A metal-organic framework Cu2(BDC)2(DABCO) as an efficient and reusable catalyst for Ullmann-type N-arylation of imidazoles

Article abstract of DOI:10.1007/s10562-014-1355-9

A highly porous metal-organic framework (Cu₂(BDC)₂(DABCO)) was synthesized and used as an efficient and recyclable heterogeneous catalyst for the Ullmann-type N-arylation of aryl halides with imidazoles. The Cu₂(BDC)₂(DABCO) was characterized by several techniques, including X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared, atomic absorption spectrophotometry, and nitrogen physisorption measurements. The catalyst offered high activity under mild conditions, confirming outstanding advantages when employing the Cu₂(BDC)₂(DABCO) as catalyst for Ullmann-type N-arylation reaction. The catalyst could be separated from the reaction mixture by simple filtration, and could be reused without a significant degradation in catalytic activity.

Full text of DOI:10.1007/s10562-014-1355-9

Catal Lett
DOI 10.1007/s10562-014-1355-9
A Metal–Organic Framework Cu (BDC) (DABCO)
2
2
as an Efficient and Reusable Catalyst for Ullmann-Type
N-Arylation of Imidazoles
Tung T. Nguyen Nam T. S. Phan
•
Received: 13 June 2014 / Accepted: 26 August 2014
Ó Springer Science+Business Media New York 2014
Abstract A highly porous metal–organic framework
(
1 Introduction
Cu (BDC) (DABCO)) was synthesized and used as an
2 2
efficient and recyclable heterogeneous catalyst for the
Ullmann-type N-arylation of aryl halides with imidazoles.
The Cu (BDC) (DABCO) was characterized by several
Metal-mediated cross coupling reactions recently have
attracted considerable attention in the synthesis of both
simple and highly complex molecules [1]. Among various
protocols reported to date, the conventional Ullmann-type
C–N coupling reaction has been considered as one of the
most important transformations due to the molecules being
obtained are often structural motifs of numerous remark-
able biological and pharmacological agents [2]. Significant
effort has been devoted toward developing atom econom-
ical methods of Ullmann-type N-arylation, including novel
catalytic systems such as palladium [3, 4], copper [5, 6],
and iron [7]. However, these protocols generally suffered
from serious drawbacks such as elevated temperature, long
reaction time, the cost and instability of catalysts. Con-
sidering the need for large-scale or even industrial appli-
cations, it remains highly desirable to develop more
efficient catalysts for the N-arylation of nitrogen hetero-
cycles [8].
2
2
techniques, including X-ray powder diffraction, scanning
electron microscopy, transmission electron microscopy,
thermogravimetric analysis, Fourier transform infrared,
atomic absorption spectrophotometry, and nitrogen physi-
sorption measurements. The catalyst offered high activity
under mild conditions, confirming outstanding advantages
when employing the Cu (BDC) (DABCO) as catalyst for
2
2
Ullmann-type N-arylation reaction. The catalyst could be
separated from the reaction mixture by simple filtration,
and could be reused without a significant degradation in
catalytic activity.
Keywords Cu (BDC) (DABCO) ꢀ N-arylation ꢀ
2
2
Coupling reaction, imidazoles ꢀ
Metal–organic frameworks
Metal–organic frameworks (MOFs) are a rapidly grow-
ing class of porous and crystalline materials comprising
inorganic vertices (metal ions or clusters) and organic struts
by coordinate bonds [9–11]. Their key benefits as compared
to conventional organic or inorganic counterparts such as
zeolites or silicas are due to large internal surface areas,
structural flexibility, relatively good thermal stability and
chemical tunability [10, 12]. For these reasons, MOFs have
been proposed to have several potential applications in the
areas of chemical detection, drug delivery, molecular sep-
aration, gas storage, and catalysis [13, 14]. As one of the
ideal candidates for new directions in catalyst design and
application [15], MOFs have been recently employed as
efficient catalysts for various transformations [16, 17].
Although promising results have been achieved, the use of
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-014-1355-9) contains supplementary
material, which is available to authorized users.
T. T. Nguyen (&) ꢀ N. T. S. Phan
Department of Chemical Engineering, HCMC University of
Technology, VNU-HCM, 268 Ly Thuong Kiet, District 10,
Ho Chi Minh City, Viet Nam
e-mail: tungtn@hcmut.edu.vn
N. T. S. Phan
e-mail: ptsnam@hcmut.edu.vn
123

T. T. Nguyen, N. T. S. Phan
MOFs for transition metal catalyzed coupling reactions
without being modified has been relatively rare [18]. As a
continuation of our interest in the development of cross
coupling reactions employing MOFs as efficiently hetero-
geneous and reusable catalysts in view of green chemistry
analysis heated samples from 60 to 280 °C at 10 °C/min and
held them at 280 °C for 2 min. Inlet temperature was set
constant at 280 °C. MS spectra were compared with the
spectra gathered in the NIST library.
[
19, 20], herein we report a copper-catalyzed N-arylation of
2.2 Synthesis of the Metal–Organic Framework
Cu (BDC) (DABCO)
aryl halides and imidazoles using Cu (BDC) (DABCO) as
2
2
2
2
a novel catalyst. High activity was observed, and the
Cu (BDC) (DABCO) catalyst could be reused without
In a typical preparation as mentioned in our previous report
2
2
significant degradation in activity.
[20], a mixture of H BDC (H BDC = 1,4-benzenedicarb-
2
2
oxylic acid; 0.506 g, 3.1 mmol), DABCO (DABCO = 1,4-
diazabicyclo(2.2.2)octane; 0.188 g, 1.67 mmol), and
Cu(NO ) ꢀ3H O (0.8 g, 3.3 mmol) was dissolved in DMF
2
Experimental
3
2
2
0
(
DMF = N,N -dimethylformamide; 80 ml). The resulting
2
.1 Materials and Instrumentation
solution was then distributed to four 20 ml vials. The vial
was heated at 120 °C in an isothermal oven for 48 h,
forming blue crystals. After cooling the vial to room
temperature, the solid product was removed by decanting
with mother liquor and washed with DMF (3 9 10 ml).
Solvent exchange was carried out with methanol
(3 9 10 ml) at room temperature. The product was then
dried at 140 °C for 6 h under vacuum, yielding 0.57 g of
the metal–organic framework Cu (BDC) (DABCO) as
All reagents and starting materials were obtained com-
mercially from Sigma-Aldrich and Merck, and were used
as received without any further purification unless other-
wise noted. Nitrogen physisorption measurements were
conducted using a Micromeritics 2020 volumetric adsorp-
tion analyzer system. Samples were pretreated by heating
under vacuum at 100 °C overnight. A Netzsch Ther-
moanalyzer STA 409 was used for thermogravimetric
analysis (TGA) with a heating rate of 10 °C/min under a
nitrogen atmosphere. X-ray powder diffraction (XRD)
patterns were recorded using a Cu Ka radiation source on a
D8 Advance Bruker powder diffractometer. Scanning
electron microscopy studies were conducted on a S4800
Scanning Electron Microscope (SEM). Transmission elec-
tron microscopy studies were performed using a JEOL
JEM 1400 Transmission Electron Microscope (TEM) at
2
2
light blue crystals (66 % based on 1,4-benzenedicarboxylic
acid).
2.3 Catalytic Studies
The Cu (BDC) (DABCO) was used as a catalyst for the
2
2
0
N-arylation of 4 -iodoacetophenone and imidazole. A
0
mixture of 4 -iodoacetophenone (0.246 g, 1 mmol) and
n-hexadecane (0.1 ml, 0.88 mmol) as an internal standard
1
00 kV. The Cu (BDC) (DABCO) sample was dispersed
2
in DMF (4 ml) was added into a 25 mL flask containing
t
the Cu (BDC) (DABCO) catalyst and KO Bu (0.224 g,
2
on holey carbon grids for TEM observation. Elemental
analysis with atomic absorption spectrophotometry (AAS)
was performed on an AA-6800 Shimadzu. Fourier trans-
form infrared (FT-IR) spectra were obtained on a Bruker
TENSOR37 instrument, with samples being dispersed on
potassium bromide pallets.
2
2
2 mmol) as a base. The catalyst concentration was calcu-
0
lated with respect to the copper/4 -iodoacetophenone molar
ratio. Imidazole (0.204 g, 3 mmol) was then added, and the
resulting mixture was stirred at 120 °C for 3 h. Reaction
conversion was monitored by withdrawing aliquots from
the reaction mixture at different time intervals, quenching
with aqueous NaOH solution (1 % w/w, 1 ml). The
organic components were then extracted into diethyl ether
(2 ml), dried over anhydrous Na SO , analyzed by GC
Gas chromatographic (GC) analyses were performed
using a Shimadzu GC 2010-Plus equipped with a flame
ionization detector (FID) and an SPB-5 column
(
length = 30 m, inner diameter = 0.25 mm, and film
2
4
thickness = 0.25 lm). The temperature program for GC
analysis heated samples from 100 to 280 °C at 40 °C/min
and held them at 280 °C for 2.5 min. Inlet and detector
temperatures were set constant at 280 °C. n-Hexadecane
was used as an internal standard to calculate reaction con-
versions. GC–MS analyses were performed using a Hewlett
with reference to n-hexadecane. The product identity was
further confirmed by GC–MS. To investigate the recycla-
bility of Cu (BDC) (DABCO), the catalyst was separated
2
2
from the reaction mixture by simple centrifugation, washed
with copious amounts of DMF, dried under air at room
temperature for 1 h, and reused if necessary. For the
leaching test, a catalytic reaction was stopped after 30 min,
analyzed by GC, and centrifuged to remove the solid cat-
alyst. The reaction solution was then stirred for a further
Packard GC–MS 5972 with
length = 30 m, inner diameter = 0.25 mm, and film
thickness = 0. 5 lm). The temperature program for GC–MS
a RTX-5MS column
(
1
23

Catalyst for Ullmann-Type N-Arylation of Imidazoles
1
50 min. Reaction progress, if any, was monitored by
GC as previously described. For homogeneity test,
Cu(NO ) ꢀ3H O (5 mol %), H BDC (5 mol %), and
3
2
2
2
DABCO (5 mol %) were used as catalytic mixture for the
reaction. After 30 min of reaction time, the reaction mix-
ture was centrifuged and the mother liquor was further
stirred for a further 150 min under control of GC. Fur-
thermore, copper content of the mother liquor was con-
firmed by ICP analysis.
3
Results and Discussion
3
.1 Catalyst Synthesis and Characterization
Fig. 1 X-ray powder diffractograms of the as-synthesized (a) and
activated (b) Cu (BDC) (DABCO)
2
2
In this work, the Cu (BDC) (DABCO) was characterized
2
2
by various techniques. The experimental contents of copper
and nitrogen were determined to be 3.60 mmol/g and
3
.55 mmol/g by elemental analysis. The XRD powder
diffractogram patterns of the resulting solid are being
compared to the previously reported ones with the presence
o
o
of sharp peaks at 2h = 8 and 9 , confirming the formation
of Cu (BDC) (DABCO) [21, 22] (Fig. 1). FT-IR spectra of
2
2
the Cu (BDC) (DABCO) exhibited a significant difference
2
2
as compared to those of the H BDC and the DABCO,
2
showing the deprotonation of –COOH groups in the
H BDC upon the reaction with copper cations (Fig. 2). The
2
nitrogen adsorption isotherm of the Cu (BDC) (DABCO)
2
2
presented a typical type-I profile with relatively high
2
Langmuir surface area of 1605 m /g (Fig. S1) and a
˚
median pore width of 4.2 A (Fig. S2). TGA result indicated
Fig. 2 FT-IR spectra of 1,4-benzenedicarboxylic acid (a) 1,4-diaza-
2 2
bicyclo[2.2.2]octane (b) and the Cu (BDC) (DABCO) (c)
that the material was stable up to over 250 °C (Fig. S3).
A SEM micrograph (Fig. S4), in consistent with the TEM
observation (Fig. S5), confirmed that a highly crystalline
material was achieved.
R
X
N
R'
3
.2 Catalytic Studies
u (
BDC
) (
DABCO
)
HN
C
2
2
N
R'
N
DMF
The Cu (BDC) (DABCO) was assessed for its catalytic
2
2
R
R
0
activity in the N-arylation of imidazole with 4 -iodoace-
tophenone to form 1-(4-acetyl)phenyl imidazole as the
principal product. Interestingly, acetophenone was also
detected by GC as the by-product of dehalogenation reac-
X: -I, Br, Cl
R'
: -H, C H , NO
6
5 2
R: -COCH , H, CH , OCH , NO
2
3
3
3
Scheme 1 The N-arylation of aryl halides and imidazoles using the
Cu (BDC) (DABCO) as catalyst
0
2
2
tion of 4 -iodoacetophenone (Scheme 1). Initial studies
addressed the effect of temperature on the reaction con-
version (Table 1). It was found that the reaction proceeded
with difficulty at room temperature, with only 5 % con-
respectively (entry 2–4). More important, the temperature
exhibited a dramatic effect on the reaction selectivity. A
selectivity of 75 % to 1-(4-acetyl)phenyl imidazole was
detected in the reaction mixture being carried out at
120 °C. As expected, this selectivity was found to slightly
0
version of 4 -iodoacetophenone was observed (entry 1).
Remarkable conversions were obtained for the reaction
being carried out at higher temperature, affording 74, 75,
and 82 % conversion after 3 h at 100, 110, and 120 °C,
123

T. T. Nguyen, N. T. S. Phan
0
Table 1 N-arylation of 4 -iodoacetophenone and imidazole over the Cu
2
(BDC)
2
(DABCO)
N
N
O
(
(
A)
HN
Cu (BDC) (DABCO)
2
2
O
N
I
B)
O
o
Temp. ( C)
a
Entry
[Cu] cat. (mol %)
Molar ratio
Base
Solvent
Conversion (%)
Selectivity (A) (%)
1
2
3
4
5
6
7
8
9
30
5
5
5
5
3
2
5
5
5
5
5
5
5
5
1:2
1:2
1:2
1:2
1:2
1:2
1:1
1:3
1:3
1:3
1:3
1:3
1:3
1:3
K
K
K
K
K
K
K
K
3
3
3
3
3
3
3
3
PO
PO
PO
PO
PO
PO
PO
PO
4
4
4
4
4
4
4
4
DMF
DMF
5
trace
67
100
110
120
120
120
120
120
120
120
120
120
120
120
0
74
75
82
83
76
84
85
97
77
96
42
96
90
DMF
73
DMF
75
DMF
65
DMF
57
DMF
47
DMF
76
KOH
CO
DMF
64
10
11
12
13
14
K
2
3
DMF
68
t
KO Bu
t
KO Bu
t
KO Bu
t
KO Bu
DMF
81
p-xylene
NMP
100
70
n-butanol
78
Reaction conditions: 4 -iodoacetophenone (1 mmol), imidazole, base (2 mmol), solvent (4 ml), 3 h. Conversions and selectivities were deter-
mined by GC using n-hexadecane as internal standard
a
0
-iodoacetophenone:imidazole molar ratio
4
go down when the temperature was decreased to 110 and
00 °C, respectively. Another important factor that should
observed in the reaction mixture using 3 equivalents of
imidazole after 3 h (entry 4, 7–8).
1
be seriously taken into consideration in the copper-based
N-arylation reaction is the catalyst concentration. It should
be noted that almost no reaction occurred in the absence of
the Cu (BDC) (DABCO) as catalyst, indicating the
As for most transition metal-catalyzed arylation reac-
tions, the presence of at least one equivalent of a base
should be required to speed up the transmetallation step in
the catalytic cycle of the reaction. We therefore decided to
investigate the effect of different bases, including K PO ,
2
2
important role of the copper-based MOF catalyst. Experi-
mental results showed that the change of catalyst loading
did not considerably enhance the reaction rate. However,
the selectivity did change remarkably when decreasing the
copper concentration, with only 65 and 57 % of 1-(4-acet-
yl)phenyl imidazole being determined by GC in the reaction
3
4
t
KOH, K CO , and KO Bu, on the N-arylation of imidazole
2
3
0
and 4 -iodoacetophenone using the Cu (BDC) (DABCO) as
2
2
t
catalyst (entry 8–11). It was found that KO Bu was the most
effective base for this transformation, with 96 % conversion
and 81 % selectivity being achieved after 3 h. As the nature
of the solvent is assumed to have a remarkable impact on
mixture after 3 h at 3 mol % and 2 mol % of the Cu2
0
0
(
BDC) (DABCO), respectively (entry 4–6). The 4 -iodo-
2
the coupling of 4 -iodoacetophenone and imidazole, dif-
acetophenone:imidazole molar ratio was also crucial for the
N-arylation reaction. While no significant improvement of
reaction yield was noticed on raising the ratio from 1:1 to
ferent solvents such as p-xylene, NMP, n-butanol, and DMF
were also examined (entry 12–14). It shown that DMF
exhibited better performance and should be the solvent of
0
1
:3, a remarkable enhancement in the product selectivity was
choice for the N-arylation of 4 -iodoacetophenone and
achieved with 76 % of 1-(4-acetyl)phenyl imidazole being
imidazole using the Cu (BDC) (DABCO) catalyst.
2
2
1
23

Catalyst for Ullmann-Type N-Arylation of Imidazoles
In order to confirm if copper species leached from the
solid Cu (BDC) (DABCO) catalyst could be significantly
homogeneity test confirmed that a specific amount of copper
source (based on ICP result) could play a role as catalyst for
the transformation. These results obviously confirmed that
the coupling reaction could only proceed in the presence of
the solid Cu (BDC) (DABCO) catalyst, and the contribution
2
2
active in the N-arylation reaction of imidazole with
0
4
-iodoacetophenone, a controlled experiment was performed
using a simple filtration during the course of the reaction. It
was observed that no further conversion to form more 1-(4-
acetyl)phenyl imidazole was achieved for the N-arylation
transformation after the solid Cu (BDC) (DABCO) catalyst
2
2
from leached active copper species in the solution phase, if
any, was negligible (Fig. 3). For the development of more
environmentally benign processes, the recoverability and
reusability of the Cu (BDC) (DABCO) catalyst in the
2
2
was separated from the reaction mixture. Furthermore, the
2
2
0
N-arylation coupling between imidazole with 4 -iodoaceto-
phenone was investigated. It was found that the Cu2
(BDC) (DABCO) catalyst could be recovered and reused
2
several times without a significant degradation in catalytic
activity. Indeed, a conversion of more than 95 % was still
th
achieved in the 5 run (Fig. 4). Moreover, the XRD pattern
(Fig. S6), FT-IR spectrum (Fig. S7), and the SEM micro-
graph (Fig. S8) of the reused Cu (BDC) (DABCO) indicated
2
2
the crystallinity and structure of the catalyst could be
maintained during the course of the reaction.
To further explore the scope of the N-arylation trans-
formations, various aryl halides as well as nitrogen het-
erocycles were employed under optimized conditions
(Table 2). It could be found that aryl iodides bearing
electron donating groups, such as methyl or methoxy,
slowed down the reaction rate (entry 2–3). Notably, none
of the desired products were detected when 4-iodophenol
and 4-iodoaniline were used as substrates (entry 4–5).
Several aryl bromides and chlorides were also employed,
and good to excellent conversions were obtained for the
compounds bearing electron withdrawing groups (entry
6–13). Indeed, though aryl chlorides are much cheaper and
more available than aryl bromides and iodides, their reac-
tivity in N-arylation of nitrogen heterocycles has been
remarkably rare [23, 24]. Besides, the effect of different
imidazoles was also investigated using the Cu (BDC)
Fig. 3 Leaching test indicated no contribution from homogeneous
catalysis of active copper species leaching into reaction solution
2
2
(
DABCO) as catalyst in our study (Table 3). It was
observed that the presence of electron-withdrawing or
donating groups on the imidazole ring did not affect the
1
00
-
reaction rate significantly. Sterically bulkier substrates such
8
6
4
2
0
0
0
0
0
as benzimidazole or 2-phenyl imidazole also efficiently
0
coupled with 4 -iodoacetophenone employing the Cu
2
(BDC) (DABCO) as catalyst, with 84 and 75 % conver-
2
1
st time
sions being observed after 3 h (entry 3–4). Interestingly,
the absence of acetophenone being detected in the reaction
mixture when using these imidazole derivatives as the
N-arylation agent indicated that dehalogenation reaction
did not occur in the cases. Further studies, however, would
be needed to elucidate the correlation of the nature of
imidazoles and the reaction rate of the cleavage of C-hal-
ogen reaction.
2nd time
3
4
5
rd time
th time
th time
0
30
60
90
120
150
180
Time (min)
Fig. 4 Catalyst recycling studies
123

T. T. Nguyen, N. T. S. Phan
Table 2 N-arylation of various
aryl halides and imidazole over
the Cu (BDC) (DABCO)
Entry
Aryl halides
Main products (A)
By-
Conversion Selectivity
products
(%)
(A) (%)
2
2
(
B)
I
N
N
1
2
55
100
58
I
N
N
29
22
0
I
N
N
O
3
4
5
65
O
O
I
N
N
OH
trace
trace
HO
HO
I
N
N
NH2
0
H N
2
H N
2
Br
N
N
6
7
35
71
100
64
Br
N
N
O
O
O
b
Br
Br
N
N
NO2
8
100
100
O N
2
O N
2
b
O N
N
NO2
9
2
100
95
100
100
88
O N
N
2
b
NO2
N
NO2
1
0
NO2
Br
N
Cl
N
O
1
1
63
N
Reaction conditions: aryl halide
1 mmol), imidazole (3 mmol),
Cu (BDC) (DABCO)
5 mol %), KO Bu (2 mmol),
DMF (4 ml), 3 h. Conversions
and selectivities were
determined by GC using
n-hexadecane as internal
standard
O
(
O
2
2
t
c
Cl
N
(
12
10
100
100
N
Cl
N
NO2
13
100
N
O N
a
2
After 1 h
O N
2
b
2
h
2 3
mmol of Cs CO as a base,
6
1
23

Catalyst for Ullmann-Type N-Arylation of Imidazoles
Table 3 N-arylation of
0
Entry
Nitrogen
Main products (A)
By-
Conversion Selectivity
4
-iodoacetophenone and
different imidazoles over
Cu (BDC) (DABCO)
heterocycles
products
(%)
(A) (%)
2
2
(
B)
H
N
O
O
1
75
100
N
N
N
O
H
O N
2
2
77
100
N
NO2
N
N
N
O
H
N
N
N
O
O
3
4
84
75
100
100
N
Reaction conditions:
0
O
4
-iodoacetophenone (1 mmol),
H
N
imidazoles (3 mmol),
Cu (BDC) (DABCO)
5 mol %), KO Bu (2 mmol),
2
2
t
N
N
N
(
DMF (4 ml), 3 h. Conversions
and selectivities were
determined by GC using
n-hexadecane as internal
standard
O
4
Conclusions
6. Panda N, Jena AK, Mohapatra S, Rout SR (2011) Tetrahedron
Lett 52:1924–1927
7
. Taillefer M, Xia N, Ouali A (2007) Angew Chem Int Ed
6:934–936
In summary, highly crystalline porous metal–organic
framework Cu (BDC) (DABCO) was synthesized and
4
2
2
8. Zhang R, Miao C, Wang S, Xia C, Sun W (2013) ChemCatChem
5:142–145
9
0. Nguyen JG, Cohen SM (2010) J Am Chem Soc 132:4560–4561
1. Farha OK, Hupp JT (2010) Acc Chem Res 43:1166–1175
used as an efficient heterogeneous catalyst for the N-ary-
lation of aryl halides and imidazoles. The Cu (BDC)
. Wang Z, Cohen SM (2007) J Am Chem Soc 129:12368–12369
2
2
1
1
(
DABCO) catalyst could be separated from the reaction
mixture by simple filtration, and could be reused without a
significant degradation in catalytic activity. Our results
indicated that the Cu (BDC) (DABCO) could be used as
12. Farha OK, Malliakas CD, Kanatzidis MG, Hupp JT (2010) J Am
Chem Soc 132:950–952
1
1
3. Tanabe KK, Cohen SM (2009) Angew Chem Int Ed 48:7424–7427
4. Bae Y-S, Spokoyny AM, Farha OK, Snurr RQ, Hupp JT, Mirkin
CA (2010) Chem Commun 46:3478–3480
2
2
an efficient recyclable catalyst for the reaction, thus
offering a route to green chemistry for the synthesis of
phenyl imidazole derivatives. Further investigations would
15. Roberts JM, Fini BM, Sarjeant AA, Farha OK, Hupp JT, Scheidt
KA (2012) J Am Chem Soc 134:3334–3337
1
1
1
1
2
6. Janssens N, Wee LH, Bajpe S, Breynaert E, Kirschhock CEA,
Martens JA (2012) Chem Sci 3:1847–1850
7. Lili L, Xin Z, Jinsen G, Chunming X (2012) Green Chem
focus on the (in) stability of the Cu (BDC)(DABCO) on
2
different conditions.
1
4:1710–1720
8. Li Z-H, Xue L-P, Wang L, Zhang S-T, Zhao B-T (2012) Inorg
Chem Commun 27:119–121
9. Phan NTS, Nguyen TT, Ho P, Nguyen KD (2013) ChemCatChem
References
5
:1822–1831
0. Phan NTS, Nguyen TT, Nguyen VT, Nguyen KD (2013)
ChemCatChem 5:2374–2381
1
2
. Maiti D (2011) Chem Commun 47:8340–8342
. Zhang R, Miao C, Shen Z, Wang S, Xia C, Sun W (2012)
ChemCatChem 4:824–830
21. Tan K, Nijem N, Canepa P, Gong Q, Li J, Thonhauser T, Chabal
YJ (2012) Chem Mater 24:3153–3167
3
4
5
. Kataoka N, Shelby Q, Stambuli JP, Hartwig JF (2002) J Org
Chem 67:5553–5566
. Anderson KW, Tundel RE, Ikawa T, Altman RA, Buchwald SL
22. Uemura T, Ono Y, Kitagawa K, Kitagawa S (2008) Macromol-
ecules 41:87–94
23. Cao C, Lu Z, Cai Z, Pang G, Shi Y (2012) Synth Commun
42:279–284
24. Zhu L, Cheng L, Zhang Y, Xie R, You J (2007) J Org Chem
72:2737–2743
(2006) Angew Chem Int Ed 45:6523–6527
. Huang Z, Li F, Chen B, Xue F, Chen G, Yuan G (2011) Appl
Catal A 403:104–111
123