Preparation of polystyrene-supported soluble palladacycle catalyst for Heck and Suzuki reactions

Article abstract of DOI:10.1016/j.tet.2005.04.036

A polystyrene-supported palladium complex soluble in tetrahydrofuran and N,N-dimethylacetamide and precipitated in diethyl ether or acetonitrile was prepared from two routes as an excellent and recyclable palladacycle catalyst for carbon-carbon bond formation in Heck and Suzuki reactions to give high yields of the desired products.

Full text of DOI:10.1016/j.tet.2005.04.036

Tetrahedron 61 (2005) 6040–6045
Preparation of polystyrene-supported soluble palladacycle
catalyst for Heck and Suzuki reactions
a,b
Fen-Tair Luo,a, Cuihua Xue, Sheng-Li Ko,a Yu-Der Shao,c Chien-Jung Wua
*
and Yang-Ming Kuoc
aInstitute of Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan
bThe Faculty of Chemistry, Sichuan University, Chengdu 610064, China
cInstitute of Applied Chemistry, Chinese Culture University, Taipei 111, Taiwan
Received 26 January 2005; revised 19 April 2005; accepted 20 April 2005
Available online 17 May 2005
Abstract—A polystyrene-supported palladium complex soluble in tetrahydrofuran and N,N-dimethylacetamide and precipitated in diethyl
ether or acetonitrile was prepared from two routes as an excellent and recyclable palladacycle catalyst for carbon–carbon bond formation in
Heck and Suzuki reactions to give high yields of the desired products.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
reactivity to promote a lot of reactions, only a few reports on
the recovery of palladacycle catalysts were reported in the
literature.17–23 In addition, phosphorus-containing poly-
styrene was generally used as the ligand to trap and reuse Pd
catalysts after the reaction.24–30 In this paper, we sum-
marized two synthetic routes for the synthesis of a
polystyrene-supported palladacycle catalyst 2 which can
be used as an efficient recyclable palladium catalyst for
running Heck-Mizoroki and Suzuki-Miyaura reaction.31
The advantage of using soluble polymers to recover
catalysts and ligands has its origins in the synthetic
approaches to peptide and oligonucleotide synthesis that
were developed in the labs of Merrifield and Letsinger in the
1960s.1,2 Although soluble polymers were common 40 years
ago, but they did not receive as much attention for using as
catalyst supports as was the case for their cross-linked,
insoluble analogues. However, the uses of soluble polymer
systems have substantially expanded in recent years due to
the point that soluble polymers are no longer uncommon as
supports for catalysts and ligands.3–5 On the other hand,
palladacycles have been known for over 20 years; yet they
have been used as catalysts recently.6–10 Nitrogen-,
phosphorus-, and sulfur-containing palladacycles are
emerging as a new family of palladium catalyst precursors,
and they have recently, become the most simple and
efficient catalyst in applying to Heck-Mizoroki, Suzuki-
Miyaura and Sonogashira reactions.11 Herrmann and his
co-workers have demonstrated that Herrmann’s pallada-
cycle catalyst 1 is thermally stable and efficient catalyst for
Heck-Mizoroki, Suzuki-Miyaura, and Sonogashira reac-
tions.12–15 It also had been shown to have high reactivity
toward arylation of olefins with aryl chlorides.16 Although
the palladacycle catalyst, as Herrmann reported, have high
2. Results and discussion
Keywords: Supported catalyst; Heck reaction; Suzuki reaction; Recyclable
catalyst; Polystyrene-bound catalyst; Palladacycle catalyst.
The two synthetic routes of the polystyrene-supported
palladacycle catalyst are shown in Scheme 1. In the first
*
Corresponding author. Tel.: C886 2 27898576; fax: C886 2 27888199;
e-mail: luoft@chem.sinica.edu.tw
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.04.036

F.-T. Luo et al. / Tetrahedron 61 (2005) 6040–6045
6041
Scheme 1. Two routes for the synthesis of polystyrene-supported pallacycle catalyst 2.
route, trans-di(m-acetato)-bis[2-(diphenylphosphino)-4-
vinylbenzyl]dipalladium(II) 4 was synthesized from
3-(diphenylphosphino)-4-methylstyrene 3 by heating with
palladium acetate in toluene at 50 8C.32 Compound 3 was
prepared in moderate yield by bromination (Br2/AlCl3)33 of
4-methylaceto-phenone followed by the reduction (LAH/
ether), dehydration (KHSO4)34 and coupling with chloro-
diphenylphosphine (Mg/THF; ClPPh2).35 Considering the
proper space around the palladium in the catalyst, the
palladacycle precursor 4 was copolymerized with 6 equiv of
styrene at 70 8C (Route 1) to give polystyrene-supported
palladacycle catalyst 2. Alternatively, the phosphine-con-
taining monomer 3 was copolymerized with 6 equiv of
styrene at 70 8C to form the phosphine-bound polystyrene 5,
which was then heating with Pd(II) acetate in toluene at
50 8C (Route 2) to form polystyrene-supported palladacycle
peak at 53 ppm in 31P NMR spectrum became the sole peak
after six times recycling of the catalyst 4. Thus, the catalyst
4 was polymerized completely under the reaction con-
ditions. On the other hand, the chemical shift of phosphorus
in 5 appeared at K12 ppm as a singlet. Gel permeation
chromatography analysis (mobile phase: THF, polystyrene
standards) indicated that Mw of catalyst 2 prepared from
Route 1 and Route 2 was 1.434!104 and 1.529!104 g/mol,
respectively. Atomic absorption spectrophotometer analysis
showed that palladium was containing at 86.39 and
82.91 mg of Pd per gram of 2 prepared from Route 1 and
Route 2, respectively.
To test the applicability of polystyrene-supported pallada-
cycle catalyst 2 obtained from the above two routes, we
examined the Heck reaction of methyl acrylate and various
aryl halide in the presence of NaOAc in N,N-dimethyl-
acetamide as shown in Table 1. Under various reaction
conditions, all the desired products were isolated in more
than 90% yields. Thus, the polystyrene-supported catalyst 2
can easily promote the Heck reaction of aryl bromides- and
iodides-containing with either electron-rich or electron-
withdrawing group (Eq. 1), which produced only one major
product as determined from GC and crude 1H NMR spectral
analysis. The polystyrene-supported catalyst 2 prepared
with other ratio of styrene (mole ratio of styrene/4Z3 and 9)
were also synthesized and were run as the catalyst in the
above Heck reaction. Gel permeation chromatography
analysis (mobile phase: THF, polystyrene standards)
indicated that Mw of catalyst 2 prepared from mole
ratio of styrene/4Z3 and 9 was 1.126!104 and 1.578!
104 g/mol, respectively. No obvious difference was
observed in the results of the above Heck reaction among
these polystyrene-supported catalysts prepared from
different ratio of styrene/4. Thus, the reactivity of catalyst
catalyst 2. The exterior deep dark brown color and their 31
P
NMR and 1H NMR spectral data are the same for the
catalyst 2 obtained from Route 1 and Route 2. The total
yields for two routes via 4 and 5 for the preparation of
polystyrene-supported palladacycle catalyst 2 were 21 and
18%, respectively, on the basis of atomic absorption
analysis of palladium in 2. The phosphorous-containing
compounds were analyzed by solution phase 31P NMR in
CDCl3. The chemical shift of phosphous in 3 appeared at
K12 ppm as a singlet, while it was shifted to 17 ppm as a
singlet in 4. On the other hand, the methyl protons in 3
appeared at 2.36 ppm as a singlet, while the methylene
1
protons in 4 appeared at 3.63 ppm as a broad singlet in H
NMR spectrum. The signal of catalyst 2 in 31P NMR
spectrum was observed at 53 ppm before and after Heck
reaction, while the signal of catalyst 4 in 31P NMR spectrum
observed at 17 ppm before Heck reaction but appeared at
17 ppm along with a new peak at 53 ppm after Heck
reaction (the peaks ratio at 17 and 53 ppm is about 7:3). The

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F.-T. Luo et al. / Tetrahedron 61 (2005) 6040–6045
Table 1. Heck reaction of using polystyrene-supported catalyst 2
Entry
Haloarene
Catalyst 2 (equiv)
Temp (8C)
Time (h)
Iso. Yield (%)
Route 1
Route 2
1
2
3
4
5
6
Iodobenzene
Bromobenzene
4-Bromotoluene
0.02
0.05
0.05
0.05
0.002
0.02
100
130
130
130
100
100
8
O99
97
95
92
O99
O99
99
98
93
92
99
98
48
48
48
10
10
4-Bromoanisole
2-Bromobenzaldehyde
4-Bromobenzonitrile
2 was proved to be similar to Herrmann’s palladacycle
catalyst 1. Furthermore, we also found that the reactivity of
polystyrene-supported palladacycle catalyst 2 obtained
from two different precursors were similar to each other
based on the yields of the above model Heck reaction,
although the catalyst 2 obtained from Route 2 gave a little
lower yields than that from Route 1.
model reaction. We also found that the yield can be kept
more than 99% after recycling 6 times, using Et3N instead
1
of NaOAc as the base in the model Heck reaction. The H
NMR and IR spectra of the recycled palladium catalysts
showed no difference before and after recycling five times.
The elemental analysis for the repeating unit
(C142H138O4P2Pd) in the polystyrene-supported palladium
catalyst found C, 82.12G0.5% and H, 6.70G0.5%
before and after recycling one to three times clearly
indicated the composition of the copolymer. Atomic
absorption spectrophotometer analysis showed that
palladium was containing at 85.43, 80.78, 74.13 mg of Pd
per gram of polymer after recycling one to three times,
respectively.
The polystyrene-supported catalyst 2 was soluble in
tetrahydrofuran, N,N-dimethylacetamide, N,N-dimethylfor-
mamide, toluene, chloroform, dichloromethane and not very
soluble in methanol, acetonitrile, hexane, and diethyl ether.
Diethyl ether and acetonitrile were used here, to precipitate
our new catalyst 2. Salt removal was skipped due to the
palladacycle catalyst, which can be deactivated easily by
water. Probably, the phosphine ligand may form phosphine
oxide in the presence of water. The Heck reaction of
4-bromobenzonitrile and methyl acrylate (1.5 equiv) with
2 mol% of catalyst 2 and NaOAc (1.5 equiv) in N,N-
dimethylacetamide at 100 8C was proceeded as the model
reaction. The results showed that the yield of the product
can be isolated more than 80% after recycled four times
with diethyl ether as the solvent to precipitate our
polystyrene-supported catalyst 2. Using acetonitrile as the
solvent may drop the yield of the product below 60% after
the 2nd run. The reactivity of Herrmann’s catalyst 1
diminished thoroughly after recycled two times in the
We also tested the applicability of catalyst 2 in Suzuki-
Miyaura cross-coupling reaction. Thus, the cross-coupling
of 2,5-dihexyloxy-1,4-benzenediboronic acid, prepared in
79% yield from the lithium–halogen exchange reaction of
2,5-dibromo-1,4-dihexyloxybenzene with n-butyllithium
followed by the treatment of trimethylborate and dilute
acid (2 N HCl), with 2.5 equiv of bromoarene with or
without cyano groups at o-, m-, or p-positions in the
presence K2CO3 as the base and catalyst 2, prepared from
Route 1 and Route 2, in o-xylene could give p-terphenyls in
fair to good yields (72 to 88%) as shown in Table 2. The
results showed that the activities of the catalyst 2 prepared
Table 2. Suzuki reaction of using polystyrene-supported catalyst 2
Entry
Haloarene
Iso. Yield (%)
Route 1
Route 2
1
2
3
4
Bromobenzene
85
72
74
76
88
78
83
84
2-Bromobenzenecarbonitrile
3-Bromobenzenecarbonitrile
4-Bromobenzenecarbonitrile

F.-T. Luo et al. / Tetrahedron 61 (2005) 6040–6045
6043
from Route 1 and Route 2 were similar. Attempts to change
the base as Et3N or other solid bases (K3PO4, Cs2CO3) in the
above Suzuki-Miyaura cross-coupling reaction gave very
low yields (!20%).
of 3-bromo-4-methylacetophenone (38 g, 180 mmol) in dry
ether (50 mL) was injected into the flask dropwisely.
Stirring was continued after the completion of addition of
3-bromo-4-methylacetophenone until no more gas was
generated. The mixture was poured into 2 N HCl aqueous
solution (240 mL), extracted with EAC (4!30 mL),
washed over saturated NH4Cl aqueous solution (50 mL),
dried over anhydrous MgSO4, and concentrated at low
pressure. The crude product was further purified by
distillation at low pressure [130 8C (4 mm Hg)] to give
31.35 g (81% yield) of the desired product as clear and pale
3. Conclusion
We have synthesized via two routes in six steps with high
yields to a new polystyrene-supported palladacycle catalyst
2 which was successfully employed in the carbon–carbon
bond formation to give good yields in the Heck-Mizoroki
and Suzuki-Miyaura model studies. The simple precipi-
tation and filtration process to recycle the catalyst after our
model reactions for these reactions were noteworthy. Our
catalyst exhibited a high reactivity as Herrmann’s pallada-
cycle catalyst and, in addition, to its high reactivity, it gave
us a promising solution to lower the reaction cost by its good
recyclabilities in Heck-Mizoroki reaction of using pertinent
organic bases.
1
yellow liquid. H NMR (300 MHz, CDCl3) d 1.47 (t, JZ
6.4 Hz, 3H), 1.76 (s, 1H), 2.38 (s, 3H), 4.84 (q, JZ6.4 Hz,
1H), 7.20 (s, 2H), 7.55 (s, 1H); 13C NMR (75 MHz, CDCl3)
d 22.54, 25.16, 69.33, 124.30, 124.93, 129.34, 130.82,
136.88, 145.27; IR (neat) 3024, 2997, 2927, 1605, 1562,
1494, 1452, 1381, 1331, 1255, 1091, 1038, 1009, 908, 822,
733 cmK1; MS m/z 214 (MC), 199, 197, 171, 169, 119, 91;
HRMS calcd for C9H11OBr: 213.9993, found: 213.9995.
4.1.3. Synthesis of 3-bromo-4-methyl-styrene. KHSO4
(0.55 g, 34 mmol), hydroquinone (0.142 g, 1.3 mmol), and
1-(3-bromo-4-methyl-phenyl)ethanol (17.2 g, 80 mmol)
were delivered into a 25 mL round bottomed flask, equipped
with a distillation equipment. The mixture was kept stirring.
The system was vacuumed at 3 mm Hg. The dehydration
and distillation processes [102 8C (3 mm Hg)] were pro-
ceeded at the same time. The isolated product was obtained
in 13.6 g (86% yield) as clear and golden yellow liquid. 1H
NMR (300 MHz, CDCl3) d 2.37 (s, 3H), 5.23 (d, JZ
10.9 Hz, 1H), 5.69 (d, JZ17.6 Hz, 1H), 6.60 (dd, JZ10.9,
17.6 Hz, 1H), 7.16 (d, JZ7.8 Hz, 1H), 7.21 (d, JZ7.8 Hz,
1H), 7.57 (s, 1H); 13C NMR (75 MHz, CDCl3) d 22.63,
114.32, 125.04, 125.09, 129.92, 130.76, 135.30, 137.11,
137.22 ppm; IR (neat) 3091, 3063, 3016, 2985, 2964, 1899,
1833, 1701, 1629, 1602, 1554, 1492, 1450, 1380, 1304,
1278, 1205, 1037, 989, 914, 833, 854, 826 cmK1; MS m/z
197 (MCC1) 171, 169, 117, 115, 91, 89; HRMS calcd for
C9H9Br: 195.9888, found: 195.9887.
4. Experimental
4.1. General
4.1.1. Synthesis of 3-bromo-4-methylacetophenone.
Anhydrous aluminum chloride (30 g, 225 mmol) and one
magnetic stirrer bar were put into a 100 mL of two necked
round bottomed flask equipped with one septum at one neck
and a pressure-equalizer dropping funnel at the other neck.
Then, the flask was flushed with nitrogen through the
septum. 4-Methylacetophenone (13.3 mL, 100 mmol) was
added slowly from the dropping funnel to the stirred solid
over a period of 10 min. The flask was stirred continuously
for another 30 min after completion of the addition.
Bromine (5.7 mL, 110 mmol) was added, dropwise, to the
stirred, molten mass over a period of 5 min. The reaction
was completed when the stirred mass solidified and no more
hydrogen bromide was emitted. The solidified mass was
dropped, portionwise, into 3 N HCl aqueous solution
(250 mL). The dark oil at the bottom of the solution was
extracted by ether (3!30 mL). The organic layer was then
washed by saturated NH4Cl aqueous solution (50 mL), dried
over with MgSO4, and concentrated to get the crude
product. The crude product was further purified by
distillation at low pressure [118 8C (3 mm Hg)] to give
18.53 g (87% yield) of the desired product. Mp 38–40 8C;
1H NMR (300 MHz, CDCl3) d 2.46 (s, 3H), 2.58 (s, 3H),
7.33 (d, JZ4.7 Hz, 1H), 7.79 (dd, JZ4.7, 0.99 Hz, 1H),
8.12 (d, JZ0.99 Hz, 1H); 13C NMR (75 MHz, CDCl3) d
23.19, 26.52, 123.21, 127.08, 130.87, 132.32, 136.46,
143.53, 196.4; IR (neat) 3024, 1684, 1599, 1383, 1521,
1039, 958, 907, 831 cmK1; MS m/z 212 (MC), 199, 197,
171, 169, 89; HRMS calcd for C9H9OBr: 211.9837, found:
211.9840.
4.1.4. Synthesis of 3-(diphenylphosphino)-4-methyl-
styrene 3. Mg (0.72 g, 30 mmol) was added into a 50 mL
of round bottomed flask, which was dried and filled with
nitrogen. Dry THF (10 mL) was injected first and then
stirred with Mg. Half mixture of 3-bromo-4-methyl-styrene
(3.94 g, 20 mmol) in dry THF (10 mL) was injected
dropwisely. After an exothermic reaction starts, the rest of
the mixture was injected. The Grignard reagent was
reversely added into the mixture of chlorodiphenyl-
phosphine (5.25 g, 25 mmol) in dry THF (10 mL) at 0 8C.
After completion of the addition, the temperature was raised
to the room temperature. After stirring for another 20 h, the
mixture was poured into a saturated NH4Cl aqueous
solution (10 mL) at 0 8C and extracted with dry THF (3!
20 mL). The organic layer was dried over anhydrous
MgSO4 and concentrated to 5 mL only. Hexane was
added into the organic solution to deposit the by-products.
After filtration and concentration, the residue was purified
by a flash column chromatography (hexane/EACZ4:1).
The isolated product was 2.42 g (39% yield). Mp 48–49 8C.
1H NMR (300 MHz, CDCl3) d 2.36 (s, 3H), 5.06 (d, JZ
10.9 Hz, 1H), 5.42 (d, JZ17.6 Hz, 1H), 6.48 (q, JZ10.9,
17.6 Hz, 1H), 6.79 (q, JZ2.1, 5.8 Hz, 1H), 7.20–7.34 (m,
4.1.2. Synthesis of 1-(3-bromo-4-methyl-phenyl)ethanol.
LAH (6.45 g, 170 mmol) and one magnetic stirrer bar were
added into a 250 mL of round bottomed flask, which was
then closed with one septum and dried under vacuum
followed by filling with nitrogen. One part of dry ether
(50 mL) was first injected into the stirred LAH. The mixture

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F.-T. Luo et al. / Tetrahedron 61 (2005) 6040–6045
11H); 13C NMR (75 MHz, CDCl3) d 20.8, 21.1, 113.0,
126.2, 128.5, 128.6, 128.8, 130.2, 130.3, 130.7, 133.9,
134.1, 135.1, 136.0, 136.3, 136.5, 141.7 ppm; 31P NMR
(121 MHz, CDCl3) d K12.34 ppm; IR (neat) 3057, 3016,
2974, 1957, 1900, 1819, 1629, 1589, 1479, 1435, 1380,
1306, 1262, 1179, 1152, 1093, 1028, 992, 911, 830,
699 cmK1; MS m/z 302 (MC) 223, 183, 165, 152, 115,
78; HRMS calcd for C21H19P: 302.1224, found: 302.1227.
chromatography analysis (mobile phase: THF, polystyrene
standards) indicated that Mw of catalyst 2 prepared from
Route 1 and Route 2 was 1.434!104 and 1.529!104 g/mol,
respectively. Atomic absorption spectrophotometer analysis
showed that palladium was containing at 86.39 and
82.91 mg of Pd per gram of polymer prepared from Route
1 and Route 2, respectively.
4.1.8. Typical procedure for use of polystyrene-
supported palladacycle catalyst 2 in the Heck reaction.
Polystyrene-supported palladacycle catalyst 2 (30 mg,
24 mmol Pd), iodobenzene (0.20 g, 1 mmol), methyl
acrylate (0.13 g, 1.5 mmol), sodium acetate (0.12 g,
1.5 mmol), and N,N-dimethylacetamide (3 mL) were
sequentially added into a 15 mL septum-sealed test tube
under nitrogen atmosphere. The mixture was then heated at
100 8C for 8 h. After cooling to the room temperature, the
mixture was added 8 mL of dry ether to precipitate
the polystyrene-supported palladacycle catalyst. After the
catalyst was further precipitated by a centrifuge, the upper
liquid layer of the reaction mixture was transferred via a
syringe into another 20 mL round bottom flask. Repeat the
above precipitation procedure one more time. The com-
bined liquid layer was concentrated under reduced pressure.
Saturated ammonium chloride solution (5 mL) was then
added to the oil mixture. The organic product was extracted
three times by ethyl acetate (10 mL!3), dried over
magnesium sulfate, filtrated, and concentrated to give the
crude product. The crude product was further purified by
column chromatography (silica gel, hexane/EACZ4:1) to
give 0.16 g (99% yield) of trans-methyl cinnamate.36
4.1.5. Synthesis of trans-di(m-acetato)-bis[3-(diphenyl-
phosphino)-4-styryl]dipalladium (II) 4. Pd(OAc)2
(0.225 g, 1 mmol) was solvated in stirring dry toluene
(20 mL) in a 50 mL round bottomed flask. The mixture of
3-(diphenylphosphino)-4-methyl-styrene
3
(0.333 g,
1.1 mmol) and dry toluene (4 mL) was injected into the
flask. After that, the mixture was heated at 50 8C for 5 min,
and then cooled slowly to the room temperature. The
mixture was concentrated to one third of the original
volume. Hexane (25 mL) was added to the mixture for
precipitation of the product. The recrystallization was
proceeded repeatedly in the system of toluene/hexane or
dichloromethane/hexane. The isolated product was 0.34 g
1
(74% yield). H NMR (500 MHz, CDCl3) d 2.61 (s, 6H),
3.63 (br s, 4H), 5.06 (d, JZ11.1 Hz, 2H), 5.42 (d, JZ
17.6 Hz, 2H), 6.48 (q, JZ11.1, 17.6 Hz, 2H), 7.1–7.8 (m,
26H); 31P NMR (121 MHz, CDCl3) d 17.41 ppm. IR
(CHCl3) n 3058, 2921, 2860, 1653, 1561, 1435 cmK1
.
Anal. Calcd for C46H42O4P2Pd2: C, 59.18; H, 4.53. Found:
C, 59.33; H, 4.68.
4.1.6. Synthesis of phosphine-bound polystyrene 5.
3-(Diphenylphosphino)-4-methyl-styrene
3
(0.33 g,
1.1 mmol) was added to a test tube and flushed with
nitrogen. A mixture of styrene (0.68 g, 6.6 mmol) and
benzene (2 mL) was injected into the test tube. Then, a
mixture of AIBN (0.18 g, 0.1 mmol) and benzene (10 mL)
was injected into the stirring test tube. The reaction mixture
was then heated at 70 8C for 40 h. The mixture was
concentrated to dryness. The dry solid was repeatedly
washed by the solvent (THF/hexaneZ1:30). The isolated
polymer was 0.8 g (79% yield). 1H NMR (500 MHz,
CDCl3) d 1.1–1.7 (m, phenylCHCH2), 2.2–2.4 (br s, Ar-
CH3), 6.2–6.7 (m, Ar-H), 6.8–7.3 (m, Ar-H) ppm; 31P NMR
(121 MHz, CDCl3) d K12.23 ppm; IR (CHCl3) n 3023,
2924, 2846, 1653, 1561, 1492, 1452, 756, 699 cmK1. Anal.
Calcd for C69H68P (repeating unit): C, 89.28; H, 7.38.
Found: C, 89.60; H, 7.84.
4.1.9. Typical procedure for the use of polystyrene-
supported palladacycle catalyst 2 from Route 1 in the
Suzuki-Miyaura reaction for the preparation of 2,5-
dihexyloxy-1,4-di-phenylbenzene. o-Xylene (5 mL) was
added to a mixture of 2,5-dihexyloxy-1,4-benzenediboronic
acid (0.44 g, 1 mmol), bromobenzene (0.39 g, 2.5 mmol),
and K2CO3 (0.83 g, 6 mmol) in a 10 mL round-bottomed
flask under nitrogen atmosphere. A solution of catalyst 2
(0.007 g) in 1 mL of o-xylene was added into the above
mixture at 130 8C. The mixture was cooled to room
temperature after it was stirred and heated for 72 h. The
mixture was added 16 mL of dry diethyl ether to precipitate
the polystyrene-supported palladacycle catalyst. After the
catalyst was further precipitated by a centrifuge, the upper
liquid layer of the reaction mixture was transferred via a
syringe into another 20 mL round bottom flask. Repeat the
above precipitation procedure one more time. The com-
bined organic layer was dried over MgSO4, filtrated, and
concentrated before recrystallized by EAC and MeOH to
give 0.37 g (85% yield) of the desired product. Mp 67–
68 8C; RfZ0.9 (hexane/EACZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.86 (t, JZ7 Hz, 6H), 1.26–1.36 (m, 12H),
1.65–1.68 (m, 4H), 3.90 (t, JZ6.4 Hz, 4H), 6.98 (s, 2H),
7.32 (t, JZ7.1 Hz, 2H), 7.41 (t, JZ7.5 Hz, 4H), 7.60 (d, JZ
7.75 Hz, 4H) ppm; 13C NMR (CDCl3, 125 MHz) d 13.96,
22.56, 25.72, 29.33, 31.45, 69.70, 116.44, 126.88, 127.89,
129.53, 130.91, 138.46, 150.31 ppm; IR n 1484.8, 1400.4,
1211.4, 1054.1, 763.9, 698.1 cmK1; MS m/z 430 (MC), 347,
262; HRMS Calcd for C30H38O2: 430.2872, found:
430.2869.
4.1.7. Synthesis of polystyrene-supported palladacycle
catalyst 2. trans-Di(m-acetato)-bis[3-(diphenylphosphino)-
4-styryl]dipalladium(II) 4 (93 mg, 0.1 mmol) was added to a
test tube and flushed with nitrogen. A mixture of styrene
(62 mg, 0.6 mmol) and benzene (2 mL) was injected into
the test tube. Then, a mixture of AIBN (18 mg, 0.01 mmol)
and benzene (1 mL) was injected into the stirring test tube.
The reaction mixture was then heated at 70 8C for 40 h. The
mixture was concentrated to dryness. The dry solid was
repeatedly washed by the solvent (THF/hexaneZ1:15). The
isolated polymer was 0.11 g (66% yield). 1H NMR
(500 MHz, CDCl3) d 1.1–2.0 (m, phenylCHCH2), 2.2–2.4
(br s, Ar-CH3), 6.3–6.7 (m, Ar-H), 6.8–7.4 (m, Ar-H) ppm;
31P NMR (121 MHz, CDCl3) d 53.01 ppm. IR (CHCl3) n
3027, 2921, 2858, 1447, 912, 743 cmK1; Gel permeation

F.-T. Luo et al. / Tetrahedron 61 (2005) 6040–6045
6045
4.1.10. 2-[4-(2-Cyanophenyl)-2,5-dihexyloxyphenyl]-
References and notes
benzenecarbonitrile. Following the procedure as described
for the preparation of 2,5-dihexyloxy-1,4-diphenylbenzene
by using 2,5-dihexyloxy-1,4-benzenediboronic acid (0.37 g,
1 mmol), 2-bromobenzene-carbonitrile (0.45 g, 2.5 mmol),
catalyst 2 (0.007 g), and K2CO3 (0.83 g, 6 mmol) to obtain
0.35 g (72% yield) of the desired product. Mp 129–131 8C;
RfZ0.6 (n-hexane/EACZ4/1); 1H NMR (CDCl3,
500 MHz) d 0.83 (t, JZ7 Hz, 6H), 1.21–1.28 (m, 12H),
1.64–1.67 (m, 4H), 3.94 (t, JZ6.5 Hz, 4H), 6.94 (s, 2H),
7.44 (t, JZ7.6 Hz, 2H), 7.56 (d, JZ7.7 Hz, 2H), 7.64 (t, JZ
7.7 Hz, 2H), 7.74 (d, JZ7.6 Hz, 2H) ppm; 13C NMR
(CDCl3, 125 MHz) d 13.88, 22.47, 25.53, 29.05, 31.35,
69.19, 113.21, 115.51, 118.61, 127.42, 128.52, 131.11,
132.17, 132.74, 142.17, 149.80 ppm; IR n 2228.1, 1513.9,
1390.7, 1215.4, 1035.9, 762.8 cmK1; MS m/z 480.2 (MC),
412.0, 395.2, 313.1; HRMS Calcd for C32H36O2N2:
480.2777, found: 480.2786.
1. Merrifield, R. B. Angew. Chem., Int. Ed. Engl. 1985, 24, 799.
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4. Toy, P. H.; Janda, K. D. Acc. Chem. Res. 2000, 33, 546.
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11. Dupont, J.; Pfeffer, M.; Spencer, J. Eur. J. Inorg. Chem. 2001,
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4.1.11. 3-[4-(3-Cyanophenyl)-2,5-dihexyloxyphenyl]-
benzenecarbonitrile. Following the procedure as described
for the preparation of 2,5-dihexyloxy-1,4-diphenylbenzene
by using 2,5-dihexyloxy-1,4-benzenediboronic acid (0.37 g,
1 mmol), 3-bromobenzene-carbonitrile (0.45 g, 2.5 mmol),
catalyst 2 (0.007 g), and K2CO3 (0.83 g, 6 mmol) to give
0.35 g (74% yield) of the desired product. Mp 100–103 8C;
RfZ0.525 (n-hexane/EACZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.87 (t, JZ7.5 Hz, 6H), 1.26–1.68 (m, 12H),
1.67–1.71 (m, 4H), 3.94 (t, JZ6 Hz, 4H), 6.94 (s, 2H), 7.52
(t, JZ7.7 Hz, 2H), 7.63 (d, JZ7.7 Hz, 2H), 7.7 (d, JZ
7.7 Hz, 2H), 7.89 (s, 2H) ppm; 13C NMR (CDCl3,
125 MHz) d 13.96, 22.53, 25.75, 29.17, 31.40, 69.58,
112.21, 115.48, 118.93, 128.77, 129.21, 130.57, 133.14,
133.89, 139.29, 150.16 ppm; IR n 2232.1, 1478.3, 1397.7,
1216.6, 1037.7, 785.9 cmK1; MS m/z 480.2 (MC), 397.1,
325.1, 312.1; HRMS Calcd for C32H36O2N2: 480.2777,
found: 480.2772.
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Chem. Commun. 2000, 1877.
4.1.12. 4-[4-(4-Cyanophenyl)-2,5-dihexyloxyphenyl]-
benzenecarbonitrile. Following the procedure as described
for the preparation of 2,5-dihexyloxy-1,4-diphenylbenzene
by using 2,5-dihexyloxy-1,4-benzenediboronic acid (0.37 g,
1 mmol), 4-bromobenzene-carbonitrile (0.45 g, 2.5 mmol),
catalyst 2 (0.007 g), and K2CO3 (0.83 g, 6 mmol) to give
0.37 g (76% yield) of the desired product. Mp 152–154 8C;
RfZ0.68 (n-hexane/EACZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.87 (t, JZ7 Hz, 6H), 1.25–1.33 (m, 12H),
1.67–1.68 (m, 4H), 3.93 (t, JZ6 Hz, 4H), 6.93 (s, 2H), 7.69
(s, 8H) ppm; 13C NMR (CDCl3, 125 MHz) d 13.89, 22.48,
25.65, 29.11, 31.31, 69.56, 110.70, 115.55, 118.96, 129.82,
130.13, 131.70, 142.80, 150.18 ppm; IR n 2226.4, 1647.6,
1601.0, 1214.5, 776.0 cmK1; MS m/z 480.2 (MC), 397.1,
325.1, 312.1; HRMS Calcd for C32H36O2N2: 480.2777,
found: 480.2772.
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Acknowledgements
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The authors thank the National Science Council and
Academia Sinica for financial supports.