Ligand-free synthesis of 1,4-disubstituted-1,3-diynes by iron/copper cocatalyzed homocoupling of terminal alkynes

Article abstract of DOI:10.1002/cjoc.201200878

A simple and efficient protocol for Fe/Cu cocatalyzed oxidative homocoupling reaction of terminal alkynes to symmetrical 1,4-disubstituted-1,3- diynes was presented. The results showed that both CuBr and FeCl₃ played crucial roles in the reaction. It is noteworthy that this protocol employs mild, efficient, aerobic and ligand free conditions. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed into the corresponding 1,3-diynes in good to excellent yields. A simple and efficient protocol for Fe/Cu cocatalyzed oxidative homocoupling reaction of terminal alkynes to symmetrical 1,4-disubstituted-1,3-diynes was presented. The results showed that both CuBr and FeCl₃ played crucial roles in the reaction. It is noteworthy that this protocol employs mild, efficient, aerobic and ligand free conditions. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed into the corresponding 1,3-diynes in good to excellent yields. Copyright

Full text of DOI:10.1002/cjoc.201200878

FULL PAPER
DOI: 10.1002/cjoc.201200878
Ligand-Free Synthesis of 1,4-Disubstituted-1,3-diynes by
Iron/Copper Cocatalyzed Homocoupling of Terminal Alkynes
Peipei Wang, Xiaoyan Liu, and Songlin Zhang*
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Mate-
rials Science of Soochow University, Suzhou, Jiangsu 215123, China
A simple and efficient protocol for Fe/Cu cocatalyzed oxidative homocoupling reaction of terminal alkynes to
symmetrical 1,4-disubstituted-1,3-diynes was presented. The results showed that both CuBr and FeCl3 played cru-
cial roles in the reaction. It is noteworthy that this protocol employs mild, efficient, aerobic and ligand free condi-
tions. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed into the corre-
sponding 1,3-diynes in good to excellent yields.
Keywords catalysis, copper, iron, 1,3-diyne, ligand-free
As is well known, iron complexes are cheap,
relatively less toxic and environmentally benign.[8a-8e,12]
Since Kharasch[13] found that iron was successful in
catalyzing the homocoupling of Grignard reagents in
1941, iron-catalysis has been used more frequently and
with wider applications.[11b,11e,14] Taillefer et al. reported
an efficient iron/copper co-catalytic system for arylation
of nitrogen nucleophiles.[11a,15] Wakharkar and co-
workers showed the N-arylation of various amines with
aryl halides in the presence of a heterogeneous recy-
clable Fe-Cu hydrotalcite.[16] Recently, our group re-
ported iron/copper co-catalyzed O-arylation of phenols
with bromoarenes[17a] and N-arylation of arylamines
with bromoarenes.[17b] In 2010, Chen’s group used
Fe(acac)3/Cu(acac)2 system to catalyze the Glaser cou-
pling reaction, in this reaction, acac plays the role of
ligand.[8i] Herein, we present an ligand-free Fe/Cu co-
catalyzed system for homocoupling reaction of terminal
alkynes.
Introduction
Since Glaser oxidative homo-coupling reaction of
terminal alkyne was reported in 1869,[1] 1,4-disubtituted-
1,3-diynes have attracted a great deal of interest. Due to
its important application in the organic synthesis of
natural products,[2] pharmaceuticals (such as anti-
fungal,[3] antitumor,[2b-2d] antibacterial,[4] and supra-
molecular materials,[5]) and in the construction of π-
conjugated acetylenic oligomers and polymers,[6] more
and more efficient and selective methods for the
synthesis of alkynes have been developed.[7,8,20] Current
methods for the homocoupling of terminal alkynes for
1,3-diynes synthesis include palladium[7] and copper[8]
salt catalyst systems. Although palladium catalysis has
played a key role because of its mild, efficient, and se-
lective properties,[7] they are expensive, and often re-
quire the use of air-sensitive and noxious phosphine
ligands or amines reagents which have characteristic
foul smell and pungent flavor. Copper-mediated homo-
coupling reactions are an alternative strategy, however,
they usually need stoichiometric amount of copper
salts,[1a,8a,9] ligands, high temperature,[8a,8d,8e,8f,8n] or have
low to moderate yields to aliphatic diynes.[8g] Recently,
our group reported the homocoupling reaction of
terminal alkynes in the presence of catalytic amounts of
CuI and TMEDA under an atmosphere of air at ambient
temperature, but the drawback was the essential need of
ligand reagent.[10] From the economic and environmen-
tal point of view, it is significant to search new ap-
proaches for Pd-, and ligand-free homocoupling of
terminal alkynes.
Results and Discussion
In our initial study, the homocoupling reaction of
phenylacetylene (1a) was chosen as a model for the op-
timization of the reaction conditions. The results for the
screening of the reaction conditions to promote the
catalytic homocoupling of phenylacetylene are shown in
Table 1.
As shown in Table 1, only a 3% yield of 1,4-diphe-
nylbuta-1,3-diyne (2a) was obtained in the absence of
Cu salts (Table 1, Entry 1). Without Fe salts, phenyl-
acetylene was transformed to the corresponding diyne in
*
E-mail: zhangsl@suda.edu.cn; Tel.: 0086-0512-65880352; Fax: 0086-0512-65880352
Received September 3, 2012; accepted October 9, 2012; published online December 11, 2012.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201200878 or from the author.
Chin. J. Chem. 2013, 31, 187—194
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Wang, Liu & Zhang
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Table 1 Optimization of reaction conditionsa
[Fe] [Cu]
Air, RT
2
2a
1a
Entry
1
Cu salt
Fe salt
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
FeCl3
Base
Solvent
THF
yieldb/%
3
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
Et3N
2
CuSO4•5H2O
CuBr
THF
72
3
THF
90
4
Cu2O
CuCl
THF
10
5
THF
80
6
Cu(acac)2
CuBr
THF
60
7
THF
40
8
CuBr
Fe2O3
Fe(NO3)3•9H2O
FeC2O4•H 2O
Fe3O4
THF
80
9
CuBr
THF
36
10
11
12
13
14
15
16
17
18
19
20
21
22
CuBr
THF
50
CuBr
THF
79
CuBr
Fe(acac)3
FeCl3•6H2O
FeCl3
THF
50
CuBr
THF
55
CuBr
THF
trace
8
CuBr
FeCl3
K2CO3
THF
CuBr
FeCl3
NaOH
THF
10
CuBr
FeCl3
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
CH3ONa
ethanol
CH2Cl2
DMF
acetone
THF
30
CuBr
FeCl3
48
CuBr
FeCl3
trace
45
88c
CuBr
FeCl3
CuBr
FeCl3
CuBr
FeCl3
THF
91d
a The reaction was performed with phenylacetylene (1.0 mmol), Cu source (5 mol%), Fe source (10 mol% ) and base (3.0 mmol) in sol-
vent (5 mL) under ambient temperature for 20 h. b Isolated yield. c 50 ℃ 16 h. d 70 ℃ 16 h.
40% yield (Table 1, Entry 7). However, when 10 mol%
Fe salts and 5 mol% Cu salts were used as a co-catalyst,
the yield enhanced obviously (Table 1, Entries 2－6,
Entries 8－13). These results show that both Cu and Fe
salts play important roles in the oxidative homocoupling
reaction of terminal alkynes. Then we investigated the
effect of the Cu salts, a better yield was obtained when
CuBr was used, compared with CuSO4•5H2O, Cu2O,
CuCl and Cu(acac)2 (Table 1, Entries 2－6). Hence the
CuBr was used in experiments to investigate the effect
of Fe salts in the homocoupling reaction. Among the Fe
salts tested in our experiments, FeCl3 was found to be
the most effective and afforded 90% yield (Table 1, En-
try 3, Entries 8－13). Furthermore, the effect of bases
was studied. From the results, we found that CH3ONa
was the best one in the reaction (Table 1, Entries 3, 14
－16). Then, we tested the effect of solvents. After in-
vestigating some solvents, THF was found to be the best
choice (Table 1, Entries 3, 17－20). Finally the effect of
temperature on the reaction was also examined. We
found when the temperature was elevated, the yield and
reaction rate were not improved significantly (Table 1,
Entries 21－22). Balancing all these results, it was con-
cluded that the most optimal condition for the homo-
coupling reaction involved the use of FeCl3 (10 mol%)
and CuBr (5 mol%) as catalyst, CH3ONa as the base
and air as the oxidant at room temperature.
Under the optimized condition, the homocoupling of
a series of terminal alkynes was investigated, the
selective results are summarized in Table 2. The
catalytic oxidative homocoupling reactions of ethynyl-
benzene derivatives with electron-donating (1b－1c,
1e－1f, 1i) as well as electron-withdrawing (1d, 1g－1h)
substituents proceeded well to afford the corresponding
aromatic 1,4-disubstituted-1,3-diyne derivatives in high
yields (2b－2i). 1-Ethynylnaphthalene (1j) and 2-
ethynyl-naphthalene (1k) were converted into the cor-
responding conjugated diynes (2j) and (2k) in 82% and
88% yields, respectively. It is well known that aliphatic
terminal alkynes are less reactive in undergoing Glaser
dimerization, probably due to the weaker acidity of the
acetylenic proton.[8g] 1-Ethynylcyclohexene (1l),
(E)-1-phenyl-1-buten-3-yne (1m), 1-octyne (1n), and
1-decyne (1o), were converted into the corresponding
1,4-dialkyl-1,3-diynes in good to excellent yields (2l－
2o). However, ethynylcyclopropane (1p) is an exception
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Ligand-Free Synthesis of 1,4-Disubstituted-1,3-diynes by Homocoupling of Terminal Alkynes
Table 2 CuBr/FeCl3 homocoupling reaction of terminal alkynesa
CuBr, FeCl3
R
R
R
2
Air, r.t.
1
2
Entry Substrate
Product
Yieldb/%
90
1c
2a
1a
2c
88
82
2b
1b
O
O
O
3c
2c
1c
F
F
F
4c
94
85
2d
1d
5c
2e
1e
6c
7c
84
77
2f
1f
Cl
Cl
Cl
2g
1g
Cl
Cl
8c
84
84
Cl
1h
2h
9c
1i
2i
10c
82
1j
2j
11c
12c
13c
88
71
68
2k
1k
2l
1l
1m
2m
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Wang, Liu & Zhang
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Continued
Yieldb/%
Entry Substrate
Product
14d
79
1n
2n
15d
83
45
85
1o
2o
16d
17d
2p
1p
O
O
O
2q
1q
18d
O
84
71
O
O
1r
2r
O
19d
O
O
O
1s
2s
2t
O
20d
21d
22d
81
88
O
O
1t
O
O
1u
2u
Cl
Cl
O
Cl
Cl
O
65
70
O
Cl
1v
2v
Cl
23d
O
O
1w
O
2w
24c
25c
50
56
N
N
S
N
S
2x
1x
S
2y
1y
a The reaction was performed with alkyne compounds (1.0 mmol), CuBr (5 mol%), FeCl3 (10 mol%) and CH3ONa (3.0 mmol) in THF (5
mL) under ambient temperature. b Isolated yield. c The aromatic alkynes react for 20 h. d The aliphatic alkynes react for 30 h.
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Ligand-Free Synthesis of 1,4-Disubstituted-1,3-diynes by Homocoupling of Terminal Alkynes
which afforded a moderate yield. The homocoupling
reaction of alkynes based on propargylic ether (1q－1w)
also smoothly proceeded to give the corresponding
diyne derivatives (2q－2w). And the heteroatom-
containing aromatic alkynes (1x, 1y) also furnish (2x)
and (2y) in moderate yields.
6H), 7.53－7.52 (m, 4H); 13C NMR δ: (CDCl3, 75 MHz)
δ: 74.16, 81.80, 122.02, 128.69, 129.46, 132.75; IR
(KBr) ν: 3034, 2142, 1638, 1477, 1431, 908, 751 cm−1;
HRMS (EI) m/z calcd for C16H10 (M＋): 202.0783, found
202.0781.
1,4-Dip-tolylbuta-1,3-diyne (2b):[10] The title com-
pound was obtained according to the general procedure.
White solid; yield: 88%; m.p. 183－184 ℃ (lit.[10]
Conclusions
1
182－183 ℃); H NMR δ: (CDCl3, 300 MHz) δ: 2.36
In conclusion, we have successfully demonstrated an
efficient, facile and enviromentally friendly method for
FeCl3/CuBr co-catalyzed oxidative homocoupling
reaction of terminal alkynes. The great attractiveness of
the current protocol was based on the conditions of
ligand-free, avoidance of expensive palladium catalysts,
the use of air as oxidant instead of additive oxidant, the
use of CH3ONa instead of amines, ambient temperature
and good to excellent yields.
(s, 6H), 7.13 (d, J＝7.5 Hz, 4H),7.41 (d, J＝7.7 Hz, 4H);
13C NMR (CDCl3, 100 MHz) δ: 23.34, 75.14, 83.24,
120.45, 130.91, 134.08, 141.20; IR (KBr) ν: 3024, 2060,
1600, 1510, 1421, 816, 770 cm−1; HRMS (EI) m/z calcd
for C18H14 (M＋): 230.1096, found 230.1097.
1,4-Bis(4-methoxyphenyl)buta-1,3-diyne
The title compound was obtained according to the gen-
(2c):[10]
eral procedure. Yellow solid; yield: 82%; m.p. 138－
1
140 ℃ (lit.[7f] 140－142 ℃); H NMR (CDCl3, 300
MHz) δ: 3.82 (s, 6H), 6.85 (d, J＝7.4 Hz, 4H), 7.45 (d,
J＝7.3 Hz, 4H); 13C NMR (CDCl3, 100 MHz) δ: 57.03,
74.62, 82.92, 115.59, 115.81, 135.73, 161.91; IR (KBr)
ν: 2985, 2078, 1600, 1553, 1505, 1261, 1160, 1020, 842
cm−1; HRMS (EI) m/z calcd for C18H14O2 (M ＋ ):
262.0994, found 262.0994.
Experimental
General methods
All chemicals were purchased from Aldrich, Alfa or
Acros chemical company and used thus, without further
purification. Petroleum ether (PE) used refers to the 60
－90 ℃ boiling point fraction of petroleum. THF was
distilled from sodium benzophenone under nitrogen. All
reactions were conducted under air atmosphere. All
solvents were purchased from commercial source,
without further purification before use. The flash col-
umn chromatography was carried out on Merck silica
gel (300－400 mesh). The IR spectra were measured on
a varian 1000 FT-IR spectrometer as KBr disks (4000－
400 cm−1). 1H and 13C NMR spectra were recorded on a
Varian Mercury 400 or 300 MHz spectrometer as solu-
1,4-Bis(4-fluorophenyl)buta-1,3-diyne (2d):[10] The
title compound was obtained according to the general
procedure. White solid; yield: 94%; m.p. 191－192 ℃
1
(lit.[10] 194－195 ℃); H NMR (CDCl3, 400 MHz) δ:
7.04 (t, J＝7.5 Hz, 4H), 7.53－7.50 (m, 4H); 13C NMR
(CDCl3, 75 MHz) δ: 74.0, 80.9, 116.4 (d, JC−F＝22.2
Hz), 118.3, 135.0 (d, JC−F＝8.5 Hz),163.6 (d, JC−F
＝
252.1 Hz); IR (KBr) ν: 1590, 1496, 1220, 1156, 826,
687 cm−1; HRMS (EI) m/z calcd for C16H8F2 (M＋):
238.0954, found 238.0953.
1,4-Bis(4-tert-butylphenyl)buta-1,3-diyne (2e): The
title compound was obtained according to the general
procedure. White solid; yield: 85%; compound purity:
1
tions in CDCl3. Chemical shifts (δ) in H NMR spectra
are reported downfield from the internal standard Me4Si
(TMS). Chemical shifts in 13C NMR spectra are re-
ported relative to the central line of the chloroform sig-
nal (δ＝77.50). High-resolution mass spectra were ob-
tained with a GCT-TOF instrument.
1
99.32% (confirmed by HPLC); m.p. 190－192 ℃; H
NMR (CDCl3, 400 MHz) δ: 1.31 (s, 18H), 7.35 (d, J＝
8.4 Hz, 4H), 7.46 (d, J＝8.3 Hz, 4H); 13C NMR (CDCl3,
75 MHz) δ: 29.15, 32.94, 71.55, 79.55, 116.86, 123.51,
130.30, 150.58; IR (KBr) ν: 2143, 1636, 1503, 1088,
1041, 910, 785, cm−1; HRMS (EI) m/z calcd for C24H26
(M＋): 314.2035, found 314.2035.
General procedure for the 1,4-disubstituted-1,3-di-
yne reaction
1,4-Bis(3-methylphenyl)buta-1,3-diyne (2f):[8l] The
title compound was obtained according to the general
procedure. White solid; yield: 84%; m.p. 74－75 ℃
Alkyne (1.0 mmol), FeCl3 (16.3 mg, 10 mol%),
CuBr (7.2 mg, 5 mol%) and CH3ONa (162 mg, 3 mmol)
were added to 5 mL of THF under ambient temperature
in the open air. The reaction mixture was stirred under
room temperature for 20 h or 30 h. The progress of the
reaction was monitored by TLC. After completion of
the reaction, the solvent was removed under reduced
pressure and the crude product obtained was purified by
column chromatography over silica gel to afford 1,4-di-
substituted-1,3-diyne.
1
(lit.[8l] 68－70 ℃); H NMR (CDCl3, 400 MHz) δ:
7.34－7.32 (m, 4H), 7.25－7.16 (m, 4H), 2.34 (s, 6H);
13C NMR (CDCl3, 75 MHz) δ: 138.17, 132.98, 130.13,
129.61, 128.33, 121.63, 81.63, 73.67, 21.23; IR (KBr) ν:
3012, 2957, 2142, 1618, 1497, 1462, 1103, 1013, 835,
620 cm−1; HRMS (EI) m/z calcd for C18H14 (M＋ ):
230.1096, found 230.1095.
1,4-Diphenylbuta-1,3-diyne (2a):[10] The title com-
pound was obtained according to the general procedure.
White solid; yield: 90%; m.p. 89－91 ℃ (lit.[7f] 86－
1,4-Bis(3-chlorophenyl)buta-1,3-diyne (2g):[8b] The
title compound was obtained according to the general
procedure. Yellow solid; yield: 77%; m.p. 88－89 ℃;
1H NMR (CDCl3, 400 MHz) δ: 7.29－7.27 (m, 2H),
1
88 ℃); H NMR (CDCl3, 400 MHz) δ: 7.36－7.33 (m,
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Wang, Liu & Zhang
FULL PAPER
7.41－7.34 (m, 4H), 7.50 (s, 2H); 13C NMR (CDCl3, 75
MHz) δ: 74.69, 80.55, 123.25, 129.71, 130.65, 132.25,
134.33; IR (KBr) ν: 2926, 2138, 1629, 1501, 1458, 1174,
1117, 1018, 838, 725 cm−1; HRMS (EI) m/z calcd for
C16H8Cl2 (M＋): 270.0003, found 270.0006.
134 ℃; 1H NMR (CDCl3, 300 MHz) δ: 6.26 (d, J＝16.3
Hz, 2H), 7.10 (d, J＝16.0 Hz, 2H), 7.39－7.25 (m, 10H);
13C NMR (CDCl3, 75 MHz) δ: 76.52, 82.18, 106.94,
126.55, 128.89, 129.32, 135.85, 144.50; IR (KBr) ν:
3020, 2346, 954, 744, 682 cm−1; HRMS (EI) m/z calcd
for C20H14 (M＋): 254.1096, found 254.1094.
1,4-Bis(2-chlorophenyl)buta-1,3-diyne (2h):[8l] The
title compound was obtained according to the general
procedure. White solid; yield: 84%; m.p. 142－143 ℃
Hexadeca-7,9-diyne (2n):[10] The title compound
was obtained according to the general procedure. Col-
ourless liquid; yield: 79%; 1H NMR (CDCl3, 400 MHz)
δ: 0.90 (t, J＝6.7 Hz, 6H), 1.32－1.26 (m, 8H), 1.56－
1.50 (m, 4H), 1.40－1.36 (m, 4H), 2.23 (t, J＝6.9 Hz,
4H); 13C NMR (CDCl3, 75 MHz) δ: 14.23, 19.40, 22.73,
28.53, 28.74, 31.51, 65.46, 77.67; IR (KBr) ν: 2897,
2753, 1432, 1195, 708 cm−1; HRMS (EI) m/z calcd for
C16H26 (M＋): 218.2035, found 218.2032.
1
(lit.[8l] 138－140 ℃); H NMR (CDCl3, 300 MHz) δ:
7.27 (t, J＝10.4 Hz, 4H), 7.42 (d, J＝7.5 Hz, 2H), 7.58
(d, J＝7.1 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ:
76.91, 79.96, 122.00, 126.78, 129.66, 130.51, 134.59,
137.17; IR (KBr) ν: 3058, 2142, 746, 670 cm−1; HRMS
(EI) m/z calcd for C16H8Cl2 (M＋): 270.0003, found
270.0005.
1,4-Bis(4-pentylphenyl)buta-1,3-diyne (2i):[8h] The
title compound was obtained according to the general
procedure. White solid; yield: 84%; m.p. 83－84 ℃
(lit.[8h] 84－85 ℃); 1H NMR (CDCl3, 400 MHz) δ: 0.89
(t, J＝6.2 Hz, 6H), 1.32－1.31 (m ,8H), 1.62－1.55 (m,
4H), 2.61 (t, J＝7.6 Hz, 4H), 7.14 (d, J＝7.9 Hz, 4H),
7.43 (d, J＝7.9 Hz, 4H); 13C NMR (CDCl3, 75 MHz) δ:
14.04, 22.54, 30.89, 31.46, 35.98, 73.51, 81.60, 118.98,
128.57, 132.41, 144.50; IR (KBr) ν: 2927, 2157, 1587,
1559, 1470, 1094, 1014, 879, 775 cm−1; HRMS (EI) m/z
calcd for C26H30 (M＋): 342.2348, found 342.2351.
1,4-Di(naphthalen-1-yl)buta-1,3-diyne (2j):[7a] The
title compound was obtained according to the general
procedure. Yellow solid; yield: 82%; m.p. 180－181 ℃
Icosa-9,11-diyne (2o):[10] The title compound was
obtained according to the general procedure. Colourless
liquid; yield: 83%; 1H NMR (CDCl3, 400 MHz) δ: 0.88
(t, J＝5.4 Hz, 6H), 1.51－1.27 (m, 20H), 1.59－1.54 (m,
4H), 2.24 (t, J＝6.9 Hz, 4H); 13C NMR (CDCl3, 75
MHz) δ: 14.29, 19.41, 22.87, 28.58, 29.07, 29.29, 29.37,
32.04, 65.47, 77.67; IR (KBr) ν: 2928, 2861, 1455, 965,
724 cm−1; HRMS (EI) m/z calcd for C20H34 (M＋ ):
274.2661, found 274.2662.
1,4-Dicyclopropylbuta-1,3-diyne (2p):[10] The title
compound was obtained according to the general pro-
cedure. Colourless liquid; yield: 45%; 1H NMR (CDCl3,
400 MHz) δ: 0.82－0.72 (m, 8H), 1.34－1.25 (m, 2H);
13C NMR (CDCl3, 75 MHz) δ: 0.22, 8.91, 61.02, 80.21;
IR (KBr) ν: 2089, 1411, 1324, 923 cm−1; HRMS (EI)
m/z calcd for C10H10 (M＋): 130.0783, found 130.0783.
1,4-Bis(1-methoxycyclohexyl)buta-1,3-diyne (2q):[10]
The title compound was obtained according to the gen-
eral procedure. White solid; yield: 85%; m.p. 63－64 ℃
(lit.[10] 60－61 ℃); 1H NMR (CDCl3, 400 MHz) δ: 1.32
－1.26 (m, 3H), 1.62－1.52 (m, 13H), 1.92－1.91 (m,
4H), 3.38 (s, 6H); 13C NMR (CDCl3, 75 MHz) δ: 22.79,
25.51, 36.67, 51.28, 70.10, 74.58, 80.57; IR (KBr) ν:
2935, 2135, 1448, 1344, 1273, 1084, 925, 804 cm−1;
HRMS (EI) m/z calcd for C18H26O2 (M＋): 274.1933,
found 274.1935.
1
(lit.[7a] 177－180 ℃); H NMR (CDCl3, 300 MHz) δ:
7.67－7.44 (m, 6H), 7.90－7.82 (m, 6H), 8.34 (d, J＝
7.8 Hz, 2H); 13C NMR (CDCl3, 100 MHz) δ: 78.92,
81.18, 119.73, 125.47, 126.37, 126.94, 127.47, 128.68,
130.00, 132.29, 133.32, 134.12; IR (KBr) ν: 3050, 2129,
771 cm−1; HRMS (EI) m/z calcd for C24H14 (M＋ ):
302.1096, found 302.1098.
1,4-Di(naphthalen-2-yl)buta-1,3-diyne (2k): The title
compound was obtained according to the general pro-
cedure. Yellow solid; yield: 88%; m.p. 202－204 ℃; IR
1
(KBr) ν: 3055, 2351, 804 cm−1; H NMR (CDCl3, 400
MHz) δ: 7.36－7.34 (m, 2H), 7.57－7.51 (m, 6H),
7.81－7.79 (m, 4H), 8.09 (s, 2H); 13C NMR (CDCl3, 75
MHz) δ: 74.37, 82.22, 119.7, 126.78, 127.24, 127.68,
127.86, 128.19, 128.49, 129.46, 133.06, 133.88; HRMS
(EI) m/z calcd for C24H14 (M ＋ ): 302.1096, found
302.1093.
1,4-Bis(1-(benzyloxy)isopropyl)buta-1,3-diyne (2r):
The title compound was obtained according to the gen-
eral procedure. White solid; yield: 84%; m.p. 55－57 ℃;
1
compound purity: 99.65% (confirmed by HPLC); H
NMR (CDCl3, 400 MHz) δ: 1.57 (s, 12H), 4.63 (s, 4H),
7.38－7.24 (m, 10H); 13C NMR (CDCl3, 75 MHz) δ:
28.73, 66.91, 68.59, 71.10, 127.52, 127.74, 128.38,
138.69, 181.77; IR (KBr) ν: 3028, 2984, 2160, 1617,
1498, 1453, 1383, 1360, 1046, 775, 674 cm−1; HRMS
(EI) m/z calcd for C24H26O2 (M＋): 346.1933, found
346.1938.
1,4-Bis(1-ethynylcyclohexyl)buta-1,3-diyne (2l):[8h]
The title compound was obtained according to the gen-
1
eral procedure. Yellow liquid; yield: 71%; H NMR
(CDCl3, 400 MHz) δ: 1.64－1.58 (m, 8H), 2.12－2.11
(m, 8H), 6.24 (s, 2H); 13C NMR (CDCl3, 75 MHz) δ:
19.33, 20.14, 23.88, 26.70, 69.57, 80.69, 117.95, 136.10;
IR (KBr) ν: 2136, 1644, 1627, 1393, 912, 743 cm−1;
HRMS (EI) m/z calcd for C16H18 (M＋): 210.1409, found
210.1411.
1,4-Bis(1-(benzyloxy)cyclohexyl)buta-1,3-diyne (2s):
The title compound was obtained according to the gen-
eral procedure. White solid; yield: 71%; m.p. 50－51 ℃;
(1E,7E)-1,8-Diphenylocta-1,7-dien-3,5-diyne (2m):[19]
The title compound was obtained according to the gen-
eral procedure. Yellow solid; yield: 68%; m.p. 133－
compound purity: 99.01% (confirmed by HPLC); H
1
NMR (CDCl3, 300 MHz) δ: 1.35－1.34 (m, 2H), 1.74－
1.55 (m, 14H), 1.98 (s, 4H), 4.67 (s, 4H), 7.39－7.28 (m,
192
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© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2013, 31, 187—194

Ligand-Free Synthesis of 1,4-Disubstituted-1,3-diynes by Homocoupling of Terminal Alkynes
10H); 13C NMR (CDCl3, 75 MHz) δ: 22.65, 25.33,
37.08, 65.79, 70.12, 74.50, 80.94, 127.35, 127.68,
128.28, 138.95; IR (KBr) ν: 3018, 2850, 2083, 1605,
1462, 1389, 768, 663 cm−1; HRMS (EI) m/z calcd for
C30H34O2 (M＋): 426.2559, found 426.2602.
(lit.[10] 92－93 ℃); 1H NMR (CDCl3, 300 MHz) δ: 7.00
(t, J＝8.4 Hz, 2H), 7.35－7.31 (m, 4H); 13C NMR
(CDCl3, 75 MHz) δ: 76.63, 80.88, 77.80, 121.90, 127.24,
128.94, 134.42; IR (KBr) ν: 3104, 1812, 1417, 830, 714
cm−1; HRMS (EI) m/z calcd for C12H6S2 (M ＋ ):
213.9911, found 213.9910.
1,4-Diphenoxyhexa-1,3-diyne (2t):[7a] The title
compound was obtained according to the general pro-
cedure. Yellow solid; yield: 81%; m.p. 82－84 ℃ (lit.[7a]
77－79 ℃); 1H NMR (CDCl3, 300 MHz) δ: 4.74 (s, 4H),
6.95－6.93 (m, 6H), 7.32－7.27 (m, 4H); 13C NMR
(CDCl3, 75 MHz) δ: 56.34, 71.23, 77.59, 115.05, 157.58,
121.98, 129.79; IR (KBr) ν: 3067, 2914, 2860, 1587,
1487, 1360, 743, 673 cm−1; HRMS (EI) m/z calcd for
C18H14O2 (M＋): 262.0994, found 262.0995.
Acknowledgement
We are grateful for financial support from the Na-
tional Natural Science Foundation of China (No.
21072143) and the Priority Academic Program Devel-
opment of Jiangsu Higher Education Institutions.
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title compound was obtained according to the general
procedure. Yellow solid; yield: 88%; compound purity:
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1
97.65% (confirmed by HPLC); m.p. 87－88 ℃; H
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NMR (CDCl3, 300 MHz) δ: 2.22 (s, 6H), 4.75 (s, 4H),
6.90 (t, J＝7.4 Hz, 4H), 7.14 (d, J＝7.0 Hz, 4H); 13C
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1
96.17% (confirmed by HPLC); m.p. 144－145 ℃; H
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The title compound was obtained according to the gen-
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purity: 97.02% (confirmed by HPLC); m.p. 69－71 ℃;
1H NMR (CDCl3, 300 MHz) δ: 4.25 (s, 4H), 4.57 (s,
4H), 7.28－7.26 (m, 4H), 7.34－7.30 (m, 4H); 13C
NMR (CDCl3, 75 MHz) δ: 57.76, 70.78, 71.08, 75.32,
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1
120－122 ℃); H NMR (CDCl3, 300 MHz) δ: 7.32－
7.27 (m, 2H), 7.55 (d, J＝7.7 Hz, 2H), 7.69 (t, J＝7.6
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MHz) δ: 73.11, 80.88, 123.80, 128.39, 136.20, 141.81,
150.35; IR (KBr) ν: 1556, 1403, 1219, 952, 743, 721
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Chin. J. Chem. 2013, 31, 187—194
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
193

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