Facile synthesis of functionalized bis(arylethynyl)benzene derivatives via sila-Sonogashira reaction

Article abstract of DOI:10.1080/00397911.2010.542538

This article describes a facile synthesis of a new series of symmetrical bis(arylethynyl) benzene derivatives via a one-pot coupling reaction between trialkylsilyl protected arylalkynyes and aryldihalides bearing both electron-withdrawing (EW) and electrondonating groups (ED) in the presence of PdCl₂(PPh₃)₂(5%) / CuI/tetrabutylammonium fluoride / triethylamine / tetrahydrofuran (sila-Sonogashira reaction) at room temperature. Copyright Taylor & Francis Group, LLC.

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Facile Synthesis of Functionalized
Bis(arylethynyl)benzene Derivatives via
Sila–Sonogashira Reaction
Zhang-Lin Zhou a , Lihua Zhao a , Sean Zhang a , Kent Vincent a , Sity
Lam a & Dick Henze a
a Hewlett-Packard Laboratories, Palo Alto, California, USA
Accepted author version posted online: 17 Nov 2011.Published
online: 03 Feb 2012.
To cite this article: Zhang-Lin Zhou , Lihua Zhao , Sean Zhang , Kent Vincent , Sity Lam & Dick Henze
(2012) Facile Synthesis of Functionalized Bis(arylethynyl)benzene Derivatives via Sila–Sonogashira
Reaction, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 42:11, 1622-1631, DOI: 10.1080/00397911.2010.542538
To link to this article: http://dx.doi.org/10.1080/00397911.2010.542538
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Synthetic Communications1, 42: 1622–1631, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.542538
FACILE SYNTHESIS OF FUNCTIONALIZED
BIS(ARYLETHYNYL)BENZENE DERIVATIVES VIA
SILA–SONOGASHIRA REACTION
Zhang-Lin Zhou, Lihua Zhao, Sean Zhang, Kent Vincent,
Sity Lam, and Dick Henze
Hewlett-Packard Laboratories, Palo Alto, California, USA
GRAPHICAL ABSTRACT
Abstract This article describes a facile synthesis of a new series of symmetrical bis(aryl-
ethynyl)benzene derivatives via a one-pot coupling reaction between trialkylsilyl protected
arylalkynyes and aryldihalides bearing both electron-withdrawing (EW) and electron-
donating groups (ED) in the presence of PdCl2(PPh3)2(5%) / CuI/tetrabutylammonium
fluoride / triethylamine / tetrahydrofuran (sila–Sonogashira reaction) at room temperature.
Keywords Bis(arylethynyl)benzene
Sonogashira reaction
derivatives; cross-coupling
reaction; Sila–
INTRODUCTION
Functionalized conjugated bis(arylethynyl)benzene derivatives have received
increased attention because of their potential in optical and electrical applications.
During the course of searching for new targets for molecular electronics and molecu-
lar display applications, there was a need to synthesize functionalized conjugated
bis(arylethynyl)benzene derivatives bearing either electron-withdrawing (EW) and=
or electron-donating (ED) groups in large quantities. Among a large number of syn-
thetic methods developed for these types of materials, the Sonogashira
palladium-catalyzed cross-coupling reaction[1] has been proved to be a powerful
method for the formation of shape-persistent arylethynylenes.[2] This method has
been employed in the generation of scaffolds leading to molecular electronic
devices,[3] dendrimers,[4] dehydrobenzannulenes,[5] foldamers,[6] and polymers.[7]
The Sonogashira cross-coupling reaction has been a reliable, high-yielding reaction
Received November 5, 2010.
Address correspondence to Zhang-Lin Zhou, Hewlett-Packard Laboratories, Hewlett-Packard
Company, 1501 Page Mill Road, MS 1157, Palo Alto, CA 94304, USA. E-mail: zhang-lin.zhou@hp.com
1622

BIS(ARYLETHYNYL)BENZENE DERIVATIVES
1623
that is tolerant of a wide variety of functional groups. However, the use of the
traditional Sonogashira reaction to effect iterative synthesis often requires stepwise
deprotection of terminal acetylenes and coupling reactions, which normally result
in much lower yields.[8] Thus, it is necessary to develop a more efficient method to
synthesize such functionalized bis(arylethynyl)benzene derivatives in better yields
for potential molecular electronics and display applications.
There have been several published reports recently to achieve Sonogashirsa
cross-coupling reactions in one step via the Sila–Sonogashira reaction.[9] However,
most of these published papers used special reagents,[9a] special catalysts,[9e,f] tra-
ditional heating,[9b,c] and=or microwave heating.[9d] Moreover, most of them also
needed either aryl iodides or activated aryl bromides as substrates. We report herein
a very efficient catalyst system for the Sila–Sonogashira coupling reaction, consisting
of PdCl2(PPh3)2(5%)=CuI=tetrabutylammonium fluoride (TBAF)=triethylamine
(TEA)=tetrahydrofuran (THF) to generate symmetrical bisarylethynyes derivatives
bearing both EW and ED groups at room temperature in good yields.
Initially, we tried to follow the traditional Sonogashira approach to make the
functionalized bisarylethynyes derivatives.[10] Thus, we carried out the deprotection
reaction of the trimethylsilyl (TMS) group of 3-(trimethylsilylethynyl)formanilide
(1b) by 1 equiv. of TBAF under argon (Ar) at room temperature (r.t.) within
10 min, affording acetylene 2 in 90% yield. Subsequent coupling reaction of acetylene
2 with 2,5-dibrormonitrobenzene (3a) by 5% equivalent of PdCl2(PPh3)2=CuI as
catalysts at room temperature under Ar resulted in a mixture of 6% of the desired
bis-coupling product (4b), 42% of monocoupling product (5), and 28% of
homocoupling by-product (6) (Scheme 1).
To minimize the undesired homocoupling reaction, we used a one-pot process
by combining both deprotection and coupling steps in one step under Ar. When a
solution of TMS protected compound 1, dibromide 3a, PdCl2(PPh3)2=CuI, and
Scheme 1. Deprotection of 3-(trimethylsilylethynyl)formanilide (1b) and subsequent coupling reaction
with 2,5-dibromonitrobenzene (3a).

1624
Z.-L. ZHOU ET AL.
Scheme 2. One-pot coupling reaction of 3-(trimethylsilylethynyl)formanilide (1b) and with 2,5-dibromo-
nitrobenzene (3a).
TEA in THF is treated with TBAF at room temperature, a blue color appeared. The
reaction was completed within 2 h at room temperature. Around 80% of mixed pro-
ducts of the desired bis-coupling product (4b) and the homocoupling by-product (6)
were obtained in the ratio of 83=17. No monocoupled side product 5 was detected.
Around 62% of the pure desired bis-coupled product (4b) can be isolated after flash
chromatography (Scheme 2).
Based on these results, we found that PdCl2(PPh3)2 (5%)=CuI=TBAF=TEA=
THF is a very efficient system to promote a one-pot Sonogashira coupling reaction
to generate functionalized bis(arylethynyl)benzene derivatives. We successfully used
this method to synthesize a series of such bis(arylethynyl)benzene derivatives with
both EW and=or ED groups (Scheme 3), which provided us various potential targets
for evaluation of molecular electronics and display applications.
Table 1 describes 12 examples of this one-pot Sonogashira coupling method to
synthesize functionalized conjugated bisarylethynylbenzene derivatives in good iso-
lated yields (58–85%) at room temperature. This is extremely high overall yield con-
sidering that this is a single combination of three-step reactions. Simple trimethylsilyl
protected phenylethynylacetylene (1a) coupled with 2,5-dibromonitrobenzene in this
condition afforded the desired bis-coupled product (4a) in 58% yield, without the
complication of homocoupling product. Both protected 3- and 4-formamidophenyl-
acetylenes reacted with 2,5-dibromonitrobenzene nicely, giving the corresponding
1
bis-coupled products 4b and 4c respectively. Based on the H NMR spectra of 4b
and 4c, these two products are the mixtures of two tautomers of formamide and
enol. Sterically hindered trimethylsilyl protected 3,5-tert-butylphenylacetylene (1d)
can react with various aryldihalides either with EW and=or ED groups (3a, 3b, 3c,
and 3d) to give rise to the corresponding desired bis-coupled products in very good
Scheme 3. General examples of one-pot coupling reaction of aryldihalides with TMS-protected
arylethynes.

BIS(ARYLETHYNYL)BENZENE DERIVATIVES
Table 1. Examples of one-pot coupling reaction of aryldihalides with TMS-protected arylethynes
Entry Arylethynes Aryldihalides Product (isolated yield)
1625
1
2
3
4
5
(Continued )

1626
Z.-L. ZHOU ET AL.
Table 1. Continued
Entry
Arylethynes
Aryldihalides
Product (isolated yield)
6
7
8
9
10
11
(Continued )

BIS(ARYLETHYNYL)BENZENE DERIVATIVES
1627
Table 1. Continued
Entry
Arylethynes
Aryldihalides
Product (isolated yield)
12
yields without any detected side products such as homocoupling product or
monocoupling product. These are very significant results, because traditional Sono-
gashira coupling reactions very often gave only monocoupled product, especially
when dihalides were inactivated by electron-donating groups such as 3b and 3d.
As for the substrates that are precursors to aldehyde and amine 1e and 1f, both
coupling reactions with 2,5-dibromonitrobenzene (3a) went smoothly to give the
desired products 4h and 4i in 70% and 65% yields respectively, which can be further
liberated to give reactive conjugated bisarylethynylbenzene derivatives. The last
three examples demonstrated heterocyclic ring systems such as trimethylsilyl pro-
tected 3- or 4-pyridylacetylenes (1g and 1h) can also couple with dihalides in the
same condition, giving rise to the corresponding bis-coupled products (4j-4l) in good
yields.
In summary, we have developed
a very efficient catalyst system,
PdCl2(PPh3)2(5%)=CuI=TBAF=TEA=THF, for a one-pot Sila–Sonogashira reaction
between trimethylsilyl protected arylacetylenes with aryldihalide bearing both EW
and=or ED groups at room temperature. This method greatly improves the synthesis
of these highly functionalized symmetrical bis(arylethynyl)benzene derivatives and
provides easy access to these novel targets in large quantities for evaluation of mol-
ecular electronics and potential display applications.
EXPERIMENTAL
Typical Procedure for Synthesis of Symmetrical
Bis(arylethynyl)benzene Derivatives: Synthesis of 1,4-Bis[3’,5’-di-
tert-butylphenylethynyl]-5-methly-2-methoxy Carbonylbenzene (4g)
Tetrabutylammonium fluoride (2.5 mL) was added to a solution of 1-[30,50-di-tert-
butylphenyl-2-trimethylsilylacetylene (1d) (572 mg, 2.0mmol), methyl 2,5-dibromo-
4-methylbenzoate (3d) (308 mg, 1.0 mmol), PdCl2(PPh3)2 (100 mg, 0.1 mmol), and
CuI (20 mg, 0.1 mmol) in 10 mL of triethylamine and 10 mL of tetrahydrofuran.
The resulting solution was stirred at room temperature overnight. Then, the mixture
was partitioned between ethyl acetate and water (50 ml=50 ml). The aqueous layer
was extracted with ethyl acetate (50 mL). The combined organic layer was washed
with water and brine and dried over sodium sulfate. Filtration of sodium sulfate
and evaporation of the solvent followed by purification by flash chromatography
gave the desired compound 4g as a pale yellow solid: 390 mg (68%). 1H NMR

1628
Z.-L. ZHOU ET AL.
(CDCl3, 300 MHz) d 8.15 (s, 1 H), 7.55 (s, 1 H), 7.38ꢀ7.42 (m, 6 H), 3.97 (s, 3 H),
2.56 (s, 3 H), 1.34 (s, 36 H); 13C NMR (75 MHz, CDCl3) d 166.5, 151.2, 151.1, 144.1,
135.2, 134.4, 129.4, 126.2, 126.1, 123.4, 122.4, 122.2, 96.9, 87.4, 86.2, 52.4, 35.1, 31.6,
20.9; IR (neat) n (cmꢀ1) 2970, 2871, 2210, 1742, 1590, 1252, 877. Anal. calcd. for
C41H50O2: C, 85.67; H, 8.77. Found: C, 85.51; H, 8.72.
1,4-Bis[phenylethynyl]-2-nitrobenzene (4a)
Yield: 58%; 1H NMR (CDCl3, 300 MHz) d 8.21 (m, 1 H), 7.68 (m, 2 H), 7.57 (m,
5 H), 7.39 (m, 5 H); 13C NMR (75 MHz, CDCl3) d 149.5, 135.2, 134.5, 132.5, 132.1,
132.0, 131.8, 129.4, 129.2, 128.8, 128.7, 128.5, 128.4, 127.6, 124.1, 122.2, 122.1,
118.0, 98.9, 93.6, 86.9, 84.9; IR (neat) n (cmꢀ1) 2930, 2220, 1540, 1351, 756. Anal.
calcd. for C22H13NO2: C, 81.72; H, 4.05; N, 4.33. Found: C, 81.56; H, 4.03; N, 4.29.
1,4-Bis[3’-formamidophenylethynyl]-2-nitrobenzene (4b)
1
Yield: 62%; H NMR (DMSO-d6, 300 MHz) d 10.38–10.25 (m, 2 H), 8.85 (m,
0.5 H), 8.31 (m, 2 H), 7.94–7.89 (m, 3.5 H), 7.50 (m, 2 H), 7.45–7.31 (m, 5 H); 13C
NMR (75 MHz, CDCl3) d 163.1, 160.4, 149.9, 149.8, 139.4, 139.1, 139.0, 135.3,
130.6, 130.5, 130.1, 130.0, 127.8, 127.4, 127.3, 123.8, 122.7, 122.2, 121.0, 120.7,
120.4, 120.3, 117.1, 98.2, 93.5, 87.4, 84.9; IR (neat) n (cmꢀ1) 3272, 3090, 2890,
1691, 1540, 1400, 792. Anal. calcd. for C24H15N3O4 ꢁ 0.25H2O: C, 69.64; H, 3.77;
N, 10.15. Found: C, 69.61; H, 3.59; N, 10.04.
1,4-Bis[4’-formamidophenylethynyl]-2-nitrobenzene (4c)
1
Yield: 55%; H NMR (DMSO-d6, 300 MHz) d 10.47–10.39 (m, 2 H), 8.88 (m,
0.5 H), 8.31–8.24 (m, 2.5 H), 7.83 (m, 2 H), 7.66 (m, 3 H), 7.55 (m, 4 H), 7.28 (s, 1
H); 13C NMR (75 MHz, CDCl3) d 163.0, 160.4, 149.6, 140.0, 139.7, 136.0, 135.1,
133.6, 133.5, 133.2, 133.1, 127.6, 123.7, 119.7, 119.6, 117.6, 117.2, 116.4, 116.3, 98.8,
93.9, 87.0, 84.7; IR (neat) n (cmꢀ1) 3260, 3010, 2220, 1705, 1610, 1532, 1301, 838. Anal.
calcd. for C24H15N3O4 ꢁ 0.25H2O: C, 69.64; H, 3.77; N, 10.15. Found: C, 69.42; H,
3.64; N, 10.02.
1,4-Bis[3’,5’-di-tert-butylphenylethynyl]-2-nitrobenzene (4d)
1
Yield: 75%; H NMR (CDCl3, 300 MHz) d 7.43–7.26 (m, 5 H), 5.45 (s, 2 H),
2.46 (s, 3 H); 13C NMR (75 MHz, CDCl3) d 151.1, 149.3, 135.2, 134.5, 127.6,
126.3, 126.1, 124.1, 124.0, 123.7, 121.3, 121.1, 118.1, 100.2, 94.7, 85.8, 83.8, 34.9;
IR (neat) n (cmꢀ1) 2970, 2871, 2220, 1592, 1540, 1360, 877. Anal. calcd. for
C38H45NO2: C, 83.32; H, 8.28; N, 2.56. Found: C, 83.20; H, 8.21; N, 2.53.
1,4-Bis[3’,5’-di-tert-butylphenylethynyl]-5-methyl-2-nitrobenzene
(4e)
Yield: 72%; 1H NMR (CDCl3, 300 MHz) d 8.25 (s, 1 H), 7.60 (s, 1 H), 7.40–7.48
(m, 6 H), 2.60 (s, 3 H), 1.35 (s, 36 H); 13C NMR (75 MHz, CDCl3) d 151.1, 151.0, 145.4,

BIS(ARYLETHYNYL)BENZENE DERIVATIVES
1629
135.2, 128.0, 126.3, 125.9, 124.0, 123.8, 123.7, 121.5, 121.4, 118.1, 99.5, 98.2, 84.9, 84.1,
34.9, 31.3; IR (neat) n (cmꢀ1) 2960, 2872, 2215, 1590, 1360, 1340, 877. Anal. calcd. for
C39H47NO2: C, 83.38; H, 8.43; N, 2.49. Found: C, 83.30; H, 8.50; N, 2.48.
1,4-Bis[3’,5’-di-tert-butylphenylethynyl]-2-trifluoromethylbenzene
(4f)
Yield: 68%; 1H NMR (CDCl3, 300 MHz) d 7.86 (s, 1 H), 7.66 (s, 2 H), 7.44 (m,
2 H), 7.40 (m, 4 H), 1.35 (s, 36 H); 13C NMR (75 MHz, CDCl3) d 151.0, 134.0, 133.7,
129.1, 129.0, 126.0, 123.5, 123.4, 123.3, 121.6, 121.5, 97.9, 93.7, 86.7, 84.2, 34.8, 31.3;
19F NMR (282 MHz, CDCl3) d ꢀ62.6; IR (neat) n (cmꢀ1) 2970, 2871, 2220, 1590,
1170, 1142, 876. Anal. calcd. for C39H45F3: C, 82.07; H, 7.95; F, 9.99. Found: C,
81.91; H, 7.92; F, 9.78.
1,4-Bis[4’-(1’’,3’’-dioxolan-2’’-yl)phenylethynyl]-2-nitrobenzene (4h)
Yield: 70%; 1H NMR (CDCl3, 300 MHz) d 8.23 (s, 1 H), 7.70 (m, 2 H), 7.61 (m,
4 H), 7.49 (m, 4 H), 5.84 (s, 2 H), 4.15–4.05 (m, 8 H); 13C NMR (75 MHz, CDCl3) d
149.5, 139.2, 139.0, 135.3, 134.5, 132.1, 131.8, 127.7, 126.7, 126.6, 124.1, 123.0, 122.9,
118.0, 103.1, 98.6, 93.3, 87.3, 85.3, 65.4; IR (neat) n (cmꢀ1) 2971, 2890, 2220, 1542,
1350, 1083, 832. Anal. calcd. for C28H21NO6: C, 71.94; H, 4.53; N, 3.00. Found: C,
71.95; H, 4.43; N, 3.01.
1,4-Bis[4’(trifluoromethylacetamidoethyl)phenylethynyl]-2-
nitrobenzene (4i)
1
Yield: 65%; H NMR (DMSO-d6, 300 MHz) d 10.03 (t, J ¼ 1.8 Hz, 2 H), 8.27
(s, 1H), 7.87 (m, 2H), 7.58 (m, 4 H), 7.35 (m, 4 H), 4.43 (d, J ¼ 8.7 Hz, 4 H); 13C
NMR (75 MHz, DMSO-d6) d 157.2, 156.7, 149.7, 139.8, 139.5, 136.1, 135.2, 133.0,
132.3, 128.3, 128.2, 123.8, 120.8, 120.7, 118.3, 117.2, 114.5, 98.3, 93.6, 87.5, 85.1,
42.8; 19F NMR (282 MHz, DMSO-d6) d ꢀ74.4; IR (neat) n (cmꢀ1) 3362, 3090,
2215, 1722, 1542, 1350, 1220, 1180, 835. Anal. calcd. for C28H17F6N3O4: C, 58.65;
H, 2.99; N, 7.33. Found: C, 58.52; H, 3.00; N, 7.16.
1,4-Bis[3’-pyridylethynyl]-2-nitrobenzene (4j)
1
Yield: 80%; H NMR (CDCl3, 300 MHz) d 8.84 (d, J ¼ 8.4 Hz, 2 H), 8.63 (d,
J ¼ 3.9 Hz, 2 H), 8.28 (d, J ¼ 0.6 Hz, 1 H), 7.91–7.84 (m, 2 H), 7.75 (m, 2H),
7.37–7.27 (m, 2H); 13C NMR (75 MHz, CDCl3) d 152.5, 152.4, 149.7, 149.5,
139.0, 138.7, 135.5, 134.7, 127.8, 123.9, 123.2, 119.4, 119.2, 117.8, 95.4, 90.3, 89.8,
87.7 IR (neat) n (cmꢀ1) 3040, 2220, 1542, 1520, 1411, 1350, 1020, 800. Anal. calcd.
for C20H11N3O2: C, 73.84; H, 3.41; N, 12.92. Found: C, 73.71; H, 3.35; N, 12.72.
1,4-Bis[4’-pyridylethynyl]-2-trifluoromethylbenzene (4k)
1
Yield: 75%; H NMR (CDCl3, 300 MHz) d 8.66 (dd, J1 ¼ 6.3 Hz, J2 ¼ 0.6 Hz,
4 H), 7.89 (s, 1 H), 7.70 (s, 2 H), 7.39 (dd, J1 ¼ 4.5 Hz, J2 ¼ 1.8 Hz, 4 H); 13C NMR

1630
Z.-L. ZHOU ET AL.
(75 MHz, CDCl3) d 149.9, 134.5, 134.1, 132.5, 132.1, 132.0, 130.3, 129.4, 128.6,
128.4, 125.5, 124.7, 123.1, 121.2, 120.9, 93.9, 91.6, 90.0, 88.9; 19F NMR (282 MHz,
CDCl3) d ꢀ62.6; IR (neat) n (cmꢀ1) 3041, 2220, 1590, 1142, 1050, 814. Anal. calcd.
for C21H11F3N2: C, 72.41; H, 3.18; N, 8.04. Found: C, 72.42; H, 3.18; N, 7.54.
1,4-Bis[3’-pyridylethynyl]-2-trifluoromethylbenzene (4l)
Yield: 85%; 1H NMR (CDCl3, 300 MHz) d 8.79 (s, 2 H), 8.59 (m, 2 H),
7.87–7.81 (m, 3 H), 7.69 (s, 2 H); 13C NMR (75 MHz, CDCl3) d 152.3, 149.2,
149.3, 138.6, 134.3, 133.9, 132.2, 132.1, 132.0, 131.9, 129.2, 129.1, 128.6, 128.4,
124.8, 123.1, 120.7, 119.6 93.4, 90.8, 89.3, 88.2; 19F NMR (282 MHz, CDCl3) d
ꢀ62.6; IR (neat) n (cmꢀ1) 3040, 2220, 1510, 1180, 1110, 800. Anal. calcd. for
C21H11F3N2: C, 72.41; H, 3.18; N, 8.04. Found: C, 71.97; H, 3.17; N, 7.78.
REFERENCES
1. Sonogashira, K.; Tohda, Y.; Hagihara, N. A convenient synthesis of acetylenes: Catalytic
substitutions of acetylenic hydrogen with Bromoalkenes, iodoarenes and bromopyridines.
Tetrahedron Lett. 1975, 16, 4467–4470
2. Moore, J. S. Shape-persistent molecular architectures of nanoscale dimension. Acc. Chem.
Res. 1997, 30, 402–413.
3. Tour, J. M. Molecular electronics: Synthesis and testing of components. Acc. Chem. Res.
2000, 33, 791–804.
4. (a) Pugh, V. J.; Hu, Q.-S.; Zuo, X.; Lewis, F. D.; Pu, L. Optically active BINOL core-
based phenyleneethynylene dendrimers for the enantioselective fluorescent recognition
of amino alcohols. J. Org. Chem. 2001, 66, 6136–6140; (b) Hu, Q.-S.; Pugh, V.; Sabat,
M.; Pu, L. Structurally rigid and optically active dendrimers. J. Org. Chem. 1999, 64,
7528–7536.
5. Wan, W. B.; Haley, M. M. Carbon networks based on dehydrobenzoannulenes. 4:
Synthesis of ‘‘star’’ and ‘‘trefoil’’ graphdiyne substructures via sixfold cross-coupling of
hexaiodobenzene. J. Org. Chem. 2001, 66, 3893–3901.
6. Hill, D. J.; Mio, M. J.; Prince, R. B.; Hughes, T. S.; Moore, J. S. A field guide to folda-
mers. Chem Rev. 2001, 101, 3893–4012
7. Bunz, U. H. F. Poly(aryleneethynylene)s: Syntheses, properties, structures, and applica-
tions. Chem. Rev. 2000, 100, 1605–1644.
8. (a) Eaborn, C.; Walton, D. R. M. The alkali cleavage of some (phenylethynyl)-silanes and
germanes. J. Organomet. Chem. 1965, 4, 217–228; (b) Eastmond, R.; Johnson, T. R.;
Walton, D. R. M. Silylation as a protective method for terminal alkynes in oxidative cou-
=
plings: A general synthesis of the parent polyynes H(C C)nH (n ¼ 4–10, 12). Tetrahedron
1972, 28, 4601–4616; (c) Denmark, S. E.; Sweis, R. F. Organosilicon compounds in
cross-coupling reactions. A. de Meijere and F. Diederich (Eds.); In Metal-Catalyzed
Cross-Coupling Reactions; Wiley-VCH: Weinheim, 1998; Chapter 4, pp. 163–216.
9. (a) Hatanaka, Y.; Matsui, K.; Hiyama, T. A one-pot synthesis of conjugated dienynes by
palladium-mediated three-component cross-coupling reaction. Tetrahedron Lett. 1989, 30,
2403–2406. (b) Chang, S.; Yang, S. H.; Lee, P. H. Pd-catalyzed cross-coupling of alkynyl-
silanols with iodobenzenes. Tetrahedron Lett. 2001, 42, 4833–4835. (c) Li, G.; Wang, X.;
Wang, F. A novel in situ deprotection=coupling and iterative divergent=convergent
strategy for the synthesis of oligo(1,4-phenyleneethynylene)s. Tetrahedron Lett. 2005,
46, 8971–8973; (d) Sorensen, U. S.; Pombo-Villar, E. Copper-free palladium-catalyzed

BIS(ARYLETHYNYL)BENZENE DERIVATIVES
1631
Sonogashira-type coupling of aryl halides and 1-aryl-2-(trimethylsilyl)acetylenes. Tetra-
hedron 2005, 61, 2697–2703; (e) Sommer, W. J.; Weck, M. Poly(norbornene)-supported
N-heterocyclic carbenes as ligands in catalysis. Adv. Synth. Catal. 2006, 348, 2101–2113;
(f) Gil-Molto, J.; Najera, C. Direct coupling reactions of alkynylsilanes catalyzed by
Palladium(II) chloride and a di(2-pyridyl)methylamine-derived palladium(II) chloride
complex in water and in NMP. Adv. Synth. Catal. 2006, 348, 1874–1882; (g) Gopinathan,
M. B.; Rehder, K. S. An improved synthesis of (4-f4-hydroxy-3-isopropyl-5-
[(4-nitrophenyl)ethynyl]benzylg-3,5-dimethylphenoxy)acetic acid (NH-3). Synthesis 2009,
1428–1430 (h) Nishihara, Y.; Inoue, E.; Ogawa, D.; Okada, D.; Noyori, S.; Takagi, K.
Palladium=copper-catalyzed sila–Sonogashira reactions of aryl iodides with alkynylsilanes
via a direct C–Si bond activation. Tetrahedron Lett. 2009, 50, 4643–4646; (i) Nishihara,
Y.; Ikegashira, K.; Hirabayashi, K.; Ando, J.; Mori, A.; Hiyama, T. Coupling reactions
of alkynylsilanes mediated by a Cu(I) salt: Novel syntheses of conjugate diynes and dis-
ubstituted ethynes. J. Org. Chem. 2000, 65, 1780–1787; (j) Nishihara, Y.; Inoue, E.;
Okada, Y.; Noyori, S.; Takagi, K. Sila–Sonogashira cross-coupling reactions of activated
aryl chlorides with alkynylsilanes. Synlett 2008, 3041–3045.
10. Elangovan, A.; Wang, Y. H.; Ho, T.-I. Sonogashira coupling reaction with diminished
homocoupling. Org. Lett. 2003, 5, 1841–1844.