Recyclable porous polymer-supported copper catalysts for Glaser and Huisgen 1,3-diolar cycloaddition reactions

Article abstract of DOI:10.1002/asia.201300690

A family of polymer-attached phenanthrolines was prepared from solvothermal copolymerization of divinylbenzene with N-(1,10-phenanthroline-5-yl)acrylamide in different ratios. The polymer-supported copper catalysts were obtained through typical impregnation with copper(II) salts. The polymers and supported copper catalysts have been characterized by N₂ adsortion, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TG); they exhibit a high surface area, hierarchical porosity, large pore volume, and high thermal and chemical stabilities. The copper catalyst has proved to be highly active for Glaser homocoupling of alkynes and Huisgen 1,3-diolar cycloaddition of alkynes with benzyl azide under mild conditions at low catalyst loading. The heterogeneous copper catalyst is more active than commonly used homogeneous and nonporous polystyrene-supported copper catalysts. In particular, the catalyst is easily recovered and can be recycled at least ten times without any obvious loss in catalytic activity. Metal leaching was prevented due to the strong binding ability of phenanthroline and products were not contaminated with copper, as determined by ICP analysis. At the Copper, Coppercabana: Stable, porous polymer-attached phenanthrolines were successfully prepared from solvothermal copolymerization of divinylbenzene with N-(1,10-phenanthrolin-5-yl)acrylamide (PCP-Phen). After coordination with copper species, a heterogeneous copper catalyst was obtained that displayed a higher activity in Glaser and Huisgen couplings than commonly used homogeneous and nonporous polystyrene-supported copper catalysts. The copper catalyst has excellent recyclability due to the strong coordination ability of phenanthrolines. Copyright

Full text of DOI:10.1002/asia.201300690

FULL PAPER
FULL PAPER
Supported Catalysts
Qi Sun, Zhonfei Lv, Yuyang Du,
Qinming Wu, Liang Wang,
Longfeng Zhu, Xiangju Meng,*
Wanzhi Chen,*
Feng-Shou Xiao*
&&&& — &&&&
At the Copper, Coppercabana: Stable,
porous polymer-attached phenanthro-
lines were successfully prepared from
solvothermal copolymerization of
divinylbenzene with N-(1,10-phenan-
throlin-5-yl)acrylamide (PCP-Phen).
After coordination with copper spe-
cies, a heterogeneous copper catalyst
was obtained that displayed a higher
activity in Glaser and Huisgen cou-
plings than commonly used homogene-
ous and nonporous polystyrene-sup-
ported copper catalysts. The copper
catalyst has excellent recyclability due
to the strong coordination ability of
phenanthrolines.
Recyclable Porous Polymer-Supported
Copper Catalysts for Glaser and
Huisgen 1,3-Diolar Cycloaddition
Reactions
Chem. Asian J. 2013, 00, 0 – 0
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Feng-Shou Xiao et al.
DOI: 10.1002/asia.201300690
Recyclable Porous Polymer-Supported Copper Catalysts for Glaser and
Huisgen 1,3-Diolar Cycloaddition Reactions
[
a]
[a]
[a]
[a]
[a, b]
[b]
Qi Sun, Zhonfei Lv, Yuyang Du, Qinming Wu, Liang Wang,
L[ao]ngfeng Zhu,
[
a]
[a]
Xiangju Meng,* Wanzhi Chen,* and Feng-Shou Xiao*
Abstract: A family of polymer-attached
phenanthrolines was prepared from
solvothermal copolymerization of di-
vinylbenzene with N-(1,10-phenanthro-
line-5-yl)acrylamide in different ratios.
The polymer-supported copper cata-
lysts were obtained through typical im-
pregnation with copper(II) salts. The
polymers and supported copper cata-
face area, hierarchical porosity, large
pore volume, and high thermal and
chemical stabilities. The copper catalyst
has proved to be highly active for
Glaser homocoupling of alkynes and
Huisgen 1,3-diolar cycloaddition of al-
kynes with benzyl azide under mild
conditions at low catalyst loading. The
heterogeneous copper catalyst is more
active than commonly used homogene-
ous and nonporous polystyrene-sup-
ported copper catalysts. In particular,
the catalyst is easily recovered and can
be recycled at least ten times without
any obvious loss in catalytic activity.
Metal leaching was prevented due to
the strong binding ability of phenan-
throline and products were not conta-
minated with copper, as determined by
ICP analysis.
lysts have been characterized by N ad-
2
Keywords: copper
·
Glaser
sortion, scanning electron microscopy
coupling · heterogeneous catalysis ·
Huisgen 1,3-dipolar cycloaddition ·
phenanthroline ligand · polymers
(
SEM), transmission electron microsco-
py (TEM), and thermogravimetric
analysis (TG); they exhibit a high sur-
Introduction
carbon–heteroatom bonds under relatively mild conditions
[3]
is important. Although copper-based homogenous catalysts
show good activity and selectivity, the difficulties of their
separation from the products and the reusability of the cata-
lysts restrict their wide applications. Copper-based heteroge-
neous catalysts can be easily separated from the reaction
system, but usually they have a lower activity. Because con-
ventional inorganic supports such as silica-based materials
usually show low wettability to organic reactants and organ-
ic supports such as polystyrene have a low degree of active
Transition-metal-catalyzed carbon–carbon and carbon–het-
eroatom bond-forming reactions have been pivotal in cur-
rent organic synthesis as well as in pharmaceutical and ma-
terial sciences. Among the metal-catalyzed transforma-
tions, copper-mediated reactions have been attracting con-
tinuous attention over the last two decades due to the low
cost and low toxicity of copper compared to noble metal
catalysts. However, the copper-catalyzed transformation
involving carbon–carbon and carbon–heteroatom bond for-
mation usually requires harsh reaction conditions (e.g., high
temperature, large amount of copper catalyst). Therefore,
the development of more versatile and efficient copper/
ligand systems for the formation of carbon–carbon and
[
1]
[2]
[4]
sites due to their low surface area, the development of cat-
alytically active and recyclable copper-based heterogeneous
catalysts is still a challenge.
Recently, we have reported a series of unique and stable
porous cross-linked polymers (PCPs) featuring a high sur-
face area, hierarchical porosity, large pore volume, high
thermal and chemical stabilities, and easy introduction of or-
[
a] Q. Sun, Z. Lv, Y. Du, Q. Wu, L. Wang, Dr. X. Meng, Prof. W. Chen,
Prof. F.-S. Xiao
Department of Chemistry
[5]
ganic ligands. Phenanthroline (Phen) has a strong coordi-
nation ability towards copper and an excellent activity in
Zhejiang University
[6]
many copper-catalyzed reactions; thus, PCPs incorporating
Hangzhou 310028 (P. R. China)
Fax : (+86)571-88273698
E-mail: mengxj@zju.edu.cn
fsxiao@zju.edu.cn
Phen may constitute good polymeric ligands that combine
the advantages of low leaching of metals and recyclability.
Herein, we describe the synthesis of porous PCP-Phen and
the corresponding polymer-supported copper catalyst, which
possesses an excellent catalytic activity and recyclability in
Glaser coupling and Huisgen cycloaddition reactions.
[
b] L. Wang, L. Zhu
State Key Laboratory of Inorganic Synthesis and Preparative Chemis-
try
Jilin University
Changchun 130012 (P. R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201300690.
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Feng-Shou Xiao et al.
Results and Discussion
N-(1,10-Phenanthroline-5-yl)acrylamide (Phen-MA) was
easily obtained from 1,10-phenanthroline through nitration,
reduction, and amidation, as depicted in Scheme 1. Co-poly-
Figure 1. (A) Representative SEM image of PCP-Phen-Cu. (B–D) C, N,
and Cu elemental mapping in the area marked by the rectangle in panel
a. Scale bars, 60 mm.
Scheme 1. Synthesis of PCP-Phen-Cu catalyst.
merization of N-(1,10-phenanthroline-5-yl)acrylamide with
divinylbenzene (DVB) under solvothermal conditions af-
forded the copolymer of DVB and Phen-MA. Variation of
the mass ratio (x) of Phen-MA and DVB gave PCP-x-Phen
with different surface areas, pore volumes, and pore size dis-
tributions (Table S1, Supporting Information).When the
Phen-MA/DVB ratio was 1:4, the co-polymer had a high
2
À1
3
À1
surface area (574 m g ), a large pore volume (0.72 cm g ),
and a large pore size (average BJH pore size of ca.
10.8 nm). Therefore, PCP-1/4-Phen prepared from Phen-
MA and DVB at ratio of 1:4 (henceforth abbreviated as
PCP-Phen) was selected as the catalyst support for subse-
quent studies. The polymer-supported copper catalyst was
obtained through the reaction of PCP-Phen with Cu-
ACHTUNGTRENNUNG( CH COO) ·H O in an acetone/water mixture (1:1 v/v), and
3 2 2
PCP-Phen-Cu was obtained after washing and drying.
Next, PCP-Phen and PCP-Phen-Cu were characterized.
Figure 1 shows that PCP-Phen-Cu exhibits a uniform distri-
bution of C, N, and Cu. The results suggest that PCP-Phen
is a copolymer rather than a mixture of polydivinylbenzene
and polymerized Phen-MA and that the dispersion of Cu
species is uniform. Thermographic analysis of PCP-Phen
shows that there is no weight loss below 3008C (Figure S1,
Supporting Information) suggesting its good thermal stabili-
Figure 2. (A) N
2
adsorption–desorption isotherms. (B) Pore size distribu-
tions of PCP-Phen (a) and PCP-Phen-Cu (b) samples. For the latter, iso-
3
À1
therms in (A) have been offset by 200 cm g . (C,D) SEM images of
PCP-Phen (C) and PCP-Phen-Cu (D). TEM images of PCP- Phen (E)
and PCP-Phen-Cu (F).
ty. Figure 2A shows the N adsorption–desorption isotherms
2
of PCP-Phen and PCP-Phen-Cu samples. Both PCP-Phen
and PCP-Phen-Cu exhibit a typical type-IV plus type I be-
havior. The steep increase that occurs in the relative pres-
sure less than 0.01 is due to the filling of micropores, and
the hysteresis loop that appears at a relative pressure of
of ca. 7.5 nm) (Figure 2B and the Supporting Information,
Figure S2 and Table S1). Scanning electron microscopy
(SEM) and transmission electron microscopy (TEM) images
of PCP-Phen and PCP-Phen-Cu samples are shown in Fig-
ure 2C–2F, and they provide direct evidence of hierarchical
porosity. The N 1s XPS (X-ray photoelectron spectroscopy)
spectra of PCP-Phen and PCP-Phen-Cu are shown in
Figure 3. PCP-Phen shows a binding energy at 399.4 eV, and
PCP-Phen-Cu exhibits a relatively high binding energy at
0.45–0.90 is assigned to the presence of mesoporosity in the
samples. These results indicate that PCP-Phen-Cu also has
2
À1
a high surface area (542 m g ), as well as a large pore
3
À1
volume (0.41 cm g ) and pore size (average BJH pore size
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Feng-Shou Xiao et al.
lyst loading of 0.1 mol%, the turnover number (TON)
reached up to 930 (entry 4). To the best of our knowledge,
this TON is the highest among those known heterogeneous
[9]
copper-based catalysts. For comparison, a polystyrene-
phen (PS-Phen)-supported copper catalyst showed much
lower activity for the oxidative coupling of phenylacetylene
(
entry 6). The polystyrene used has a low surface area of
2
À1
less than 1 m g . These results suggest that the surface area
of the catalysts may play an important role in determining
the efficiency of the catalysts.
Figure 3. N 1s XPS spectra of PCP-Phen (a) and PCP-Phen-Cu (b).
The PCP-Phen-Cu catalyst can be easily recovered by fil-
tration after the reaction. The recovered catalyst can be
reused at least ten times without any obvious loss in activity
(Table 2). Meanwhile, no copper species could be detected
in the filtrate by ICP analysis, thus suggesting that the heter-
ogeneous catalyst is very stable with no detectable copper
leaching.
400.2 eV. Obviously, the higher binding energy of PCP-
Phen-Cu originates from the strong coordination of copper
[7]
species to Phen. The molar ratio of Phen:Cu is 1.07 in the
PCP-Phen-Cu sample according to elemental and inductive-
ly coupled plasma analyses.
Diyne derivatives are a very important class of com-
pounds used as key structural elements in natural product
Table 2. Recycling of PCP-Phen-Cu in the oxidative homocoupling of
phenylacetylene.
[a]
[8]
synthesis and material science. We examined the catalytic
activity of PCP-Phen-Cu for oxidative homocouplings of al-
kynes. For comparision, a variety of other copper-based cat-
alysts were also studied under the same conditions, and the
results are summarized in Table 1. Notably, PCP-Phen-Cu
was highly active under oxygen atmosphere at 1208C for the
conversion of phenylacetylene giving 1,4-diphenyl-1,3-buta-
diyne in quantitative yield (Table 1, entry 1). Even under at-
mospheric air (entry 2) or at room temperature (entry 3),
Cycle
1
2
3
4
5
6
7
8
9
10
97
[
b]
Yield(%)
99
99
99
99
98
99
97
98
97
[
a] Reaction conditions: alkyne (1 mmol), DMF (4 mL), PCP-Phen-Cu
(
2
2.5 mol%), 1 atm of O , 1208C, 40 min. [b] GC yield.
Encouraged by the results described above, we extended
the homocouplings catalyzed by PCP-Phen-Cu to other al-
kynes, and the results are presented in Table 3. The results
show that the PCP-Phen-Cu catalyst is highly active for ho-
mocouplings of a variety of alkynes. The reactions of aro-
matic alkynes could be completed within 40 minutes, afford-
ing the corresponding diynes in nearly quantitative yields.
Terminal aliphatic alkynes could also be oxidized to the cor-
1,4-diphenyl-1,3-butadiyne could also be obtained in nearly
quantitative yields at an elongated reaction time. At a cata-
Table 1. Catalytic performance in oxidative homocoupling of phenylace-
[
a]
tylene over various catalysts.
Table 3. Oxidative homocouplings of alkynes under various reaction con-
ditions.
[
b]
Entry
1
Catalyst
t [min]
Yield [%]
TON
[
a]
PCP-Phen-Cu
PCP-Phen-Cu
PCP-Phen-Cu
PCP-Phen-Cu
PCP-Phen-Cu
PS-Phen-Cu
Cu-Y zeolite
Cu-HPA
40
>99(97)
>99
>99
93
2.7
32
97
93
90
94
>99
<1
18
31
>99
67
40
40
40
[
[
[
[
c]
d]
e]
f]
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
240
1080
1440
180
1440
900
1080
30
[
b]
Entry
R
Solvent
T [8C] t [min] Yield [%]
930
1.1
320
3.3
468
9
666
100
<0.4
7.3
10
1
2
3
4
5
6
7
8
p-Methyl-phenyl
p-Anisole
m-Methyl-phenyl
DMF
DMF
DMF
120
120
120
120
120
120
120
100
80
40
40
40
180
180
180
40
>99(97)
>99(96)
>99(95)
>94(85)
98(95)
95(91)
>99
>99
>99
>99
89
62
87
3
<1
<1
37
2.5
[
[
[
g]
h]
i]
1-Hydroxycyclohexyl DMF
Butyl
Heptane
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
DMF
DMF
DMF
DMF
DMF
DMF
DMSO
NMP
Cu(OH)
Cu(OH)
x
/TiO
/OMS-2
2
[
[
j]
0
1
2
3
4
5
6
x
10
k]
CuNP/TiO
Cu-MCM-41
Cu(OAc) ·H
CuI
Phen+Cu
Phen+Cu(OAc)
2
240
180
180
180
30
60
9
150
480
40
40
40
40
40
40
180
180
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
2
O
10
11
12
13
1
1
1
1
1
60
120
120
[
[
l]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(OAc)
2
2
·H
·H
2
2
O
O
40
670
m]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
1440
benzonitrile 120
acetonitrile 85
toluene
4
5
6
7
8
[
(
a] Reaction conditions: alkyne (1 mmol), DMF (4 mL), Cu catalyst
2.5 mol%), 1208C, and 1 atm of O . [b] GC yield (isolated yield). [c] In
air. [d] At room temperature. [e] Phenylacetylene (5 mmol) and Cu
0.5 mol%). [f] In N . [g] Ref. [9a]. [h] Ref. [9b]. [i] Ref. [9c]. [j] Ref. [9d].
k] Ref. [9e]. [l] Cu(OAc) ·H (2.5 mol%) and 1,10-phenanthroline
110
2
1,4-dioxane 110
H
H
2
2
O
O
120
RT
(
[
2
Ph
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
2
O
(
(
2.5 mol%) were used as the catalyst. [m] Phenylacetylene (5 mmol), Cu
0.5 mol%) and 1,10-phenanthroline (0.5 mol%).
[a] Reaction conditions: alkyne (1 mmol), solvent (4 mL), PCP-Phen-Cu
(2.5 mol%), O
2
(1 atm). [b] GC yield (isolated yield).
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Feng-Shou Xiao et al.
responding diynes, but they are relatively inert and thus re-
quired longer reaction times (entries 4–6). In addition, the
results show that increased temperatures can accelerate the
reaction (entries 7–10). Moreover, the effect of solvents
shows that polar aprotic solvents such as N,N-dimethylfor-
mamide (DMF) are more suitable for the reactions (en-
tries 11–18).
again, and the yield of diyne almost reached 99%. When
the brown catalyst was used in phenylacetylene coupling, no
diyne could be obtained. These results imply that the reduc-
2
+
+
tion of Cu to Cu species by alkynes and re-oxidation of
+
2+
Cu to Cu species by oxygen are involved in the catalytic
cycles.
The copper-catalyzed azide–alkyne cycloaddition discov-
ered by Melda and Sharpless has attracted much attention
due to its wide applications for synthesizing fine chemicals,
We observed that during the reaction the color of the
PCP-Phen-Cu catalyst changed from dark green to brown
within about 4 minutes and then turned back to dark green
after about 40 minutes when phenylacetylene was nearly
completely converted (Figure S3 in the Supporting Informa-
tion). The color change might correspond to the change of
[
12]
+
pharmaceuticals, and functional materials, where Cu spe-
[13]
cies are catalytically active. As PCP-Phen-Cu is reduced
to a Cu catalyst in the presence of alkynes, the PCP-Phen-
+
Cu catalyst should be active for Huisgen couplings. Indeed,
we found that PCP-Phen-Cu is quite efficient for azide–
alkyne cycloaddition of various alkynes (Table 4), even
[9b]
the chemical state of the copper species, and we charac-
terized this change of PCP-Phen-Cu by XPS and ESR spec-
troscopies. The dark green PCP-Phen-Cu shows a binding
energy of Cu 2p3/2 at 935.5 eV with a satellite peak at
Table 4. Azide-alkyne cycloaddition reactions over PCP-Phen-Cu cata-
943.3 eV (Figure 4A), thereby indicating that the oxidation
[a]
lyst.
[b]
À1
Entry
R
t [min]
Yielid [%]
TOF [h ]
1
2
3
4
5
6
7
Ph
40
40
40
40
80
100
100
99
98
99
97
94
97
93
2970
2940
2970
2910
1410
1164
1116
m-Methyl-phenyl
p-Methyl-phenyl
p-Anisole
1-Hydroxycyclohexl
Heptane
Butyl
[
a] Reaction conditions: alkynes (5.25 mmol), benzyl azide (5 mmol),
PCP-Phen-Cu (0.05 mol%), water (5 mL), RT. [b] Isolated yield.
when 0.05 mol% of PCP-Phen-Cu was used. The reactions
of benzyl azide and alkynes could be accomplished within
1
9
00 min, thereby affording the corresponding products in
3–99% yields (entry 1–10). For example, the cycloaddition
of benzylazide and phenylacetylene yielded the tetrazole in
almost quantitative yield within 40 min, and the TOF
Figure 4. (A) XPS and (B) ESR spectra of fresh catalyst (a), the brown
catalyst in the reaction (b), and the catalyst after the reaction (c).
À1
reached 2970 h (entry 1), which is higher than those of
[12s]
most of the reported heterogeneous catalysts.
state of the copper species is +2. The brown catalyst
formed during the reaction exhibits a binding energy of Cu
The PCP-Phen-Cu catalyst can also be easily recovered
by filtration in azide–alkyne cycloadditions. The catalyst can
be recycled at least ten times without an obvious loss in ac-
tivity (Table 5). More importantly, copper species are unde-
tectable in the isolated triazole. By contrast, when CuSO4
and Cu/C were used as catalysts, the concentration of
2p3/2 at 933.9 eV without any satellite peaks, thus indicating
that the chemical state of Cu has changed. When the reac-
tion was finished, the catalyst became dark green again, in-
dicating that the chemical state of copper species returned
[10]
À1
to +2. ESR spectroscopy (Figure 4B) revealed that both
copper is as high as 399 and 76 mgg in the product. This is
dark-green catalysts had characteristic ESR signals associat-
probably because phenanthroline (log K=9.2) has a much
stronger coordination ability than triazole (log K<2.5),
2
+
[14]
ed with Cu species with g-values at about 2.2, while the
+
[11]
brown one was ESR-inactive associated with Cu species.
Notably, when the reactions were carried out under N at-
2
mosphere, the color change of the catalyst from dark green
to brown was also very fast (ca. 4 min), and the brown color
remained unchanged even after a long reaction time (3 h),
after which the yield of diyne was close to the catalyst
amount. However, after introducing oxygen to the reaction,
the color of the catalyst turned to dark green (ca. 40 min)
Table 5. Recycling of PCP-Phen-Cu in the cycloaddition of benzylazide
and phenylacetylene.
[
a]
Cycle
1
2
3
4
5
6
7
8
9
10
97
[
b]
Yield (%)
99
99
99
99
98
99
97
98
97
[
a] Reaction conditions: alkyne 1 mmol, DMF 4 mL, PCP-Phen-Cu
2.5 mol%, 1 atm of O and reaction at 1208C for 40 min. [b] GC yield.
2
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Feng-Shou Xiao et al.
thus preventing copper leaching. Obviously, this feature is
very important for the industrial production of fine chemi-
cals and pharmaceuticals by Huisgen 1,3-diolar cycloaddi-
tion of azide–alkyne.
excellent catalytic activity in Glaser coupling and Huisgen
cycloaddition reactions. The PCP-Phen-Cu catalyst is easily
recovered and can be reused for at least ten times without
any obvious loss in catalytic activity. The copper is tightly
anchored to the polymeric support due to the strong binding
ability of phenanthroline and thus product contamination
arising from metal leaching is avoided.
Similar to the homocoupling of alkynes, the color of the
catalyst changed from dark green to brown within 5 min due
2
+
+
to the reduction of Cu to Cu (Figure S4 in the Support-
ing Information), and trace amounts of 1,3-diyne derivatives
were detected. After the color of the catalyst changed to
brown, no more 1,3-diyne derivatives were formed in the
system, and the azide–alkyne cycloaddition dominated im-
mediately. As a result, the 1,4-substituted-1,2,3-triazole
product was obtained with a very high selectivity and a high
yield. Table 6 presents the dependence of the catalyst load-
ing and solvent on the cycloaddition of benzylazide and phe-
nylacetylene. When 1.0 mol% of PCP-Phen-Cu was used in
water, the reaction of phenylacetylene and benzyl azide was
completed within 5 min (Table 6, entry 1). At the catalyst
loading of 0.01 mol%, the reaction was completed when the
reaction time was extended to 6 h (entry 4). For comparison,
Experimental Section
Synthesis of PCP with Phen Ligands
In a typical procedure, DVB (15 mmol, 2 g) and Phen-MA (2 mmol,
0
.5 g) were dissolved in DMF (20 mL), followed by addition of azobisiso-
butyronitrile (AIBN, 0.05 g). After stirring for 3 h at room temperature,
the mixture was transferred into an autoclave for 24 h at 1008C. After ex-
traction of the solvent with EtOH, a brown solid product was obtained,
which was denoted as PCP-Phen.
Synthesis of the PCP-Phen-Cu Catalyst
The PCP-Phen-Cu catalyst was synthesized by reacting the PCP-Phen
sample with copper acetate in an acetone/water mixture (1:1 v/v). The
mixtures were stirred at room temperature for 24 h, filtered off, and
washed with excessive amounts of the acetone/water mixture and water
in order to remove physisorbed copper species. Subsequently, the catalyst
was dried overnight in air at 908C to afford a dark green copper-support-
ed catalyst, denoted as PCP-Phen-Cu. Inductively coupled plasma (ICP)
analysis showed a Cu content of 3.2 wt% in the resultant sample.
Cu ACHTUNGTRENNUNG( OAc) ·H O and 1,10-phenanthroline in water resulted in
2 2
a much lower conversion (8% yield at 20 min and 50%
yield at 1.5 h, entries 6 and 7). These results indicate that
PCP-Phen-Cu is highly active for azide–alkyne cycloaddi-
tion. The solvent screening experiments showed that alco-
hols are also better solvents than aprotic solvents (entries 8–
Catalytic Tests
12).
Glaser couplings. A terminal alkyne (1mmol), DMF (4mL), and PCP-
Phen-Cu (2.5mol%) were added to a Schlenk tube, sealed, and purged
Table 6. The effects of the catalyst amount and solvents on the activities
in cycloaddition of benzylazide and phenylacetylene over PCP-Phen-Cu
catalyst.
2
with O for four times. After the reaction, the catalyst was removed from
the system by centrifugation (5 min, 8000 rpm) and the solution was ana-
lyzed by gas chromatography (GC-1690 Kexiao Co., equipped with
a flame ionization detector) on a flexible quartz capillary column coated
with DB-1. In some cases, the diynes were isolated and purified by
column chromatography on silica gel (200–300 mesh) using EtOAc/petro-
[
a]
1
leum ether (1:10 v/v) as eluent. All products were confirmed by H NMR
[b]
À1
Entry Catalyst [mol%] Solvent
t [min] Yield [%]
TOF [h ]
spectroscopy.
1
2
3
4
5
6
7
8
9
1
1
1
1
0.1
0.05
0.01
0.005
1
H
H
H
H
H
H
H
2
2
2
2
2
2
2
O
O
O
O
O
O
O
5
>99
>99
>99
>99
82
8
50
97
96
1188
2970
2970
1980
1367
24
Huisgen 1,3-diolar cycloaddition. A terminal alkyne (5.25mmol), an
azide (5.0mmol), H O (5mL), and PCP-Phen-Cu (0.05mol%) were
2
20
40
300
720
20
90
40
40
added to a Schlenk tube, followed by sealing. After the reaction, EtOAc
(20mL) was added and the catalyst was removed by centrifugation. The
solution was then analyzed by gas chromatography. In some cases, the
products were isolated and purified by column chromatography on silica
gel (200–300 mesh) using EtOAc/petroleum ether (1:10 v/v) as eluent.
[
[
c]
c]
1
33
1
0.05
0.05
0.05
0.05
0.05
butanol
MeOH
acetonitrile 40
DMF
toluene
2910
2880
2910
1590
2460
All products were confirmed by H NMR spectroscopy.
0
1
2
97
53
82
40
40
[
(
(
a] Reaction conditions: phenylacetylene (5.25 mmol), benzylazide
Acknowledgements
5 mmol), solvent (5 mL), RT. [b] GC yield. [c] Cu
2.5 mol%) and 1,10-phenanthroline (2.5 mol%) were used.
2 2
ACHTUNGTRNENUG( OAc) ·H O
This work was supported by theNSFC (U1162201 and 21003107), the Na-
tional High-Tech Research and Development program of China
(
2013AA065301), the Science and Technology Innovative Team of Zhe-
jiang Province (No. 2012R10014-01), and the Fundamental Research
Funds for the Central Universities (2013XZZX001).
Conclusions
In summary, a phenanthroline-functionalized polymer (PCP-
Phen) with a high surface area, large pore volume, hierarchi-
cal porosity, and high thermal stability has been successfully
synthesized from the copolymerization of Phen-MA and
DVB. The PCP-Phen-supported copper catalyst shows an
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Chem. Asian J. 2013, 00, 0 – 0
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ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ