), 3 (2.2 mmol), Pd(OAc)2/1 (1:1, 0.004 mmol), K2CO3
(4 mmol) in PEG-2000 (3 g) at 110 °C for 18 h.
b Reaction time was 24 h.
c Isolated yield.
d Reaction time was 15 h.
Preparation of PEG-Supported Dipyridyl Ligand (1)
and efficiently. Furthermore, the Pd(OAc)2/1/PEG-2000
system could be recycled and reused five to six times
without obvious loss of catalytic activity for Suzuki reac-
tion. Further efforts to extend the application of the
system in other Pd-catalyzed reactions are in progress in
our laboratory.
Bis(2-pyridyl)methanol (0.518 g, 2.78 mmol) was dissolved in an-
hyd THF (50 mL). To this solution was added NaH (0.12 g, 5.0
mmol), and the resulting mixture was stirred for 1 h, after which
dimesyl PEG (1 g, 0.464 mmol) was added. The solution was re-
fluxed for 24 h, and THF was evaporated under reduced pressure.
The brown residue was redissolved in a minimal amount of water
and extracted with CH2Cl2 (3 × 50 mL). The organic layers were
combined, dried over Na2SO4 and their volume was reduced by
95% under reduced pressure. The remaining CH2Cl2 was cooled to
0 °C, and anhyd Et2O (100 mL) was slowly added with stirring. Yel-
low crystals were formed and filtered after 1 h. Yield: 0.66 g (61%)
by 1H NMR.
1H NMR (600 MHz, CDCl3): d = 8.55 (d, J = 4.8 Hz, 4 H), 7.69 (m,
4 H), 7.60 (d, J = 7.8 Hz, 4 H), 7.18–7.16 (m, 4 H), 5.66 (s, 2 H),
3.60–3.73 (m, 302 H).
13C NMR (150 MHz, CDCl3): d = 160.31, 149.18, 136.67, 122.49,
121.47, 85.95, 70.53, 68.93.
Synthesis of Bis(2-pyridyl)methanol
To a stirred anhyd Et2O (200 mL) solution of 2-bromopyridine (9.5
mL, 100 mmol) was added n-BuLi (62.5 mL, 100 mmol, 1.6 M in
hexane) at –78 °C under a N2 atmosphere. After being stirred for 20
min, the reaction was quenched with 2-pyridinecarboxaldehyde (9.5
mL, 100 mol) at the same temperature. The whole mixture was
stirred for 30 min. After the cooling bath was removed, the mixture
was diluted with 2 M HCl (160 mL) and then solid NaOH was add-
ed until a pH of ca. 8 was reached. The mixture was extracted with
Et2O (3 × 200 mL) and the organic layer was washed with brine and
dried over MgSO4. Solvent was removed under reduced pressure,
and the residual mixture was purified by flash chromatography on
silica gel (petroleum ether–EtOAc) to afford the product (14 g,
75%).
Suzuki Reaction; General Procedure
A mixture of aryl halides 2 (2 mmol), arylboronic acid 3 (2.2
mmol), Pd(OAc)2/1 (1:1, 0.004 mmol), K2CO3 (4 mmol), and PEG-
2000 (3 g) was added to a flask and stirred at 110 °C in open air for
the desired time until complete consumption of the starting sub-
strates as judged by TLC. After the mixture was extracted with an-
hyd Et2O (3 × 30 mL) and evaporated, the residue was purified by
flash column chromatography (petroleum ether or petroleum ether–
EtOAc) to afford the desired coupled products 4–16.
1H NMR (600 MHz, CDCl3): d = 8.56 (d, J = 4.8 Hz, 2 H), 7.66 (td,
J = 1.8, 6.0 Hz, 2 H), 7.54 (d, J = 7.8 Hz, 2 H), 7.19 (d, J = 7.2 Hz,
2 H), 5.90 (s, 1 H).
Mesylation of PEG-2000
Selected data for 5: 1H NMR (400 MHz, CDCl3): d = 8.04 (d, J =
8.4 Hz, 2 H), 7.70 (d, J = 8.4 Hz, 2 H), 7.64 (d, J = 7.2 Hz, 2 H),
7.49 (t, J = 7.2 Hz, 2 H), 7.42 (t, J = 7.2 Hz, 1 H), 2.64 (s, 3 H).
13C NMR (150 MHz, CDCl3): d = 197.74, 145.77, 139.86, 135.84,
128.94, 128.90, 128.22, 127.26, 127.21, 26.66.
PEG-2000 (4 g, 2 mmol) was dried under vacuum at 80 °C for 1 h
and then dissolved in anhyd CH2Cl2 (100 mL). Trioctylamine (3.5
mL, 8 mmol) was added, and the mixture was cooled to 0 °C with
stirring. Mesyl chloride (0.93 mL, 12 mmol) was added slowly, and
the mixture was stirred for 24 h at r.t. The CH2Cl2 volume was then
reduced by 95% under reduced pressure. The remaining CH2Cl2
was cooled to 0 °C, and anhyd Et2O (100 mL) was slowly added
with stirring. After 1 h a white solid (4.18 g, 97% yield) was ob-
tained by filtration and washed with Et2O (2 × 25 mL).
1H NMR (600 MHz, CDCl3): d = 4.39 (t, J = 4.8 Hz, 4 H), 3.63–3.77
(m, 184 H), 3.09 (s, 6 H).
13C NMR (150 MHz, CDCl3): d = 70.51, 69.24, 68.96, 37.68.
Suzuki-Type Reaction; General Procedure
A mixture of aryl halides 2 (2 mmol), NaBPh4 (0.6 mmol),
Pd(OAc)2/1 (1:1, 0.01 mmol), NaOH (4 mmol), PEG-2000 (3.5 g),
and H2O (3 mL) was added to a flask and stirred at 110 °C in open
air for the desired time until complete consumption of the starting
substrates as judged by TLC. After the mixture was extracted with
Synlett 2006, No. 16, 2553–2558 © Thieme Stuttgart · New York

2558
W. Mai, L. Gao
LETTER
(5) Zapf, A.; Beller, M. Chem. Eur. J. 2000, 6, 1830.
(6) Li, G. Y. Angew. Chem. Int. Ed. 2001, 40, 1513.
(7) (a) Homogeneous Catalysis with Metal Phosphine
Complexes; Pignolet, L. H., Ed.; Plenum: New York, 1983.
(b) Parshall, G. W.; Ittel, S. Homogeneous Catalysis; Wiley
and Sons: New York, 1992.
(8) (a) Okamoto, K.; Akiyama, R.; Kobayashi, S. Org. Lett.
2004, 6, 1987. (b) an der Heiden, M.; Plenio, H. Chem. Eur.
J. 2004, 10, 1789. (c) Kim, N.; Kwon, M. S.; Park, C. M.;
Park, J. Tetrahedron Lett. 2004, 45, 7057.
anhyd Et2O (3 × 30 mL) and evaporated, the residue was purified by
flash column chromatography (petroleum ether or petroleum ether–
EtOAc) to afford the desired coupled products 4–10.
Selected data for 6: 1H NMR (400 MHz, CDCl3): d = 10.06 (s, 1 H),
7.96 (d, J = 8.4 Hz, 2 H), 7.76 (d, J = 8.4 Hz, 2 H), 7.65 (d, J = 7.2
Hz, 2 H), 7.49 (t, J = 7.2 Hz, 2 H), 7.41–7.44 (m, 1 H).
13C NMR (150 MHz, CDCl3): d = 191.86, 147.12, 139.65, 135.14,
130.21, 128.96, 128.42, 127.62, 127.31.
Recovery and Reuse of the System for the Suzuki or Suzuki-
Type Reactions; General Procedure
(9) (a) Welton, T. Chem. Rev. 1999, 99, 2071.
(b) Wasserscheid, P.; Keim, W. Angew. Chem. Int. Ed. 2000,
39, 3772. (c) Sheldon, R. Chem. Commun. 2001, 2399.
(d) Earle, M. J.; Seddon, K. R. Pure Appl. Chem. 2000, 72,
1391.
After extracting with Et2O, the mixture of Pd(OAc)2/1/PEG-2000 or
Pd(OAc)2/1/PEG-2000–H2O was cooled and then evaporated under
reduced pressure and subjected to a second run of the Suzuki or
Suzuki-type reactions by charging with the same substrates or
different substrates.
(10) (a) Boon, J. A.; Levisky, J. A.; Pflug, J. L.; Wilkes, J. S. J.
Org. Chem. 1986, 51, 480. (b) Brown, R. A.; Pollet, P.;
McKoon, E.; Eckert, C. A.; Liotta, C. L.; Jessop, P. G. J. Am.
Chem. Soc. 2001, 123, 1254. (c) Chauvin, Y.; Mussmann,
L.; Olivier, H. Angew. Chem., Int. Ed. Engl. 1995, 34, 2698.
(d) Favre, F.; Olivier-Bourbigou, H.; Commereuc, D.;
Saussine, L. Chem. Commun. 2001, 1360. (e) Adams, C. J.;
Earle, M. J.; Roberts, G.; Seddon, K. R. Chem. Commun.
1998, 2097. (f) Song, C. E.; Shim, W. H.; Roh, E. J.; Lee, S.;
Choi, J. H. Chem. Commun. 2001, 1122. (g) Xu, L.; Chen,
W.; Xiao, J. Organometallics 2000, 19, 1123. (h) Handy, S.
T.; Zhang, X. L. Org. Lett. 2001, 3, 233. (i) Adams, C. J.;
Earle, M. J.; Seddon, K. R. Chem. Commun. 1999, 1043.
(j) Jiang, T.; Gao, H. X.; Han, B. X.; Zhao, G. Y.; Chang, Y.
H.; Wu, W. Z.; Gao, L.; Yang, G. Y. Tetrahedron Lett. 2004,
45, 2699.
References
(1) Selected recent reviews: (a) Miyaura, N. Top. Curr. Chem.
2002, 219, 11. (b) Kotha, S.; Kashinath, D. Tetrahedron
2002, 58, 9633. (c) Bellina, F.; Carpita, A.; Rossi, R.
Synthesis 2004, 2419. (d) Hassan, J.; Sevignon, M.; Gozzi,
C.; Schulz, E.; Lemaire, M. Chem. Rev. 2002, 102, 1359.
(e) Littke, A. F.; Fu, G. C. Angew. Chem. Int. Ed. 2002, 41,
4176.
(2) (a) Wang, W.; Xiong, C.; Yang, J.; Hruby, V. J. Tetrahedron
Lett. 2001, 42, 7717. (b) Vaz, B.; Rosana, R.; Nieto, M.;
Paniello, A. I.; de Lera, A. R. Tetrahedron Lett. 2001, 42,
7409. (c) Schomaker, J. M.; Delia, T. J. J. Org. Chem. 2001,
66, 7125. (d) Wong, K.-T.; Huang, T. S.; Lin, Y.; Wu, C.-C.;
Lee, G.-H.; Peng, S.-M.; Chou, C. H.; Su, Y. O. Org. Lett.
2002, 4, 513.
(11) Polyethylene Glycol Chemistry: Biotechnological and
Biomedical Applications; Harris, J. M., Ed.; Plenum: New
York, 1992.
(12) (a) Bergbreiter, D. E. Chem. Rev. 2002, 102, 3345.
(b) Bergbreiter, D. E.; Li, C. Org Lett. 2003, 5, 2445.
(c) Dickerson, T. J.; Need, N. N.; Janda, K. D. Chem. Rev.
2002, 102, 3325. (d) Gravert, D. J.; Janda, K. D. Chem. Rev.
1997, 97, 489.
(13) (a) Chandrasehar, S.; Narsihmulu, C.; Sultana, S. S.; Reddy,
N. R. Org. Lett. 2002, 4, 4399. (b) Wang, L.; Zhang, Y. H.;
Liu, L. F.; Wang, Y. G. J. Org. Chem. 2006, 71, 1284.
(c) Heldebrant, D. J.; Jessop, P. G. J. Am. Chem. Soc. 2003,
125, 5600. (d) Li, J. H.; Zhu, Q. M.; Liang, Y.; Yang, D. J.
Org. Chem. 2005, 70, 5347. (e) Chandrasekhar, S.; Sultana,
S. S.; Yaragorla, S. R.; Reddy, N. R. Synthesis 2006, 839.
(14) Li, J. H.; Liu, W. J.; Xie, Y. X. J. Org. Chem. 2005, 70, 5409.
(15) Corma, A.; Carcía, H.; Leyva, A. J. Catal. 2006, 240, 87.
(16) Wu, X. E.; Ma, L.; Ding, M. X.; Gao, L. X. Chem. Lett.
2005, 34, 312.
(3) (a) Hobbs, P. D.; Upender, V.; Dawson, M. I. Synlett 1997,
965. (b) Nicolaou, K. C.; Li, H.; Boddy, C. N. C.;
Ramanjulu, J. M.; Yue, T.-Y.; Natarajan, S.; Chu, X.-J.;
Brase, S.; Rubsam, F. Chem. Eur. J. 1999, 5, 2584.
(c) Nicolaou, K. C.; Koumbis, A. E.; Takayanagi, M.;
Natarajan, S.; Jain, N. F.; Bando, T.; Li, H.; Hughes, R.
Chem. Eur. J. 1999, 5, 2622. (d) Kamikawa, K.; Watanabe,
T.; Daimon, A.; Uemura, M. Tetrahedron 2000, 56, 2325.
(4) (a) Wolfe, J. P.; Singer, R. A.; Yang, B. H.; Buchwald, S. L.
J. Am. Chem. Soc. 1999, 121, 9550. (b) Bei, X.; Turner, H.
W.; Weinberg, W. H.; Guram, A. S.; Petersen, J. L. J. Org.
Chem. 1999, 64, 6797. (c) Zapf, A.; Ehrentraut, A.; Beller,
M. Angew. Chem. Int. Ed. 2000, 22, 4153. (d) Littke, A. F.;
Dai, C.; Fu, G. C. J. Am. Chem. Soc. 2000, 122, 4020.
(e) Feuerstein, M.; Laurenti, D.; Bougeant, C.; Doucet, H.;
Santelli, M. Chem. Commun. 2001, 325. (f) Pickett, T. E.;
Richards, C. J. Tetrahedron Lett. 2001, 42, 3767.
(17) (a) Benaglia, M.; Cinquini, M.; Cozzi, F. Tetrahedron Lett.
1999, 40, 2019. (b) Annunziata, R.; Benaglia, M.; Cinquini,
M.; Cozzi, F. Chem. Eur. J. 2000, 6, 133.
(18) Bumagin, N. A.; Bykov, V. V. Tetrahedron 1997, 53, 14437.
(19) Lu, G.; Franzén, R.; Zhang, Q.; Xu, Y. J. Tetrahedron Lett.
2005, 46, 4255.
(g) Feuerstein, M.; Doucet, H.; Santelli, M. Synlett 2001,
1458. (h) Liu, S.-Y.; Choi, M. J.; Fu, G. C. Chem. Commun.
2001, 2408. (i) Kudo, N.; Perseghini, M.; Fu, G. C. Angew.
Chem. Int. Ed. 2006, 45, 1282. (j) Anderson, K.; Buchwald,
S. L. Angew. Chem. Int. Ed. 2005, 44, 6173. (k) Willis, M.
C.; Powell, L. H.; Claverie, C. K. Angew. Chem. Int. Ed.
2004, 43, 1249. (l) Colacot, T. J.; Shea, H. A. Org. Lett.
2004, 6, 3731. (m) Barder, T. E.; Walker, S. D.; Martinelli,
J. R.; Buchwald, S. L. J. Am. Chem. Soc. 2005, 127, 4685.
(20) Liu, L. F.; Zhang, Y. H.; Wang, Y. G. J. Org. Chem. 2005,
70, 6122.
Synlett 2006, No. 16, 2553–2558 © Thieme Stuttgart · New York