Synthesis of symmetrical 1,3-diynes via homocoupling reaction of n-butyl alkynyltellurides

Article abstract of DOI:10.1016/j.tetlet.2009.03.078

An ultrasound-assisted synthesis of symmetrical 1,3-diyne compounds with electron-withdrawing or -donating substituents is described and illustrated by the palladium-catalyzed homocoupling reaction of n-butyl alkynyltellurides. This procedure offers easy

Full text of DOI:10.1016/j.tetlet.2009.03.078

Tetrahedron Letters 50 (2009) 2636–2639
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthesis of symmetrical 1,3-diynes via homocoupling reaction of n-butyl
alkynyltellurides
Fateh V. Singh a, Mônica F. Z. J. Amaral a, Hélio A. Stefani a,b,
*
a Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, Av. Prof. Lineu Prestes 580, São Paulo 05508-900, Brazil
b Departamento de Biofisica, Universidade Federal de São Paulo, SP, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
An ultrasound-assisted synthesis of symmetrical 1,3-diyne compounds with electron-withdrawing or -
donating substituents is described and illustrated by the palladium-catalyzed homocoupling reaction
of n-butyl alkynyltellurides. This procedure offers easy access to 1,3-diynes in very short reaction times,
and the products are achieved in good to excellent yields.
Received 14 January 2009
Revised 26 February 2009
Accepted 11 March 2009
Available online 16 March 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Homocoupling reaction
Symmetrical 1,3-diynes
Alkynyltellurides
Symmetrical and unsymmetrical alkynes play an important role
as building blocks in many synthetic transformations, and in new
materials such as conjugated oligomers and polymers, liquid crys-
tals, non-linear materials, molecular wires, and in other engineer-
ing materials.1 Several symmetrical 1,3-diynes have been
exclusively used as equivalents to other functional groups in syn-
thetic organic chemistry.2 In addition, these 1,3-diynes are com-
mon structural motifs found in various natural products3 and
important biological activities, specially antifungal activity.4 In
the past two decades, 1,3-diynes have been recognized as an
important functionality in organic molecular materials such as
molecular wires and molecular architecture on the nanometer
scale.5 Therefore, the need for efficient and concise syntheses of
diynes having desired functionalities is evident in natural product
chemistry as well as in the discovery of new pharmaceutical
agents.
Carbon–carbon bond formation for the preparation of symmet-
rical and unsymmetrical diyne compounds is one of the most use-
ful and important tools in modern organic chemistry. The
construction of diynes can be achieved either by intermolecular-
or by intramolecular cross-coupling of two similar or dissimilar
alkynylic functionalities in the presence of organo-metal com-
plexes. Palladium-catalyzed cross-coupling reactions between the
electrophilic compounds Ar–X (X being mainly Cl, Br, I and OTf)
and organometallic species Ar–M (M being Mg, Zn, Sn, and B) are
on the verge of truly becoming a general process for the construc-
tion of diyne systems.
Numerous synthetic approaches are available for the synthesis
of symmetrical 1,3-diynes in the literature, which include the tra-
ditional oxidative homocoupling of terminal acetylenes such as
Cadiot–Chodkiewicz,6 Eglington,7 Glaser,8 Hay,2b Sonogashira cou-
plings9 and the Pd(0)–Cu(I) catalyzed self-coupling of terminal al-
kynes in the presence of chloroacetone,10 iodine,11 allyl bromide,12
and ethyl bromoacetate.13 Recently, Cahiez14 and others15 demon-
strated the efficiency of the iron-catalyzed homocoupling of alky-
nyl Grignard reagents using 1,2-dihalogenoethanes as oxidants.
Following this, Knochel16 described the elegant transition-metal-
free homocoupling reaction of organomagnesium compounds by
direct oxidation with 3,30,5,50-tetra-tert-butyl-4,40-diphenoqui-
none. However, for industrial applications, these methods are lim-
ited since they require
a stoichiometric amount of organic
oxidant.17 Recently, we reported the synthesis of 1,3-diyne sys-
tems by the Cu-mediated homocoupling of potassium alkynylic tri-
fluoroborate salts.18
In the current decade, organotellurium compounds have at-
tained remarkable development as synthons and intermediates in
synthetic organic chemistry. Organotellurium compounds have
been used instead of halogens as electrophilic partners in some
palladium-catalyzed cross-coupling reactions.19,20 Uemura and
his research group21 demonstrated the palladium-catalyzed homo-
coupling of some organotellurides, such as alkenyl and aryl tellu-
rides, but this approach was associated with poor yields and the
formation of some undesired side products. It was also disclosed
that homocoupling hardly occurred with tellurides such as diaryl,
alkyl aryl, dialkyl and alkynyl aryl tellurides, even in the presence
of a stoichiometric amount of palladium salts and at higher tem-
perature.21a Barton and his research group22 also reported the
* Corresponding author. Tel.: +55 11 818 3654; fax: +55 11 3 815 4418.
E-mail address: hstefani@usp.br (H.A. Stefani).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.03.078

F. V. Singh et al. / Tetrahedron Letters 50 (2009) 2636–2639
2637
homocoupling of some organotellurides but the experimental de-
tails are not available.
Recently, we have achieved the palladium-catalyzed homocou-
pling of n-butyl aryltellurides successfully in minutes by using
ultrasonic waves as a source of energy.23 The ultrasound effects
are attributed to a physical process called cavitation.24
Herein, we report a new protocol for the synthesis of 1,3-diyne
systems by the palladium-catalyzed homocoupling of functional-
ized n-butyl alkynyltellurides using ultrasonic waves as a source
of energy. The strength of the procedure lies in formation of the
C–C bond and in the introduction of electron-donor or -acceptor
functionalities into the molecule.
The approach to prepare 1,3-diyne compounds 2a–j was based
on the palladium-catalyzed homocoupling reaction of functional-
ized n-butyl alkynyltellurides 1a–j. The parent precursors n-butyl
alkynyltellurides 2a–j were conveniently prepared in high yields
by the lithiation of terminal alkynes followed by the addition of
metallic tellurium and n-bromobutane.25
Initially, we paid attention to the determination of the optimal
conditions for the homocoupling of alkynyltelluride 1. Toward this
end, n-butyl phenylacetylenic telluride 1a was chosen as a model
substrate and a variety of conditions were screened (Table 1).
The reactions were monitored by TLC or GC.
In order to find an appropriate catalyst for the homocoupling
of n-butyl phenylacetylenic telluride 1a, we tested several reac-
tions with palladium and non-palladium catalysts. The reactions
with the palladium catalysts were successful in most cases. The
Pd(II) and (0) species were used in these homocoupling reactions
and the best result was obtained with PdCl2 (Table 1, entry 2).
AgOAc was used as an additive, triethylamine used as the base,
and methanol used as the solvent. The reaction was irradiated
for 20 min in an ultrasound bath. The product was obtained in
95% yield.
The next step was the determination of the best base and the
necessity of an additive in the reaction. Initially, organic bases such
as triethylamine and diisopropyl ethyl amine (DIPEA) were used in
the presence of AgOAc and the desired compound was observed in
98 and 95% yields respectively (Table 2, entries 2 and 8). When the
same reaction was performed with an inorganic base, such as so-
dium carbonate, the desired compound was achieved in 92% yield
(Table 2, entry 7). In order to verify the effect of the base we per-
formed the same reaction without base, but no reaction was ob-
served (Table 2, entry 6).
In order to investigate the effect of the additive, the same reac-
tion was performed with three different additives, mainly AgOAc,
Ag2O, and CuI, and the desired product 2a was achieved in 98, 31
and 67% yields, respectively (Table 2, entries 2–4). To establish
the stoichiometry of the reaction, we performed this reaction with
two equivalents of Ag2OAc, and the desired compound was
achieved in 81% yield (Table 2, entry 5). No reaction was observed
in the absence of additive (Table 2, entry 1).
In order to achieve the best solvent, we performed different
reactions with different kinds of solvents. The best result was
achieved with a polar protic solvent (methanol) in 98% yield (Table
3, entry 1). The optimizations results with different solvents are
described in Table 3.
During the optimization studies for 1,4-diphenylbuta-1,3-diyne
2a, it was observed that the reaction mixture containing 1.0 equiv
of n-butyl phenylacetylenic telluride 1a, 1.0 equiv of Ag2OAc,
2.0 equiv of triethylamine, and 8 mol % of PdCl2 in methanol, irra-
diated under ultrasonic waves for 15 min, was the best for the syn-
thesis of 1,4-diphenylbuta-1,3-diyne 2a. After achieving the best
conditions for the synthesis of the desired compound 2a, we syn-
thesized a series of symmetrical 1,3-diyne compounds 2a–j using
the optimized conditions in 77–91% yields (see Table 4). Interest-
ingly this reaction worked nicely with both aliphatic and aromatic
acetylenic tellurides. All synthesized compounds were character-
ized by spectroscopic analysis.32
Table 1
Study of the effect of a catalyst on the homocoupling of n-butyl phenylacetylenic
telluride 1a
Et3N, PdCl2 (8%)
Te Bu -n
AgOAc, MeOH
Ultrasonic
1a
2a
Entry
Catalysta
Yieldb (%)
On the basis of available literature21a we propose a possible cat-
alytic cycle for the homocoupling reaction of n-butyl alkynyltellu-
rides as described in Figure 1. According to this cycle, the reaction
proceeds with the formation of a telluride-palladium(II) complex
(A) followed by the transmetallation of the alkynyl group to give
the alkynyl palladium species (B), which reacts with another alky-
nyltelluride molecule to give a dialkynyl palladium intermediate
(C). On reductive elimination the intermediate C undergo homo-
coupling to give product 2 and Pd. The palladium species is later
oxidized with AgOAc to give palladium(II) thus completing the cy-
cle. We observed the formation of dibutyltelluride in trace
amounts by GC–MS.
1
2
3
4
5
6
7
8
—
PdCl2
nr
95
88
91
nr
71
60
92
PdCl2(BzCN)2
Pd(PPh3)4
CuI
PdCl2(dppf)CH2Cl2
Fe(Acac)3
Pd(OAc)2
a
10 mol % of catalyst was used.
The yield was determined by GC analysis.
b
In summary, we have demonstrated the ultrasound-assisted
synthesis of alkyl and aryl substituted 1,3-diynes by the homocou-
pling reaction of easily accessible alkynyltellurides. This methodol-
ogy has the flexibility of introducing electron-donor or -acceptor
Table 2
Study of the effects of additive and base on the homocoupling of n-butyl
phenylacetylenic telluride 1a
Entry
Base
Additive (equiv)
Pd(PPh3)4 (mol %)
Yielda (%)
1
2
3
4
5
6
7
8
9
Et3N
Et3N
Et3N
Et3N
Et3N
—
Na2CO3
DIPEA
Et3N
Et3N
—
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (10)
PdCl2 (5)
nr
Table 3
AgOAc (1)
Ag2O (1)
CuI (1)
AgOAc (2)
AgOAc (1)
AgOAc (1)
AgOAc (1)
AgOAc (1)
AgOAc (1)
98
31
67
81
nra
92
95
71
98
Study of the solvent effect on the homocoupling of n-butyl phenylacetylenic telluride
1a
Entry
Solvent
Yielda (%)
1
2
3
4
MeOH
MeCN
THF
98
21
10
19
10
PdCl2 (8)
Dioxane
a
a
The yield was determined by GC analysis.
The yield was determined by GC analysis.

2638
F. V. Singh et al. / Tetrahedron Letters 50 (2009) 2636–2639
Table 4
Homocoupling reaction of functionalized n-butyl alkynyltellurides 1a–j
Et3N, PdCl2 (8%)
R
TeBu- n
R
R
AgOAc, MeOH
Ultrasonic
1
2
Entry
a
Alkynyltellurides
Products
Reaction time (min)
15
Yieldsa (%)
85
TeBu - n
b
c
20
15
87
85
Me
TeBu- n
Me
Me
n-C5H11
TeBu- n
TeBu- n
n-C5H11
n-C5H11
OMe
MeO
MeO
d
e
20
20
91
82
TeBu- n
f
20
15
20
20
20
87
75
80
77
85
n-C3H7
n-C4H9
n-C5H11
TeBu- n
TeBu- n
TeBu- n
n-C3H7
n-C4H9
n-C5H11
n-C3H7
g
h
i
n-C4H9
n-C5H11
Si
TeBu- n
Si
Si
j
MeOH2C
TeBu - n
MeOH2C
CH2OMe
a
Isolated yields.
Acknowledgments
R
TeBu -n
AgOAc
PdCl2
The authors are indebted to CNPq (300613/2007-5) and FAPESP
(07/59404-2 and 07/51466-9) for financial support.
Pd0
R
R
[(R
[(R
Te Bu-n).PdCl2]2
or
References and notes
Te Bu-n)2.PdCl2
1. (a) Hunstman, V. D. In The Chemistry of the Carbon–Carbon Triple Bond; Patai, S.,
Ed.; Wiley-Interscience: London, 1978; p 553; (b) Diederich, F.; Stang, P. J.;
Tykwinski, R. R. Acetylene Chemistry: Chemistry, Biology, and Material Science;
Wiley-VCH: Weinheim, 2005; (c) Bunz, U. H. F. Chem. Rev. 2000, 100, 1605; (d)
Tour, J. M. Acc. Chem. Res. 2000, 33, 791; (e) Martin, R. E.; Diederich, F. Angew.
Chem., Int. Ed. 1999, 38, 1350; (f) Tour, J. M. Chem. Rev. 1996, 96, 537; (g) Stang,
P. J.; Diederich, F. Modern Acetylene Chemistry; Wiley-VCH: Weinheim, 1995.
2. For general reviews on coupling reactions between a sp carbon center, see: (a)
Sonogashira, K.. In Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon
Press: New York, 1991; Vol. 3, p 551; (b) Hay, A. S. J. Org. Chem. 1962, 27, 3320;
(c) Jones, G. E.; Kendrick, D. A.; Holmes, A. B. Org. Synth. 1987, 65, 52;; (d)
Valenti, E.; Pericas, M. A.; Serratosa, F. J. Am. Chem. Soc. 1990, 112, 7405;; (e)
Kitamura, T.; Lee, C. H.; Taniguchi, Y.; Fujiwara, Y. J. Am. Chem. Soc. 1997, 119,
619;; (f) Siemsen, P.; Livingston, R. C.; Diederich, F. Angew. Chem., Int. Ed. 2000,
39, 2632.
(A)
R
Pd
R
(C)
TeCl2
R
TeCl
R
TeC l
Pd-Cl
R
(B)
Figure 1. Possible catalytic cycle of the homocoupling reaction of n-butyl
alkynyltellurides.
functionalities in the 1,3-diynes. Further applications of our meth-
odology for the synthesis of substituted diynes are currently in
progress.
3. (a) Li, Y.-L.; Li, J.; Wang, N.-L.; Yao, X.-S. Molecules 2008, 13, 1931; (b) Cho, E. J.;
Lee, D. Org. Lett. 2008, 10, 257; (c) Kanokmedhakul, S.; Kanokmedhakul, K.;

F. V. Singh et al. / Tetrahedron Letters 50 (2009) 2636–2639
2639
Kantikeaw, I.; Phonkerd, N. J. Nat. Prod. 2006, 69, 68; (d) Holmes, A. B.;
Jennings-White, C. L. D.; Kendrick, D. A. J. Chem. Soc., Chem. Commun. 1983, 415;
(e) Nicolaou, K. C.; Zipkin, R. E.; Dolle, R. E.; Harris, B. D. J. Am. Chem. Soc. 1984,
106, 3548; (f) Crombie, L.; Hobbs, A. J. W.; Horsham, M. A. Tetrahedron Lett.
1987, 28, 4875; (g) Holmes, A. B.; Tabor, A. B.; Baker, R. J. Chem. Soc., Perkin
Trans. 1 1991, 3307; (h) Hoye, T. R.; Chanson, P. R. Tetrahedron Lett. 1993, 34,
5043.
507, 197; (c) Uemura, S.; Takahashi, H.; Ohe, K. J. Organomet. Chem. 1992, 423,
C9.
22. Barton, D. H. R.; Ozbalik, N.; Ramesh, M. Tetrahedron Lett. 1988, 29, 3533.
23. Singh, F. V.; Stefani, H. A. Synlett 2008, 3221.
24. Margulis, M. A. High Energy Chemistry 2004, 38, 135; (a) Mason, T. J. Chem. Soc.
Rev 1997, 26, 443.
25. Dabdoub, M. J.; Comasseto, J. V. Organometallics 1988, 7, 84.
4. Stuts, A. Angew. Chem., Int. Ed. Engl. 1987, 26, 320.
26. Yadav, J. S.; Reddy, B. V. S.; Reddy, K. B.; Gayathri, K. U.; Prasad, A. R.
Tetrahedron Lett. 2003, 44, 6493.
27. Li, J.-H.; Liang, Y.; Xie, Y.-X. J. Org. Chem. 2005, 70, 4393.
28. Yang, F.; Cui, X.; Li, Y.; Zhang, J.; Rena, G.; Wua, Y. Tetrahedron 2007, 63, 1963.
29. Li, J.-H.; Liang, Y.; Zhang, X. D. Tetrahedron 2005, 61, 1903.
30. Woltermann, C. J.; Shechter, H. Helv. Chim. Acta 2005, 88, 354.
31. Blangetti, M.; Deagostino, A.; Rosso, H.; Prandi, C.; Zavattaro, C.; Venturello, P.
Eur. J. Org. Chem. 2007, 5867.
5. (a) Fouquey, C.; Lehn, J.-M.; Malthete, J. J. Chem. Soc., Chem. Commun. 1987,
1424; (b) Diederich, F.; Rubin, Y.; Knobler, C. B.; Whetten, R. L.; Schriver, K. E.;
Houk, K. N.; Li, Y. Science 1989, 245, 1088; (c) Kanis, D. R.; Ratner, M. A.; Marks,
T. J. Chem. Rev. 1994, 94, 195; (d) Xu, Z.; Kaha, M.; Walker, K. L.; Wilkins, C. L.;
Moore, J. S. J. Am. Chem. Soc. 1994, 116, 4537; (e) Chang, J. Y.; Baik, J. H.; Lee, C.
B.; Han, M. J. J. Am. Chem. Soc. 1997, 119, 3197; (f) Kitamura, T.; Lee, C. H.;
Taniguchi, Y.; Fujiwara, Y. J. Am. Chem. Soc. 1997, 119, 619.
6. Cadiot, P.; Chodkiewicz, W. In Chemistry of Acetylene; Viehe, H. G., Ed.; Marcel
Dekker: New York, 1969; p 597.
7. Eglington, G.; Galbraith, R. J. Chem. Soc 1959, 889.
8. Taylor, R. J. K. Organocopper Reagents: A Practical Approach; Oxford University
Press: New York, 1994.
9. (a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 50, 4467; (b)
Sonogashira, K. In Metal-Catalyzed Cross-Coupling Reactions; Diederich, F., Stang,
P. J., Eds.; Wiley-VCH: Weinheim, Germany, 1998; pp 203–230; (c)
Sonogashira, K.. In Comprehensive Organic Synthesis; Pergamon Press, 1990;
Vol. 3. p. 521.
10. Rossi, R.; Carpita, A.; Bigelli, C. Tetrahedron Lett. 1985, 26, 523.
11. Liu, Q.; Burton, D. J. Tetrahedron Lett. 1997, 38, 4371.
12. Vlasa, M.; Ciocan-Tarta, I.; Margineanu, F.; Oprean, I. Tetrahedron 1996, 52,
1337.
13. Lei, A.; Srivastava, M.; Zhang, X. J. Org. Chem. 2002, 67, 196.
14. Cahiez, G.; Chaboche, C.; Mahuteau-Betzer, F.; Ahr, M. Org. Lett. 2005, 7, 1943.
15. Nagano, T.; Hayashi, T. Org. Lett. 2005, 7, 491; For leading references about Fe-
catalyzed cross-coupling reactions, see: (a) Cahiez, G.; Avedissian, H. Synthesis
1998, 1199; (b) Fürstner, A.; Leitner, A.; Méndez, M.; Krause, H. J. Am. Chem.
Soc. 2002, 124, 13856; (c) Duplais, C.; Bures, F.; Korn, T.; Sapountzis, I.; Cahiez,
G.; Knochel, P. Angew. Chem., Int. Ed. 2004, 43, 2968; (d) Nakamura, M.; Matsuo,
K.; Ito, S.; Nakamura, E. J. Am. Chem. Soc. 2004, 126, 3686; (e) Nagano, T.;
Hayashi, T. Org. Lett. 2004, 6, 1297; (f) Bedford, R. B.; Bruce, D. W.; Frost, R.;
Hird, M. Chem. Commun. 2005, 4161; (g) Cahiez, G.; Habiak, V.; Duplais, C.;
Moyeux, A. Angew. Chem., Int. Ed. 2007, 46, 4364; (h) Cahiez, G.; Duplais, C.;
Moyeux, A. Org. Lett. 2007, 9, 3253.
16. Krasovskiy, A.; Tishkov, A.; del Amo, V.; Mayr, H.; Knochel, P. Angew. Chem., Int.
Ed. 2006, 45, 5010.
17. Cahiez, G.; Moyeux, A.; Buendia, J.; Duplais, C. J. Am. Chem. Soc. 2007, 129,
13788.
18. Paixão, M. W.; Weber, M.; Braga, A. L.; Azeredo, J. B.; Deobald, A. M.; Stefani, H.
A. Tetrahedron Lett. 2008, 49, 2366.
32. General experimental procedure for 1,3-diyne compounds 2a–j: A suspension of
alkynyl telluride (1a) (0.1435 g, 0.5 mmol), PdCl2 (0.08 g, 8 mmol %),
triethylamine (0.101 g, 1 mmol), and silver(I) acetate (0.083 g, 0.5 mmol) in
5 mL of methanol was irradiated in a water bath of an ultrasonic cleaner for
15 min. Then, the reaction was diluted with ethyl acetate (25 mL). The organic
layer was washed with a saturated solution of NH4Cl (2 ꢀ 10 mL) and water
(2 ꢀ 10 mL), dried over MgSO4, and concentrated under vacuum. The crude
product was purified by flash silica column chromatography using hexane as
the eluent and characterized as 1,4-diphenylbuta-1,3-diyne 2a:26 white solid;
mp 86–88 °C; 1H NMR (300 MHz, CDCl3) d 7.30–7.38 (m, 6H, ArH), 7.47–7.56
(m, 4H, ArH); 13C NMR (75.5 MHz, CDCl3) d 73.74, 81.34, 121.58, 128.43,
129.48, 132.29; GC–MS (%) 202 (100), 200 (24), 150 (8), 101 (13), 88 (10).
Compound 2b:27 white solid; mp 182–184 °C; 1H NMR (300 MHz, CDCl3) d 2.31
(s, 6H, 2Me), 7.09 (d, J = 8.0 Hz, 4H, ArH), 7.36 (d, J = 8.0 Hz, 4H, ArH); 13C NMR
(75.5 MHz, CDCl3) d 21.63, 73.45, 81.55, 118.80, 129.22, 132.40, 129.50; GC–
MS (%) 230 (100), 215 (17), 115 (17), 101 (15). Compound 2c:28 white solid; mp
90–92 °C; 1H NMR (300 MHz, CDCl3) d 0.89 (t, J = 6.8 Hz, 6H, 2Me), 1.27–1.38
(m, 8H, 4CH2), 1.53–1.66 (m, 4H, 2CH2), 2.60 (t, J = 7.6 Hz, 4H, 2CH2), 7.14 (d,
J = 8.0 Hz, 4H, ArH), 7.43 (d, J = 8.0 Hz, 4H, ArH); 13C NMR (75.5 MHz, CDCl3) d
13.78, 22.29, 30.63, 31.21, 35.74, 73.27, 81.36, 118.77, 128.33, 132.19, 144.28;
GC–MS (%) 342 (79), 285 (100), 228 (48). Compound 2d: white solid; mp 214–
216 °C; 1H NMR (300 MHz, CDCl3) d 3.92 (s, 6H, 2OMe), 7.09 (s, 2H, ArH), 7.16
(d, J = 9.0 Hz, 2H, ArH), 7.52 (d, J = 8.4 Hz, 2H, ArH), 7.68 (d, J = 8.4 Hz, 4H, ArH),
7.99 (s, 2H, ArH); 13C NMR (75.5 MHz, CDCl3) d 55.16, 74.25, 82.51, 105.66,
116.46, 119.41, 126.73, 128.12, 128.96, 129.21, 132.55, 134.36, 158.51; GC–MS
(%) 362 (100), 331 (76), 300 (46). Compound 2e:29 white solid, mp 60–62 °C;
1H NMR (300 MHz, CDCl3) d: 1.55–1.67 (m, 8H, 4CH2), 2.11–2.14 (m, 8H, 4CH2),
6.25 (t, J = 4.0 Hz, 2H); 13C NMR (75.5 MHz, CDCl3) d 21.3, 22.1, 25.8, 28.6, 71.5,
82.7, 119.9, 138.0, GC–MS (%): 210 (100) 181 (23), 167 (74), 153 (53), 128 (24),
115 (33), 91 (24), 77 (41). Compound 2f:30 colorless oil; 1H NMR (300 MHz,
CDCl3) d 0.96 (t, J = 7.2 Hz, 6H, 2Me), 1.45–1.59 (m, 4H, 2CH2), 2.20 (t, J = 6.8 Hz,
4H, 2CH2); 13C NMR (75.5 MHz, CDCl3) d 13.22, 20.93, 21.61, 65.14; GC–MS (%)
134 (39), 119 (32), 105 (41), 91 (100), 78 (45), 63 (28). Compound 2g:17
colorless oil; 1H NMR (300 MHz, CDCl3) d 0.92 (t, J = 7.2 Hz, 6H, 2Me), 1.26–
1.58 (m, 8H, 4CH2), 2.27 (t, J = 6.8 Hz, 4H, 2CH2); 13C NMR (75.5 MHz, CDCl3) d
13.29, 18.65, 21.68, 30.15, 65.00, 74.06; GC–MS (%) 162 (37), 147 (3), 133 (2),
119 (16), 91 (100), 78 (48). Compound 2h:29 Colorless oil; 1H NMR (300 MHz,
CDCl3) d 0.89 (t, J = 7.6 Hz, 6H, 2Me); 1.28–1.54 (m, 12H, 6CH2), 2.25 (t,
J = 7.2 Hz, 4H, 2CH2); 13C NMR (75.5 MHz, CDCl3) d 13.91, 19.23, 22.21, 28.04,
31.00, 65.21, 77.5; GC–MS (%) 190 (34), 161 (15), 105 (57), 91(100). Compound
2i:31 white solid; mp 106–108 °C; 1H NMR (300 MHz, CDCl3) d 0.17 (s, 18H,
19. For review: (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; (d)
Petragnani, N.; Stefani, H. A. Tellurium in Organic Chemistry, Second, Updated
and Enlarged Edition; Academic Press/Elsevier, 2007.
20. (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)
Nishibayashi, Y.; Cho, C. -S.; Ohe, K.; Uemura, S. J. Organomet. Chem. 1996, 507,
197; (d) Nishibayashi, Y.; Cho, C.-S.; Ohe, K.; Uemura, S. J. Organomet. Chem.
1996, 526, 335.
6Me); 13C NMR (75.5 MHz, CDCl3)
d
-0.34, 89.99, 93.04. Compound 2j:18
colorless oil; 1H NMR (300 MHz, CDCl3) d 3.40 (s, 6H, 2OMe), 4.17 (s, 4H, 2CH2);
13C NMR (75.5 MHz, CDCl3) d 57.60, 59.90, 70.24, 74.97.
21. (a) Nishibayashi, Y.; Cho, C. S.; Ohe, K.; Uemura, S. J. Organomet. Chem. 1996,
526, 335; (b) Nishibayashi, Y.; Cho, C. S.; Uemura, S. J. Organomet. Chem. 1996,