Environmentally benign chemical fixation of CO2 catalyzed by the functionalized ion-exchange resins

Article abstract of DOI:10.1007/s11426-010-4028-6

Basic ion-exchange resins, one kind of polystyryl-supported tertiary amine, were demonstrated to be highly efficient and recyclable catalysts for the fixation of carbon dioxide with aziridines under mild conditions, leading to the formation of 5-aryl-2-oxazolidinone with excellent regio-selectivities. Notably, neither solvents nor any additives were required, and the catalyst could be recovered by simple filtration and directly reused at least five times without significant loss of catalytic activity and selectivity. The present protocol has been applied to reactions of epoxides/propargyl amines with CO ₂/CS₂. This solvent-free process thus represents environmentally friendly catalytic conversion of CO₂ into value-added chemicals and may have potential in various continuous flow reactors in industry.

Full text of DOI:10.1007/s11426-010-4028-6

SCIENCE CHINA
Chemistry
July 2010 Vol.53 No.7: 1578–1585
doi: 10.1007/s11426-010-4028-6
• ARTICLES •
Environmentally benign chemical fixation of CO2 catalyzed by the
functionalized ion-exchange resins
LIU AnHua, HE LiangNian*, PENG ShiYong, PAN ZhongDa, WANG JingLun & GAO Jian
State Key Laboratory of Elemento-Organic Chemistry; Institute of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, China
Received March 10, 2010; accepted June 9, 2010
Basic ion-exchange resins, one kind of polystyryl-supported tertiary amine, were demonstrated to be highly efficient and recy-
clable catalysts for the fixation of carbon dioxide with aziridines under mild conditions, leading to the formation of 5-aryl-2-
oxazolidinone with excellent regio-selectivities. Notably, neither solvents nor any additives were required, and the catalyst
could be recovered by simple filtration and directly reused at least five times without significant loss of catalytic activity and
selectivity. The present protocol has been applied to reactions of epoxides/propargyl amines with CO2/CS2. This solvent-free
process thus represents environmentally friendly catalytic conversion of CO2 into value-added chemicals and may have poten-
tial in various continuous flow reactors in industry.
cycloaddition, carbon dioxide, aziridine, ion-exchange resin, solvent-free process
1 Introduction
Carbon dioxide, as the main green house gas, is widely
blamed to take most of the responsibility for the disaster of
global warming [1, 2]. Governments all around the world
are struggling to reduce the national carbon emission, in
which CO2 accounts for the largest share. However, on the
other side of the coin, a safe, cheap and abundant C1 build-
ing block in organic synthesis comes to light, which acts as
a sustainable carbon source for the potential transformations
[3]. Chemical fixation of CO2 into industrially useful mate-
rials turns to be one of the most attractive methods in recent
years. In particular, synthesis of medicinally valuable [4–7]
and synthetically useful five-membered cyclic urethanes
[8–12] such as 5-substituted oxazolidinones via the coupling
of CO2 with aziridines (Scheme 1) has become one of the
most promising methodologies in this area, because this
process has 100% atom efficiency, which exactly matches
one of the most significant demands of green chemistry [13].
Scheme 1 Synthesis of 2-oxazolidinone from aziridine and CO2.
In this respect, a large number of reports have been pub-
lished on this kind of CO2 conversion, such as dual-com-
ponent system viz. SalenCr(III)/DMAP [14] or Phenol/
DMAP [15], iodine [16, 17], alkali metal halide [18–20],
tetraalkyl ammonium halide [20], and recent naturally oc-
curring amino acids [21]. Particularly, we have reported that
PEG functionalized quaternary ammonium bromide [22]
and zirconyl chloride [23] were extremely active for this
reaction under supercritical CO2 conditions. Concurrently,
analogous cycloadditions of epoxides [24–31] and propargyl
amines [32–37] with CO2 to produce industrially useful
cyclic carbonates [38, 39] and alkylene urethanes [40, 41]
have also been reported intensively, offering alternative
pathways for chemical utilization of CO2 as a renewable
feedstock. However, most of the above catalysts failed to
*Corresponding author (email: heln@nankai.edu.cn)
© Science China Press and Springer-Verlag Berlin Heidelberg 2010
chem.scichina.com
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LIU AnHua, et al. Sci China Chem July (2010) Vol.53 No.7
1579
meet the current industrial demands because of at least one
of such drawbacks: Requirements of high CO2 pressure,
high temperature, or toxic additives/co-solvents, employ-
ment of expensive catalysts made by complicated multiple
steps along with troublesome handling of catalyst separation.
In this context, developing environmentally benign proc-
esses for catalytic fixation of CO2 would still be desirable.
Most of the documented cycloadditions of aziridines with
CO2 were catalyzed by acidic catalysts or the ones with an
acidic center, which usually acts as an aziridine ring-opening
promoter (vide supra). Activation of CO2 itself by a nu-
cleophilic species should not be neglected. There have been
numerous reports about interactions between CO2 and terti-
ary amines [42–45]. The catalytic utilization in chemical
fixation of CO2 was intensively investigated as well [46–52].
Therefore, in this work we report a green process for CO2
fixation by employing the functionalized ion exchange res-
ins, one kind of polystyryl supported tertiary amines, as
effective catalysts under mild reaction conditions without
any organic solvents and co-catalysts. Notably, the catalyst
could be reused at least five times.
magnetic stirrer, the substrate (1 mmol), catalyst (ion-ex-
change resin, 0.05 mmol), and biphenyl (50 mg, an internal
standard for GC analysis) were charged. Then CO2 was
introduced into the autoclave. The pressure was adjusted to
the designed pressure at 373 K, and the mixture was stirred
for the appropriate time. 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. The residue was purified by
column chromatography on silica gel (200–300 mesh,
eluting with 4:1 to 2:1 petroleum ether/ethyl acetate) to pro-
vide the desired products.
3-Ethyl-5-phenyloxazolidin-2-one (2a)
Colorless liquid. 1H NMR (400 MHz, CDCl3)  ppm 1.18 (t,
3
3J = 6.4 Hz, 3H), 3.32–3.46 (m, 3H), 3.93 (t, J = 8.2 Hz,
1H), 5.49 (t, 3J = 7.8 Hz, 1H), 7.27–7.41 (m, 5H); 13C NMR
(100 MHz, CDCl3)  ppm 12.6, 38.9, 51.6, 74.3, 125.5,
128.8, 128.9, 138.8, 157.7; ESI-MS calcd for C11H13NO2
191.09, found m/z 192.29 (M + H)+, 214.38 (M + Na)+,
405.01 (2M + Na)+.
3-Ethyl-4-phenyloxazolidin-2-one (3a)
Colorless liquid. 1H NMR (400 MHz, CDCl3)  ppm 1.05 (t,
2 Experimental
3J = 7.2 Hz, 3H), 2.79–2.88 (m, 1H), 3.48–3.57 (m, 1H),
2.1 Apparatus and reagents
3
3
4.10 (t, J = 8.0 Hz, 1H), 4.62 (t, J = 8.8 Hz, 1H), 4.81 (t,
3J = 7.2 Hz, 1H) 7.30–7.44 (m, 5H); 13C NMR (100 MHz,
CDCl3)  ppm 12.1, 36.8, 59.3, 69.7, 126.9, 129.0, 129.2,
137.8, 158.1; ESI-MS calcd for C11H13NO2 191.09, found
m/z 192.29 (M + H)+, 214.38 (M + Na)+, 405.01 (2M + Na)+.
1H NMR spectra were recorded on Bruker 300 or Bruker
400 spectrometer in CDCl3 and TMS (0 ppm) was used as
the internal reference. 13C NMR was recorded at 75 or 100
MHz in CDCl3 and CDCl3 (77.0 ppm) was used as the in-
ternal reference. GC analysis was performed on Shimadzu
GC-2014, equipped with a capillary column (RTX-5, 30 m
× 0.25 m) using a flame ionization detector and ESI-MS
with spray voltage of 4.8 kV. High-resolution mass spec-
trometry was conducted using an Ionspec 7.0T spectrometer
by ESI-FTICR technique. Melting points were measured on
an X4 apparatus and uncorrected. All the ion-exchange res-
ins were supplied by the Chemical Plant of Nankai Univer-
sity, and the characteristics of them are shown in Table 1.
Prior to the reaction, all of the ion-exchange resins used in
this study were evacuated at 373 K for 3 h. Aziridines [53]
and propargyl amines [54] were synthesized according to
previously published procedures. Epoxides were purchased
from Acros Organics. Carbon dioxide with a purity of
99.99% was commercially available. The other organic and
inorganic compounds from Tianjin Guangfu Fine Chemical
Research Institute were used without further purification
except for the solvents, which were distilled by the known
method prior to use.
5-Phenyloxazolidin-2-one (2b)
White crystal, mp 85–86 °C. 1H NMR (400 MHz, CDCl3) 
3
3
ppm 3.55 (t, J = 8.4 Hz, 1H), 3.99 (t, J=8.4 Hz, 1H), 5.62
3
(t, J = 8.4 Hz, 1H), 6.08 (br s, 1H), 7.35–7.43 (m, 5H); 13
C
NMR (100 MHz, CDCl3)  ppm 48.2, 77.8, 125.6, 128.9,
138.4, 160.1; ESI-MS calcd for C9H9NO2 163.06, found m/z
164.18 (M + H)+, 186.28 (M + Na)+, 349.03 (2M + Na)+.
3-Methyl-5-phenyloxazolidin-2-one (2c)
1
White solid, mp: 50–52 °C. H NMR (400 MHz, CDCl3) 
3
3
ppm 2.89 (s, 3H), 3.42 (t, J = 8.4 Hz, 1H), 3.90 (t, J = 8.4
3
Hz, 1H), 5.45 (t, J = 8.0 Hz, 1H), 7.33–7.38 (m, 5H); 13C
NMR (100 MHz, CDCl3)  ppm 30.7, 54.0, 73.0, 125.3,
128.5, 128.6, 138.4, 157.9; ESI-MS calcd for C10H11NO2
177.08, found m/z 178.21 (M + H)+, 200.25 (M + Na)+,
377.00 (2M + Na)+.
3-propyl-5-phenyloxazolidin-2-one (2d)
Colorless liquid. 1H NMR (400 MHz, CDCl3)  ppm 0.93 (t,
3J = 7.4 Hz, 3H), 1.54–1.63 (m, 2H), 3.20–3.34 (m, 2H),
2.2 General procedure for the cycloaddition reaction
with CO2
3
3
3.43 (t, J = 8.0 Hz, 1H), 3.92 (t, J = 8.8 Hz, 1H), 5.49 (t,
3J = 8.2 Hz, 1H), 7.34–7.44 (m, 5H); 13C NMR (100 MHz,
CDCl3)  ppm 11.1, 20.7, 45.8, 52.1, 74.3, 125.5, 128.8,
In a 25 mL autoclave reactor with a quartzose tube and a

1580
LIU AnHua, et al. Sci China Chem July (2010) Vol.53 No.7
128.9, 138.9, 158.0; ESI-MS calcd for C12H15NO2 205.11,
found m/z 206.30 (M+H)+, 228.30 (M +Na)+, 433.04 (2M+
Na)+.
2.31 (s, 3H), 2.36–2.48 (m, 2H), 7.09–7.15 (m, 4H); 13C
NMR (100 MHz, CDCl3)  ppm 12.6, 21.2, 38.9, 51.6, 74.3,
125.6, 129.5, 135.8, 138.7, 157.7; ESI-MS calcd for
C12H15NO2 205.25, found m/z 206.45 (M + H)+, 411.15 (2M
+ H)+.
3-butyl-5-phenyloxazolidin-2-one (2e)
Colorless liquid. 1H NMR (300 MHz, CDCl3)  ppm 0.93 (t,
3J = 7.4 Hz, 3H), 1.31–1.64 (m, 4H), 3.23–3.35 (m, 2H),
5-(4-Chlorophenyl)-3-ethyloxazolidin-2-one (2k)
3
3
White solid, mp: 70–74 °C. 1H NMR (400 MHz, CDCl3) 
3.43 (t, J = 8.1 Hz, 1H), 3.91 (t, J = 8.9 Hz, 1H), 5.49 (t,
3J = 8.1 Hz, 1H), 7.34–7.44 (m, 5H); 13C NMR (75 MHz,
CDCl3)  ppm 13.4, 19.5, 29.1, 43.6, 51.8, 74.1, 125.2,
128.4, 128.5, 138.7, 157.7; ESI-MS calcd for C13H17NO2
219.13, found m/z 220.34 (M + H)+, 259.48 (M + K)+,
461.05 (2M + Na)+.
ppm 1.17 (t, 3J = 7.3 Hz, 3H), 3.30–3.43 (m, 2H), 3.69–3.76
3
3
(m, 1H), 3.92 (t, J = 8.7 Hz, 1H), 5.44 (t, J = 8.0 Hz, 1H),
7.27–7.38 (m, 4H); 13C NMR (100 MHz, CDCl3)  ppm
12.6, 38.9, 51.5, 73.6, 126.9, 129.1, 134.7, 137.4, 157.4;
ESI-MS calcd for C11H12ClNO2 225.67, found m/z 451.64
(2M + H)+.
3-Isobutyl-5-phenyloxazolidin-2-one (2f)
1
1,4-Diethyl-2,5-diphenylpiperazine (4a)
White solid, mp: 38–42 °C. H NMR (400 MHz, CDCl3) 
ppm 0.93 (d, 3J = 6.8 Hz, 6H), 1.85–1.92 (m, 1H), 3.04–3.17
White solid, mp: 116–119 °C. H NMR (300 MHz, CDCl3)
1
3
3
3
(m, 2H), 3.43 (t, J = 8.0 Hz, 1H), 3.92 (t, J = 8.8 Hz, 1H),
 ppm 0.91 (t, J = 7.2 Hz, 6H), 1.99–2.05 (m, 2H), 2.30 (t,
5.50 (t, J = 8.2 Hz, 1H), 7.35–7.41 (m, 5H); 13C NMR (100
3
3J = 10.8 Hz, 2H), 2.54–2.62 (m, 2H), 3.08 (dd, 3J=11.6 Hz,
2
3
MHz, CDCl3)  ppm 18.8, 18.9, 25.8, 50.8, 51.8, 73.3,
124.4, 127.7, 127.9, 137.9, 158.0; ESI-MS calcd for
C13H17NO2 219.13, found m/z 461.22 (2M + Na)+, 679.70
(3M + Na)+.
2J = 2.4 Hz, 2H), 3.45 (dd, J = 2.0 Hz, J = 12.0 Hz, 2H),
7.29–7.43 (m, 10H); HRMS calcd for C20H26N2 (M + H)+
295.2169, found m/z 295.2164.
1,4-Diethyl-2,3-diphenyl-piperazine (5a)
Colorless liquid. 1H NMR (300 MHz, CDCl3)  ppm 1.01 (t,
3-Tert-butyl-5-phenyloxazolidin-2-one (2g)
Colorless liquid. 1H NMR (300 MHz, CDCl3)  ppm 1.41 (s,
9H), 3.45 (t, 3J = 8.4 Hz , 1H), 3.95 (t, 3J=8.7 Hz, 1H), 5.36
(t, 3J = 8.1 Hz, 1H), 7.32–7.41 (m, 5H); 13C NMR (75 MHz,
CDCl3)  ppm 27.3, 50.9, 53.5, 73.4, 125.4, 128.5, 128.7,
138.9, 156.6; ESI-MS calcd for C13H17NO2 219.13, found
m/z 242.46 (M + Na)+, 259.30 (M + K)+.
3J = 7.2 Hz, 6H), 2.17–2.26 (m, 2H), 2.33–2.26 (m, 2H),
3
2.65–2.69 (m, 2H), 2.95–2.99 (q, J = 6.0 Hz, 2H), 3.73 (s,
3
2H), 7.27–7.38 (m, 6H), 7.69–7.71 (d, J = 7.2 Hz, 4H);
HRMS: calcd for C20H26N2 (M + H)+ 295.2169, found
295.2167.
4-phenyldioxolan-2-one (7a)
1
3-Cyclohexyl-5-phenyloxazolidin-2-one (2h)
White solid, mp: 55–56 °C. H NMR (400 MHz, CDCl3) 
3
3
1
ppm 4.35 (t, J = 8.4 Hz, 1H), 4.80 (t, J=8.4 Hz, 1H), 5.68
White solid, mp: 92–93 °C. H NMR (400 MHz, CDCl3) 
3
ppm 1.13–1.9 (m, 10H), 3.40 (t, 3J = 8.0 Hz, 1H), 3.72–3.78
(t, J = 8.0 Hz, 1H), 7.36–7.38 (m, 2H), 7.43–7.47 (m, 3H);
3
3
13C NMR (100 MHz, CDCl3)  ppm 71.1, 78.0, 125.9,
129.3, 129.8, 135.8, 154.8; ESI-MS calcd for C9H8O3
164.16, found m/z 351.26 (2M + Na)+, 367.68 (2M + K)+.
(m, 1H), 3.88 (t, J = 8.8 Hz, 1H), 5.47 (t, J = 8.2 Hz, 1H),
7.34–7.42 (m, 5H); 13C NMR (100 MHz, CDCl3)  ppm
25.1, 25.2, 29.9, 30.3, 48.1, 52.4, 74.4, 125.3, 128.5, 128.7,
138.9, 157.0; ESI-MS calcd for C15H19NO2 245.14, found
m/z 246.27 (M + H)+, 757.70 (3M + Na)+.
3-Benzyl-5-methyleneoxazolidin-2-one (9a)
1
Light yellow solid, mp: 51–52 °C. H NMR (400 MHz,
CDCl3)  ppm 4.02 (t, 3J=2.4 Hz, 2H), 4.24 (dd, 3J=5.2 Hz,
3-Benzyl-5-phenyloxazolidin-2-one (2i)
1
3
2J = 2.4 Hz, 1H), 4.47 (s, 2H), 4.74 (dd, J = 5.6 Hz, 3J=2.8
White solid, mp: 60–64 °C. H NMR (400 MHz, CDCl3) 
3
3
Hz, 1H), 7.29–7.39 (m, 5H); 13C NMR (100 MHz, CDCl3) 
ppm 47.2, 47.8, 86.8, 128.2, 129.0, 134.9, 148.9, 155.6;
ESI-MS calcd for C11H11NO2 189.21, found m/z 410.29 (2M
+ Na)+.
ppm 3.31 (t, J = 8.0 Hz, 1H), 3.77 (t, J=8.8 Hz, 1H), 4.48
3
(ABq, JAB = 15.2 Hz, vAB = 37.8 Hz, 2H), 5.47 (t, J = 8.2
Hz, 1H), 7.28–7.38 (m, 10H); 13C NMR (100 MHz, CDCl3)
 ppm 48.4, 51.6, 74.5, 125.5, 128.0, 128.2, 128.8, 128.9,
135.6, 138.6, 158.0; ESI-MS calcd for C16H15NO2 253.11,
found m/z 276.44 (M + Na)+, 781.66 (3M + Na)+.
2.3 General procedure for the coupling reaction with CS2
3-Ethyl-5-p-tolyloxazolidin-2-one (2j)
In a 25 mL autoclave reactor with a quartzose tube and a
magnetic stirrer, the substrate (1 mmol), catalyst (ion-ex-
change resin, 0.05 mmol), and biphenyl (50 mg) were
charged. Then CS2 (1 mL) was added into the autoclave.
White solid, mp: 48–50 °C. 1H NMR (400 MHz, CDCl3) 
ppm 1.18 (t, 3J = 7.3 Hz, 3H), 1.62 (d, 3J=6.4 Hz, 1H), 1.87
3
3
2
(d, J = 3.2 Hz, 1H), 2.27 (dd, J = 6.6 Hz, J = 3.2 Hz, 1H),

LIU AnHua, et al. Sci China Chem July (2010) Vol.53 No.7
1581
clave. The temperature was adjusted to 373 K, and the mix-
3-Benzyl-5-methylenethiazolidine-2-thione (12a)
Yellow solid, mp: 45–46 °C. 1H NMR (400 MHz, CDCl3) 
ture was stirred for the appropriate time. After the reaction,
the reactor was cooled in ice water. An aliquot of sample
was taken from the resultant mixture for GC analysis. The
residue was purified by column chromatography on silica
gel (200–300 mesh, eluting with 20:1 to 10:1 petroleum
ether/ethyl acetate) to provide the desired products.
ppm 4.57 (t, 3J = 2.6 Hz), 5.02 (s, 2H), 5.08 (dd, 3J=5.0 Hz,
3
2
2J = 2.4 Hz, 1H), 5.13 (dd, J = 4.4 Hz, J = 2.4 Hz, 1H),
7.30–7.45 (m, 5H); 13C NMR (100 MHz, CDCl3)  ppm
51.9, 61.2, 104.9, 128.3, 128.4, 129.1, 134.6, 136.1, 194.5.
3-Ethyl-5-phenylthiazolidine-2-thione (10a)
3 Results and discussion
Yellow solid, mp: 63–65 °C. 1H NMR (400 MHz, CDCl3) 
3
ppm 1.27 (t, J = 7.2 Hz, 1H), 3.80–3.93 (m, 2H), 4.07 (dd,
Initial studies were performed with 1-ethyl-2-phenyl aziridine
1a and CO2 under solvent free conditions. The screening
reaction was carried out at 373 K for 2 h in the presence of
8 MPa CO2. The results are listed in Table 1. Without a
catalyst, the desired coupling reaction of 1a and CO2 did not
proceed at all (entry 1, Table 1). Either Lewis acid or Lewis
base gave a profitable effect on this reaction while the for-
mer was superior. However, the dimers of substrates (4a
and 5a) were largely formed as by-products in some cases
(entries 2–6). Then the insoluble ion-exchange resins con-
taining acidic carboxylic/sulfonic group or ammonium/amino
group were tested (entries 7–11). The acidic ion-exchange
resins were found to be active to some extent (entries 7 and
8), while the basic counterparts containing the ammonium
2
3
2
3J = 11.4 Hz, J = 7.2 Hz, 1H), 4.31 (dd, J = 11.4 Hz, J =
3
8.4 Hz, 1H), 4.84 (t, J = 7.6 Hz, 1H), 7.31–7.43 (m, 5H);
13C NMR (100 MHz, CDCl3)  ppm 11.6, 44.1, 47.0, 63.5,
127.3, 128.6, 129.2, 138.7, 195.4; ESI-MS calcd for
C11H13NS2 223.36, found m/z 224.38 (M +H)+, 242.75 (M+
H2O + H)+.
4-Phenyloxathiolane-2-thione (11a)
Yellow solid, mp: 80–82 °C. 1H NMR (400 MHz, CDCl3) 
3
2
3
ppm 4.04 (dd, J = 12.0 Hz, J = 5.6 Hz, 1H), 4.18, (t, J =
3
2
11.2 Hz, 1H), 5.65 (dd, J = 10.4 Hz, J = 5.6 Hz, 1H),
6.38–7.51 (m, 5H); 13C NMR (100 MHz, CDCl3)  ppm
49.7, 64.2, 127.5, 129.2, 129.3, 135.1, 183.4.
Table 1 Cycloaddition reaction of CO2 to aziridines into oxazolidinones a)
Yield (%) b)
Entry
Catalyst (mol%)
Functional group
Conv. (%) b)
2a
3a

4a+5a

1
15.3
100
99.5
100
98.2
7.9
trace
65.7
78.1
81.3
22.8
4.7


2
LiBr (5)
9.8
9.7
7.1
0.9
0.5
2.3
2.2
0.7
7.3
1.7
6.4
4.4
7.5
6.7
9.3
8.6
36.6
0.7
6.1
6.2
1.0
4.4
5.6
5.9
7.1
2.9

3
AlCl3 (5)

4
ZrOCl2 (5)
I2 (5)

5

6
DBU c) (5)
D072 d, e) (5)
D152 d, f) (5)
D201 d, g) (5)
D301R d, h) (5)
D380 d, i) (5)
D301R d, h) (1)
D301R d, h) (0.1)
D301R d, h) (10)

7
98.4
98.1
44.4
100
90.8
99.3
76.2
100
73.4
71.8
7.2
SO3H
COOH
NMe3Cl
NMe2
NH2
NMe2
NMe2
NMe2
8
9
10
11
12
13
14
84.0
54.8
73.5
44.2
85.7
a) All the reactions were carried out using 1a (0.1472 g, 1 mmol), 8 MPa, 373 K, 2 h; b) determined by GC with biphenyl as an internal standard; c) DBU:
1,8-diazabicyclo[5,4,0]-undec-7-ene; d) trade names for ion-exchange resins, bead diameter: 0.3–1.25 mm, maximum operating temperature: 120 °C. The
ion exchange resins used in this study were commercially supplied by the Chemical Plant of Nankai University, Tianjin, China; e) exchange capacity 4.2
mmol/g, true density 1.20–1.30 g/mL, strength (sized bead content after grinding) ≥90%; f) exchange capacity 9.5 mmol g1, true density 1.10–1.18 g/mL,
strength ≥85%; g) exchange capacity 3.7 mmol g1, crosslinking degree of bead 1%, true density 1.04–1.08 g/mL, strength ≥90%; h) exchange capacity
4.8 mmol g1, crosslinking degree of bead 1%, true density 1.03–1.07 g/mL, strength ≥95%; i) exchange capacity 3.5 mmolg1, crosslinking degree of bead
1%, true density 1.03–1.09 g/mL, strength ≥90%.

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LIU AnHua, et al. Sci China Chem July (2010) Vol.53 No.7
Table 2 Coupling of CO2 with 1-ethyl-2-phenylaziridine (1a) a)
salt group or primary amino group gave inferior results (en-
tries 9 and 11). To our delight, it was found that 91.3%
yield of (2a + 3a) was obtained when a basic ion-exchange
resin containing tertiary amino group D301R was used as
the catalyst (entry 10), which was demonstrated to be the
most active species in this study. Moreover, the catalytic
activity strongly depends on the functional group. The cata-
lytic activity follows this order: tertiary amine > primary
amine > quaternary ammonium > DBU (entries 6, 9–11),
which is consistent with the basicity of the functional group
except DBU. This fact presumably implies that the basic
species may be assumed to activate CO2, and thus the ba-
sicity may play a crucial role in the present catalytic system.
The functional group of D301R is a tertiary amino group,
which is assumed to activate CO2 through formation of the
zwitterionic species [42–45]. However, the primary amine
group in D380 likely tends to form the stable carbamate
salts, thus resulting in lower activity (entry 10 vs. 11). The
poor performance of DBU could presumably be due to its
coordination with CO2 and whereby retarding the ring-
closing step afterwards.
Subsequently, the influence of the catalyst amount was
evaluated under otherwise identical reaction conditions. As
shown in Table 1, the yield of 2a decreased to 73.5% as the
catalyst loading went down to 1 mol% (Table 1, entry 12).
Notably, with further decreasing the catalyst quantity to 0.1
mol%, the reaction gave unfavorable conversion with 44.2%
yield of the target products, alongside with increased
amounts of 1,4-diethyl-2,5-diphenyl-piperazine 4a and 1,4-
diethyl-2,3-diphenylpiperazine 5a (entry 13). However, in-
creasing the catalyst loading to 10 mol% showed no signifi-
cant improvement in the yield (entry 14). As a result, 2a
was formed in high chemo- and regio-selectivity by em-
ploying 5 mol% of tertiary amine functionalized ion-exchange
resin D301R as the catalyst (entry 10).
The influences of other reaction parameters were studied
as shown in Table 2. The outcome of the reaction had no
significant difference between 2 h and 1.5 h, but quickly
went down after further shortening the reaction time (entries
1–4). The reaction temperature also has distinct effect on
the coupling reaction of 1a with CO2. Entry 5 shows that
relatively low temperature has an adverse effect on the ac-
tivity. However, only slight enhancement was observed
while the temperature was elevated from 373 to 393 K (en-
tries 2 and 6). Accordingly, 373 K was suitable for the reac-
tion. The pressure has great influence on the reaction. The
total yields of 2a and 3a increased while CO2 pressure was
elevated from 0.1 to 10 MPa (entries 2, 8–11, 13–14), and
decreased at 12 MPa, presumably due to the dilution effect
of CO2 (entry 7). Apparently, 8 MPa was a reasonable
pressure for the cycloaddition to proceed. The reaction
could be carried out at a relatively low pressure without too
much loss of efficiency by prolonging the reaction time to
2.5 h (entry 12).
Conv.
(%) b)
Yield
(%) b)
Regio-sel
(%) c)
Entry P (MPa) T (K)
t (h)
1
8
100
100
100
100
80
2.0
1.5
1.0
0.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
2.5
1.5
1.5
100
99.4
98.0
86.0
53.3
100
68.7
100
99.5
99.3
100
100
100
13.6
91.3
91.5
65.6
51.1
46.2
93.7
48.5
95.5
88.4
85.6
60.2
91.1
51.0
9.1
92:8
92:8
92:8
91:9
92:8
91:9
90:10
90:10
91:9
92:8
91:9
91:9
93:7
92:8
2
8
3
8
4
8
5
8
6
8
120
100
100
100
100
100
100
100
100
7
12
10
6
8
9
10
11
12
13
14
4
2
2
1
0.1
a) All the reactions were carried out using 1a (0.1472 g, 1 mmol),
D301R (5 mol%); b) determined by GC with biphenyl as an internal stan-
dard; c) molar ratio of 2a to 3a.
the reaction was extended to the carboxylation of various
aziridines 1b–1k by employing D301R as the catalyst.
As shown in Table 3, a wide set of oxazolidinones were
selectively formed in good yields and regio-selectivities.
Substrates 1b and 1c afforded a relatively low yield of the
desired product because self-oligomers were formed (Table
3, entries 2 and 3). The substrates 1d, 1e, and 1i bearing
liner alkyl or planar benzyl groups at the nitrogen atom gave
the corresponding oxazolidinones in good to excellent yields
all with above 90% regio-selectivities (entries 4, 5 and 9).
However, 1f, 1g, and 1h with a branched or cyclic alkyl
group at the nitrogen atom showed slow reaction rate with
excellent regio-selectivity (entries 6, 7 and 8), probably due
to the steric effect. In addition, the aziridines with either
electron-donating groups or electron-withdrawing groups on
the C1-aryl ring could smoothly react with CO2 and af-
forded oxazolidinones in high yield and regio-selectivity
(entries 10 and 11). As a consequence, the activity and regio-
selectivity may greatly depend on the electron nature of the
C1-aryl group and the steric hindrance of the substituent
group at the nitrogen atom.
Another advantage of this approach is related to the het-
erogeneous catalytic process under solvent-free conditions.
The catalyst can be easily recovered from the reaction mix-
ture simply by filtration and reused for the next run after
washing with CH2Cl2 and further drying. As shown in Table
4, the catalyst can be reused at least five times without sig-
nificant loss in catalytic activity. Therefore, the recyclability
To demonstrate the utility and generality of this approach,

LIU AnHua, et al. Sci China Chem July (2010) Vol.53 No.7
Table 4 Recyclability of the catalyst a)
1583
Table 3 Substrate scope a)
Yield b) Regio-sel c)
Entry
Conv. b) (%)
>99
Yield b) (%)
92.3
Regio-sel c) (%)
Entry
Aziridine
Product
t (h)
(%)
(%)
1
2
3
4
5
91:9
91:9
>99
89.4
1
2.5
84.3
92:8
>99
89.3
90:10
90:10
90:10
1a
1b
2a
2b
>99
87.9
>99
85.8
2
3
2.5
2.5
17.3
42.5
80:20
88:12
a) Reaction conditions: 1a (1 mmol, 0.1472 g), D301R (5 mol%, 0.0104
g), 373 K, 2 MPa, 2.5 h; b) determined by GC; c) the molar ratio of 2a to 3a.
oxirane 6a and propargyl amine 8a as substrates with CO2.
As a result, the corresponding five-membered cycloaddition
products 7a and 9a were obtained in good isolated yield as
shown in Scheme 2.
1c
1d
1e
2c
4
5
2.5
2.5
85.4
89.9
92:8
92:8
2d
2e
2f
6
7
8
91.1
47.3
87.9
86.1
85.4
83.3
97:3
99:1
99:1
94:6
92:8
91:9
Scheme 2 The D310R-catalyzed carboxylation of epoxide/propargyl
amine with CO2.
1f
1g
1h
CS2 is a sulfur analogue of CO2 which can also be con-
sidered as an attractive C1 building block to synthesize sulfur-
containing functional molecules. There are only a few ex-
amples about cycloaddition of CS2 with aziridines [20, 55],
epoxides [15, 56–58] and propargyl amines [32, 59]. In this
context, we further extended this catalytic system to the
reaction involving CS2. The results are summarized in Table
5. The cycloaddition reaction proceeded smoothly to give
72
2g
2h
2i
8
18
a)
9
2.5
2.5
2.5
Table 5 Cycloaddition reaction with CS2
1i
1j
Entry
Substrate
Product
t (h)
Yield b) (%)
88.8
10
11
1
2.5
1a
6a
2j
10a
11a
2
3
24
12
31.8
92.1
1k
2k
a) Reaction conditions: substrate (1 mmol), D301R (5 mol%), 373 K, 2
MPa; b) the total isolated yield of 2 and 3; c) the molar ratio of 2 to 3.
8a
of the catalyst makes the process economically and poten-
tially viable for commercial applications.
12a
a) All the reactions were carried out with 1 mmol of the substrate with 1 mL
of CS2 by using D301R (5 mol%) as the catalyst at 373 K; b) isolated yield.
This protocol was successfully applied to the reaction of

1584
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A green catalytic process for CO2 fixation of epoxides/
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reaction conditions was developed without any organic sol-
vents. The insoluble ion-exchange resin D301R was dem-
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and a counterpart of CO2, i.e., CS2. The present process has
notable advantages and remarkable environmentally benign
features: 1) it requires no additional organic solvents; 2) the
catalyst is effective under mild conditions, and excellent
yields together with good chemo- and regio- selectivity
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