Zirconocene-promoted coupling reaction of terminal acetylenes to geminal enediynes in the presence of p-chloranil

Article abstract of DOI:10.1016/j.jorganchem.2007.04.028

Reaction of alkynyllithium with zirconocene dichloride in the presence of quinones afforded zirconoenediynes in good yields. Treatment of the zirconoenediyne with p-chloranil in the presence of CuCl afforded 1,1,4,4-tetraethynyl-1,3-diene in good yield. I

Full text of DOI:10.1016/j.jorganchem.2007.04.028

Journal of Organometallic Chemistry 692 (2007) 4612–4617
www.elsevier.com/locate/jorganchem
Zirconocene-promoted coupling reaction of terminal acetylenes
to geminal enediynes in the presence of p-chloranil
*
Chanjuan Xi , Yuanyuan Liu, Xiaoyu Yan, Chao Chen
Key Lab of Organic Optoelectronics & Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University,
Beijing 100084, China
Received 23 March 2007; received in revised form 18 April 2007; accepted 20 April 2007
Available online 25 April 2007
Dedicated to Professor Gerhard Erker on the occasion of his 60th birthday.
Abstract
Reaction of alkynyllithium with zirconocene dichloride in the presence of quinones afforded zirconoenediynes in good yields. Treat-
ment of the zirconoenediyne with p-chloranil in the presence of CuCl afforded 1,1,4,4-tetraethynyl-1,3-diene in good yield. In the pres-
ence of CuCl and/or Pd(PPh3)4, the zirconoenediynes could be transformed into various enediyne derivatives through coupling reaction
with electrophiles.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Coupling reactions; Alkynes; Zirconium; Quinones; Enediynes
1. Introduction
found [11]. In a typical process, the carbon–carbon bond
formation was reported by Negishi et al. using zirconate
complex Li[Cp2Zr(C„CR)3] [12,13]. Three equivalents of
LiC„CPh were essential to promote the carbon–carbon
bond formation, however, the third LiC„CPh did not take
part in forming new C–C bond. Considering atomic eco-
nomics, it is important in maximal use of raw materials.
It was reported of oxidative decomposition of organozirco-
nium compounds as a promising method in forming new
carbon–carbon bond through coupling reaction of the
ligands on the zirconocene species [14]. Recently, it was
found out that treatment of zirconacyclopentadienes with
quinones in the presence of CuCl gave cyclobutadiene
derivatives in our group [15]. As a part of our continuing
program on the application of organozirconium and qui-
nones in organic synthesis, herein we would like to report
zirconocene-promoted trimerization of terminal acetylenes
into zirconoenediynes 1 in the presence of p-chloranil
(Scheme 2). Moreover, the resulting zirconoenediynes 1
can be converted into various geminal enediynes through
coupling reaction with electrophiles.
Geminal enediynes (gem-DEEs) have recently received
considerable attention due to their extensive applications
in molecular wires, switches, and other components for
molecular electronics, nonlinear optics (NLO), organic
conductors, light-emitting diodes [1–4]. Consequently,
there is significant interest in the development of new
synthetic methodologies to access geminal enediynes.
Although a number of synthetic methods affording geminal
enediynes have been reported [5–9], alternative strategies
that involve the metal-mediated direct coupling of terminal
acetylenes (Scheme 1) remain to be developed.
Organometal-promoted coupling reactions have proved
to be an extremely powerful tool to construct carbon–car-
bon bonds [10]. Among them, interest in organozirconium
chemistry has been rapidly increasing and a tremendous
number of applications in synthetic chemistry have been
*
Corresponding author. Tel.: +86 10 62782695.
E-mail address: cjxi@tsinghua.edu.cn (C. Xi).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.04.028

C. Xi et al. / Journal of Organometallic Chemistry 692 (2007) 4612–4617
4613
Table 1
R
Optimization of reaction conditionsa
Ph
Ph
Ph
[M]
R
H3+O
Ph
R
Ph
Oxidant
8h
Li[Cp2Zr(C≡CPh)3]
Cp2Zr
X
R
2a
Ph
Scheme 1.
1a
Entry
Oxidant
Temperature (°C)
Yield of 2a (%)b
R
R
1) n-BuLi
2) Cp2ZrCl2
3) p-chloranil
1
2
3
4
5
6
7
1,4-Benzoquinone
TCQ
DDQ
DDQ
DDQ
35
35
35
20
10
20
10
10
67
64
24
21
27
25
R
R
Cp2Zr
X
TCQ
TCQ
X = phenolate, or chloride
a
Reaction conditions: ethynylbenzene (3.0 mmol), Cp2ZrCl2
Scheme 2.
(1.0 mmol), Oxidant (1.3 mmol).
b
Isolated yields.
2. Results and discussion
Ph
Reaction of Li[Cp2Zr(C„CPh)3] prepared by the reac-
tion of Cp2ZrCl2 with 3 equiv. of LiC„CPh according to
reported literature [12], with oxidants such as 1,4-benzo-
quinone, tetrachlorobenzoquinone (TCQ) or dichloro-
dicyanobenzoquinone (DDQ) were carefully examined
and quenched with acid to form (2-(phenylethynyl)but-1-
en-3-yne-1,4-diyl)dibenzene (2a). The product 2a was char-
acterized by 13C NMR spectroscopy. Its 13C NMR(CDCl3,
Me4Si) spectrum revealed characteristic signals for @C-
(„-Ph)2, @CH-Ph at 103.3 and 143.2 ppm, and four sp
carbons appeared at 86.9, 88.3, 89.2, and 94.6 ppm. Its data
were consistent with the literature [7e].
Ph
H
H3+O
D3+O
I2
Ph
2a
Ph
Ph
Ph
Ph
D
Cp2Zr
X
3a
4a
Ph
Ph
Ph
1a
Ph
I
Ph
Scheme 3.
As expected, the oxidants promoted the coupling reac-
tion involving the third LiC„CPh for the trimerization
of phenylacetylene, and their results relied on the different
oxidants and reaction temperature were collected in Table
1. Accordingly to results of entries 1–3, both TCQ and
DDQ worked well for this reaction, and the optimized con-
dition is as the following: using TCQ or DDQ as an oxi-
dant, the reaction was carried out at 35 °C for 8 h under
nitrogen atmosphere. It was noteworthy that in any of
the cases, trace amount of 1,4-diphenyl-1,3-butadiyne was
detected by GC–MS even addition of excess amount of
oxidants.
The intermediate organozirconium 1a was assumed in
forming product 2a. To clarify this issue, deuteriolysis and
iodinolysis of organozirconium 1a afforded monodeuter-
ated compound 3a in 65% yield with 94% deuterium incor-
poration, and monoiodinated product 4a in 60% yield,
respectively (Scheme 3). The results indicated that zirco-
nium containing complex 1a formed as an intermediate.
Under the optimized conditions, the coupling reactions
of various terminal alkynes were extensively examined
and the results are summarized in Table 2. When the aro-
matic 1-alkynes were used, the desired products were
formed in moderated yields (entries 1–4). However, when
the aliphatic 1-alkynes were used, only trace amount of
desired product was formed (entry 5) and main product
was diyne. When 1-ethynylcyclohex-1-ene was used, the
corresponding enediyne 2f was formed in 17% isolated
yield (entry 6). Likely the conjugated system of 1-alkyne
is necessary for the further coupling of third 1-alkyne.
The remaining Zr–C bond of zirconoendiynes 1 could be
used in forming functionalized enediynes through coupling
reaction with various electrophiles such as iodobenzene, or
allyl bromide in the presence of CuCl and/or Pd(PPh3)4.
Typically, 1a was investigated in reacting with allyl bro-
mide in the presence of CuCl, and one new carbon–carbon
bond was formed to give 5a in 53% yield. In addition, the
reaction of 1a with iodobenzene gave compound 6a in 49%
yield in the presence of CuCl and Pd(PPh3)4. Moreover,
when 1a was treated with TCQ in the presence of CuCl,
dimerized product 7a was obtained in 55% yield (Scheme
4).
Recently, triethynylethenes have received attention in
conjugated organic materials, however, such synthetic
reports are rarely reported [16]. The new forming product
4 could be further used in reactions, the reactions of 4 with

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C. Xi et al. / Journal of Organometallic Chemistry 692 (2007) 4612–4617
Table 2
Homo-coupling reaction of alkynes promoted by zirconocene in the presence of TCQ
Entry
1
Alkynes
Time (h)
8
Product
Yield(%)a
67
Ph
Ph
Ph
Ph
H
2a
2
3
12
56
63
Tol-
p
p
p
p
-Tol
p
p
-Tol
H
2b
Tol-
8
-MeOC6H4
C6H4OMe-
C6H4OMe-
p
p
-MeOC6H4
H
2c
4
12
phbi
phbi
43
biph
biph
H
2d
5
6
36
24
Trace
Hex
Hex
Hex
Hex
H
2e
17
H
2f
a
Isolated yields.
Ph
Ph
Ph
Ph
Ph
alkyne 8 under Sonogashira reaction conditions afforded
product 9 in high yields (Scheme 5). Therefore, herein the
reaction provides a general methodology for the prepara-
tion of triethynylethenes.
Br
Ph
Ph
Ph
Ph
PhI
Pd(PPh3)4 (1%)
CuCl (1 eq), rt, 12h
CuCl (1 eq.)
rt, 12h
LCp2Zr
1a
The pathway of the oxidation of Li[Cp2Zr(C„CR)3]
into zirconoenediynes is not clear yet. Possible mechanism
is proposed as the following (Scheme 6). First, the zircon-
ate complex Li[Cp2Zr(C„CR)3] undergoes a 1,2-migra-
tory insertion reaction to give intermediate 10 [12], which
was confirmed by Choukroun et al.[17]. Then the sp2 car-
bon of zirconacyclopropylene reacted with sp carbon of
C„CR to form another intermediate, proposed as the
bicyclic zirconate 11. The intermediate 11 reacts with qui-
none to form 1 via intermediate 12. To understand this
Ph
5a: Yield 53%
6a: Yield 49%
CuCl (1 eq.)
TCQ (1.1 eq)
rt, 12h
Ph
Ph
Ph
Ph
7a: Yield 55%
Ph
Ph
Scheme 4.

C. Xi et al. / Journal of Organometallic Chemistry 692 (2007) 4612–4617
4615
as the solvent and TMS as internal standard. Flash col-
umn chromatography was performed using silica gel
(200–300 mesh).
R
R
R
R
R
I
1% Pd(PPh3)4, CuI
(iPr)2NH, 70oC
+
OH
4.1. A typical procedure for the preparation of (2-
(phenylethynyl)but-1-en-3-yne-1,4-diyl)dibenzene (2a)
8
4
R
OH
9a: R = Ph, Yield 78%
9b: R = Tol, Yield: 69%
The phenylacetylene (3 mmol) was dissolved in THF
(5 mL), and then BuLi (3.2 mmol, 2 mL, 1.6 M solution
in hexane) was added in the solution at ꢀ78 °C. The mix-
ture was stirred at room temperature for 1 h. To the reac-
tion solution, Cp2ZrCl2 (1 mmol, 292 mg) was added at
ꢀ78 °C. This mixture was stirred at room temperature
for 12 h to afford a dark red solution. Then TCQ
(1.3 mmol, 296 mg) was added to the solution and was stir-
red for another 8 h. The reaction mixture was quenched by
3N HCl solution. Product was extract with CH2Cl2 and the
organic extract was dried over MgSO4. Removing the sol-
vent and subsequent purification by column chromatogra-
phy silica gel (CH2Cl2/petroleum ether = 1/10) afforded
204 mg yellow liquid (isolated yield 67%). 1H NMR
(300 MHz, CDCl3, Me4Si) d 7.17 (s, 1H), 7.31–7.40 (m,
5H), 7.52–7.55 (m, 8H), 7.93–7.95 (m, 3H); 13C NMR
(75 MHz, CDCl3, Me4Si) d 86.9, 88.3, 89.2, 94.6, 103.3,
122.4, 122.9, 128.3, 128.4, 128.8, 129.1, 129.2, 131.6,
131.7, 135.7, 143.2. HRMS calcd. for C24H16 304.1252,
found 304.1256.
Scheme 5.
R
R
R
Li
Cp2ZrCl2
Li[Cp2Zr(C≡CR)3]
LiCp2Zr
10
R
O
R
R
migrating
insertion
O
quenone
LiCp2Zr
LiCp2Zr
R
R
R
12
11
R
R
R
R
Cp2Zr
O
4.1.1. 4,40-(2-(p-tolylethynyl)but-1-en-3-yne-1,4-
diyl)bis(methylbenzene) (2b)
1
1
A yellow liquid (194 mg, isolated yield 56 %). H NMR
OLi
(300 MHz, CDCl3, Me4Si) d 2.28 (s, 3H), 2.29 (s, 6H),
7.03–7.13 (m, 7H), 7.33–7.37 (m, 3H), 7.75–7.78 (d,
3JHH = 7.9 Hz, 2H); 13C NMR (75 MHz, CDCl3, Me4Si)
d 21.5, 21.5, 21.6, 86.6, 88.1, 88.8, 94.7, 102.4, 120.0,
120.0, 129.0, 129.1, 129.1, 129.2, 131.5, 131.5, 133.2,
138.4, 138.8, 139.3, 142.6. HRMS calcd. for C27H22
346.1722, found 346.1719.
Scheme 6.
mechanism, the separation and characterizations of their
intermediates are still being in progress.
3. Conclusions
In summary, zirconocene-promoted self-coupling reac-
tions of terminal alkynes were successively developed in
the presence of p-chloranil to afford geminal enediynes.
Its intermediates including one Zr–C bond were used to
form functionalized enediynes. These reactions provided
the convenient methodologies in synthesizing new organic
materials with conjugated systems in good yields.
4.1.2. 4,40-(2-((4-Methoxyphenyl)ethynyl)but-1-en-3-yne-
1,4-diyl)bis(methoxybenzene) (2c)
1
A yellow liquid (248 mg, isolated yield 63 %). H NMR
(300 MHz, CDCl3, Me4Si) d 3.81 (s, 3H), 3.82 (s, 3H), 3.83
(s, 3H), 6.84–7.05 (m, 7H), 7.44–7.50 (m, 4H), 7.89–7.92
(m, 2H); 13C NMR (75 MHz, CDCl3, Me4Si) d 55.44,
86.3, 87.7, 88.5, 94.4, 101.2, 113.9, 114.1, 114.2, 115.3,
115.4, 129.1, 130.7, 133.2, 141.8, 159.7, 160.0, 160.2.
HRMS calcd. for C27H22O3 394.1569, found 394.1573.
4. Experimental
All reactions were carried out in pre-dried Schlenk tube
and under nitrogen with a slightly positive pressure.
Unless otherwise noted, all starting materials were
commercially available and were used without further
purification. Tetrahydrofuran (THF) was refluxed and
distilled from sodium and benzophenone under a nitrogen
atmosphere. 1H NMR and 13C NMR spectra were
recorded on JOEL 300 NMR spectrometer with CDCl3
4.1.3. 4,40-(2-(Diphenyl-4-ylethynyl)but-1-en-3-yne-1,4-diyl)-
bis(diphenyl) (2d)
1
A yellow liquid (229 mg, isolated yield 43 %). H NMR
(300 MHz, CDCl3, Me4Si) d 7.21 (s, 1H), 7.30–7.36 (m,
3H), 7.40–7.44 (m, 6H), 7.55–7.64 (m, 16H), 8.02–8.06 (d,
2H); 13C NMR (75 MHz, CDCl3, Me4Si) d 88.0, 88.7,
90.3, 95.1, 103.4, 121.9, 122.0, 127.1, 127.3, 127.8, 127.9,
129.0, 129.7, 132.2, 132.3, 135.0, 140.3, 140.4, 140.4,

4616
C. Xi et al. / Journal of Organometallic Chemistry 692 (2007) 4612–4617
141.2, 141.6, 141.8, 142.9. HRMS calcd. for C42H28
532.219, found 532.221.
4.1.8. (2-(Phenylethynyl)but-1-en-3-yne-1,1,4-triyl)-
tribenzene (6a)
The reaction was carried out in a similar way to that
described above using iodobenzene instead of I2. After
adding the iodobenzene and catalytic amount of
Pd(PPh3)4, the reaction mixture was stirred for 12 h at
50 °C. 1H NMR (300 MHz, CDCl3, Me4Si) d 7.25–8.20
(m, 20H); 13C NMR (75 MHz, CDCl3, Me4Si) d 88.9,
91.9, 102.1, 123.3, 127.8, 128.1, 128.3, 128.4, 128.6, 128.9,
129.1, 130.6, 131.6, 131.8, 140.5, 156.0. Calcd. for C30H20
380.1565, found 380.1569.
4.1.4. 1,10-(2-(Cyclohexenylethynyl)but-1-en-3-yne-1,4-diyl)-
dicyclohex-1-ene (2f)
1
A yellow liquid (54 mg, isolated yield 17 %). H NMR
(300 MHz, CDCl3, Me4Si) d 1.56–1.66 (m, 12H), 2.10–
2.16 (m, 12H), 6.01 (s, 1H), 6.09–6.12 (m, 2H), 6.44 (s,
1H); 13C NMR (75 MHz, CDCl3, Me4Si) d 21.6, 21.9,
22.2, 22.4, 22.7, 25.8, 26.6, 27.0, 28.7, 29.2, 85.4, 87.8,
88.4, 95.1, 100.2, 120.8, 121.1, 134.7, 134.9, 136.9, 145.8.
HRMS calcd. for C24H28 316.2191, found 316.2197.
4.1.9. (5-Phenyl-3,6-bis(phenylethynyl)octa-3,5-dien-1,7-
diyne-1,4,8-triyl)tribenzene (7a)
4.1.5. (2-(Phenylethynyl)but-1-deuterium-1-en-3-yne-1,4-
diyl)dibenzene (3a)
To the reaction mixture of 1a at room temperature,
CuCl and p-chloranil were added and the reaction mixture
was stirred at room temperature for 12 h. The resulting
mixture was treated with 3N HCl at 0 °C. Product was
extract with CH2Cl2 and the organic extract was dried over
MgSO4. Removing the solvent and subsequent purification
by column chromatography silica gel (CH2Cl2/petroleum
ether = 1/10) yield 168 mg of the title compound in 55%
isolated yield.
The reaction was carried out in a similar way to that
described above using DCl instead of 3N HCl to quench
the reaction mixture. Isolated yield: 65%. 1H NMR
(300 MHz, CDCl3, Me4Si) d 7.38–7.48 (m, aromatic, 9H),
7.59–7.61 (m, aromatic, 4H), 8.00–8.03 (m, aromatic, 4H);
13C NMR (75 MHz, CDCl3, Me4Si) d 87.0, 88.5, 89.3,
94.7, 103.3, 122.9, 123.0, 128.4, 128.5, 128.9, 129.2, 129.3,
1
131.8, 131.8, 135.8, 142.9 (t, JDC = 23.7 Hz). Calcd. for
C24H15D 305.1315, found 305.1319.
1H NMR (300 MHz, CDCl3, Me4Si) d 7.34–7.38 (m,
aromatic, 6H), 7.43–7.54 (m, aromatic, 16H), 7.66–7.71
(m, aromatic, 4H), 7.99–8.02 (m, aromatic, 4H); 13C
NMR (75 MHz, CDCl3, Me4Si) d 86.1, 86.5, 92.9, 95.7,
104.1, 122.6, 122.7, 127.9, 128.4, 128.5, 128.8, 129.0,
129.2, 130.0, 131.5, 131.9, 136.7, 146.0. Calcd. for C48H30
606.2348, found 606.2353.
4.1.6. (1-Iodo-2-(phenylethynyl)but-1-en-3-yne-1,4-diyl)-
dibenzene (4a)
After addition of CuCl (1.0 mmol, 99 mg) to the reac-
tion mixture of 1a at room temperature, I2 (1.2 mmol,
305 mg) was added and the reaction mixture was stirred
at room temperature for 3 h. The resulting mixture was
treated with 3N HCl at 0 °C. Product was extract with
CH2Cl2 and the organic extract was dried over MgSO4.
Removing the solvent and subsequent purification by col-
umn chromatography silica gel (CH2Cl2/petroleum
ether = 1/10) yield 258 mg of the title compound in 60%
isolated yield. 1H NMR (300 MHz, CDCl3, Me4Si) d
7.28–7.29 (m, 10H), 7.34–7.41 (m, 2H), 7.63–7.71 (m,
3H); 13C NMR (75 MHz, CDCl3, Me4Si) d 86.0, 92.1,
92.5, 93.9, 114.1, 118.0, 122.6, 122.7, 127.8, 128.4, 128.5,
128.8, 129.0, 129.3, 130.0, 131.5, 131.9, 142.0. Calcd. for
C24H15I 430.0218, found 430.0221.
4.2. A typical procedure for the preparation of 2-methyl-5,8-
diphenyl-6-(phenylethynyl)octa-5-en-3,7-diyn-2-ol (9a)
A mixture of 4a (1 mmol, 430 mg), Pd(PPh3)4 (30 mg),
CuI (2 mg), 2-methylbut-3-yn-2-ol (2 mmol, 194 lL), and
NEt3 (5 mL) was stirred for 12 h at 50 °C. The mixture
was filtrated under reduced pressure, affording a clarifying
solution, which was washed with 2N HCl solution to
remove NEt3. The product was extracted with CH2Cl2
and the organic extract was dried over MgSO4. Removing
the solvent and subsequent purification by column chroma-
tography silica gel (diethyl ether/petroleum ether = 1/1)
1
4.1.7. (3-(Phenylethynyl)hepta-3,6-dien-1-yne-1,4-diyl)-
dibenzene (5a)
afforded 302 mg product (isolated yield 78%). H NMR
(300 MHz, CDCl3, Me4Si) d 1.69 (s, 6H), 2.87 (br, 1H),
7.34–8.02 (m, 15H); 13C NMR (75 MHz, CDCl3, Me4Si)
d 31.4, 66.0, 82.7, 87.4, 88.7, 94.4, 96.4, 105.7, 109.4,
122.7, 123.0, 128.0, 128.4, 128.5, 128.8, 128.9, 129.0,
129.1, 131.6, 131.8, 135.4, 136.7. Calcd. for C29H22O
386.1671, found 386.1673.
The reaction was carried out in a similar way to that
described above using allyl bromide instead of I2. After
adding the allyl bromide, the reaction mixture was stirred
for 12 h at room temperature. 1H NMR (300 MHz, CDCl3,
Me4Si) d 3.66–3.69 (d,3JHH = 6.5 Hz, 2H), 5.03–5.07 (d,
3JHH = 10.0 Hz, 1H), 5.13–5.19 (d, JHH = 17.1 Hz, 1H),
3
3
3
3
5.81–5.90 (m, JHH = 6.5 Hz, JHH = 10.3 Hz, JHH
=
4.2.1. 2-Methyl-5,8-dip-tolyl-6-(p-tolylethynyl)octa-5-en-
3,7-diyn-2-ol (9b)
16.8 Hz, 1H), 7.21–7.62 (m, 15H); 13C NMR (75 MHz,
CDCl3, Me4Si) d 40.7, 87.1, 87.7, 90.8, 93.4, 103.2, 116.9,
123.2, 123.3, 127.9, 128.3, 128.4, 128.5, 128.6, 128.6,
131.5, 131.7, 134.5, 139.8, 155.2. Calcd. for C27H20
344.1565, found 344.1567.
1
A yellow liquid (295 mg, isolated yield 69%). H NMR
(300 MHz, CDCl3, Me4Si) d 1.61(s, 6H), 2.32 (s, 3H),
3
2.33(s, 3H), 2.36 (s, 3H), 7.08–7.11 (d, JHH = 8.2 Hz,
3
2H), 7.12–7.15 (d, JHH = 8.2 Hz, 2H), 7.17–7.20 (t,

C. Xi et al. / Journal of Organometallic Chemistry 692 (2007) 4612–4617
4617
3
3JHH = 8.2 Hz, 2H), 7.29–7.32 (d, JHH = 7.9 Hz, 2H),
(d) B.R. Kaafarani, A.A. Pinkerton, D.C. Neckers, Tetrahedron
Lett. 42 (2001) 8137;
(e) G.W. Kabalka, G. Dong, B. Venkataiah, Tetrahedron Lett. 46
(2005) 763;
(f) G. T Hwang, H.S. Son, J.K. Ku, B.H. Kim, J. Am. Chem. Soc.
125 (2003) 11241.
3
7.45–7.47 (d, JHH = 7.9 Hz, 2H), 7.84–7.87 (d,
3JHH = 7.9 Hz, 2H); 13C NMR (75 MHz, CDCl3, Me4Si)
d 21.5, 21.6, 31.5, 66.0, 83.0, 87.2, 88.5, 94.4, 96.6, 105.1,
108.9, 119.9, 120.1, 128.7, 128.9, 129.2, 129.3, 131.5,
131.7, 134.0, 134.4, 138.9, 139.1, 139.1. Calcd. for
C32H28O 428.2140, found 428.2140.
[8] (a) Y. Zhao, R.R. Tykwinski, J. Am. Chem. Soc. 121 (1999) 458;
(b) Y. Zhao, A.D. Slepkov, C.O. Akoto, R. McDonald, F.A.
Hegmann, R.R. Tykwinski, Chem. Eur. J. 11 (2005) 321.
[9] (a) C.K. Tseng, K.G. Migliorese, S.I. Miller, Tetrahedron 30 (1974)
377;
Acknowledgements
(b) R. Livingston, L. Cox, S. Odermatt, F. Diederich, Helv. Chim.
Acta 85 (2002) 3052.
[10] F. Diederich, P.J. Stang (Eds.), Metal-Catalyzed Cross-coupling
Reactions, Wiley-VCH, Weinheim, 1997.
[11] (a) For recent reviews, see: H.G. Alt, A. Ko¨ppl, Chem. Rev. 100
(2000) 1205;
This work was supported by the National Natural Sci-
ence Foundation of China (20572058) and Beijing Depart-
ment of Education (XK100030514).
References
(b) G. Erker, Acc. Chem. Res. 34 (2001) 309;
(c) E.-I. Negishi, Pure Appl. Chem. 73 (2001) 239;
(d) P. Wipf, C. Kendall, Chem.-Eur. J. 8 (2002) 1778;
(e) K. Suzuki, P. Wifp, Tetrahedron 60 (2004) 1267.
[12] K. Takagi, C.J. Roussert, E.-I. Negishi, J. Am. Chem. Soc. 113
(1991) 1440.
[13] (a) Y.R. Dumond, E. Negishi, J. Am. Chem. Soc. 121 (1999) 11223;
(b) Y.R. Dumond, E. Negishi, Tetrahedron 60 (2004) 1345.
[14] (a) M.J. Burk, D.L. Staley, W. Tumas, J. Chem. Soc., Chem.
Commun. (1990) 809;
[1] (a) M.B. Nielsen, F. Diederich, Chem. Rev. 105 (2005) 1837;
˚
(b) W.R. Salaneck, I. Lundstro¨m, B. Ranby, Conjugated Polymers
and Related Materials, Oxford University Press, Oxford, 1993;
(c) T.A. Skotheim, R.L. Elsenbaumer, J.R. Reynold, Handbook of
Conducting Polymers, second ed., Marcel Dekker, New York, 1998;
(d) A. Kraft, A.C. Grimsdale, A.B. Holmes, Angew. Chem. Int. Ed.
37 (1998) 402;
(e) A. Pron, P. Rannou, Prog. Polym. Sci. 27 (2002) 135.
[2] (a) M.C. Petty, M.R. Bryce, D. Bloor (Eds.), Introduction to
Molecular Electronics, Edward Arnold, London, 1995;
(b) L.A. Bumm, J.J. Arnold, M.T. Cygan, T.D. Dunbar, T.P. Burgin,
L. II Jones, D.L. Allara, J.M. Tour, P.S. Weiss, Science 271 (1996)
1705.
(b) R.F. Jordan, J. Chem. Educ. 65 (1988) 285;
(c) R.F. Jordan, R.E. LaPointe, C.S. Bajgur, S.F. Echols, R. Willett,
J. Am. Chem. Soc. 109 (1987) 4111;
(d) R.F. Jordan, C.S. Bajgur, R. Willett, B. Scott, J. Am. Chem. Soc.
108 (1986) 7410;
(e) D.A. Straus, C. Zhang, T.D. Tilley, J. Organomet. Chem. 369
(1989) C13;
[3] L. Gobbi, P. Seiler, F. Diederich, Angew. Chem. Int. Ed. Engl. 38
(1999) 674.
(f) M.J. Burk, W. Tumas, M.D. Ward, D.R. Wheelert, J. Am. Chem.
Soc. 112 (1990) 6133;
[4] (a) R.E. Martin, U. Gubler, C. Boudon, V. Gramlich, C. Bosshard,
J.-P. Gisselbrecht, P. Gunter, M. Gross, F. Diederich, Chem. Eur. J.
¨
(g) Y. Liu, W.-H. Sun, K. Nakajima, T. Takahashi, Chem. Commun.
(1998) 1133;
3 (1997) 1505;
(b) R. Spreiter, C. Bosshard, G. Kno¨pfle, P. Gunter, R.R. Tykwinski,
¨
(h) K. Kasai, Y. Liu, R. Hara, T. Takahashi, Chem. Commun.
(1998) 1989.
M. Schreiber, F. Diederich, J. Phys. Chem. B 102 (1998) 29;
(c) R.R. Tykwinski, U. Gubler, R.E. Martin, F. Diederich, C.
[15] (a) C. Chen, C. Xi, C. Lai, R. Wang, X. Hong, Eur. J. Org. Chem.
(2004) 647;
(b) C. Chen, C. Xi, Y. Liu, X. Hong, J. Org. Chem. 71 (2006) 5373.
[16] (a) R. Rossi, A. Carpita, C. Bigelli, Tetrahedron Lett. 26 (1985) 523;
(b) T. Rankin, R.R. Tykwinski, Org. Lett. 5 (2003) 213;
(c) A.S. Andersson, K. Qvortrup, E.R. Torbensen, J.-P. Mayer, J.-P.
Bosshard, P. Gunter, J. Phys. Chem. B 102 (1998) 4451.
¨
[5] (a) T. Bo¨hm-Go¨ssl, W. Hunsmann, L. Rohr-Schneider, W.M.
Schneider, W. Ziegenbein, Chem. Ber. 96 (1963) 4;
(b) A.H. Alberts, J. Am. Chem. Soc. 111 (1989) 3093.
[6] R. Gleiter, R. Merger, B. Nuber, J. Am. Chem. Soc. 114 (1992) 8921.
[7] (a) J.-F. Nierengarten, A. Hermann, R.R. Tykwinski, M. Ruttimann,
¨
˚
Gisselbrecht, C. Boudon, M. Gross, A. Kadziola, K. Kilsa, M.B.
Nielsen, Eur. J. Org. Chem. (2005) 3600;
F. Diederich, C. Boudon, J.-P. Gisselbrecht, M. Gross, Helv. Chim.
Acta 80 (1997) 293;
(d) C. Chen, Z. Ai, J. Lin, X. Hong, C. Xi, Synlett (2006) 2454.
[17] R. Choukroum, J. Zhao, C. Lorber, P. Cassoux, B. Donnadieu,
Chem. Commun. (2000) 1511.
(b) D.A. Shultz, K.P. Gwaltney, H. Lee, J. Org. Chem. 63 (1998)
4034;
(c) B.R. Kaafarani, D.C. Neckers, Tetrahedron Lett. 42 (2001) 4099;