Preparation of polystyrene-supported Lewis acidic Fe(III) ionic liquid and its application in catalytic conversion of carbon dioxide

Article abstract of DOI:10.1016/j.tet.2012.03.048

A polystyrene-supported Lewis acidic iron-containing ionic liquid was proved to be recyclable and efficient heterogeneous catalyst for converting CO₂ into cyclic carbonate without utilization of any organic solvent or additive. Excellent yields and selectivity were obtained under mild reaction conditions. Notably, the catalyst could be readily recovered and reused over five times without appreciable loss of catalytic activity. A possible catalytic cycle was proposed. The present protocol has successfully been applied to reactions of aziridines/propargyl amines with CO₂. This kind of the catalyst presented herein would have great potential in industrial application thanks to its featured advantages.

Full text of DOI:10.1016/j.tet.2012.03.048

Tetrahedron 68 (2012) 3835e3842
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Preparation of polystyrene-supported Lewis acidic Fe(III) ionic liquid and its
application in catalytic conversion of carbon dioxide
*
Jian Gao, Qing-Wen Song, Liang-Nian He , Chang Liu, Zhen-Zhen Yang, Xu Han, Xue-Dong Li,
Qing-Chuan Song
State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A polystyrene-supported Lewis acidic iron-containing ionic liquid was proved to be recyclable and ef-
ficient heterogeneous catalyst for converting CO2 into cyclic carbonate without utilization of any organic
solvent or additive. Excellent yields and selectivity were obtained under mild reaction conditions. No-
tably, the catalyst could be readily recovered and reused over five times without appreciable loss of
catalytic activity. A possible catalytic cycle was proposed. The present protocol has successfully been
applied to reactions of aziridines/propargyl amines with CO2. This kind of the catalyst presented herein
would have great potential in industrial application thanks to its featured advantages.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 27 December 2011
Received in revised form 3 March 2012
Accepted 15 March 2012
Available online 22 March 2012
Keywords:
Carbon dioxide
Iron-containing ionic liquid
Cycloaddition
Heterogeneous catalyst
Cyclic carbonates
1. Introduction
and phosphines,10 alkali metal halides and onium salts,11 organo-
metallic compounds,12 CO2 adducts of N-heterocyclic carbenes13
Great efforts have been directed towards the fixation and utili-
zation of CO2 in the past two decades. In view of organic synthesis,
CO2 can be regarded as an easily available renewable carbon re-
source and an attractive C1 building block in organic synthesis,
which has the advantages of being non-toxic, abundant, and eco-
nomical.1e4 Therefore, the chemical fixation of CO2 is of great sig-
nificance from the viewpoint of better utilization of carbon
resources and environment concern. One of the most promising
methodologies in this area is the atom efficient insertion of CO2 into
epoxides to afford five-membered cyclic carbonates as shown in
Scheme 1, which can serve as electrolytes in secondary batteries,
valuable monomers of polycarbonates, and polyurethanes, aprotic
polar solvents, and raw materials in chemical reactions.5e9
and especially ionic liquids (ILs)4,9,14 firstly reported by Deng and
co-workers,14a which have been attracting rising interest in the last
decades with a diversified range of applications because of their
potential advantages including negligible vapor pressure, good
thermal stabilities, wide liquid temperature ranges and diversiform
structure/property modulation.15 Particularly, Kawanami and co-
workers found that 1-alkyl-3-methylimidazolium salts exhibited
high rate and effective activity for the synthesis of cyclic carbonate
under supercritical CO2 and BFꢀ4 was the most effective among the
counter anions (NO3ꢀ, CF3SO3ꢀ, BF4ꢀ, and PFꢀ6 ) of imidazolium salts.14c
Nevertheless, homogeneous catalysts are usually undesirably dis-
solved in the products making some procedures inevitably required
to separate the products with catalyst recovery. Such separation
procedure like distillation under reduced pressure would be cum-
bersome and high energy-consumed. To address this issue, het-
erogeneous catalysts have been also developed for the cycloaddtion
reaction, such as metal oxides,16 oxychlorides,17 Cs-loaded zeolite,
and alumina,18 active species including supported ILs through
polymers,19 silica,12e,20 which could have a synergistic effect dis-
covered by Sakakura,20d zeolite,21 and other materials.22 Notably, in
this regard, an imidazolium chloride IL grafted onto a highly cross-
linked polymer matrix developed by Han and co-workers19g could
be a representative example. Although significant advances have
been made, most of the above heterogeneous catalysts cannot meet
the current industrial demands because of some drawbacks, such as
Scheme 1. Cycloaddition of CO2 to epoxides.
In this respect, numerous homogeneous catalysts have been
developed for the synthesis of cyclic carbonates, including amines
* Corresponding author. Tel./fax: þ86 22 2350 3878; e-mail address: heln@
nankai.edu.cn (L.-N. He).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.03.048

3836
J. Gao et al. / Tetrahedron 68 (2012) 3835e3842
the need for a cosolvent16d,20l or cocatalyst,19d,20c,22c low catalyst
activity,19b long reaction time,12e,20l or the requirement for high CO2
pressure.20d Therefore, there is continuing motivation for de-
veloping low cost, highly efficient, and practical catalysts for the
chemical fixation of CO2 to cyclic carbonates.
depicted in Scheme 3, whose structure was characterized by using
FT-IR, SEM (Scanning Electron Microscopy), TGA (Thermogravi-
metric Analysis)/DTA (Differential Thermal Analysis) and AAS
(Atomic Absorption Spectroscopy).
Recently, the synthesis and application of task-specific ILs con-
taining transition metals have drawn much attention in this
thriving research field. The functionalized ILs are regarded as novel
and promising materials, which would favorably combine spec-
troscopic, and/or magnetic properties with high catalytic activity,
presumably originating from incorporated metals. In particular, the
Fe(III) based IL, e.g., [C4mim][FeCl4] (Scheme 2) possessing attrac-
tive properties of both IL and the Lewis acidic FeCl3, was found to
have great application in catalysis.23 As one of the most inexpensive
and non-pollutant metals, iron catalysis would be of great interest
and is constantly growing from a standpoint of sustainable catal-
ysis.24 And various iron salts and its complexes, which possess
unique properties, such as distinct Lewis acid character have been
proved to be efficacious, alternative and promising transition-metal
catalysts in a broad range of synthetic transformations.24
Scheme 3. Synthetic route of polystyrene-supported iron-containing IL catalyst.
2.2. Characterization of polystyrene-supported iron-
containing ionic liquid PS-MimFeCl4
FT-IR spectroscopy provided unequivocal evidence for the graft
of iron-containing IL onto polystyrene via a covalent bond manner.
Four typical peaks19h centered at 1606, 1566, 1154, and 1085 cmꢀ1
,
respectively, could correspond to the feature band absorption of the
imidazolium ring (Fig. 1). On the other hand, those peaks are absent
in non-functionalized polystyrene resin. Furthermore, the bands at
1263 and 671 cmꢀ1 of CH2Cl group absorption19i disappears in the
FT-IR spectra of PS-MimFeCl4, indicating full functionalization of
PS-CH2Cl. The above result is a clear indication of the chemical
immobilization of imidazolium FeClꢀ4 on polystyrene. In addition,
the IL loading was determined to be 2.62 mmol/g by using AAS
technique.
Scheme 2. Ionic liquids used in this study.
Cross-linked polystyrene is one of the most useful polymers
owing to its compatibility with a wide range of reaction condi-
tions.25 Furthermore, because of its easy preparation, recyclability,
low cost, and non-solubility in any commonly used organic solvent
and water, cross-linked polystyrene has attracted considerable at-
tention as an efficient support for homogeneous catalyst immobi-
lization.19g,26 In this context, we envisioned that a type of Lewis
acidic iron-containing IL being covalently grafted onto polystyrene
(PS-MimFeCl4, Scheme 2), could be utilized as a recyclable het-
erogeneous catalyst for the cycloaddition reaction of CO2 with ep-
oxides. More importantly, the presence of the Lewis acidic iron
center in the anionic part could activate an epoxide, thus facilitate
its ring-opening. As a result, we designed and prepared a new kind
of polystyrene-supported iron-containing ionic liquid, e.g., PS-
MimFeCl4, which displayed high catalytic activity for the cycload-
dition reaction of CO2 with epoxides together in the absence of any
additional organic solvent or additive.
Fig. 1. FT-IR spectra comparison of: (a) PS-CH2Cl, (b) fresh PS-MimFeCl4, (c) the first
recycled PS-MimFeCl4, (d) the fifth recycled PS-MimFeCl4.
The morphology of PS-MimFeCl4 was further observed using
SEM as shown in Fig. 2, showing that microscopic appearance of the
polymer changed obviously after it has been functionalized with
MimFeCl4. The surface of the MimFeCl4 functionalized polymer
became rough in comparison with that of the support (PS-CH2Cl).
However, the particle agglomeration is irregular. Thermal stability
would also be important for practical application of the polymer-
supported IL since vigorous shaking, filtration, or drastic acid-
ebase treatment may be encountered. In this aspect, the thermal
stability of PS-MimFeCl4 was measured using TGA and DTA, as
depicted in Fig. 3. It is observed that the weight loss of the catalyst
2. Results and discussion
2.1. Synthesis of polystyrene-supported iron-containing ionic
liquid PS-MimFeCl4
A
cross-linked polystyrene was functionalized with iron-
containing IL (MimFeCl4) using a modified procedure based on
literature.19h,27 The preparative procedure of the polystyrene-sup-
ported Lewis acidic Fe(III) based ionic liquid, i.e., PS-MimFeCl4 is

J. Gao et al. / Tetrahedron 68 (2012) 3835e3842
3837
Fig. 2. Scanning electron micrographs of: (a) PS-CH2Cl, (b) PS-MimFeCl4.
Table 1
4
PC synthesis catalyzed by various ILsa
Entry
Catalyst
Yieldb (%)
Selectivityb (%)
2
1
2
3
4
5
6
7
8
None
C4MimCl
0
48
55
2
0
9
0
88
91
66
0
27
73
81
C4MimBr
C4MimBF4
PS-CH2Clc
PS-MimCld
C4mimFeCl4
PS-MimFeCl4
TG
0
72
77
-2
-4
-6
-2.4mg (-82.7%)
a
Reaction conditions: PO, 10 mmol, 580.8 mg; catalyst, 1 mol % relative to PO;
CO2 2 MPa; 100 ꢁC; 6 h.
b
Determined by GC using biphenyl as the internal standard.
PS-CH2Cl, chloromethylated polystyrene.
PS-MimCl, polystyrene-supported imidazolium chloride.
c
d
DTA
100
200
300
400
500
600
700
PS-MimFeCl4 showed better catalyst performance in comparison
with C4MimBr (entries 7 and8 vs 3), as well as their none-iron-
containing counterparts, C4MimCl, and PS-MimCl, respectively
(entries 7 vs 2, 8 vs 6). This is understandable because the Lewis
acidity of the iron (III)-containing part could play a determining
role in activating the epoxide.14b,e,g,19b,28 Additionally, there may be
H-bonding interaction of the C2eH of imidazolium ring with FeClꢀ4 ,
which could play a significant role in improving the catalytic acti-
vity.14g As a consequence, the polystyrene-supported iron-con-
taining IL PS-MimFeCl4 was identified as the most effective catalyst
and was thus chosen as the bench catalyst for further investigation
given its easy recyclability.
o
Temperature/ C
Fig. 3. TGA and DTA of PS-MimFeCl4.
occurred slightly at ca. 290 ꢁC. The significant weight loss took place
in the region of 375e480 ꢁC, being attributed to its decomposition.
Consequently, the polystyrene-supported IL possesses pretty good
stability.
In short, structural characterization data could reveal that the
Fe(III) based IL is firmly anchored onto polystyrene resin.
2.3. Activities of various catalysts for cycloaddition of CO2 to
propylene oxide
2.4. Influence of reaction conditions on the synthesis of
propylene carbonate
The carboxylation reaction of propylene oxide (PO) with CO2 for
the synthesis of propylene carbonate (PC) was chosen as the model
reaction to examine the catalytic activity of PS-MimFeCl4 and to
evaluate effects of the reaction parameters. For comparison, several
imidazolium-based ILs were also tested in this study. The results
are listed in Table 1. Obviously, no reaction occurred at all without
any catalyst (entry 1, Table 1). In the cases of the imidazolium-based
ILs, the anions showed a crucial influence on the reaction. Halide
anions, such as Clꢀ, Brꢀ gave moderate yields as well as excellent
selectivity, probably thanks to their good leaving ability and nu-
cleophilicity (entries 2 and 3). However, the IL with BFꢀ4 anion was
found to be inefficacious (entry 4). On the other hand, the support
(PS-CH2Cl) and the catalyst precursor (polystyrene-supported
imidazolium chloride, PS-MimCl) were found to be almost inactive
(entries 5 and 6). To our delight, the FeCl3-based imidazolium IL,
e.g., C4mimFeCl4 and its polystyrene-supported counterpart, i.e.,
The influence of catalyst loading on PC synthesis was first in-
vestigated under identical reaction conditions as depicted in
Fig. 4(a). Both the yield and selectivity of PC reached maximum as
the catalyst loading was increased up to 1 mol %. Further increasing
the catalyst loading led to a slight decrease in both yield and se-
lectivity, presumably due to mass transfer limitation as solid
amount increasing. Thus, 1 mol % catalyst loading would be ap-
propriate for the reaction. It is also worth noting that facile for-
mation of the by-products, such as acetone and n-
propylaldehyde19c under the reaction conditions could cause a de-
crease in selectivity.
Furthermore, we found that PC yield and selectivity were
strongly affected by the reaction temperature. As shown in Fig. 4(b),
the yield of PC increased with temperature rising and optimal
performance was achieved at 100 ꢁC, although the selectivity de-
creased slightly compared with the maximum. In addition, the high

3838
J. Gao et al. / Tetrahedron 68 (2012) 3835e3842
100
100
80
60
40
20
0
80
60
40
PC Yield
20
PC Yield
Selectivity
Selectivity
0
60
80
100
120
140
0.0
0.5
1.0
1.5
2.0
2.5
Temperature/oC
Catalyst loading/mol%
(b)
Effect of temperature
(a)
Effect of catalyst loading
Reaction conditions: PO (10 mmol), PS-
MimFeCl4 (1 mol%), CO2 (2 MPa), 6 h.
Reaction conditions: PO (10 mmol), CO2
(2 MPa), 100 oC, 6 h.
100
100
80
60
80
40
PC Yield
PC Yield
20
Selectivity
Selectivity
60
4
6
8
10
12
0
2
4
6
8
10
Reaction time/h
CO Pressure/MPa
2
(d)
Effect of reaction time
(c)
Effect of CO2 pressure
Reaction conditions: PO (10 mmol), PS-
Reaction conditions: PO (10 mmol), PS-
MimFeCl4 (1 mol%), CO2 (8 MPa), 100 oC.
MimFeCl4 (1 mol%), 100 oC, 6 h.
Fig. 4. Dependence of PC yields and selectivity on different parameters catalyzed by PS-MimFeCl4.
catalytic activity can be maintained when the temperature was
further increased to 140 ꢁC, which also could prove the excellent
thermal stability of PS-MimFeCl4 experimentally. Conclusively,
100 ꢁC could be the optimal temperature for PC synthesis.
Shown in Fig. 4(c) is the yield and selectivity of PC as a function
of CO2 pressure. As a result, PC yield and selectivity are not sensitive
to CO2 pressure upon variation of CO2 pressure from 1 to 6 MPa. The
maximum yield and selectivity of PC appeared at ca. critical pres-
sure of 8 MPa. However, further increasing CO2 pressure up to
10 MPa led to a remarkable decrease both in yield and selectivity of
PC. This is because excessive CO2 may retard the interaction be-
tween the epoxide and the catalyst, and could cause a low con-
centration of epoxide in the vicinity of the catalyst, thus resulting in
a low yield.19c Therefore, 8 MPa would be an appropriate operating
pressure.
conditions. The catalyst was recovered after separation of PC
through a simple filtration and then used for the next run without
further purification under the identical reaction conditions. The
results shown in Fig. 5 indicate that the yields of PC are almost
consistent after five successive recycles. Furthermore, no significant
100
80
60
Dependence of PC yield and selectivity on reaction time is
shown in Fig. 4(d). As can be seen, the yield increased with reaction
time increasing within 6 h, and 6 h is needed to complete the re-
action. Further extending the reaction time had no apparent benefit
to the yield and selectivity.
40
PC Yield
20
0
2.5. Catalyst reusability
0
1
2
3
4
5
6
Cycle
To test catalyst reusability, the reaction was performed in the
presence of a catalytic amount of PS-MimFeCl4 by using 2-(chlor-
omethyl)oxirane as the starting material under the given reaction
Fig. 5. Recyclability of the catalyst. Reaction conditions: 2-(chloromethyl)oxirane
(10 mmol, 925.2 mg), PS-MimFeCl4 (1 mol %, 58 mg), CO2 (8 MPa), 100 ꢁC, 12 h.

J. Gao et al. / Tetrahedron 68 (2012) 3835e3842
3839
difference was observed in the FT-IR spectroscopies (Fig. 1) be-
tween the fresh catalyst and the recycled ones. In addition, the iron
content of the first recycled catalyst is 2.50 mmol/g detected by
AAS, which is just slightly lower than that of the fresh catalyst.
These results indicated that the catalyst PS-MimFeCl4 is stable and
can be recycled over five times without appreciable loss of activity.
depicted in Scheme 4. There could be an H-bonding interaction
formed from Clꢀ and C2eH of the imidazolium ring in the active
catalyst. Firstly, the epoxide is activated by the coordination with
the Lewis acidic Fe(III) species. Simultaneously, the nucleophilic
attack of Clꢀ on the less sterically hindered
b-carbon atom of the
epoxide furnishes the ring-opened intermediate A, which could be
stabilized through the H-bonding interaction. Then the insertion of
CO2 into the intermediate A would give chloroalkoxy carbonate
active species B, which eventually provides the cyclic carbonate
through subsequent intramolecular cyclization. The catalyst can be
also regenerated once the catalyst cycle completes. It is noteworthy
that the Lewis acidity of the iron(III)-containing species and the H-
bonding interaction could play a key role in promoting the reaction.
2.6. Substrates scope
The generality and utility of this protocol was also examined and
the results are summarized in Table 2. Generally, terminal epoxides
with both electron-withdrawing and electron-donating groups
could be transformed to the corresponding cyclic carbonates with
moderate to excellent yields and selectivity within 6 h under 8 MPa
CO2 pressure (entries 1e3). But for the terminal epoxides with
larger substituents, such as phenyl, allyloxymethyl, and iso-
propoxymethyl, higher reaction temperature and prolonged re-
action time were needed to obtain excellent results (entries 4e6).
However, internal cyclohexene oxide showed poor reactivity and
just 7% of the corresponding cyclic carbonate was obtained even for
longer reaction time under higher reaction temperature, pre-
sumably due to the steric effect (entry 7).
Table 2
Substrates scopea
Entry
1
Substrate
Product
Yieldb (%) Selectivityb (%)
57
88
64
89
2
3
Scheme 4. Proposed mechanism for PS-MimFeCl4-catalyzed cycloaddition reaction of
CO2 with epoxides.
96
100
2.8. Applications for the carboxylation of aziridine/propargyl
amine with CO2
This protocol was successfully applied to the reaction of azri-
dines 1 and propargyl amine with CO2. As listed in Table 3, various
oxazolidinones were selectively formed in good to excellent yields
as well as high regio- selectivities (entries 1e5).
4
84c
100c
5
6
87c
89d
95c
94d
Table 3
a
PS-MimFeCl4-catalyzed carboxylation of aziridines with CO2
7c
50c
Entry
R1, R2
Conv. (%)b
Yieldb (%)
Regio-sel. (%)b,c
7
1
2
3
4
5
Et, Ph
>99
>99
>99
>99
90
84
93
97
94
86
90:10
90:10
87:13
90:10
97:3
Et, p-MeeC6H4
Et, p-CleC6H4
n-Pr, Ph
a
Reaction conditions: epoxide, 10 mmol; PS-MimFeCl4, 1 mol %, 58 mg; CO2
8 MPa; 100 ꢁC; 6 h.
i-Bu, Ph
b
Determined by GC.
c
120 ꢁC, 12 h.
a
Reaction conditions: azridines, 1 mmol; PS-MimFeCl4, 1 mol %, 5.8 mg; CO2
8 MPa; 100 ꢁC; 6 h.
d
120 ꢁC, 24 h.
b
Determined by GC.
Molar ratio of 2e3.
c
2.7. Reaction mechanism
In addition, the corresponding five-membered oxazolidinone
product was obtained in moderate yield when propargyl amine
reacted with CO2 under the given reaction conditions as shown in
Scheme 5.
Based on previous reports14b,e,g,19b,28 and the obtained results in
this study, a probable catalytic cycle was proposed for the cyclo-
addition of CO2 to epoxides using PS-MimFeCl4 as a catalyst, as

3840
J. Gao et al. / Tetrahedron 68 (2012) 3835e3842
methyl imidazole attached on PS-MimCl was about 3.0 mmol/g
determined by nitrogen content from elementary analysis. Then,
under a N2 atmosphere, a mixture of PS-MimCl (10 g), FeCl3
(4.87 g, 30 mmol), and 100 mL CH3CN was stirred at reflux
temperature for 72 h. After the reaction, the PS-MimFeCl4 ionic
liquid was obtained by filtration and dried at 70 ꢁC for 24 h under
reduced pressure.
Scheme 5. PS-MimFeCl4-catalyzed carboxylation of propargyl amine with CO2.
4.5. General procedure for the synthesis of PC from PO and
CO2
3. Conclusions
In summary, we developed a functionalized polystyrene bearing
iron-containing IL, viz. PS-MimFeCl4 as an efficient and recyclable
catalyst for the cycloaddition reaction of CO2 with epoxides/azir-
idine/propargyl amine in the absence of any organic solvent or
additive. The Lewis acidic iron center in the anion could play
a crucial role in the activation of epoxide, which could be re-
sponsible for the high catalyst performance in combination with
the H-bonding interaction between Clꢀ and C2eH of the imidazo-
lium ring. Notably, the catalyst could be used over five sequential
runs with only a 2% loss in maximum yield. Therefore this protocol
could have much potential application for the catalytic conversion
of CO2 into valuable compounds and materials in industry.
The reaction was carried out in a stainless-steel autoclave re-
actor with an inner volume of 25 mL. In an autoclave equipped
with a magnetic stirrer, CO2 (5 MPa) was added to a mixture of
propylene oxide (10 mmol, 580.8 mg) and polystyrene-supported
iron-containing ionic liquid PS-MimFeCl4 (1 mol %, 58 mg) at
room temperature. The initial pressure was generally adjusted to
8 MPa at 100 ꢁC. Then the autoclave was heated at that temper-
ature for 6 h, and the pressure was kept constant during the re-
action. After that, the vessel was cooled to ambient temperature
by placement in an ice-water bath. The excess gases were vented.
The product yields were determined by GC using biphenyl
(50 mg) as the internal standard. The products were also isolated
by column chromatography on silica gel and identified by NMR.
4. Experimental section
4.1. Caution
4.6. General procedure for the cycloaddition reaction of
azridine/propargyl amine with CO2
Experiments using compressed gases CO2 are potentially haz-
ardous and must only be carried out by using the appropriate
equipment and under rigorous safety precautions.
In a 25 mL autoclave reactor with a glass tube and a magnetic
stirrer, the substrate (1 mmol), catalyst (PS-MimFeCl4, 1 mol %,
5.8 mg), and CO2 (5 MPa) were successively charged at room
temperature. The initial pressure was generally adjusted to 8 MPa
at 100 ꢁC. Then the autoclave was heated at that temperature for
the appropriate time, and the pressure was kept constant during
the reaction. After the reaction was completed, the reactor was
cooled in ice water and CO2 was ejected slowly. An aliquot of
sample was taken from the resultant mixture for GC analysis using
biphenyl (50 mg) as the internal standard or 1H NMR analysis using
1-chloro-2,4-dinitrobenzene as the internal standard. The residue
was purified by column chromatography on silica gel
(200e300 mesh, eluting with 4:1 to 2:1 petroleum ether/ethyl
acetate) to provide the desired products.
4.2. Chemical reagents
Imidazolium-based ionic liquids are synthesized according to
the published procedures.19h,27,29 CO2 with a purity of 99.99% is
commercially available and epoxides are supplied from Aldrich
Company. Highly cross-linked chloromethylated polystyrene
(18e19% Cl content) was purchased from Tianjin Nankai Hecheng
S&T Co., Ltd.
4.3. Instrumentation
1H NMR spectra is recorded at Bruker 400/300 spectrometer in
CDCl3 and CDCl3 (7.26 ppm) is used as internal reference, 13C NMR is
recorded at 100.6/75 MHz in CDCl3 and CDCl3 (77.0 ppm) is used as
internal reference. GC analysis are performed on Shimadzu GC-
4.7. Characterization data
4.7.1. 4-(Chloromethyl)-1,3-dioxolan-2-one. Light yellow liquid; 1H
NMR (400 MHz, CDCl3)
d
¼3.71e3.80 (m, 2H, ClCH2), 4.40e4.44 (m,
3
2014, equipped with
a
capillary column (RTX-WAX,
1H, OCH2), 4.59 (t, JHH¼8.4 Hz, 1H, OCH2), 4.93e4.99 (m, 1H,
30 mꢂ0.25 m) using a flame ionization detector. Infrared (IR)
m
OCH) ppm; 13C NMR (100.6 MHz, CDCl3)
154.0 ppm.
d
¼43.5, 67.0, 74.2,
spectra were recorded on a Bruker Tensor27 FT-IR spectropho-
tometer with KBr pellets. AAS was performed on TAS-990. SEM was
performed on Tescan Vega 3 SBH. TGA was performed on a PTC-10A
TG-DTA analyzer (Japan, Rigaku) under air flow from room tem-
perature to 700 ꢁC with a heating rate of 10 ꢁC/min. Elementary
analysis was performed on vario EL CUBE analyzer.
4.7.2. 4-Phenyl-1,3-dioxolan-2-one. White
solid;
1H
NMR
3
(400 MHz, CDCl3)
d
¼4.35 (t, JHH¼8.2 Hz, 1H, OCH2), 4.80 (t,
3JHH¼8.4 Hz, 1H, OCH2), 5.68 (t, JHH¼8.0 Hz, 1H, OCH), 7.35e7.38
3
(m, 2H, ArH), 7.42e7.47 (m, 3H, ArH) ppm; 13C NMR (100.6 MHz,
CDCl3)
d¼76.6, 77.9, 125.8, 129.2, 129.7, 135.7, 154.7 ppm.
4.4. Synthesis of polystyrene-supported iron-containing ionic
liquid PS-MimFeCl4
4.7.3. 4-((Allyloxy)methyl)-1,3-dioxolan-2-one. Colorless liquid; 1H
NMR (400 MHz, CDCl3)
d
¼3.60e3.71 (m, 2H, OCH2), 4.05e4.07 (m,
3
A mixture of PS-CH2Cl (15.8 g), N-methyl imidazole (Mim)
(7.40 g, 90 mmol), and acetonitrile (70 mL) was heated at 80 ꢁC
for 24 h in a 250 mL three-necked flask. After cooled down to
room temperature, the solid residue was collected by filtration
and washed separately with ethyl acetate, 0.1 mol/L HCl, water,
and methanol. Then, the solid was dried under vacuum at 70 ꢁC
for 24 h to give PS-MimCl with a 96% yield. The loading of N-
2H, OCH2), 4.39e4.22 (m, 1H, OCH2), 4.50 (t, JHH¼8.4 Hz, 1H,
OCH2), 4.79e4.85 (m, 1H, OCH), 5.22e5.31 (m, 2H, ]CH2),
5.82e5.92 (m, 1H, CH]) ppm; 13C NMR (100.6 MHz, CDCl3)
d¼66.2,
68.8, 72.5, 75.0, 117.8, 133.6, 154.9 ppm.
4.7.4. 4-(Isopropoxymethyl)-1,3-dioxolan-2-one. Yellow liquid; 1H
3
NMR (400 MHz, CDCl3)
d
¼1.56 (d, JHH¼5.6 Hz, 6H, 2CH3),

J. Gao et al. / Tetrahedron 68 (2012) 3835e3842
3841
3.59e3.67 (m, 3H, OCH2, OCH), 4.37e4.40 (m, 1H, OCH2), 4.48 (t,
3JHH¼8.4 Hz, 1H, OCH2), 4.77e4.80 (m, 1H, OCH) ppm; 13C NMR
128.9, 134.8, 148.8, 155.6 ppm; ESI-MS calcd for C11H11NO2 189.21,
found m/z 410.29 (2MþNa)þ.
(100.6 MHz, CDCl3)
155.0 ppm.
d
¼21.6, 21.7, 66.2, 66.9, 72.6, 75.2,
Acknowledgements
4.7.5. Hexahydrobenzo[d][1,3]dioxol-2-one. White solid; 1H NMR
(400 MHz, CDCl3)
¼1.37e1.43 (m, 2H, CH2), 1.56e1.60 (m, 2H,
We are grateful to the National Natural Science Foundation of
China (21172125), the “111” Project of Ministry of Education of
China (Project No. B06005).
d
3
3
CH2), 1.86 (t, JHH¼3.6 Hz, 4H, 2CH2), 4.66 (t, JHH¼3.6 Hz, 2H,
2CH) ppm; 13C NMR (100.6 MHz, CDCl3)
ppm.
d
¼19.0, 26.6, 75.7, 155.3,
Supplementary data
4.7.6. 3-Ethyl-5-phenyloxazolidin-2-one. Colorless liquid; 1H NMR
Experimental information for the synthesis of ionic liquids,
azridine, propargyl amine, 1H, 13C NMR spectra and other charac-
terization data of the products and ionic liquids. Supplementary
data associated with this article can be found in the online version,
at doi:10.1016/j.tet.2012.03.048. These data include MOL files and
InChIKeys of the most important compounds described in this
article.
3
(300 MHz, CDCl3)
d
¼1.17 (t, JHH¼7.2 Hz, 3H), 3.29e3.45 (m, 3H),
3
3
3.92 (t, JHH¼8.7 Hz, 1H), 5.48 (t, JHH¼7.8 Hz, 1H), 7.34e7.42 (m,
5H) ppm; 13C NMR (75 MHz, CDCl3)
d
¼12.4, 38.8, 51.5, 74.2,
125.4, 128.6, 128.8, 138.8, 157.5 ppm; ESI-MS calcd for C11H13NO2
191.09, found 192.29 (MþH)þ, 214.38 (MþNa)þ, 405.01
(2MþNa)þ.
4.7.7. 3-Ethyl-4-phenyloxazolidin-2-one. Colorless liquid; 1H NMR
3
References and notes
(400 MHz, CDCl3)
d
¼1.05 (t, JHH¼7.2 Hz, 3H), 2.79e2.88 (m, 1H),
3
3
3.48e3.57 (m, 1H), 4.10 (t, JHH¼8.0 Hz, 1H), 4.62 (t, JHH¼8.8 Hz,
1. Arakawa, H.; Aresta, M. Chem. Rev. 2001, 101, 953e956.
2. Aresta, M.; Dibenedetto, A.; Tommasi, I. Energy Fuels 2001, 15, 269e273.
3. Omae, I. Catal. Today 2006, 115, 33e52.
4. Sakakura, T.; Choi, J. C.; Yasuda, H. Chem. Rev. 2007, 107, 2365e2387.
5. Clements, J. H. Ind. Eng. Chem. Res. 2003, 42, 663e674.
6. Yoshida, M.; Ihara, M. Chem.dEur. J. 2004, 10, 2886e2893.
7. Sun, J.-M.; Fujita, S. I.; Arai, M. J. Organomet. Chem. 2005, 690, 3490e3497.
8. Sakakura, T.; Kohno, K. Chem. Commun. 2009, 1312e1330.
9. Dai, W.-L.; Yin, S.-F.; Au, C.-T. Appl. Catal., A 2009, 366, 2e12.
3
1H), 4.81 (t, JHH¼7.2 Hz, 1H), 7.30e7.44 (m, 5H) ppm; 13C NMR
(75 MHz, CDCl3)
d
¼12.1, 36.8, 59.3, 69.7, 126.9, 129.0, 129.2, 137.8,
158.1 ppm; ESI-MS calcd for C11H13NO2 191.09, found 192.29
(MþH)þ, 214.38 (MþNa)þ, 405.01 (2MþNa)þ.
4.7.8. 3-Ethyl-5-p-tolyloxazolidin-2-one. White solid; 1H NMR
(400 MHz, CDCl3)
d
¼1.18 (t, 3JHH¼7.3 Hz, 3H), 1.62 (d, 3JHH¼6.4 Hz,
10. For amines and phosphines catalyzed cycloaddition of CO2 and epoxides see:
(a) Kawanami, H.; Ikushimaab, Y. Chem. Commun. 2000, 2089e2090; (b) Shen,
Y.-M.; Shi, M. Adv. Synth. Catal. 2003, 345, 337e340; (c) He, L.-N.; Yasuda, H.;
Sakakura, T. Green Chem. 2003, 5, 92e94; (d) Huang, J.-W.; Shi, M. J. Org. Chem.
2003, 68, 6705e6709.
11. For alkali metal halides and onium salts catalyzed cycloaddition of CO2 and
epoxides see: (a) Kihara, N.; Hara, N.; Endo, T. J. Org. Chem. 1993, 58,
6198e6202; (b) Calo, V.; Nacci, A.; Monopoli, A.; Fanizzi, A. Org. Lett. 2002, 4,
2561e2563; (c) Koseva, K.; Koseva, N.; Troev, K. J. Mol. Catal. A: Chem. 2003, 194,
29e37; (d) Sibaouih, A.; Repo, T. Appl. Catal., A 2009, 365, 194e198; (e) Tsut-
sumi, Y.; Yamakawa, K.; Yoshida, M.; Ema, T.; Sakai, T. Org. Lett. 2010, 12,
5728e5731.
12. For organometallic compounds-catalyzed cycloaddition of CO2 and epoxides
see: (a) Kruper, W. J.; Dellar, D. V. J. Org. Chem. 1995, 60, 725e727; (b) Paddock,
R. L.; Nguyen, S. T. J. Am. Chem. Soc. 2001, 123, 11498e11499; (c) Lu, X.-B.; Wang,
H.; He, R. J. Mol. Catal. A: Chem. 2002, 186, 33e42; (d) Li, F.-W.; Xia, C.-G.; Xu, L.-
W.; Sun, W.; Chen, G.-X. Chem. Commun. 2003, 2042e2043; (e) Barbarini, A.;
Maggi, R.; Mazzacani, A.; Mori, G.; Sartori, G.; Sartorio, R. Tetrahedron Lett. 2003,
44, 2931e2934; (f) Du, Y.; Kong, D.-L.; Wang, H.-Y.; Cai, F.; Tian, J.-S.; Wang, J.-
Q.; He, L.-N. J. Mol. Catal. A: Chem. 2005, 241, 233e237; (g) Jutz, F.; Grunwaldt, J.
D.; Baiker, A. J. Mol. Catal. A: Chem. 2008, 279, 94e103; (h) Miao, C.-X.; Wang, J.-
Q.; Wu, Y.; Du, Y.; He, L.-N. ChemSusChem 2008, 1, 236e241; (i) Kleist, W.;
Baiker, A. Eur. J. Inorg. Chem. 2009, 3552e3561; (j) Sibaouih, A.; Repo, T. J. Mol.
Catal. A: Chem. 2009, 312, 87e91; (k) Melendez, J.; North, M. Chem. Commun.
2009, 2577e2579; (l) Clegg, W.; Harrington, R. W.; North, M.; Pasquale, R.
Chem.dEur. J. 2010, 16, 6828e6843; (m) Decortes, A.; Belmonte, M. M.; Benet-
Buchholza, J.; Kleij, A. W. Chem. Commun. 2010, 4580e4582; (n) Dengler, J. E.;
Lehenmeier, M. W.; Klaus, S.; Anderson, C. E.; Herdtweck, E.; Rieger, B. Eur. J.
Inorg. Chem. 2011, 3, 336e343; (o) Jaisiel, M.; Michael, N.; Pedro, V.; Carl, Y.
Dalton Trans. 2011, 40, 3885e3902; (p) Buchard, A.; Kember, M. R.; Sandemanb,
K. G.; Williams, C. K. Chem. Commun. 2011, 212e214.
3
3
2
1H), 1.87 (d, JHH¼3.2 Hz, 1H), 2.27 (dd, JHH¼6.6 Hz, JHH¼3.2 Hz,
1H), 2.31 (s, 3H), 2.36e2.48 (m, 2H), 7.09e7.15 (m, 4H) ppm; 13C
NMR (100 MHz, CDCl3)
d
¼12.6, 21.2, 38.9, 51.6, 74.3, 125.6, 129.5,
135.8, 138.7, 157.7 ppm; ESI-MS calcd for C12H15NO2 205.25, found
206.45 (MþH)þ, 411.15 (2MþH)þ.
4.7.9. 3-Ethyl-5-(4-chlorophenyl)oxazolidin-2-one. White solid; 1H
3
NMR (400 MHz, CDCl3)
d
¼1.17 (t, JHH¼7.3 Hz, 3H), 3.30e3.43 (m,
3
2H), 3.69e3.76 (m, 1H), 3.92 (t, JHH¼8.7 Hz, 1H), 5.44 (t,
3JHH¼8.0 Hz, 1H), 7.27e7.38 (m, 4H) ppm; 13C NMR (100 MHz,
CDCl3)
d
¼12.6, 38.9, 51.5, 73.6, 126.9, 129.1, 134.7, 137.4,
157.4 ppm; ESI-MS calcd for C11H12ClNO2 225.67, found 451.64
(2MþH)þ.
4.7.10. 3-Propyl-5-phenyloxazolidin-2-one. Colorless liquid; 1H
3
NMR (300 MHz, CDCl3)
d
¼0.91 (t, JHH¼7.2 Hz, 3H), 1.52e1.61 (m,
3
2H), 3.18e3.31 (m, 2H) 3.40 (t, JHH¼8.0 Hz, 1H), 3.90 (t,
3JHH¼8.8 Hz, 1H), 5.46 (t, JHH¼8.0 Hz, 1H), 7.31e7.37 (m,
3
5H) ppm; 13C NMR (75 MHz, CDCl3)
d
¼10.7, 20.3, 45.5, 51.8, 74.0,
125.2, 128.4, 128.5, 138.7, 157.6 ppm; ESI-MS calcd for C12H15NO2
205.11, found 206.30 (MþH)þ, 228.30 (MþNa)þ, 433.04
(2MþNa)þ.
4.7.11. 3-Isobutyl-5-phenyloxazolidin-2-one. White crystals; mp
13. (a) Zhou, H.; Lu, X.-B. J. Org. Chem. 2008, 73, 8039e8044; (b) Kayaki, Y.; Ya-
mamoto, M.; Ikariya, T. Angew. Chem., Int. Ed. 2009, 48, 4194e4197.
14. For ILs-catalyzed cycloaddition of CO2 and epoxides see: (a) Peng, J.-J.; Deng, Y.-
Q. New J. Chem. 2001, 25, 639e641; (b) Kim, H. S.; Kim, J. J.; Kim, H.; Jang, H. G. J.
Catal. 2003, 220, 44e46; (c) Kawanami, H.; Sasaki, A.; Matsui, K.; Ikushima, Y.
Chem. Commun. 2003, 896e897; (d) Sun, J.-M.; Fujita, S. I.; Zhao, F.-Y.; Arai, M.
Green Chem. 2004, 6, 613e616; (e) Li, F.-W.; Xiao, L.-F.; Xia, C.-G.; Hu, B. Tet-
rahedron Lett. 2004, 45, 8307e8310; (f) Palgunadi, J.; Kim, H. S. Catal. Today
2004, 98, 511e514; (g) Kim, Y. J.; Varma, R. S. J. Org. Chem. 2005, 70, 7882e7891;
(h) Sun, J.; Zhang, S.-J. Tetrahedron Lett. 2008, 49, 3588e3591; (i) Zhou, Y.-X.;
Hu, S.-Q.; Ma, X.-M.; Liang, S.-G.; Jiang, T.; Han, B.-X. J. Mol. Catal. A: Chem. 2008,
284, 52e57; (j) Sun, J.; Ren, J.-Y.; Zhang, S.-J.; Cheng, W.-G. Tetrahedron Lett.
2009, 50, 423e426; (k) Yang, Z.-Z.; He, L.-N.; Miao, C.-X.; Chanfreau, S. Adv.
Synth. Catal. 2010, 352, 2233e2240; (l) Kumar, S.; Jain, S. L.; Sain, B. Tetrahedron
Lett. 2011, 52, 6957e6959; (m) Sun, J.; Han, L. J.; Cheng, W. G.; Wang, J. Q.;
Zhang, X. P.; Zhang, S. J. ChemSusChem 2011, 4, 502e507.
38e42 ꢁC; 1H NMR (300 MHz, CDCl3)
d
¼0.91 (d, 3JHH¼4.8 Hz, 3H),
0.93 (d, 3JHH¼4.8 Hz, 3H), 1.81e1.95 (m, 1H), 3.02e3.16 (m, 2H), 3.42
(dd, 2JHH¼8.7 Hz, 3JHH¼7.5 Hz, 1H), 3.91 (t, 3JHH¼8.7 Hz, 1H), 5.48 (t,
3JHH¼8.4 Hz, 1H), 7.32e7.41 (m, 5H) ppm; 13C NMR (75 MHz, CDCl3)
d
¼19.7, 19.8, 26.7, 51.6, 52.6, 74.1, 125.3, 128.5, 128.7, 138.8,
158.0 ppm; ESI-MS calcd for C13H17NO2 219.13, found 461.22
(2MþNa)þ, 679.70 (3MþNa)þ.
4.7.12. 3-Benzyl-5-methyleneoxazolidin-2-one. Light yellow solid;
mp: 51e52 ꢁC 1H NMR (400 MHz, CDCl3)
d
¼4.02 (t, 3JHH¼2.4 Hz, 2H,
CH3), 4.24 (dd, 3JHH¼5.2 Hz, 3JHH¼2.4 Hz, 1H, CH), 4.47 (s, 2H, CH2),
3
3
4.74 (dd, JHH¼5.6 Hz, JHH¼2.8 Hz, 1H, CH), 7.29e7.39 (m, 5H,
15. For reviews on ionic liquids see: (a) Wasserscheid, P.; Welton, T. Ionic Liquids in
Synthesis, 2nd ed.; Wiley-VCH: Weinheim, 2008; (b) Parvulescu, V. I.; Hardacre,
ArH) ppm; 13C NMR (100.6 MHz, CDCl3)
d¼47.1, 47.8, 86.7, 128.1,

3842
J. Gao et al. / Tetrahedron 68 (2012) 3835e3842
C. Chem. Rev. 2007, 107, 2615e2665; (c) Olivier-Bourbigou, H.; Magna, L.;
Morvan, D. Appl. Catal., A 2010, 373, 1e56.
Catal. Lett. 2010, 135, 295e304; (k) Xie, Y.; Ding, K.-L.; Liu, Z.-M.; Li, J.-J.; An, G.-
M.; Tao, R.-T.; Sun, Z.-Y.; Yang, Z.-Z. Chem.dEur. J. 2010, 16, 6687e6692; (l)
Zhou, H.; Wang, Y.-M.; Zhang, W.-Z.; Qu, J.-P.; Lu, X.-B. Green Chem. 2011, 13,
644e650; (m) Han, L.; Choi, H.-J.; Choi, S.-J.; Liu, B.-Y.; Park, D.-W. Green Chem.
2011, 13, 1023e1028.
16. For metal oxide-promoted cycloaddition of CO2 and epoxides see: (a) Yano, T.;
Matsui, H.; Koike, T.; Ishiguro, H.; Fujihara, H.; Yoshihara, M.; Maeshima, T.
Chem. Commun. 1997, 1129e1130; (b) Yamaguchi, K.; Ebitani, K.; Yoshida, T.;
Yoshida, H.; Kaneda, K. J. Am. Chem. Soc. 1999, 121, 4526e4527; (c) Bhanage, B.
M.; Fujita, S.; Ikushima, Y.; Arai, M. Appl. Catal., A 2001, 219, 259e266; (d)
Aresta, M.; Dibenedetto, A.; Gianfrate, L.; Pastore, C. J. Mol. Catal. A: Chem. 2003,
204/205, 245e252; (e) Yasuda, H.; He, L.-N.; Takahashi, T.; Sakakura, T. Appl.
Catal., A 2006, 298, 177e180; (f) Dai, W. L.; Yin, S. F.; Guo, R.; Luo, S. L.; Du, X.;
Au, C. T. Catal. Lett. 2010, 136, 35e44.
21. Srivastava, R.; Srinivas, D.; Ratnasamy, P. Appl. Catal., A 2005, 289, 128e134.
22. (a) Srivastava, R.; Srinivas, D.; Ratnasamy, P. J. Catal. 2005, 233, 1e15; (b) Zheng,
X.-X.; Luo, S.-Z.; Cheng, J.-P. Green Chem. 2009, 11, 455e458; (c) Song, J.; Han,
B.-X. Green Chem. 2009, 11, 1031e1036; (d) Cho, H. C.; Lee, H. S.; Chun, J.; Lee, S.
M.; Kimb, H. J.; Son, S. U. Chem. Commun. 2011, 917e919; (e) Yang, Z.-Z.; Zhao,
Y.-N.; He, L.-N.; Gao, J.; Yin, Z.-S. Green Chem. 2012, 14, 519e527; (f) Liang, S.-G.;
Liu, H.-Z.; Jiang, T.; Song, J.-L.; Yang, G.-Y.; Han, B.-X. Chem. Commun. 2011,
2131e2133.
17. Yasuda, H.; He, L.-N.; Sakakura, T. J. Catal. 2002, 209, 547e550.
18. Tu, M.; Davis, R. J. J. Catal. 2001, 199, 85e91.
19. For polymer supported catalyst for cycloaddition of CO2 with epoxide, see: (a)
Nishikubo, T.; Kameyama, A.; Yamashita, J.; Tomoi, M.; Fukuda, W. J. Polym. Sci.,
Part A: Polym. Chem. 1993, 31, 939e947; (b) Kim, H. S.; Kim, J. J.; Kwon, H.-N.;
Chung, M. J.; Lee, B. G.; Jang, H. G. J. Catal. 2002, 205, 226e229; (c) Du, Y.; Cai, F.;
Kong, D.-L.; He, L.-N. Green Chem. 2005, 7, 518e523; (d) Xiao, L.-F.; Li, F.-W.; Xia,
C.-G. Appl. Catal., A 2005, 279, 125e129; (e) Du, Y.; Wang, J.-Q.; Chen, J.-Y.; Cai,
F.; Tian, J.-S.; Kong, D.-L.; He, L.-N. Tetrahedron Lett. 2006, 47, 1271e1275; (f)
Zhao, Y.; He, L.-N. J. Mol. Catal. A: Chem. 2007, 271, 284e289; (g) Xie, Y.; Han, B.-
X. Angew. Chem., Int. Ed. 2007, 46, 7255e7258; (h) Sun, J.; Cheng, W.-G.; Fan, W.;
Wang, Y.-H.; Meng, Z.-Y.; Zhang, S.-J. Catal. Today 2009, 148, 361e367; (i) Qi, C.-
R.; Ye, J.-W.; Zeng, W.; Jiang, H.-F. Adv. Synth. Catal. 2010, 352, 1925e1933; (j)
Dai, W.-L.; Chen, L.; Yin, S.-F.; Li, W.-H.; Zhang, Y.-Y.; Luo, S.-L.; Au, C.-T. Catal.
Lett. 2010, 137, 74e80; (k) Xiong, Y.-B.; Wang, H.; Wang, R.-M.; Yan, Y.-F.; Zheng,
B.; Wang, Y.-P. Chem. Commun. 2010, 3399e3401; (l) Han, L.; Choi, H.-J.; Kima,
D.-K.; Parka, S.-W.; Liu, B.-Y.; Park, D.-W. J. Mol. Catal. A: Chem. 2011, 338, 58e64.
20. Silica supported catalysts for cycloaddition of CO2 with epoxide: (a) Xie, H.-B.;
Duan, H.-F.; Li, S.-H.; Zhang, S.-B. New J. Chem. 2005, 29, 1199e1203; (b) Wang,
J.-Q.; Kong, D.-L.; Chen, J.-Y.; Cai, F.; He, L.-N. J. Mol. Catal. A: Chem. 2006, 249,
143e148; (c) Xiao, L.-F.; Xia, C.-G. J. Mol. Catal. A: Chem. 2006, 253, 265e269; (d)
Takahashi, T.; Watahiki, T.; Kitazume, S.; Yasuda, H.; Sakakura, T. Chem. Com-
mun. 2006, 1664e1666; (e) Wang, J.-Q.; Yue, X.-D.; Cai, F.; He, L.-N. Catal.
Commun. 2007, 8, 167e172; (f) Sakai, T.; Tsutsumi, Y. Green Chem. 2008, 10,
337e341; (g) Motokura, K.; Itagaki, S. Green Chem. 2009, 11, 1876e1880; (h)
Udayakumar, S.; Lee, M. K.; Shim, H. L.; Park, D. W. Appl. Catal., A 2009, 365,
88e95; (i) Udayakumar, S.; Lee, M. K.; Shim, H. L.; Park, S. W.; Park, D. W. Catal.
Commun. 2009, 10, 659e664; (j) Dai, W. L.; Chen, L.; Yin, S. F.; Luo, S. L.; Au, C. T.
23. Applications of iron-containing ionic liquids in catalysis: (a) Li, M.; De Rooy, S.
L.; Bwambok, D. K.; El-Zahab, B.; DiTusa, J. F.; Warner, I. M. Chem. Commun.
2009, 45, 6922e6924; (b) Yoshida, Y.; Saito, G. Phys. Chem. Chem. Phys. 2010, 12,
1675e1684; (c) Gao, J.; Wang, J.-Q.; Song, Q.-W.; He, L.-N. Green Chem. 2011, 13,
1182e1186.
24. For reviews on iron catalysis see: (a) Bolm, C.; Legros, J.; LePaih, J.; Zani, L. Chem.
€
Rev. 2004, 104, 6217e6254; (b) Furstner, A.; Martin, R. Chem. Lett. 2005, 34,
624e629; (c) Plietker, B. Iron Catalysis in Organic Chemistry: Reactions and Ap-
€
plications; Wiley-VCH: Weinheim, Germany, 2008; (d) Sherry, B. D.; Furstner, A.
Acc. Chem. Res. 2008, 41, 1500e1511; (e) Enthaler, S.; Junge, K.; Beller, M. Angew.
~
Chem., Int. Ed. 2008, 47, 3317e3321; (f) Correa, A.; Mancheno, O. G.; Bolm, C.
Chem. Soc. Rev. 2008, 37, 1108e1117; (g) Sarhan, A. A. O.; Bolm, C. Chem. Soc. Rev.
2009, 38, 2730e2744; (h) Nakamura, E.; Yoshikai, N. J. Org. Chem. 2010, 75,
6061e6067; (i) Sun, C.-L.; Li, B.-J.; Shi, Z.-J. Chem. Rev. 2011, 111, 1293e1314 and
references therein.
25. For a comprehensive list of alternative supports, see: Hudson, D. J. Comb. Chem.
1999, 1, 403e457.
26. (a) Heinze, K.; Winterhalter, U.; Jannack, T. Chem.dEur. J. 2000, 6, 4203e4210;
(b) Toy, P. H.; Reger, T. S.; Garibay, P.; Garno, J. C.; Malikayil, J. A.; Liu, G. Y.;
Janda, K. D. J. Comb. Chem. 2001, 3, 117e124; (c) McClain, A.; Hsieh, Y. L. J. Appl.
Polym. Sci. 2004, 92, 218e225.
27. Bica, K.; Gaertner, P. Org. Lett. 2006, 8, 733e735.
28. For metals assisted fixation of CO2 see: (a) Kim, H. S.; Kim, J. J.; Lee, B. G.; Jung,
Q. S.; Jang, H. G.; Kang, S. O. Angew. Chem., Int. Ed. 2000, 39, 4096e4098; (b)
Shibata, I.; Mitani, I.; Imakuni, A.; Baba, A. Tetrahedron Lett. 2011, 52, 721e723.
29. Jain, N.; Kumar, A.; Chauhan, S. M. S. Tetrahedron Lett. 2005, 46, 2599e2602.