Polymeric Phosphine Ligand from Ring-Opening Metathesis Polymerization of a Norbornene Derivative. Applications in the Heck, Sonogashira, and Negishi Reactions

Article abstract of DOI:10.1021/jo035318z

The phosphine-containing polymer 1 is obtained by ruthenium-catalyzed ring-opening metathesis polymerization of the norbornene derivative 2. Polymer 1 is employed as the polymer support in the palladium-catalyzed Heck, Sonogashira, and Negishi reactions,

Full text of DOI:10.1021/jo035318z

SCHEME 1 a
P olym er ic P h osp h in e Liga n d fr om
Rin g-Op en in g Meta th esis P olym er iza tion
of a Nor bor n en e Der iva tive. Ap p lica tion s
in th e Heck , Son oga sh ir a , a n d Negish i
Rea ction s
Yun-Chin Yang†,| and Tien-Yau Luh*,†,‡,|
Department of Chemistry and Institute of Polymer Science
and Engineering, National Taiwan University, Taipei,
Taiwan 106, and Institute of Chemistry, Academia Sinica,
Nangang, Taipei, Taiwan 115
tyluh@chem.sinica.edu.tw
Received September 7, 2003
Abstr a ct: The phosphine-containing polymer 1 is obtained
by ruthenium-catalyzed ring-opening metathesis polymer-
ization of the norbornene derivative 2. Polymer 1 is em-
ployed as the polymer support in the palladium-catalyzed
Heck, Sonogashira, and Negishi reactions, and the corre-
sponding (methoxymethylphenyl)diphenylphosphine (6) ligand
is used for comparison. The polymer-supported catalysts
retain most of their catalytic activities in these coupling
reactions in the recycling processes.
a
(a) Cyclopentadiene, -78 °C, 95%. (b) 4-Bromobenzyl bromide,
The use of transition-metal catalysts immobilized on
polymer supports is well-documented.1 Catalysts can in
general be recovered by filtration2 or by biphasic separa-
tion.3 Cross-linked styrene-based polymer supports are
one of the most popular resins for this purpose. Soluble
polymer supports such as those derived from polyethers,4
polyacrylates,5 polyethylene,6 or fluorinated polymers7
provide important alternative sources. To the best of our
knowledge, phosphine-containing polymer supports arisen
from ring-opening metathesis polymerization (ROMP) of
norbornene derivatives have been sporadically explored.8
It is noteworthy that using such phosphine-containing
K2CO3, refluxing MeCN, 78%. (c) nBuLi, -78 °C, and then ClPPh2,
60%. (d) 5, rt.
norbornene derivatives would make it more difficult to
proceed with the ROMP reaction because the ligand on
the catalyst may readily undergo exchange with the
phosphine moiety on the substrates, which may reduce
the activity of the catalyst.9 It is envisaged that the recent
highly reactive N-heterocyclic ruthenium carbene cata-
lyst10 may tolerate the presence of the phosphine moiety
in the substrates.11 We now report the synthesis of the
phosphine-containing polymer 1 by ROMP of the corre-
sponding monomer 2 and the use of 1 as the polymer-
supported ligand in palladium-catalyzed C-C bond for-
mation reactions.
Polymer 1 was prepared according to the reaction
sequence shown in Scheme 1. Treatment of 3 with K2-
CO3 and 4-bromobenzyl bromide in refluxing CH3CN
afforded dibromide 4 in 78% yield. Reaction of 4 with
nBuLi at -78 °C followed by displacement with ClPPh2
gave the monomer 2 in 60% yield. Polymerization of 2
using second-generation Grubbs’ catalyst 512 in THF at
room temperature for 24 h yielded the corresponding
polymer 1. Matrix-assisted laser desorption ionization
time of flight (MALDI-TOF) analysis indicated that the
polymer may mainly consist of 4-6 repetitive monomeric
† Department of Chemistry, National Taiwan University.
‡ Institute of Polymer Science and Engineering, National Taiwan
University.
| Institute of Chemistry, Academia Sinica.
(1) (a) Bailey, D. C.; Langer, S. H. Chem. Rev. 1981, 81, 110. (b)
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P. Solid-Phase Synthesis and Combinatorial Techniques; J ohn Wiley:
New York, 2001. (d) Burgess, K. Solid-Phase Organic Synthesis; J ohn
Wiley: New York, 2000. (e) Pomogailo, A. D. Catalysis by Polymer-
Immobilized Metal Complexes; Gordon and Breach: Australia, 1998.
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102, 3325. (b) Toy, P. H.; J anda, K. D. Acc. Chem. Res. 2000, 33, 546.
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Am. Chem. Soc. 2000, 122, 9058. (b) Bergbreiter, D. E.; Osburn, P. L.;
Smith, T.; Li, C.; Frels, J . D. J . Am. Chem. Soc. 2003, 125, 6254. (c)
Bergbreiter, D. E.; Hughes, R.; Besinaiz, J .; Li, C.; Osburn, P. L. J .
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11101. (b) Pollino, J . M.; Weck, M. Org. Lett. 2002, 4, 753.
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Herrmann, W. A. Angew. Chem., Int. Ed. 1999, 38, 2416. (b) Scholl,
M.; Trnka, T. M.; Morgan, J . P.; Grubbs, R. H. Tetrahedron Lett. 1999,
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Org. Lett. 2002, 4, 1975.
(12) Mes: 2,4,6-mesitylenyl. dba: dibenzylideneacetone.
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3301.
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10.1021/jo035318z CCC: $25.00 © 2003 American Chemical Society
Published on Web 11/19/2003
9870
J . Org. Chem. 2003, 68, 9870-9873

TABLE 1. Use of P h osp h in e Liga n d s 1 or 6 in th e
P a lla d iu m -Ca ta lyzed Heck , Son oga sh ir a , a n d Negish i
Rea ction s
employed, five catalytic cycles had been performed. The
catalyst retained more than 90% of the activity of the
catalyst in the previous cycle.
Heck reaction Sonogashira reaction Negishi reaction
In the Sonogashira reaction, phenylacetylene was
treated with methyl 4-iodobenzoate in the presence of
Pd2(dba)3,12 CuI, and phosphine ligand (1 or 6) in reflux-
ing Et3N for 12 h (eq 2). In a manner similar to that
described for the Heck reaction, the mixture was worked
up to give 8, and the catalyst was recovered for the next
cycle. It is noteworthy that Et3NHI was also precipitated
and was mixed with the catalyst for the next cycle.
However, the presence of this side product did not show
any appreciable effect on the reaction. The results are
also outlined in Table 1. Again, the phosphine ligand is
indispensable in this reaction. The monomeric ligand 6
gave an excellent yield in cycle 1, but the activity
significantly decreased in the second cycle and no reac-
tion was observed in the third cycle. The catalytic activity
also gradually fell by approximately 4-8% in each recycle
experiment when 1 was used.
nil
6
1
nil
(%)
6
(%)
1
(%)
nil
6
1
cycle (%)a (%) (%)
(%) (%) (%)
1
2
3
4
5
63
15
0
93 95
30 90
0
42
0
93
34
0
95
90
86
79
65
42
0
83
0
85
76
47
12
0
87
82
85
a
No phosphine ligand was added.
units.13 31P NMR of 1 and 2 appeared as singlets at δ
-5.57 and -5.24, respectively. Because each of the
monomeric units contained two phosphine groups, the
loading of the phosphine moiety in 1 was therefore fairly
high (2.8 mmol/g). Polymer 1 is soluble in moderate polar
organic solvents such as THF, toluene, or dichlo-
romethane but insoluble in alkane solvents, ether, and
DMF at room temperature. At elevated temperature, a
homogeneous solution of 1 in DMF was obtained.14
Negishi coupling reaction was also employed to test the
activity of the polymer support 1. 4-Cyanophenylzinc
bromide was allowed to react with methyl 4-iodobenzoate
To test the efficacy of 1 as a polymer support in
catalysis, a series of coupling reactions was examined.
4-(Methoxymethylphenyl)diphenylphosphine (6) was also
used as a ligand for comparison. In the Heck reaction, a
mixture of iodobenzene, methyl acrylate, and Bu4NOAc
in the presence of Pd(OAc)2 and the phosphine ligand (1
or 6) in DMF was heated at 80 °C for 12 h (eq 1). After
cooling to room temperature, the mixture was filtered,
and the solid material was washed with ether, evacuated,
and used directly for the next catalytic reaction. The
filtrate was worked up as usual to afford the coupling
product 7. DMF was chosen as the solvent not only
because it is a common solvent for the Heck reaction but
also because the polymer ligand 1 exhibited different
solubilities at different temperatures. The results are
summarized in Table 1.
12
in the presence of Pd(dba)2 and phosphine ligand (1 or
6) in THF at room temperature for 12 h (eq 3). The
mixture was poured into ether, and the precipitate was
collected and washed with ether. Usual workup of the
filtrate yielded the coupling product 9. As can be seen
from Table 1, no reaction occurred when the recycled
catalyst with monomeric phosphine ligand was used, and
the catalytic activity reduced significantly when the
recycled polymer-supported catalyst (from 1) was em-
ployed. As mentioned earlier, polymer 1 is readily soluble
in THF, which may cause more difficulty in the catalyst
recovery.
In summary, we have demonstrated that the phos-
phine-containing polymer derived from the ROMP of the
norbornene derivative can serve as a polymer support for
the palladium-catalyzed C-C bond formation. Further
extension in other applications is in progress in our
laboratory.
Apparently, the presence of phosphine ligands is es-
sential to give a better yield of 7 than those without
phosphines. When 6 was used, the yield of the reaction
dropped from 93% in the first cycle to 30% in the second
cycle, and no reaction was observed in the third cycle.
Presumably, the majority of the palladium catalyst may
remain in the DMF solution, and the insoluble portion
was barely enough to initiate the second cycle of the Heck
reaction. On the other hand, when polymer 1 was
(13) GPC analysis using polystyrene as a ref, however, gave a much
lower average molecular weight (Mn ) 1000, PDI ) 1.1).
(14) The solubilities of 1 in DMF were 46 mg/mL at 80 °C and <0.7
mg/mL at 25 °C. The solubilities of 1 in Et3N were ca. 0.2 and 0.5
mg/mL at 25 and 80 °C, respectively.
Exp er im en ta l Section
1,4,4a ,8a -Tet r a h yd r o-1,4-m et h a n on a p h t h a len e-5,8-d i-
on e (3). To a methanol solution (40 mL) of 1,4-benzoquinone
J . Org. Chem, Vol. 68, No. 25, 2003 9871

(21.62 g, 200 mmol) was added a methanol (10 mL) solution of
freshly cracked cyclopentadiene (13.5 mL, 200 mmol) at -78 °C.
The reaction mixture was gradually warmed to room tempera-
ture and stirred for 6 h. Removal of the solvent afforded yellow
needles 3 (33.15 g, 95%). Mp: 74-76 °C (ether, lit.15 76-78 °C).
5,8-Bis(4-b r om ob e n zyloxy)-1,4-d ih yd r o-1,4-m e t h a n o-
n a p h th a len e (4). A mixture of 3 (1.74 g, 10 mmol), K2CO3 (8.3
g, 60 mmol), and 4-bromobenzylbromide (5.0 g, 20 mmol) in CH3-
CN (100 mL) was refluxed for 36 h under a nitrogen atmosphere.
The mixture was quenched with saturated NH4Cl (150 mL), and
the organic layer was separated. The aqueous layer was ex-
tracted with CH2Cl2 (2 × 100 mL). The combined organic layers
were washed with saturated NaHCO3 (2 × 400 mL), dried
(MgSO4), filtered, and evaporated in vacuo. The residue was
chromatographed (CH2Cl2/hexane, 1:4) to give 4 as white needles
(4.00 g, 78%). Mp: 182-183 °C (EtOH). 1H NMR (400 MHz,
CDCl3) δ: 2.16 (d, J ) 7.0 Hz, 1 H), 2.21 (dt, J ) 7.0, 1.6 Hz, 1
H), 4.15 (dt, J ) 3.6, 1.6 Hz, 2 H), 4.96 (s, 4 H), 6.48 (s, 2 H),
6.77-6.79 (m, 2 H), 7.28 and 7.50 (AA′XX′, J ) 8.1, 0.3, 2.1, 2.1
Hz, 8 H). 13C NMR (100 MHz, CDCl3) δ: 47.1, 69.9, 70.7, 111.8,
121.6, 129.0, 131.5, 136.6, 141.5, 142.8, 147.9. IR (KBr) ν: 3059,
3001, 2969, 2935, 2885, 2853, 1489, 1454, 1408, 1372, 1300,
1260, 1225, 1202, 1166, 1117, 1091, 1067, 1011, 978, 907, 895,
834, 808, 787, 731, 494, 481 cm-1. MS (FAB) m/z (relative
intensity): 514 (12), 512 (23), 510 (M+, 11), 171 (40), 169 (41),
155 (47), 139 (22), 138 (33), 137 (100), 124 (11), 120 (19), 97 (12),
95 (13), 91 (25), 83 (14), 77 (22), 57 (16). HRMS calcd for
C25H20Br2O2: 509.9830. Found: 509.9824. Anal. Calcd: C, 58.62;
H, 3.94. Found: C, 58.43; H, 3.77.
5,8-Bis(4-d ip h en ylp h osp h or a n ylben zyloxy)-1,4-d ih yd r o-
1,4-m eth a n on a p h th a len e (2). Under an argon atmosphere, a
THF solution (20 mL) of 4 (1.53 g, 3 mmol) was treated with
nBuLi (3.0 mL of a 2.5 M solution, 7.5 mmol) and stirred at -78
°C for 30 min. A THF solution (20 mL) of chlorodiphenylphos-
phine (1.50 mL, 8 mmol) was then added to the reaction mixture
at -78 °C. After 1 h, the mixture was gradually warmed to room
temperature and stirred for 5 h. The reaction was quenched with
saturated NH4Cl (30 mL), and the organic layer was separated.
The aqueous layer was extracted with CH2Cl2 (3 × 20 mL). The
combined organic extracts were washed with water (50 mL),
dried (MgSO4), filtered, and evaporated in vacuo to afford the
crude product, which was chromatographed on silica gel (CH2-
Cl2/hexane, 1:2) to furnish 2 as white needles (0.43 g, 60%).
Mp: 146-147 °C (EtOH). 1H NMR (400 MHz, CDCl3) δ: 2.12
(dt, J ) 7.0, 1.4 Hz, 1 H), 2.17 (dt, J ) 7.0, 1.6 Hz, 1 H), 4.14
(dt, J ) 3.7, 1.5 Hz, 2 H), 4.99 (s, 4 H), 6.51 (s, 2 H), 6.74 (t, J
) 1.8 Hz, 2 H), 7.27-7.37 (m, 28 H). 13C NMR (100 MHz, CDCl3)
δ: 47.1, 70.0, 71.3, 112.0, 127.4 (d, J ) 7.2 Hz), 128.5 (d, J )
6.8 Hz), 128.7, 133.7 (d, J ) 19.2 Hz), 133.9 (d, J ) 19.4 Hz),
136.7 (d, J ) 11.1 Hz), 137.1 (d, J ) 10.7 Hz), 138.3, 141.5, 142.9,
148.1. 31P NMR (121 MHz, CDCl3) δ: -5.24. IR (KBr) ν: 3068,
3000, 2933, 2866, 1585, 1490, 1459, 1433, 1400, 1301, 1256,
1164, 1116, 1090, 1043, 1017, 908, 810, 743, 696, 505 cm-1. MS
(FAB) m/z (relative intensity): 723 (M + H+, 53), 722 (M+, 40),
292 (13), 289 (13), 277 (10), 276 (53), 275 (100), 197 (16), 185
(13), 183 (20), 167 (22), 165 (17), 155 (18), 138 (18), 137 (34),
121 (17), 107 (10). HRMS calcd for C49H41O2P2 (M + H+):
723.2599. Found: 723.2582. Anal. Calcd for C49H40O2P2: C,
81.42; H, 5.58. Found: C, 81.17; H, 5.45.
1017, 806, 743, 694, 539 cm-1. MALDI-TOF MS (dithranol) m/z
(relative intensity): 2356 (53), 3110 (100), 3865 (77), 4619 (23),
5373 (6), 6128 (3).
(4-Meth oxym eth ylp h en yl)d ip h en ylp h osp h a n e (6). Under
an argon atmosphere, a THF solution (20 mL) of 1-bromo-4-
n
methoxymethylbenzene (4.02 g, 20 mmol) was treated with
-
BuLi (10 mL of a 2.5 M solution, 25 mmol) at -78 °C, and the
mixture was stirred for 30 min. A THF solution (10 mL) of
chlorodiphenylphosphine (5.40 mL, 30 mmol) was then intro-
duced at -78 °C. After 1 h, the mixture was gradually warmed
to room temperature, stirred for 5 h, and quenched with
saturated NH4Cl (30 mL). The organic layer was separated, and
the aqueous layer was extracted with Et2O (3 × 20 mL). The
combined organic extracts were washed with water (50 mL),
dried (MgSO4), filtered, and evaporated in vacuo to afford the
crude product, which was chromatographed on silica gel (hexane/
CH2Cl2, 1:4) to give 6 as a colorless oil (5.58 g, 91%). 1H NMR
(400 MHz, CDCl3) δ: 3.40 (s, 3 H), 4.45 (s, 2 H), 7.26-7.35 (m,
14 H). 13C NMR (100 MHz, CDCl3) δ: 58.2, 74.3, 127.7 (d, J )
7.1 Hz), 128.4 (d, J ) 6.9 Hz), 128.6, 133.8 (d, J ) 19.1 Hz),
133.9 (d, J ) 19.4 Hz), 136.4 (d, J ) 10.5 Hz), 137.1 (d, J ) 10.5
Hz), 138.8. 31P NMR (121 MHz, CDCl3) δ: -5.24.
Heck Rea ction . A DMF suspension (10 mL) of tetrabutyl-
ammonium acetate (0.75 g, 2.5 mmol) and crushed 4A molecular
sieve (0.4 g) was stirred for 15 min. Phosphine 1 (36.1 mg, 0.05
mmol), iodobenzene (0.11 mL, 1.0 mmol), and methyl acrylate
(0.18 mL, 2 mmol) were then successively added to the mixture,
and the mixture were stirred for another 15 min before addition
of palladium acetate (11.2 mg, 0.05 mmol). The reaction mixture
was stirred at 80 °C for 12 h and then filtered on filter paper.
The insoluble materials were washed with Et2O (50 mL) and
collected for subsequent runs. The filtrate was extracted with
water (50 mL). The aqueous layer was extracted with Et2O (3
× 50 mL). The combined organic extracts were washed with
saturated NH4Cl (50 mL), dried (MgSO4), filtered, and evapo-
rated in vacuo to afford the crude product. The crude product
was purified by flash column chromatography (CH2Cl2/hexane,
1:4) and recrystallized from ethanol to provide 7 as a white solid
(0.15 g, 95%). Mp: 34-35 °C (lit.16 35-36 °C).
A similar procedure was employed when phosphine 6 was
used.
Son oga sh ir a Rea ction . To methyl 4-iodobenzoate (262 mg,
1.0 mmol) in Et3N (10 mL) was added Pd2(dba)3‚CHCl3 (26 mg,
0.025 mmol) and phosphine 1 (36.1 mg, 0.10 mmol). The reaction
mixture was bubbled with nitrogen for 10 min followed by the
addition of phenylacetylene (0.11 mL, 1.1 mmol) and CuI (4.8
mg, 0.025 mmol). The mixture was refluxed for 12 h. After
cooling to room temperature, the mixture was filtered on filter
paper. The insoluble materials were washed with Et2O (50 mL)
and collected for subsequent runs. The filtrate was added to a
saturated NH4Cl solution (50 mL), and the organic layer was
separated. The organic layer was washed with saturated NH4-
Cl (3 × 50 mL), dried (MgSO4), filtered, and evaporated in vacuo
to afford the crude product, which was chromatographed on silica
gel (CH2Cl2/hexane, 1:4) to give 8 as a white solid (0.22 g, 95%).
Mp: 120-121 °C (EtOH, lit.17 124 °C).
A similar procedure was employed when phosphine 6 was
used.
Negish i Rea ction . 4-Bromobenzonitrile (457.4 mg, 1.2 mmol)
in THF (10 mL) was treated with nBuLi (0.5 mL of a 2.5 M
solution, 1.25 mmol) at -78 °C for 30 min. ZnBr2 (292 mg, 1.3
mmol) in THF (5 mL) was then added at -78 °C, and after being
stirred for 5 min, the mixture was slowly warmed to 0 °C and
then transferred via a cannula to another flask containing Pd-
(dba)2 (23 mg, 0.04 mmol), phosphine 1 (57.8 mg, 0.08 mmol),
and methyl 4-iodobenzoate (262 mg, 1.0 mmol) in THF (10 mL).
The mixture was then warmed to room temperature and stirred
for 12 h. Et2O (50 mL) was added, and the mixture was filtered
on filter paper. The insoluble materials were washed with Et2O
(50 mL) and collected for subsequent runs. The filtrate was
extracted with saturated NH4Cl (3 × 100 mL), dried (MgSO4),
Syn th esis of P olym er 1. In a glovebox, to a THF solution
(5 mL) of 3 (361 mg, 0.5 mmol) was added 5 (21 mg, 0.025 mmol),
and the mixture was stirred at room temperature for 24 h and
then poured into pentane (50 mL) to form a pink suspension.
The suspension was centrifuged, and the pink precipitate was
collected. The precipitate was dissolved in 2 mL of CH2Cl2 and
reprecipitated in pentane (20 mL) before centrifuging. The
reprecipitation was repeated a few times to provide 1 as a pale
yellowish white powder (325 mg, 90%). 1H NMR (400 MHz,
CDCl3) δ: 1.25-1.85 (br, 1H), 2.15-2.75 (br, 1H), 3.45-4.45 (br,
2H), 4.45-5.15 (br, 4H), 5.28-5.90 (br, 2H), 6.00-6.50 (br, 2H),
6.60-7.80 (br, 28H). 31P NMR (121 MHz, CDCl3) δ: -5.57. IR
(KBr) ν: 2959, 2919, 1488, 1456, 1434, 1398, 1379, 1260, 1184,
(16) Inoue, T.; Tsutsumi, S. J . Am. Chem. Soc. 1965, 87, 3525.
(17) Drefahl, G.; Ploetner, G. Chem. Ber. 1960, 93, 990.
(15) Marchand, A. P.; Allen, R. W. J . Org. Chem. 1974, 39, 1596.
9872 J . Org. Chem., Vol. 68, No. 25, 2003

filtered, and evaporated in vacuo to afford the crude product,
which was chromatographed on silica gel (CH2Cl2/hexane, 1:1)
to give 9 as a white solid (0.20 g, 85%). Mp: 104-105 °C (EtOH,
lit.18 102-103 °C).
A similar procedure was employed when phosphine 6 was
used.
Ack n ow led gm en t. We thank the National Science
Council and the Ministry of Education of the Republic
of China for financial support.
(18) Ananthakrishnanadar, P.; Kanan, N. J . Chem. Soc., Perkin
Trans. 2 1984, 1, 35.
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J . Org. Chem, Vol. 68, No. 25, 2003 9873