Homo and heterocoupling of terminal alkynes using catalytic CuCl 2 and DBU

Article abstract of DOI:10.1071/CH11080

Homocoupling of terminal alkynes has been efficiently achieved using catalytic amounts of CuCl2 and DBU. This methodology could be extended to couple two different terminal alkynes together by taking one of the alkyne partners, preferably the electron rich alkyne, in five fold excess than the other. CSIRO 2011.

Full text of DOI:10.1071/CH11080

RESEARCH FRONT
Full Paper
CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2011, 64, 567–575
Homo and Heterocoupling of Terminal Alkynes
Using Catalytic CuCl2 and DBU
A B
,
A
Rengarajan Balamurugan,
Naganaboina Naveen,
A
A
Seetharaman Manojveer, and Masthan Vali Nama
A
School of Chemistry, University of Hyderabad, Gachibowli, Hyderabad 500046, India.
Corresponding author. Email: rbsc@uohyd.ernet.in
B
Homocoupling of terminal alkynes has been efficiently achieved using catalytic amounts of CuCl2 and DBU. This
methodology could be extended to couple two different terminal alkynes together by taking one of the alkyne partners,
preferably the electron rich alkyne, in five fold excess than the other.
Manuscript received: 17 February 2011.
Manuscript accepted: 5 April 2011.
Introduction
catalytic system in alkyne heterocoupling. For the reaction
screening, phenylacetylene was chosen as the substrate. The
homocoupling of phenylacetylene was studied with CuCl2 in
tetrahydrofuran (THF) using different bases. It was found that,
among the bases studied, 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) worked well to effect the 1,3-diyne 2a formation, 1,4-
diazabicyclo[2.2.2]octane (DABCO) being slightly less effect-
ive. The outcome of the base screening is given in Table 1. It is
important to note that DBU was reported to be the best base in a
study to evaluate the influence of bases in the CuI-catalyzed
homocoupling of terminal alkynes.[9a] From electrochemical
studies, Fontaine et al. have shown that there is poor stabiliza-
tion of the CuII state in the CuII/CuI redox established in
the complex formed between CuBr2 and DBU.[19] Perhaps the
stabilized CuI state, which is required to form the alkynyl copper
species, could be one of the reasons for the better efficiency of
DBU. Furthermore, alkynyl copper species can undergo facile
oxidation to an alkynyl radical by CuII, which reduces itself
to CuI. This might also facilitate the reaction in the presence
of DBU.
Next we studied the effect of solvents in the CuCl2/DBU
catalyzed dimerization of phenylacetylene (Table 2). For these
reactions 10 mol-% of CuCl2 and 1.2 equiv. of DBU were used
in different solvents with a wide range of polarities. Among the
solvents studied, toluene and THF worked very well. A slightly
higher yield of 2a was noticed in the reaction that was carried
out in THF. Nitromethane and methanol resulted in very poor
yields. Hence the system CuCl2 (10 mol-%)/DBU (1.2 equiv.)
in THF was chosen for the study of substrate scope.
Coupling of terminal alkynes is a straight forward route to
make 1,3-diynes.[1] Glaser,[2] Eglington,[3] and Hay[4] coupling
methods are the classical protocols to make homocoupled 1,3-
diynes. Considering the presence of conjugated CꢀC units
in useful oligomers/polymers,[5] natural and bioactive com-
pounds,[6] materials having non-linear optical properties,[7]
and molecular recognition properties,[8] several variants of
the above mentioned methods have been developed in recent
years.[9] Palladium catalysts have been employed in combina-
tion with CuI salts to perform the alkyne homocoupling reac-
tions. In this way the efficiency of the coupling is enhanced
at the cost of expensive Pd catalysts.[10] In recent years, solid-
supported heterogeneous catalysts have been developed for the
same task.[11] Apart from copper salts, catalysts based on other
transition metals such as Ti,[12] Co,[13] and Ni[14] have also been
employed in alkyne homocoupling. An iron catalyst has also
been used, however, in combination with a Cu salt.[15] Hetero-
coupling of terminal alkynes are typically achieved using a
Cadiot–Chodkiewicz procedure, which requires a haloalkyne
along with a terminal alkyne.[16] There are a few reports on
palladium catalyzed alkyne heterocoupling as well.[17] Coupling
of two different terminal alkynes is a more simple way to obtain
differentially substituted 1,3-diynes. NiCl2 in combination with
CuI has been found to catalyze this transformation.[17d] We
focused on developing a CuII-based catalytic system to effect the
alkyne heterocoupling as CuII salts are comparatively cheaper
and easier to handle than CuI salts. We chose CuCl2 as the
catalyst and studied the homo and heterocouplings of terminal
alkynes. While our study was in progress, alkyne heterocoupling
using catalytic systems such as Fe(acac)3/Cu(acac)2/K2CO3
(acac ¼ acetylacetonate),[15] CuCl2/Et3N,[9g] and Cu(OAc)2/
piperidine[9h] appeared in the literature. Very recently transition-
metal-free homo and heterocoupling of a 1-haloalkyne using KI
was reported.[18]
A wide range of terminal alkynes were subjected to homo-
coupling using CuCl2/DBU in THF system. The results are
presented in Table 3. The substrates include substituted aryl,
heteroaryl, alkyl, and hydroxyalkyl alkynes. All the substrates
underwent smooth dimerization resulting in yields ranging from
good to excellent. The reactions do not require bubbling of air
through the reaction mixture and could be carried out in an open
flask at room temperature. The yields of the products were
comparable and in some cases greater than those obtained in
reported systems. Aryl alkynes having substituents such as Cl,
Results and Discussion
At the outset, we studied the CuCl2-catalyzed homocoupling of
terminal alkynes with the intention of employing the optimized
Ó CSIRO 2011
10.1071/CH11080
0004-9425/11/050567

RESEARCH FRONT
568
R. Balamurugan et al.
Table 1. Influence of bases in the CuCl2-catalyzed dimerization of phenylacetylene
(THF: tetrahydrofuran, TMEDA: N,N,N0,N0-tetramethylethylenediamine, DABCO: 1,4-diazabicyclo[2.2.2]octane,
DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene)
CuCl2, base
2
THF, r.t.
1a
2a
Entry
Base
Equiv.
CuCl2 [mol-%]
Time
Isolated yield [%]
1
2
3
4
5
6
7
8
9
10
Et3N
1.5
1.5
1.5
1.0
1.0
1.5
1.2
1.0
5
10
10
10
10
5
24
24
24
24
24
24
24
24
24
24
82
42
90
88
51
90
92
82
80
20
TMEDA
DABCO
DABCO
DABCO
DBU
10
10
5
DBU
DBU
DBU
5
DBU
10
5
heterocoupled product. Only a slight improvement of yield
was noticed when 20 mol-% of CuCl2 was used (entry 9).
The scope of CuCl2-catalyzed heterocoupling using DBU
as a base was tested with different pairs of terminal alkynes. In
these reactions one of the alkynes was used in five-fold excess of
the other. The reactions were carried out at room temperature
under an air-filled balloon. Although the role of oxygen in this
reaction is not very clear, it can be proposed that it is needed to
oxidize the CuI species which will be formed after the initial
Eglinton coupling using CuII present in a catalytic amount.
Furthermore, the thus formed CuI may form an acetylide with a
terminal alkyne which will require oxygen to give the 1,3-diyne
by oxidative coupling. The outcome of different coupling
reactions are presented in Table 5. All of the reactions were
carried out for 24 h except for the reactions presented in entries
14–19, which were carried out for 48 h. The reactions between
an aryl alkyne with an aliphatic alkyne underwent smooth
coupling to yield unsymmetrically substituted 1,3-diynes in good
yields. Substituted 1,3-diynes with Br and NH2 on one aryl ring
could also be made with out any difficulties (entries 8, 9, 11, 12,
17, and 18, Table 5). These functional groups can be utilized for
further synthetic elaborations using transition-metal-catalyzed
coupling methods. Even two different aryl alkynes could also
be coupled in moderate efficiencies (entries 14–18, Table 5).
Selected reactions were repeated by taking the coupling partners
in exactly opposite molar ratios. The results are presented in
Table 5 (entries 2 and 3, 6 and 7, 14 and 15, and 17 and 18).
From these experiments it is clear that the results are not a result
of strategic choice of alkyne used in excess. However, it
indicates that the yields are higher when the electron-rich alkyne
is used in excess, i.e., five equivalents. Some of the products
obtained have been reported as precursors for making useful
products. For example, compound 16 could be converted into
indoles.[20] Compounds 3 and 6 are known to act as precursors
for generating dialkynyl carbenes.[21]
Table 2. Effect of solvent in the CuCl2/diazabicyclo[5.4.0]undec-7-ene
(DBU) catalyzed dimerization of phenylacetylene
(DCE:1,2-dichloroethane, DMF:N,N-dimethylformamide, DMSO: dimethyl
sulfoxide, THF: tetrahydrofuran)
Entry
Solvent
Isolated yield [%]
1
CH2Cl2
CH3NO2
DCE
28
19
78
79
46
66
69
90
92
85
12
2
3
4
DMF
5
DMSO
Acetone
Hexane
Toluene
THF
6
7
8
9
10
11
CH3CN
CH3OH
Br, OMe, and NH2 tolerate the reaction conditions. Aliphatic
alkynes having a tertiary alcohol function resulted in good yields
(entries 15 and 16, Table 3). However, the yield with simple
oct-1-yne was poor (entry 20, Table 3).
Differentially substituted 1,3-diynes are useful building
blocks to make interesting molecular structures. Only a few
reports are available for the alkyne heterocoupling.[9g–i,15,17d,18]
Hence the applicability of the catalytic system CuCl2/DBU
was tested in alkyne heterocoupling. With this intention, the
coupling of phenylacetylene (1a) with equimolar propargyl
alcohol (1s) was studied using CuCl2/DBU in THF. The reaction
resulted in all three possible coupled products 3, 2a, and 2s
(Table 4). The heterocoupled product 3 was obtained only in
38% yield. It improved to 45% when three equivalents of
phenylacetylene with respect to propargyl alcohol were used.
However, when the reaction was carried out under an air-filled
balloon the yield increased significantly to 61% (entry 3,
Table 4). A similar trend was observed when propargyl alcohol
was used in a three-fold excess of phenylacetylene (entries 4
and 5, Table 4). The highest yield was obtained when five
equivalents of propargyl alcohol was used with respect to
phenylacetylene. Reactions carried out under reflux (entry 7)
and sonication (entry 8) did not improve the yield of the
Conclusion
We described a simple protocol for making symmetrically and
unsymmetrically substituted 1,3-diynes using catalytic CuCl2.
DBU was found to be the base of choice. The scope of the homo
and heterocoupling was shown with a wide range of terminal

RESEARCH FRONT
Homo and Heterocoupling of Terminal Alkynes
569
Table 3. Results of homocoupling of different terminal alkynes using CuCl2/diazabicyclo[5.4.0]undec-7-ene (DBU) in tetrahydrofuranA
Entry
1
Alkyne
Product
YieldB [%]
92
1a
2a
NH2
NH2
Br
H2N
Br
83
96
1b
2
3
2b
Br
1c
2c
2d
Cl
Cl
Cl
Cl
4
5
95
65
1d
Cl
Cl
1e
2e
2f
6
84
1f
7
8
99
98
1g
2g
2h
1h
OMe
OMe
MeO
9
72
70
1i
2i
MeO
OMe
MeO
10
1j
2j
MeO
MeO
OMe
11
12
84
76
1k
2k
1l
2l
13
91
MeO
MeO
OMe
1m
2m
14
15
55
98
1n
N
N
N
2n
2o
HO
HO
OH
1o
OH
HO
OH
16
90
1p
2p
(Continued)

RESEARCH FRONT
570
R. Balamurugan et al.
Table 3. (Continued)
Entry
17
Alkyne
BnO
Product
YieldB [%]
70
BnO
OBn
1q
2q
18
19
88
68
1r
2r
HO
HO
OH
1s
2s
H3C (CH2)5
H3C (CH2)5
(CH2)5
CH3
20
55
1t
2t
AAll the reactions were carried out with anhydrous CuCl2 (10 mol-%) and DBU (1.2 equiv.) in tetrahydrofuran for 24 h under open atmosphere.
BIsolated yield.
Table 4. Heterocoupling of phenylacetylene with propargyl alcohol at different molar ratios
(DBU: diazabicyclo[5.4.0]undec-7-ene, THF: tetrahydrofuran)
OH
CuCl2 (10 mol-%)
OH
ϩ
2a
2s
ϩ
ϩ
DBU (1.2 equiv.), THF
r.t., 24h
1a
1s
3
Entry
1a
(equiv.)
1s
(equiv.)
CuCl2
[mol-%]
DBU
(equiv.)
YieldC [%]
3
2a
2s
1A
1
3
3
1
1
1
1
1
1
1
1
1
3
3
5
5
5
5
10
10
10
10
10
10
10
10
20
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
38
40
69
39
21
22
20
13
17
17
18
18
12
21
15
18
15
37
18
2A
45
61
44
63
65
17
37
70
3B
4A
5B
6B
7B,D
8B,E
9B
AThe reactions were carried out in an open flask.
BThe reactions were carried out under an air-filled balloon.
CIsolated yield.
DReaction was carried out at reflux.
EReaction was carried out under sonication.
alkynes. The unsymmetrically substituted 1,3-diynes could
serve as important building blocks.
General Experimental Procedure for the CuCl2-Catalyzed
Homocoupling of Alkynes
To a solution of terminal alkyne 1a (100 mg, 0.98 mmol) in THF
(5 mL), CuCl2 (13 mg, 0.098 mmol) was added and the mixture
was allowed to stir at room temperature for 10 min. DBU
(179 mg, 1.176 mmol) was added to the reaction mixture which
was allowed to stir vigorously at room temperature open to the
atmosphere. After 24 h the reaction mixture was concentrated
under reduced pressure and the residue was purified by column
chromatography on silica gel using hexanes/ethyl acetate as
eluent to obtain pure 2a (92 mg, 92%).
Experimental
1H and 13C spectra were recorded on a Bruker Avance
400 MHz spectrometer at 400 MHz and 100 MHz, respec-
tively, using solutions in CDCl3 with tetramethylsilane
(TMS) as an internal standard. IR spectra were recorded on
an FT-IR spectrometer. Elemental (C, H, N) analysis were
performed by a flash combustion method in a THERMO
FINNIGAN FLASH EA 1112 CHN analyzer. Column chro-
matography was performed on a silica gel column (100–200
mesh), using a mixture of ethyl acetate and hexane as eluent.
Most of the starting materials were prepared by following
known and standard literature procedures. Freshly distilled
THF was used.
Same procedure was followed to prepare the diynes 2b–2t.
1,4-Diphenylbuta-1,3-diyne (2a)[9a]
dH 7.52–7.50 (m, 4H), 7.37–7.29 (m, 6H). dC 132.43, 129.15,
128.38, 121.71, 81.52, 73.90.

RESEARCH FRONT
Homo and Heterocoupling of Terminal Alkynes
571
Table 5. Scope of CuCl2/DBU system in alkyne heterocoupling
(DBU: diazabicyclo[5.4.0]undec-7-ene, THF: tetrahydrofuran)
OH
CuCl2 (10 mol-%)
OH
ϩ
2a
2s
ϩ
ϩ
DBU (1.2 equiv.), THF
r.t., 24h
1a
1s
3
A
B
Entry
1
Product
YieldC [%]
65
HO
OH
1s
1a
3
BnO
OBn
2
72
1a
1q
4
BnO
OBn
OH
3
4
43
74
1a
1q
4
HO
1o
1a
5
HO
OH
5
6
7
58
51
61
1g
1s
6
HO
BnO
HO
HO
OBn
OBn
1s
7
7
1q
BnO
HO
1s
1q
Br
Br
Br
HO
OH
8
9
62
55
1o
1c
Br
8
9
HO
OH
OH
1s
1c
HO
10
11
68
45
1s
10
1f
NH2
BnO
NH2
OBn
1q
1b
11
HO
OH
Cl
Cl
12
13
74
48
1d
1s
12
HO
O
O
1s
OH
1j
1j
13
14
O
O
14D
48
1a
(Continued)

RESEARCH FRONT
572
R. Balamurugan et al.
Table 5. (Continued)
A
B
Entry
Product
YieldC [%]
O
O
15D
51
1a
14
15
1j
16D
45
28
O
O
1k
1a
NH2
NH2
NH2
17D
1a
1b
16
16
NH2
18D
54
1a
1b
HO
OH
19D
35
55
1s
1r
17
H3C (CH2)5
(CH2)5
CH3
20
1t
18
1g
A1 equivalent.
B5 equivalents.
CIsolated yield.
DReaction was carried out for 48 h.
[22]
1,4-Di-m-tolylbuta-1,3-diyne (2h)[17d]
´
2,2-(Buta-1,3-diyne-1,4-diyl)dibenzeneamine (2b)
dH 7.35 (d, J 7.6, 2H), 7.17 (t, J 8.0, 7.2, 2H), 6.69 (t, J 8.0,
4H), 4.33 (s, 4H). dC 149.53, 133.04, 130.67, 118.01, 114.46,
106.19, 79.75, 79.03.
dH 7.37 (m, 4H), 7.27–7.20 (m, 4H), 2.37 (s, 6H). dC 138.22,
133.03, 130.20, 129.67, 128.39, 121.68, 81.70, 73.74, 21.27.
1,4-Bis(2-methoxyphenyl)buta-1,3-diyne (2i)[10b]
1,4-Bis(2-bromophenyl)buta-1,3-diyne (2c)[23]
dH 7.48 (dd, J 7.6, 1.6, 2H), 7.35–7.31 (m, 2H), 6.91 (m, 4H),
3.89 (s, 6H). dC 161.34, 134.40, 130.61, 120.52, 111.23, 110.97,
110.67, 78.70, 78.0, 55.82.
dH 7.61–7.56 (m, 4H), 7.31–7.20 (m, 4H). dC 134.54, 132.62,
130.41, 127.13, 126.21, 124.07, 81.09, 77.87.
1,4-Bis(3-methoxyphenyl)buta-1,3-diyne (2j)[10b]
1,4-Bis-(4-chlorophenyl)buta-1,3-diyne (2d)[17d]
dH 7.45 (d, J 8.4, 4H), 7.32 (d, J 8.0, 4H).
dH 7.26 (t, J 8.0, 2H), 7.14 (d, J 8.0, 2H), 7.06 (s, 2H), 6.95
(dd, J 8.0, 4.0, 2H), 3.81 (s, 6H). dC 159.31, 129.58, 125.10,
122.69, 117.09, 116.06, 81.54, 73.68, 55.32.
1,4-Bis-(3-chlorophenyl)buta-1,3-diyne (2e)[11a]
1,4-Bis(4-methoxyphenyl)buta-1,3-diyne (2k)[9a]
dH 7.52 (s, 2H), 7.40 (d, J 7.6, 2H), 7.60 (d, J 8.0, 2H), 7.27
(m, 2H). dC 134.37, 132.28, 130.67, 123.29, 80.56, 74.86.
dH 7.46 (d, J 8.4, 4H), 6.85 (d, J 8.8, 4H), 3.83 (s, 6H).
dC 160.25, 134.05, 114.14, 113.9, 81.23, 73.04, 55.35.
1,4-Di(napthalen-1-yl)buta-1,3-diyne (2f)[11a]
dH 8.42 (d, J 7.6, 2H), 7.86 (d, J 7.6, 4H), 7.82 (d, J 7.2, 2H),
7.62 (t, J 7.6, 2H), 7.54 (d, J 7.6, 2H), 7.44 (t, J 7.2, 2H).
dC 133.94, 133.15, 132.11, 129.82, 128.50, 127.29, 126.76,
126.18, 125.28, 119.56, 81.02, 78.76.
1,4-Bis(2,4-dimethylphenyl)buta-1,3-diyne (2l)
dH 7.16 (s, 4H), 7.0 (s, 2H), 2.31 (s, 12H). dC 138.03, 131.16,
130.14, 121.50, 81.67, 73.39, 21.10. nmax (neat)/cmꢁ1 2916,
2854, 2143, 1591, 846, 750, 682, 462. Anal. Calc. for C12H12O2:
C 92.98, H 7.02. Found: C 92.85, H 7.10.
1,4-Di-p-tolylbuta-1,3-diyne (2g)[9a]
1,4-Bis(4-methoxy2-methylphenyl)buta-1,3-diyne (2m)
dH (CDCl3, 400 MHz) 7.43 (d, J 8.0, 4H), 7.15 (d, J 8.0, 4H),
2.38 (s, 6H). dC (CDCl3, 100 MHz) 139.52, 132.41, 129.24,
118.78, 81.56, 73.45, 21.66.
dH 7.43 (d, J 8.4, 2H), 6.75 (s, 2H), 6.69 (dd, J 8.4, 4.4, 2H),
3.85 (s, 6H), 2.47 (s, 6H). dC 160.07, 143.52, 134.36, 115.21,

RESEARCH FRONT
Homo and Heterocoupling of Terminal Alkynes
573
114.10, 111.44, 80.81, 76.48, 55.28, 21.03. nmax (neat)/cmꢁ1
2974, 2137, 1896, 1597, 1564, 1491, 1460, 1307, 1236, 1163,
1095, 1033, 823, 688, 590, 489. Anal. Calc. for C12H12O2:
C 82.73, H 6.25. Found: C 82.65, H 6.31.
2-Methyl-6-phenylhexa-3,5-diyn-2-ol (5)[17d]
dH 7.48 (d, J 7.6, 2H), 7.38–7.30 (m, 3H), 2.17 (br s, 1H), 1.59
(s, 6H). dC 132.53, 129.26, 128.44, 121.55, 86.69, 78.81, 73.14,
67.07, 65.77, 31.13.
1,4-Di(pyridin-3-yl)buta-1,3-diyne (2n)[9k]
5-p-Tolylpenta-2,4-diyn-1-ol (6)[24]
dH ((D6)acetone) 8.66 (s, 2H), 8.51 (d, J 4.0, 2H), 7.87 (d,
J 8.0, 2H), 7.35–7.32 (m, 2H). dC ((D6)acetone) 152.84, 149.93,
139.38, 123.43, 118.28, 79.18, 75.74.
dH 7.39 (d, J 8.0, 2H), 7.12 (d, J 8.0, 2H), 4.42 (s, 2H), 2.36
(s, 3H), 2.03 (br s, 1H). dC 139.82, 132.55, 129.24, 118.23,
80.11, 78.93, 72.58, 70.61, 51.70, 21.65.
2,7-Dimethylocta-3,5-diyne-2,7-diol (2o)[17d]
6-(Benzyloxy)hexa-2,4-diyn-1-ol (7)
dH 7.35–7.28 (m, 5H), 4.60 (s, 2H), 4.32 (s, 2H), 4.23 (s, 2H),
2.09 (br s, 1H). dC 136.95, 128.54, 128.22, 128.10, 77.18, 75.77,
71.80, 70.52, 69.88, 57.53, 51.43. nmax (neat)/cmꢁ1 3389,
3036, 2928, 2249, 2179, 1454, 1026, 738, 698. Anal. Calc. for
C13H12O2: C 77.98, H 6.04. Found: C 77.85, H 6.12.
dH 2.02 (br s, 2H), 1.53 (s, 12H). dC 83.99, 66.33, 65.58, 31.04.
[9a]
´
1,1-(Buta-1,3-diyne-1,4diyl)dicylohexanol (2p)
dH 1.94–1.91 (m, 4H), 1.71–1.68 (m, 4H), 1.63–1.53 (m,
10H), 1.33–1.25 (m, 4H). dC 83.0, 69.22, 68.34, 39.66, 25.0,
23.11.
(2-Bromophenyl)-2-methylhexa-3,5-diyn-2-ol (8)
dH 7.57 (d, J 7.6, 1H), 7.51 (t, J 6.0, 1H), 7.26–7.20 (m, 2H),
2.27 (br s, 1H), 1.60 (s, 6H). dC 134.49, 132.56, 130.29,
127.10, 126.17, 123.99, 88.23, 76.85, 66.92, 65.81, 31.06.
n
C12H12O2: C 59.34, H 4.21. Found: C 59.55, H 4.18.
1,6-Bis(benzyloxy)hexa-2,4-diyne (2q)[17d]
dH 7.36–7.24 (m, 10H), 4.60 (s, 4H), 4.25 (s, 4H). dC 137.04,
128.51, 128.17, 128.04, 75.37, 71.81, 70.61, 57.55.
max (neat)/cmꢁ1 3294, 2235, 2150, 1466, 1163. Anal. Calc. for
1,4-Dicyclohexenylbuta-1,3-diyne (2r)[17d]
5-(2-Bromophenyl)penta-2,4-diyn-1-ol (9)
dH 6.24 (s, 2H), 2.12–2.11 (m, 8H), 1.61–1.57 (m, 8H). dC
138.13, 119.96, 82.70, 71.55, 28.69, 25.87, 22.13, 21.32.
dH 7.58 (d, J 7.2, 1H), 7.51 (dd, J 6.0, 1.6, 1H), 7.29–7.19
(m, 2H), 4.44 (s, 2H), 2.01 (br s, 1H). dC 134.47, 132.52, 130.37,
127.06, 126.25, 123.75, 82.00, 70.19, 51.64. nmax (neat)/cmꢁ1
3341, 3069, 2920, 2856, 2245, 1585, 1556, 1469, 1433, 1109,
1014, 754, 686. Anal. Calc. for C11H7OBr: C 56.20, H 3.00.
Found: C 56.31, H 3.07.
Hexa-2,4-diyne-1,6-diol (2s)[17d]
dH ((D6)acetone) 4.28 (br s, 2H), 4.15 (d, J 4.8, 4H). dC
((D6)acetone) 78.58, 68.04, 49.93.
Hexadeca-7,9-diyne (2t)[9a]
5-(Napthalen-1-yl)penta-2,4-diyn-1-ol (10)
dH 8.28 (d, J 8.4, 1H), 7.84 (dd, J 8.0, 3.2, 2H), 7.73 (d, J 7.2,
1H), 7.57 (dt, J 6.8, 1.2, 1H), 7.51 (dt, J 6.8, 1.2, 1H), 7.40 (t,
J 8.0, 1H), 4.47 (s, 2H), 2.04 (br s, 1H). dC 133.94, 133.05,
132.22, 129.92, 128.47, 127.29, 126.73, 125.95, 125.17, 119.02,
81.53, 77.80, 76.99, 70.64, 51.75. nmax (neat)/cmꢁ1 3364,
3059, 2916, 2856, 2233, 1356, 1028, 798, 771. Anal. Calc. for
C15H10O: C 87.36, H 4.89. Found: C 87.25, H 4.82.
dH 2.20 (t, J 7.2, 4H), 1.49–1.46 (m, 4H), 1.34 (m, 4H),
0.84–0.83 (t, J 7.2, 6H). dC 78.0, 66.1, 31.30, 28.45, 28.20, 22.5,
18.5, 14.1.
General Experimental Procedure for the CuCl2-Catalyzed
Heterocoupling of Alkynes
5-Phenylpenta-2,4-diyn-1-ol (3)[17d]
To a solution of phenylacetylene (1a) (100 mg, 0.98 mmol)
and propargyl alcohol (1s) (274 mg, 4.90 mmol) in THF (5 mL),
was added CuCl2 (13 mg, 0.098 mmol) and the mixture
allowed to stir at room temperature for 10 min. DBU (178 mg,
1.176 mmol) was added to the reaction mixture which was then
stirred vigorously under an air-filled balloon at room tempera-
ture. The reaction was monitored by TLC. After completion of
the reaction, the mixture was concentrated under reduced
pressure and the residue was purified by column chromatogra-
phy on silica gel using hexanes/ethyl acetate (1/5 v/v) as eluent
to obtain pure 3 in 65% yield (99 mg). dH 7.49–7.47 (m, 2H),
7.37–7.25 (m, 3H), 4.41 (s, 2H), 2.24 (br s, 1H). dC 132.61,
129.36, 128.44, 121.39, 80.51, 78.58, 73.22, 70.42, 51.61.
The above procedure was used to prepare the other unsym-
metrical diynes 4–18.
2-(5-(Benzyloxy)penta-1,3-diynyl)benzenamine (11)
dH 7.39 (d, J 4.0, 4H), 7.33 (d, J 6.8, 2H), 7.16 (t, J 7.6, 1H),
6.68 (t, J 7.2, 2H), 4.66 (s, 2H), 4.35 (s, 2H). dC 149.81, 137.16,
133.26, 130.81, 128.54, 128.20, 128.05, 117.94, 114.45, 105.67,
79.94, 78.53, 75.35, 71.85, 71.20, 57.87. nmax (neat)/cmꢁ1 3470,
3373, 3030, 2856, 2233, 2141, 1614, 1454, 1354, 1257, 750.
Anal. Calc. for C12H12O2: C 82.73, H 5.79, N 5.36. Found:
C 82.58, H 5.71, N 5.32.
5-(4-Chlorophenyl)penta-2,4-diyn-1-ol (12)
dH ((D6)acetone) 7.55 (d, J 8.4, 2H), 7.44 (d, J 8.4, 2H), 4.50
(t, J 6.0, 1H), 4.36 (d, J 6.0, 2H). dC ((D6)acetone) 135.10,
133.97, 128.98, 120.11, 83.46, 75.99, 74.22, 67.99, 50.13. nmax
(neat)/cmꢁ1 3443, 2241, 1589, 1487, 1087, 1012, 823, 522. Anal.
Calc. for C12H12O2: C 69.31, H 3.70. Found: C 69.45, H 3.65.
(5-(Benzyloxy)penta-1,3-dinyl)benzene (4)[17d]
5-(3-Methoxyphenyl)penta-2,4-diyn-1-ol (13)
dH 7.51 (d, J 6.4, 2H), 7.38–7.31 (m, 8H), 4.64 (s, 2H), 4.32
(s, 2H). dC 137.13, 132.64, 129.35, 128.51, 128.45, 128.20,
128.03, 121.44, 78.72, 78.13, 73.36, 71.77, 71.17, 57.77.
dH 7.26–7.20 (m, 1H), 7.09 (d, J 7.6, 1H), 7.01 (s, 1H), 6.93
(d, J 8.0, 1H), 4.42 (s, 2H), 3.79 (s, 3H), 2.10 (br s, 1H). dC

RESEARCH FRONT
574
R. Balamurugan et al.
159.26, 129.56, 125.20, 122.32, 117.22, 116.17, 80.52, 78.50,
72.97, 70.38, 55.34, 51.64. nmax (neat)/cmꢁ1 3462, 2918, 2839,
2239, 1577, 1458, 785. Anal. Calc. for C12H12O2: C 77.40,
H 5.41. Found: C 77.32, H 5.45.
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ANIE1350.3.0.CO;2-6
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T. Minami, H. Nishihara, T. Hiraoka, Bull. Chem. Soc. Jpn. 1994, 67,
1717. doi:10.1246/BCSJ.67.1717
1-Methoxy-3-(phenylbuta-1,3-diynyl)benzene (14)
dH 7.53–7.51 (m, 2H), 7.37–7.31 (m, 3H), 7.26–7.22 (m, 1H),
7.12 (d, J 7.6, 1H), 7.04 (s, 1H), 6.92 (dd, J 2.8, 2.4, 1H), 3.80
(s, 3H). dC 159.33, 132.53, 129.56, 129.26, 128.47, 125.09,
122.75, 121.78, 117.10, 116.06, 81.62, 81.51, 73.90, 73.74,
55.32. nmax (neat)/cmꢁ1 2208, 2141, 1597, 1504, 1487, 1249,
1028, 690, 530. Anal. Calc. for C17H12O: C 87.90, H 5.21.
Found: C 87.85, H 5.26.
(b) F. Alonso, I. P. Beletskaya, M. Yus, Chem. Rev. 2004, 104, 3079.
doi:10.1021/CR0201068
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New York, NY).
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molecular Chemistry (Ed. V. Vogtle) 1996, Vol. 2, pp. 29–67
(Pergamon: Oxford, UK).
1-Methoxy-4-(phenylbuta-1,3-diynyl)benzene (15)[9h]
dH 7.52 (d, J 6.8, 2 H), 7.47 (d, J 7.6, 2H), 7.33 (m, 3H), 6.85
(d, J 8.4, 2H), 3.82 (s, 1H). dC 160.38, 134.15, 132.45, 129.05,
128.43, 122.02, 114.18, 113.71, 81.83, 81.04, 74.17, 72.74,
55.36.
(b) J.-M. Lehn, Supramolecular Chemistry: Concepts and Perspec-
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2-(Phenylbuta-1,3-diynyl)benzenamine (16)[20]
dH 7.52 (d, J 6.8, 2H), 7.36–7.33 (m, 4H), 7.15 (t, J 8.0, 1H),
6.70–6.66 (m, 2H), 4.32 (br s, 2H). dC 149.61, 133.12, 132.42,
130.68, 129.19, 128.49, 121.88, 117.98, 114.42, 106.13, 82.72,
79.05, 78.64, 73.95.
(b) J. S. Yadav, B. V. S. Reddy, K. U. Gayathri, A. R. Prasad,
Tetrahedron Lett. 2003, 44, 6493. doi:10.1016/S0040-4039(03)
01565-X
(c) L. Li, J. Wang, G. Zhang, Q. Liu, Tetrahedron Lett. 2009, 50, 4033.
doi:10.1016/J.TETLET.2009.04.065
(d) D. Li, K. Yin, J. Li, X. Jia, Tetrahedron Lett. 2008, 49, 5918.
doi:10.1016/J.TETLET.2008.07.138
(e) Q. Zheng, R. Hua, Y. Wan, Appl. Organometal. Chem. 2010, 24,
314. doi:10.1002/AOC.1604
(f) P. Kuhn, A. Alix, M. Kumar Raja, B. Louis, P. Pale, J. Sommer, Eur.
J. Org. Chem. 2009, 423. doi:10.1002/EJOC.200800848
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12, 45. doi:10.1039/B917448F
5-Cyclohexenylpenta-2,4-diyn-1-ol (17)
dH 6.29 (m, 1H), 4.31 (s, 2H), 2.17–2.10 (m, 4H), 1.84 (br s,
1H), 1.62–1.58 (m, 4H). dC 139.30, 119.44, 80.77, 79.36, 70.71,
70.62, 51.69, 28.51, 25.87, 22.04, 21.23. nmax (neat)/cmꢁ1 3389,
2930, 2235, 1664, 1435, 1350, 1016. Anal. Calc. for C12H12O2:
C 82.46, H 7.55. Found: C 82.33, H 7.61.
(h) K. Balaraman, V. Kesavan, Synthesis 2010, 20, 3461. doi:10.1055/
S-0030-1258199
(i) M. W. Paixa˜o, M. Weber, A. L. Braga, J. B. de Azeredo, A. M.
Deobald, H. A. Stefani, Tetrahedron Lett. 2008, 49, 2366. doi:10.1016/
J.TETLET.2008.02.083
(j) Y. Nishihara, M. Okamoto, M. Miyazaki, M. Miyasaki, K. Takagi,
Tetrahedron Lett. 2005, 46, 8661. doi:10.1016/J.TETLET.2005.10.056
(k) K. Kamata, S. Yamaguchi, M. Kotani, K. Yamaguchi,
N. Mizuno, Angew. Chem. Int. Ed. 2008, 47, 2407. doi:10.1002/ANIE.
200705126
1-(Deca-1,3-diynyl)-4-methylbenzene (18)
dH 7.36 (d, J 8.0, 2H), 7.10 (d, J 8.0, 2H), 2.36–2.34 (m, 5H),
1.60–1.55 (m, 2H), 1.46–1.38 (m, 2H), 1.34–1.28 (m, 4H), 0.89
(t, J 6.8, 3H). dC 139.08, 132.40, 129.12, 119.02, 84.50, 74.95,
73.77, 65.15, 31.31, 28.57, 28.28, 22.53, 21.55, 19.60, 14.05.
nmax (neat)/cmꢁ1 2930, 2854, 2243, 2152, 1604, 1508, 1456,
1180, 1116, 1020, 815, 723. Anal. Calc. for C12H12O2: C 91.01,
H 8.99. Found: C 91.12, H 8.85.
[10] (a) A. Lei, M. Srivastava, X. Zhang, J. Org. Chem. 2002, 67, 1969.
doi:10.1021/JO011098I
Acknowledgement
(b) S.-N. Chen, W.-Y. Wu, F.-Y. Tsai, Green Chem. 2009, 11, 269.
doi:10.1039/B815812F
(c) J.-H. Li, Y. Liang, Y.-X. Xie, J. Org. Chem. 2005, 70, 4393.
doi:10.1021/JO0503310
This work was funded by Department of Science and Technology (DST),
India. N.N., S.M., and M.V.N. thank CSIR, India for their fellowships.
(d) J.-H. Li, Y. Liang, X.-D. Zhang, Tetrahedron 2005, 61, 1903.
doi:10.1016/J.TET.2004.12.026
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