Ultrasound-assisted synthesis of functionalized 1,3-enynes by palladium-catalyzed cross-coupling reaction of α-styrylbutyltelluride with alkynyltrifluoroborate salts

Article abstract of DOI:10.1055/s-2008-1078507

An ultrasound-assisted synthesis of functionalized 1,3-enyne scaffolds is described and illustrated by palladium-catalyzed cross-coupling of potassium alkynyltrifluoroborate salts and α-styrylbutyltellurides. This procedure offers easy access to 1,3-enyne

Full text of DOI:10.1055/s-2008-1078507

LETTER
1889
Ultrasound-Assisted Synthesis of Functionalized 1,3-Enynes by Palladium-
Catalyzed Cross-Coupling Reaction of a-Styrylbutyltelluride with
Alkynyltrifluoroborate Salts
S
ynthesis of
F
a
unctionalize
t
d 1,3-E
e
nynes h Veer Singh,a Minéia Weber,b Rafael Carlos Guadagnin,a Hélio A. Stefani*a,b
a
Departamento de Farmácia, Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo, SP, Brazil
Fax +55(11)8154418; E-mail: hstefani@usp.br
Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil
b
Received 17 March 2008
or rhodium-catalyzed dimerization of terminal alkynes
but these approaches were associated with the mixture of
isomers.19 Recently, Santelli and his research group has
reported the tetraphosphine–palladium-catalyzed synthe-
Abstract: An ultrasound-assisted synthesis of functionalized 1,3-
enyne scaffolds is described and illustrated by palladium-catalyzed
cross-coupling of potassium alkynyltrifluoroborate salts and a-
styrylbutyltellurides. This procedure offers easy access to 1,3-enyne
architecture that contains aliphatic and aromatic groups in good to sis of enynes using vinyl bromides with terminal alkynes
as coupling moieties.20
excellent yields.
Key words: cross-coupling reaction, 1,3-enyne, a-styrylbutyltellu-
ride, potassium alkynyltrifluroborate salts
Most of the available methodologies for the synthesis of
enyne systems suffered by low yield, harsh reaction con-
ditions, and formation of some undesired side prod-
ucts.17,18 Thus, there is a need to develop an expedient
Functionalized enyne scaffolds play an important role in
the biosynthesis of several polyacetylenic compounds in
the plants that belongs to Apiaceae, Araliaceae and Aster-
aceae family.1,2 These polyacetylenic systems are com-
mon structural features found in many biologically
important synthetic and natural products.3–5 Molecules
embedded with these scaffolds are known to exhibit di-
verse pharmacological activities such as antibiotic6 and
anticancer.7 Naturally occurring acetylenes have attracted
wide interest during the past two decades. Even though
these scaffolds have been studied by many research
groups for more than a century, but the most exciting re-
sults were obtained after 1980, through the discovery of a
new antibiotic family, the so called enediyne antibiot-
ics.8–12 In addition, these scaffolds are fascinating and
challenging research objects in order to explore their in-
trinsic photophysical and photochemical properties.
route for the synthesis of these systems that could offer an
economical route with the flexibility of introducing the
electron-donor or -acceptor groups into their molecular
architecture.
Recently, Molander and his group introduced potassium
organotrifluoroborate salts as a nucleophilic partner in the
Suzuki–Miyaura reaction instead of unstable organoboron
reagents.21 These reagents are readily prepared by addi-
tion of KHF2 salt to an organoboron intermediates,22 and
they were monomeric, crystalline compounds that were
easily handled and indefinitely stable to moisture and air.
Organotellurium compounds have successfully been used
in several metal-assisted cross-coupling reactions as alter-
native of halogens.23,24 Recently, we reported the synthe-
sis of biaryls, stereodefined stilbenes and 1,3-dienes,
using organotellurium compounds as alternative of halo-
gens in cross-coupling reactions.25 Tellurium compounds
containing halides moiety in their structures exhibited
high chemoselectivity. Reaction occurred exclusively at
the telluride moiety, and none at the halide.25a,b
Our recent efforts25b,26 indicated that the metal-assisted
cross-coupling reaction of potassium organotrifluorobo-
rate salts and organotellurium compounds can be success-
fully achieved in few minutes by using ultrasonic waves
as a source of energy.
Numerous synthetic methodologies are available for the
synthesis of enyne13 units which involves the chemoselec-
tive triple-bond reduction of conjugated unsymmetrical
diacetylene systems by using sodium borohydride,14 flash
vacuum pyrolysis of N-propargyloxadiazolinone through
a quartz tube,15 by the reaction of 2-furyllithium with b-
bromostyrene in the presence of palladium catalyst,16 and
palladium-catalyzed cross-coupling reaction of haloalk-
enes and haloalkynes with 1-alkenyldisiamylboranes or 1-
alkenyl-1,3,2-benzodioxaboroles in the presence of bases
such as sodium alkoxides.17 In last decade Montevecchi
and his research group reported the synthesis of enynes by
DDQ-prompted oxidation of phenylalkylacetylenes.18 In
last few decades, some research groups have paid their at-
tention on the synthesis of enyne scaffolds by palladium-
The ultrasound effects are attributed to a physical process
called cavitation.27
Herein, we report an alternative approach for the synthesis
of 1,3-enyne systems in high yields by the Suzuki–
Miyaura reaction of potassium alkynyltrifluoroborate
salts and a-styrylbutyltelluride. The strength of the proce-
dure lies in the formation of C–C bond and introduction of
aliphatic and aromatic functionalities into their molecular
architecture.
SYNLETT 2008, No. 12, pp 1889–1893
x
x
.x
x
.2
0
0
8
Advanced online publication: 19.06.2008
DOI: 10.1055/s-2008-1078507; Art ID: S02508ST
© Georg Thieme Verlag Stuttgart · New York

1890
F. V. Singh et al.
LETTER
Table 1 Suzuki–Miyaura Reaction of a-n-Butyltelluro Styrene and Potassium Alkynyltrifluoroborate Salts
Et3N (2 equiv), Pd(PPh3)4
R
BF3K
Ten-Bu
+
R
AgOAc (1 equiv), MeOH
ultrasonic
1
2
3
Entry
1
Alkynyltrifluoroborate salts 2
Products 3
Reaction time (min) Yield (%)
BF3K
20
20
20
20
20
79
85
70
73
74
2a
3a
MeO
2
3
4
5
BF3K
OMe
2b
2c
2d
3b
3c
3d
3e
BF3K
Si
Si
O
O
BF3K
OMe
BF3K
OMe
2e
2f
BF3K
6
7
20
20
79
74
3f
MeO
BF3K
OMe
2g
3g
Si
BF3K
8
20
77
2h
3h
Our approach to prepare functionalized 1,3-enyne deriva- yields by Grignard reaction of a-bromostyrene followed
tives 3a–h was based on metal-assisted cross-coupling re- by addition of tellurium and butylation by n-bromobu-
action of a-styrylbutyltelluride (1) with potassium tane,25a while the precursors potassium alkynyltrifluoro-
alkynyltrifluoroborate salts 2a–h. The parent precursor a- borate salts 2a–h were prepared by the lithiation of
styrylbutyltelluride (1) was conveniently prepared in high
Synlett 2008, No. 12, 1889–1893 © Thieme Stuttgart · New York

LETTER
Synthesis of Functionalized 1,3-Enynes
1891
Table 2 Suzuki–Miyaura Reaction of Potassium a-Styryltrifluoroborate Salt and Alkynylbutyltellurides
Et3N (2 equiv), Pd(PPh3)4
R
Ten-Bu
BF3K
+
R
AgOAc (1 equiv), MeOH
ultrasonic
4
5
6
Entry
1
Alkynyltellurides 5
Products 6
Reaction time (min) Yield (%)
Ten-Bu
20
20
20
73
74
68
5a
5b
5c
5d
6a
6b
6c
6d
Ten-Bu
Ten-Bu
Ten-Bu
2
3
4
20
71
alkynes followed by the addition of trimethyl borate and Further, to investigate the effect of additive, the same re-
KHF2 salt, respectively.28
action was performed with two different additives CuI and
AgOAc, but no reaction was observed with CuI while the
desired product 3a was isolate in 78% yield with AgOAc.
Further, to establish the stoichiometry of the reaction, we
performed this reaction with two equivalents of AgOAc
but the reaction leads to the formation of side products. In-
terestingly, no reaction was observed in the absence of ad-
ditive.
Initially, we paid our attention on the determination of the
optimal conditions for the Suzuki–Miyaura reaction of a-
styrylbutyltelluride (1) and potassium alkynyltrifluorobo-
rate salts 2a–h. Toward this end, a-styrylbutyltelluride (1)
and potassium phenylethynyltrifluoroborate salt (2a)
were chosen as model substrates and a variety of condi-
tions were screened. The reactions were monitored by
TLC or GC.
The role of silver acetate can be attributed to the removal
of phosphine ligands of the catalyst or from one of the cat-
alytic intermediates formed in the course of the reac-
tion.25a The catalyst loadings were analyzed and the best
result was afforded with 10 mol% of Pd(PPh3)4 (79%
yield).
First of all, to determine the appropriate palladium cata-
lyst, we performed two reactions with two different palla-
dium catalysts Pd(Acac)2 and Pd(PPh3)4 in which Ag2O
was used as additive, K2CO3 as base, and methanol as sol-
vent, but no reaction was observed with Pd(Acac)2 while
with Pd(PPh3)4 the desired compound 3a (1,3-enyne de- During the optimization studies for 1,3-enyne derivative
rivative) was isolated in 64% yield.
3a, it was observed that the reaction mixture of 1.0 equiv-
alent of a-styrylbutyltelluride (1), 1.0 equivalent of potas-
sium phenylethynyltrifluoroborate salt (2a), 1.0
equivalent of AgOAc, 2 equivalents of triethylamine, and
10 mol% of Pd(PPh3)4 in methanol irradiated under ultra-
sonic waves for 20 minutes, was found the best conditions
for the synthesis of enyne derivative 3a. After achieving
the best conditions for the synthesis of desired compound
3a, there was synthesized a series of these functionalized
1,3-enynes 3a–g using the optimized conditions in 70–
The next step was the determination of the best base and
the necessity of an additive in the reaction. Initially was
used inorganic base as potassium carbonate in the pres-
ence of Ag2O and the desired compound was isolated in
64% yield. When the same reaction was performed with
an organic base, triethylamine, the desired compound was
achieved in 72% yield. Further to check the effect of base
we performed the same reaction without base, but no re-
action was observed.
Synlett 2008, No. 12, 1889–1893 © Thieme Stuttgart · New York

1892
F. V. Singh et al.
LETTER
(7) (a) Nicolaou, K. C.; Dai, W. M.; Tsay, S. C.; Estevez, V. A.;
Wrasidlo, W. Science 1992, 256, 1172. (b) Lee, M. D.;
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3464.
85% yields (see Table 1). After completion the reaction
mixture was poured into water and neutralized with am-
monium chloride solution followed by the extraction with
ethyl acetate. The crude product thus obtained was puri-
fied by flash column chromatography using hexane as elu-
ent. The reaction was monitored by TLC and GC.
(9) Lee, M. D.; Dunne, T. S.; Chang, C. C.; Ellestad, G. A.;
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Further, when the same reaction was performed with po-
tassium trimethylsilylacetylenetrifluoborate salt (2h), sur-
prisingly, we did not get the desired product trimethyl(3-
phenylbut-3-en-1-ynyl)silane. No signal appeared due to
the three methyl groups attached with Si atom in 1H NMR
spectrum. The spectroscopic data of isolated compound
3h matched with 2,5-diphenylhexa-1,5-dien-3-yne. The
1H NMR spectrum of this compound showed two singlets
at d = 5.76 and 5.98 ppm, respectively, due to four hydro-
gen atoms of the terminal alkene groups and two multi-
plets appeared due to the aromatic ring. The molecular ion
peak (m/z) in GC-MS at 230 and the presence of one sig-
nal at d = 89.70 ppm (13C NMR) due to both acetylenic
carbon atoms confirmed the structure of isolated com-
pound 3h as 2,5-diphenylhexa-1,5-dien-3-yne. The for-
mation of this compound can be explained because the
trimethylsilyl group could be a viable donor in palladium-
catalyzed cross-coupling reactions.29 All the synthesized
compounds were characterized by spectroscopic analy-
ses.30
(12) Konishi, M.; Ohkuma, H.; Matsumoto, K.; Tsuno, T.;
Kamei, H.; Miyaki, T.; Oki, T.; Kawaguchi, H.; VanDuyne,
G. D.; Clardy, J. J. Antibiot. 1989, 42, 1449.
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(14) Dabdoub, M. J.; Dabdoub, V. R. Tetrahedron 1995, 51,
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(15) Shimizu, M.; Kuwajima, I. J. Org. Chem. 1980, 45, 4065.
(16) Murahashi, S.-I.; Yamamura, M.; Yanagisawa, K.-I.; Mita,
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(17) Miyaura, N.; Yamada, K.; Suginome, H.; Suzuki, A. J. Am.
Chem. Soc. 1985, 107, 972.
Further, in order to generalize this approach, n-butyltellu-
rides of functionalized alkynes25c 5a–d were prepared and
the reactions with potassium a-styryltrifluroborate salt25a
(4) were attempted. These reactions yielded, under similar
conditions, functionalized 1,3-enynes 6a–d in 68–74%
yields (see Table 2).
(18) Montevecchi, P. C.; Navacchia, M. L. J. Org. Chem. 1998,
63, 8035.
(19) (a) Komeyama, K.; Kawabata, T.; Takehira, K.; Takaki, K.
J. Org. Chem. 2005, 70, 7260. (b) Yang, C.; Nolan, S. P.
J. Org. Chem. 2002, 67, 591. (c) Ohshita, J.; Furumori, K.;
Matsuguchi, A.; Ishikawa, M. J. Org. Chem. 1990, 55, 3277.
(20) Feuerstein, M.; Chahen, L.; Doucet, H.; Santelli, M.
Tetrahedron 2006, 62, 112.
(21) (a) Molander, G. A.; Ellis, N. Acc. Chem. Res. 2007, 40,
275. (b) Stefani, H. A.; Cella, R.; Vieira, A. S. Tetrahedron
2007, 63, 3623. (c) Darses, S.; Genet, J.-P. Chem. Rev.
2008, 108, 288.
(22) (a) Vedejs, E.; Chapman, R. W.; Fields, S. C.; Lin, S.;
Schrimpf, M. R. J. Org. Chem. 1995, 60, 3020. (b) Vedejs,
E.; Fields, S. C.; Hayashi, R.; Hitchcock, S. R.; Powell, D.
R.; Schrimpf, M. R. J. Am. Chem. Soc. 1999, 121, 2460.
(23) For reviews, see: (a) Petragnani, N.; Stefani, H. A.
Tetrahedron 2005, 61, 1613. (b) Comasseto, J. V.; Ling, L.
W.; Petragnani, N.; Stefani, H. A. Synthesis 1997, 373.
(c) Zeni, G.; Braga, A. L.; Stefani, H. A. Acc. Chem. Res.
2003, 36, 731.
In summary, we have demonstrated the ultrasound-assist-
ed synthesis of functionalized 1,3-enyne systems by Suzu-
ki–Miyaura reaction of easily accessible a-styrylbutyl-
tellurides with potassium alkynyltrifluoroborate salts in-
stead of unstable organoboronic acids. Further applica-
tions of our methodology for the synthesis of
functionalized 1,3-enynes are currently in progress.
Acknowledgment
The authors are grateful to FAPESP (07/51466-9 and 05/59141-6)
and CNPq (154976/2006-7) for financial support.
(24) (a) Zeni, G.; Perin, G.; Cella, R.; Jacob, R. G.; Braga, A. L.;
Silveira, C. C.; Stefani, H. A. Synlett 2002, 975. (b) Braga,
A. L.; Lüdtke, D. S.; Vargas, F.; Donato, R. K.; Silveira, C.
C.; Stefani, H. A.; Zeni, G. Tetrahedron Lett. 2003, 44,
1779. (c) Braga, A. L.; Vargas, F.; Zeni, G.; Silveira, C. C.;
Andrade, L. H. Tetrahedron Lett. 2002, 43, 4399. (d) Zeni,
G.; Comasseto, J. V. Tetrahedron Lett. 1999, 40, 4619.
(e) Nishibayashi, Y.; Cho, C.-S.; Ohe, K.; Uemura, S.
J. Organomet. Chem. 1996, 507, 197. (f) Nishibayashi, Y.;
Cho, C.-S.; Ohe, K.; Uemura, S. J. Organomet. Chem. 1996,
526, 335.
References and Notes
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Acetylenes; Academic Press: New York, 1973.
(2) Zhu, L.; Minto, R. E. Tetrahedron Lett. 2001, 42, 3803.
(3) Matsunaga, H.; Saita, T.; Nagumo, F.; Mori, M.; Katano, M.
Cancer Chemother. Pharmacol. 1995, 35, 291.
(4) Arnaud, A. Bull. Soc. Chim. Fr. 1892, 3, 233.
(5) Willams, W. W.; Smirnow, W. S.; Golmow, W. P. Zh.
Obshch. Khim. 1935, 5, 1195.
(6) (a) Smith, A. L.; Nicolaou, K. C. J. Med. Chem. 1996, 39,
2103. (b) Edo, K.; Mizugaki, M.; Koide, Y.; Seto, H.;
Furihata, K.; Otake, N.; Ishida, N. Tetrahedron Lett. 1985,
26, 331.
(25) (a) Cella, R.; Cunha, R. L. O. R.; Reis, A. E. S.; Pimenta, D.
C.; Klitzke, C. F.; Stefani, H. A. J. Org. Chem. 2006, 71,
244. (b) Cella, R.; Stefani, H. A. Tetrahedron 2006, 62,
Synlett 2008, No. 12, 1889–1893 © Thieme Stuttgart · New York

LETTER
5656. (c) Stefani, H. A.; Cella, R.; Dörr, F. A.; Pereira, C. M.
Synthesis of Functionalized 1,3-Enynes
1893
1 H, CH), 5.92 (s, 1 H, CH), 7.27–7.39 (m, 3 H, ArH), 7.63–
7.69 (m, 2 H, ArH). 13C NMR (75.5 MHz, CDCl3): d = –
5.08, 18.32, 25.82, 52.20, 83.92, 89.35, 120.70, 125.57,
126.03, 128.30, 130.27, 137.09. IR (neat): 761.12, 789.67,
1104.28, 1218.70 cm–1. GC-MS: m/z (relative intensity, %)
= 272 (100), 257 (18), 242 (28), 167 (48).
P.; Zeni, G. Jr.; Gomes, M. Tetrahedron Lett. 2005, 46, 563.
(d) Cella, R.; Orfão, A. T. G.; Stefani, H. A. Tetrahedron
Lett. 2006, 47, 5075.
(26) (a) Pereira, C. M. P.; Stefani, H. A.; Almeida, R. B.; Braga,
R. C.; Guzen, K. P.; Cella, R. Tetrahedron Lett. 2005, 46,
6833. (b) Stefani, H. A.; Oliveira, C. B.; Almeida, R. B.;
Pereira, C. M. P.; Braga, R. C.; Cella, R.; Borges, V. C.;
Savegnago, L.; Nogueira, C. W. Eur. J. Med. Chem. 2006,
513.
(27) (a) Margulis, M. A. High Energy Chem. 2004, 38, 135.
(b) Mason, T. J. Chem. Soc. Rev. 1997, 26, 443.
(28) Paixão, M. W.; Weber, M.; Braga, A. L.; Azeredo, J. B.;
Deobald, A. M.; Stefani, H. A. Tetrahedron Lett. 2008, 49,
2366.
Dec-1-en-3-yn-2-ylbenzene (3d): colorless oil. 1H NMR
(300 MHz, CDCl3): d = 0.90 (t, J = 6.6 Hz, 3 H, Me), 1.28–
1.67 (m, 8 H, 4 CH2), 2.40 (t, J = 6.6 Hz, 2 H, CH2), 5.57 (s,
1 H, CH), 5.83 (s, 1 H, CH), 7.27–7.51 (m, 3 H, ArH), 7.62–
7.69 (m, 2 H, ArH). 13C NMR (75.5 MHz, CDCl3): d =
14.05, 19.42, 22.58, 28.65, 28.72, 31.36, 79.76, 92.10,
119.30, 126.07, 128.08, 128.25, 131.00, 137.83. IR (neat):
750.00, 773.47, 1134.53, 1227.52 cm–1. GC-MS: m/z
(relative intensity, %) = 212 (43), 197 (40), 183 (32), 169
(52), 155 (82), 141 (100), 129 (67).
(29) Denmark, S. E.; Sweis, R. F. In Metal-Catalyzed Cross-
Coupling Reactions; Meijere A., Diederich Wiley-VCH:
Weinheim, 2004, 163.
[4-(1-Methoxycyclohexyl)but-1-en-3-yn-2-yl]benzene (3e):
colorless oil. 1H NMR (300 MHz, CDCl3): d = 1.23–1.36 (m,
2 H, CH2), 1.59–1.70 (m, 6 H, 3 CH2), 1.96–2.04 (m, 2 H,
CH2), 3.53 (s, 3 H, OMe), 5.66 (s, 1 H, CH), 5.91 (s, 1 H,
(30) General Procedure for the Synthesis of 3a–h
A suspension of a-styrylbutyltelluride (1, 0.143 g, 0.5
mmol), potassium alkynyltrifluoroborate salt(2) (0.103 g,
0.50 mmol), Pd(PPh3)4 (0.055 g, 0.05 mmol), Et3N (0.101g,
1 mmol) and AgOAc (0.083 g, 0.5 mmol) in MeOH (3 mL)
was irradiated in a water bath of an ultrasonic cleaner for 20
min. Then, the reaction was diluted with EtOAc (30 mL).
The organic layer was washed with sat. solution of NH4Cl
(2 × 10 mL) and H2O (2 × 10 mL), dried over MgSO4, and
concentrated under vacuum. The crude product was purified
by flash column chromatography (SiO2) using hexane as
eluent and characterized as follows:
CH), 7.23–7.40 (m, 3 H, ArH), 7.62–7.68 (m, 2 H, ArH). 13
C
NMR (75.5 MHz, CDCl3): d = 22.92, 25.50, 36.83, 50.91,
74.41, 85.22, 91.91, 120.58, 126.00, 128.28, 128.38, 130.29,
137.33. IR (neat): 745.94, 769.78, 1127.56, 1240.67 cm–1.
GC-MS: m/z (relative intensity, %) = 240 (19), 225 (51), 197
(100), 137 (100).
(4-Cyclohexenylbut-1-em-3yn-2yl)benzene (3f): colorless
oil. 1H NMR (300 MHz, CDCl3): d = 1.61–1.69 (m, 4 H, 2
CH2), 2.11–2.24 (m, 4 H, 2 CH2), 5.61 (s, 1 H, CH), 5.87 (s,
1 H, CH), 6.21 (s, 1 H, CH), 7.29–7.36 (m, 3 H, ArH), 7.62–
7.68 (m, 2 H, ArH). 13C NMR (75.5 MHz, CDCl3): d =
21.30, 22.11, 25.55, 29.00, 85.78, 92.60, 119.41, 120.46,
125.85, 127.97, 128.08, 130.62, 135.22, 137.34. IR (neat):
754.41, 780.07, 1121.48 cm–1. GC-MS: m/z (relative
intensity, %) = 208 (100), 178 (64), 165 (55), 115 (26).
(5-Methoxy-5-methylhept-1-em-3-yn-2yl)benzene (3g):
colorless oil. 1H NMR (300 MHz, CDCl3): d = 1.03 (t,
J = 7.4 Hz, 3 H, Me), 1.46 (s, 3 H, Me), 1.69–1.88 (m, 2 H,
CH2), 3.40 (s, 3 H, OMe), 5.64 (s, 1 H, CH), 5.90 (s, 1 H,
But-3-en-1-yne-1,3-diyldibenzene (3a): yellow oil. 1H NMR
(300 MHz, CDCl3): d = 5.80 (s, 1 H, CH), 6.03 (s, 1 H, CH),
7.32–7.48 (m, 5 H, ArH), 7.54–7.61 (m, 3 H, ArH), 7.74–
7.81 (m, 2 H, ArH). 13C NMR (75.5 MHz, CDCl3): d =
88.56, 90.78, 120.67, 123.11, 126.12, 128.36, 128.42,
129.21, 130.63, 131.68, 132.51, 137.28. IR (neat): 755.84,
782.57, 1111.48, 1225.69 cm–1. GC-MS: m/z (relative
intensity, %) = 204 (100), 203 (81), 202 (92), 101 (45).
2-Methoxy-6-(3-phenylbut-3-em-1ynyl)naphthalene (3b):
colorless oil. 1H NMR (300 MHz, CDCl3): d = 3.94 (s, 3 H,
OMe), 5.80 (s, 1 H, CH), 6.00 (s, 1 H, CH), 7.11–7.20 (m, 2
H, ArH), 7.27 (s, 1 H, ArH), 7.33–7.46 (m, 3 H, ArH), 7.55
(d, J = 8.6 Hz, 1 H, ArH), 7.68–7.81 (m, 3 H, ArH), 7.99 (s,
1 H, ArH). 13C NMR (75.5 MHz, CDCl3): d = 55.38, 88.26,
91.42, 105.83, 117.99, 119.48, 120.49, 126.87, 128.10,
128.37, 128.45, 128.50, 129.04, 129.38, 130.76, 131.42,
134.23, 137.40. IR (neat): 747.75, 776.73, 1123.46, 1232.64
cm–1. GC-MS: m/z (relative intensity, %) = 284 (100), 269
(10), 241 (45), 120 (45).
CH), 7.22–7.50 (m, 3 H, ArH), 7.59–7.66 (m, 2 H, ArH). 13
NMR (75.5 MHz, CDCl3): d = 8.52, 24.87, 33.81, 51.38,
C
74.32, 84.25, 91.64, 120.39, 125.74, 128.05, 128.13, 129.99,
137.06. IR (neat): 759.83, 788.50, 1105.48, 1236.67 cm–1.
GC-MS: m/z (relative intensity, %) = 214 (4), 199 (8), 185
(100).
Hexa-1,5-dien-3yne-2,5-diyldibenzene (3h): colorless oil.
1H NMR (300 MHz, CDCl3): d = 5.76 (s, 2 H, 2 CH), 5.98
(s, 2 H, 2 CH), 7.22–7.50 (m, 6 H, ArH), 7.59–7.66 (m, 4 H,
ArH). 13C NMR (75.5 MHz, CDCl3): d = 89.70, 120.84,
125.89, 128.15, 128.22, 130.36, 137.00. IR (neat): 743.60,
778.43, 1134.56, 1234.54 cm–1. GC-MS: m/z (relative
intensity, %) = 230 (100), 215 (40), 202 (17), 115 (49).
tert-Butyldimethyl(4-phenylpent-4-en-2-ynyloxy)silane
(3c): colorless oil. 1H NMR (300 MHz, CDCl3): d = 0.17 (s,
6 H, 2 Me), 0.93 (s, 9 H, 3 Me), 4.55 (s, 2 H, CH2), 5.66 (s,
Synlett 2008, No. 12, 1889–1893 © Thieme Stuttgart · New York

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