An efficient synthesis of diynes using (diacetoxyiodo)benzene

Article abstract of DOI:10.1016/j.jorganchem.2007.05.004

A novel and facile method for synthesis of symmetrical conjugated diynes, using (diacetoxyiodo)benzene as oxidant under palladium-catalyzed conditions is presented, in which diynes are prepared in good yields in a short period of time at room temperature.

Full text of DOI:10.1016/j.jorganchem.2007.05.004

Journal of Organometallic Chemistry 692 (2007) 3636–3639
www.elsevier.com/locate/jorganchem
An efficient synthesis of diynes using (diacetoxyiodo)benzene
a,
b
a
Jie Yan *, Jinlong Wu , Hongwei Jin
a
College of Chemical Engineering and Materials Sciences, Zhejiang University of Technology, Hangzhou 310032, Zhejiang, PR China
b
Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang, PR China
Received 9 February 2007; received in revised form 13 April 2007; accepted 1 May 2007
Available online 8 May 2007
Abstract
A novel and facile method for synthesis of symmetrical conjugated diynes, using (diacetoxyiodo)benzene as oxidant under palladium-
catalyzed conditions is presented, in which diynes are prepared in good yields in a short period of time at room temperature.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: (Diacetoxyiodo)benzene; Diyne; Homocoupling; Synthesis
1. Introduction
of 1-alkynes with DIB in the presence of catalytic amounts
of PdCl2 and CuI, the good result is in agreement with that
DIB is a good oxidizing reagent for the palladium-cata-
lyzed homocoupling of alkynes.
Diynes are very important compounds in terms of their
chemistry and the solid state properties of their homopoly-
mers [1]. The synthesis of diynes, in addition to the tradi-
tional Glaser oxidative dimerization of terminal acety-
lenes [2], they can be achieved by Pd(0)–Cu(I) catalyzed
self-coupling of terminal alkynes in the presence of chloro-
acetone [3], ethyl bromoacetate [4], allyl bromide [5] and
iodine [6], diynes were also prepared under standard Sono-
gashira cross-coupling conditions in the absence of an
obvious oxidant [7]. Because palladium-catalyzed homo-
coupling of alkynes is quick, simple, mild and environmen-
tally more benign, the research in exploring the scope of it
is still a much-sought process.
(Diacetoxyiodo)benzene (DIB) is a most important, well
investigated, and practically useful organic derivatives of
iodine (III) [8]. As a general, universal oxidizing reagent,
DIB has been widely used for the oxidation of phenols,
enolizable ketones, alkenes, alkoxyallenes and so on [9].
We investigated the oxidative coupling of isopropylidene
5-alkylmalonates using (diacetoxyiodo)benzene [10] and
now we wish to report a novel and facile method for the
synthesis of symmetrical conjugated diynes by the reaction
2. Results and discussion
2.1. The homocoupling of phenylacetylene
Initially, we mixed phenylacetylene with DIB and Et3N
in THF in the presence of catalytic amounts of PdCl2 and
CuI under N2 at room temperature, we found that the
homocoupling occurred easily and the product of diph-
enylbutadiyne was obtained in good yield in a short period
of time. Then, we investigated the reaction in air, and
found that reaction was also carried out fluently and the
same result was achieved. In order to determine the opti-
mum reaction conditions, a series of experiments were per-
formed on the homocoupling of phenylacetylene using DIB
as an oxidizing reagent, the results are summarized in
Table 1.
It is shown from Table 1 that yield of the diyne
depended on the amount of DIB used in the reaction: if
DIB was not presented or only in catalytic amounts, the
yields were poor (entries 1 and 15); however, when the
amount was raised to 0.5 molar ratio of phenylacetylene
or more, diyne was obtained in excellent yields (entries
*
Corresponding author.
E-mail address: jieyan87@hotmail.com (J. Yan).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.05.004

J. Yan et al. / Journal of Organometallic Chemistry 692 (2007) 3636–3639
3637
Table 1
The results of the homocoupling of phenylacetylenea
PdCl2 , CuI, Et3N, THF
PhI(OCOCH3)2
Ph
Ph
Ph
Entry
DIB (equiv.)
Catalyst (2%)
Base (1.1 equiv.)
Solvent
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
a
0.10
0.35
0.5
1.0
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
PdCl2
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et2NH
i-Pr2NH
NaHCO3
Na2CO3
Et3N
THF
THF
THF
THF
THF
DMF
CH3CN
H2O
THF
THF
THF
THF
THF
THF
THF
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
20
33
73
88
91
90
82
72
67
88
90
65
71
27
12
37
CuI
CuI
Et3N
Et3N
0.5
2.5
PdCl2
Reaction conditions: 1.0 mmol of phenylacetylene, 0.6 mmol of DIB, 1.1 mmol of Et3N, PdCl2 (2.0 mol%), CuI (2.0 mol%), THF (3 mL) at RT.
Isolate yields.
b
3–5). As a suitable solvent, THF was the most preferred
from the dialkynylpalladium, which was derived from
1-alkyne and PdCl2 in the presence of CuI and Et3N.
DIB was used to regenerate the Pd(II) catalyst by oxida-
tive addition from the Pd(0) formed in the catalytic
cycle, making the second reductive elimination possible
and eventually converting all alkynes to the correspond-
ing diynes.
In conclusion, we have successfully developed a novel
and facile method for synthesis of symmetrical conjugated
diynes by palladium-catalyzed homocoupling of terminal
alkynes, using DIB to initiate the reaction. It has some
advantages such as mild reaction conditions, simple proce-
dure and good yields. Furthermore, the scope of palla-
dium-catalyzed homocoupling of alkynes could be
extended. Further investigation of the reactions will be
reported in due course.
(entries 5–8). Organic bases were better than inorganic
bases, and the bases Et3N, Et2NH and i-Pr2NH were
almost effective (entries 5, 9 and 10). Without CuI, the
homocoupling occurred slowly and a poor yield of diyne
was afforded (entry 13). In the absence of PdCl2, the reac-
tion also yielded a small amount of diyne (entry 14). We
also investigated the coupling reaction using Pd(OAc)2
instead of PdCl2, the same result was got; when
PdCl2(PPh3)2 was used, the reaction was somewhat slower
and the yield in 0.5 h was lower compared with PdCl2.
2.2. The homocoupling of terminal alkynes
Under the optimum reaction conditions, the homocou-
pling of a series of terminal alkynes using DIB as oxidizing
reagent and Et3N as a base in the presence of catalytic
amounts of PdCl2 and CuI was investigated, the good
results are summarized in Table 2. It is shown that the
homocoupling of terminal aromatic alkynes gave diynes
in excellent yields (entries 1–3); while when aliphatic alky-
nes were used, the yields were somewhat lower (entries 4–6)
compared with aromatic alkynes and the homocoupling
needed to prolong the reaction time due to the weaker acid-
ity of the acetylenitic proton [11]. Using this protocol, the
dimerization of 2-methyl-3-butyne-2-nol 1g gave diyne 2g
in 62% yield after 3 h. However, switching to ethyl propio-
late resulted in no reaction [7].
3. Experimental
3.1. General
IR spectra were recorded on a FT-170 SX instrument,
1H NMR spectra were measured on a Broker AM-400
FT-NMR spectrometer, and Mass spectra were determined
on HP5989A mass spectrometer. All terminal alkynes are
commercially available.
3.2. The homocoupling of terminal alkynes
2.3. Mechanistic consideration
A typical reaction procedure: to a mixture of phenyl-
acetylene (1.0 mmol), DIB (0.6 mmol), Et3N (1.1 mmol),
PdCl2 (2.0 mol%) and CuI (2.0 mol%), THF (3 mL) was
added. The mixture was stirred at room temperature for
Scheme 1 illustrates the proposed mechanism for the
homocoupling of alkynes via a reductive elimination

3638
J. Yan et al. / Journal of Organometallic Chemistry 692 (2007) 3636–3639
Table 2
3.3. Diphenylbutadiyne (2a) [6]
a
The results of the homocoupling of alkynes
PdCl2 , CuI, Et3N, THF
1H NMR (CDCl3): d = 7.32–7.36 (m, 6H), 7.50–7.55 (m,
4H); IR (film): m = 3049, 2978, 2145, 1261, 730 cmÀ1; MS
(70 eV, EI) m/z (%): 202 (M+, 100).
R
R
R
PhI(OCOCH3)2
2
1
b
Entry
1
Alkyne
Diyne
Time (h)
0.5
Yield (%)
90
2a
Ph
1a
3.4. Bis(4-methylphenyl)butadiyne (2b) [12]
1H NMR (CDCl3): d = 2.39 (s, 3H), 7.25 (d,
J = 11.0 Hz, 4H), 7.42 (d, J = 11.0 Hz, 4H); IR (film):
m = 3060, 2988, 2133, 1267, 751 cmÀ1; MS (70 eV, EI)
m/z (%): 230 (M+, 100).
2
3
4
5
6
7
2b
2c
2d
2e
2f
0.5
0.5
1.0
1.0
1.0
3.0
87
88
70
77
74
62
p-CH3-C6H4-
1b
p-C2H5-C6H4-
1c
3.5. Bis(4-ethylphenyl)butadiyne (2c) [4]
1H NMR (CDCl3): d = 1.23 (t, J = 7.6 Hz, 6H), 2.65 (q,
J = 7.6 Hz, 4H), 7.14 (d, J=8.0 Hz, 4H), 7.42 (d,
J = 8.0 Hz, 4H); IR (film): m = 3051, 2991, 2152, 1268,
743 cmÀ1; MS (75 eV, EI) m/z (%): 258 (M+, 100).
n-C4H9-
1d
n-C5H11-
1e
3.6. 5,7-Dodecadiyne (2d) [12]
1H NMR (CDCl3): d = 0.90 (t, J = 7.2 Hz, 6H), 1.36–
1.44 (m, 4H), 1.45–1.54 (m, 4H), 2.24 (t, J = 6.8 Hz, 4H);
IR (film): m = 2966, 2140, 1259, 736 cmÀ1; HRMS (EI)
calcd. for C12H18 M+ 162.1409, found: 162.1401.
n-C6H13-
1f
2g
Me
3.7. 6,8-Tetradecadiyne (2e) [12]
Me
OH
1H NMR (CDCl3): d = 0.89 (t, J = 7.2 Hz, 6H), 1.24–
1.40 (m, 8H), 1.48–1.55 (m, 4H), 2.24 (t, J = 7.2 Hz, 4H);
IR (film): m = 2971, 2152, 1256, 744 cmÀ1; HRMS (EI)
calcd. for C14H22 M+ 190.1722, found: 190.1712.
1g
a
Reaction conditions: 1.0 mmol of alkyne, 0.6 mmol of DIB, 1.1 mmol
of Et3N, PdCl2 (2.0 mol%), CuI (2.0 mol%), THF (3 mL) at RT.
b
Isolated yields.
3.8. 7,9-Hexadecadiyne (2f) [13]
1H NMR (CDCl3): d = 0.89 (t, J = 7.2 Hz, 6H), 1.18–
1.40 (m, 12H), 1.45–1.56 (m, 4H), 2.22 (t, J = 6.8 Hz,
4H); IR (film): m = 2982, 2133, 1263, 741 cmÀ1; HRMS
(EI) calcd. for C16H26 M+ 218.2035, found: 218.2022.
R
R
Pd (0)
PhI(OCOCH3)2
3.9. 2,7-Dimethylocta-3,5-diyne-2,7-diol (2g) [14]
PhI
R
R
Pd
1H NMR (CDCl3): d = 1.37 (s, 12H), 2.52 (s, 2H); IR
(film): m = 3279, 3211, 2924, 2120, 1216, 1170 cmÀ1; MS
(75 eV, EI) m/z (%): 166 (M+, 1.2), 43 (100).
Pd(OAc)2
Et3N HCl
R
CuI, Et3N
PdCl2
CuI, Et3N
Acknowledgement
R
Et3N HOAc
Scheme 1.
Financial support from the Natural Science Foundation
of China (Project 20672100) is greatly appreciated.
References
0.5 h and then separated by a silica gel plate using petro-
leum ether as developer, the product of diphenylbutadiyne
(2a) was afforded in 90% yield.
[1] V.D. Hunstman, in: S. Patai (Ed.), The Chemistry of Carbon–Carbon
Triple Bond, Wiley-Interscience, London, 1978, p. 553.

J. Yan et al. / Journal of Organometallic Chemistry 692 (2007) 3636–3639
3639
[2] (a) A.S. Has, J. Org. Chem. 27 (1962) 3320;
(b) M.G. Mkryan, N.A. Papazyan, E.S. Voskayan, I.V. Khachatur-
yan, Arm. Khim. Zh. 19 (1966) 938;
Compounds, VCH Publishers, New York, 1999, p. 359 (Chapter 13);
M. Ochiai, J. Organomet. Chem. 611 (2000) 494;
(e) T. Okuyama, Acc. Chem. Res. 35 (2002) 12;
(f) V.V. Grushin, Chem. Soc. Rev. 29 (2000) 315.
[9] (a) O. Prakash, N. Saini, P.K. Sharma, Synlett (1994) 221;
(b) P. Wipf, Y. Kim, P.C. Fritch, J. Org. Chem. 58 (1993) 7195;
(c) H. Hara, T. Inoue, H. Nakamora, M. Endoh, O. Hoshino,
Tetrahedron Lett. 34 (1992) 6419;
(c) E. Valenti, M.A. Pericas, F. Serratosa, J. Am. Chem. Soc. 112
(1990) 7405;
(d) K. Maruyama, H. Tsukube, T. Araki, J. Polym. Sci., Polym.
Chem. Ed. 18 (1980) 749;
(e) Y. Liao, R. Fathi, Z. Yang, Org. Lett. 5 (2003) 909.
[3] R. Rossi, A. Carpita, C. Bigelli, Tetrahedron Lett. 26 (1985) 523.
[4] A. Lei, M. Srivastava, X. Zhang, J. Org. Chem. 67 (2002) 1969.
[5] M. Vlasa, I. Ciocan-Tarta, F. Margineanu, I. Oprean, Tetrahedron
52 (1996) 1337.
(d) R.M. Moriarty, T.E. Hopkins, R.K. Vaid, B.K. Vaid, S.G. Levy,
Synthesis (1992) 847;
(e) A. Pelter, S.M.A. Elgendy, J. Chem. Soc., Perkin Trans. 1 (1993)
1891;
[6] Q. Liu, D.J. Burton, Tetrahedron Lett. 38 (1997) 4371.
[7] I.J.S. Fairiamb, P.S. Bauerlein, L.R. Marrison, J.M. Dickinson,
Chem. Commun. (2003) 632.
[8] (a) A. Varvoglis, Hypervalent Iodine in Organic Synthesis, Academic
Press, London, 1997;
(f) R.M. Mariarty, R. Penmasta, A.K. Awasthi, I. Prakash, J. Org.
Chem. 53 (1988) 6124.
[10] J. Yan, Li. Zhong, Z. Chen, J. Org. Chem. 56 (1991) 461.
[11] L. Brandsma, H.D. Verkruijsse, B. Walda, Synth. Commun. 21
(1991) 137.
A. Varvoglis, Tetrahedron 53 (1997) 1179;
[12] S.V. Damle, D. Seomoon, P.H. Lee, J. Org. Chem. 68 (2003) 7085.
[13] R. Takeuchi, Y. Tsuji, M. Fujita, T. Kondo, Y. Watanabe, J. Org.
Chem. 54 (1989) 1831.
(b) P.J. Stang, V.V. Zhdankin, Chem. Rev. 96 (1996) 1123;
(c) V.V. Zhdankin, P.J. Stang, Chem. Rev. 102 (2002) 2523;
(d) M. Ochiai, in: K. Akibe (Ed.), Chemistry of Hypervalent
[14] R.C. Paul, S. Braverman, Synth. Commun. 29 (1999) 2629.