Non-cross-linked polystyrene-supported triphenylarsonium halides and their use in the arsa-Wittig reaction

Article abstract of DOI:10.1016/j.tet.2011.09.005

Non-cross-linked polystyrene-supported (carbomethoxymethyl) triphenylarsonium bromide (1) and benzyltriphenylarsonium iodide (2) were synthesized. They showed similar reactivities compared with the free arsonium salts in the arsa-Wittig reaction. The use of the polymer-supported reagents facilitated product purification and rendered the organoarsenic reagents easily separable and recyclable.

Full text of DOI:10.1016/j.tet.2011.09.005

Tetrahedron 67 (2011) 8769e8774
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Non-cross-linked polystyrene-supported triphenylarsonium halides and their use
in the arsa-Wittig reaction
*
Kelvin C.Y. Lau, Pauline Chiu
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 July 2011
Received in revised form 30 August 2011
Accepted 6 September 2011
Available online 8 September 2011
Non-cross-linked polystyrene-supported (carbomethoxymethyl)triphenylarsonium bromide (1) and
benzyltriphenylarsonium iodide (2) were synthesized. They showed similar reactivities compared with
the free arsonium salts in the arsa-Wittig reaction. The use of the polymer-supported reagents facilitated
product purification and rendered the organoarsenic reagents easily separable and recyclable.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
Arsine
Polymer support
Wittig reaction
Ylides
1. Introduction
already described a controlled synthesis of non-cross-linked poly-
styrene (NCPS) triphenylarsine and its application as recyclable li-
Organoarsenic reagents have found various applications in or-
ganic synthesis. Triphenylarsine is an important ligand in Pd-
mediated transformations.1 Arsonium ylides2 have been utilized
in cyclopropanations,3 epoxidations,4 aziridinations,5 aldehyde
coupling reactions,6 and the synthesis of vinyl halides7 and het-
erocycles.8 In particular, olefination by the reaction of arsonium
ylides with aldehydes,9 i.e., the arsa-Wittig reaction, offers syn-
thetic advantages over the corresponding phosphonium counter-
parts (the phospha-Wittig reaction), including milder reaction
conditions,10 higher stereoselectivities11 and/or yields,12 and the
possibility for catalysis,13 due to the intrinsically higher nucleo-
philicity14 of arsonium ylides.
However, despite the utility of arsines in organic synthesis, most
practitioners consider that any advantages are far outweighed by
their toxicity by creating problems in the handling, purification and
disposal of these reagents. The development of reactions using
a catalytic amount of arsine reduces the quantities used and sub-
sequently needed to be separated from the product.13 The use of
polymer13c,15 or silica16 supports to immobilize arsenic reagents is
another strategy, which provides additional benefits including
simplification of reaction workup and product purification.17 Fi-
nally, the ability to isolate and recycle the arsine increases the
economy of the reaction and limits the actual amounts of arsines
that need to be handled and stocked. In this connection, we have
gands in Suzuki15a and Stille15c coupling reactions.
On the other hand, the use of supported arsines for the synthesis
and reactions of immobilized arsonium salts and ylides impart even
greater benefits in handling, as stoichiometric amounts of arsines
are used in arsa-Wittig reactions. The first examples have been
reported by Tao and Hu, who prepared and isolated arsonium salts
and ylides from the reaction of polystyrene-supported tripheny-
larsine and bromoacetophenones.18 To further exploit the potential
of arsonium ylides in organic synthesis but with the additional aims
of mitigating the toxicity of arsines, streamlining product isolation,
and obviating the problems associated with their disposal, we have
synthesized two soluble and recyclable non-cross-linked poly-
styrene (NCPS) supported arsonium halides, which have been
converted to arsonium ylides in situ and shown to undergo the
arsa-Wittig reaction in the same pot.
2. Results and discussion
2.1. Synthesis of NCPS-arsonium halides 1, 2
The NCPS-triphenylarsine (3) used had been synthesized from
a copolymerization of a 1:8 ratio of diphenylarsinated styrene and
styrene and determined to have 0.87 g As/mmol by integration of
the 1H NMR spectra, according to the methods described in our
previous report.15a Treatment of 3 with over 20 equiv methyl bro-
moacetate in THF under reflux resulted in a very low yield of NCPS-
(carbomethoxymethyl)triphenylarsonium bromide (1). Although
* Corresponding author. E-mail address: pchiu@hku.hk (P. Chiu).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.09.005

8770
K.C.Y. Lau, P. Chiu / Tetrahedron 67 (2011) 8769e8774
arsonium ylides are more reactive than their corresponding phos-
phonium counterparts, arsonium salts are more difficult to obtain
due to the lower nucleophilicity of arsines.19 Finally, heating 3 with
neat methyl bromoacetate resulted in a homogeneous reaction
mixture, and an excellent yield of 1 was obtained after polymer
precipitation (Scheme 1).20
product 4a (Table 1, entry 3). The reaction did not go to completion
with less than 2 equiv of 1 (Table 1, entry 1 vs 2). While the gen-
eration of the ylide occurred effectively at room temperature, the
subsequent Wittig reaction proceeded at room temperature with
the reactive aldehyde 4a, but required higher temperatures when
4b was substrate (Table 1, entries 2 and 5). Compared with heating,
microwave irradiation did not promote the reaction effectively at
100 ꢁC or 150 ꢁC, with some decomposition of 4b observed under
these conditions.23
O
1
8 n
Br
OMe
Table 1
Optimization of reaction conditions for olefination with 1
70 oC, 3h
98%
O
Ph2As
Br
CO2 Me
O
1 (2.0 equiv), base
R
OMe
R
H
Reaction Conditions
1
4a, R= p-NO2-C6H4-
4b, R= PhCH=CH-
5a, R= p-NO2-C6H4-
5b, R= PhCH=CH-
1
8 n
Entry RCHO Base
Reaction conditions
Yield, %
1
2
3
4
5
6
7
8
9
4a
4a
4a
4b
4b
4b
4b
4b
4b
K2CO3 THF, trace H2O, rt, 2 ha
K2CO3 THF, trace H2O, rt, 15 min
5a, 58
5a, 95
5a, 98
5b, 69
5b, 89
AsPh2
8
n
1
I
3
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
THF, rt, 15 min
THF, rt, 4 h
THF, reflux, 2h
THF, reflux, 1 h
o
5b, 81 (10)b
70 C, 15 h
72%
Ph2As
I
Ph
THF,
DMSO,
m
W,c 25 min
m
5b, 34 (34)b
0
W at 150 ꢁC,c 25 min
K2CO3 THF, trace MeOH,
m
W at 100 ꢁC,c 25 min 0 (100)b
2
a
b
c
Compound 1 (1.1 equiv) was used.
Recovered 4b.
Scheme 1. Synthesis of 1 and 2.
m
W¼250 W.
The degree of alkylation in 1 was determined by 1H NMR in-
tegration and analysis. The methylene group in free [MeO2C-
2.3. One-pot ylide generation-arsa-Wittig reactions with 1
CH2AsPh3]þBr has
a
signal at 5.41 ppm,20 and there is
a corresponding broad peak at
d
5.2e5.6 ppm in the 1H NMR
The one-pot ylide generation-olefination reactions of various 4
were then investigated (Table 2). Except for 4a and 4h, all arsa-
Wittig reactions were conducted with 4 in the presence of
2 equiv of 1, 2 equiv of Et3N, and heated in refluxing THF for the
shown reaction times. Good yields of olefins 5 were generally ob-
tained in this one-pot reaction. As expected, the more electrophilic
and less sterically demanding aldehydes completed reactions in
comparatively less time and with higher yields. The electron-rich
anisaldehyde (4e), and the sterically hindered mesitaldehyde (4g)
reacted to give poor yields of the corresponding enoate products 5e
and 5g. No olefination of cyclopentanone was observed under these
reaction conditions.24
spectrum of 1. From the ratio of the integration of the methylene
protons to the aromatic protons, the loading of arsonium bromide
was determined to be 0.76 mmol/g.21
Attempts to synthesize 2 by treating 3 with neat benzyl bromide
were unsuccessful, and unreacted 3 was largely recovered. When
the more reactive benzyl iodide was used,22 a good yield of 2 was
obtained. As for the analysis of 1, the loading of arsonium iodide on
2 was determined to be 0.72 mmol/g polymer, based on the in-
tegration of the methylene protons of the benzyl group
(d
¼4.7e5.2 ppm) relative to the aromatic protons.21
2.2. Optimization of olefination reactions with 1
Table 2
Olefinations of 4 with 1
Previously, Tao and Hu have synthesized several polystyrene-
supported aroylmethylarsonium salts and isolated the corre-
sponding ylides. Subsequently aryl aldehydes were subjected to
Wittig reactions with these supported-ylides to yield chalcones.18
Our aim in this project was to generate the ylide from 1 and 2 in
situ, to use the ylides directly in a one-pot reaction to streamline
the operations of this arsa-Wittig reaction, and to recycle the
polymer-supported arsine reagent to furnish a more environmen-
tally and economically benign process overall.
We started our investigation of this one-pot arsa-Wittig reaction
with 1 using aldehydes 4a and 4b as substrates. K2CO3 was first
tried as base to generate the arsonium ylide from 1. Although ylide
formation and the subsequent Wittig reaction proceeded well, the
use of K2CO3 necessitated an aqueous workup to isolate the prod-
uct, resulting in additional operations, premature precipitation and
a lower recovery of the polymer. On the other hand, Et3N proved to
be equally effective as a base for generating the ylide, and the by-
product [Et3HN]þBrꢀ could be removed by filtration instead of by
an aqueous workup, which facilitated a full recovery of the polymer
after the reaction, as well as a nearly quantitative yield of Wittig
O
1 (2.0 equiv), Et3N
RCHO
R
OMe
THF reflux
4
5
CO2Me
CO2Me
CO2Me
NO2
R"
5c
5a
5b
:
R"= Me, 14 h: 79%
0.25 ha: 98%
2 h; 89%
5d:R"= Br, 2 h: 89%
5e
:
R"= OMe, 2 h: 29%
CO2Me
CO2Me
CO2Me
n-C6H13
Cl
5f
5g
5h
17 ha,b: 81%
2 h: 85%
4 h: 15%
aReaction at room temperature.
bK2CO3 used as base.

K.C.Y. Lau, P. Chiu / Tetrahedron 67 (2011) 8769e8774
8771
On the other hand, the one-pot reaction with the highly elec-
2.5. Recycling of 1
trophilic 4a proceeded efficiently even at room temperature. In the
case of 4h, reaction under the typical conditions with Et3N in
refluxing THF yielded about 14% self-aldol as a side-product.
However, when the reaction was conducted at room temperature
and with K2CO3 as base, a good yield of 5h was obtained. The yield
of this reaction was comparable to that reported for hexanal,
[MeO2CCH2AsPh3]þBrꢀ, and K2CO3 (82% yield).25 Therefore, the
reactivity of 1 in ylide formation and in the ensuing arsa-Wittig
reaction was similar to that of the free arsonium bromide.
Finally we investigated the feasibility of recycling 1 for reaction.
In the arsa-Wittig reaction, after 1 reacts with an aldehyde, the used
polymer is represented by 7 in which the arsine residues have
undergone reaction have become oxidized (Scheme 2). Polymer 7
was readily isolated as described previously, and was treated with
triphenyl phosphite to reduce the arsine oxide back to the arsine.28
Polymer 8 thus obtained was converted back to 1 by reaction with
methyl bromoacetate as in the original preparation of 1 (Scheme 2).
2.4. One-pot ylide generation-arsa-Wittig reactions with 2
NCPS
RCH=CHCO2Me
RCHO
n
m
We next proceeded to study the reactions of 2, which would typify
that of semi-stabilized arsa-Wittig reagents. Reactions of benzyl-
triphenylarsonium ylides with aldehydes have been reported to yield
epoxides and olefins, the latter being favored in non-polar solvents.26
Ph
1
Br
AsPh2
AsPh2
O
Regardless of their electrophilicity,
4
reacted with
MeO2C
1.9e2.0 equiv of 2 in a biphasic reaction in the presence of 50%
aqueous NaOH and benzene, to give excellent yields of olefins,
with ꢂ5% of epoxides observed in crude 1H NMR of the product
mixture obtained under these conditions (Table 3). Olefination of
both the electron-rich 4e and the sterically demanding 4g pro-
ceeded smoothly to give 6e and 6g, respectively. It is noteworthy
that E-alkenes were exclusively formed in the reactions of all al-
dehydes, highlighting the stereoselectivity offered by arsoranes,
in contrast to the usual formation of a mixture of E/Z isomers in
the phospha-Wittig reaction of semi-stabilized ylides.27 Whereas
the benzylidenation of cyclopentanone by Ph3P]CHPh proceeds
poorly, cyclopentanone was effectively olefinated using 2 in 80%
yield with heating.
7
NCPS
O
m
n
Br
P(OPh)3
Ph
MeO
Recycled 1
70 oC, 3 h
94%
THF, 20 h
95%
Br
AsPh2
AsPh2
MeO2C
8
Scheme 2. Reconstitution of 1.
The reactivity of 1 obtained from this protocol was examined
over several cycles with aldehyde 4d (Table 4). Recycled 1 was
shown to be efficient for the olefination reaction, albeit there was
a slight reduction in the yields. Each reaction was complete in 2 h,
and the efficiency of 1 was maintained over at least three sub-
sequent cycles, showing that a sub-stoichiometric use of arsine was
possible in a large scale arsa-Wittig reaction by recycling of 1.
Table 3
Benzylidenation of 4 with 2
1.9 equiv. 2, 50% NaOH
Ph
RCHO
4
R
PhH, rt
6
t (h); yield
_________________________________________
Ph
Ph
Table 4
Efficiency of recycled 1
R"
Cl
6f: 2 h, 83%
6a: R= NO2: 0.25 h; 89%
O
H
1
2.0 equiv. , Et3N
CO2Me
c
Br
6
: R= Me: 2 h; 86%
Br
THF, reflux
d
6
: R=Br: 2 h; 81%
4d
5d
e
6
: R= OMe: 2 h; 89%
Cycle
Reaction time (h)
Yield, %
1 (Freshly prepared)
2
2
2
2
89
79
81
83
Ph
Ph
n-C6H13
2
3
4
Ph
b
6h
6i:
2 h , 80%
6g
3 h; 83%
17 ha; 81%
3. Conclusion
_________________________________________
aK2CO3 used as base.
bReaction conducted at 70 ꢁC.
From non-cross-linked polystyrene-supported triphenylarsine
3, we have successfully synthesized two recyclable, NCPS-
triphenylarsonium halides, 1 and 2. Arsa-Wittig reactions using
these reagents were executed in one-pot efficiently and with
a similar reactivity compared with the free arsonium salts. The
arsine residues in 1 and 2 are anchored to the polymer support,
thus mitigating the toxicity of the organoarsenic reagents. This
streamlines product isolation by using extraction and filtrations,
rather than by chromatography as operations, and makes recovery
of the arsines practical, preventing the bulk loss of the arsines to the
wastes. Finally, 1 was demonstrated to be recyclable, and therefore
Comparing the results of benzylidenation of 4a, 4d, and 4e using
2 and the corresponding unbound ylide, in which 6a, 6d, and 6e
were reported to be obtained in similar yields of 95%, 81% and 91%,
respectively,26 it can be seen that the immobilization of the arso-
nium salt on the polystyrene support again did not adversely affect
its reactivity in this reaction.
In workup of this reaction, after separation of the aqueous
phase, the polymer could be obtained by precipitation from the
organic layer, with a recovery of about 90%.

8772
K.C.Y. Lau, P. Chiu / Tetrahedron 67 (2011) 8769e8774
a sub-stoichiometric use of arsines in these Wittig reactions is
possible by recycling the reagent. These properties and applications
of 1, 2, and 3 should make reactions involving stoichiometric
amounts of arsines more practicable.
a Buchner funnel, and washed with 3ꢃ10 mL 20% ether/hexane and
set aside. The filtrates and washings were combined and concen-
trated in vacuo, and the residue was purified by silica gel chro-
matography to afford 5b (35.8 mg, 0.190 mmol) in 89% yield as
a white solid. (E)-5-Phenylpenta-2,4-dienoic acid, methyl ester
(5b):29 1H NMR (300 MHz, CDCl3): 3.77 (s, 3H), 6.00 (d, 1H,
J¼15.4 Hz), 6.81e6.94 (m, 2H), 7.27e7.52 (m, 6H) ppm; 13C NMR
(75 MHz, CDCl3): 51.7, 121.0, 126.3, 127.3, 128.9, 129.2, 136.1, 140.7,
145.0, 167.6 ppm.
4. Experimental
4.1. General experimental
Benzyl iodide was synthesized according to the literature,22
and washed with 10% Na2S2O3 to remove I2 before use. Other re-
agents were purchased from Aldrich, Lancaster, Acros or Merck
and used without further purification. Flash column chromatog-
raphy was performed with E. Merck silica gel 60 (230e400 mesh
ASTM). 1H and 13C NMR spectra were recorded in CDCl3 with TMS
as an internal standard at ambient temperature on Bruker Avance
DPX300, AV400 or DRX500 spectrometers, operating at 300 MHz,
400 MHz or 500 MHz for 1H NMR, and 75 MHz, 100 MHz or
125 MHz for 13C NMR. IR spectra were recorded on a Bio-Rad FT-IR
spectrometer. All products were known compounds, and their
spectral properties were identical to those reported in the
literature.
4.3.1. (E)-3-(4-Nitrophenyl)acrylic acid, methyl ester (5a)30. Follo-
wing the typical procedure, but stirring at room temperature for
15 min, the reaction of 4a (37.8 mg, 0.250 mmol) yielded 5a
(51.3 mg, 0.248 mmol, 98% yield) as a white solid; 1H NMR
(400 MHz, CDCl3): 3.83 (s, 3H), 6.56 (d, 1H, J¼16.1 Hz), 7.66 (d, 2H,
J¼8.7 Hz), 7.71 (d, 1H, J¼16.1 Hz), 8.24 (d, 2H, J¼8.8 Hz) ppm; 13C
NMR (100 MHz, CDCl3): 52.2, 122.2, 124.3, 128.8, 140.6, 142.0, 148.6,
166.6 ppm.
4.3.2. (E)-3-(p-Tolyl)acrylic acid methyl ester (5c)31. Following the
typical procedure, the reaction of 4c (37.5 mg, 0.229 mmol) yielded
5c (32.0 mg, 0.182 mmol, 79% yield) as a white solid; 1H NMR
(300 MHz, CDCl3): 2.37 (s, 3H), 3.80 (s, 3H), 6.40 (d, 1H, J¼16.0 Hz),
7.19 (d, 2H, J¼8.0 Hz), 7.42 (d, 2H, J¼8.1 Hz), 7.67 (d, 1H, J¼16.0 Hz)
ppm; 13C NMR (75 MHz, CDCl3): 21.6, 51.8, 116.9, 128.2, 129.8, 131.8,
140.9, 145.0, 167.8 ppm.
4.2. Synthesis of 1 and 2
4.2.1. Synthesis of NCPS-(carbomethoxymethyl)triphenylarsonium
bromide (1). NCPS-triphenylarsine (3) (2.0 g, 1.7 mmol) was dis-
solved in 5.0 mL methyl bromoacetate. The reaction mixture was
heated in a 70 ꢁC oil bath for 3 h under argon. Excess methyl
bromoacetate in the reaction mixture was removed by vacuum
distillation until a pale brown residue was left. THF (5.0 mL) was
added to dissolve the residue, and this solution was poured into
150 mL hexane for polymer precipitation. The precipitated poly-
mer was collected by suction filtration using filter paper on
a Buchner funnel, washed with 3ꢃ15 mL hexane, and dried in
vacuo over P2O5 to afford 1 as a white solid (2.243 g, 1.72 mmol,
98%). 1H NMR (300 MHz, CDCl3): 0.82e2.38 (br m, 26H), 3.73e3.95
(br m, 3H), 5.20e5.58 (br m, 2H), 6.20e7.25 (br m, 38.5H),
7.52e7.91 (br m, 14H) ppm; IR (CHCl3): 3063, 3030, 3009, 2958,
2930, 1733, 1602, 1494, 1454, 1441, 1304, 1215, 1085, 845, 782, 767,
4.3.3. (E)-3-(4-Bromophenyl)acrylic acid methyl ester (5d)32. Follo-
wing the typical procedure, the reaction of 4d (25.7 mg, 0.194 mmol)
yielded 5d (43 mg, 0.178 mmol, 89%) as a white solid; 1H NMR
(300 MHz, CDCl3): 3.80 (s, 3H), 6.42 (d, 1H, J¼16.0 Hz), 7.37 (d, 2H,
J¼8.5 Hz), 7.51 (d, 2H, J¼8.5 Hz), 7.61 (d, 1H, J¼16.0 Hz) ppm; 13C
NMR (75 MHz, CDCl3): 52.0, 118.7, 124.7, 129.6, 132.3, 133.4, 143.6,
167.3 ppm.
4.3.4. (E)-3-(4-Methoxyphenyl)acrylic acid methyl ester (5e)33. Follo-
wing the typical procedure, the reaction of 4e (28.0 mg, 0.205 mmol)
yielded 5e (11.4 mg, 0.059 mmol, 29%) as a white solid; 1H NMR
(300 MHz, CDCl3): 3.79 (s, 3H), 3.84 (s, 3H), 6.31 (d, 1H, J¼16.0 Hz),
6.90 (d, 2H, J¼8.8 Hz), 7.47 (d, 2H, J¼8.7 Hz), 7.65 (d, 1H, J¼16.0 Hz)
ppm; 13C NMR (75 MHz, CDCl3): 51.7, 55.5, 114.5, 115.5, 127.3, 129.9,
144.7, 161.6, 167.9 ppm.
754, 732 cmꢀ1
.
4.2.2. Synthesis of NCPS-benzyltriphenylarsonium iodide (2). NCPS-
triphenylarsine (3) (2.0 g, 1.7 mmol) was dissolved in 4.0 mL benzyl
iodide.22 The reaction mixture was heated in a 70 ꢁC oil bath for
15 h under argon. CH2Cl2 (30 mL) was added to the reaction mix-
ture, and the organics were washed with 3ꢃ15 mL 10% aqueous
sodium thiosulfate solution. The bulk of the CH2Cl2 was removed
under reduced pressure, and the residue was poured into 150 mL
hexane for polymer precipitation. The precipitated polymer was
collected by suction filtration using filter paper on a Buchner fun-
nel, washed with 3ꢃ15 mL hexane, and dried in vacuo over P2O5 to
afford 2 as a white solid (1.71 g,1.27 mmol, 72%). 1H NMR (400 MHz,
CDCl3): 1.20e2.13 (br m, w26H) 4.71e5.17 (br m, w2H), 6.28e7.20
(br m, w43H), 7.40e7.80 (br m, w14H) ppm; IR (CHCl3): 3083,
3062, 3029, 3010, 2929, 2852, 1602, 1494, 1454, 1441, 1235, 1220,
4.3.5. (E)-3-(3-Chlorophenyl)acrylic acid methyl ester (5f)34. Follo-
wing the typical procedure, the reaction of 4f (36.0 mg,
0.256 mmol) yielded 5f (42.8 mg, 0.218 mmol, 85%) as a white
solid; 1H NMR (400 MHz, CDCl3): 3.80 (s, 3H), 6.43 (d, 1H,
J¼16.0 Hz), 7.28e7.40 (m, 3H), 7.41e7.52 (m, 1H), 7.61 (d, 1H,
J¼16.0 Hz) ppm; 13C NMR (100 MHz, CDCl3): 51.9, 119.4, 126.4,
127.9, 130.2, 130.3, 135.0, 136.3, 143.3, 167.1 ppm.
4.3.6. (E)-3-(2,4,6-Trimethylphenyl)acrylic acid methyl ester (5g)35. Fo-
llowing the typical procedure, the reaction of 4g (34.8 mg,
0.235 mmol) yielded 5g (7.2 mg, 0.035 mmol, 15%) as a white solid;
1H NMR (500 MHz, CDCl3): 2.28 (s, 3H), 2.33 (s, 6H), 3.81 (s, 3H), 6.06
(d, 1H, J¼16.4 Hz), 6.89 (s, 2H), 7.85 (d, 1H, J¼16.4 Hz) ppm; 13C NMR
(125 MHz, CDCl3): 21.2, 21.2, 51.8, 123.0, 129.3, 131.1, 137.0, 138.5,
143.6, 167.6 ppm.
1210, 1186, 1084, 909, 825 cmꢀ1
.
4.3. Typical procedure for olefinations of 4 using 1
4.3.7. (E)-Non-2-enoic acid methyl ester (5h)36. Following the typ-
ical procedure, but using K2CO3 as base and a solvent mixture of
THF (2.0 mL) and water (0.23 mL), the reaction of 4h (43.5 mg,
0.381 mmol) at room temperature yielded 5i (52.6 mg,
0.309 mmol, 81%) as a colorless oil; 1H NMR (400 MHz, CDCl3):
0.83e0.88 (m, 3H), 1.22e1.45 (m, 8H), 2.14e2.20 (m, 2H), 3.70 (s,
3H), 5.79 (dt, 1H, J¼15.6, 1.6 Hz), 6.95(dt, 1H, J¼15.6, 7.0 Hz) ppm;
To a solution of 4b (0.0283 g, 0.214 mmol) in 2.0 mL THF were
added 1 (0.564 g, 0.428 mmol) and Et3N (0.06 mL, 0.43 mmol). The
reaction mixture was heated in a 70 ꢁC oil bath for 2 h. The white
solids [Et3NH]þBrꢀ were removed by suction filtration. This filtrate
was concentrated and poured into 60 mL of 20% ether/hexane. The
precipitated polymer 7 was collected by suction filtration on

K.C.Y. Lau, P. Chiu / Tetrahedron 67 (2011) 8769e8774
8773
13C NMR (100 MHz, CDCl3): 14.1, 22.6, 28.1, 28.9, 31.7, 32.3, 51.4,
120.9, 149.9, 167.3 ppm.
1.31e1.54 (m, 8H), 2.18e2.26 (m, 2H), 6.24 (dt, 1H, J¼15.8, 6.8 Hz),
6.39 (d, 1H, J¼15.9 Hz), 7.16e7.23 (m, 1H), 7.26e7.38 (m, 4H) ppm;
13C NMR (75 MHz, CDCl3): 14.3, 22.8, 29.1, 29.5, 31.9, 33.2, 126.1,
126.9, 128.6, 129.8, 131.4, 138.1 ppm.
4.4. Typical procedure for olefinations of 4 using 2
4.4.1. (E)-4-Nitrostilbene (6a)37. Polymer 2 (0.54 g, 0.39 mmol) and
4a (30.2 mg, 0.200 mmol) were dissolved in 2.0 mL benzene.
Aqueous 50% NaOH was added and the reaction mixture was stirred
at room temperature. After 0.25 h, 10.0 mL benzene was added and
the aqueous layer was separated and discarded. The organic layer
was washed with 2ꢃ10 mL H2O, and concentrated in vacuo. THF
(1.0 mL) was added to dissolve the residue, which was then poured
into 60 mL of 20% ether/hexane. The polymer was collected by
suction filtration on filter paper using a Buchner funnel, and
washed with 3ꢃ10 mL 20% ether/hexane. The filtrate and washings
were combined, concentrated in vacuo, and the residue was puri-
fied by silica gel chromatography to afford 6a as a pale yellow solid
(40.1 mg, 0.178 mmol, 89%); 1H NMR (500 MHz, CDCl3): 7.15 (d, 1H,
J¼16.3 Hz), 7.25e7.30 (m,1H), 7.32e7.35 (m,1H), 7.38e7.42 (m, 2H),
7.55 (d, 2H, J¼7.3 Hz), 7.64 (d, 2H, J¼8.8 Hz), 8.21e8.24 (m, 2H)
ppm; 13C NMR (125 MHz, CDCl3): 124.2, 126.3, 126.9, 127.0, 128.9,
128.9, 133.4, 136.2, 143.9, 146.8 ppm.
4.4.8. Cyclopentylidenemethylbenzene (6i)44. Following the typical
procedure, but with heating in a 70 ꢁC oil bath, the reaction of 4i
(37.0 mg, 0.440 mmol) yielded 6i (56.4 mg, 0.356 mmol, 80%) as
a colorless oil; 1H NMR (500 MHz, CDCl3): 1.63e1.70 (m, 2H),
1.75e1.81 (m, 2H), 2.47e2.51 (m, 2H), 2.53e2.57 (m, 2H), 6.35e6.37
(m, 1H), 7.13e7.17 (m, 1H), 7.29e7.33 (m, 4H) ppm; 13C NMR
(125 MHz, CDCl3): 25.6, 27.2, 31.2, 36.0, 120.8, 125.6, 127.9, 128.2,
138.9, 147.2 ppm.
4.5. Recycling of 1
4.5.1. Reduction of 7. Polymer 7 (1.02 g, z0.80 mmol) was dis-
solved in 4.0 mL THF and treated with triphenyl phosphite
(0.4960 g, 1.60 mmol). The reaction mixture was stirred at room
temperature for 20 h, then poured into 20% ether/hexane. The
precipitated polymer was collected by suction filtration, and
washed with 3ꢃ15 mL 20% ether/hexane, dried in vacuo over P2O5
to afford 8 (0.921 g, z0.76 mmol, 95%).
4.4.2. (E)-4-Methylstilbene (6c)38. Following the typical procedure,
the reaction of 4c (36.1 mg, 0.300 mmol) yielded 6c (50.0 mg,
0.257 mmol, 86%) as a white solid; 1H NMR (500 MHz, CDCl3): 2.37
(s, 3H), 7.07e7.09 (m, 2H), 7.17 (d, 2H, J¼8.0 Hz), 7.23e7.25 (m, 1H),
7.33e7.37 (m, 2H), 7.42 (d, 2H, J¼8.1 Hz), 7.49e7.52 (m, 2H) ppm;
13C NMR (125 MHz, CDCl3): 21.4, 126.5, 126.6, 127.5, 127.9, 128.8,
128.8, 129.5, 134.7, 137.7, 137.7 ppm.
Acknowledgements
We thank Mr. John Chun Kit Chu for editorial and technical as-
sistance. This research was supported financially by the University
of Hong Kong and the Research Grants Council of the Hong Kong
Special Administrative Region, PR of China (HKU 7107/04P, 7017/
09P).
4.4.3. (E)-4-Bromostilbene (6d)39. Following the typical procedure,
the reaction of 4d (29.8 mg, 0.161 mmol) yielded 6d (33.8 mg,
0.130 mmol, 81%) as a white solid; 1H NMR (500 MHz, CDCl3): 7.03
(d, 1H, J¼16.3 Hz), 7.10 (d, 1H, J¼16.4 Hz), 7.26e7.30 (m, 1H),
7.34e73.39 (m, 4H), 7.46e7.53 (m, 4H) ppm; 13C NMR (125 MHz,
CDCl3): 121.3, 126.6, 127.4, 127.9, 128.0, 128.8, 129.5, 131.8, 136.3,
137.0 ppm.
Supplementary data
1H NMR spectra of polymers 1 and 2, and the calculations of
their arsonium salt loadings. Supplementary data associated with
this article can be found, in the online version, at doi:10.1016/
j.tet.2011.09.005.
4.4.4. (E)-4-Methoxystilbene (6e)40. Following the typical pro-
cedure, the reaction of 4e (39.5 mg, 0.290 mmol) yielded 6e
(54.6 mg, 0.260 mmol, 89%) as a white solid; 1H NMR (300 MHz,
CDCl3): 3.84 (s, 3H), 6.89e7.11 (m, 4H), 7.20e7.26 (m,1H), 7.32e7.38
(m, 2H), 7.44e7.51 (m, 4H) ppm; 13C NMR (75 MHz, CDCl3): 55.5,
114.3, 126.4, 126.8, 127.4, 127.9, 128.4, 128.8, 130.3, 137.8, 159.4 ppm.
References and notes
1. (a) Aggarwal, V. K.; Patel, M.; Studley, J. Chem. Commun. 2002, 1514e1515; (b)
€
Faust, R.; Gobelt, B. J. Prakt. Chem. 1998, 340, 90e93; (c) Farina, V.; Krishnan, B. J.
Am. Chem. Soc. 1991, 113, 9585e9595; (d) Farina, V.; Krishnan, B.; Marshall, D.
R.; Roth, G. P. J. Org. Chem. 1993, 58, 5434e5444; (e) Bedford, R. B.; Betham, M.;
Bruce, D. W.; Danopoulos, A. A.; Frost, R. M.; Hird, M. J. Org. Chem. 2005, 71,
1104e1110; (f) Hennings, D. D.; Iwama, T.; Rawal, V. H. Org. Lett. 1999, 1,
1205e1208; (g) Kawatsura, M.; Ikeda, D.; Ishii, T.; Komatsu, Y.; Uenishi, J. Synlett
2006, 2435e2438.
2. (a) Lloyd, D.; Gosney, I.; Ormiston, R. A. Chem. Soc. Rev. 1987, 16, 45e74; (b) He,
H. S.; Chung, C. W. Y.; But, T. Y. S.; Toy, P. H. Tetrahedron 2005, 61, 1385e1405.
3. (a) Zhou, D.; Ren, Z.; Cao, W.; Chen, J.; Liu, Y.; Deng, H.; Shao, M. J. Heterocycl.
Chem. 2010, 47, 1116e1122; (b) Wang, H.; Chen, Y.; Cao, W.; Ding, H.; Chen, J.;
Deng, H.; Shao, M. Synthesis 2008, 3995e4001; (c) Yu, H.; Liu, Y.; Zhang, H.;
Chen, J.; Deng, H.; Shao, M.; Ren, Z.; Cao, W. Tetrahedron 2010, 66, 2598e2601;
(d) Zhao, Y.-H.; Zheng, C.-W.; Zhao, G.; Cao, W.-G. Tetrahedron: Asymmetry
2008, 19, 701e708.
4. (a) Ousset, J. B.; Mioskowski, C.; Solladie, G. Tetrahedron Lett. 1983, 24,
4419e4422; (b) Still, W. C.; Novack, V. J. J. Am. Chem. Soc. 1981, 103, 1283e1285;
(c) Boubia, B.; Mioskowski, C.; Manna, S.; Falck, J. R. Tetrahedron Lett. 1989, 30,
6023e6026.
5. Li, A.-H.; Dai, L.-X.; Hou, X.-L.; Chen, M.-B. J. Org. Chem. 1996, 61, 4641e4648.
6. Zhu, S.; Liao, Y.; Zhu, S. Org. Lett. 2004, 6, 377e380.
4.4.5. (E)-3-Chlorostilbene (6f)41. Following the typical procedure,
the reaction of 4f (32.8 mg, 0.233 mmol) yielded 6f (41.7 mg,
0.194 mmol, 83%) as a white solid; 1H NMR (300 MHz, CDCl3): 7.03
(d, 1H, J¼16.3 Hz), 7.12 (d, 1H, J¼16.3 Hz), 7.20e7.25 (m, 1H),
7.26e7.40 (m, 5H), 7.50e7.53 (m, 3H) ppm; 13C NMR (75 MHz,
CDCl3): 124.9, 126.5, 126.8, 127.4, 127.6, 128.2, 128.9, 130.0, 130.3,
134.8, 137.0, 139.4 ppm.
4.4.6. (E)-2,4,6-Trimethylstilbene (6g)42. Following the typical pro-
cedure, the reaction of 4g (32.3 mg, 0.218 mmol) yielded 6g
(40.2 mg, 0.181 mmol, 83%) as a white solid; 1H NMR (300 MHz,
CDCl3): 2.35 (s, 3H), 2.40 (s, 6H), 6.64 (d, 1H, J¼16.6 Hz), 6.96 (s,
2H), 7.15 (d, 1H, J¼16.6 Hz), 7.29e7.35 (m, 1H), 7.39e7.44 (m, 2H),
7.55 (d, 2H, J¼7.4 Hz) ppm; 13C NMR (75 MHz, CDCl3): 21.1, 21.1,
126.4, 127.1, 127.6, 128.8, 128.9, 133.8, 134.1, 136.3, 136.4, 137.9 ppm.
7. (a) Huang, Z.; Lan, G.-C.; Huang, X. Synth. Commun. 1998, 28, 633e637; (b)
Huang, Z.; Yu, X.; Huang, X. J. Org. Chem. 2002, 67, 8261e8264.
8. (a) Chen, Z.; Zhang, J.; Chen, J.; Deng, H.; Shao, M.; Zhang, H.; Cao, W. Tetra-
hedron 2010, 66, 6181e6187; (b) Wu, X.; Cao, W.; Zhang, H.; Chen, J.; Jiang, H.;
Deng, H.; Shao, M.; Zhang, J.; Chen, H. Tetrahedron 2008, 64, 10331e10338; (c)
Mitsumoto, Y.; Nitta, M. J. Chem. Soc., Perkin Trans. 1 2002, 2268e2274.
9. Seyer, A.; Alcaraz, L.; Mioskowski, C. Tetrahedron Lett. 1997, 38, 7871e7874.
10. Dai, W.-M.; Wu, A.; Wu, H. Tetrahedron: Asymmetry 2002, 13, 2187e2191.
4.4.7. (E)-Hept-1-enylbenzene (6h)43. Following the typical pro-
cedure, but using K2CO3 as base in water, the reaction of 4h
(33.6 mg, 0.294 mmol) yielded 6h (52.2 mg, 0.277 mmol, 81%) as
a colorless oil; 1H NMR (300 MHz, CDCl3): 0.88e0.93 (m, 3H),

8774
K.C.Y. Lau, P. Chiu / Tetrahedron 67 (2011) 8769e8774
11. (a) Boubia, B.; Mann, A.; Bellamy, F. D.; Mioskowski, C. Angew. Chem., Int. Ed.
Engl. 1990, 29, 1454e1456; (b) Wei-Min, D.; Jinlong, W.; Xian, H. Tetrahedron:
Asymmetry 1997, 8, 1979e1982.
24. The arsonium Wittig reaction with cyclopentanone may be successful at higher
reaction temperatures, see: Wu, J.; Li, D.; Wu, H.; Dai, W.-M. Tetrahedron 2006,
62, 4643e4650.
12. Habrant, D.; Stengel, B.; Meunier, S.; Mioskowski, C. Chem.dEur. J. 2007, 13,
5433e5440.
25. Shi, L.; Xiao, W.; Ge, Y.; Huang, Y. Acta Chim. Sin. 1986, 44, 421e423.
26. These experiments were done with [Ph3AsCH2Ph]þBrꢀ: Tao, W.; Zhou, X.; Feng,
Y.; Zhai, J. Huaxue Shiji 1993, 15, 193e196.
27. (a) McKenna, E. G.; Walker, B. J. Tetrahedron Lett. 1988, 29, 485e488; (b) Ac-
kermann, M.; Berger, S. Tetrahedron 2005, 61, 6764e6771; (c) Raeck, C.; Berger,
S. Eur. J. Org. Chem. 2006, 4934e4937; (d) Wu, J.; Li, D.; Zhang, D. Synth.
Commun. 2005, 35, 2543e2551.
13. (a) Cao, P.; Li, C.-Y.; Kang, Y.-B.; Xie, Z.; Sun, X.-L.; Tang, Y. J. Org. Chem. 2007, 72,
6628e6630; (b) Shi, L.; Wang, W.; Wang, Y.; Huang, Y. J. Org. Chem. 1989, 54,
2027e2028; (c) Smith, C. P.; Temme, G. H. J. Org. Chem. 1983, 48, 4681e4685.
14. Huang, Y.; Shen, Y. In Adv. Organomet. Chem.; Stone, F. G. A., Robert, W., Eds.;
Academic: New York, 1982; pp 115e157.
15. (a) Lau, K. C. Y.; He, H. S.; Chiu, P.; Toy, P. H. J. Comb. Chem. 2004, 6, 955e960; (b)
Song He, H.; Zhang, C.; Ng, C. K.-W.; Toy, P. H. Tetrahedron 2005, 61,
12053e12057; (c) Lau, K. C. Y.; Chiu, P. Tetrahedron Lett. 2007, 48, 1813e1816;
(d) Steiner, U. B.; Caseri, W. R.; Suter, U. W. Langmuir 1998, 14, 347e351; (e)
Miller, J. A.; Knox, L. K. J. Chem. Soc., Chem. Commun. 1994, 1449e1450.
16. (a) Cai, M.; Huang, Y.; Zhao, H.; Song, C. React. Funct. Polym. 2004, 59, 81e86; (b)
Cai, M.; Huang, Y.; Zhao, H.; Zhang, R. J. Organomet. Chem. 2004, 689,
2436e2440; (c) Cai, M.; Huang, Y.; Hu, R.; Song, C. J. Mol. Catal. A: Chem. 2004,
212, 151e154; (d) Liu, G.; Cai, M. J. Mol. Catal. A: Chem. 2006, 258, 257e260.
17. For selected reviews on the use of polymer supports in organic synthesis, see
(a) Lu, J.; Toy, P. H. Chem. Rev. 2009, 109, 815e838; (b) Bergbreiter, D. E.; Tian, J.;
Hongfa, C. Chem. Rev. 2009, 109, 530e582; (c) Solinas, A.; Taddei, M. Synthesis
2007, 2409e2453.
18. (a) Tao, W.; Hu, X. Huaxue Shiji 1983, 5, 15e17; (b) Tao, W.; Hu, X. Huaxue Shiji
1984, 6, 207e209; (c) Tao, W.; Hu, X. Huaxue Shiji 1982, 4, 197e199.
19. Horner, L.; Hofer, W.; Ertel, I.; Kunz, H. Chem. Ber. 1970, 103, 2718e2728.
20. Moorhoff, C. M. Synth. Commun. 1998, 28, 2925e2935.
21. The Supplementary data contains the detailed calculations.
22. Di Deo, M.; Marcantoni, E.; Torregiani, E.; Bartoli, G.; Bellucci, M. C.; Bosco, M.;
Sambri, L. J. Org. Chem. 2000, 65, 2830e2833.
28. Lu, X.; Wang, Q.; Tao, X.; Sun, J.; Lei, G. Acta Chim. Sin. 1985, 43, 450e453.
29. O’Donnell, M. E.; Sanvoisin, J.; Gani, D. J. Chem. Soc., Perkin Trans. 1 2001,
1696e1708.
30. Huang, X.; Xie, L.; Wu, H. J. Org. Chem. 1988, 53, 4862e4864.
31. Xiong, Z.; Wang, N.; Dai, M.; Li, A.; Chen, J.; Yang, Z. Org. Lett. 2004, 6, 3337e3340.
32. Dai, M.; Liang, B.; Wang, C.; Chen, J.; Yang, Z. Org. Lett. 2004, 6, 221e224.
33. McNulty, J.; Capretta, A.; Laritchev, V.; Dyck, J.; Robertson, A. J. J. Org. Chem.
2003, 68, 1597e1600.
34. Ruan, J.; Li, X.; Saidi, O.; Xiao, J. J. Am. Chem. Soc. 2008, 130, 2424e2425.
35. Felpin, F.-X.; Fouquet, E.; Zakri, C. Adv. Synth. Catal. 2008, 350, 2559e2565.
36. Deng, G.; Xu, B.; Liu, C. Tetrahedron 2005, 61, 5818e5821.
37. Tian, J.; Moeller, K. D. Org. Lett. 2005, 7, 5381e5383.
38. Ishizuka, K.; Seike, H.; Hatakeyama, T.; Nakamura, M. J. Am. Chem. Soc. 2010,
132, 13117e13119.
ꢀ
39. Aydin, J.; Larsson, J. M.; Selander, N.; Szaboc, K. L. N. J. Org. Lett. 2009, 11,
2852e2854.
40. Li, S.; Lin, Y.; Xie, H.; Zhang, S.; Xu, J. Org. Lett. 2006, 8, 391e394.
41. Kabalka, G. W.; Tejedor, D.; Li, N.-S.; Malladi, R. R.; Trotman, S. Tetrahedron 1998,
54, 15525e15532.
42. Barder, T. E.; Walker, S. D.; Martinelli, J. R.; Buchwald, S. L. J. Am. Chem. Soc.
2005, 127, 4685e4696.
23. For examples of microwave-promoted Wittig reactions, see: (a) Frattini, S.;
Quai, M.; Cereda, E. Tetrahedron Lett. 2001, 42, 6827e6829; (b) Westman, J. Org.
Lett. 2001, 3, 3745e3747.
43. Wang, Z.; Zhang, G.; Guzei, I.; Verkade, J. G. J. Org. Chem. 2001, 66, 3521e3524.
44. Zhou, Z.; Larouche, D.; Bennett, S. M. Tetrahedron 1995, 51, 11623e11644.