Novel imidazolium ion-tagged Ru-carbene complexes: synthesis and applications for olefin metathesis in ionic liquid

Article abstract of DOI:10.1016/j.tet.2009.02.043

Novel Hoveyda-type Ru-carbene complexes 7a,b and 8a,b tethering imidazolium tags at chelating isopropoxy group have been synthesized, and investigated their catalytic activities and recyclabilities in ring-closing metathesis (RCM) and cross metathesis (CM

Full text of DOI:10.1016/j.tet.2009.02.043

Tetrahedron 65 (2009) 3397–3403
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Novel imidazolium ion-tagged Ru-carbene complexes: synthesis and applications
for olefin metathesis in ionic liquid
,
Shu-Wei Chen a, Ju Hyun Kim a, Ka Yeon Ryu a, Won-Woong Lee b, Jongki Hong b, Sang-gi Lee a
*
a Department of Chemistry and Nano Science (BK21), Ewha Womans University, Seoul 120-750, Republic of Korea
b College of Pharmacy, Kyung Hee Univeristy, Seoul 130-701, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel Hoveyda-type Ru-carbene complexes 7a,b and 8a,b tethering imidazolium tags at chelating iso-
propoxy group have been synthesized, and investigated their catalytic activities and recyclabilities in
ring-closing metathesis (RCM) and cross metathesis (CM) in ionic liquids. They showed excellent cata-
lytic activities for RCM of various dienes in [bmim][PF6]/CH2Cl2 (1/1, v/v). The recyclability of these
catalysts is largely dependent on the tether length and the structures of imidazolium tag and ionic liquid,
as well as the composition of the ionic solvent system. A combination of the 2-methylated imidazolium
ion-tagged Ru-complex 7b with a mixture of [bdmim][PF6]/toluene (1/3, v/v) allowed several times
recycling without significant loss of catalytic activity in RCM, however low recyclabilities were observed
in CMs.
Received 15 December 2008
Received in revised form 17 February 2009
Accepted 18 February 2009
Available online 26 February 2009
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
the use of imidazolium ion-tagged catalyst, which could retain in
ionic liquid layer more effectively. Numbers of different imidazo-
Olefin metathesis has become one of the simplest and effective
synthetic methods for the construction of carbon–carbon double
bonds, and is widely employed in a variety of fields of chemistry
including natural products, pharmaceuticals, and polymer chem-
istry.1 The spectacular recent success of olefin metathesis stems
largely from the availability of several, well-defined Ru-catalysts
such as Grubbs’ Ru-benzylidenes 1 and Hoveyda’s Ru-complexes 2,
which are easy to handle and tolerant toward different kinds of
functional groups (Fig. 1).
Despite the widespread use of Ru-catalyzed metathesis, a major
disadvantage is difficulty in the recovery and reuse of the expensive
catalysts, as well as the product contamination caused by metal
leaching. Hence, from an economic and environmental point of
view, development of immobilization technology for recycling of
the catalyst is of great importance.2 In this context, the recently
emerged room-temperature ionic liquids (RTILs) hold great po-
tential. Given for characteristic properties of non-volatility, tunable
immiscibility with organic solvents, and ability to dissolve organ-
ometallic compounds, RTILs have been utilized in many different
kinds of reactions for catalyst recycling.3 However, the recovered
Ru-catalysts immobilized in ionic liquid layer rapidly lose their
activity in subsequent runs, which has been ascribed largely to the
leaching of the catalyst into the organic solvent used for product
extraction.4 An elegant solution to solve this leaching problem is
lium ion-tagged Hoveyda-type Ru-complexes such as 3–6 have
been designed and synthesized for olefin metathesis in ionic liquids
(Fig. 2).5–7 It has been observed that the catalytic activity and
recyclability of the imidazolium ion-tagged Ru-complexes were
largely dependent on the positions of imidazolium tag. For exam-
ples, both catalysts 3 and 4 tagging the imidazolium moiety para-
position of chelating isopropoxy showed excellent recyclability
with moderate activity.5,6 However, much lower activity and
recyclability have been observed with the catalyst 5 when the
imidazolium tag anchored onto the chelating ortho oxygen atom.
On changing the tagging position of imidazolium tag to the meta-
position of the styrenylidene ligand, the activity was increased, but
the recyclability was decreased.7
During our ongoing studies on the development of recyclable
olefin metathesis catalysts,8 we have interest to evaluate other
possibilities of anchoring imidazolium ionic tags onto the che-
lating isopropoxy group. In order to investigate the effects of
L
L
Cl
Cl
Ru
O
Cl
Cl
Ru
PCy3
Ph
1
2
a: L = PCy3
b: L = MesN
NMes
..
* Corresponding author. Tel.: þ82 2 3277 4505; fax: þ82 2 3277 3419.
E-mail address: sanggi@ewha.ac.kr (S.-gi Lee).
Figure 1. Grubbs and Hoveyda’s Ru-complexes for olefin metathesis.
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.02.043

3398
S.-W. Chen et al. / Tetrahedron 65 (2009) 3397–3403
moiety, the chloride 11 was reacted with an excess amount
Cl
Cl
Ru PCy3
Cl
Cl
Ru L
Me
Me
N
N
N
(2 equiv) of 1-methylimidazole for 12a and 1,2-dimethylimidazole
for 12b in CH3CN for 36 h at 70 ꢀC to afford the corresponding
imidazolium chlorides 12a and 12b in 91% and 93%, respectively.
The chloride anion was exchanged with NaPF6 to give the
O
O
O
X
PF
Me
6
5
PF6
Cl
Cl
Ru PCy3
1-methylimidazolium
and
1,2-dimethylimidazolium
hexa-
Me
PF6
O
N
N
Me
n
fluorophosphate-tagged styrenyl 13a and 13b in almost quanti-
tative yield. Compounds 13a and 13b were then reacted with
Grubbs 2nd-generation catalyst 1b in the presence of CuCl, and
purified by silica column chromatography followed by solidifying
with a mixture of CH2Cl2/pentane (1/1, v/v) to provide the pure
imidazolium ion-tagged Ru-complexes 7a (72%) and 7b (78%) as
air-stable, greenish powder. In order to investigate the effects of
tether length on the activity and recyclability, the Ru-complexes
8a,b tethering imidazolium tag onto chelating isopropoxy group
directly were synthesized. For the synthesis of 8a and 8b, the
hydroxy group of 10 was converted to the bromide 14 through the
mesylation followed by nucleophilic substitution with LiBr in two
steps 85% yield. The remaining synthetic steps are the same as
those followed for the synthesis of 7a,b. Thus, starting from the
bromide 14, both the ionic complex 8a and 8b were prepared in
three steps with overall yields of 77% and 78%. In NMR analyses,
the characteristic Ru]CH resonance signals were observed at
16.62 ppm for 7a, 16.57 ppm for 7b, 16.64 ppm for 8a, 16.57 ppm
for 8b in 1H NMR and 296.4 ppm for 7a, 296.6 ppm for 7b,
297.4 ppm for 8a, 296.6 ppm for 8b in 13C NMR spectra. In HRMS
analyses, the parent peaks, m/z¼924.2074 for 7a and
m/z¼938.2231 for 7b, were also detected indicating clearly for-
mation of the desired Ru-complexes.
N
3: X = O, n = 3
4: X = CH2, n = 1
6
L = PCy3 and
MesN .. NMes
Figure 2. Imidazolium-tagged Ru-complexes.
structure and tagging position of imidazolium moiety on catalytic
activity, two different types of Ru-complexes 7a,b and 8a,b have
been designed. Herein, we report the synthesis of imidazolium
ion-tagged Ru-carbene complexes 7a,b and 8a,b and their cata-
lytic activities for olefin metathesis in ionic liquid-based solvent
systems.
2. Results and discussion
2.1. Synthesis of imidazolium ion-tagged Ru-complexes 7a,b
and 8a,b
The Ru-complexes 7a,b and 8a,b could be synthesized effi-
ciently in seven steps starting from the commercially available
(E/Z)-2-propenylphenol and methyl 2-bromopropionate (Scheme
1). The Ru-complexes 7a and 7b were synthesized first. Reaction
of (E/Z)-2-propenylphenol with methyl 2-bromopropionate affor-
ded the ester-functionalized olefin 9 in 93% yield.9 The ester was
reduced with LAH to give alcohol 10 in 98%, which has been used
as key intermediate for the synthesis of both 7 and 8. The alcohol
10 was reacted with 1-bromo-4-chlorobutane to afford the chlo-
rinated ether 11 in 90% yield. To introduce the imidazolium
2.2. Olefin metathesis in ionic liquids using imidazolium ion-
tagged Ru-complexes 7a,b and 8a,b
First, we investigated the effects of counter anion of ionic liquid
on the catalytic activity using 7a. Thus, the RCM reactions of the
benchmark substrate, N,N-bisallyl-p-toluenesulfonamide 17a were
i) MsCl, Et3N,
Br
MeO
OH
HO
O
CH2Cl2,
RT, 3 h
O
O
Br
CO2Me
LiAlH4
O
ii) LiBr, DMF/THF
RT, 12 h
K2CO3/cat.Cs2CO3
DMF, RT, 10 h
93%
THF, 0 °C
1 h, 97%
85% (2 steps)
9
10
14
NaH
Br-(CH2)4-Cl
DMF, RT
48 h, 90%
CH3CN
70 °C, 36 h
1-methylimidazole for 15a
1,2-dimethylimidazole for 15b
Me
N
N
O
O
Cl
O
Me
N
N
1-methylimidazole for 12a
O
O
4
4
1,2-dimethylimidazole for 12b
R
R
X
X
CH3CN, 70 °C, 36 h
11
12a: X = Cl, R = H (91%)
12b: X = Cl, R = Me (93%)
15a: X = Br, R = H (96%)
15b: X = Br, R = Me (94%)
NaPF6
NaPF6
CH3CN
RT, 12 h
CH3CN
RT, 12 h
13a: X = PF6, R = H (98%)
13b: X = PF6, R = Me (98%)
16a: X = PF6, R = H (98%)
16b: X = PF6, R = Me (98%)
Mes
N
Cl
Cl
N Mes
1b
Mes
N
Cl
Cl
N Mes
1b
Mes
N
Mes
N
CuCl
RT, 2 h
CuCl
Cl
Cl
Ru
Cl Cl
Ru
RT, 2 h
Me
N
N
O
Me
PF6
N
N
Ru
Ru
O
O
4
Ph
Ph
N
Mes
N
Mes
PCy3
PCy3
R
R
PF6
7a: R = H (72%)
7b: R = CH3 (78%)
8a: R = H (77%)
8b: R = CH3 (78%)
Scheme 1. Synthesis of imidazolium ion-tagged Ru-complexes 7a,b and 8a,b.

S.-W. Chen et al. / Tetrahedron 65 (2009) 3397–3403
3399
Table 2
carried out in monophasic ionic solvent systems composed of
a
RCMs of various dienes with 7a and 8a in [bmim][PF6]/CH2Cl2
[bmim][NTf2]/CH2Cl2, [bmim][SbF6]/CH2Cl2, and [bmim][PF6]/
CH2Cl2 (1/1, v/v) (bmim¼1-butyl-3-methylimidazolium) at room
temperature in the presence of 1.0 mol % of 7a.
Entry
17
18
7a
8a
Timeb Convc (%) Timeb Convc (%)
The reactions were monitored by TLC and the final conversion
was determined by GC and NMR analyses. As observed by Dixneuf
et al. in RCM with ruthenium allenylidene salts in ionic liquids,4b
the catalytic activity was significantly dependent on the nature of
counter anion of ionic liquid. The reactions in [bmim][NTf2]/CH2Cl2
(entry 1, Table 1) and [bmim][SbF6]/CH2Cl2 (entry 2, Table 1)
showed 74% and 51% conversions, respectively, for 2 h, whereas the
reaction in [bmim][PF6]/CH2Cl2 (entry 3, Table 1) was completed
within 10 min to provide ring-closed product 18a in over 98%
conversion. Based on these results, we investigated the catalytic
activity of 7b, 8a, and 8b in [bmim][PF6]/CH2Cl2 solvent. It has been
found that all of the imidazolium ion-tagged Ru-complexes showed
extremely high catalytic activities, and complete conversions ach-
ieved within 10–15 min at room temperature (entries 4–6, Table 1).
For comparison, the RCM reaction with original Hoveyda catalyst
2b was conducted under the same condition completing in 45 min
(entry 7, Table 1) indicating that anchoring imidazolium tag onto
chelating isopropoxy group increased the catalytic activity.
To evaluate the substrate scope of imidazolium-tagged Ru-
complexes, RCM reactions of various dienes 17b–17h with 7a and
8a were conducted in [bmim][PF6]/CH2Cl2 at room temperature,
and the results are summarized in Table 2.
Both 7a and 8a showed excellent catalytic activity for all sterically
less demanding dienes 17b–17f, and thus, the reactions were com-
pleted within 10 min to give the corresponding ring-closed products
18b–18f in almost quantitative conversions (entries 1–5, Table 2). The
RCM of olefin 17g affording trisubstituted cyclic olefin 18g was also
completed at room temperature with prolonged reaction time (entry
6, Table 2). Moreover, the sterically more demanding diene 17h,
known to be a difficult substrate for RCM, can be cyclized smoothly,
but required high temperature (40 ꢀC) (entry 7, Table 2).
Ts
N
Ts
N
1
10 min >98
10 min >98
10 min >98
10 min >98
18b
17b
Ts
N
Ts
N
2
3
18c
17c
CO2Et
EtO2C
EtO2C
CO2Et
10 min >98
10 min >98
18d
CO2Et EtO2C
17d
EtO2C
CO2Et
4
5
6
10 min >98
10 min >98
10 min >98
10 min >98
17e
CO2Et
18e
EtO2C
CO2Et
EtO2C
18f
Ts
17f
Ts
N
N
2.5 h
36 h
>98
2 h
>98
17g
18g
Ts
N
Ts
N
7d
72
36 h
86
We next investigated the recyclability of the imidazolium ion-
tagged catalysts. To recover the catalyst immobilized in ionic liquid,
volatile CH2Cl2 was evaporated and the product was extracted with
diethyl ether (2.0 mLꢁ5). The recovered catalyst/ionic liquid was
reused for next run. Disappointingly, the catalytic activity of the
recovered 7a, immobilized in [bmim][PF6], was dramatically de-
creased in the 2nd cycle (entry 1, Table 3).
17h
18h
a
Reactions were carried out at room temperature using 1.0 mol % of catalyst in
[bmim][PF6]/CH2Cl2 (1/1, v/v, c¼0.5 M).
b
Time for completion.
Determined by 1H NMR analysis.
c
d
Reaction was conducted at 40 ꢀC.
A recent report by Maudit and Guillemin indicated that a bi-
phasic [bmim][PF6]/toluene is to be effective recyclable solvent
system in RCM reactions by using the imidazolium ion-tagged
Ru-complex 4.6b Thus, the ionic solvent system was changed to
a biphasic [bmim][PF6]/toluene (1/3, v/v) resulted in improved
recyclability, allowing two iterations of recycling with diminished
reactivity (entry 2, Table 3). Compared to reaction in [bmim][PF6]/
CH2Cl2, the reaction rate was relatively decreased in [bmim][PF6]/
toluene solvent system, which could be ascribed to its biphasic
nature. The level of recyclability of 7a was improved further as the
ionic liquid was changed from [bmim][PF6] to [bdmim][PF6]
(bdmim¼1-butyl-2,3-dimethylimidazolium) (entry 3, Table 3). To
our delight, in contrast to 7a, the use of 1,2-dimethylimidazolium
ion-tagged 7b dramatically increased recyclability, thus, the re-
covered 7b/[bdmim][PF6] could be reused for several times without
any loss of catalytic activity (entry 4, Table 3). These results clearly
indicated that the structures of imidazolium tag and ionic liquid
used have a pronounced effect on recyclability. Comparisons of the
levels of Ru residue in toluene layer from 1st run with 7a in
[bmim][PF6]/toluene (entry 2, Table 3), 7a in [bdmim][PF6]/[tolu-
ene] (entry 3, Table 3), and 7b in [bdmim][PF6]/toluene (entry 4,
Table 3) also supported the structural effects of imidazolium moiety
on catalyst stability. Combination of 2-methylated imidazolium-
tagged 7b with [bdmim][PF6]/toluene minimized Ru leaching. In-
terestingly, the Ru-complexes 8a and 8b, in which the imidazolium
moieties are in the proximity of reaction metal center, showed
higher conversion rate compared with the 7a and 7b in a biphasic
Table 1
RCM of 17a with catalysts 7a,b and 8a,b in ionic liquidsa
catalyst
(1.0 mol%)
ionic liquid/CH2Cl2
(1/1, v/v), c = 0.5 M
room temp. time
N
N
Ts
18a
Ts
17a
Entry
Catalyst
Ionic liquid
Timeb
Convc (%)
1
2
3
4
5
6
7
7a
7a
7a
7b
8a
8b
2b
[bmim][NTf2]
[bmim][SbF6]
[bmim][PF6]
[bmim][PF6]
[bmim][PF6]
[bmim][PF6]
[bmim][PF6]
2 h
2 h
74
51
10 min
10 min
10 min
15 min
45 min
>98
>98
>98
>98
>98
a
Reactions were carried out at room temperature using 1.0 mol % of catalyst in
ionic liquid/CH2Cl2 (1/1, v/v, c¼0.5 M).
b
Time for completion.
c
Determined by GC and 1H NMR analyses.

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S.-W. Chen et al. / Tetrahedron 65 (2009) 3397–3403
Table 3
acrylate. Both 7b and 8b showed excellent catalytic activities in the
first runs, and thus the cross metathesis products 21 and 22 were
formed in over 90% with E-isomer selectivity. However, the cata-
lytic activities of the recovered catalysts immobilized in ionic liquid
layer were dramatically decreased in 2nd runs, which could be
ascribed to the remained methyl acrylate. To avoid the self-cross
metathesis, at least 2 equiv methyl acrylate was used, and the
remained methyl acrylate provokes a competitive metathesis re-
action against the styrenyl ether inhibiting the return process of the
catalytically active Ru-catalyst.
Recycling of catalysts 7a,b and 8a,b for RCM of 17a in ionic liquid
catalyst
(1.0 mol%)
solvent, c = 0.5 M
N
N
Ts
18a
Ts
17a
room temp. time
Entry
1
Cat.
Solvent
Cycle
Time
Conva (%)
7a
[bmim][PF6]/MC
1
2
1
2
3
1
2
3
1
2
3
4
5
6
7
8
1
2
3
1
2
3
10 min
1 h
1.5 h
4 h
12 h
1 h
3 h
12 h
1 h
1 h
1 h
1 h
1 h
2 h
6 h
6 h
30 min
30 min
30 min
30 min
30 min
30 min
>98
20
>98
>98
46
>98
>98
80
>98
>98
>98
>98
>98
>98
>98
77
2
3
4
7a
7a
7b
[bmim][PF6]/toluene
Ru residue: 89 ppmb
3. Conclusion
[bdmim][PF6]/toluene
Ru residue: 87 ppmb
A new-type of Hoveyda-type Ru-complexes 7a,b and 8a,b an-
choring imidazolium ion onto the chelating isopropoxy group has
been designed and synthesized to perform olefin metathesis in
ionic liquid. These catalysts exhibited excellent catalytic activities
for ring-closing metathesis and cross metathesis. The present work
highlights the fact that changing the location of the tagging and the
structures of imidazolium tag and ionic liquid as well as the com-
position of ionic solvent can dramatically improve the catalyst/ionic
liquid and minimized residual Ru levels in the RCM products. Thus,
combination of 2-methylated imidazolium ion-tagged Ru-complex
7b with a biphasic [bdmim][PF6]/toluene medium increased dra-
matically the recycling of the catalyst and low residual Ru levels
were detected by ICP-AES in the product. Excellent activities were
also observed in first runs of cross metathesis, however, the recy-
clability was very low. Further studies on the development of
a more effective recyclable catalytic system for cross metathesis in
ionic liquids are currently underway.
[bdmim][PF6]/toluene
Ru residue: 21 ppmb
5
6
8a
8b
[bdmim][PF6]/toluene
[bdmim][PF6]/toluene
>98
97
11
>98
93
27
a
Determined by GC and 1H NMR analyses.
Ru contents in toluene layer after 1st run and determined by ICP-AES.
b
solvent system. Thus, the RCM reactions with 8a (entry 5, Table 3)
and 8b (entry 6, Table 3) in [bdmim][PF6]/toluene were completed
within 30 min. However, the catalytic activities of the recovered
catalysts were dramatically decreased in 3rd runs. Taken all to-
gether, it can be concluded that the structure of the imidazolium
tag and ionic liquid, as well as the choice of the anchoring position
of the imidazolium tag, and composition of ionic solvent system are
important for the development of highly reactive and recyclable
Ru-catalysts for RCMs in ionic liquids.
4. Experimental
4.1. General
Nuclear magnetic resonance (NMR) spectra were recorded on
a Varian Mercury VX250 NMR spectrometer (250 MHz) in given
solvent. Chemical shifts were expressed in parts per million with
TMS as an internal standard (
d
¼0 ppm) for 1H NMR, coupling
Finally, we investigated catalytic activity and recyclability of the
imidazolium ion-tagged Ru-complexes for cross metathesis (CM) in
ionic liquids (Scheme 2).
constants (J) are in hertz. The anhydrous toluene was distilled from
sodium benzophenone ketyl. The DMF and methylene chloride
were freshly distilled from calcium hydride. The purchased re-
agents are used as-received without further purification. All ma-
nipulations involving air and moisture-sensitive compounds and
reactions were carried out using standard Schlenk technique under
nitrogen atmosphere.
O
Ph
Ph
O
19
20
cat. (1.0 mol%)
[bdmim][PF6]/
toluene (1/3)
O
4.2. Synthesis
OMe
OMe
c= 0.5, RT, 4 h
O
4.2.1. 2-(2-Propenylphenoxy)propionic acid methyl ester (9)
OMe
To a solution of E/Z mixture of 2-propenylphenol (3.03 g,
22.58 mmol) and methyl 2-bromopropionate (5.63 g, 33.70 mmol)
in anhydrous DMF (30 mL) were added Cs2CO3 (1.47 g, 4.52 mmol)
and K2CO3 (4.66 g, 33.70 mmol). After stirring for 10 h at room
temperature, the reaction mixture was poured into water (100 mL)
and extracted with EtOAc (3ꢁ50 mL). The combined organic layer
was washed with brine, dried (Na2SO4), and concentrated under
vacuum. Purification by silica gel chromatography (EtOAc/
hexane¼1/9 v/v) afforded the desired product 9 as a colorless oil
(4.65 g, 93.6%). Spectral data for major isomer: 1H NMR (250 MHz,
Ph
O
Ph
O
O
21
22
with catalyst 7b
with catalyst 7b
st run: 92% (E/Z = 18:1)
1
2
st run: 90% (E/Z = 20:1)
nd run: 10% (E/Z = 21:1)
1
2nd run: 12% (E/Z = 15:1)
with catalyst 8b
with catalyst 8b
st run: 90% (E/Z = 15:1)
nd run:14% (E/Z = 15:1)
1
2
st run: 89% (E/Z = 19:1)
nd run:12% (E/Z = 20:1)
1
2
Scheme 2. Cross metatheses with 7b and 8b in [bdmim][PF6]/toluene.
CDCl3)
d
7.41 (dd, J¼7.7, 1.7 Hz, 1H), 7.18–7.06 (m, 1H), 6.94–6.88 (m,
Based on the results from ring-closing metathesis described
above, the Ru-complexes 7b and 8b anchoring 2-methylated imi-
dazolium ion tag and [bdmim][PF6]/toluene solvent system were
selected for CMs of 5-pentenylbenzoate 19 and 3-phenyl-1-pro-
pene 20 with a standard electron demanding substrate, methyl
1H), 6.78 (dq, J¼15.9, 1.8 Hz, 1H), 6.69 (dq, J¼8.2, 1.0 Hz, 1H), 6.23
(dq, J¼15.9, 6.6 Hz, 1H), 4.73 (q, J¼6.8 Hz, 1H), 3.72 (s, 3H), 1.90 (dd,
J¼6.6, 1.8 Hz, 3H), 1.63 (d, J¼6.8 Hz, 3H) ppm; 13C NMR (62.5 MHz,
CDCl3)
d 172.7, 154.2, 130.5, 127.9, 127.6, 126.6, 125.4, 121.7, 113.0,
73.3, 52.2, 18.9, 18.6 ppm.

S.-W. Chen et al. / Tetrahedron 65 (2009) 3397–3403
3401
4.2.2. 2-(2-Propenylphenoxy)propan-1-ol (10)
(m, 1H), 4.16 (t, J¼7.3 Hz, 2H), 3.88 (s, 3H), 3.55–3.42 (m, 4H), 2.60
(s, 3H), 1.81–1.72 (m, 5H), 1.56–1.51 (m, 2H), 1.20 (d, J¼6.2 Hz, 3H)
To a stirred solution of 9 (6.0 g, 27.24 mmol) in anhydrous THF
(100 mL) was added LiAlH4 (32.7 mL, 1 M in THF) dropwise at
0 ꢀC. After stirring for 1 h at 0 ꢀC, the excess of LiAlH4 was
destroyed by addition of saturated aqueous Na2SO4 dropwise. The
appeared white precipitate was filtered and the residue was
washed with THF several times. The THF filtrate was dried with
anhydrous Na2SO4, and the THF was evaporated to afford 10
(5.12 g, 97.7%) as a slightly yellow oil, which was used for next
reaction without further purification. The spectral data of major
ppm; 13C NMR (62.5 MHz, CD2Cl2)
d 155.0, 144.0, 130.5, 128.1, 126.5,
125.7,123.3,121.6,120.6,114.8,114.5, 74.6, 74.4, 71.0, 48.6, 35.9, 27.4,
26.5, 19.1, 17.2, 10.7 ppm. IR: 3343, 3050, 2957, 2316, 1594, 1458,
1258, 1123, 970, 905, 753 cmꢂ1
.
4.2.6. 3-Methyl-1-{4-[2-(2-propenylphenoxy)-propoxy]-butyl}-3H-
imidazolium hexafluorophosphate (13a)
To a stirred solution of 12a (1.0 g, 2.74 mmol) in anhydrous
CH3CN (15 mL) was added NaPF6 (1.15 g, 6.85 mmol). The resulting
mixture was stirred for 12 h at room temperature, and then filtered.
After evaporation of the solvent, the resulting residue was dis-
tributed in water and methylene chloride, and the water layer was
washed with methylene chloride. The combined methylene chlo-
ride layer was evaporated, and dried under vacuum to give 13a
(1.27 g, 98.2%) as colorless oil. The spectral data of major isomer: 1H
isomer: 1H NMR (250 MHz, CDCl3)
d
7.39 (dd, J¼8.0, 1.6 Hz, 1H),
7.16–7.09 (m, 1H), 6.93–6.86 (m, 2H), 6.71 (dq, J¼15.9, 1.6 Hz, 1H),
6.19 (dq, J¼15.9, 6.6 Hz, 1H), 4.47–4.40 (m, 1H), 3.74–3.68 (m, 2H),
2.52 (br s, 1H), 1.88 (dd, J¼6.6, 1.6 Hz, 3H), 1.22 (d, J¼6.2 Hz, 3H)
ppm; 13C NMR (62.5 MHz, CD2Cl2)
d 154.8, 130.7, 128.7, 128.3,
127.2, 125.9, 121.6, 114.9, 76.3, 66.5, 19.0, 16.2 ppm. IR: 3591, 3374,
3038, 2985, 2940, 2090, 1594, 1484, 1447, 1241, 1148, 1041, 914,
742 cmꢂ1
.
NMR (250 MHz, CDCl3)
d
8.29 (s, 1H), 7.36 (dd, J¼1.4, 7.6 Hz, 1H),
7.26–7.14 (m, 3H), 6.95–6.85 (m, 2H), 6.65 (dq, J¼15.9, 1.5 Hz, 1H),
6.20 (dq, J¼15.8, 6.5 Hz, 1H), 4.48–4.60 (m, 1H), 4.11 (t, J¼7.2 Hz,
2H), 3.74 (s, 3H), 3.66–3.41 (m, 4H), 2.00–1.75 (m, 5H),1.57–1.51 (m,
4.2.3. 1-[2-(4-Chlorobutoxy)-1-methylethoxy]-2-propenyl-
benzene (11)
To a solution of 10 (4.6 g, 23.93 mmol) in anhydrous DMF
(50 mL) was added NaH (1.44 g, 35.89 mmol) at 0 ꢀC. After stir-
ring for 10 min at 0 ꢀC, 1-bromo-4-chlorobutane (8.21 g,
47.86 mmol) was added. The resulting mixture was stirred for
48 h at room temperature and the reaction mixture was
quenched with water (50 mL), and extracted with ethyl acetate
(3ꢁ25 mL). The combined organic layer was dried with Na2SO4
and concentrated by vacuum. The residue was purified by flash
column chromatography on silica gel (EtOAc/hexane 1/5) to give
the product 11 (6.1 g, 90.0%) as a colorless oil. The spectral data
2H), 1.27 (d, J¼6.3 Hz, 3H) ppm; 13C NMR (62.5 MHz, CDCl3)
d 154.5,
135.8, 130.3, 128.1, 126.4, 125.5, 123.4, 122.2, 121.2, 120.5, 114.4, 74.4,
74.1, 70.8, 49.5, 35.9, 27.5, 25.5, 18.9, 16.8 ppm. IR: 3055, 2993, 2308,
1594, 1430, 1266, 1106, 849, 731, 553 cmꢂ1
.
4.2.7. 2,3-Methyl-1-{4-[2-(2-propenylphenoxy)-propoxy]-butyl}-
3H-imidazol-1-ium hexafluorophosphate (13b)
Prepared by the same method for 13a using 12b. Yield: 98%. The
spectral data of major isomer: 1H NMR (250 MHz, CD2Cl2)
d 7.40 (dd,
J¼1.4, 7.6 Hz,1H), 7.21–7.13 (m, 3H), 6.95–6.89 (m, 2H), 6.72 (dq, J¼16.0,
1.4 Hz, 1H), 6.24 (dq, J¼15.9, 6.6 Hz, 1H), 4.62–4.53 (m, 1H), 4.05 (t,
J¼7.5 Hz, 2H), 3.75 (s, 3H), 3.64–3.54 (m, 4H), 2.51 (s, 3H),1.90–1.81 (m,
5H),1.64–1.59 (m, 2H), 1.30 (d, J¼6.3 Hz, 3H) ppm; 13C NMR (62.5 MHz,
of major isomer: 1H NMR (250 MHz, CD2Cl2)
d
7.40 (dd, J¼8.2,
1.7 Hz, 1H), 7.22–7.09 (m, 1H), 6.95–6.89 (m, 2H), 6.72 (dq,
J¼15.9, 1.6 Hz, 1H), 6.20 (dq, J¼15.9, 6.6 Hz, 1H), 4.49–4.47 (m,
1H), 3.62–3.47 (m, 6H), 1.88 (dd, J¼6.6, 1.6 Hz, 3H), 1.73–1.70 (m,
4H), 1.32 (d, J¼6.2 Hz, 3H) ppm; 13C NMR (62.5 MHz, CDCl3)
CD2Cl2) d 155.1, 144.1, 130.6, 128.3, 126.6, 125.9, 122.7, 121.4, 120.7, 114.8,
114.7, 74.8, 74.4, 71.1, 48.9, 35.5, 27.5, 26.3, 19.1, 17.0, 9.5 ppm. IR: 3050,
d
154.6, 130.3, 128.4, 127.8, 126.4, 125.9, 121.1, 114.8, 74.2, 74.1,
2985, 2299, 1585, 1444, 1267, 1117, 979, 835, 756, 556 cmꢂ1
.
70.6, 44.9, 29.4, 27.0, 18.9, 17.3 ppm. IR: 3049, 2982, 2875, 1597,
1447, 1261, 1114, 747, 705 cmꢂ1
.
4.2.8. 1-(2-Bromo-1-methylethoxy)-2-propenylbenzene (14)
To a solution of 10 (3.0 g, 15.60 mmol) and triethylamine
(3.26 mL, 23.41 mmol, 1.5 equiv) in dry dichloromethane (90 mL)
was added methanesulfonyl chloride (1.82 mL, 23.41 mmol,
1.5 equiv) at 0 ꢀC. The reaction mixture was stirred for 3.5 h at room
temperature. After filtration of the precipitates, the organic phase
was washed four times with a 5% citric acid solution, dried over
sodium sulfate, and concentrated to give the mesylated compound,
which was used without further purification in the following re-
action. The spectral data of major isomer: 1H NMR (250 MHz,
4.2.4. 3-Methyl-1-{4-[2-(2-propenylphenoxy)-propoxy]-butyl}-3H-
imidazolium chloride (12a)
A 50 mL round bottomed flask equipped with a condenser was
charged with 11 (1.0 g, 3.53 mmol), 1-methylimidazole (0.72 g,
8.84 mmol), and anhydrous acetonitrile (15 mL). The mixture was
refluxed for 36 h. After cooling to room temperature, the solvent
was evaporated, and the residue was washed with diethyl ether
(3ꢁ25 mL) to remove unreacted 1-methylimidazole to give 12a as
pale yellowish oil (1.18 g, 91.2%). The spectral data of major iso-
CDCl3)
d
7.40 (dd, J¼8.0, 1.8 Hz, 1H), 7.18–7.10 (m, 1H), 6.95–6.85 (m,
mer: 1H NMR (250 MHz, CD2Cl2)
d
7.40–7.14 (m, 4H), 6.96–6.88
2H), 6.71 (dq, J¼15.9, 1.7 Hz, 1H), 6.19 (dq, J¼15.8, 6.6 Hz, 1H), 4.62–
4.56 (m, 1H), 4.37–4.26 (m, 2H), 2.94 (s, 3H), 1.87 (dd, J¼6.6, 1.6 Hz,
(m, 2H), 6.69 (dq, J¼15.9, 1.6 Hz, 1H), 6.23 (dq, J¼15.9, 6.6 Hz, 1H),
4.60–4.50 (m, 1H), 4.31 (t, J¼7.2 Hz, 2H), 3.98 (s, 3H), 3.62–3.51
(m, 4H), 3.02 (br s, 1H), 1.99–1.93 (m, 2H), 1.86 (dd, J¼6.6, 1.6 Hz,
3H), 1.62–1.56 (m, 2H), 1.27 (d, J¼6.3 Hz, 3H) ppm; 13C NMR
3H), 1.30 (d, J¼6.2 Hz, 3H) ppm; 13C NMR (62.5 MHz, CDCl3)
d 153.7,
128.5, 127.9, 126.6, 125.5, 121.9, 121.2, 114.7, 72.5, 72.0, 37.4, 18.9,
16.3 ppm. To a solution of mesylate (2.97 g,11 mmol) obtained from
above procedure in tetrahydrofuran (40 mL) and dimethylforma-
mide (16 mL) was added lithium bromide (1.92 g, 22 mmol,
2 equiv) in one portion. The mixture was stirred overnight at room
temperature. After evaporation of the solvent, the residue was di-
luted in ethyl acetate. The organic layer was washed three times
successively with a saturated NaHCO3 solution and brine, dried
over magnesium sulfate, filtrated, and concentrated. The residue
was purified by silica gel chromatography using n-hexane/ethyl
acetate (20/1) as the eluent to afford 14 as colorless oil (2.33 g,
9.12 mmol, 85% (two steps)). The spectral data of major isomer: 1H
(62.5 MHz, CD2Cl2)
d 154.9, 138.2, 130.6, 128.1, 126.7, 125.9, 123.6,
122.3, 121.4, 120.7, 114.7, 74.7, 74.6, 71.1, 49.9, 36.7, 27.9, 26.3, 19.1,
17.1 ppm. IR: 3382, 3058, 2970, 1594, 1458, 1385, 1278, 1168, 1114,
970, 733, 606 cmꢂ1
.
4.2.5. 2,3-Dimethyl-1-{4-[2-(2-propenylphenoxy)-propoxy]-
butyl}-3H-imidazolium chloride (12b)
Prepared by the same method for 12a using 1,2-dimethylimi-
dazole. Yield: 93%. The spectral data of major isomer: 1H NMR
(250 MHz, CD2Cl2)
d
7.82 (d, J¼1.8 Hz, 1H), 7.58 (d, J¼1.9 Hz, 1H),
7.31 (dd, J¼1.1, 7.6 Hz, 1H), 7.16–7.04 (m, 1H), 6.87–6.77 (m, 2H),
6.64 (dq, J¼16.0, 1.5 Hz, 1H), 6.17 (dq, J¼15.8, 6.6 Hz, 1H), 4.52–4.40
NMR (250 MHz, CDCl3)
1H), 6.94–6.85 (m, 2H), 6.73 (dq, J¼15.9, 1.5 Hz, 1H), 6.23 (dq,
d
7.42 (dd, J¼7.6, 1.5 Hz, 1H), 7.18–7.12 (m,

3402
S.-W. Chen et al. / Tetrahedron 65 (2009) 3397–3403
J¼15.8, 6.6 Hz, 1H), 4.55–4.50 (m, 1H), 3.60–3.42 (m, 2H), 1.90 (dd,
J¼6.6, 1.8 Hz, 3H), 1.28 (d, J¼6.2 Hz, 3H) ppm; 13C NMR (62.5 MHz,
4.2.13. Imidazolium ion-tagged Ru-carbene complexes 7a,b
and 8a,b
CDCl3)
d
153.8, 128.7, 127.7, 126.6, 125.5, 121.8, 121.2, 114.8, 74.4,
A degassed solution of 13a (14.9 mg, 0.031 mmol), Grubbs 2nd-
35.6, 18.9, 14.7 ppm. IR: 3041, 2976, 2398, 2071, 1602, 1453, 1278,
1230, 1140, 1026, 950, 742 cmꢂ1
generation
catalyst,
RuCl2(]CHPh)(PCy3)(NHC),
(40.0 mg,
.
0.047 mmol), and CuCl (3.88 mg, 0.039 mmol) in dry dichloro-
methane (5 mL) was stirred at room temperature for 1 h. After
short column silica chromatography (MC/MeOH¼9/1, v/v), the
resulting material was treated with a mixture of CH2Cl2/pentane
(1/1, v/v) to provide the pure imidazolium-tagged Ru-carbene
complexes 7a as air-stable, greenish powder (56.6 mg, 72%). 1H
4.2.9. 3-Methyl-1-[2-(2-propenylphenoxy)]propyl-3H-imidazolium
bromide (15a)
A 100 mL round bottomed flask equipped with a condenser was
charged with compound 14 (2.5 g, 9.80 mmol), 1-methyl-1H-im-
idazole (1.61 g, 19.60 mmol), and anhydrous acetonitrile (50 mL).
The mixture was refluxed for 36 h and cooled to room temperature.
After evaporation of the solvent, the residue was washed with
diethyl ether (3ꢁ30 mL) to afford imidazolium bromide 15a as
slightly yellow oil (3.17 g, 95.6%). The spectral data of major isomer:
NMR (250 MHz, CDCl3)
d 16.62 (s, 1H), 8.30 (s, 1H), 7.51–7.47 (m,
1H), 7.08–6.97 (m, 8H), 6.84–6.83 (m, 2H), 4.98–4.96 (m, 1H), 4.15
(s, 4H), 4.10–3.84 (m, 2H), 3.68–3.60 (m, 2H), 3.55 (s, 3H), 3.32–
3.26 (m, 2H), 3.15–3.12 (m, 1H), 2.43–2.29 (m, 18H), 1.74–1.70 (m,
2H), 1.45–1.42 (m, 2H), 1.20 (d, J¼6.3 Hz, 3H) ppm; 13C NMR
1H NMR (250 MHz, CD2Cl2)
d
9.95 (s, 1H), 7.62 (d, J¼1.4 Hz, 1H), 7.50
(62.5 MHz, CDCl3) d 296.4, 209.8, 152.3, 144.6, 139.0, 130.1, 129.8,
(d, J¼1.5 Hz,1H), 7.37 (dd, J¼7.6,1.4 Hz,1H), 7.14–7.07 (m, 1H), 6.92–
6.83 (m, 2H), 6.64 (dq, J¼15.9, 1.5 Hz, 1H), 6.20 (dq, J¼15.9, 6.6 Hz,
1H), 4.89–4.84 (m, 2H), 4.56–4.41 (m, 1H), 3.98 (s, 3H), 1.90 (dd,
J¼6.6, 1.5 Hz, 3H), 1.33 (d, J¼6.1 Hz, 3H) ppm; 13C NMR (62.5 MHz,
129.4, 123.6, 123.4, 123.1, 122.8, 122.3, 122.2, 113.5, 73.6, 70.2, 51.6,
49.4, 36.0, 27.6, 25.1, 21.1, 18.8, 17.4, 17.1 ppm; HRMS (m/z) Calcd
for [M]þ: C39H51Cl2F6N4O2PRuþ: 924.2069. Found: 924.2074.
Compound 7b was prepared from 13b. Yield: 78%. 1H NMR
CD2Cl2)
d
151.2, 135.9, 128.6, 126.4, 126.0, 125.1, 124.6, 123.3, 121.4,
(250 MHz, CDCl3) d 16.57 (s, 1H), 7.56–7.52 (m, 2H), 7.10–7.04 (m,
121.3, 119.9, 112.4, 71.3, 34.7, 16.9, 14.8 ppm. IR: 3374, 3049, 2956,
2434, 2090, 1594, 1453, 1238, 970, 888, 761, 618, 536 cmꢂ1
5H), 6.96 (d, J¼8.2 Hz, 1H), 6.84–6.82 (m, 2H), 4.99–4.93 (m, 1H),
4.14 (s, 4H), 3.70–3.62 (m, 5H), 3.30–3.25 (m, 4H), 2.44–2.30 (m,
18H), 1.63–1.58 (m, 2H), 1.47–1.44 (m, 2H), 1.19 (d, J¼6.3 Hz, 3H)
.
4.2.10. 2,3-Methyl-1-[2-(2-propenylphenoxy)]propyl-3H-
imidazolium bromide (15b)
ppm; 13C NMR (62.5 MHz, CDCl3)
d 296.6, 210.1, 152.4, 144.6, 143.5,
139.0, 129.8, 128.7, 127.5, 126.4, 123.6, 122.6, 122.1, 120.7, 113.5,
73.5, 70.0, 51.5, 48.1, 34.9, 26.8, 25.8, 21.1, 19.3, 17.4, 16.9, 9.1 ppm;
HRMS (m/z) Calcd for [M]þ: C40H53Cl2F6N4O2PRuþ: 938.2225.
Found: 938.2231. Compound 8a was prepared from 16a. Yield:
Prepared by the same method for 15a using 1,2-dimethylimi-
dazole. Yield: 94%. The spectral data of major isomer: 1H NMR
(250 MHz, CD2Cl2)
d
7.88 (d, J¼2.1 Hz, 1H), 7.58 (d, J¼2.1 Hz, 1H),
7.28 (dd, J¼7.6, 1.5 Hz, 1H), 7.04–6.98 (m, 1H), 6.82–6.70 (m, 2H),
6.48 (dq, J¼15.9, 1.5 Hz, 1H), 6.09 (dq, J¼15.9, 6.6 Hz, 1H), 4.84–4.70
(m, 2H), 4.40–4.34 (m, 1H), 3.78 (s, 3H), 2.67 (s, 3H), 1.79 (dd, J¼7.0,
1.8 Hz, 3H), 1.30 (d, J¼6.1 Hz, 3H) ppm; 13C NMR (62.5 MHz, CD2Cl2)
77%; 1H NMR (250 MHz, CDCl3)
d 16.64 (s, 1H), 8.25 (s, 1H), 7.53–
7.26 (m, 4H), 6.96–6.84 (m, 5H), 6.50–6.48 (m, 1H), 5.37–5.34 (m,
1H), 4.45–4.18 (m, 4H), 3.53 (s, 3H), 2.47–2.31 (m, 18H), 1.26 (d,
J¼6.3 Hz, 3H) ppm; 13C NMR (62.5 MHz, CDCl3)
d 297.4, 208.9,
d
151.1, 142.9, 128.5, 126.3, 126.0, 124.9, 124.5, 123.3, 120.8, 120.3,
151.8, 143.7, 140.9, 139.2, 134.9, 130.1, 129.5, 129.0, 126.5, 124.1,
123.5, 122.6, 111.2, 53.8, 51.6, 36.5, 21.1, 19.4, 17.8, 17.5 ppm. IR:
3058, 2990, 2308, 1430, 1267, 897, 843, 742, 561 cmꢂ1; HRMS
(m/z) Calcd for [MꢂHPF6]þ: C35H43Cl2N4ORuþ: 707.1861. Found:
707.1892. Compound 8b was prepared from 16b. Yield: 78%; 1H
119.8, 112.3, 71.6, 33.9, 16.8, 14.9, 9.1 ppm. IR: 3366, 3067, 2957,
1594, 1492, 1456, 1266, 1241, 1131, 1041, 976, 894, 742 cmꢂ1
.
4.2.11. 3-Methyl-1-[2-(2-propenylphenoxy)]propyl-3H-
imidazolium hexafluorophosphate (16a)
NMR (250 MHz, CDCl3) d 16.57 (s, 1H), 7.56–7.52 (m, 1H), 7.37–7.26
To a stirred solution of 15a (0.8 g, 2.37 mmol) in anhydrous
CH3CN (15 mL) was added NaPF6 (0.48 g, 2.85 mmol). The resulting
mixture was stirred for 12 h, and then filtered through Celite. After
evaporation of solvent, the residue was dissolved in methylene
chloride, and washed with water, and evaporated to give 16a as
dark yellow oil (0.95 g, 97.6%). The spectral data of major isomer: 1H
(m, 4H), 6.96–6.87 (m, 4H), 6.50–6.43 (m, 1H), 4.99–4.93 (m, 1H),
4.30–4.17 (m, 5H), 3.62–3.48 (m, 4H), 2.53–2.30 (m, 21H), 1.30 (d,
J¼6.3 Hz, 3H) ppm; 13C NMR (62.5 MHz, CDCl3)
d 296.6, 209.0,
151.4, 144.8, 144.3, 139.2, 130.0, 129.4, 128.9, 126.4, 123.6, 122.6,
122.0, 114.0, 111.2, 75.3, 51.7, 35.0, 21.0, 19.5, 17.4, 16.8, 9.6 ppm. IR:
3066, 2197, 2082, 1972, 1258, 843, 733, 552 cmꢂ1; HRMS (m/z)
Calcd for [MꢂHPF6]þ: C36H45Cl2N4ORuþ: 721.2018. Found:
721.2026.
NMR (250 MHz, acetone)
d
8.93 (s, 1H), 7.72 (d, J¼1.4 Hz, 1H), 7.62
(d, J¼1.3 Hz,1H), 7.44 (dd, J¼7.6,1.6 Hz,1H), 7.21–7.12 (m,1H), 6.99–
6.89 (m, 2H), 6.71 (dd, J¼15.9, 1.5 Hz, 1H), 6.23 (dq, J¼15.9, 6.6 Hz,
1H), 4.96–4.92 (m, 1H), 4.67–4.57 (m, 2H), 3.99 (s, 3H), 1.88 (dd,
J¼6.6, 1.5 Hz, 3H), 1.33 (d, J¼6.1 Hz, 3H) ppm; 13C NMR (62.5 MHz,
4.3. Olefin metathesis in ionic liquid
acetone)
d 154.2, 138.1, 131.3, 129.1, 128.9, 127.3, 126.2, 124.6, 124.2,
122.7, 115.3, 73.8, 54.8, 36.7, 19.0, 17.0 ppm. IR: 3165, 3058, 2990,
4.3.1. A typical procedure for ring-closing metathesis in ionic liquid
using imidazolium ion-tagged catalysts
1594, 1447, 1258, 1176, 852, 739, 553 cmꢂ1
.
A solution of 7b (3.68 mg, 4.0ꢁ10ꢂ3 mmol) in a mixture of
[bmim][PF6]/CH2Cl2 (1.0 mL/1.0 mL) (or [bdmim][PF6]/toluene,
0.5 mL/1.5 mL) was stirred at room temperature for 1 h, at which
point diene 17a (100 mg, 0.4 mmol) was added. The reaction mix-
ture was stirred until completion of the conversion (by TLC). After
evaporation of CH2Cl2, the ionic liquid layer was extracted with dry
diethyl ether (2 mLꢁ5), and then the diethyl ether was evaporated.
For the [bmim][PF6]/toluene solvent system: the toluene layer was
separated and then the ionic liquid layer was extracted with tolu-
ene (2 mLꢁ5). After evaporation of the diethyl ether (or toluene),
the crude residue was subjected to GC and 1H NMR analyses to
reveal complete conversion. The ionic liquid phase containing 7b
was reused for subsequent runs.
4.2.12. 2,3-Methyl-1-[2-(2-propenylphenoxy)]propyl-3H-
imidazolium hexafluorophosphate (16b)
Prepared by the same method for 16a using 15b. Yield: 98%. The
spectral data of major isomer: 1H NMR (250 MHz, acetone)
d 7.70
(d, J¼2.1 Hz, 1H), 7.60 (d, J¼2.1 Hz, 1H), 7.44 (dd, J¼7.7, 1.5 Hz, 1H),
7.15–7.12 (m, 1H), 6.97–6.88 (m, 2H), 6.65 (dq, J¼15.9, 1.5 Hz, 1H),
6.24 (dq, J¼15.9, 6.6 Hz, 1H), 4.99–4.97 (m, 1H), 4.70–4.64 (m, 2H),
3.94 (s, 3H), 2.85 (s, 3H), 1.87 (dd, J¼6.6, 1.5 Hz, 3H), 1.40 (d,
J¼6.1 Hz, 3H) ppm; 13C NMR (62.5 MHz, CD2Cl2)
d 153.1, 145.3,
128.9, 128.3, 127.6, 127.0, 125.5, 122.8, 122.5, 122.2, 114.5, 73.4, 35.6,
19.0, 17.0, 14.7, 10.2 ppm. IR: 3061, 2993, 2310, 1421, 1258, 846, 756,
710, 553 cmꢂ1
.

S.-W. Chen et al. / Tetrahedron 65 (2009) 3397–3403
3403
4592; (c) Grubbs, R. H. Handbook of Metathesis; Wiley-VCH: Weinheim, 2003; (d)
Connon, S. J.; Blechert, S. Angew. Chem., Int. Ed. 2003, 42, 1900; (e) Astruc, A. New
J. Chem. 2005, 29, 42.
2. Review on supported Ru-catalysts, see: Clavier, H.; Grela, K.; Kirschning, A.;
Mauduit, M.; Nolan, S. P. Angew. Chem., Int. Ed. 2007, 46, 6786.
4.3.2. A typical procedure for cross metathesis in [bdmim][PF6]/
toluene
A solution of 7b (4.9 mg, 5.2ꢁ10ꢂ3 mmol) in a mixture of
[bdmim][PF6]/toluene (0.3 mL/0.9 mL) was stirred at room tem-
perature for 30 min, at which point olefin 19 (100 mg, 0.52 mmol)
and methyl acrylate (90.5 mg, 1.05 mmol) were added all at once.
The reaction mixture was stirred at room temperature for 4 h. After
separation of toluene, the ionic liquid layer was extracted with
toluene (1 mLꢁ3), and the combined toluene was evaporated. The
residue was subjected to GC and 1H NMR analyses to determine the
conversion and E/Z ratio of the cross-coupled product. The ionic
liquid layer containing 7b was reused for 2nd run.
3. Recent reviews on ionic liquids: (a) Lee, S.-g. Chem. Commun. 2006, 1049; (b)
Song, C. E. Chem. Commun. 2004, 1033; (c) Antonietti, M.; Kuang, D.; Smarsly, B.;
Xhou, Y. Angew. Chem., Int. Ed. 2004, 43, 4988; (d) Davis, J. H., Jr.; Fox, P. A. Chem.
Commun. 2003, 1209; (e) Dupont, J.; de Souza, R. F.; Saurez, P. A. Z. Chem. Rev.
2002, 102, 3667; (f) Olivier-Bourbiou, H.; Magna, L. J. Mol. Catal. A: Chem. 2002,
182–183, 419; (g) Sheldon, R. Chem. Commun. 2001, 2399; (h) Wassercheid, P.;
Keim, W. Angew. Chem., Int. Ed. 2000, 39, 3772; (i) Welton, T. Chem. Rev. 1999, 99,
2071.
4. (a) Buijsman, R. C.; van Vuuren, E.; Sterrenburg, J. G. Org. Lett. 2001, 3, 3785; (b)
Semeril, D.; Olivier-Bourgbigou, H.; Bruneau, C.; Dixneuf, P. H. Chem. Commun.
2002, 146; (c) Mayo, K. G.; Nearhoof, E. H.; Kiddle, J. J. Org. Lett. 2002, 4, 1567; (d)
Csihony, S.; Fischmeister, C.; Bruneau, C.; Horva´th, I. T.; Dixneuf, P. H. New J.
Chem. 2002, 26, 1667; (e) Ding, X.; Lv, X.; Hui, B.; Chen, Z.; Xiao, M.; Guo, B.; Tang,
W. Tetrahedron Lett. 2006, 47, 2921.
Acknowledgements
5. (a) Yao, Q.; Zhang, Y. Angew. Chem., Int. Ed. 2003, 42, 3395; (b) Yao, Q.; Sheets, M.
J. Organomet. Chem. 2005, 690, 3577.
This work was supported by the Korean Research Foundation
(KRF-2006-312-C00587).
6. (a) Audic, N.; Clavier, H.; Mauduit, M.; Guillemin, J.-C. J. Am. Chem. Soc. 2003, 125,
9248; (b) Clavier, H.; Audic, N.; Mauduit, M.; Guillemin, J.-C. Chem. Commun.
2004, 2282; (c) Clavier, H.; Audic, N.; Mauduit, M.; Guillemin, J.-C. J. Organomet.
Chem. 2005, 690, 3585; (d) Rix, D.; Cı¨jo, F.; Laurent, I.; Gu1ajski, q.; Grela, K.;
Mauduit, M. Chem. Commun. 2007, 3771.
7. (a) Thurier, C.; Fischmeister, C.; Bruneau, C.; Olivier-Bourbigou, H.; Dixneuf, P. H.
J. Mol. Catal. A: Chem. 2007, 268, 127; (b) Thurier, C.; Fischemister, C.; Bruneau, C.;
Olivier-Bourbiou, H.; Dixneuf, P. H. ChemSusChem 2008, 1, 118.
Supplementary data
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2009.02.043.
8. (a) Lee, B. S.; Namgoong, S. K.; Lee, S.-g. Tetrahedron Lett. 2005, 46, 4501; (b)
Chen, S.-W.; Kim, J. H.; Song, C. E.; Lee, S.-g. Org. Lett. 2007, 9, 3845; (c) Chen, S.-
W.; Kim, J. H.; Shin, H.; Lee, S.-g. Org. Biomol. Chem. 2008, 6, 2676.
9. Bieniek, M.; Bujok, R.; Cabaj, M.; Lugan, N.; Lavigne, G.; Arit, D.; Grela, K. J. Am.
Chem. Soc. 2006, 128, 13652.
References and notes
1. Selected reviews on olefin metathesis: (a) Trnka, T. M.; Grubbs, R. H. Acc. Chem.
Res. 2001, 34, 18; (b) Schrock, R. R.; Hoveyda, A. H. Angew. Chem., Int. Ed. 2003, 42,