Highly efficient synthesis of cyclic carbonates from epoxides catalyzed by indium tribromide system

Article abstract of DOI:10.1016/j.tetlet.2010.12.009

A novel, efficient synthesis of cyclic carbonates from the reaction of epoxides and 1 atom of CO₂ under mild conditions (no solvent, 1 atom, room temperature) was achieved in good yields by using indium catalyst system.

Full text of DOI:10.1016/j.tetlet.2010.12.009

Tetrahedron Letters 52 (2011) 721–723
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Highly efficient synthesis of cyclic carbonates from epoxides catalyzed
by indium tribromide system
Ikuya Shibata a, , Ikuko Mitani b, Akira Imakuni c, Akio Baba c
⇑
a Research Center for Environmental Preservation, Osaka University, 2-4 Yamadaoka, Suita, Osaka 565-0871, Japan
b The Kansai Electric Power Co., Inc. 3-11-20 Nakoji, Amagasaki, Hyogo 691-0974, Japan
c Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel, efficient synthesis of cyclic carbonates from the reaction of epoxides and 1 atom of CO2 under
mild conditions (no solvent, 1 atom, room temperature) was achieved in good yields by using indium cat-
alyst system.
Received 11 November 2010
Revised 29 November 2010
Accepted 3 December 2010
Available online 8 December 2010
Ó 2010 Elsevier Ltd. All rights reserved.
In memory of Professor Haruo Matsuda
Catalytic transformation of carbon dioxide into useful organic
compounds has attracted much attention during the last two dec-
ades for the sustenance of life on earth.1 Conversion of carbon
dioxide to cyclic carbonates is one of the most important pro-
cesses.2 It is a process of high atom efficiency, and cyclic carbon-
ates are excellent aprotic polar solvents,3 electrolytes in lithium
ion batteries,4 and intermediates for producing polycarbonates
and other chemicals.5 Various catalysts have been reported for
the reaction of epoxides with carbon dioxide, including transition
metal compounds, ionic liquid or onium salts, alkali metal salts,
and so on.1b,6 While some advances have been obtained, all suffer
from either the need for co-solvent or the requirement for temper-
ature, high CO2 pressure, or expensive catalyst. Recently, active
catalysts are focused for the synthesis of cyclic carbonates from
terminal epoxides under atmospheric pressure at room tempera-
ture.7 Herein we wish to report a simple, not expensive, easily
available catalytic system and environmentally benign route to
cyclic carbonates under extremely mild reaction conditions.
Recently, indium compounds have been used in organic synthe-
sis because of their mildness and easy handling character.8 We
screened indium halides as catalysts in the reaction of epoxide
1a with 3.9 MPa of CO2. The sole use of InCl3 or InBr3 did not cat-
alyze the reaction at all (entries 1 and 2). On the other hand, the
addition of Ph3P to InBr3 dramatically increased the yield of car-
bonate 2a (entry 3). The reaction proceeded well even at room
temperature. Use of 2 equiv. of Ph3P to InBr3 afforded 2a in a quan-
titative yield (entry 4). The combination of InCl3 with Ph3P exhib-
ited no catalytic ability (entry 5). The sole use of Ph3P did not
catalyze the reaction (entry 6). Thus InBr3–Ph3P catalytic system
gave high yield at room temperature. Noteworthy is that the reac-
tion proceeded well under 1 atom of CO2 conditions (entry 7).
Reaction for 5 h gave higher yield (entry 8).
Table 2 shows the synthesis of various cyclic carbonates by
using epoxides 1b–h as starting materials with InBr3–Ph3P cata-
lytic system. Of particular interest is that in every case, the reaction
proceeded well under 1 atom of CO2 at room temperature. Epox-
ides bearing aliphatic and aromatic substituents reacted well to
give the corresponding cyclic carbonates 2b–d (entries 1–3). High
chemoselectivities were observed owning to the mild conditions.
Acid-sensitive substrate was applicable to give vinyl substituted
cyclic carbonate 2e in a good yield (entry 4). Epoxides including
halogen, oxygen substitutes gave the functionalized cyclic carbon-
ates 2f–h (entries 5–7). Unsaturated ester moiety was tolerated to
give 2h (entry 7).9
Table 1
Catalytic activity of indium tribromide-Ph3P system at rta
InX3 (cat.)
Additive (cat.)
MeO
MeO
+
CO2
O
O
no solvent, rt, 1 h
O
2a
1a
O
Entry
InX3 (5 mol %)
Additive
CO2 (MPa)
2ac (%)
1
2
3
4
5
6
7
8b
InCl3
InBr3
InBr3
InBr3
InCl3
—
—
—
3.9
3.9
3.9
3.9
3.9
3.9
0
0
74
96
0
0
72
85
Ph3P (5 mol %)
Ph3P (10 mol %)
Ph3P (10 mol%)
Ph3P (10 mol %)
Ph3P (10 mol %)
Ph3P (10 mol %)
InBr3
InBr3
0.1 (1 atom)
0.1 (1 atom)
a
b
c
1a 10 mmol.
5 h.
⇑
Corresponding author. Tel.: +81 6 6879 8975; fax: +81 6 6879 8978.
E-mail address: shibata@epc.osaka-u.ac.jp (I. Shibata).
Determined by 1H NMR.
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.12.009

722
I. Shibata et al. / Tetrahedron Letters 52 (2011) 721–723
Table 2
Me
Me
Synthesis of cyclic carbonates 2 from epoxides with CO2 at rta
Br
OInBr2
R
InBr3
PPh3
InBr (5 mol%)
3
Me
(PPh3)n
Me
A
H2O
R
PPh (10 mol%)
3
PPh3 Br
or
+
CO2
O
O
O
THF
rt, 1 h
room temp.
no solvent
OH
Isolated
O
1
3
80%
(1 atm)
PPh
3 Br
1b
O
2
O
InBr2
A'
Entry
1
R
Time
(h)
Product
2b
(%)
Scheme 1. Ring opening of epoxide by InBr3 system.
O
O
Me (1b)
Bun (1c)
5
8
2b 82
2c 90
Plausible catalytic cycles are shown in Scheme 2. Initially, InBr3
forms complex with Ph3P (left cycle). In the complex, the nucleo-
philicity of In–Br bonds is increased.11,12 After the reaction with
1, a ring-opened intermediate A or A0 is formed as an active cata-
lytic species. In the case employing A0 (right cycle), indium moiety
activates epoxide as a Lewis acid and phosphonium bromide moi-
ety causes ring opening to give B. The higher nucleophilicity of bro-
mide than chloride to 1 would result in the difference of catalytic
activity between InBr3 and InCl3 system (Table 1, entries 4 and
5). The resulting indium alkoxide of A or B adds to CO2 and the sub-
sequent intramolecular O-alkylation gives cyclic carbonates 2 with
the regeneration of A or A0.
O
O
O
2
3
O
Ph
O
O
O
Ph (1d)
10
2d 81
2e 84
O
O
4
5
6
CH@CH2 (1e)
CH2Cl (1f)
10
5
In conclusion, we provided environmentally benign and eco-
nomic process to cyclic carbonates.
O
O
Cl
O
2f
86
Acknowledgments
O
This research was supported by a Grant-in-Aid for Scientific Re-
search from the Ministry of Education, Science, Sports, and Culture,
a Japan Science and Technology Agency Potentiality Verification
Stage Project and The Naito Foundation.
BnO
O
O
CH2OBn (1g)
5
2g 89
O
O
References and notes
O
CH2O2CCMe@CH2
(1h)
7
10
2h 89
O
O
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Eckert, J.; Fujita, E.; Gibson, D. H.; Goddard, W. A.; Goodman, D. W.; Keller, J.;
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O
a
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b
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opened by InBr3–Ph3P to form A or A0 which is thought as a key
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R
InBr3 + PPh3
R
PPh3
Br
R
O
O
CO2
O
O
1
InBr2
InBr3
O
2
O
(PPh3)n
R
R
O
R
PPh3
Br
R
R
Br
PPh3
InBr2
Br
O
C
O
O
Br2In
O
O
O
InBr2
O
InBr2
O
R
A'
(PPh3)n
A
(PPh3)n
Br
R
R
B
PPh3
Br
Me
O
Br2In
Br
O
O
O
CO2
InBr2
O
O
O
C
C
(PPh3)n
R
O
O
2
O
Scheme 2. Plausible catalytic cycles.

I. Shibata et al. / Tetrahedron Letters 52 (2011) 721–723
723
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59.3, 66.0, 71.3, 75.0, 154.9; EIHRMS calcd for C5H8O4 132.0423, found
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(1.32 g. 5 mmol), and THF was added propylene oxide (1b) (5.0 mmol) under
nitrogen. The reaction mixture was stirred at room temperature for 1 h. The
resulting mixture was poured into aqueous NaHCO3 (50 mL) and extracted
with Et2O (50 mL). The organic layer was dried over MgSO4 and concentrated
in vacuo. Phosphonium salt 3 was obtained as a wax (1.60 g, 80%). 1H NMR
(CDCl3) d 1.51 (dd, J = 2.67, 5.84 Hz, 3H), 2.23 (m, 1H), 3.24 (ddd, J = 2.93, 12.70,
15.63 Hz, 1H), 3.45 (ddd, J = 10.74, 10.74, 15.63 Hz, 1H), 4.22 (m, 1H), 7.60–
8. Cintas, P. Synlett 1995, 1087–1096.
7.90 (m, 15H). 13C NMR (CDCl3)
d 25.8 (d, JC–P = 14.53 Hz), 33.1 (d, JC–
9. Representative method: To a CO2 balloon equipped 10 mL round-bottomed flask
containing indium bromide (0.178 g, 0.5 mmol) was added triphenylphosphine
(0.262 g, 1 mmol) at rt. Epoxide 1 (10 mmol) was added, and stirred at rt for
5 h. The reaction system is gas (CO2)–liquid (substrate) biphasic system. To the
reaction mixture was added 10 mL of H2O. The mixture was extracted with
Et2O (10 mL) for three times. The organic layer was dried over MgSO4. After
filtration and evaporation, the corresponding carbonate 2 was obtained in
almost pure form. Yield was determined by comparing the ratio of product to
substrate in the 1H NMR spectrum of the crude mixture. CAS Nos. 2a: 40492-
31-7, 2b: 108-32-7, 2c: 66675-43-2, 2d: 4427-92-3, 2e: 4427-96-7, 2f: 2463-
45-8, 2g: 949-97-3, 2h: 13818-44-5. For example, spectral data for 2a:
Purification was done by distillation under reduced pressure. bp 85 °C/
P = 53.46 Hz), 63.2 (d, JC–P = 6.23 Hz), 118.2 (d, JC–P = 87.19 Hz), 130.4 (d, JC–
P = 12.98 Hz), 133.6 (d, JC–P = 10.38 Hz), 135.0 (d, JC–P = 3.11 Hz); EIMS 321.1
(M+ꢀBr calcd for C21H22BrOP 400.0592). The corresponding iodide salt. Huang,
J.-W.; Shi, M. J. Org. Chem. 2003, 68, 6705–6709. Isolation of A or A0 was
unsuccessful even in the treatment in inert glove box.
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I.; Baba, A. Tetrahedron Lett. 2000, 41, 113–116; (b) Inoue, K.; Shimizu, Y.;
Shibata, I.; Baba, A. Synlett 2001, 1659–1661.
12. Optimized 1:2 ratio of InBr3/Ph3P would be according to the formation of stable
1:2 complex of InBr3/Ph3P which has been already reported: (a) Carty, A. J.;
Tuck, D. G. J. Chem. Soc. 1966, 1081–1087; (b) Chen, F.; Ma, G.; Bernard, G. M.;
Cavell, R. G.; McDonald, R.; Ferguson, M. J.; Wasylishen, R. E. J. Am. Chem. Soc.
2010, 132, 5479–5493.
;
0.07 mm Hg; IR (neat) 2900, 1789, 1172 cmꢀ1 1H NMR (CDCl3) d 3.43 (s, 3H,
OCH3), 3.54 (dd, 1H, J = 3.9 and 11.2 Hz, one of MeOCH2), 3.67 (dd, 1H, J = 3.4