MCM-41-immobilized 1,10-phenanthroline-copper(i) complex: A highly efficient and recyclable catalyst for the coupling of aryl iodides with aliphatic alcohols

Article abstract of DOI:10.1039/c6ra19825b

A heterogeneous C-O coupling reaction between aryl iodides and aliphatic alcohols was achieved in neat alcohol or toluene at 110 °C in the presence of 10 mol% of the MCM-41-immobilized 1,10-phenanthroline-copper(i) complex [MCM-41-1,10-phen-CuI] with Cs₂CO₃ as a base, yielding a variety of aryl alkyl ethers in good to excellent yields. The new heterogeneous copper catalyst can easily be prepared by a simple procedure from commercially available and inexpensive reagents, and recovered by filtration of the reaction solution and recycled at least 8 times without significant loss of activity.

Full text of DOI:10.1039/c6ra19825b

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DOI: 10.1039/C6RA19825B
MCM-41-immobilized 1,10-phenanthroline-copper(I)
complex: A highly efficient and recyclable catalyst for the
coupling of aryl iodides with aliphatic alcohols
Yang Lina, Mingzhong Caib*, Zhiqiang Fanga and Hong Zhaoa*
a School of Chemistry and Chemical Engineering, Guangdong Pharmaceutical
University, Guangzhou 510006, P. R. China
b College of Chemistry & Chemical Engineering, Jiangxi Normal University,
Nanchang 330022, P. R. China
Eꢀmail: mzcai@jxnu.edu.cn; zhaohong1001@sina.com
The heterogeneous C–O coupling reaction between aryl iodides and aliphatic alcohols
was achieved in neat alcohol or toluene at 110 ºC in the presence of 10 mol% of
MCMꢀ41ꢀimmobilized 1,10ꢀphenanthrolineꢀcopper(I) complex [MCMꢀ41ꢀ1,10ꢀPhenꢀ
CuI] with Cs2CO3 as base, yielding a variety of aryl alkyl ethers in good to excellent
yields. The new heterogeneous copper catalyst can easily be prepared by a simple
procedure from commercially available and inexpensive reagents, and recovered by
filtration of the reaction solution and recycled for at least 8 times without significant
loss of activity.
Introduction
Aryl alkyl ethers are important structures that are often found in many naturally
occurring and medicinally relevant compounds1 and important solvents and synthetic
building blocks in organic synthesis.2 The copperꢀmediated Ullmann ether synthesis is
a classical route for the preparation of these compounds.3 However, harsh reaction
conditions such as high reaction temperatures, the use of strong alkoxide bases,
stoichiometric quantities of the copper salts, and the low to moderate yields have
1

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generally restricted its synthetic applicability. Although palladiumꢀcatalyzed C–O
bond formation reactions have become effective strategies for their preparation,4 the
drawbacks of the catalyst systems, such as high cost, toxicity, the utilization of
environmental unfriendly phosphine ligands, and tedious multistep processes involved
in the synthesis of these phosphine ligands often limit their applications in largeꢀscale
preparation. In contrast, copperꢀcatalyzed Ullmann coupling between aryl halides and
alcohols is an attractive alternative for palladiumꢀcatalyzed aryl alkyl ether synthesis
due to the relatively low toxicity and cost of the catalyst, as well as a decreased
amount of βꢀH elimination.5 For these reasons, much effort has been devoted to the
development of copperꢀcatalyzed Ullmann C–O coupling reactions for the preparation
of aryl alkyl ethers.6 Although these copperꢀcatalyzed C–O coupling methods are
highly efficient for the construction of aryl alkyl ethers, about 10 mol% of copper
salts and 20 mol% of ligands are usually utilized to obtain high yields. Moreover, the
problem with homogeneous catalysis is the difficulty to separate the catalyst from the
reaction mixture and the impossibility to reuse it in consecutive reactions. It is well
known that homogeneous catalysis might result in heavy metal contamination of the
desired isolated product. These problems are of particular environmental and econoꢀ
mic concerns in largeꢀscale syntheses and in industry. To overcome these drawbacks,
development of highly efficient heterogeneous catalysts, for example by immobilizaꢀ
tion of catalytically active species onto an ideal heterogeneous support to generate a
molecular heterogeneous catalyst is essential.7 The heterogenization of C–O coupling
catalysts appears to be a logical solution; the use of immobilized catalysts could result
2

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in easy recovery and recyclability of the copper catalyst, thereby, minimizing copper
contamination of the desired isolated products and wastes derived from reaction
workup. In spite of some reports on heterogeneous copperꢀcatalyzed C–O coupling
between aryl halides and phenols in recent years,8 to the best of our knowledge, the
C–O coupling between aryl halides and aliphatic alcohols catalyzed by heterogeneous
copper complexes has not been reported until now.
The discovery of mesoporous MCMꢀ41 materials has provided a new possible
candidate for an ideal heterogeneous support for the immobilization of homogeneous
catalysts and given an enormous stimulus to research in heterogeneous catalysis.9 The
MCMꢀ41 has high surface area, large and defined pore size, big pore volume and rich
silanol groups in the inner channel walls.10 To date, some functionalized MCMꢀ41ꢀ
immobilized palladium,11 rhodium,12 molybdenum,13 gold14 and copper15 complexes
have been prepared and successfully utilized as potentially green and sustainable
catalysts in organic synthesis. In continuation of our efforts to develop economical
and ecoꢀfriendly synthetic pathways for organic transformations,11dꢀf,15 herein we wish
to report the first preparation of the MCMꢀ41ꢀimmobilized 1,10ꢀphenanthrolineꢀCuI
complex [MCMꢀ41ꢀ1,10ꢀPhenꢀCuI] and its successful application to C–O coupling
reaction between aryl iodides and aliphatic alcohols (Scheme 1). The new heteroꢀ
geneous copper catalyst exhibits high catalytic activity for the C–O coupling reaction
in neat alcohol or toluene with Cs2CO3 as base and can easily be recovered by a
simple filtration of the reaction solution, and its catalytic efficiency remains unaltered
even after recycling eight times.
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2. Results and discussion
The new MCMꢀ41ꢀimmobilized 1,10ꢀphenanthrolineꢀcopper(I) complex [MCMꢀ41ꢀ
1,10ꢀPhenꢀCuI] was easily prepared according to the procedure summarized in
Scheme 2. Firstly, the mesoporous material MCMꢀ4116 was treated with 1ꢀ(1,10ꢀ
phenanthrolinꢀ5ꢀyl)ꢀ3ꢀ(3ꢀ(triethoxysilyl)propyl)urea17 in toluene under reflux for 24 h,
followed by the silylation with Me3SiCl in toluene at room temperature for 24 h to
generate the 1,10ꢀphenanthrolineꢀfunctionalized MCMꢀ41 [MCMꢀ41ꢀ1,10ꢀPhen]. The
latter was then reacted with CuI in acetone under reflux for 24 h to afford the
MCMꢀ41ꢀimmobilized 1,10ꢀphenanthrolineꢀcopper(I) complex [MCMꢀ41ꢀ1,10ꢀPhen
ꢀCuI] as a light green powder, the copper content of the catalyst was found to be 0.75
mmol/g according to the ICPꢀAES measurements.
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The Xꢀray powder diffraction (XRD) patterns of the parent MCMꢀ41 and the
MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex are illustrated in Figure 1. Small angle Xꢀray
diffraction of the parent MCMꢀ41 gave three peaks corresponding to hexagonally
ordered mesoporous phases. For the MCMꢀ41ꢀ1,10ꢀPhenꢀCuI, the (100) reflection of
MCMꢀ41 with decreased intensity was remained after functionalization, while the
(110) and (200) reflections became weak and diffuse, which should be attributed to
contrast matching between the silicate framework and organic moieties which are
located inside the channels of MCMꢀ41. These results indicate that the structure of the
mesoporous material remains unchanged through the grafting procedure and the
formation of the catalyst has taken place preferentially inside the pore system of
MCMꢀ41. The energy dispersive Xꢀray spectroscopy (EDS) shows the elements
present in the material. EDS analysis of fresh MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex
shows the presence of Si, O, C, N, I, and Cu elements (Figure 2).
(100)
a
(110)
(200)
b
1
2
3
4
5
6
2θ (degrees)
Fig. 1 XRD patterns of MCMꢀ41 (a) and MCMꢀ41ꢀ1,10ꢀPhenꢀCuI (b).
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Fig. 2 EDS analysis of MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex.
In our initial screening experiments, the crossꢀcoupling of 4ꢀmethyliodobenzene
with butanol was chosen as the model reaction to optimize the reaction conditions,
which include base, solvent, and reaction temperature and the results are summarized
in Table 1. At first, the solvent effect was examined by using 10 mol% of MCMꢀ41
ꢀ1,10ꢀPhenꢀCuI as catalyst with Cs2CO3 as base at 110 ºC (Table 1, entries 1ꢀ6).
Among the solvents examined, toluene afforded good yield (entry 1), while other
solvents such as dioxane, DMSO, DMF and butyronitrile were substantially less
effective (entries 2ꢀ5). To our delight, when butanol was used as solvent, the reaction
proceeded smoothly in neat alcohol to give the desired product 3a in 92% yield (entry
6). We then turned our attention to investigate the effect of base on the coupling
reaction. It is evident that lower yields were obtained when other inorganic bases such
as K2CO3, Na2CO3, and K3PO4 were used and organic bases such as piperidine and
nꢀBu3N were inefficient (entries 7ꢀ11). Lowering reaction temperature to 100 ºC
resulted in a lower 78% yield (entry 12) and raising reaction temperature to 120 ºC
did not improve the yield of the desired product (entry 13). Finally, the amount of the
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catalyst was also screened and 10 mol% of MCMꢀ41ꢀ1,10ꢀPhenꢀCuI was found to be
optimal (entries 6, 14 and 15). To compare with homogeneous copper catalytic system,
10 mol% CuI and 20 mol% 1,10ꢀphenanthroline were used as the catalyst, the desired
product 3a was isolated in 93% yield (entry 16), which indicating that the catalytic
activity of the MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex is comparable to that of the homoꢀ
geneous analogue. Thus, the optimized reaction conditions for this transformation are
the MCMꢀ41ꢀ1,10ꢀPhenꢀCuI (10 mol%) in neat alcohol with Cs2CO3 as base at 110 ºC
under Ar for 24 h (entry 6).
Table 1 Crossꢀcoupling between 4ꢀmethyliodobenzene and butanol in different
conditions.a
Entry
Base
Solvent
Temp. (ºC)
Yield (%)b
1
2
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
toluene
110
110
110
110
110
110
110
110
110
110
110
100
120
84
dioxane
DMF
33
3
49
4
DMSO
36
5
butyronitrile
nꢀBuOH
nꢀBuOH
nꢀBuOH
nꢀBuOH
nꢀBuOH
nꢀBuOH
nꢀBuOH
nꢀBuOH
54
6
92
7
75
8
Na2CO3
K3PO4
67
9
46
10
11
12
13
piperidine
nꢀBu3N
Cs2CO3
Cs2CO3
trace
trace
78
91
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14c
15d
16e
Cs2CO3
Cs2CO3
Cs2CO3
nꢀBuOH
nꢀBuOH
nꢀBuOH
110
110
110
69
92
93
a All reactions were performed using 4ꢀmethyliodobenzene (0.5 mmol), nꢀBuOH (1 mmol), base
(1 mmol), 10 mol% of MCMꢀ41ꢀ1,10ꢀPhenꢀCuI, solvent (1 mL) under Ar in a sealed tube for 24 h.
b Isolated yield. c 5 mol% of copper catalyst was used. d 20 mol% of copper catalyst was used. e 10
mol% CuI and 20 mol% 1,10ꢀphenanthroline were used.
With this promising result in hand, we started to examine the scope and limitation
of this heterogeneous copperꢀcatalyzed coupling reaction between aryl iodides and
aliphatic alcohols under the optimized conditions. Firstly, reactions of aryl iodides
with inexpensive primary or secondary alcohols were examined and the results are
summarized in Table 2. The butoxylation reactions of a variety of aryl iodides bearing
both electronꢀdonating and electronꢀwithdrawing groups with nꢀBuOH (2a) proceeded
smoothly in neat nꢀBuOH at 110 ºC, leading to the corresponding aryl butyl ethers
3a-3f in good to excellent yields (78ꢀ93%) within 24 h. The results indicated that the
electronic effect of substituents on the benzene ring has limited influence on this
heterogeneous copperꢀcatalyzed C–O coupling reaction. However, the electronꢀwithꢀ
drawing substituent CN seemed to be more sensitive under the optimized coupling
conditions, which may be due to the fact that nitriles are also good ligands for copper.
When the reaction of 4ꢀiodobenzonitrile was performed in neat nꢀBuOH, a mixture of
the corresponding amide and ester as well as other decomposition products was
observed even at lower temperature and shorter reaction time. Thus, this reaction was
carried out with only 4 equiv of nꢀBuOH in toluene as a solvent for 30 h to afford the
desired 3f in 78% yield. The sterically hindered 2ꢀiodotoluene, 2ꢀnitroiodobenzene
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and bulky 1ꢀiodonaphthalene were also coupled with nꢀBuOH effectively to give the
corresponding products 3g, 3h and 3i in 94, 76 and 89% yields, respectively. It is
noteworthy that heterocyclic substrates such as 2ꢀ or 3ꢀiodopyridines and 2ꢀiodoꢀ
thiophene can also be successfully coupled with nꢀBuOH to give the corresponding
butyl heteroaryl ethers 3j-3l in good yields. The C–O coupling reactions of other
inexpensive primary alcohols such as methanol and benzyl alcohol with aryl iodides
also proceeded smoothly to furnish the corresponding aryl methyl ethers 3m, 3n and
aryl benzyl ethers 3o, 3p in high yields within 24 h. Both strong electronꢀdonating and
electronꢀwithdrawing groups on the benzene ring were tolerated well. Encouraged by
the above results, we also carried out the reaction of aryl bromides with aliphatic
alcohols, unfortunately, aryl bromides were not reactive under the present catalytic
system even at elevated temperatures. The similar observation had also been made by
Buchwald et al. using homogeneous CuI/1,10ꢀphenanthroline system.6a
The preparation of aryl alkyl ethers from secondary alcohols and aryl halides
represents a more challenging synthetic problem18 that thus far cannot be generally
solved using palladium catalysts due to the presence of βꢀhydride elimination. Thus,
we next examined the possibility of coupling common secondary alcohols that could
also serve as solvents under optimized conditions, and the results are listed in Table 2.
As shown in Table 2, isopropanol and cyclohexanol could be effectively coupled with
aryl or heteroaryl iodides to afford the desired secondary alkyl aryl ethers 3q-3s in
high yields on longer times (36 h). The coupling reactions of sterically hindered
2ꢀiodotoluene and 2ꢀiodochlorobenzene with cyclohexanol also gave the desired
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products 3t and 3u in high yields. Interestingly, 2ꢀundecanol, a long chain secondary
alcohol, was also good coupling partner and coupled with aryl iodides smoothly to
give the expected long chain secondary alkyl aryl ethers 3v and 3w in good yields.
Table 2 Coupling of aryl iodides with primary or secondary alcohols catalyzed by
MCMꢀ41ꢀ1,10ꢀPhenꢀCuIa,b
a All reactions were performed using 0.5 mmol of aryl iodide, 1 mL of R2OH, Cs2CO3 (1 mmol),
b
10 mol% of MCMꢀ41ꢀ1,10ꢀPhenꢀCuI at 110 ºC under Ar in a sealed test tube for 24 or 36 h.
Isolated yield. c 4 equiv of nꢀBuOH in 1 mL of toluene was used for 30 h. d For 36 h.
During our initial screening experiments, we found that toluene was a suitable
solvent for the coupling of 4ꢀmethyliodobenzene with nꢀBuOH (Table 1, entry 1). For
more precious alcohols, it is highly desirable to perform the reaction in a solvent
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using only a moderate excess of one of the coupling partners. We next carried out the
coupling reaction with 0.5 mmol of aryl iodide, 1.0 mmol of alcohol and 1.0 mmol of
Cs2CO3 in toluene (1 mL) at 110 ºC for 36 h. To demonstrate the scope of this heteroꢀ
geneous copperꢀcatalyzed method, allylic alcohols, substituted benzyl alcohols, and
pyridineꢀ3ꢀmethanol were used as substrates and the results are listed in Table 3. Conꢀ
sidering the fact that paraꢀsubstituted electronꢀrich aryl halides are poor substrates for
the corresponding palladiumꢀcatalyzed transformations, we chose 4ꢀiodoanisole as the
aromatic coupling partner for the allylic alcohols. As shown in Table 3, the primary
allylic alcohols gave the corresponding allyl aryl ethers 3x and 3y in high yields. The
electronꢀrich pꢀ, mꢀ, or oꢀiodotoluenes were also good substrates for 4ꢀmethylbenzyl
alcohol and afforded the corresponding aryl 4ꢀmethylbenzyl ethers 3z-3b' in good
yields. It is noteworthy that the coupling reactions of sterically hindered 2ꢀmethylꢀ
benzyl alcohol with the electronꢀrich 4ꢀiodoanisole or 4ꢀiodotoluene in toluene could
proceed smoothly to give the coupling products 3c' and 3d' in 94 and 79% yields,
respectively. The reaction of pyridineꢀ3ꢀmethanol with 4ꢀiodoanisole furnished the
desired 3e' in 65% yield. Interestingly, the coupling reaction between both sterically
hindered substrates, 2ꢀchloroiodobenzene and 2ꢀmethylbenzyl alcohol in toluene also
proceeded effectively to provide the corresponding ether 3f' in good yield.
Table 3 Heterogeneous copperꢀcatalyzed coupling of aryl iodides with aliphatic
alcohols using toluene as solvent.a,b
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Me
Me
O
Me
Me
O
O
Me
3y, 89%
MeO
Me
MeO
Me
3x, 87%
3z, 73%
Me
Me
Me
O
O
O
Me
MeO
3a', 78%
3b', 72%
3c', 94%
Cl
O
O
N
O
Me
MeO
Me
Me
3e', 65%
3d', 79%
3f', 69%
a All reactions were performed using 0.5 mmol of aryl iodide, 1 mmol of R2OH, 1 mmol of
Cs2CO3, 10 mol% of MCMꢀ41ꢀ1,10ꢀPhenꢀCuI in toluene (1 mL) at 110 ºC under Ar in a sealed
test tube for 36 h. b Isolated yield.
To determine whether the observed catalysis was due to the heterogeneous catalyst
MCMꢀ41ꢀ1,10ꢀPhenꢀCuI or to a leached copper species in solution, the reaction of
4ꢀmethyliodobenzene (1a) with butanol (2a) was carried out until an approximately
50% conversion of 1a was reached. Then the MCMꢀ41ꢀ1,10ꢀPhenꢀCuI catalyst was
removed from the reaction mixture by hot filtration19 and the filtrate was again stirred
in a sealed tube at 110 ºC under Ar atmosphere for 20 h. In this case, no significant
increase in conversion was observed, demonstrating that leached copper species from
the supported catalyst (if any) are not responsible for the observed catalysis. It was
confirmed by ICPꢀAES analysis that no copper species could be detected in the
filtrate (below the detection limit). These results indicated that the catalyst was stable
during the reactions and the observed catalysis was intrinsically heterogeneous.
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MCM-41
R2OH + Cs2CO3
(2)
2 (3)
Ar-O-R
N
N
CuI
CsI + CsHCO3
MCM-41
MCM-41
N
N (A)
N
N (B)
Cu(III)I
Cu(I)
Ar
OR2
OR2
(1)
Ar-I
Scheme 3. Plausible mechanism.
Recently, Casitas and Ribas have described the role of organometallic copper(III)
complexes in homogeneous catalysis.20 Although experimental evidences were lackꢀ
ing, organometallic copper(III) species have been invoked in many copperꢀcatalyzed
reactions. This heterogeneous copperꢀcatalyzed C–O coupling reaction of aryl iodides
with aliphatic alcohols may proceed through oxidative addition followed by a reduc
tive elimination process (Scheme 3). Firstly, the reaction of MCMꢀ41ꢀ1,10ꢀPhenꢀCuI
with R2OH 2 in the presence of Cs2CO3 affords an MCMꢀ41ꢀimmobilized 1,10ꢀphenꢀ
anthrolineꢀCu(I)–OR2 intermediate A. Then oxidative addition of ArꢀI 1 to interꢀ
mediate A forms an MCMꢀ41ꢀimmobilized 1,10ꢀphenanthrolineꢀArCu(III)I–OR2
intermediate B. Finally, intermediate B undergoes a reductive elimination to give the
desired product 3 and regenerate the MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex.
For the practical application of a heterogeneous transitionꢀmetal catalyst system its
stability and reusability are important factors. We next examined the recyclability of
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the MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex by using coupling reaction between 2ꢀmethylꢀ
iodobenzene (0.5 mmol) and nꢀBuOH with Cs2CO3 (1.0 mmol) as base in nꢀBuOH (1
mL) in the presence of 10 mol% of MCMꢀ41ꢀ1,10ꢀPhenꢀCuI at 110 ºC in a sealed tube
under argon atmosphere for 24 h. After carrying out the reaction, the catalyst was
separated by simple filtration and washed with distilled water and EtOH. After being
airꢀdried, it can be reused directly without further purification. The recovered copper
catalyst was used in the next run, and almost consistent activity was observed for 8
consecutive cycles (Fig. 3). In addition, copper leaching in the supported catalyst was
also determined. The copper content of the catalyst was found by ICP analysis to be
0.74 mmol/g after eight consecutive runs, only 1.3% of copper had been lost from the
MCMꢀ41 support. The satisfactory reusability of the catalyst should result from the
chelating action of bidentate 1,10ꢀphenanthroline ligand on copper and the mesoꢀ
porous structure of the MCMꢀ41 support. The result is important from industrial and
environmental points of view. The high catalytic activity and excellent reusability of
MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex make it a highly attractive heterogeneous copper
catalyst for the parallel solution phase synthesis of diverse libraries of compounds.
100
80
60
40
20
0
1
2
3
4
5
6
7
8
Reused times
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Fig. 3 Recycle of the MCMꢀ41ꢀ1,10ꢀPhenꢀCuI catalyst.
Conclusions
In summary, we have developed a novel, highly efficient and practical method for the
synthesis of aryl alkyl ethers through C–O coupling reaction of aryl iodides with
aliphatic alcohols by using an MCMꢀ41ꢀimmobilized 1,10ꢀphenanthrolineꢀcopper(I)
complex [MCMꢀ41ꢀ1,10ꢀPhenꢀCuI] as catalyst and Cs2CO3 as base in neat alcohol or
toluene at 110 ºC under Ar atmosphere. The reactions generated a variety of aryl alkyl
ethers in good to excellent yields under mild and green conditions and were appliꢀ
cable to a wide range of aryl iodides and various primary or secondary aliphatic
alcohols. The new heterogeneous copper catalyst can be easily prepared by a simple
procedure from commercially available and inexpensive reagents and recycled for at
least 8 times without significant loss of catalytic activity. The use of recyclable copper
catalyst along with mild and environmentꢀfriendly reaction conditions will make this
methodology a powerful complement to the traditional C–O coupling reactions.
Experimental
All chemicals were reagent grade and used as purchased. All solvents were dried and
distilled before use. Mesoporous material MCMꢀ41 was prepared by standard
protocol.16 1ꢀ(1,10ꢀPhenanthrolinꢀ5ꢀyl)ꢀ3ꢀ(3ꢀ(triethoxysilyl)propyl)urea was prepared
via the addition of 5ꢀaminoꢀ1,10ꢀphenanthroline to 3ꢀ(triethoxysilyl)propyl isocyanate
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according to a literature procedure.17 The products were purified by flash chromatoꢀ
graphy on silica gel. Mixture of EtOAc and hexane was generally used as eluent. All
coupling products were characterized by comparison of their spectra and physical data
with authentic samples. 1H NMR spectra were recorded on a Bruker Avance 400 MHz
spectrometer with TMS as an internal standard in CDCl3 as solvent. 13C NMR spectra
(100 MHz) were recorded on a Bruker Avance 400 MHz spectrometer in CDCl3 as
solvent. Copper content was determined with inductively coupled plasma atom
emission Atomscan16 (ICPꢀAES, TJA Corporation). Xꢀray powder diffraction was
obtained on Damax–γA (Rigaku). Xꢀray energy dispersive spectroscopy (EDS) was
performed using a microscope.
Preparation of the 1,10-phenanthroline-functionalized MCM-41 (MCM-41-1,10-
Phen)
A solution of 1.47 g of 1ꢀ(1,10ꢀphenanthrolinꢀ5ꢀyl)ꢀ3ꢀ(3ꢀ(triethoxysilyl)propyl)urea in
9 mL of dry chloroform was added to a suspension of 1.10 g of the MCMꢀ41 in 90
mL of dry toluene. The mixture was stirred for 24 h at 110 °C under Ar. Then the solid
was filtered and washed by CHCl3 (2 × 20 mL), and dried in vacuum at 160 °C for 5 h.
The product was then soaked in a solution of 4.2 g of Me3SiCl in 80 mL of dry
toluene at room temperature under stirring for 24 h. Then the solid was filtered,
washed with acetone (3 × 20 mL) and diethyl ether (3 × 20 mL), and dried in vacuum
at 120 °C for 5 h to obtain 1.53 g of hybrid material MCMꢀ41ꢀ1,10ꢀPhen. The
nitrogen content was found to be 3.66 mmol/g by elemental analysis.
Preparation of the MCM-41-1,10-Phen-CuI catalyst
In a small Schlenk tube, 1.2 g of the aboveꢀfunctionalized MCMꢀ41 material (MCMꢀ
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41ꢀ1,10ꢀPhen) was mixed with 0.21 g (1.1 mmol) of CuI in 20 mL of dry acetone. The
mixture was refluxed for 24 h under an argon atmosphere. The solid product was
filtered by suction, washed with acetone, distilled water and acetone successively and
dried at 70 °C/26.7 Pa under Ar for 5 h to give 1.33 g of a light green copper complex
[MCMꢀ41ꢀ1,10ꢀPhenꢀCuI]. The nitrogen and copper contents were found to be 3.41
mmol/g and 0.75 mmol/g, respectively.
General procedure for the heterogeneous copper-catalyzed C–O coupling of aryl
iodides with aliphatic alcohols
A test tube equipped with a magnetic stirring bar was charged under Ar with MCMꢀ
41ꢀ1,10ꢀPhenꢀCuI (67 mg, 0.05 mmol), Cs2CO3 (326 mg, 1.0 mmol), aryl iodide (0.5
mmol), and either (a) the alcohol (1 mL) or (b) the alcohol (1.0 mmol) and toluene (1
mL). The test tube was sealed, and the reaction mixture was stirred at 110 ºC for
24ꢀ36 h. The reaction mixture was cooled to room temperature and then diluted with
EtOAc (20 mL), and filtered. The MCMꢀ41ꢀ1,10ꢀPhenꢀCuI complex was washed with
distilled water (2 × 5 mL) and EtOH (3 × 5 mL), and reused in the next run. The
filtrate was concentrated under reduced pressure and the residue was purified by flash
column chromatography on silica gel to provide the desired product.
Acknowledgements
We thank the National Natural Science Foundation of China (No. 21272044) and
Scientific Research Fund of Education Department of Jiangxi Province (KJLD13022)
for financial support.
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Graphical contents entry
MCM-41-immobilized 1,10-phenanthro-
line-copper(I) complex: A highly efficient
and recyclable catalyst for the coupling of
aryl iodides with aliphatic alcohols
Yang Lin, Mingzhong Cai*, Zhiqiang
Fang, Hong Zhao*
A practical method for the synthesis of aryl alkyl ethers has been
developed by a heterogeneous Cu-catalyzed C–O coupling.