Well-Defined Cesium Benzotriazolide as an Active Catalyst for Generating Disubstituted Ureas from Carbon Dioxide and Amines

Article abstract of DOI:10.1002/cctc.201601320

The reaction of alkali metal carbonates with various azole compounds produced a new series of alkali metal azolides, and they were applied as active catalysts for the production of disubstituted ureas from the carboxylation of various amines with CO₂. Among them, cesium benzotriazolide (Cs[BTd]) was found to be the most active for the carboxylation reaction and was structurally characterized by single-crystal X-ray diffraction. The crystal structure of highly hygroscopic Cs[BTd] was found to be [BTA]???Cs[BTd], which explains why it is a water-tolerant active species for this carboxylation reaction, leading to a maximum turnover frequency of 344 h^?1 as well as high recyclability even after five successive runs.

Full text of DOI:10.1002/cctc.201601320

Accepted Article
Title: Well-Defined Cesium Benzotriazolide as Active Catalyst for
Generating Disubstituted Ureas from Carbon Dioxide and Amines
Authors: Cong Chien Truong, Jin Kim, Yunho Lee, and Yong Jin Kim
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.201601320
Link to VoR: http://dx.doi.org/10.1002/cctc.201601320
A Journal of
www.chemcatchem.org

10.1002/cctc.201601320
ChemCatChem
COMMUNICATION
Well-Defined Cesium Benzotriazolide as Active Catalyst for
Generating Disubstituted Ureas from Carbon Dioxide and Amines
Cong Chien Truong,[b] Jin Kim,[c] Yunho Lee,[c] and Yong Jin Kim*[a]
Recently, an ionic liquid (IL) system including [Bmim]Cl/CsOH[14]
has received particular attention since this exhibited higher
activity than any other catalyst systems reported although the use
Abstract: The reaction of alkali metal carbonates with various azole
compounds produced a new series of alkali metal azolides and they
of excess amounts of expensive IL as solvent and CsOH (molar
were applied as active catalysts for producing disubstituted ureas
ratio of amine/base = 60, TOF = 15 h-1) remains as minor regret.
from the carboxylation of CO2 with various amines. Among them,
The synthesis of disubstituted urea from CO2 and amine can
cesium benzotriazolide (Cs[BTd]) was found to be most active for the
carboxylation and was structurally characterized by a single-crystal X-
ray diffraction. The crystal structure of highly hygroscopic Cs[BTd]
was found to be [BTA]···Cs[BTd], which explains water-tolerant active
species for this carboxylation reaction, leading to maximum TOF of
344 h-1 as well as high recyclability even after five successive runs.
be done by carboxylation reaction to produce carbamate salt
+
(RNH3 RNHCOO-), followed by in situ dehydration known as rate-
determining step. Eventually, a breakthrough of this reaction can
be achieved by a process of dehydrative carboxylation.
The cesium ion is known as most basic among the alkali
metals. The use of this basic cation as a part of catalyst for the
carboxylation reaction has some advantages since the intrinsic
nature of carbon dioxide is weak acid, which renders it easy to
activate. It would be beneficial for this carboxylation reaction when
the counteranion of the cesium is also basic. This is why the
Cs2CO3 showed high activity as a catalyst for generating DSUs.[15]
However, there has been no report on the systematic approach to
explain the high activity.
In this context, we used organic anions such as imidazolide,
triazolide, and benzotriazolide as counter parts of cesium cation
to elucidate key factors influencing the catalytic activity based on
X-ray crystal structure and in situ NMR study. The synthesized
cesium azolides, especially cesium benzotriazolide showed
surprisingly high activity for carboxylation of amines with CO2 to
produce corresponding DSUs with almost quantitative yield in the
absence of additional dehydrating agent.
Chemical fixation of CO2 into organic molecules has been
received increasing attention during a couple of decades.[1]
Taking into account the increased concerns on the global
warming, the catalytic transformation of CO2 into useful organic
compounds can be one option among the various efforts to
mitigate the CO2 concentration.[2] Even though the consumption
of CO2 through this protocol is unlikely to impact significantly, the
utilization of CO2 as carbonyl reagent by catalysis is of large
importance from
a standpoint of green and sustainable
chemistry.[3] While some advances have been made, the inert
nature of CO2 hampers a wide spectrum of efficient catalytic
processes, which remains a significant challenge. One of the
promising endeavors in this area is the direct carboxylation of
amines with CO2 to produce disubstituted urea (DSU), which is
widely used as intermediates of fine chemicals and biologically
active compounds.[4] Meanwhile, the DSU has been produced by
phosgenation of amines to isocyanates, followed by the reaction
with corresponding amines,[5] or by the carbonylation of amines.[6]
We now report the synthesis and reactivity of a series of active
catalysts, M[Azd] (M = alkali metal, Azd = imidazolide, triazolide,
benzotriazolide), which are used as catalyst for producing dihexyl
urea (DHU when R is C6) as described in Eq. (1).
However, both have several drawbacks of using highly toxic
8]
reagent[7] or extremely expensive catalyst,[4d,
respectively.
Although CO2 easily reacts with amines to afford the
corresponding carbamate salt at room temperature and
atmospheric pressure,[9] further transformation into diurea
generally needs harsh reaction conditions such as higher
temperature than 200 oC [10] and more than 12 h reaction time,[11]
and in some cases, stoichiometric amounts of base is required.[12]
Because this reaction is controlled by thermodynamic equilibrium,
excess amounts of dehydrating agent should be added.[12-13]
The reflux of 2 equiv of benzotriazole (BTA) with 1 equiv of
cesium carbonate in methanol for 12 h, followed by evaporation
and recrystallization in methanol/ether to give a white crystalline
solid, Cs[benzotriazolide] (Cs[BTd]) (1) as shown in Eq. (2), which
was characterized with 1H and 13C NMR spectroscopy and
elemental analysis (see Supporting Information). When we have
a close look at the 13C NMR spectrum of 1, there is no peak
responsible for carbonates at around 159 ppm, indicating that the
compound 1 is synthesized with high purity and there is no
remaining salts of carbonates.
[a]
Prof. Dr. Y. J. Kim
Green Material and Process R&D Group
Korea Institute of Industrial Technology (KITECH)
89 Yangdaegiro-gil, Ipjang-myeon, Cheonan 31056, Korea
E-mail: yjkim@kitech.re.kr
[b]
[c]
C. C. Truong
Department of Green Process and System Engineering
Korea University of Science and Technology (UST)
89 Yangdaegiro-gil, Ipjang-myeon, Cheonan 31056, Korea
J. Kim, Prof. Y. Lee
Department of Chemistry
Korea Advanced Institute of Science and Technology (KAIST)
291, Daehak-ro, Yuseong-gu, Daejeon 34141, Korea
The catalytic activities of various alkali metal benzotriazolides
were evaluated as catalysts for the carboxylation of n-hexylamine
(HA) as a model substrate, and were compared with Cs-
containing other azolides such as imidazolide and 1,2,4-triazolide.
The results in Table 1 show that the activity of cesium
benzotriazolide (1) is significantly higher (DHU yield: 95.1%) than
other alkali metal benzotriazolides and the tendency of alkali
metal on the activity in this reaction is found in the order Li+< Na+<
K+< Rb+< Cs+, suggesting that the size of cation plays an
important role in promoting the carboxylation reaction, probably
by rendering more basic condition as the size of cation becomes
larger (entries 1-5). In contrast, when changing benzotriazolide
with a different anion such as 1,2,4-triazolide (2) or imidazolide
Supporting information for this article is given via a link at the end of
the document. It contains IR and NMR spectroscopic data, TGA
data, and single-crystal X-ray diffraction data. CCDC-1510248
contain(s) the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data
request/cif.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601320
ChemCatChem
COMMUNICATION
(3) using cesium as same cation, the activities decrease with the
increase in the basicity of anion1 (entries 5-7).[16] Thus the basicity
of anion and catalytic activity is not likely to have a strong
relationship in the carboxylation reactions when using Cs-
azolides as catalyst in spite of strong dependency on the basicity
of these anions for CO2 capture, implying that some kinds of
different factors are governing for resulting in high activity of 1.[17]
It is worth noting that when replacing the protons at 4 and 5
position (R1 and R2) on the benzo ring of 1 with electron
withdrawing groups such as -NO2 and -Cl, a significant decrease
in activity was observed to give only 38.6% of DHU yield (entry 2,
Table 3). On the other hand, replacing them with electron
donating group like -CH3 improved the original activity even more
slightly, leading to 96.1% yields of DHU. These results strongly
suggest that the electronic effect of the substituents largely
influences the basicity of benzotriazolide species, i.e., the
stronger the electron donating ability, the higher the basicity of
benzotriazolide, and thus the higher the activity of catalyst in the
carboxylation reaction.
The combination of benzotriazole and Cs2CO3 resulted in lower
yield of DHU (82.9%) than 1, suggesting that an induction period
is needed for the formation of 1 during the carboxylation and this
is quite reasonable because the existence of CO2 pressure might
retard the rate of the formation of 1 due to Le Chatelier’s principle
during the carboxylation reaction. As the NMP itself has some
ability to afford this reaction,[18] the carboxylation without catalyst
produced 20.2% of DHU yield (entry 9). Moreover, the compound
1 was also found to be active for the carboxylation of various
substrates including benzylamine, n-propylamine, n-butylamine,
and n-heptylamine. However, aniline with a low basicity (pKa =
4.25) was inactive toward the carboxylation reaction and sec-
butylamine gave comparatively low yield, possibly due to the
steric hindrance of the methyl group next to the amino group.
Table 3. Substitution effect on the catalytic activity for producing DHU.[a]
Conversion
[%]
DHU Yield
[%][b]
Entry
R1
H
NO2
CH3
H
R2
H
Cl
H
CH3
1
2
3
4
98.6
50.4
98.5
97.4
95.1
38.6
96.5
96.1
[a] HA (20 mmol), catalyst (0.2 mmol), NMP (15 mL), P = 82 bar, T = 170 oC, t
= 4 h
Table 1. Activities of various alkali metal benzotriazolides for carboxylation of
n-hexylamine to produce dihexyl urea (DHU).[a]
This almost quantitative formation of diurea from the catalytic
reaction of CO2 with amine would be ascribed to the effective
dehydrating or protecting ability against water by the presence of
cesium benzotriazolide compounds. To this end, a set of separate
experiment was carried out by adding a different of amount of
water into the system. Stoichiometrically, 2 equiv of amine
produces one equiv of water in the carboxylation reaction, thus 20
mmol of amine produces 10 mmol of water. To our surprise, the
results summarized in Table 4 show that adding up to 10 mmol
(0.18 mL) of water does not affect seriously on the DHU yield
(84.2%, entry 3). However, a decrease in the yield of DHU was
unavoidable upon additional water more than 10 mmol (entries
4~6), resulting in a distinct negative effect on the DHU yield, and
eventually, it dropped down to 39.5% when adding 5 mL of water
(278 mmol). When comparing this ability with Cs2CO3 at the molar
ratio of 1600, the activity of compound 1 is still noticeable (entries
7 and 8). The solid 1 and Cs2CO3 are spontaneously transformed
into liquid state upon exposure to air due to their intrinsic
hygroscopic nature. After the exposure, the catalytic activity was
also compared and the results (entries 9 and 10) shows that 1
retains superior activity to Cs2CO3. From these results, it is
tentatively concluded that this impervious nature of 1 makes the
equilibrium right, providing much higher activity than others
reported up to present.
Entry
Catalyst
Amine
Conv. [%]
Urea Yield
[%][b]
48.6
71.4
74.9
78.4
95.1
89.0
78.9
82.9
20.2
60.0
N.R.
77.0
79.3
91.4
31.4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Li[BTd]
Na[BTd]
K[BTd]
Rb[BTd]
n-hexylamine
n-hexylamine
n-hexylamine
n-hexylamine
n-hexylamine
n-hexylamine
n-hexylamine
n-hexylamine
n-hexylamine
benzylamine
aniline
53.7
78.9
81.2
83.4
98.6
91.2
87.9
90.0
25.1
76.5
N.R.
87.4
86.7
96.8
40.6
Cs[BTd] (1)
Cs[triazolide] (2)
Cs[imidazolide] (3)
Cs2CO3 + BTA (1:2)
None
1
1
1
1
1
1
n-propylamine
n-butylamine
n-heptylamine
sec-butylamine
[a] HA (20 mmol), catalyst (0.2 mmol), NMP (15 mL), P = 82 bar, T = 170 oC, t
= 4 h.
[b] DHU = 1,3-dihexyl urea, After the completion of reaction, water was added
to the product mixture to precipitate the DHU, which was separated by filtration,
followed by drying in vacuum oven. The white crystalline solid were weighed to
determine the isolated yield of DHU.
To compare the activity of 1 in the carboxylation reaction with
those reported in the literature, a series of selected well-known
catalyst systems[11,14,15,19] were tested at the molar ratio
(amine/cat) of 100, at 170 oC and 82 bar of CO2 pressure for 4 h.
The results listed in Table 2 show that our catalyst (1) shows even
much higher activity than others, suggesting that cesium
benzotriazolide catalyst (1) is highly competitive to those reported
for producing disubstituted urea from amine and CO2.
Table 4. Effect of added water on the DHU yield.[a]
Molar Ratio
(HA/cat)
100
Water Content
DHU Yield
[%][b]
95.2
92.0
84.2
66.6
64.9
39.5
39.0
Entry
Catalyst
mL
0
mmol
0
1
2
3
4
5
1
1
1
1
100
100
100
100
0.10
0.18
0.30
0.50
5.00
0.72
0.72
5.6
10
16.7
27.8
278
40
Table 2. Activities of various catalysts for carboxylation of n-hexylamine.[a]
Entry
Catalyst
[Bmim]OH
CsOH/[Bmim]Cl
Cs2CO3
Conversion [%]
56.8
DHU Yield [%][b]
1
1
2
3
4
5
6
7
45.8
76.3
87.6
43.4
40.1
85.9
95.1
6
1
Cs2CO3
1
Cs2CO3
1
100
7[c]
8[c]
9
1600
1600
100
80.1
91.2
59.0
50.9
95.6
98.6
40
50.1
70.6
82.5
exposure to air[d]
exposure to air[d]
[Bmim]Cl
n-Bu4PBr
K3PO4
Cs[benzotriazolide] (1)
10
100
[a] HA (20 mmol), 1 (0.2 mmol), NMP (15 mL), P = 82 bar, T = 170 oC, t = 4 h.
[b] DHU = 1,3-dihexyl urea. [c] Catalyst (0.05 mmol), HA (80 mmol). [d]
catalyst was exposed to air for 24 h.
[a] HA (20 mmol), catalyst (0.2 mmol), NMP (15 mL), P = 82 bar, T = 170 oC, t
= 4 h. [b] DHU = 1,3-dihexyl urea.
Figure 1 shows the effect of molar ratio (HA/1) on the DHU yields
and their TOF value. As can be seen in Figure 1, although the
1 pKa value of 1 (8.2); 2 (9.3); 3 (14.4).
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601320
ChemCatChem
COMMUNICATION
yield decreases with the increase in the molar ratio, the TOF
increases very sharply up to molar ratio of 3200 and starts to drop
at 6400. Overall, the maximum TOF is found to be 344 h-1, which
is the highest among reported in the carboxylation reactions.
Figure 2. Displacement ellipsoid (50%) representation of 1a. Hydrogen atoms,
except the one at a nitrogen atom, are omitted for clarity. A N–H hydrogen atom
was located on the Fourier difference map and its position was freely refined.
Selected bond lengths [Å ] and angles [°]: Cs1···N2 3.396(3), Cs1···N4 3.209(3),
N(1)-H(1) 1.25(4), N(1)-N(2) 1.349(4), N(2)-N(3) 1.313(4), N(4)-N(5) 1.340(4),
N(5)-N(6) 1.349(4); N(2)-Cs(1)-N(4) 71.68(7), N(4)-N(5)-N(6) 111.7(3), N(1)-
N(2)-N(3) 109.9(3).
A N–H proton of the benzotriazole moiety was successfully
located in the difference density map, while no significant residual
density was observed near the benzotriazolide anion. The
geometry of this benzotriazole is almost identical to the free
benzotriazole molecule.[20] However, its C1–N1–H1 angle (141(2)
Å) is considerably distorted and the N–H bond length (1.25(4) Å)
is elongated compared to general N–H bonds (~1.01 Å). A
structurally analogous osmium benzotriazole-benzotriazolato
complex [Os(bta···H-bta)H(CO)(PPh3)2], which has a significantly
elongated N–H bond (1.265(66) Å) and a large C–N–H angle
(135°), was reported by Hursthouse and co-workers.[21] Strong
intramolecular hydrogen bonding results in the distortion of the N–
H bond. Similarly, we found intermolecular hydrogen bonding
between the benzotriazolide and benzotriazole moieties in 1a
(figure 40S and Table S8). It is likely to affect the N–H bond length,
resulting in the elongation and the distortion of this N–H moiety. It
is worth noting that the bond length of Cs1···N2 (3.396(3) Å) is
longer than Cs1···N4 (3.209(3) Å), indicating that the former has
a weaker interaction between N- and Cs+ than the latter. This
unexpected structure of 1a is quite reasonable due to the
hypothesis that it can be formed by the hydrolysis of 1 by the
presence of water according to Eq. (3) and that 1 is indeed very
hygroscopic.4 The formation of CsHCO3 can be explained from
the in situ reaction of CO2 with CsOH (intermediate), which seems
to occur without any difficulty if it is under the CO2 environment.
Figure 1. Effect of molar ratio (HA/1) on the yield and TOF.[a]
To investigate the possibility of recycling this novel catalyst, a
series of experiments were carried out with cyclohexylamine
(CHA)2 as substrate and 1 as a catalyst at 170 oC, 82 bar of CO2
for 4 h. After completion of each reaction, the product mixture was
filtered off to isolate insoluble dicyclohexyl urea (DCU), which was
then washed with MeOH to recover the possible remaining 1
present in the solid DCU, and the methanolic filtrate was added
to the mother liquor (NMP solution containing original 1), followed
by evaporation for 2 h at 60 oC under a reduced pressure of 133
mbar to remove MeOH. The resulting solution containing the
catalyst, 1 was reused for further carboxylation reactions with a
fresh charge of CHA. As can be seen in Table 5, 1 retains most
of its original activity even after five successive cycles, indicating
that 1 is, indeed, highly recyclable. Considering Table 4 (effect of
added water), a certain amount of accumulated water generated
during several cycles might have hampered the carboxylation.
This unexpected result, however, is likely due to that the amount
of water might be reduced below the critical level (entry 3, Table
4) during the evaporation step.3
Table 5. Catalyst recycling studies with 1.[a]
Cycle
Amine
CHA
CHA
CHA
CHA
CHA
Conversion [%]
DCU Yield [%][b]
1
2
3
4
5
84.7
86.6
88.1
87.5
89.9
74.7
74.1
73.7
73.2
73.1
It is reported that K3PO4 reacts with CO2 to produce KH2PO4 and
KHCO3 in the presence of water, and these are found to be active
species for the formation of DSU in the carboxylation of amines
and CO2.[19b] Therefore, it is conceivable that 1a can be an auto-
generated intermediate species from the reaction of 1 with H2O
produced during the carboxylation as by-product. Moreover, the
existence of 1a is confirmed through the single-crystal X-ray
diffraction study, which corroborates above postulation.
Indeed, when the NMR tube containing 1 in DMSO-d6 is
introduced with 0.5 equiv of water and 30 psi of 13CO2, two peaks
(7.59 and 6.85 ppm) designated to protons in benzo ring are
shifted to downfields (8.1 and 7.3 ppm) with the formation of H2O
at 5.4 ppm (Figure 3), indicating some changes of electronic
environment in the benzo ring. This can be more clearly seen in
13C NMR spectra (Figure 4). The addition of water and
[a] CHA (20 mmol), 1 (0.2 mmol), NMP (15 mL), P = 82 bar, T = 170 oC, t = 4
h.
This unprecedented high catalytic performance led us to carry out
a single-crystal X-ray diffraction study to elucidate a relationship
between structure and reactivity. Surprisingly, the structure of 1
was found to be an adduct of its protonated form,
[benzotriazole]···Cs[BTd] (1a) with an empirical formula of
C12H9CsN6 (Figure 2).
2 Cyclohexylamine (CHA) was chosen as a substrate for recycling study since
its corresponding product, dicyclohexyl urea (DCU) is insoluble in NMP and thus
it is easy to be removed by filtration for next reaction.
3 The reduced pressure and temperature during the evaporation step was 133
mbar and 60 oC, respectively, and the boiling point of water at 150 mbar is
53.9 oC, CRC Handbook, 87th Ed.
4 This hygroscopic nature of 1 might resulted in the structure in Figure 2.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601320
ChemCatChem
COMMUNICATION
introduction of 30 psi of 13CO2 results in the new carbonate peak
at 159.7 ppm, which is undoubtly responsible for in situ formation
of CsHCO3, along with a downfield shift (from 120.0 to 121.5 ppm)
of the peaks responsible for the carbon atom of benzo ring
adjacent to nitrogen. From these results, it is clear that 1a is
formed during the carboxylation by the presence of water, which,
in turn, leads to the formation of CsHCO3 with the help of CO2
atmosphere.5 Further transformation into H2CO3 from CsHCO3
cannot be proceeded, rather than, it is possible that the resulting
CsHCO3 can react with free BTA isolated from 1a to regenerate
the initial catalyst 1 as illustrated in Eq. (4), and it is experimentally
confirmed that 1 can be synthesized from the separate reaction of
BTA and CsHCO3 with 95% yield under reflux condition, and
95.2% yield under the CO2 pressure.6
Experimental Section
All the carboxylation reactions were conducted in 50-mL high pressure
bomb reactor. The reactor was charged with an amine, N-
methylpyrrolidione (NMP), and an appropriate catalyst. The reactor was
pressurized with CO2, and then heated to a specific temperature with
vigorous stirring. The pressure in the reactor was uniformly maintained
at 82 bar throughout the reaction using a gas reservoir system equipped
with a high pressure regulator and a pressure transducer. After the
completion of the reaction, the reactor was cooled to room temperature
and the reaction mixture was analyzed by GC. To isolate 1,3-disubstitued
urea, water was added to product mixture to preciptate the white crystalline
solid, which was collected by filtration and dried in oven. For the recycling
experiment, the product, dicyclohexylurea was removed by filtration, and
the resulting solution containing the catalyst was reused for further reaction
with a fresh charge of cyclohexylamine.
Acknowledgements
If these kinds of reaction take place during the carboxylation, the
initial catalyst 1 is not likely to be deactivated by the presence of
water, which might be responsible for exhibiting high activity in the
carboxylation. The results in the Table 4 (effect of added water)
also supports the advantages of using 1 as active catalyst for this
application.
This work was supported by the Ministry of Science, ICT & Future
Planning as “Fusion Research Program for Green Technologies
(2012M3C1A1054497)“ and as “C1 Gas Refinery Program
(2015M3D3A1A01064895)“ through the National Research
Foundation of Korea.
Keywords: carboxylation • cesium benzotriazolide • CO2
conversion • amine • catalysis
[1]
a) I. Omae, Catal. Today 2006, 115, 33-52; b) T. Sakakura, J.-C. Choi,
H. Yasuda, Chem. Rev. 2007, 107, 2365-2387; c) M. Mikkelsen, M.
Jorgensen, F. C. Krebs, Energy Environ. Sci. 2010, 3, 43-81; c) S.
Verma, R. B. N. Baig, M. N. Nadagouda, R. S. Varma, Green Chem 2016,
18, 4855-4858.
[2]
a) R. Zevenhoven, S. Eloneva, S. Teir, Catal. Today 2006, 115, 73-79;
b) K. M. K. Yu, C. M. Y. Yeung, S. C. Tsang, J. Am. Chem. Soc. 2007,
129, 6360-6361; c) M. Honda, S. Sonehara, H. Yasuda, Y. Nakagawa,
K. Tomishige, Green Chem. 2011, 13, 3406-3413; d) T. Kimura, K.
Kamata, N. Mizuno, Angew. Chem. Int. Ed. 2012, 51, 6700-6703; e) M.
Tamura, K. Noro, M. Honda, Y. Nakagawa, K. Tomishige, Green Chem.
2013, 15, 1567-1577; f) T. Ema, Y. Miyazaki, J. Shimonishi, C. Maeda,
J.-y. Hasegawa, J. Am. Chem. Soc. 2014, 136, 15270-15279; g) J. Hu,
J. Ma, Q. Zhu, Z. Zhang, C. Wu, B. Han, Angew. Chem. Int. Ed. 2015,
54, 5399-5403; h) Q. Liu, L. Wu, R. Jackstell, M. Beller, Nat. Commun.
2015, 6; i) W.H. Wang, Y. Himeda, J. T. Muckerman, G. F. Manbeck, E.
Fujita, Chem. Rev. 2015, 115, 12936-12973; j) P. Garcia-Dominguez, L.
Fehr, G. Rusconi, C. Nevado, Chem. Sci. 2016, 7, 3914-3918; k) J. Wang,
Y. Zhang, ACS Catal. 2016, 4871-4876.
Figure 3
1H NMR spectra of a) 1 in [d6]DMSO; (b) after adding 0.5 equiv of
.
water into the NMR tube, followed by introduction of 30 psi of 13CO2 at room
temperature.
[3]
[4]
a) P. Markewitz, W. Kuckshinrichs, W. Leitner, J. Linssen, P. Zapp, R.
Bongartz, A. Schreiber, T. E. Muller, Energy Environ. Sci. 2012, 5, 7281-
7305; b) G. Centi, E. A. Quadrelli, S. Perathoner, Energy Environ. Sci.
2013, 6, 1711-1731; c) S. Kumar, S. Verma, S. L. Jain, Tetrahedron Lett.
2015, 56, 2430-2433; d) S. Verma, R. B. N. Baig, M. N. Nadagouda, R.
S. Varma, ChemCatChem 2016, 8, 690-693.
Figure 4. 13C NMR spectra of a) 1 in [d6]DMSO; (b) after adding 0.5 equiv of
water into the NMR tube, followed by introduction of 30 psi of 13CO2 at room
temperature.
a) T. P. Vishnyakova, I. A. Golubeva, E. V. Glebova, Russ. Chem. Rev.
1985, 54, 249; b) D. P. Getman, G. A. DeCrescenzo, R. M. Heintz, K. L.
Reed, J. J. Talley, M. L. Bryant, M. Clare, K. A. Houseman, J. J. Marr, J.
Med. Chem. 1993, 36, 288-291; c) F. Bigi, R. Maggi, G. Sartori, Green
Chem. 2000, 2, 140-148; d) B. Gabriele, G. Salerno, R. Mancuso, M.
Costa, J. Org. Chem. 2004, 69, 4741-4750; e) J. A. Shimshoni, M. Bialer,
B. Wlodarczyk, R. H. Finnell, B. Yagen, J. Med. Chem. 2007, 50, 6419-
6427.
There are many advantages to cesium-based azolides catalyst.
In addition to distinguishable catalytic performance from the
reported catalyst in the carboxylation reaction, they are highly
recyclable without losing initial activity. The single-crystal X-ray
diffraction study revealed that Cs[BTd] can be transformed into
stable hydrolyzed adduct in the presence of water. Further
spectroscopic investigations to elucidate the mechanism for this
carboxylation of amines with CO2 are now under progress.
6
5 This step seems to proceed straightforwardly since there is no peak ascribed
to free 13CO2 around 125 ppm.
The 1H and 13C NMR spectra of 1 obtained under reflux and CO2 pressure
are provided in the Supporting Information (Figure 6S and 7S).
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601320
ChemCatChem
COMMUNICATION
[5]
a) G. M. Dyson, Chem. Rev. 1927, 4, 109-165; b) H. Babad, A. G. Zeiler,
Chem. Rev. 1973, 73, 75-91.
[6]
a) J. S. Oh, S. M. Lee, J. K. Yeo, C. W. Lee, J. S. Lee, Ind. Eng. Chem.
Res. 1991, 30, 1456-1461; b) T. W. Leung, B. D. Dombek, J. Chem. Soc.,
Chem. Commun. 1992, 205-206; c) H. S. Kim, Y. J. Kim, H. Lee, S. D.
Lee, C. S. Chin, J. Catal. 1999, 184, 526-534; d) H. S. Kim, Y. J. Kim, H.
Lee, K. Y. Park, C. Lee, C. S. Chin, Angew. Chem. Int. Ed. 2002, 41,
4300-4303; e) J. Chen, G. Ling, S. Lu, Euro. J. Org. Chem. 2003, 2003,
3446-3452; f) H. S. Kim, Y. J. Kim, J. Y. Bae, S. J. Kim, M. S. Lah, C. S.
Chin, Organometallics 2003, 22, 2498-2504; g) F. Ragaini, Dalton Trans.
2009, 6251-6266.
[7]
[8]
S. Chauhan, S. Chauhan, R. D’Cruz, S. Faruqi, K. K. Singh, S. Varma,
M. Singh, V. Karthik, Environ. Toxicol. Pharmacol. 2008, 26, 113-122.
a) P. Giannoccaro, C. F. Nobile, P. Mastrorilli, N. Ravasio, J. Organomet.
Chem. 1991, 419, 251-258; b) E. Bolzacchini, S. Meinardi, M. Orlandi, B.
Rindone, J. Mol. Catal. A: Chem. 1996, 111, 281-287; c) J. E. McCusker,
A. D. Main, K. S. Johnson, C. A. Grasso, L. McElwee-White, J. Org.
Chem. 2000, 65, 5216-5222; d) F. Shi, Y. Deng, T. SiMa, H. Yang,
Tetrahedron Lett. 2001, 42, 2161-2163; e) F. Shi, Y. Deng, J. Catal. 2002,
211, 548-551; f) I. Chiarotto, M. Feroci, J. Org. Chem. 2003, 68, 7137-
7139; g) M. Gasperini, F. Ragaini, C. Remondini, A. Caselli, S. Cenini, J.
Organomet. Chem. 2005, 690, 4517-4529.
[9]
a) E. M. Hampe, D. M. Rudkevich, Tetrahedron 2003, 59, 9619-9625; b)
B. Lee, K. H. Lee, B. W. Lim, J. Cho, W. Nam, N. H. Hur, Adv. Synth.
Catal. 2013, 355, 389-394.
[10] R. Nomura, Y. Hasegawa, M. Ishimoto, T. Toyosaki, H. Matsuda, J. Org.
Chem. 1992, 57, 7339-7342.
[11] T. Jiang, X. Ma, Y. Zhou, S. Liang, J. Zhang, B. Han, Green Chem. 2008,
10, 465-469.
[12] a) H. Ogura, K. Takeda, R. Tokue, T. Kobayashi, Synthesis 1978, 1978,
394-396; b) C. F. Cooper, S. J. Falcone, Synth. Commun. 1995, 25,
2467-2474.
[13] a) N. Yamazaki, F. Higashi, T. Iguchi, Tetrahedron Lett. 1974, 15, 1191-
1194; b) J. Fournier, C. Bruneau, P. H. Dixneuf, S. Lecolier, J. Org. Chem.
1991, 56, 4456-4458; c) D.-L. Sun, J.-H. Ye, Y.-X. Fang, Z.-S. Chao, Ind.
Eng. Chem. Res. 2016, 55, 64-70.
[14] F. Shi, Y. Deng, T. SiMa, J. Peng, Y. Gu, B. Qiao, Angew. Chem. Int. Ed.
2003, 42, 3257-3260.
[15] A. Ion, V. Parvulescu, P. Jacobs, D. D. Vos, Green Chem. 2007, 9, 158-
161.
[16] a) H. Walba, R. W. Isensee, J. Org. Chem. 1961, 26, 2789-2791; b) A.
R. Katritzky, S. Rachwal, G. J. Hitchings, Tetrahedron 1991, 47, 2683-
2732.
[17] a) H. Tang, C. Wu, ChemSusChem 2013, 6, 1050-1056; b) S. Seo, M.
Quiroz-Guzman, M. A. DeSilva, T. B. Lee, Y. Huang, B. F. Goodrich, W.
F. Schneider, J. F. Brennecke, J. Phys. Chem. B 2014, 118, 5740-5751.
[18] P. D. Vaidya, V. V. Mahajani, Ind. Eng. Chem. Res. 2005, 44, 1868-1873.
[19] a) Y. N. Shim, J. K. Lee, J. K. Im, D. K. Mukherjee, D. Q. Nguyen, M.
Cheong, H. S. Kim, Phys. Chem. Chem. Phys. 2011, 13, 6197-6204; b)
Y.-S. Choi, H. Kim, S. H. Shin, M. Cheong, Y. J. Kim, H. G. Jang, H. S.
Kim, J. S. Lee, Appl. Catal., B 2014, 144, 317-324.
[20] a) A. Escande, J. L. Galigné, L. Lapasset, Acta Cryst., B 1974, 30,1490-
1495; b) S. Krawczyk, M. Gdaniec, Acta Cryst., E 2005, 61, o2967-o2969.
[21] a) B. G. Olby, S. D. Robinson, M. B. Hursthouse, R. L. Short, Polyhedron
1988, 7, 1781-1783; b) B. G. Olby, S. D. Robinson, M. B. Hursthouse, R.
L. Short, J. Chem. Soc., Dalton Trans. 1990, 621-627.
This article is protected by copyright. All rights reserved.

10.1002/cctc.201601320
ChemCatChem
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
Layout 1:
COMMUNICATION
Table of Contents
Cong Chien Truong, Jin Kim, Yunho Lee,
and Yong Jin Kim*
Page No. – Page No.
Well-Defined Cesium Benzotriazolide
as Active Catalyst for Generating
Disubstituted Ureas from Carbon
Dioxide and Amines
Layout 2:
COMMUNICATION
Author(s), Corresponding Author(s)*
Page No. – Page No.
Title
Text for Table of Contents
This article is protected by copyright. All rights reserved.