Transformation of Carbon Dioxide into Oxazolidinones and Cyclic Carbonates Catalyzed by Rare-Earth-Metal Phenolates

Article abstract of DOI:10.1002/cctc.201600534

Rare-earth-metal complexes stabilized by amine-bridged tri(phenolato) ligands were developed, and their activities in catalyzing transformations of CO₂ were studied. A series of terminal epoxides and challenging disubstituted epoxides were converted into the respective cyclic carbonates in the presence of CO₂ in yields of 58 to 96 %. In addition, these rare-earth-metal complexes also showed good activities in catalyzing three-component reactions of anilines, epoxides, and CO₂, which generated 5-substituted-3-aryl-2-oxazolidines in yields of 48 to 96 %, as a useful strategy to construct oxazolidinones.

Full text of DOI:10.1002/cctc.201600534

DOI: 10.1002/cctc.201600534
Communications
Transformation of Carbon Dioxide into Oxazolidinones
and Cyclic Carbonates Catalyzed by Rare-Earth-Metal
Phenolates
Bin Xu,[a, b] Peng Wang,[a] Min Lv,[a] Dan Yuan,*[a] and Yingming Yao*[a]
Rare-earth-metal complexes stabilized by amine-bridged tri-
(phenolato) ligands were developed, and their activities in cat-
alyzing transformations of CO2 were studied. A series of termi-
nal epoxides and challenging disubstituted epoxides were con-
verted into the respective cyclic carbonates in the presence of
CO2 in yields of 58 to 96%. In addition, these rare-earth-metal
complexes also showed good activities in catalyzing three-
Scheme 1. Reactions of epoxides and CO2.
component reactions of anilines, epoxides, and CO2, which
generated 5-substituted-3-aryl-2-oxazolidines in yields of 48 to
96%, as a useful strategy to construct oxazolidinones.
Recently, we reported the synthesis of oxazolidinones from
isocyanates, which are also heterocumulenes as CO2, catalyzed
Carbon dioxide is a main greenhouse gas, and a reduction in
CO2 emission is becoming a global challenge. On the other
hand, it is an important C1 building block and can be used in
producing fine chemicals and fuels.[1] Fixation and transforma-
tion of CO2 into value-added chemicals contribute to a greener
and more sustainable chemical industry and are, thus, gaining
increasing interest.
by rare-earth-metal complexes.[7] A series of oxazolidinones
were prepared under mild conditions from epoxides and iso-
cyanates. Oxazolidinones are important heterocycles and may
potentially find applications as HIV-1 protease inhibitors, antibi-
otics, and antidepressant drugs.[8] However, this strategy re-
quires the handling of toxic isocyanates and is limited to the
availability of isocyanates that are synthesized from amines
and phosgene. Thus, a method for the preparation of oxazoli-
dinones from more easily available amines that avoids the han-
dling of highly toxic isocyanates will be greatly desirable. Gao
et al. reported a three-component synthesis of oxazolidinones
from CO2, ethylene oxide, and amines catalyzed by binary ionic
liquids (Scheme 1).[9] This method, however, requires high CO2
pressures (25 bar; 1 bar=0.1 MPa) and high temperatures
(1408C). To overcome these limitations, we herein report the
application of rare-earth-metal complexes in catalyzing the
three-component reaction. Milder reaction conditions [lower
CO2 pressure (10 bar) and temperature (958C)] and a broad
substrate scope were achieved.
The transformation of CO2 is, in general, challenging owing
to its thermodynamic stable nature. A wide range of catalysts
have thus been developed to overcome the kinetic limitations
of CO2 conversion.[2] Among them, rare-earth (RE)-metal com-
plexes are finding more applications in fields including the co-
polymerization of CO2 and epoxides[3] and the synthesis of
cyclic carbonates[4] and carboxylic acids.[5] The cycloaddition of
CO2 and epoxides is a 100% atom-economic strategy to con-
struct cyclic carbonates (Scheme 1).[6] Our group reported the
first example of a rare-earth-metal complex catalyzed reaction
of CO2 with epoxides under mild conditions, which revealed
the great potential of rare-earth-metal complexes in promoting
transformations of CO2.[4]
As a continuation of our investigation on rare-earth-metal
mediated CO2 transformations,[4,5] a series of rare-earth-metal
complexes stabilized by amine-bridged tri(phenolato) ligands
were prepared, and their activities were studied and com-
pared. Complexes 1–4 were synthesized according to our pre-
vious report (Scheme 2).[7] Given that neodymium complex 3
performed best in catalyzing the synthesis of oxazolidinones
from epoxides and isocyanates,[7] analogous complexes 5 and
6 bearing tri(phenolato) ligands with different substituents
were synthesized by a similar strategy in yields of 70 and 56%,
respectively. The solid-state structure of complex 5 (depicted
in Figure S1 in the Supporting Information) was unambiguous-
ly confirmed by X-ray diffraction analysis of single crystals ob-
tained from a hexane/THF solution. The neodymium center in
complex 5 is coordinated by the phenolato L2 ligand and three
THF molecules, adopting an orthorhombic geometry.
[a] B. Xu, P. Wang, M. Lv, Dr. D. Yuan, Prof. Y. Yao
Key Laboratory of Organic Synthesis of Jiangsu Province
College of Chemistry
Chemical Engineering and Materials Science
Dushu Lake Campus
Soochow University
Suzhou 215123 (P.R. China)
Fax: (+86)512-65880305
E-mail: yuandan@suda.edu.cn
yaoym@suda.edu.cn
[b] B. Xu
Lhasa Normal College
Lhasa 850007 (P.R. China)
Supporting Information for this article can be found under http://
dx.doi.org/10.1002/cctc.201600534.
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the yield (Table 1, entries 6 and 7). Different co-catalysts were
tested, and the combination of complex 3 with NBu4Br proved
to be most effective (Table 1, entries 3, 8–10). Consistent with
previous reports, halides of good nucleophilic and leaving abil-
ities were crucial in opening of the epoxide ring and subse-
quent cycloaddition.[10] In comparison, complex 3 or NBu4Br
alone did not lead to good results (Table 1, entries 11 and 12).
On the basis of this finding, the ratio of complex 3/NBu4Br was
examined and 1:6 proved to be optimal (Table 1, entries 3, 13–
14).
Scheme 2. Synthesis of complexes 1–6. Cp=h5-cyclopentadienyl.
Prior to studying the three-component reaction, the activi-
ties of complexes 1–6 in catalyzing the two-component reac-
tion between CO2 and propylene oxide (PO) were assessed,
and the results are summarized in Table 1. A preliminary study
with complexes 1–4 (0.1 mol%) in the presence of NBu4I
(0.5 mol%) as a co-catalyst under CO2 (10 bar) pressure at
1008C generated propylene carbonate in yields of 64 to 82%,
and complexes 3 and 4 bearing metal ions of larger ionic radii
were the most active (Table 1, entries 1–4). Complex 3 was em-
ployed for further condition screening. The reaction was con-
ducted at a lower CO2 pressure of 6 bar, which, however, led
to a significantly lower yield of 69% (Table 1, entry 5). On the
other hand, raising the pressure was not helpful in improving
Table 2. Scope of the reaction of epoxides with CO2.[a]
Entry
1
Substrate
Product
Yield[b,c] [%]
95
2
83[d] (46[e]
)
3
4
5
77[d]
93
96
6
7
94 (41[e]
)
Table 1. Screening of conditions for the reaction of propylene oxide (PO)
with CO2.[a]
72
8
58[d]
75[d]
88[f]
Entry
Catalyst
Co-catalyst
PCO [bar]
T [8C]
Yield[b,c] [%]
2
1
2
3
4
5
6
7
8
1
2
3
4
3
3
3
3
3
3
–
3
3
3
5
5
5
5
6
5
NBu4I
NBu4I
NBu4I
NBu4I
NBu4I
NBu4I
NBu4I
NBu4Br
NOct4Br
PPNCl
NBu4Br
–
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
10
10
10
10
6
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
85
74
76
82
80
69
81
83
90
85
77
13
trace
54
93
98
96
93
88
9
10
20
30
10
10
10
10
10
10
10
10
10
10
10
10
10
11
72[g,h]
9
10
11
12
13
14
89[g]
83[i]
12
13[d]
14[e]
15[e]
16[e]
17[f]
18[g]
19[g]
20[f,h]
86[g]
85
85
85
85
15
91[g]
55
80
[a] Reaction conditions: complex 5 (0.067 mol%), NBu4Br (0.4 mol%),
neat, 24 h, CO2 (1 bar), 858C. [b] Yield of isolated product. [c] Selectivity
for the cyclic carbonate product was >99%. [d] Complex 5 (0.1 mol%),
NBu4Br (0.6 mol%). [e] In the absence of 5. [f] Complex 5 (0.1 mol%),
NBu4Br (0.6 mol%), 36 h. [g] CO2 (10 bar), complex 5 (0.067 mol%), NBu4Br
(0.4 mol%). [h] 6:1 dr. [i] CO2 (10 bar), complex 5 (0.1 mol%), NBu4Br
(0.6 mol%).
[a] Reaction conditions: catalyst (0.1 mol%), co-catalyst (0.5 mol%), neat,
1 h. Oct=n-octyl. [b] Determined by 1H NMR spectroscopy. [c] Selectivity
for the cyclic carbonate product was >99%. [d] Catalyst (0.1 mol%),
NBu4Br (0.1 mol%). [e] Catalyst (0.1 mol%), NBu4Br (0.6 mol%). [f] Catalyst
(0.067 mol%), NBu4Br (0.4 mol%). [g] Catalyst (0.05 mol%), NBu4Br
(0.3 mol%). [h] 0.5 h.
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To study the influence of ancillary ligands, complex 5 was
tested, and a near-quantitative yield of 98% was obtained
(Table 1, entry 15). The presence of electron-withdrawing
chloro substituents in ligand L2 makes the neodymium center
in 5 more Lewis acidic, which may result in enhanced activity.
Lowering the temperature to 858C gave a similar yield
(Table 1, entry 16). Evaluation of the catalyst loading revealed
that >90% yield was still obtained at a low catalyst loading of
0.067 mol% (Table 1, entries 16–18). For comparison, under
identical conditions, the reaction catalyzed by complex 6 led
to a significantly lower yield of 55% (Table 1, entry 19). An at-
tempt to conduct the reaction for a shorter time of 0.5 h re-
sulted in a decreased yield of 80% (Table 1, entry 20).
and functional-group tolerance for a broad range of substrates.
Similar performances were observed for rare-earth-metal com-
plexes stabilized by ethylenediamine-bridged tetra(phenolato)
ligands.[4] For substrate 7l comprised of 86% trans and 14%
cis isomers, respective cyclic carbonate 8l comprising 89%
trans and 11% cis configurations was obtained, which suggest-
ed that the configurations are retained during the transforma-
tion.[10a,12] Carbonates 8m–o derived from internal cis-epoxides
7m–o were determined to be cis configured after comparison
with literature data.[12,13] Two background reactions involving
the use of 7c and 7g were conducted in the absence of com-
plex 5, and the yields dropped by 37% (Table 2, entry 2) and
53% (Table 2, entry 6), respectively, which is indicative of the
imperative role of rare-earth-metal complexes in this reaction.
Inspired by the good performance of rare-earth-metal tri(-
phenolate) complexes in catalyzing the cycloadditions of epox-
ides and CO2, we examined their activities in catalyzing three-
component reactions involving PO, aniline, and CO2 (Table 3).
An initial study with complex 3 in the presence of NBu4Br as
co-catalyst formed desired product 10a, 5-methyl-3-phenyl-2-
oxazolidinone, in a trace amount after a reaction time of 18 h,
and a large amount of propylene carbonate was formed as
To explore the scope of the epoxides, a series of terminal
and disubstituted epoxides were tested, and the results are
summarized in Table 2. Notably, under 1 bar of CO2, terminal
epoxides bearing chloro, aryl, alkyl, ether, ester, hydroxy, and
morpholinyl substituents were converted expediently into the
respective cyclic carbonates in yields ranging from 58 to 96%
yields (Table 2, entries 1–9). 1,2,7,8-Diepoxyoctane reacted with
CO2 (2 equiv.) and generated the corresponding dicarbonate in
88% yield (Table 2, entry 10). Reactions of more challenging
disubstituted epoxides[6c,10a,11] required a higher pressure of
10 bar, and the respective cyclic carbonates were isolated in
good yields of 72 to 91% (Table 2, entries 11–15). It is thus con-
clusive that rare-earth-metal phenolates show good activities
a
byproduct (Table 3, entry 1). Given that 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU) works as a CO2 activator by form-
ing zwitterionic adducts,[14] the addition of DBU was tested,
which resulted in an dramatic increase in the yield to 72%
Table 3. Screening of the conditions for the reaction of propylene oxide (PO), aniline, and CO2.[a]
Entry
Catalyst
Co-catalyst
PO/PhNH2/Catalyst/Co-catalyst
Additive
Additive/PhNH2
t [h]
Yield[b] [%]
1
2
3
4
5
6
7
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
1
2
4
5
5
5
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4I
1000:100:1:1
1000:100:1:1
1500:100:1:1
2000:100:1:1
2000:100:1:1
2000:100:1:1
2000:100:1:1
2000:100:1:1
3000:150:1:1
3000:150:1:1
3000:150:1:1
3000:150:1:1
3000:150:1:1
3000:150:1:1
3000:150:1:1
2400:400:1:1
2400:400:1:1
2400:400:1:1
2400:400:1:1
2400:400:1:1
2400:400:1:1
2400:400:1:1
2400:400:1:1
4000:400:1:1
6000:400:1:1
–
–
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
7:10
5:10
1:10
7:10
7:10
7:10
7:10
7:10
7:10
7:10
7:10
7:10
7:10
18
18
18
18
12
9
6
9
9
9
9
9
9
9
9
9
9
9
trace
72
89
94
96
92
52
43
74
6
DBU
DBU
DBU
DBU
DBU
DBU
DBU
DBU
TMEDA
Et3N
DABCO
DBU
DBU
DBU
DBU
DBU
DBU
DBU
DBU
DBU
DBU
DBU
DBU
DBU
8[c]
9
10
11
12
13
14
15
16
17[d]
18
19
20
21
22
23
24
25
45
8
99
85
66
67
58
55
49
55
60
58
73
84
95
PPNCl
9
9
9
9
9
9
9
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
NBu4Br
[a] Reaction conditions: 958C, CO2 (10 bar). TMEDA=N,N,N’,N’-tetramethyl-1,2-ethylenediamine, DABCO=1,4-diazabicyclo[2.2.2]octane. [b] Determined by
GC. [c] 808C. [d] CO2 (6 bar).
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(Table 3, entry 2). To gain better yields of the oxazolidinones,
a large excess amount of PO was essential. Increasing the ratio
of PO to aniline led to a significant increase in the yield (89
and 94%; Table 3, entries 3 and 4). Optimization of the reaction
time suggested 9 h to be sufficient (Table 3, entries 4–7). A rel-
atively high temperature of 958C was crucial, as only a moder-
ate yield of 43% was obtained at 808C (Table 3, entry 8). In an
attempt to reduce the catalyst loading, a good yield of 74%
was achieved with a PO/PhNH2/catalyst ratio of 3000:150:1
(Table 3, entry 9). Different additives were screened, and DBU
remained the optimal choice (Table 3, entries 9–12). Adjust-
ment of the ratio of DBU to aniline suggested that 7:10 was
the most effective (Table 3, entries 9, 13–15), as evidenced by
the near-quantitative yield (Table 3, entry 13). A further in-
crease in the substrate/catalyst ratio to 400:1 resulted in a re-
duced yield of 67% (Table 3, entry 16), and the reaction pro-
ceeded moderately at a lower CO2 pressure of 6 bar (Table 3,
entry 17). Different co-catalysts were screened, and NBu4Br
proved to be the best performer (Table 3, entries 16, 18, and
19).
Table 4. Scope of the reaction of propylene oxide (PO), aniline, and
CO2.[a]
Entry
1
Amine
Product
Yield[b] [%]
86
2
56
3
4
5
76
85
91
Under identical conditions, the performances of com-
plexes 1–5 were studied and compared, and the reaction cata-
lyzed by complex 5 bearing a more Lewis acidic metal center
gave the best yield (Table 3, entries 16, 20–23), which is consis-
tent with the observation of the rare-earth-metal catalyzed cy-
cloaddition of epoxides and CO2 (see above). Increasing the
amount of PO led to an improved yield of 95% (Table 3, en-
tries 23–25).
6
7
8
86
92
72
On the basis of the optimization results, the scopes of the
epoxides and amines were studied to construct oxazolidinones
with different substituents (Tables 4 and 5). A series of anilines
bearing either electron-donating or electron-withdrawing sub-
stituents in the para positions were conveniently converted
into the corresponding oxazolidinones in yields of 76 to 92%
(Tables 4, entries 1–7), with the exception of p-anisidine
(Tables 4, entry 2), possibly because of deactivation of the cata-
lyst with coordinating oxygen atoms. Reactions of anilines with
meta substituents, including nitro, chloro, and methyl groups,
also proceeded, and led to the desired oxazolidinones in yields
of 72, 76, and 48%, respectively (Tables 4, entries 8–10). How-
ever, no product was isolated with substrates bearing ortho
substituents, regardless of the electron-donating or electron-
withdrawing nature (Tables 4, entries 11 and 12). Comparing
the three-component reaction with the two-component reac-
tion of epoxides and isocyanates, comparable yields were gen-
erally obtained.[7] However, the latter is restricted to aryl isocya-
nates bearing para substituents owing to the availability of
substituted aryl isocyanates. Thus, the three-component reac-
tion not only employs easily available substrates but also pro-
vides a synthetic route to a broader range of oxazolidinones.
Reactions of different epoxides were also studied, and mod-
erate yields were obtained from monosubstituted epoxides
bearing alkyl, ether, alkenyl, or phenyl groups (Table 5, en-
tries 1–6). 5-Phenyl aryloxazolidinone 10r formed exclusively as
the only product, showing the high regioselectivity of this
strategy. In comparison, a mixture of 5- and 4-phenyl aryloxa-
zolidinones was formed in a ratio of 2.1:1 from the two-com-
9
76
48
10
11
12
trace
trace
[a] Reaction conditions: propylene oxide (PO) (5.75 mL, 82.2 mmol), ani-
line (5.48 mmol), 958C, CO2 (10 bar), complex 5 (12.3 mg, 0.0137 mmol),
NBu4Br (4.4 mg, 0.0137 mmol), 9 h, DBU (0.57 mL, 3.84 mmol). [b] Yield of
isolated product.
ponent reaction of styrene oxide with phenyl isocyanate.[7] Re-
action of the disubstituted epoxide 1,2-epoxy-2-methylpro-
pane proceeded sluggishly and generated the desired oxazoli-
dinone in <10% yield, which is significantly lower than that
obtained through the two-component reaction.[7] These two
methods are thus complementary to each other and provide
access to a diverse set of oxazolidinones.
A preliminary study to investigate the reaction mechanism
was conducted by treating propylene carbonate (15-fold
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Communications
oxazolidines with yields in the 48–96% range. These results
prove the great application of rare-earth-metal complexes in
mediating CO2 transformations, adding value to the utilization
of CO2. One main drawback of the three-component approach
is the necessity for a large excess amount of the epoxides with
respect to the amine (15-fold excess in this study), which re-
quires further optimization to improve atom efficiency. More
investigations on rare-earth-metal mediated CO2 transforma-
tions are in progress in our laboratory.
Table 5. Scope of the reaction of epoxides, aniline, and CO2.[a]
Entry
Epoxide
Product
Yield[b] [%]
1
57
2
62
Experimental Section
3
4
45
54
General procedure for the three-component reaction: The reac-
tion was performed in a 300 mL stainless-steel Parr reactor with
a stirring bar inside and a needle valve for injection. In a typical re-
action, complex 5 (12.3 mg, 0.0137 mmol), NBu4Br (4.4 mg,
0.0137 mmol), epoxide (82.2 mmol), aniline (5.48 mmol), and DBU
(3.84 mmol) were introduced into the predried reactor. The reactor
was pressurized to 10 bar with CO2 and heated at 958C for 9 h.
Upon completion of the reaction, the mixture was cooled to room
temperature, and the pure product was isolated by column chro-
matography (EtOAc/petroleum ether 1:30). The structure was con-
firmed by comparison with literature data.[7,9]
5
6
7
46
68
Acknowledgements
<10
Financial support from the National Natural Science Foundation
of China (Grants 21132002, 21372172, and 21402135), the Natu-
ral Science Foundation of the Jiangsu Higher Education Institu-
tions of China (14KJA150007, 14KJB150021), and Priority Aca-
demic Program Development of Jiangsu Higher Education Institu-
tions PAPDare gratefully acknowledged.
[a] Reaction conditions: epoxide (82.2 mmol), aniline (0.5 mL, 5.48 mmol),
958C, CO2 (10 bar), complex 5 (12.3 mg, 0.0137 mmol), NBu4Br (4.4 mg,
0.0137 mmol), 9 h, DBU (0.57 mL, 3.84 mmol). [b] Yield of isolated prod-
uct.
excess) with aniline under catalytic conditions (Scheme 3), and
5-methyl-3-phenyl-2-oxazolidinone was detected in 34% yield
(by GC) along with unreacted propylene carbonate. This find-
ing implies that the formation of the cyclic carbonate followed
by reaction with aniline might be one of the pathways leading
to oxazolidinone formation.
Keywords: carbon dioxide fixation
oxazolidinones · rare earths · multicomponent reactions
· cyclic carbonates ·
[1] a) M. Peters, B. Kçhler, W. Kuckshinrichs, W. Leitner, P. Markewitz, T. E.
Mꢁller, ChemSusChem 2011, 4, 1216; b) M. Cokoja, C. Bruckmeier, B.
Rieger, W. A. Herrmann, F. E. Kꢁhn, Angew. Chem. Int. Ed. 2011, 50, 8510;
Angew. Chem. 2011, 123, 8662; c) Z.-Z. Yang, L.-N. He, J. Gao, A.-H. Liu,
B. Yu, Energy Environ. Sci. 2012, 5, 6602; d) X.-B. Lu, W.-M. Ren, G.-P. Wu,
Acc. Chem. Res. 2012, 45, 1721; e) I. Omae, Coord. Chem. Rev. 2012, 256,
1384; f) M. Aresta, A. Dibenedetto, A. Angelini, Chem. Rev. 2014, 114,
1709; g) C. Maeda, Y. Miyazaki, T. Ema, Catal. Sci. Technol. 2014, 4, 1482;
h) Q. Liu, L. Wu, R. Jackstell, M. Beller, Nat. Commun. 2015, 6, 5933; i) M.
Luo, Y. Li, Y.-Y. Zhang, X.-H. Zhang, Polymer 2016, 82, 406; j) J. A. Rodri-
guez, P. Liu, D. J. Stacchiola, S. D. Senanayake, M. G. White, J. G. Chen,
ACS Catal. 2015, 5, 6696.
[2] M. Drees, M. Cokoja, F. E. Kꢁhn, ChemCatChem 2012, 4, 1703.
[3] a) X. Chen, Z. Shen, Y. Zhang, Macromolecules 1991, 24, 5305; b) C.-S.
Tan, T.-J. Hsu, Macromolecules 1997, 30, 3147; c) B. Liu, X. Zhao, X.
Wang, F. Wang, J. Polym. Sci. Part A 2001, 39, 2751; d) T.-J. Hsu, C.-S. Tan,
Polymer 2001, 42, 5143; e) J.-T. Guo, X.-Y. Wang, Y.-S. Xu, J.-W. Sun, J.
Appl. Polym. Sci. 2003, 87, 2356; f) Z. Quan, X. Wang, X. Zhao, F. Wang,
Polymer 2003, 44, 5605; g) D. Xie, X. Wang, X. Zhang, F. Wang, Chin. J.
Polym. Sci. 2005, 23, 671; h) H. Lu, Y. Qin, X. Wang, X. Yang, S. Zhang, F.
Wang, J. Polym. Sci. Part A 2011, 49, 3797; i) Y. Dong, X. Wang, X. Zhao,
F. Wang, J. Polym. Sci. Part A 2012, 50, 362; j) D. Cui, M. Nishiura, Z. Hou,
Macromolecules 2005, 38, 4089; k) B. B. Lazarov, F. Hampel, K. C.
Hultzsch, Z. Anorg. Allg. Chem. 2007, 633, 2367; l) D. Cui, M. Nishiura, O.
Tardif, Z. Hou, Organometallics 2008, 27, 2428; m) Z. Zhang, D. Cui, X.
Liu, J. Polym. Sci. Part A 2008, 46, 6810; n) A. Decortes, R. M. Haak, C.
In summary, rare-earth-metal complexes stabilized by amine-
bridged tri(phenolato) ligands were developed to catalyze
transformations of CO2. A series of terminal epoxides were
treated with CO2 under atmospheric pressure to generate
cyclic carbonates in yields of 58 to 96%. More challenging dis-
ubstituted epoxides were also converted into cyclic carbonates
in yields of 72 to 91% at a relatively higher pressure of 10 bar.
In addition, rare-earth-metal complexes showed good activities
in catalyzing three-component reactions of epoxides, amines,
and CO2 (10 bar) to generate a series of 5-substituted-3-aryl-2-
Scheme 3. Reaction of propylene carbonate with aniline.
ChemCatChem 2016, 8, 1 – 7
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These are not the final page numbers! ÞÞ

Communications
Martꢂn, M. M. Belmonte, E. Martin, J. Benet-Buchholz, A. W. Kleij, Macro-
molecules 2015, 48, 8197.
[4] J. Qin, P. Wang, Q. Li, Y. Zhang, D. Yuan, Y. Yao, Chem. Commun. 2014,
50, 10952.
[11] a) A. Decortes, M. M. Belmonte, J. Benet-Buchholz, A. W. Kleij, Chem.
Commun. 2010, 46, 4580; b) A. Coletti, C. J. Whiteoak, V. Conte, A. W.
Kleij, ChemCatChem 2012, 4, 1190; c) W. Clegg, R. Harrington, M. North,
R. Pasquale, Chem. Eur. J. 2010, 16, 6828; d) C. J. Whiteoak, N. Kielland,
V. Laserna, E. C. Escudero-Adꢃn, E. Martin, A. W. Kleij, J. Am. Chem. Soc.
2013, 135, 1228.
[5] H. Cheng, B. Zhao, Y. Yao, C. Lu, Green Chem. 2015, 17, 1675.
[6] a) T. Sakakura, K. Kohno, Chem. Commun. 2009, 1312; b) M. North, R.
Pasquale, C. Young, Green Chem. 2010, 12, 1514; c) A. Decortes, A. M.
Castilla, A. W. Kleij, Angew. Chem. Int. Ed. 2010, 49, 9822; Angew. Chem.
2010, 122, 10016; d) P. P. Pescarmona, M. Taherimehr, Catal. Sci. Technol.
2012, 2, 2169; e) X.-B. Lu, D. J. Darensbourg, Chem. Soc. Rev. 2012, 41,
1462; f) M. Cokoja, M. E. Wilhelm, M. H. Anthofer, W. A. Herrmann, F. E.
Kꢁhn, ChemSusChem 2015, 8, 2436; g) C. Martꢂn, G. Fiorani, A. W. Kleij,
ACS Catal. 2015, 5, 1353.
[7] P. Wang, J. Qin, D. Yuan, Y. Wang, Y. Yao, ChemCatChem 2015, 7, 1145.
[8] a) A. Ali, G. S. K. K. Reddy, H. Cao, S. G. Anjum, M. N. L. Nalam, C. A.
Schiffer, T. M. Rana, J. Med. Chem. 2006, 49, 7342; b) S. Cacchi, G. Fabrizi,
A. Goggiamani, G. Zappia, Org. Lett. 2001, 3, 2539; c) B. Mallesham,
B. M. Rajesh, P. R. Reddy, D. Srinivas, S. Trehan, Org. Lett. 2003, 5, 963.
[9] B. Wang, E. H. M. Elageed, D. Zhang, S. Yang, S. Wu, G. Zhang, G. Gao,
ChemCatChem 2014, 6, 278.
[12] C. Beattie, M. North, P. Villuendas, C. Young, J. Org. Chem. 2013, 78, 419.
´
[13] K. M. Tomczyk, P. A. Gunka, P. G. Parzuchowski, J. Zachara, G. Rokicki,
Green Chem. 2012, 14, 1749.
[14] a) X. Liu, S. Zhang, Q. W. Song, X. F. Liu, R. Ma, L. N. He, Green Chem.
2016, 18, 2871; b) E. R. Pꢄrez, M. O. da Silva, V. C. Costa, U. P. Rodrigues-
Filho, D. W. Franco, Tetrahedron Lett. 2002, 43, 4091; c) M. Yoshida, T.
Mizuguchi, K. Shishido, Chem. Eur. J. 2012, 18, 15578; d) D. J. Helde-
brant, P. G. Jessop, C. A. Thomas, C. A. Ecket, C. L. Liotta, J. Org. Chem.
2005, 70, 5335; e) E. R. Pꢄrez, R. H. A. Santos, M. T. P. Gambardella,
L. G. M. de Macedo, U. P. Rodrigues-Filho, J. C. Launay, D. W. Franco, J.
Org. Chem. 2004, 69, 8005; f) J. Sun, W. Cheng, Z. Yang, J. Wang, T. Xu,
J. Xin, S. Zhang, Green Chem. 2014, 16, 3071; g) C. Villiers, J. P. Dognon,
R. Pollet, P. Thuꢄry, M. Ephritikhine, Angew. Chem. Int. Ed. 2010, 49,
3465; Angew. Chem. 2010, 122, 3543.
[10] a) C. J. Whiteoak, E. Martin, M. M. Belmonte, J. Benet-Buchholz, A. W.
Kleij, Adv. Synth. Catal. 2012, 354, 469; b) J. A. Castro-Osma, C. Alonso-
Moreno, A. Lara-Sꢃnchez, J. Martꢂnez, M. North, A. Otero, Catal. Sci. Tech-
nol. 2014, 4, 1674.
Received: May 3, 2016
Published online on && &&, 0000
&
ChemCatChem 2016, 8, 1 – 7
www.chemcatchem.org
6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

COMMUNICATIONS
A rare find: Rare-earth-metal complexes
stabilized by amine-bridged tri(phenola-
to) ligands are active in catalyzing trans-
formations of CO2. A series of terminal
and disubstituted epoxides are convert-
ed into cyclic carbonates in yields of 58
to 96%. In addition, these rare-earth-
metal complexes show good activities
in catalyzing the three-component reac-
tion of anilines, epoxides, and CO2,
which provides a useful strategy to pre-
pare oxazolidinones.
B. Xu, P. Wang, M. Lv, D. Yuan,* Y. Yao*
&& – &&
Transformation of Carbon Dioxide into
Oxazolidinones and Cyclic Carbonates
Catalyzed by Rare-Earth-Metal
Phenolates
ChemCatChem 2016, 8, 1 – 7
www.chemcatchem.org
7
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ