Palladium-catalyzed self-coupling reaction of terminal alkynes in the presence of p-chloranil: A practical method for the synthesis of triethynylethenes

Article abstract of DOI:10.1055/s-2006-950416

Pd-catalyzed reaction of aliphatic-1-alkynes in the presence of p-chloranil afforded triethynylethenes as exclusive self-coupling products in good yields. On the other hand, diynes were obtained when aromatic alkynes were used. Georg Thieme Verlag Stuttga

Full text of DOI:10.1055/s-2006-950416

2
454
LETTER
Palladium-Catalyzed Self-Coupling Reaction of Terminal Alkynes in the
Presence of p-Chloranil: A Practical Method for the Synthesis of
Triethynylethenes
P
C
alladium-Cataly
h
ze
d
Self-Cou
a
pling Rea
c
o
tion of Terminal
A
C
lkynes hen, Zhezhe Ai, Jie Lin, Xiaoyin Hong, Chanjuan Xi*
Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University,
Beijing 100084, P. R. of China
Fax +86(10)62618239; E-mail: cjxi@tsinghua.edu.cn
Received 18 May 2006
continuing program on the application of quinones as
Abstract: Pd-catalyzed reaction of aliphatic-1-alkynes in the pres-
13
oxidants in organic synthesis, herein we report a Pd(0)-
Cu(I)-catalyzed reaction of aliphatic-1-alkynes 4 in the
presence of p-chloranil, to afford triethynylethenes 3 as
the exclusive self-coupling product (Scheme 1).
ence of p-chloranil afforded triethynylethenes as exclusive self-cou-
pling products in good yields. On the other hand, diynes were
obtained when aromatic alkynes were used.
Key words: coupling reaction, alkyne, quinone, triethynylethene,
palladium catalyst
R
Pd(PPh3)4, CuCl, THF
R
R
Interest in conjugated organic materials has grown be-
cause of their potential applications in molecular wires,
switches, and other components for molecular electronics,
p-chloranil, Et3N, r.t.
4
R = aliphatic group
3
R
R
nonlinear optics (NLO), organic conductors, and light- Scheme 1
emitting diodes. With regard to acetylenic scaffolding,5
1–4
derivatives of 1,2-diethynylethene (1, DEE, hex-3-ene-
Our method has similarities to a related process reported
by Rossi and coworkers. The reaction of aliphatic 1-
1
,5-diyne) and tetraethynylethene (2, TEE, 3,4-diethynyl-
7a
hex-3-ene-1,5-diyne) have provided a unique class of p-
alkynes
with
tetrakis(triphenylphosphan)palladium
6
conjugated building blocks (Figure 1). The interesting
[
Pd(PPh ) ], copper iodide, and triethylamine in benzene
3
4
properties of these compounds have resulted in an array of
modifications specially directed to oligomerization/poly-
in the presence of chloroacetone afforded mixtures of 1,4-
dialkyl-l,3-butadiynes (30–50%) and 3-ethynylhexa-3-
en-1,5-diyne (28–50%). However, our procedure gave 3-
ethynylhexa-3-en-1,5-diyne in excellent yields when ali-
phatic 1-alkynes were used. Only trace amount of 1,4-di-
alkyl-1,3-butadiynes was observed by GC-MS. During
the course of our study, we examined other oxidants such
as 1,4-benzoquinione, 2,3-dichloronaphthalene-1,4-di-
one, and 4,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,2-
dicarbonitrile (DDQ) and p-chloranil worked as a good
oxidant. The results are listed in Table 1. For example, the
reaction of alkynes 4a with Pd(PPh ) , copper chloride,
4
c
merization. It is surprising, however, that synthetic
reports and structural studies of the other module, tri-
ethynylethene (3, 3-ethynylhexa-3-en-1,5-diyne), is
7
rarely reported.
(E)-1
(Z)-1
2
3
3
4
Figure 1
Table 1 Pd(0)-Catalyzed Self-Coupling Reaction of Hept-1-yne
with Oxidants
The palladium-catalyzed coupling reaction has proved to
n-C5H11
be an extremely powerful tool to construct carbon-carbon
8
Pd(PPh ) , CuCl, THF
n-C5H11
bonds. In a typical Pd-catalyzed process, oxidative cou-
3 4
n-C5H11
pling of terminal alkynes occurred in the presence of oxi-
oxidant, Et3N, r.t.
7
a
9
10
4a
dants, such as chloroacetone, bromoacetate, iodine,
n-C H
5 11
n-C H
5
11
3a
1
1
12
allyl bromide and O2. These reactions resulted in the
corresponding symmetrical 1,3-diynes in good yields. It
had been reported earlier that reaction of terminal alkynes
in the presence of chloroacetone (as oxidant) afforded 1,3-
Entry
Oxidant
Yield (%)
trace
32
1
2
3
4
5
–
7
a
diynes together with triethynylethenes. As a part of our
1,4-benzoquinione,
2,3-dichloronaphthalene-1,4-dione
trace
trace
90
SYNLETT 2006, No. 15, pp 2454–2458
1
8
.0
9
.2
0
0
6
Advanced online publication: 08.09.2006
DOI: 10.1055/s-2006-950416; Art ID: W10406ST
DDQ
p-chloranil
©
Georg Thieme Verlag Stuttgart · New York

LETTER
Palladium-Catalyzed Self-Coupling Reaction of Terminal Alkynes
2455
and triethylamine in tetrahydrofuran in the presence of Furthermore, we conducted the reaction using hept-1-yne
1
4
p-chloranil afforded 3a in 90% yield.
(4a) and hex-1-yne (4c) in one pot under the optimized
conditions as shown in Scheme 3. Several compounds, in-
cluding homocoupling products (peaks A and E) and
cross-coupling products (peaks B-D) were observed by
GC-MS, and the results shown in Figure 2. The structures
of the peaks are illustrated in Table 4.
Under the optimized conditions, the self-coupling reac-
tion of various terminal alkynes 4 was next examined and
1
4
the results are shown in Table 2.
To extend the scope of the reaction, we next investigated
the aromatic 1-alkynes. However, under the optimized
conditions, aromatic 1-alkynes afforded good to excellent
yields of diaryldiynes 5 (Table 3, entries 1–3). No for-
mation of any triethynylethenes 3 was observed. In the
Based on the above results, we proposed the reaction
mechanism as follows. Pd(0) species reacted with oxidant
to generate Pd(II). The alkynylcopper intermediate 7 is
formed from the reaction of a terminal alkyne and copper
chloride in the presence of triethylamine and it undergoes
double transmetallation with Pd(II). The transmetallation
yields the dialkynylpalladium intermediate 8. One of the
triple bonds in intermediate 8 inserts into another C-Pd
bond to form intermediate 9, which then undergoes dou-
1
5
1
5d
reaction of 1-ethynylcyclohex-1-ene, 5d was also pro-
vided in 72% yield (Table 3, entry 4).
To investigate the reaction mechanism, we conducted a
similar reaction of tetradeca-6,8-diyne (6) together with
hept-1-yne (4a) under the optimized conditions
Scheme 2). Product 3a was observed by GC-MS. No
formation of cross-coupling product was observed. That
means the diyne was not an intermediate.
(
2
ble reductive elimination to form sp –sp coupling product
3
and Pd(0) (Scheme 4).
Table 2 Pd(0)-Catalyzed Self-Coupling Reaction of 1-Alkynes
Entry
1
R
Product
Yield (%)a
90
n-C5H11
n-C5H11
n-C5H11
4
a
n-C5H11
n-C6H13
n-C5H11
3
3
a
n-C6H13
n-C6H13
2
3
4
81
65
52
4
b
n-C6H13
n-C4H9
n-C6H13
b
n-C4H9
n-C4H9
4
c
n-C4H9
n-C3H7
n-C4H9
3
c
n-C3H7
n-C3H7
4
d
n-C3H7
n-C3H7
3
d
Ph
Ph
PhCH2CH2
5
68
Ph
4
e
Ph
3
e
Cl
Cl
Cl(CH2)3
Cl
79b
6
4
f
Cl
3
f
a
Isolated yield.
b
Pd(PPh ) Cl was used as catalyst.
3
2
2
Synlett 2006, No. 15, 2454–2458 © Thieme Stuttgart · New York

2
456
C. Chen et al.
LETTER
Table 3 Pd(0)-Catalyzed Homocoupling Reaction of 1-Alkynes
Entry
1
R
Product
Yield (%)a
84
79
5
5
a
Me
Me
2
3
Me
b
82
72
5
c
4
5
d
a
Isolated yield.
n-C4H9
n-C4H9
Pd(PPh3)4, CuCl, THF
6
+
3a
+
6
n-C5H11
p-chloranil, Et3N, r.t.
4a
Scheme 2
n-C5H11
Pd(PPh3)4, CuCl, THF
4a
+
Peak A + Peaks B + Peaks C
Peaks D + Peaks E
p-chloranil, Et3N, r.t.
n-C4H9
+
4c
Scheme 3
Figure 2 GC-MS chart of the cross-coupling reaction
Table 4 Cross-Coupling Reaction of Hept-1-yne (4a) and Hex-1-yne (4c)
Peak
Time (min)
MW
Product
n-C4H9
n-C4H9
A
14.77
324
n-C4H9
n-C4H9
n-C5H11
n-C4H9
n-C H
n-C H
4
9
5
11
n-C4H9
4 9
n-C H
n-C4H9
n-C4H9
n-C H
B
15.24
338
4
9
n-C4H9
n-C H
n-C H
4
9
4
9
n-C5H11
4 9
n-C H
n-C4H9
n-C H
5
11
Synlett 2006, No. 15, 2454–2458 © Thieme Stuttgart · New York

LETTER
Palladium-Catalyzed Self-Coupling Reaction of Terminal Alkynes
2457
Table 4 Cross-Coupling Reaction of Hept-1-yne (4a) and Hex-1-yne (4c) (continued)
Peak
Time (min)
MW
352
Product
n-C5H11
n-C5H11 n-C4H9
n-C5H11 n-C5H11
n-C4H9
n-C4H9
n-C4H9
n-C5H11
C4H9
n-C5H11
n-C4H9
n-C4H9
C
15.65
n-C4H9
n-C5H11 n-C4H9
n-C4H9 n-C5H11
n-C5H11
n-C5H11
n-C4H9
n-C4H9
n-C5H11
n-C5H11
n-C5H11
n-C5H11 n-C4H9
n-C5H11
n-C4H9
n-C5H11
n-C5H11
n-C5H11
n-C5H11
n-C4H9
D
16.12
366
n-C5H11
n-C5H11
n-C5H11
n-C5H11
n-C4H9
n-C5H11
n-C5H11
n-C5H11
E
16.58
380
n-C5H11
n-C5H11
Pd(0)
R
References and Notes
3
[
O]
(
1) (a) Nielsen, M. B.; Diederich, F. Chem. Rev. 2005, 105,
R
Pd
Pd
1837. (b) Salaneck, W. R.; Lundström, I.; Rånby, B.
Pd(II)
CuCl
R
Conjugated Polymers and Related Materials; Oxford
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Elsenbaumer, R. L.; Reynold, J. R. Handbook of Conducting
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9
R
R
R
Et3N
Pd
R
Cu 7
R
(d) Kraft, A.; Grimsdale, A. C.; Holmes, A. B. Angew.
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Scheme 4
(
(
2) (a) Petty, M. C.; Bryce, M. R.; Bloor, D. Introduction to
Molecular Electronics; Edward Arnold: London, 1995.
In summary, we have developed a Pd(0)-Cu(I)-catalyzed
self-coupling reaction of terminal alkynes in the presence
of p-chloranil, to afford triethynylethenes. This simple
and efficient process may be useful in the synthesis of new
organic materials with interesting electronic and optical
applications. Studies are in progress in order to clarify the
detailed mechanism and the scope.
(
b) Bumm, L. A.; Arnold, J. J.; Cygan, M. T.; Dunbar, T. D.;
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Acknowledgment
(
c) Tykwinski, R. R.; Gubler, U.; Martin, R. E.; Diederich,
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451.
This work was supported by the National Natural Science Founda-
tion of China (20372041) (20572058) and Beijing Department of
Education (XK100030514).
4
Synlett 2006, No. 15, 2454–2458 © Thieme Stuttgart · New York

2
458
C. Chen et al.
LETTER
(
5) (a) Scott, L. T.; Cooney, M. J. In Modern Acetylene
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2
Na SO and concentrated under vacuum to yield the crude
2
4
product. The crude product was purified by flash
chromatography on silica gel using PE as the eluent.
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liquid (90% isolated yield).
1998, 1055. (d) Youngs, W. J.; Tesseir, C. A.; Bradshaw, J.
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1
(
f) Haley, M. M.; Park, J. J.; Brand, S. C. Top. Curr. Chem.
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3
1999, 201, 81. (g) Bunz, U. H. F. Top. Curr. Chem. 1999,
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1
3
201, 131. (h) Tour, J. M. Acc. Chem. Res. 2000, 33, 791.
3
(i) Hopf, H. Classics in Hydrocarbon Chemistry; Wiley-
20.0, 22.3, 22.5, 27.9, 28.4, 28.5, 28.6, 31.1, 31.4, 34.6, 77.8,
79.3, 81.0, 92.5, 96.9, 100.9, 109.3, 138.1. GC-MS: m/z =
380. HRMS: m/z calcd for C H : 380.3443; found:
VCH: Weinheim Germany, 2000. (j) Laskoski, M.; Roidl,
G.; Smith, M. D.; Bunz, U. H. F. Angew. Chem. Int. Ed.
2
8
44
2
2
2
001, 40, 1460. (k) Nielsen, M. B.; Diederich, F. Synlett
002, 544. (l) Nielsen, M. B.; Diederich, F. Chem. Rec.
002, 2, 189. (m) Camacho, D. H.; Saito, S.; Yamamoto, Y.
380.3441.
9-Hexyl-10-(oct-1-ynyl)octadeca-9-en-7,11-diyne (3b)
1
H NMR (CDCl /TMS, 300 MHz): d = 0.85–0.89 (m, 12 H),
3
J. Am. Chem. Soc. 2002, 124, 924.
1.28 (d, J = 2.7 Hz, 16 H), 1.34–1.59 (m, 16 H), 2.33–2.42
(m, 8 H). C NMR (CDCl /TMS, 75 MHz): d = 14.0, 19.7,
1
3
(
(
6) (a) Tykwinski, R. R.; Diederich, F. Liebigs Ann./Recl. 1997,
3
649. (b) Diederich, F. Chem. Commun. 2001, 219.
20.0, 22.5, 28.1, 28.5, 28.7, 28.7, 28. 8, 31.3, 31.4, 31.7,
34.6, 77.6, 79.1, 80.8, 92.5, 96.9, 100.9, 109.1, 138.1. GC-
MS: m/z = 436. HRMS: m/z calcd for C H : 436.4069;
7) (a) Rossi, R.; Carpita, A.; Bigelli, C. Tetrahedron Lett. 1985,
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2
52
213. (c) Andersson, A. S.; Qvortrup, K.; Torbensen, E. R.;
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Mayer, J.-P.; Gisselbrecht, J.-P.; Boudon, C.; Gross, M.;
Kadziola, A.; Kilså, K.; Nielsen, M. B. Eur. J. Org. Chem.
7-Butyl-8-(hex-1-ynyl)tetradeca-7-en-5,9-diyne (3c)
1
H NMR (CDCl /TMS, 300 MHz): d = 0.86–0.93 (m, 12 H),
3
1
3
2
005, 3600.
8) (a) Reiser, O. Angew. Chem. Int. Ed. 2006, 45, 2838.
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005, 38, 413. (c) Nicolaou, K. C.; Bulger, P. G.; Sarlah, D.
1.24–1.59 (m, 16 H), 2.34–2.43 (m, 8 H). C NMR (CDCl3/
TMS, 75 MHz): d = 13.5, 13.5, 13.6, 13.8, 19.30, 19.4, 21.9,
22.2, 30.3, 30.6, 30.7, 30.8, 34.3, 77.7, 79.2, 80.9, 92.3, 96.8,
100.8, 109.1, 138.0. GC-MS: m/z = 324. HRMS: m/z calcd
for C H : 324.2817; found: 324.2815.
(
(
2
Angew. Chem. Int. Ed. 2005, 44, 4442. (d) Zeni, G.; Braga,
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2
4
36
6-(Pent-1-ynyl)-7-propyldodeca-6-en-4,8-diyne (3d)
1
(e) Culkin, D. A.; Hartwig, J. F. Acc. Chem. Res. 2003, 36,
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3
234. (f) Negishi, E.; Anastasia, L. Chem. Rev. 2003, 103,
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(m, 8 H). C NMR (CDCl /TMS, 75 MHz): d = 13.4, 13.6,
1
3
3
21.5, 21.6, 21.7, 22.0, 36.6, 77.8, 79.3, 81.0, 92.3, 96.8,
100.7, 109.2, 137.9. GC-MS: m/z = 268. HRMS: m/z calcd
for C H : 268.2191; found: 268.2194.
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2
0
28
5-Phenethyl-1,10-diphenyl-6-(4-phenylbut-1-ynyl)deca-
5-en-3,7-diyne (3e)
1
H NMR (CDCl /TMS, 300 MHz): d = 7.08–7.28 (m, 20 H),
3
1
3
2.57–2.90 (m, 16 H). C NMR (CDCl /TMS, 75 MHz): d =
3
(
9) Lei, A.; Srivastava, M.; Zhang, X. J. Org. Chem. 2002, 67,
22.0, 22.0, 22.3, 34.4, 35.0, 35.2, 35.2, 36.5, 78.1, 79.6, 81.4,
92.4, 96.8, 100.9, 109.7, 126.0, 126.3, 126.4, 128.3, 128.4,
128.5, 128.5, 137.2, 140.5, 140.6, 140.7, 141.5. HRMS:
m/z calcd for C H : 516.2817; found: 516.2820.
1969.
(
(
10) Liu, Q.; Burton, D. J. Tetrahedron Lett. 1997, 38, 4371.
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Tetrahedron 1996, 52, 1337.
4
0
36
1,12-Dichloro-6-(5-chloropent-1-ynyl)-7-(3-chloro-
(
(
(
12) Herrmann, W. A.; Bohm, V. P. W.; Gstottmayr, C. W. K.;
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propyl)dodeca-6-en-4,8-diyne (3f)
1
H NMR (CDCl /TMS, 300 MHz): d = 1.95–2.08 (m, 8 H),
3
1
3
2.52–2.68 (m, 8 H), 3.52–3.75 (m, 8 H). C NMR (CDCl /
3
TMS, 75 MHz): d = 17.0, 17.2, 17.4, 31.2, 31.3, 31.8, 43.6,
43.6, 43.7, 44.3, 77.9, 79.7, 81.2, 91.2, 96.1, 99.7, 110.2,
136.5. GC-MS: m/z = 408. HRMS: m/z calcd for C H Cl :
20
24
4
14) Typical Reaction Procedure and Spectroscopic Data: To
a solution of Pd(PPh ) (40 mg, 3.5 mmol%), CuCl (2 mg,
404.0632; found: 404.0636.
(15) NMR data for 5a-d were in accordance with literature
3
4
0
.5 mmol%), 1-heptyne (525 mL, 4.0 mmol) in THF (6 mL),
values: (a) Organ, M. G.; Ghasemi, H.; Valente, C.
p-chloranil (1.0 mmol) and Et N (2.6 mmol, 0.4 mL) were
Tetrahedron 2004, 60, 9453. (b) Damle, S. V.; Seomoon,
3
added under a N atmosphere. The mixture was allowed to
stir at r.t. for 12 h, and quenched with 3 N HCl. The resulting
D.; Lee, P. H. J. Org. Chem. 2003, 68, 7085. (c)Rodríguez,
J. G.; Tejedor, J. L. Tetrahedron 2005, 61, 3033. (d)Loupy,
A.; Meyer, G.; Tchoubar, B. Tetrahedron 1978, 34, 1323.
2
solution was extracted with Et O and washed with a sat.
2
Synlett 2006, No. 15, 2454–2458 © Thieme Stuttgart · New York