Copper powder-mediated homocoupling reactions of iodoacetylenes to synthesize symmetrical 1,3-butadiynes

Article abstract of DOI:10.1080/00397910802026568

A new route to synthesize symmetrical 1,3-butadiynes from iodoacetylenes in the presence of copper powder and pyridine was developed. Moderate to excellent yields were obtained through an efficient and simple process involving the copper powder without any further activation. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910802026568

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Copper Powder–Mediated
Homocoupling Reactions of
Iodoacetylenes to Synthesize
Symmetrical 1,3-Butadiynes
Song Xue a , Ling-Guo Meng b & Qing-Xiang Guo b
a Department of Applied Chemistry , Tianjin
University of Technology , Tianjin, China
b Department of Chemistry , University of Science
and Technology of China , Hefei, China
Published online: 18 Aug 2008.
To cite this article: Song Xue , Ling-Guo Meng & Qing-Xiang Guo (2008) Copper
Powder–Mediated Homocoupling Reactions of Iodoacetylenes to Synthesize
Symmetrical 1,3-Butadiynes, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 38:13, 2243-2251, DOI:
10.1080/00397910802026568
To link to this article: http://dx.doi.org/10.1080/00397910802026568
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Synthetic Communications1, 38: 2243–2251, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802026568
Copper Powder–Mediated Homocoupling
Reactions of Iodoacetylenes to Synthesize
Symmetrical 1,3-Butadiynes
Song Xue,1 Ling-Guo Meng,2 and Qing-Xiang Guo,2
1Department of Applied Chemistry, Tianjin University of Technology,
Tianjin, China
2Department of Chemistry, University of Science and Technology of China,
Hefei, China
Abstract: A new route to synthesize symmetrical 1,3-butadiynes from iodoacety-
lenes in the presence of copper powder and pyridine was developed. Moderate to
excellent yields were obtained through an efficient and simple process involving
the copper powder without any further activation.
Keywords: 1,3-Butadiynes;
Iodoacetylenes
Copper
powder;
Homocoupling
reaction;
1,3-Butadiynes have been important intermediates in organic synthesis,[1]
pharmaceuticals,[2] polymes,[3a,3b] and natural products.[3c] Numerous
synthetic methods for their preparation have been developed. There are
several Pd(0)-Cu(I)–catalyzed cross-coupling reactions, such as dimeri-
zation of terminal alkynes[4] or dimerization of alkynyl halides with
terminal alkynes.[5] Alkynylstannanes,[6a] alkynylboronates,[6b] and alky-
nylsilanes[7] were also used to give 1,3-butadiynes. Damle and coworker’s
described an efficient synthetic method of 1,3-butadiynes from iodoacety-
lenes in the presence of Pd(PPh3)4 in N,N-dimethylformamide (DMF);
however, Pd(PPh3)4 was expensive and sensitive to air.[8]
Another efficient and useful method for preparing 1,3-butadiynes was
observed by Carl Glaser in 1869, who got 1,3-butadiynes from terminal
Received October 5, 2007
Address correspondence to Song Xue, Department of Applied Chemistry,
Tianjin University of Technology, Tianjin 300191, China. E-mail: xuesong@
ustc.edu.cn
2243

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2244
S. Xue, L.-G. Meng, and Q.-X. Guo
acetylenes with CuCl in the presence of NH4OH.[9] Subsequently, many
improved methods were developed to give 1,3-butadiynes.[10] Especially
in the 1960s, Hay reported that terminal acetylenes could be transformed
to 1,3-butadiynes at room temperature with oxygen or air by CuCl–
pyridine or CuCl–tetramethylethylenediamine (TMEDA).[11] In short, a
variety of cupric salts in the presence of organic bases have been
employed in the past several decades.[12] However, moderate yields were
obtained in most cases. Therefore, a simple and efficient methodology
for synthesis of 1,3-butadiynes is of interest.
In 1901, Ullmann discovered that copper powder catalyzed the coup-
ling of aromatic halides to produce biaryls,[13] which is an effective
method for the construction of sp2-sp2 C-C bonds. The homocoupling
of alkyl halides to construct sp3-sp3 C-C bonds utilizing a highly acti-
vated form of zero-valent copper has also been reported.[14] However,
to the best of our knowledge, copper powder used to construct sp-sp
C-C bonds has received relatively little attention.[15] Herein, we report
a new route to synthesize 1,3-butadiynes from iodoacetylenes in the
presence of copper powder and pyridine under mild reaction conditions.
EXPERIMENTAL
Our investigation began with an effort to optimize reaction conditions for
the coupling of iodoacetylenes. 1-(2-Iodoethyny)benzene was chosen as
Table 1. Coupling of iodoacetylenes with copper powder
Entry
Base
Time (h)
2a yield (%)a
1
2
3
Pyridine
DMAP
PPh3
6
6
8
98
98
30
4
5
6
7b
8c
9d
Et3N
K2CO3
None
Pyridine
Pyridine
Pyridine
3
6
6
6
12
12
Trace
Trace
—
96
49
47
aIsolated yields.
bReactions were performed under nitrogen.
cCopper powder (0.5 eq.) and pyridine (0.5 eq.) were used.
dCopper powder (0.5 eq.) and pyridine (1.2 eq.) were used.