Jin & Kuang
NOTE
groups on the aromatic ring can enhance the reaction
and lead to the desired product in excellent yields (2g,
6H), 6.81 (d, J=8.3 Hz, 2H), 7.01 (s, 2H), 7.14 (dd, J=
8.3, 1.7 Hz, 4H).
14
1
2
h). However, lower yield was obtained by using
1,4-Bis(4-benzodioxole)buta-1,3-diyne (2h)
H
1
,1-dibromo-1-alkenes bearing an electron-withdrawing
NMR (CDCl
3
, 500 MHz) δ: 6.00 (s, 4H), 6.80 (d, J=8.1
group (2j).
Hz, 2H), 6.96 (s, 2H), 7.04 (d, J=8.1 Hz, 2H).
1
5
1
1
,4-Bis(4-aminophenyl)buta-1,3-diyne (2i)
H
NMR (CDCl
3
, 500 MHz) δ: 5.71 (br, 4H), 6.52 (d, J=
Experimental section
8
.5 Hz, 4H), 7.19 (d, J=8.5 Hz, 4H).
1
13
1
6
1
H NMR and C NMR spectra were recorded with a
Bruker AM-500 spectrometer on CDCl solutions with
SiMe as an internal standard. Commercially obtained
reagents were used without further purification. Sol-
vents used were dried over 4 Å molecular sieve. All re-
actions were monitored by TLC with Huanghai GF 254
silica gel coated plates. Column chromatography was
carried out using 300—400 mesh silica gel at medium
pressure.
1
,4-Bis(4-bromophenyl)buta-1,3-diyne (2j)
H
3
, 500 MHz) δ: 7.38 (d, J=8.1 Hz, 4H),
NMR (CDCl
3
4
7
.49 (d, J=8.1 Hz, 4H).
Conclusions
In summary, we have developed a ligand-free copper-
catalyzed homocoupling protocol for the preparation of
symmetrical diynes from 1,1-dibromo-1-alkenes. The
protocol can be easily performed under mild conditions
in good to excellent yields.
Preparation of compound 2
To a sealed tube were added DMSO (2 mL),
1
,1-dibromo-1-alkenes (0.5 mmol), CuI (19 mg, 0.1
References
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stirred at 25 ℃ and the reaction was monitored by TLC.
After reaction completed, the mixture was extracted
1
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4
5
6
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1
777.
1
0
1
1
,4-Bis(4-methylphenyl)buta-1,3-diyne (2a)
H
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3
, 500 MHz) δ: 2.35 (s, 6H), 7.13 (d, J=8.0
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0
1
1
,4-Diphenylbuta-1,3-diyne (2b)
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1
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m, 4H).
1
11
1
1,4-Bis(2-methoxyphenyl)buta-1,3-diyne (2c)
H
NMR (CDCl
3
, 500 MHz) δ: 3.88 (s, 6H), 6.86—6.91 (m,
1
4
H), 7.28—7.42 (m, 4H).
7
8
9
0
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11
1
1
,4-Bis(3-methoxyphenyl)buta-1,3-diyne (2d)
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3
, 500 MHz) δ: 3.81 (s, 6H), 6.93 (dd, J=
8
7
.3, 2.3 Hz, 2H), 7.05 (s, 2H), 7.13 (d, J=7.6 Hz, 2H),
1
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1
0
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,4-Bis(4-methoxyphenyl)buta-1,3-diyne
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1
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1
3
13 Biftu, T.; Schneiders, G. E.; Stevenson, R. J. Chem. Res.,
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,4-Bis(4-benzyloxyphenyl)buta-1,3-diyne (2f)
1
H NMR (CDCl
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1
4
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14
15 Serwinski, P. R.; Lahti, P. M. Org. Lett. 2003, 5, 2099.
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,4-Bis(3,4-dimethoxyphenyl)buta-1,3-diyne (2g)
1
3
H NMR (CDCl , 500 MHz) δ: 3.88 (s, 6H), 3.90 (s,
(E1008261 Cheng, B.; Zheng, G.)
5
94
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