Pd(0)-catalyzed polycondensation of aryl-substituted propargylic carbonates with bifunctional nucleophiles promoted by aryl group on the acetylenic terminal carbon

Article abstract of DOI:10.1002/pola.24475

A Pd(0)-catalyzed polycondensation of bifunctional nucleophiles and propargylic carbonates having an aryl group was investigated. The polycondensation was carried out for tetrahydrofuran at 60 °C for 3 h in the presence of Pd(0) catalyst. The Pd(0)-cataly

Full text of DOI:10.1002/pola.24475

Pd(0)-Catalyzed Polycondensation of Aryl-Substituted Propargylic
Carbonates with Bifunctional Nucleophiles Promoted by Aryl Group
on the Acetylenic Terminal Carbon
NORIYUKI NISHIOKA, TOSHIO KOIZUMI
Department of Applied Chemistry, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan
Received 3 September 2010; accepted 29 October 2010
DOI: 10.1002/pola.24475
Published online 7 December 2010 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: A Pd(0)-catalyzed polycondensation of bifunctional
nucleophiles and propargylic carbonates having an aryl group
was investigated. The polycondensation was carried out for
tetrahydrofuran at 60 ꢀC for 3 h in the presence of Pd(0) cata-
lyst. The Pd(0)-catalyzed polycondensation of phenyl-substi-
tuted propargylic carbonates and nucleophiles proceeded
efficiently, when bis[(2-diphenylphosphino)phenyl]ether was
used as the ligand. We found that the position of the phenyl
group was crucial for the successful polycondensation. The
introduction of a phenyl group on the acetylenic terminal car-
bon remarkably promoted the polycondensation and afforded
high molecular weight polymers. On the other hand, a phenyl
group at the propargylic position was not effective. Propar-
gylic carbonates having a substituted phenyl group were also
examined. Electron-withdrawing group-substituted phenyl
groups on the acetylenic terminal carbon were found to be
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more effective for the polycondensation.
2010 Wiley Period-
icals, Inc. J Polym Sci Part A: Polym Chem 49: 642–649, 2011
KEYWORDS: catalyst; polycondensation; polyethers; synthesis;
transition metal chemistry
INTRODUCTION Palladium-catalyzed reactions of propargylic
compounds with nucleophiles have been shown to be
extremely effective for the construction of carbon–carbon
and carbon–heteroatom bonds.1,2 Many of the reports on the
reactions describe the synthesis of heterocyclic com-
pounds.3–18 Sinou and coworkers19–22 reported a palladium-
catalyzed condensation reaction of propargylic carbonates
and catechol for the synthesis of 1,4-benzodioxins. When the
reaction was performed with methyl-substituted carbonates
1a and 2a, the same product was obtained in 95% yield
[Scheme 1(a)].21,22 We recently reported that a Pd(0)-cata-
lyzed polycondensation of methyl propargyl carbonate and
bisphenols could afford polyethers having exomethylene
groups.23,24 Substituted propargylic carbonates 1a and 1b
could also afford the corresponding polymers 4aa and 4ba
in the polycondensation using Pd(PPh3)4 [Scheme 1(b)],
whereas the expected same polymers 4aa and 4ba were not
obtained at all under the same conditions when propargylic
carbonates 2a and 2b were used [Scheme 1(c)], in contrast
to the Pd(0)-catalyzed reaction of 1a and 2a with catechol.23
These facts prompted us to explore the Pd(0)-catalyzed poly-
condensation with 2. We succeeded in synthesizing the poly-
mers 4aa and 4ba from 2a and 2b, respectively, by use of
an appropriate ligand and found that the polymerization
behavior of 2 was quite different from that of 1. In this arti-
cle, we report the Pd(0)-catalyzed polycondensation between
propargylic carbonates 1 and 2 and oxygen nucleophiles in
detail.
EXPERIMENTAL
Materials
Tris(dibenzylideneacetone)dipalladium(0)-chloroform adduct (Al-
drich, 97%), tetrakis(triphenylphosphine)palladium(0) (Aldrich,
99%), 1,2-bis(diphenylphosphino)ethane (DPPE; Kanto, 98%),
1,3-bis(diphenylphosphino)propane (DPPP; Kanto 98%), 1,4-
bis(diphenylphosphino)butane (DPPB; Kanto, 98%), 1,5-bis
(diphenylphosphino)pentane (DPPPent; Aldrich, 97%), 1,1-
(diphenylphosphino)ferrocene (DPPF; Aldrich, 97%), bis[(2-
diphenylphosphino)phenyl]ether (DPEphos; TCI, 98%), 4,40-
dihydroxydiphenylether (TCI, 98%), 4,40-biphenol (TCI, 99%),
4,40-isopropylidenediphenol (Kanto, 98%), 4,40-thiodiphenol
(TCI, 98%), 4,40-dihydroxybenzophenone (TCI, 98%), 4,40-
dicarboxydiphenyl ether (TCI, 98%), and p-methoxyphenol
(TCI, 99%) were used without further purification. Propargylic
carbonates 1 and 2 were prepared according to the litera-
ture.25–28 Tetrahydrofuran (THF; Wako, 99%) was distilled
from sodium/benzophenone ketyl under nitrogen.
Measurements
1H and 13C NMR spectra were recorded on a JEOL-AL300
spectromer with CDCl3 as a solvent and Me4Si as an internal
standard. Infrared (IR) spectra were obtained using a JASCO
Correspondence to: T. Koizumi (E-mail: tkoizumi@nda.ac.jp)
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Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 49, 642–649 (2011) 2010 Wiley Periodicals, Inc.
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ARTICLE
119.93, 120.08, 120.15, 120.22, 120.53, 121.37, 122.24,
122.32, 122.36, 132.01, 149.76, 150.91, 151.80, 153.53,
153.84, 153.95, 154.68, 163.05, 163.11, 163.18. IR (KBr,
cmꢂ1) 3043, 2981, 2936, 2453, 2031, 1875, 1753, 1646,
1590, 1494, 1373, 1199, 1125, 1092, 1009, 961, 835.
Polymer 4ba
1H NMR (300 MHz; CDCl3, d, ppm) 4.14 (s, 1H, C¼¼CH), 4.53
(s, 2H, CH2 (E)), 4.59 (s, 1H, C¼¼CH), 4.70 (s, 2H, CH2 (Z)),
5.60 (s, 1H, CHPh), 6.05 (s, 1H, C¼¼CHPh (Z)), 6.26 (s, 1H,
C¼¼CHPh (E)), 6.84–7.11 (m, 7H, ArH), 7.19–7.40 (m, 4H,
ArH), 7.55–7.59 (m, 2H, ArH). 13C NMR (75MHz; CDCl3, d,
ppm) 67.64 (CH2), 77.42 (CH), 80.32 (C¼¼CH2), 116.05,
116.10, 117.24, 117.28, 117.38, 118.41, 118.88, 119.00,
119.29, 119.40, 119.47, 119.53, 119.67, 119.71, 119.86,
119.96, 120.01, 120.15, 121.65, 122.13, 122.17, 122.21,
127.02, 127.49, 128.21, 128.40, 128.45, 128.79, 133.88,
147.31, 147.36, 149.92, 150.47, 151.88, 153.55, 153.95,
154.18, 161.77 (C¼¼CH2). IR (KBr, cmꢂ1) 3044, 2934, 1492,
1196. Anal. calcd. for C21H16O3: C, 79.73; H, 5.10. Found: C,
78.98; H, 5.06.
Polymer 4ca
1H NMR (300 MHz; CDCl3, d, ppm) 4.13 (s, 1H, C¼¼CH), 4.52
(s, 2H, CH2 (E)), 4.59 (s, 1H, C¼¼CH), 4.67 (s, 2H, CH2 (Z)),
5.57 (s, 1H, CHAr), 6.12 (s, 1H, C¼¼CHAr (Z)), 6.22 (s, 1H,
C¼¼CHAr (E)), 6.69–6.96 (m, 8H, ArH), 7.15–7.51 (m, 4H,
ArH). 13C NMR (75MHz; CDCl3, d, ppm) 67.46 (CH2), 79.63
(CH), 89.56 (C¼¼CH2), 115.99, 116.05, 116.14, 117.27,
118.47, 118.92, 119.07, 119.34, 119.49, 119.65, 119.72,
119.77, 119.91, 120.01, 120.05, 120.20, 121.88, 122.12,
122.17, 128.38, 128.57, 128.67, 129.68, 130.02, 132.38,
130.00, 133.99, 137.16, 147.91, 147.97, 150.20, 150.49,
153.47, 153.57, 153.86, 154.10, 154.24, 161.35 (C¼¼CH2). IR
SCHEME 1 Pd(0)-Catalyzed condensation of propargylic carbo-
nates and phenols.
FT-IR 460 Plus. Gel permeation chromatography (GPC) was
performed on a Tosoh HLC-8220 system equipped with three
columns (TSK gel, Super HM-M, Super HM-N, and Super
H3000) using THF as an eluent at 40 ꢀC. The GPC was cali-
brated against polystyrene standards. Elemental analyses
were performed on a ThermoFinnigan Flash EA1112 CHN-O
Analyzer.
(KBr, cmꢂ1
)
3043, 1491, 1195, 826. Anal. calcd. for
Typical Procedure for Polymerization
C
21H15ClO3: C, 71.90; H, 4.31. Found: C, 71.43; H, 4.20.
To a mixture of Pd2(dba)3ꢁCHCl3 (where dba is dibenzylide-
neacetone; 0.013 g, 0.0125 mmol) and DPEphos (0.026 mg,
0.05 mmol) in THF (1 mL), 3 (0.4 mmol) was added. To the
mixture, a solution of propargylic carbonate (0.5 mmol) in
THF (1 mL) was added. After being stirred for 3 h at 60 ꢀC
under Ar, the reaction mixture was poured into methanol
(100 mL) to precipitate the polymer. The resulting polymer
was filtered off, washed with methanol, and dried in vacuo
giving polymer 4.
Polymer 4da
1H NMR (300 MHz; CDCl3, d, ppm) 4.13 (s, 1H, C¼¼CH2), 4.53
(s, 2H, CH2 (E)), 4.59 (s, 1H, C¼¼CH), 4.66 (s, 2H, CH2 (Z)),
5.58 (s, 1H, CHAr), 5.99 (s, 1H, C¼¼CHAr (Z)), 6.23 (s, 1H,
C¼¼CHAr (E)) and 6.85–7.06 (m, 10H, ArH), 7.54–7.55 (m,
2H, ArH). 13C NMR (75MHz; CDCl3, d, ppm) 67.53 (CH2),
67.92 (CH2) 79.65 (CH), 89.43 (C¼¼CH2), 115.18, 115.24,
115.46, 115.53, 116.01, 117.26, 118.37, 118.91, 119.05,
119.33, 119.48, 119.63, 119.88, 120.04, 120.19, 121.72,
122.10, 128.72, 128.83, 128.97, 130.42, 130.53, 134.39,
146.94, 150.22, 151.76, 153.93, 154.30, 160.23, 160.93,
161.52, 164.17. IR (KBr, cmꢂ1) 3864, 3832, 3746, 2021,
1881, 1752, 1645, 1499, 1357, 1197, 1099, 1013, 928, 829.
Polymer 4aa
1H NMR (300 MHz; CDCl3, d, ppm) 1.64–1.72 (m, 3H, CH3),
4.01 (d, J ¼ 2.1 Hz, 1H, C¼¼CH (exo)), 4.24 (d, J ¼ 7.5 Hz, 1H,
C¼¼CH (diene)), 4.32–4.52 (br, 1H, C¼¼CH (exo) and 1H,
C¼¼CH (diene)), 4.47 (s, 2H, CH2 (Z)), 4.64 (s, 2H, CH2 (E)),
4.77 (br s, 1H, CH), 5.12 (br s, 1H, C¼¼CHCH3 (Z)), 5.21 (d,
J ¼ 9.6 Hz, 1H, C¼¼CH (diene)), 5.51 (br s, 1H, C¼¼CHCH3
(E)), 5.70 (d, J ¼ 17.4 Hz, 1H, C¼¼CH (diene)), 6.29 (dd, J1 ¼
10.8 Hz, J2 ¼ 16.8 Hz, 1H, CH¼¼CH2 (diene)), 6.83–7.26 (8H,
m, ArH). 13C NMR (75MHz; CDCl3, d, ppm) 10.66 (CH3),
20.25 (CH3), 27.67 (CH3), 67.52 (CH2), 74.55 (CH), 87.66
(C¼¼CH2), 87.88 (CH2), 115.38, 115.47, 115.89, 115.98,
117.01, 117.08, 117.17, 117.22, 118.85, 118.97, 119.07,
119.28, 119.40, 119.46, 119.51, 119.54, 119.68, 119.80,
Polymer 4ea
1H NMR (300 MHz; CDCl3, d, ppm) 3.76 (s, 3H, OCH3), 3.79
(s, 3H, OCH3 (E)), 3.84 (s, 3H, OCH3, (Z)), 4.13 (s, 1H,
C¼¼CH), 4.52 (s, 2H, CH2 (E)), 4.59 (s, 1H, C¼¼CH), 4.69 (s,
2H, CH2 (Z)), 5.54 (s, 1H, CH), 6.05 (s, 1H, C¼¼CHAr (Z)),
6.22 (s, 1H, C¼¼CHAr (E)), 6.68–6.96, (m, 10H, ArH), 7.46–
7.54 (m, 2H, ArH). 13C NMR (75MHz; CDCl3, d, ppm) 55.14
(OCH3), 67.89 (CH2 (E and Z)), 77.42 (CH), 89.28 (C¼¼CH2),
113.84, 116.03, 116.09, 117.22, 118.18, 118.87, 118.98,
Pd(0)-CATALYZED POLYCONDENSATION, NISHIOKA AND KOIZUMI
643

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
119.25, 119.36, 119.44, 119.56, 119.81, 119.95, 120.03,
120.15, 121.34, 122.12, 122.22, 126.60, 128.42, 129.63,
130.18, 130.62, 145.41, 149.96, 150.40, 150.60, 151.03,
151.82, 153.57, 153.77, 153.95, 154.52, 158.90 (C¼¼CHAr
ppm) 67.33 (CH2), 114.24, 114.27, 115.98, 118.45, 119.57,
126.96, 127.63, 128.04, 128.47, 128.53, 130.85, 131.12,
132.15, 132.22, 132.28, 132.57, 133.02, 145.21, 145.27,
54.18, 158.54, 158.71, 161.27, 161.49, 194.05 (C¼¼O). IR
(KBr, cmꢂ1) 3055, 1651, 1597, 1500, 1222, 1160. Anal.
Calcd. for C22H16O3: C, 80.47; H, 4.91. Found: C, 79.52; H,
4.93.
(E)), 159.47 (C¼¼CHAr (Z)), 161.93 (C¼¼CH2). IR (KBr, cmꢂ1
)
3041, 2999, 2932, 2834, 1607, 1491, 1197, 829.
Polymer 4bb
1H NMR (300 MHz; CDCl3, d, ppm) 4.25 (s, 1H, C¼¼CH), 4.63
(s, 2H, CH2 (E)), 4.68 (s, 1H, C¼¼CH), 4.78 (s, 2H, CH2 (Z)),
5.72 (s, 1H, CHPh), 6.20 (s, 1H, C¼¼CHPh (Z)), 6.37 (s, 1H,
C¼¼CHPh (E)), 6.96–7.72 (m, 13H, ArH). 13C NMR (75MHz;
CDCl3, d, ppm) 67.09 (CH2), 67.98 (CH), 76.60 (C¼¼CH2),
79.65, 115.21, 115.24 116.30, 116.32, 117.25, 117.92,
120.37, 121.10, 127.09, 127.60, 127.66, 127.74, 127.78,
127.83, 127.95, 128.04, 128.16, 128.26, 128.47, 128.54,
128.85, 128.96, 133.68, 133.79, 135.33, 135.55, 138.52,
146.85, 154.40, 154.60, 154.72, 157.01, 157.18, 157.27,
Polymer 4bf
1H NMR (300 MHz; CDCl3, d, ppm) 3.90 (d, J ¼ 3.3 Hz, 1H,
C¼¼CH), 5.16 (s, 2H, CH2), 5.22(s, 1H, C¼¼CH), 6.48 (s, 1H,
C¼¼CHPh), 6.95–7.467 (m, 9H, ArH), 7.94–8.17 (m, 4H, ArH).
13C NMR (75MHz; CDCl3, d, ppm) 64.65 (CH2), 118.64,
118.97, 121.04, 124.32, 124.63, 125.31, 125.62, 128.13,
128.53, 128.72, 128.81, 131.82, 131.88, 132.03, 132.10,
132.52, 132.58, 132.94, 143.13, 159.89, 160.22, 160.60,
160.93, 163.42, 165.24. IR (KBr, cmꢂ1) 3066, 1727, 1593,
1498, 1440, 1241, 1159, 1089.
157.40, 157.57, 157.68, 161.26 (C¼¼CH2). IR (KBr, cmꢂ1
)
3037, 2934, 2862, 1602, 1489, 1223.
Pd(0)-Catalyzed Reaction of 2a and p-Methoxyphenol
To a mixture of Pd2(dba)3ꢁCHCl3 (0.013 g, 0.0125 mmol) and
DPEphos (0.027 mg, 0.05 mmol) in THF (1 mL), p-methoxy-
phenol (0.124 g, 1.0 mmol) was added. To the mixture, a so-
lution of 2a (0.068 g, 0.5 mmol) in THF (1 mL) was added.
After being stirred for 3 h at 60 ꢀC under Ar, the reaction
mixture was evaporated and the residue was purified by
flash chromatography on silica gel (hexane/EtOAc ¼ 4:1) to
afford model products 5 and 6 (0.113 g, 75%) and diene 7
(0.004 g, 5%). The model products 5 and 6 were isolated as
a mixture.
Polymer 4bc
1H NMR (300 MHz; CDCl3, d, ppm) 4.19 (s, 1H, C¼¼CH), 4.54
(s, 2H, CH2 (E)), 4.61(s, 1H, C¼¼CH), 4.68 (s, 2H, CH2 (Z)),
5.61 (s, 1H, CHPh), 6.14 (s, 1H, C¼¼CHPh (Z)), 6.31 (s, 1H,
C¼¼CHPh (E)), 6.80–7.35 (m, 11H, ArH), 7.50–7.53 (m, 2H,
ArH). 13C NMR (75MHz; CDCl3, d, ppm) 65.12 (CH2), 67.14
(CH), 67.19 (C¼¼CH2), 76.58, 79.60, 90.84, 115.72, 115.79,
115.85, 115.93, 116.82, 116.87, 117.69, 118.18, 120.61,
121.43, 121.46, 126.99, 127.16, 127.71, 128.44, 128.53,
128.83, 129.52, 130.70, 131.07, 131.67, 131.82, 132.10,
132.22, 132.34, 132.65, 132.77, 133.33, 133.52, 134.16,
138.12, 146.17, 146.27, 146.36, 154.18, 157.52, 157.86,
160.88 (C¼¼CH2). IR (KBr, cmꢂ1) 3057, 3016, 2934, 2873,
1592, 1484, 1220. Anal. Calcd. for C21H16O2S: C, 75.88; H,
4.85. Found: C, 75.45; H, 4.75.
Model Products 5 and 6
1H NMR (300 MHz; CDCl3, d, ppm) 1.58 (d, J ¼ 6.9, 3H, CH3
(E)), 1.61 (d, J ¼ 7.2, 3H, CH3 (Z)), 1.65 (d, J ¼ 4.8 Hz, 3H,
CH3), 3.60 (s, 3H, OCH3), 3.68 (s, 3H, OCH3 (E)), 3.69 (s, 3H,
OCH3), 3.70 (s, 3H, OCH3 (E and Z)), 3.71 (s, 3H, OCH3 (Z)),
3.90 (d, J ¼ 2.1 Hz, 1H, C¼¼CH), 4.31 (s, 2H, CH2 (E)), 4.33
(d, J ¼ 2.4 Hz, 1H, C¼¼CH), 4.54 (s, 2H, CH2 (Z)), 4.69–4.75
(m, 1H, CH), 4.92–4.99 (m, 1H, C¼¼CHCH3 (Z)), 5.43–5.50 (m,
1H, C¼¼CHCH3 (E)), 6.72–6.98 (m, 8H, ArH). 13C NMR
(75MHz; CDCl3, d, ppm) 10.59 (CH3), 11.56 (CH3), 20.29
(CH3), 55.51 (OCH3), 64.76 (OCH3), 67.61 (OCH3), 74.84
(CH), 87.00 (C¼¼CH2), 107.34 (C¼¼CHAr (E and Z)), 114.41,
114.48, 114.56, 115.93, 117.08, 117.30, 121.51, 122.15,
148.19, 151.91, 154.09, 156.33, 163,64 (C¼¼CH2). IR (KBr,
cmꢂ1) 2941, 2835, 1504, 1218. Anal. Calcd. for C18H20O4: C,
71.98; H, 6.71. Found: C, 71.96; H, 7.04.
Polymer 4bd
1H NMR (300 MHz; CDCl3, d, ppm) 1.55 (s, 6H, CH3 ꢃ 2),
1.58 (s, 6H, CH3 ꢃ 2), 4.16 (s, 1H, C¼¼CH), 4.52 (s, 2H, CH2
(E)), 4.60 (s, 1H, C¼¼CH), 4.68 (s, 2H, CH2 (Z)), 5.61 (s, 1H,
CHPh), 6.13 (s, 1H, C¼¼CHPh (Z)), 6.28 (s, 1H, C¼¼CHPh (E)),
6.76–7.39 (m, 11H, ArH), 7.53–7.57 (m, 2H, ArH); 13C NMR
(75MHz; CDCl3, d, ppm) 30.98 (CH3), 41.64, 41.78, 41.89,
42.02 (C(CH3)2), 65.01 (CH2), 66.89 (CH2), 79.56 (CH), 89.77
(C¼¼CH2), 114.29, 115.32, 116.44, 117.26, 119.35, 120.20,
127.06, 127.32, 127.55, 127.59, 127.64, 127.67, 127.78,
127.81, 127.93, 127.98, 128.07, 128.35, 128.39, 128.42,
128.45, 128.80, 134.02, 138.83, 143.33, 143.58, 145.08,
147.22, 152.97, 153.02, 155.77, 155.82, 156.09, 156.14,
161.47 (C¼¼CH2). IR (KBr, cmꢂ1) 3054, 2930, 2595, 1650,
1597, 1500, 1447, 1415, 1222, 1159. Anal. Calcd. for
Diene 7
1H NMR (300 MHz; CDCl3, d, ppm) 3.27 (s, 3H, OCH3), 4.06
(s, 1H, C¼¼CH), 4.31 (s, 1H, C¼¼CH), 5.15 (d, J ¼ 10.8 Hz, 1H,
HC¼¼CH2), 5.67 (d, J ¼ 17.1 Hz, 1H, HC¼¼CH2), 6.22 (dd, J1 ¼
10.8 Hz, J2 ¼ 18.0 Hz, 1H, HC¼¼CH2), 6.78–7.19 (m, 4H, ArH).
13C NMR (75MHz; CDCl3, d, ppm) 55.56 (CH3), 93.62
(C¼¼CH2), 114.54, 115.13 (HC¼¼CH2), 121.57, 132.24
C24H22O2: C, 84.18; H, 6.48. Found: C, 84.40; H, 6.17.
Polymer 4be
1H NMR (300 MHz; CDCl3, d, ppm) 4.43 (s, 1H, C¼¼CH), 4.72
(s, 2H, CH2 (E)), 4.84 (s, 2H, CH2 (Z)), 4.89 (s, 1H, C¼¼CH),
5.79 (s, 1H, CHPh), 6.04 (s, 1H, C¼¼CHPh (Z)), 6.45 (s, 1H,
C¼¼CHPh (E)), 6.88–7.12 (m, 4H, ArH), 7.20–7.25 (m, 3H,
ArH), 7.51–7.73 (m, 6H, ArH). 13C NMR (75MHz; CDCl3, d,
(HC¼¼CH2), 148.99, 155.98, 159.20 (C¼¼CH2). IR (KBr, cmꢂ1
)
2959, 1585, 1504, 1291, 1217, 1095, 1034, 808.
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TABLE 1 Pd(0)-Catalyzed Polycondensation of Propargylic Carbonates and 3aa
Yield
Polymer (%)b
x/yd
c
c
Run Carbonate Pd(0)
Mn
Mw/Mn
1
2
3
4
5
6
7
a
2a
2b
2b
1a
1b
1b
1b
Pd2(dba)3 ꢁ CHCl3/DPEphos 4aa
Pd2(dba)3 ꢁ CHCl3/DPEphos 4ba
Pd2(dba)3 ꢁ CHCl3/DPPF 4ba
31
83
63
36
79
79
77
4,800 3.73
19/81
63/38
72/28
20/80
59/41
70/30
54/46
7,000 1.80
6,300 1.80
4,700 1.98
13,000 1.89
13,000 1.66
27,000 2.25
Pd2(dba)3 ꢁ CHCl3/DPEphos 4aa
Pd(PPh3)4
4ba
Pd2(dba)3 ꢁ CHCl3/DPPF
4ba
Pd2(dba)3 ꢁ CHCl3/DPEphos 4ba
Conditions: carbonate (0.5 mmol), 3a (0.4 mmol), Pd(0) (5.0 mol %), ligand (10.0 mol %), THF (2 mL),
60 ꢀC, and 3 h.
b
Insoluble in methanol.
Estimated by GPC (based on PSt).
Determined by 1H NMR.
c
d
RESULTS AND DISCUSSION
nates 2a and 2b could lead to the formation of polymers
4aa and 4ba by use of DPEphos instead of PPh3 as the
ligand.
The polycondensation of 4,40-dihydroxydiphenylether (3a)
and substituted propargylic carbonates 1 and 2 was carried
out in THF at 60 ꢀC for 3 h in the presence of Pd2(dba)3
ꢁ
We next examined the ligand effect on the polycondensation
with 1b having a phenyl group on the acetylenic terminal
carbon. The polycondensation of 1b and 3a tended to pro-
ceed successfully regardless of the kind of the ligands
employed (runs 5–7). In particular, the polycondensation
using DPEphos proceeded efficiently and the Mn of polymer
4ba reached up to 27,000 (run 7). The Mn of polymer 4ba
obtained from 1b was about four times as high as that of
polymer 4ba obtained from 2b (runs 2 and 7). Scheme 3
shows a possible mechanism of the polycondensation with
1b and 2b. The phenyl group appears to play an important
role. The nucleophilic attack by 3aꢂ to intermediate A gen-
erated from 1b seems to occur promptly because the phe-
nyl group can stabilize intermediate B. That is, intermediate
A is activated by the phenyl group. Therefore, it can be pre-
sumed that the polycondensation proceeds efficiently to
produce high molecular weight polymer 4ba. On the other
hand, the phenyl group does not effectively stabilize inter-
mediate D generated from 2b. It seems that intermediate C
has lower reactivity than intermediate A. Both inter-
mediates B and D abstract a proton from 3a and form the
same p-allyl intermediate E. Second nucleophile 3aꢂ attacks
intermediate E to give products 8 and 9. The products 8
and 9 further react with 1b or 2b to give polymer 4ba.
The difference of the reactivities between A and C seems
to be a reason why the molecular weight of the polymer
4ba obtained from 1b was much higher than that of 4ba
from 2b.
CHCl3. We first investigated various phosphine ligands for
the polycondensation with 2a and 2b. DPPE, DPPP, DPPB,
DPPPent, DPPF, and DPEphos were employed. The results
are summarized in Table 1. Among the phosphine ligands,
DPEphos was found to be the most effective ligand for the
polycondensation. The desired polymer 4aa could be
obtained in the polycondensation of 2a and 3a only when
DPEphos was used (run 1). The unit ratio (x/y) was 19/81.
The yield and the molecular weight were not high, presum-
ably due to termination by b-hydride elimination. The similar
result was obtained by the polycondensation with 1a having
a methyl group on the acetylenic terminal carbon (run 4). A
diene 7 was isolated as a by-product in the model reaction
of 2a with p-methoxyphenol (Scheme 2). The formation of
another by-product could not be confirmed. The diene 7
seems to be formed via b-hydride elimination, as the p-allyl-
palladium intermediate generated from 2a has methyl pro-
tons as b-hydrogens. The diene protons of 7 were observed
at 4.06, 4.31, 5.15, 5.67, and 6.22 ppm, respectively
[Fig. 1(a)]. The polymer termini of 4aa could be observed as
a diene moiety by 1H NMR [Fig. 1(b)]. The NMR data were
in good agreement with that of diene 7. The polycondensa-
tion of 2b and 3a could also give the expected polymer 4ba,
the Mn of which was 7000 (run 2). DPPF and DPEphos were
good ligands in this case (run 3). Other ligands, DPPE, DPPP,
DPPB, and DPPPent, were not effective for the polycondensa-
tion with 2b and 3a. Thus, we found that propargylic carbo-
SCHEME 2 Pd(0)-Catalyzed model reaction of 2a and p-methoxyphenol.
Pd(0)-CATALYZED POLYCONDENSATION, NISHIOKA AND KOIZUMI
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
In the polycondensation of 1b and 3a, bidentate ligands
other than DPEphos also afforded polymer 4ba: DPPP (Mn ¼
9300, x/y ¼ 93/7), DPPB (Mn ¼ 10,200, x/y ¼ 83/17), and
DPPPent (Mn ¼ 16,300, x/y ¼ 81/19). The ratio of y unit
increased with increasing bite angle of the ligands [(95ꢀ
(DPPP29), 99ꢀ (DPPB29), 104.37ꢀ (DPPPent30), 101.23ꢀ
(DPPF31), and 103.93ꢀ (DPEphos31)] and was changed from
7% (DPPP) to 46% (DPEphos). In general, nucleophiles
attack a less substituted carbon on p-allylpalladium inter-
mediates. However, Leeuwen and coworkers31,32 reported
that larger bite angle of phosphine ligands leads to the for-
mation of a g1–g2-allyl intermediate and a nucleophile
attacks a more substituted carbon in the Pd(0)-catalyzed
reaction of allylic acetates and nucleophiles. Scheme 4 shows
a possible mechanism for the formation of x and y units. The
ratio of g1–g2-allyl intermediate F seems to increase by
use of a ligand with a large bite angle because of steric
hinderance between the ligand and the phenyl group of
intermediate E.33 Furthermore, the benzyl carbon of the
intermediate F would be more electrophilic because larger
bite angle of ligands results in a decrease of the back-dona-
tion of the Pd center.31,32 In addition, steric hindrance
between the ligand and the phenyl group of p-complex H
FIGURE 1 1H NMR spectra of diene 7 and polymer 4aa (run 4
in Table 1).
SCHEME 4 Possible mechanism for the formation of x and y
SCHEME 3 Possible mechanism of the polycondensation.
units.
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ARTICLE
TABLE 2 Pd(0)-Catalyzed Polycondensation of Aryl-Substituted Propargylic Carbonates and 3aa
d
d
Run
1
Carbonate
Polymer 4 (x/y ratio)b
Yield (%)c
79
Mn
Mw/Mn
32,600
34,800
10,200
2.10
1.96
1.87
2
3
4
72
74
4ca (64/36)
4ea (45/55)
67
58
6,800
8,400
1.80
1.83
5
a
c
Conditions: carbonate (0.5 mmol), 3a (0.4 mmol), Pd2(dba)3ꢁCHCl3
Insoluble in methanol.
d
(2.5 mol %), DPEphos (10.0 mol %), THF (2 mL), 60 ꢀC, and 3 h.
b
Estimated by GPC (based on PSt).
Determined by 1H NMR.
can be reduced by rotation of the allylic carbon. These effects
seem to contribute to increasing the formation of y unit.
Other bisphenols instead of 3a could also be used in the
polycondensation with 1b. These results are summarized
in Table 3. The polycondensation using 4,40-biphenol (3b)
gave high molecular polymer 4bb in good yield, the Mn
of which was 25,200 (run 1). Racemic 1,10-binaphtol was
also examined, but the expected polymer was not formed
at all. A sulfide analog of 3a, 4,40-dihydroxydiphenyl sul-
fide (3c), could be used as a nucleophile and the corre-
sponding polymer 4bc was obtained (run 2), although the
Mn of 4bc was less than half that of 4ba. Bisphenol A
Carbonate 1b could produce higher molecular weight 4ba.
The intermediate B should be more stabilized by electron-
withdrawing aryl groups, which would result in the formation
of higher molecular weight polymer 4. We next synthesized
such aryl-substituted propargylic carbonates and examined
the polycondensation with 3a. The results were shown in Ta-
ble 2. Propargylic carbonates 1c and 1d, which have p-chloro-
phenyl and p-fluorophenyl groups, respectively, on the acety-
lenic terminal carbon, gave higher molecular weight polymers
4ca and 4da as expected (runs 1 and 2). On the other hand,
the polycondensation with p-methoxyphenyl-substituted prop-
argylic carbonate 1e gave lower molecular weight polymer
4ea (run 3). Furthermore, neither p-chlorophenyl nor p-
methoxy groups at the propargylic position was effective
(runs 4 and 5). Thus, we found that propargylic carbonates
having an aryl group on the acetylenic terminal carbon are
excellent monomers for the polycondensation with 3a.
(3d) gave high molecular weight polymer 4bd (Mn
¼
21,300; run 3). The polymer 4be was produced by the
polycondensation with bisphenol analog 3e bearing an
electron-withdrawing group. The Mn of 4be was less than
10,000 (run 4). A dicarboxylic acid, 4,40-dicarboxydiphenyl
ether (3f), could be used as an oxygen nucleophile, but
the Mn of the obtained polymer 4bf was not high. The
corresponding exomethylene unit was not contained in
this case (run 5).
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
TABLE 3 Pd(0)-Catalyzed Polycondensation of 1b and 3a
Polymer 4 (x/y ratio)b
Yield (%)c
88
Mn
Mw/Mn
d
d
Run
1
Nucleophile
25,200
12,700
21,300
7,100
2.56
2
3
4
5
56
70
86
86
1.83
2.03
1.80
1.67
3,000
a
c
Conditions: 1b (0.5 mmol), nucleophile (0.4 mmol), Pd2(dba)3ꢁCHCl3
Insoluble in methanol.
d
e
(2.5 mol %), DPEphos (10.0 mol %), THF (2 mL), 60 ꢀC, and 3 h.
b
Estimated by GPC (based on PSt).
The corresponding exomethylene unit was not observed.
Determined by 1H NMR.
CONCLUSIONS
6 Guo, L. N.; Duan, X. H.; Bi, H. P.; Liu, X.-Y.; Liang, Y. M.
J Org Chem 2007, 72, 1538–1540.
We found that the Pd(0)-catalyzed polycondensation of
bisphenols and substituted propargylic carbonates proceeded
efficiently and gave the high molecular weight polymers in
good yields when DPEphos was used as the ligand. The
introduction of aryl groups on the acetylenic terminal carbon
remarkably promoted the polycondensation to afford high
molecular weight polymers. The Mn values were higher,
when the propargylic carbonates bearing an electron-with-
drawing aryl group on the acetylenic terminal carbon were
used.
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