Practical oxidative homo- and heterocoupling of terminal alkynes catalyzed by immobilized copper in MCM-41

Article abstract of DOI:10.1002/ejoc.201200359

A practical oxidative homo- and heterocoupling of terminal alkynes was achieved in CH₂Cl₂ at 25 °C by using a 3-(2-aminoethylamino)propyl-functionalized MCM-41-immobilized copper(I) complex (MCM-41-2N-CuI, 1 mol-%) as the catalyst, piperidine (0.1 or 3 equiv.) as the base, and air as the environmentally friendly co-oxidant, yielding a variety of symmetrical and unsymmetrical 1,4-disubstituted 1,3-diynes in good to excellent yields. This heterogeneous copper catalyst showed a higher catalytic activity than CuI and can be recovered and recycled by a simple filtration of the reaction mixture and used for at least 10 consecutive runs without any decrease in activity. A practical oxidative homo- and heterocoupling of terminal alkynes was achieved in CH₂Cl₂ at 25 °C by using a 3-(2-aminoethylamino)propyl-functionalized MCM-41-immobilized copper(I) complex (MCM-41-2N-CuI, 1 mol-%) as the catalyst and air as the environmentally friendly oxidant, yielding a variety of symmetrical and unsymmetrical 1,4-disubstituted 1,3-diynes in good to excellent yields.

Full text of DOI:10.1002/ejoc.201200359

Job/Unit: O20359
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Date: 12-06-12 18:14:06
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FULL PAPER
DOI: 10.1002/ejoc.201200359
Practical Oxidative Homo- and Heterocoupling of Terminal Alkynes Catalyzed
by Immobilized Copper in MCM-41
Ruian Xiao,[a] Ruiya Yao,[a] and Mingzhong Cai*[a]
Keywords: 1,3-Diynes / Supported catalysts / Copper / C–C coupling / Heterogeneous catalysis
A practical oxidative homo- and heterocoupling of terminal
alkynes was achieved in CH2Cl2 at 25 °C by using a 3-(2-
aminoethylamino)propyl-functionalized MCM-41-immobi-
lized copper(I) complex (MCM-41–2N-CuI, 1 mol-%) as the
catalyst, piperidine (0.1 or 3 equiv.) as the base, and air as
the environmentally friendly co-oxidant, yielding a variety of
symmetrical and unsymmetrical 1,4-disubstituted 1,3-diynes
in good to excellent yields. This heterogeneous copper cata-
lyst showed a higher catalytic activity than CuI and can be
recovered and recycled by a simple filtration of the reaction
mixture and used for at least 10 consecutive runs without any
decrease in activity.
Introduction
oxidative homocoupling of terminal alkynes.[8] Very re-
cently, solvent-free systems mediated by copper have also
been used for the synthesis of 1,3-diynes.[9]
Diynes and polyynes have been widely used as important
building blocks in organic synthesis,[1] and 1,3-conjugated
diynes occur widely in numerous natural products, pharma-
ceuticals, and bioactive compounds with, for example, anti-
inflammatory, antifungal, anti-HIV, antibacterial, or anti-
cancer activities.[2] In addition, 1,3-conjugated diynes play
an important role in the construction of a variety of func-
tional polymeric materials, such as nonlinear-optical mate-
rials, electrically conductive plastics, high-density and high-
strength fibers, and liquid crystals.[3] Therefore, much atten-
tion has been devoted to the development of new and ef-
ficient methods for the synthesis of conjugated diynes since
1869.[1a,1d,1e,4] Glaser oxidative coupling of terminal alkynes
has been the main method of preparation of 1,3-diynes for
over 50 years.[1e,4a,5] The Glaser coupling reaction involves
oxidative homocoupling of two terminal alkynes using Cu
salts as reagents or catalysts to produce symmetrical 1,3-
diynes.[6] Current research on the Glaser-type coupling re-
action is mainly focused on modifications of Glaser’s origi-
nal conditions to promote oxidative alkyne–alkyne coupling
more effectively. The homocoupling of terminal alkynes cat-
alyzed by the bimetallic palladium/copper system represents
one of the most attractive ways to synthesize symmetrical
1,3-diynes due to its efficiency and mildness.[7] However,
palladium reagents are expensive and often require air-sen-
sitive and expensive phosphane ligands, and oxidants other
than oxygen or air are required to regenerate the active pal-
ladium species. To avoid the use of expensive palladium cat-
alysts, several methodologies using copper(I) or copper(II)
salts as catalysts have been developed in recent years for the
Although these copper-catalyzed homocouplings of ter-
minal alkynes are highly efficient, the difficulty in separat-
ing the catalyst from the reaction mixture and the impossi-
bility of reusing it in subsequent reactions are disadvantages
of homogeneous catalysis. In addition, homogeneous catal-
ysis might result in unacceptable copper contamination of
the desired isolated product, which is a significant obstacle
to its implementation in the pharmaceutical industry. In
contrast, heterogeneous catalysts can be easily separated
from the reaction mixture by a simple filtration and reused
in successive reactions, provided that the active sites have
not become deactivated. Heterogeneous catalysis also helps
to minimize waste derived from reaction work-up, so con-
tributing to the development of green chemical processes.[10]
From the standpoint of environmentally benign organic
synthesis, the development of immobilized copper catalysts
is challenging and important. In an ideal system, they can
be recovered by simple filtration and reused indefinitely,
and the contamination of products by copper is avoided.
Recently, several copper-based heterogeneous catalytic sys-
tems for the homocoupling of terminal alkynes have been
reported, including CuAl hydrotalcite,[11] copper(I)-modi-
fied zeolites,[8h] Cu(OH)x/TiO2,[8e] and copper nanopar-
ticles.[8k,12] However, these catalytic systems generally suffer
from some drawbacks such as a requirement for a stoichio-
metric amount of TMEDA and copper (110 mol-%),[11]
a
higher reaction temperature (110 °C),[8e,8h] and poor recy-
clability[8h,8k] or a decrease in activity with repeated
uses.[8e,12] Therefore, the development of polymer-supported
copper-complex catalysts having a high activity and excel-
lent recyclability is a topic of enormous importance.
[a] Department of Chemistry, Jiangxi Normal University,
Nanchang 330022, P. R. China
Fax: +86-791-8812-0388
E-mail: caimzhong@163.com
Polymer-supported palladium-complex catalysts have
been used successfully in a variety of carbon–carbon or car-
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200359.
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R. Xiao, R. Yao, M. Cai
FULL PAPER
bon–heteroatom bond-forming reactions;[10d,10e,13] however, The copper content of the catalyst was found to be
polymer-supported copper-complex catalysts for organic 0.45 mmol/g according to the ICP–AES measurements. X-
transformations have received less attention.[14] To the best ray powder diffraction (XRD) analysis of the new MCM-
of our knowledge, no homocoupling of terminal alkynes 41-immobilized copper-complex catalyst (MCM-41–2N-
catalyzed by polymer-supported copper complexes has been CuI) showed, in addition to an intense diffraction peak
reported to date. The development of the mesoporous mate- (100), two higher order peaks (110) and (200) with lower
rial MCM-41 provided a new possible candidate for a solid intensities, indicating that the chemical bonding procedure
support for the immobilization of homogeneous cata- did not reduce the structural ordering of the MCM-41.
lysts.[15] MCM-41 has a regular pore-diameter of ca. 5 nm
In our initial screening experiments to optimize the reac-
and a specific surface area Ͼ700 m2 g–1.[16] Its large pore- tion conditions, the homocoupling reaction of phenylacetyl-
size allows the passage of large molecules such as organic ene was investigated, and the results are summarized in
reactants and metal complexes through the pores to reach Table 1. Oxidative homocoupling of phenylacetylene was
to the surface of the channel.[17] It is generally believed that carried out using MCM-41–2N-CuI (1.0 mol-%) as catalyst
a high surface area of a heterogeneous catalyst results in a in the presence of a base at room temperature in different
high catalytic activity. Considering the fact that the MCM- solvents in air. No oxygen atmosphere, co-oxidants, or addi-
41 support has an extremely high surface area and the cata- tives were utilized. First, the effect of solvent was examined,
lytic copper species would be anchored onto the inner sur- and a significant solvent effect was observed. Good to high
face of the mesopore of MCM-41, we expect that an MCM- yields were obtained when the reaction was performed in
41-supported copper catalyst will exhibit high activity and CH2Cl2, EtOH, or DMF (Table 1, entries 1–3), whereas
good reusability. As part of our continued effort to develop CH3CN, MeOH, and toluene afforded moderate yields
greener synthetic pathways for organic transformations, we (Table 1, entries 4–6), and 1,4-dioxane was ineffective
wish to report herein the synthesis of a new 3-(2-amino- (Table 1, entry 7). Hence, CH2Cl2 was selected as the sol-
ethylamino)propyl-functionalized MCM-41-immobilized vent for subsequent reactions. Our next studies focused on
copper-complex catalyst and to illustrate its application in the effect of base on the model reaction. Among the bases
the homo- and heterocoupling reactions of terminal alkynes examined, piperidine was found to be the most effective
using air as an environmentally friendly co-oxidant.
(Table 1, entry 1). Pyrrolidine and Et2NH also gave good
yields (Table 1, entries 8 and 10), whereas other bases such
as Et3N, pyridine, NaHCO3, K3PO4, K2CO3, Na2CO3, and
NaOAc were ineffective (Table 1, entries 9, 11–16), and
Cs2CO3 was substantially less effective (Table 1, entry 17).
The amount of supported copper catalyst was also scre-
ened, and a 1.0 mol-% loading of copper was found to be
optimal. A lower yield was observed when the amount of
the catalyst was decreased (Table 1, entry 18). Increasing
the amount of copper catalyst shortened the reaction time,
but did not increase the yield of 1,4-diphenylbuta-1,3-diyne
(Table 1, entry 19). Interestingly, the same result was ob-
tained when 10 mol-% piperidine was used as had been seen
with 1 equiv. piperidine (Table 1, entry 20). Thus, the opti-
mized reaction conditions for this homocoupling reaction
are the MCM-41–2N-CuI (1.0 mol-%) in CH2Cl2 using pi-
peridine (10 mol-%) as base at 25 °C in air for 2 h (Table 1,
entry 20).
Results and Discussion
A
new 3-(2-aminoethylamino)propyl-functionalized
MCM-41-immobilized copper complex catalyst (MCM-41–
2N-CuI) was very conveniently synthesized starting from
commercially available and cheap 3-(2-aminoethylamino)-
propyltrimethoxysilane and CuI according to Scheme 1.
First, the MCM-41 support was treated with 3-(2-amino-
ethylamino)propyltrimethoxysilane in toluene at 100 °C for
24 h. This was followed by silylation with Me3SiCl in tolu-
ene at room temperature for 24 h to generate 3-(2-amino-
ethylamino)propyl-functionalized MCM-41 (MCM-41–
2N). Then, MCM-41–2N was treated with CuI in DMF at
room temperature for 7 h to generate the 3-(2-aminoethyl-
amino)propyl-functionalized MCM-41-immobilized copper
complex catalyst (MCM-41–2N-CuI) as a pale blue powder.
Scheme 1. Preparation of the MCM-41–2N-CuI complex.
2
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Oxidative Coupling of Terminal Alkynes
Table 1. Screening of reaction conditions for the homocoupling of (Table 2, entry 12). Alkynes based on propargylic alcohols
phenylacetylene.[a]
also afforded the corresponding symmetrical 1,3-diynes
(i.e., 2m and 2n) in good yields (Table 2, entries 13 and 14).
This demonstrates that the hydroxy group does not exert
any influence on the progress of dimerization. The reaction
Entry
Solvent
Base
Time [h]
Yield [%][b]
of heteroatom-containing alkynes 1o and 1p also proceeded
efficiently under same reaction conditions to give the de-
sired coupled products (i.e., 2o and 2p) in high yields
(Table 2, entries 15 and 16). Propargyl acetate (1q) afforded
1,3-diyne 2q in 89% yield (Table 2, entry 17). It is obvious
that the homocoupling reaction catalyzed by the MCM-41–
2N-CuI complex tolerates several functional groups, includ-
ing hydroxy, fluoro, silyl, methoxy, and ester groups.
1
2
3
4
5
6
7
8
CH2Cl2
EtOH
DMF
piperidine
piperidine
piperidine
piperidine
piperidine
piperidine
piperidine
pyrrolidine
Et3N
2
3
3
5
5
4
24
3
24
3
24
24
24
24
24
24
24
5
94
85
83
76
69
75
trace
84
trace
80
trace
trace
trace
trace
trace
trace
50
CH3CN
toluene
MeOH
1,4-dioxane
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
9
10
11
12
13
14
15
16
17
18[c]
19[d]
20[e]
Et2NH
Table 2. Homocoupling of terminal alkynes catalyzed by MCM-
41–2N-CuI.[a]
pyridine
NaHCO3
K3PO4
K2CO3
Na2CO3
NaOAc
Cs2CO3
Entry
R
Time [h] Product Yield [%][b]
piperidine
piperidine
piperidine
85
1
2
93
94
1
2
3
4
5
6
7
8
Ph (1a)
4-CH3C6H4 (1b)
3-CH3C6H4 (1c)
4-C2H5C6H4 (1d)
4-CH3OC6H4 (1e)
4-FC6H4 (1f)
3-FC6H4 (1g)
n-C4H9 (1h)
n-C6H13 (1i)
2
4
4
7
7
4
3
4
4
4
2
4
3
3
6
5
4
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
2o
2p
2q
94
91
93
89
88
96
98
83
81
88
86
85
78
82
87
90
89
[a] Reaction conditions: phenylacetylene (1.0 mmol), copper cata-
lyst (1.0 mol-%), base (1.0 mmol), solvent (2 mL), air, 25 °C.
[b] Isolated yield. [c] 0.5 mol-% copper catalyst was used.
[d] 2.5 mol-% copper catalyst was used. [e] 10 mol-% piperidine was
used.
9
10
11
12
13
14
15
16
17
CH3OCH2 (1j)
cyclopropyl (1k)
(CH3)3Si (1l)
Having achieved this promising result, we started to in-
vestigate the scope of this reaction under the optimized
conditions. A variety of terminal alkynes were subjected to
homocoupling using 1.0 mol-% MCM-41–2N-CuI and pip-
eridine (0.1 equiv.) at room temperature under aerobic
conditions, and the results are summarized in Table 2. Cata-
lytic oxidative homocoupling of phenylacetylenes 1a–g,
containing electron-donating or electron-withdrawing sub-
stituents, proceeded smoothly to afford the corresponding
symmetrical 1,3-diynes (i.e., 2a–g) in 88–98% yield (Table 2,
entries 1–7). This heterogeneous copper-complex catalyst
1-hydroxycyclohexyl (1m)
HOC(CH3)2 (1n)
thiophen-2-yl (1o)
pyridin-3-yl (1p)
CH3CO2CH2 (1q)
[a] Reaction conditions: terminal alkyne 1 (1.0 mmol), MCM-41–
2N-CuI (1.0 mol-%), piperidine (0.1 mmol), CH2Cl2 (2 mL), air,
25 °C. [b] Isolated yield.
Cadiot–Chodkiewicz coupling and its variants have been
showed a higher catalytic activity than CuI. For example, widely used in the synthesis of unsymmetrical 1,3-diynes.[18]
the oxidative homocoupling of phenylacetylene (1a) in the The heterocoupling reactions of haloalkynes with terminal
presence of only 1 mol-% MCM-41–2N-CuI in CH2Cl2 alkynes catalyzed by palladium are also reported for the
using piperidine (0.1 equiv.) as base at 25 °C in air for 2 h preparation of unsymmetrical 1,3-diynes.[19] Recently, Lei et
gave a 94% yield of homocoupling product 2a (Table 2, en- al. described the synthesis of unsymmetrical 1,3-diynes via
try 1). The same reaction in the presence of CuI (10 mol- the oxidative heterocoupling of two different terminal al-
%) in CH2Cl2 using piperidine (1.0 equiv.) as base at 25 °C kynes catalyzed by NiCl2/CuI.[20] However, the copper-me-
in air for 3 h gave 2a in 91% yield.[8c] It is known that ali- diated oxidative heterocoupling of two different terminal
phatic terminal alkynes are less reactive towards Glaser di- alkynes has received less attention.[8c,8n,9a] The cross-cou-
merization, probably due to the lower acidity of the acetyle- pling of two different terminal alkynes was also investigated
nic protons.[8d,8e,8g] Under the same reaction conditions as using our catalytic system, with an excess amount of one
those used above (Table 2, entries 1–7), the oxidative homo- of the terminal alkyne substrates. Considering the fact that
coupling of aliphatic terminal alkynes such as 1-hexyne separation of heterocoupling products from homocoupling
(1h), 1-octyne (1i), 3-methoxypropyne (1j), and cycloprop- products would be difficult to achieve when two terminal
ylacetylene (1k) proceeded readily to give 1,4-dialkyl-1,3- alkynes of similar polarity were used as substrates, we se-
diynes 2h–k in good yields (Table 2, entries 8–11). 1,4-Bi- lected one nonpolar and another polar terminal alkyne for
s(trimethylsilyl)buta-1,3-diyne (2l) was obtained from the cross-coupling reactions. The scope of terminal alkynes
dimerization of trimethylsilylacetylene (1l) in 85% yield used for the synthesis of unsymmetrical 1,3-diynes was ex-
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plored, and the results are listed in Table 3. Since one of and its reusability. We also investigated the recyclability of
the alkynes was used in excess, the corresponding homocou- the MCM-41–2N-CuI using the homocoupling reaction of
pled 1,3-diynes were isolated in high yields. As shown in 4-fluorophenylacetylene. After carrying out the reaction,
Table 3, all the heterocoupling reactions proceeded the catalyst was separated by simple filtration and washed
smoothly in the presence of 1 mol-% of MCM-41–2N-CuI with diethyl ether. After being air-dried, it was reused di-
under mild conditions, and a variety of unsymmetrical 1,3- rectly without further purification. The recovered copper
diynes were produced in 63–89% yields. An excess amount catalyst was used in the next run, and almost consistent
of phenylacetylene (5 mmol) was successfully cross-coupled activity was observed for 10 consecutive cycles (Table 4, en-
with various terminal alkynes including propargylic tries 1–10). In addition, copper leaching from the supported
alcohols, aliphatic alkynes, and 4-methoxyphenylacetylene catalyst was determined. The copper content of the catalyst
in good to high yields (Table 3, entries 1–4). Substituted was found by ICP analysis to be 0.45 mmol/g after 10 con-
phenylacetylenes (5 mmol) such as 4-fluorophenylacetylene secutive runs, which means that no copper had been lost
and 4-methylphenylacetylene could also be cross-coupled from the MCM-41 support. The high stability and excellent
with aromatic acetylenes or propargylic alcohols in moder- reusability of the catalyst is expected to result from the che-
ate to good yields (Table 3, entries 6 and 7). Excess amounts lating action of the bidentate 2-aminoethylamino ligand on
of cyclopropylacetylene (Table 3, entry 5) and homopropar- copper, and from the mesoporous structure of the MCM-
gyl alcohol (Table 3, entry 8) were treated with aromatic 41 support. The result is important from a practical point
acetylenes to afford the corresponding unsymmetrical 1,3- of view. The high catalytic activity, excellent reusability and
diynes (i.e., 3e and 3h) in moderate yields, respectively. Het- the easy accessibility of the MCM-41–2N-CuI make it a
erocoupling of terminal alkynes catalyzed by the MCM-41– highly attractive heterogeneous copper catalyst for the par-
2N-CuI complex avoids the use of a bimetallic catalysis, allel solution phase synthesis of diverse libraries of com-
such as NiCl2/CuI.[20] Also, it does not suffer from low pounds.
yields as is the case when copper(II) chloride is used.[9a]
This heterogeneous cross-coupling reaction of terminal al-
kynes also tolerates several functional groups, including hy-
Table 4. Homocoupling reaction of 4-fluorophenylacetylene cata-
lyzed by recycled catalyst.[a]
droxy, methoxy, and fluoro groups.
Table 3. Heterocoupling of terminal alkynes catalyzed by MCM-
41–2N-CuI.[a]
Cycle
Yield [%][b]
1
2
3
4
5
6
7
8
9
96
96
95
95
94
95
94
93
94
93
Entry
R1
R2
Time Product
[h]
Yield
[%][b]
1
2
3
4
5
6
7
Ph
Ph
Ph
HOCH2
CH3OCH2CH2
HOC(CH3)2
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
1-hydroxycyclo-
hexyl
6
8
3
8
10
6
3a
3b
3c
3d
3e
3f
85
74
89
75
68
81
68
Ph
cyclopropyl
4-FC6H4
4-CH3C6H4
10
12
3g
[a] Reaction conditions: 4-fluorophenylacetylene (10 mmol),
MCM-41–2N-CuI (0.1 mmol), piperidine (1.0 mmol), CH2Cl2
(20 mL), air, 25 °C, for 4 h. [b] Isolated yield.
8
HOCH2CH2
4-CH3C6H4
7
3h
63
[a] Reaction conditions: R1CϵCH (5.0 mmol), R2CϵCH
(1.0 mmol), MCM-41–2N-CuI (1.0 mol-%), piperidine (3.0 mmol),
CH2Cl2 (5 mL), air, 25 °C. [b] Isolated yield.
Conclusions
In summary, we have successfully developed a novel,
In order to determine whether the catalysis was due to practical, and environmentally friendly catalyst system for
the MCM-41–2N-CuI complex or to a homogeneous cop- the homo- and heterocoupling reactions of terminal alkynes
per complex that is released from the support during the by using
a 3-(2-aminoethylamino)propyl-functionalized
reaction and then returns to the support at the end, we MCM-41-immobilized copper complex as catalyst and air
performed a filtration test on the homocoupling reaction as co-oxidant under mild reaction conditions. The reactions
of phenylacetylene. We filtered off the MCM-41–2N-CuI generated the corresponding symmetrical or unsymmetrical
complex after a reaction time of 0.5 h and allowed the fil- 1,4-disubstituted 1,3-diynes in good to excellent yields and
trate to react further. We found that after this filtration, were applicable to various terminal alkynes. This novel
no further reaction was observed, and no copper could be heterogeneous copper catalyst can be conveniently prepared
detected by ICP–AES in the filtered solution. This result by a simple two-step procedure from commercially available
points to a process of a heterogeneous nature. For a hetero- and cheap reagents, it shows a higher activity than CuI, and
geneous transition metal catalyst, it is important to examine it can be reused at least 10 times without any decrease in
how easily it can be separated, how well it can be recovered, activity. Although high yields of homocoupling products
4
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Oxidative Coupling of Terminal Alkynes
1,4-Diphenylbuta-1,3-diyne (2a): Yield: 0.095 g, 94%. White solid,
m.p. 86–87 °C (ref.[8n] m.p. 88–89 °C). 1H NMR (400 MHz,
CDCl3): δ = 7.54–7.52 (m, 4 H), 7.38–7.32 (m, 6 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 132.51, 129.21, 128.45, 121.81, 81.56,
were achieved using CuI (10 mol-%) as catalyst and piperi-
dine (1.0 equiv.) as base in dichloromethane at 25 °C in
air,[8c] the amount of catalyst used is larger and the homo-
geneous copper catalyst is not recyclable. Some attractive
advantages of our methodology are the low copper loading
(1 mol-%), the use of a catalytic amount of piperidine
(10 mol-%), and the excellent recyclability of the catalyst.
The homo- and heterocoupling reactions of terminal alk-
ynes catalyzed by the MCM-41–2N-CuI complex provide a
better and more practical procedure for the synthesis of a
variety of 1,4-disubstituted 1,3-diynes.
73.91 ppm. IR (KBr): ν = 3050, 2980, 2140, 1570, 920, 753 cm–1.
˜
1,4-Bis(4-methylphenyl)buta-1,3-diyne (2b): Yield: 0.105 g, 91%.
1
White solid, m.p. 183–185 °C (ref.[8n] m.p. 182–183 °C). H NMR
(400 MHz, CDCl3): δ = 7.42 (d, J = 8.0 Hz, 4 H), 7.14 (d, J =
8.0 Hz, 4 H), 2.36 (s, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 139.49, 132.39, 129.21, 118.80, 81.54, 73.44, 21.62 ppm. IR
(KBr): ν = 3052, 2990, 2130, 1502, 1265, 802 cm–1.
˜
1,4-Bis(3-methylphenyl)buta-1,3-diyne (2c): Yield: 0.107 g, 93%.
White solid, m.p. 75–76 °C (ref.[7a] m.p. 74–75 °C). 1H NMR
(400 MHz, CDCl3): δ = 7.33 (d, J = 8.0 Hz, 2 H), 7.24–7.16 (m, 6
H), 2.34 (s, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 138.17,
132.99, 130.12, 129.62, 128.33, 121.66, 81.62, 73.65, 21.21 ppm. IR
Experimental Section
General: All chemicals were reagent grade and were used as pur-
chased. All solvents were dried and distilled before use. The prod-
ucts were purified by flash chromatography on silica gel. A mixture
of EtOAc and hexane was generally used as eluent. All coupled
products were characterized by comparison of their spectra and
physical data with authentic samples. IR spectra were recorded
with a Perkin–Elmer 683 instrument. 1H NMR spectra were re-
corded with a Bruker Avance (400 MHz) spectrometer in CDCl3 as
solvent, with TMS as an internal standard. 13C NMR spectra were
recorded with a Bruker Avance (100 MHz) spectrometer in CDCl3
as solvent. Copper content was determined using an Atomscan16
inductively coupled plasma atomic emission spectrometer (ICP–
AES, TJA Corporation). X-ray powder diffraction data was ob-
tained with a Damx-rA (Rigaka) instrument. Microanalyses were
measured using a Yanaco MT-3 CHN microelemental analyzer.
The mesoporous material MCM-41 was easily prepared according
to a literature procedure.[21]
(KBr): ν = 3052, 2918, 2142, 1502, 1265, 802, 785 cm–1.
˜
1,4-Bis(4-ethylphenyl)buta-1,3-diyne (2d): Yield: 0.115 g, 89%.
White solid, m.p. 97–98 °C (ref.[8d] m.p. 97–98 °C). 1H NMR
(400 MHz, CDCl3): δ = 7.44 (d, J = 8.4 Hz, 4 H), 7.17 (d, J =
8.0 Hz, 4 H), 2.66 (q, J = 7.6 Hz, 4 H), 1.23 (t, J = 7.6 Hz, 6 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 145.75, 132.49, 128.03,
119.00, 81.55, 73.42, 28.92, 15.26 ppm. IR (KBr): ν = 2960, 2930,
˜
1650, 1430, 820 cm–1.
1,4-Bis(4-methoxyphenyl)buta-1,3-diyne (2e): Yield: 0.115 g, 88%.
1
White solid, m.p. 143–144 °C (ref.[8n] m.p. 140–141 °C). H NMR
(400 MHz, CDCl3): δ = 7.46 (d, J = 8.4 Hz, 4 H), 6.85 (d, J =
8.4 Hz, 4 H), 3.82 (s, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 160.26, 134.04, 114.15, 113.98, 81.23, 72.97, 55.34 ppm. IR
(KBr): ν = 3055, 2980, 2140, 1585, 1560, 1250, 1220, 1140, 1058,
˜
840, 798 cm–1.
Synthesis of 3-(2-Aminoethylamino)propyl-functionalized MCM-41-
Immobilized Copper Complex (MCM-41–2N-CuI): A solution of 3-
(2-aminoethylamino)propyltrimethoxysilane (1.54 g, 6.94 mmol) in
dry chloroform (18 mL) was added to a suspension of MCM-41
(2.2 g) in dry toluene (180 mL). The mixture was stirred for 24 h
at 100 °C. The solid was filtered and washed with CHCl3
(2ϫ20 mL) and then dried in vacuo at 160 °C for 5 h. The dried
white solid was then soaked in a solution of Me3SiCl (3.1 g,
28.57 mmol) in dry toluene (100 mL) at room temperature whilst
stirring for 24 h. Then the solid was filtered, washed with acetone
(3ϫ20 mL) and diethyl ether (3ϫ20 mL), and dried in vacuo at
120 °C for 5 h to obtain hybrid material MCM-41–2N (3.49 g). The
nitrogen content was found to be 1.84 mmol/g by elemental analy-
sis.
1,4-Bis(4-fluorophenyl)buta-1,3-diyne (2f): Yield: 0.114 g, 96%.
1
White solid, m.p. 192–193 °C (ref.[8n] m.p. 194–195 °C). H NMR
(400 MHz, CDCl3): δ = 7.53–7.50 (m, 4 H), 7.06–7.02 (m, 4 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 163.05 (d, 1JCF = 250 Hz),
3
4
2
134.54 (d, JCF = 8 Hz), 117.80 (d, JCF = 4 Hz), 115.92 (d, JCF
= 23 Hz), 80.41, 73.53 ppm. IR (KBr): ν = 2344, 1594, 1499, 1215,
˜
1157, 1093, 824, 695 cm–1.
1,4-Bis(3-fluorophenyl)buta-1,3-diyne (2g): Yield: 0.117 g, 98%.
White solid,[8l] m.p. 121–122 °C. 1H NMR (400 MHz, CDCl3): δ =
7.33–7.31 (m, 4 H), 7.26–7.21 (m, 2 H), 7.12–7.07 (m, 2 H) ppm.
1
13C NMR (100 MHz, CDCl3): δ = 162.26 (d, JCF = 245 Hz),
3
4
3
130.15 (d, JCF = 8 Hz), 128.49 (d, JCF = 3 Hz), 123.36 (d, JCF
= 10 Hz), 119.24 (d, 2JCF = 23 Hz), 116.93 (d, 2JCF = 21 Hz), 80.63
In a small Schlenk tube, the above-functionalized MCM-41
(MCM-41–2N; 1.0 g) was mixed with CuI (0.1 g, 0.52 mmol) in dry
DMF (10 mL). The mixture was stirred at room temperature for
7 h under an argon atmosphere. The solid product was filtered by
suction, washed with DMF and acetone, and dried at 40 °C/26.7 Pa
under Ar for 5 h to give a pale blue copper complex (MCM-41–
2N-CuI; 1.066 g). The nitrogen and copper contents were found to
be 1.67 and 0.45 mmol/g, respectively.
(d, 4JCF = 3 Hz), 74.41 ppm. IR (KBr): ν = 2345, 1604, 1499, 1215,
˜
1157, 1093, 824, 675 cm–1.
Dodeca-5,7-diyne (2h): Yield: 0.067 g, 83%. Light yellow oil.[8c] 1
H
NMR (400 MHz, CDCl3): δ = 2.25 (t, J = 6.8 Hz, 4 H), 1.55–1.48
(m, 4 H), 1.47–1.38 (m, 4 H), 0.90 (t, J = 7.2 Hz, 6 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 77.49, 65.25, 30.40, 21.93, 18.90,
13.54 ppm. IR (neat): ν = 2929, 2858, 1458, 1322, 725 cm–1.
˜
Typical Procedure for the Homocoupling Reaction of Terminal
Alkynes: A mixture of terminal alkyne 1 (1 mmol), piperidine
(1 mmol), and MCM-41–2N-CuI (1 mol-%) in CH2Cl2 (2 mL) was
stirred open to atmospheric air at 25 °C with TLC monitoring for
2–7 h. The mixture was then diluted with dichloromethane and fil-
tered. The catalyst was washed with diethyl ether (2ϫ5 mL) and
reused in the next run. The filtrate was concentrated in vacuo, and
the residue was purified by column chromatography (silica gel, hex-
ane/ethyl acetate) to afford coupled products 2.
Hexadeca-7,9-diyne (2i): Yield: 0.088 g, 81%. Light yellow oil.[8n]
1H NMR (400 MHz, CDCl3): δ = 2.24 (t, J = 6.8 Hz, 4 H), 1.53–
1.48 (m, 4 H), 1.40–1.35 (m, 4 H), 1.34–1.26 (m, 8 H), 0.89 (t, J =
6.4 Hz, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 77.52, 65.27,
31.30, 28.53, 28.33, 22.50, 19.21, 14.01 ppm. IR (neat): ν = 2929,
˜
2858, 1458, 1322, 725 cm–1.
1,6-Dimethoxyhexa-2,4-diyne (2j): Yield: 0.061 g, 88%. Light yel-
low oil.[22] 1H NMR (400 MHz, CDCl3): δ = 4.18 (s, 4 H), 3.40 (s,
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5

Job/Unit: O20359
/KAP1
Date: 12-06-12 18:14:06
Pages: 8
R. Xiao, R. Yao, M. Cai
FULL PAPER
6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 75.19, 70.47, 60.13,
128.94, 128.35, 121.90, 81.14, 75.16, 74.15, 70.20, 66.04, 58.79,
57.85 ppm. IR (neat): ν = 2994, 2825, 2255, 1450, 903 cm–1.
20.88 ppm. IR (neat): ν = 2928, 2246, 1595, 1490, 1442, 1185, 999,
˜
˜
755, 689 cm–1. C13H12O (184.24): calcd. C 84.75, H 6.57; found C
84.47, H 6.42.
1,4-Dicyclopropylbuta-1,3-diyne (2k): Yield: 0.056 g, 86%. Color-
less oil.[8n] 1H NMR (400 MHz, CDCl3): δ = 1.31–1.25 (m, 2 H),
0.82–0.72 (m, 8 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 80.01,
2-Methyl-6-phenylhexa-3,5-diyn-2-ol (3c): Yield: 0.164 g, 89%.
White solid,[8c] m.p. 59–61 °C. 1H NMR (400 MHz, CDCl3): δ =
7.48 (d, J = 7.2 Hz, 2 H), 7.37–7.32 (m, 3 H), 2.08 (s, 1 H), 1.58
(s, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 132.52, 129.26,
128.43, 121.51, 86.67, 78.79, 73.12, 67.05, 65.76, 31.11 ppm. IR
60.79, 8.69, 0.00 ppm. IR (neat): ν = 3094, 3012, 2157, 1425, 1185,
˜
938 cm–1.
1,4-Bis(trimethylsilyl)-1,3-butadiyne (2l): Yield: 0.083 g, 85%.
1
White solid, m.p. 110–112 °C (ref.[11] m.p. 110–113 °C). H NMR
(KBr): ν = 3428, 2981, 2446, 1642, 1570, 1165, 954, 860, 757 cm–1.
˜
(400 MHz, CDCl3): δ = 0.00 (s, 18 H) ppm. 13C NMR (100 MHz,
1-Methoxy-4-(phenylbuta-1,3-diynyl)benzene (3d): Yield: 0.174 g,
75%. White solid, m.p. 97–98 °C (ref.[8n] m.p. 95–96 °C). 1H NMR
(400 MHz, CDCl3): δ = 7.53–7.50 (m, 3 H), 7.47 (d, J = 8.0 Hz, 2
H), 7.33 (d, J = 8.0 Hz, 2 H), 6.85 (d, J = 8.0 Hz, 2 H), 3.81 (s, 3
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 160.40, 134.16, 132.46,
129.06, 128.45, 122.03, 114.19, 113.71, 81.87, 81.06, 74.22, 72.78,
CDCl ): δ = 87.81, 85.66, –0.70 ppm. IR (KBr): ν = 2942, 1731,
˜
3
1599, 1425, 1367, 1259, 1087, 924, 708, 683 cm–1.
1,4-Bis(1-hydroxycyclohexyl)buta-1,3-diyne (2m): Yield: 0.096 g,
78%. White solid, m.p. 174–175 °C (ref.[8n] m.p. 178–179 °C). 1H
NMR (400 MHz, [D6]DMSO): δ = 5.56 (s, 2 H), 1.73–1.21 (m, 20
H) ppm. 13C NMR (100 MHz, [D6]DMSO): δ = 85.07, 67.52,
55.36 ppm. IR (KBr): ν = 3129, 2991, 2217, 1599, 1567, 1507, 1069,
˜
67.43, 39.69, 25.14, 22.99 ppm. IR (KBr): ν = 3240, 2850, 1420,
˜
954 cm–1.
1312, 1250, 1068, 950 cm–1.
1-Methoxy-4-(cyclopropylbuta-1,3-diynyl)benzene
(3e):
Yield:
0.133 g, 68%. Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 7.40
(d, J = 8.0 Hz, 2 H), 6.81 (d, J = 8.0 Hz, 2 H), 3.80 (s, 3 H),
1.43–1.36 (m, 1 H), 0.89–0.81 (m, 4 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 160.04, 134.09, 114.06, 87.17, 74.32, 73.34, 60.59,
2,7-Dimethylocta-3,5-diyne-2,7-diol (2n): Yield: 0.068 g, 82%.
1
White solid, m.p. 132–134 °C (ref.[8n] m.p. 131–132 °C). H NMR
(400 MHz, CDCl3): δ = 2.02 (s, 2 H), 1.54 (s, 12 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 84.05, 66.38, 65.60, 31.08 ppm. IR (KBr):
ν = 3220, 2982, 2514, 2256, 1685, 1449, 1364, 1211, 1170, 954, 889,
˜
55.31, 9.02, 0.39 ppm. IR (neat): ν = 3094, 2958, 2838, 2539, 2148,
˜
732 cm–1.
1603, 1567, 1509, 1425, 1185, 938 cm–1. C14H12O (196.25): C 85.68,
H 6.16; found C 85.44, H 6.32.
1,4-Bis(thiophen-2-yl)buta-1,3-diyne (2o): Yield: 0.093 g, 87%.
White solid, m.p. 91–92 °C (ref.[8n] m.p. 92–93 °C). 1H NMR
(400 MHz, CDCl3): δ = 7.31–7.24 (m, 4 H), 7.02–7.00 (m, 2 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 132.14, 127.66, 127.19,
1-Methoxy-4-(4-fluorophenylbuta-1,3-diynyl)benzene (3f): Yield:
0.203 g, 81%. White solid,[23] m.p. 122–124 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.51–7.45 (m, 4 H), 7.02 (d, J = 8.4 Hz, 2
H), 6.85 (d, J = 8.8 Hz, 2 H), 3.81 (s, 3 H) ppm. 13C NMR
122.93, 86.23 ppm. IR (KBr): ν = 3116, 1817, 1416, 843, 710 cm–1.
˜
1
(100 MHz, CDCl3): δ = 162.93 (d, JCF = 250 Hz), 160.45, 134.44
1,4-Bis(pyridin-3-yl)buta-1,3-diyne (2p): Yield: 0.092 g, 90%. White
solid, m.p. 145–146 °C (ref.[8n] m.p. 144–146 °C). 1H NMR
(400 MHz, CDCl3): δ = 8.78 (s, 2 H), 8.61 (d, J = 4.4 Hz, 2 H),
7.84 (d, J = 8.0 Hz, 2 H), 7.32 (t, J = 4.8 Hz, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 153.05, 149.41, 139.52, 123.17, 118.91,
3
4
2
(d, JCF = 8 Hz), 134.15, 118.17 (d, JCF = 3 Hz), 115.85 (d, JCF
= 22 Hz), 114.20, 113.61, 81.84, 79.93, 74.00, 72.61, 55.34 ppm.
IR (KBr): ν = 3409, 2961, 2208, 1617, 1502, 1293, 1251, 1069,
˜
954 cm–1.
79.15 ppm. IR (KBr): ν = 2151, 1638, 1579, 1413, 1022, 804,
˜
1-(p-Tolylbuta-1,3-diynyl)cyclohexan-1-ol (3g): Yield: 0.162 g, 68%.
White solid,[24] m.p. 57–59 °C. 1H NMR (400 MHz, [D6]DMSO):
δ = 7.62 (d, J = 8.0 Hz, 2 H), 7.39 (d, J = 8.0 Hz, 2 H), 5.83 (s, 1
H), 2.50 (s, 3 H), 1.98–1.39 (m, 10 H) ppm. 13C NMR (100 MHz,
[D6]DMSO): δ = 140.19, 132.71, 129.91, 118.06, 88.99, 78.45,
699 cm–1.
Hexa-2,4-diyne-1,6-diyl Diacetate (2q): Yield: 0.086 g, 89%. Color-
less oil.[8n] 1H NMR (400 MHz, CDCl3): δ = 4.74 (s, 4 H), 2.11 (s,
6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 169.91, 73.60, 70.18,
73.46, 67.73, 67.63, 39.70, 25.17, 23.03, 21.57 ppm. IR (KBr): ν =
˜
52.14, 20.53 ppm. IR (neat): ν = 2149, 1778, 1427, 828, 730 cm–1.
˜
3421, 2930, 2342, 1640, 1564, 1255, 1120, 967, 768, 619 cm–1.
Typical Procedure for the Heterocoupling Reaction of Two Different
Terminal Alkynes: A mixture of R1CϵCH (5 mmol), R2CϵCH
(1 mmol), piperidine (3 mmol), and MCM-41–2N-CuI (1 mol-%)
in CH2Cl2 (5 mL) was stirred open to atmospheric air at 25 °C
with TLC monitoring for 3–12 h. The mixture was diluted with
dichloromethane and filtered. The catalyst was washed with diethyl
ether (2ϫ5 mL) and reused in the next run. The filtrate was con-
centrated in vacuo, and the residue was purified by column
chromatography (silica gel, hexane/ethyl acetate) to afford cross-
coupled products 3.
6-Tolylhexa-3,5-diyn-1-ol (3h): Yield: 0.116 g, 63%. Colorless oil.
1H NMR (400 MHz, CDCl3): δ = 7.30 (d, J = 8.0 Hz, 2 H), 7.04
(d, J = 8.0 Hz, 2 H), 3.72 (t, J = 6.2 Hz, 2 H), 2.57 (t, J = 6.2 Hz,
2 H), 2.28 (s, 3 H), 1.80 (s, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 139.43, 132.47, 129.18, 118.60, 80.58, 75.68, 73.31,
67.01, 60.83, 24.03, 21.60 ppm. IR (neat): ν = 3352, 3030, 2924,
˜
2246, 1605, 1508, 1415, 1045, 908 cm–1. C13H12O (184.24): calcd.
C 84.75, H 6.57; found C 84.54, H 6.31.
Supporting Information (see footnote on the first page of this arti-
cle): 1H NMR and 13C NMR spectra of compounds 2a–q and
3a–h.
5-Phenylpenta-2,4-diyn-1-ol (3a): Yield: 0.133 g, 85%. Colorless
oil.[8n] 1H NMR (400 MHz, CDCl3): δ = 7.48 (d, J = 7.2 Hz, 2 H),
7.36–7.29 (m, 3 H), 4.41 (s, 2 H), 1.87 (s, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 132.61, 129.37, 128.44, 121.35, 80.49,
Acknowledgments
We thank the National Natural Science Foundation of China (Pro-
ject No. 20862008) and the Natural Science Foundation of Jiangxi
Province in China (2010GZH0062) for financial support.
78.56, 73.19, 70.39, 51.61 ppm. IR (neat): ν = 3350, 2927, 2869,
˜
1721, 1678, 1447, 1284, 753 cm–1.
(6-Methoxyhexa-1,3-diynyl)benzene (3b): Yield: 0.136 g, 74%. Col-
orless oil. 1H NMR (400 MHz, CDCl3): δ = 7.48–7.46 (m, 2 H),
7.32–7.26 (m, 3 H), 3.56 (t, J = 6.0 Hz, 2 H), 3.39 (s, 3 H), 2.64 (t,
J = 6.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 132.53,
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: March 21, 2012
Published Online: ᭿
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7

Job/Unit: O20359
/KAP1
Date: 12-06-12 18:14:06
Pages: 8
R. Xiao, R. Yao, M. Cai
FULL PAPER
Coupling of Terminal Alkynes
R. Xiao, R. Yao, M. Cai* ................. 1–8
Practical Oxidative Homo- and Heterocou-
pling of Terminal Alkynes Catalyzed by
Immobilized Copper in MCM-41
Keywords: 1,3-Diynes / Supported cata-
lysts / Copper / C–C coupling / Hetero-
geneous catalysis
A practical oxidative homo- and hetero-
coupling of terminal alkynes was achieved
in CH2Cl2 at 25 °C by using a 3-(2-amino-
ethylamino)propyl-functionalized MCM-
41-immobilized copper(I) complex (MCM-
41–2N-CuI, 1 mol-%) as the catalyst and
air as the environmentally friendly oxidant,
yielding a variety of symmetrical and un-
symmetrical 1,4-disubstituted 1,3-diynes in
good to excellent yields.
8
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Eur. J. Org. Chem. 0000, 0–0