Preparation and reaction of 2-aryl-3-silyl-1,3-butadiene

Article abstract of DOI:10.1021/ol051557s

(Chemical Equation Presented) A conjugated π-electron compound, 2-aryl-3-silyl-1,3-butadiene, was easily prepared from 1-benzyloxy-3-silyl-2- propyne, bis(iodozincio)methane, and an aryl halide in the presence of nickel catalyst. A subsequent cross-coupling reaction of the product with another aryl halide gave an unsymmetrical 2,3-diaryl-1,3-butadiene efficiently.

Full text of DOI:10.1021/ol051557s

ORGANIC
LETTERS
2005
Vol. 7, No. 22
4859-4861
Preparation and Reaction of
2-Aryl-3-silyl-1,3-butadiene
Zenichi Ikeda, Koichiro Oshima, and Seijiro Matsubara*
Department of Material Chemistry, Graduate School of Engineering, Kyoto UniVersity,
Kyoutodaigaku-katsura, Nishikyo, Kyoto 615-8510, Japan
matsubar@orgrxn.mbox.media.kyoto-u.ac.jp
Received July 2, 2005
ABSTRACT
A conjugated
π-electron compound, 2-aryl-3-silyl-1,3-butadiene, was easily prepared from 1-benzyloxy-3-silyl-2-propyne, bis(iodozincio)methane,
and an aryl halide in the presence of nickel catalyst. A subsequent cross-coupling reaction of the product with another aryl halide gave an
unsymmetrical 2,3-diaryl-1,3-butadiene efficiently.
Conjugated π-electron compounds such as aryl-substituted
polyenes attract a lot of attention from material scientists.1
The most common and effective strategy to construct the
aryl-substituted polyene skeleton has been stepwise as-
sembling of alkene and arene units by means of cross-
coupling reaction.2 One drawback of the methodology is that
some undesirable π-bond isomerization, including poly-
merization, may occur under the cross-coupling reaction
conditions. To prevent such isomerization, reseachers have
tuned and modifed the organometallic compound that is one
of the cross-coupling partners. For example, Denmark
reported recently an efficient coupling of unsymmetrical 1,4-
bissilyl-1,3-butadiene with an aryl halide to construct 1-silyl-
4-aryl-1,3-butadiene. The compound can be transformed into
an unsymmetrical 1,4-diaryl-1,3-butadiene or the conjugated
polyenes through further cross-coupling reaction.3 Hiyama
showed an efficient preparation of 2,3-bisboryl-1,3-butadiene,
which is a potent precursor for 2,3-diaryl-1,3-butadiene or
dendralene.4,5 In these methods, bissilylated or -borated 1,3-
butadiene is the key intermediate, on which selective cross-
coupling in the right sequence was performed. Several
examples that are based on carbometalation have also been
reported.2b,6 In these methods, an intermediate that is formed
by transition metal catalyzed carbometalation between alkyne
and aryl halide undergoes an additional cross-coupling
reaction or Heck reaction. We have reported a series of
synthetic studies of bis(iodozincio)methane.7 This gem-dizinc
reagent is prepared from diiodomethane, zinc, and a catalytic
amount of lead(II) chloride as reported previously.8 If an
intermediate 2 via a carbometalation of aryl halide to
Scheme 1
propargyl derivative 1 (Scheme 1) undergoes a cross-coup-
ling reaction with bis(iodozincio)methane, the obtained
(5) Hopf, H. Angew. Chem., Int. Ed. 2001, 40, 705.
(1) Conjugated Polymers and Related Materials; Salaneck, W. R.,
Lundstro¨m, I., Rånby, B., Eds.; Oxford University Press: Oxford, 1993.
(2) (a) Babudri, F.; Farinola, G. M.; Fiandanese, V.; Mazzone, L.; Naso,
F. Tetrahedron 1998, 54, 1085-1094. (b) Shibata, K.; Satoh, T.; Miura,
M. Org. Lett. 2005, 7, 1781. (c) Itami K, Mineno M, Muraoka N, Yoshida
J. J. Am. Chem. Soc. 2004, 126, 11778.
(6) (a) Zhou, C.; Emrich, D. E.; Larock, R. C. Org. Lett. 2003, 5, 1579.
(b) Zhang, X.; Larock, R. C. Org. Lett. 2003, 5, 2993. (c) Thadani, A. N.;
Rawal, V. H. Org. Lett. 2002, 4, 4317. (d) Pal, M.; Parasuraman, K.;
Subramanian, V.; Dakarapu, R.; Yeleswarapu, K. R. Tetrahedron Lett. 2004,
45, 2305. (e) Pottier, L. R.; Peyrat, J.-F.; Alami, M.; Brion, J.-D. Synlett
2004, 1503.
(3) Denmark, D. E.; Tymonko, S. A. J. Am. Chem. Soc. 2005, 127, 8004.
(4) (a) Shimizu, M.; Tanaka, K.; Kutrahashi, T. Shimono, K.; Hiyama,
T. Chem. Lett. 2004, 33, 1066. (b) Shimizu, M.; Kurahashi, T.; Hiyama, T.
Synlett 2001, 1006.
(7) (a) Matsubara, S.; Oshima, K. Proc. Jpn. Acad. 2003, 79, 71. (b)
Matsubara, S.; Oshima, K. In Modern Carbonyl Olefination; Takeda, T.,
Ed.; Wiley-VCH: Weinheim, 2004; p 200. (c) Hirayama, T.; Oshima, K.;
Matsubara, S. Angew. Chem., Int. Ed. 2005, 44, 3293.
10.1021/ol051557s CCC: $30.25
© 2005 American Chemical Society
Published on Web 09/24/2005

allylzinc derivative 3 will be transformed into a 1,3-butadiene
derivative 4 via elimination of zinc alkoxide. Accoding to
this method, 2-aryl-3-silyl-1,3-butadiene, which is a conve-
nient precursor for unsymmetrical 2,3-diaryl-1,3-butadiene,
can be prepared in one step. Treatment of 3-trimethylsilyl-
1-bezyloxy-2-propyne (1a) with bis(iodozincio)methane and
iodobenzene in the presence of some palladium catalyst that
was prepared from Pd2dba3‚CHCl3 and PAr3 (Ar ) phenyl,
p-tolyl, 2-furyl, 3,5-bis(trifluoromethyl)phenyl) resulted in
quantitative recovery of alkyne 1a.9 As shown in Scheme 2,
ordinated silyl group, which is the key intermediate for the
cross-coupling.10 Trost demonstrated that the benzyldimeth-
ylsilyl group benefits the cross-coupling reaction, as it is
easily transformed into the fluorodimethylsilyl group, which
is the important hypercoordinated silyl group precursor.11
We had also reported that the (2,6-dimethoxyphenyl)-
dimethylsilyl group can be transformed into the fluorodi-
methylsilyl group with BF3-acetic acid complex.12 As shown
in Scheme 4, the propyne derivatives with these silyl groups
Scheme 4
Scheme 2
however, use of Ni(II) catalyst gave the desired 2-aryl-3-
silyl-1,3-butadiene 6a. Optimization of the yield of 6a by
tuning the nickel(II) catalyst was examined, as shown in
Scheme 2. The catalyst prepared from 2 mol % of Ni(cod)2
and 3 mol % of P(2-furyl)3 improved the yield of 6a to 99%.
Using the nickel catalyst, we examined the reaction of 1a
with bis(iodozincio)methane (5) and various aryl iodides, as
shown in Scheme 3. It is notable that the reaction of 4-bromo-
(1b-d) were examined for the reaction. In each case, the
2-phenyl-3-silyl-1,3-butadiene 7b-c was obtained in good
yield.13
As shown in Scheme 5, 2,3-diaryl-1,3-butadiene was
prepared using 7d. A transformation of 7d into fluorosilane
derivative 8,12 followed by cross-coupling reaction with
4-iodotoluene, gave the 2,3-diaryl-1,3-butadiene 9.
Scheme 5
Scheme 3
This sequential carbometalation and cross-coupling method
can be also applied to diiodoarene. The method will give an
arene with two silylbutadienyl groups. Diiodo arenes 10a-c
were treated with 1a and bis(iodozincio)methane (5) in the
presence of nickel catalyst to give the highly conjugated
π-electron compounds 11a-c in good yields (Scheme 6).
We propose in Scheme 1 that a mechanism of these
transformations may be initiated by carbonickelation of
arylnickel iodide, which is formed by oxidative insertion of
low-valent nickel to aryl iodide. Two other routes are possible
for the formation of 2-aryl-3-silyl-1,3-butadiene. One con-
1-iodobenzene gave the 4-bromophenyl substituted butadiene
6e in excellent yield. The product may be a substrate for
another cross-coupling reaction as aryl bromide.
The trimethylsilyl group is not an attractive group as an
organometallic reagent for the Hiyama coupling reaction. The
various organosilyl compounds, instead of the trimethylsilyl
group, have often been used in attempts to form a hyperco-
(10) Hiyama, T.; Hatanaka, Y. Pure Appl. Chem. 1994, 66, 1471.
(11) Trost, B. M.; Machacek, M. R.; Ball, Z. Org. Lett. 2003, 5, 1895.
(12) Utimoto, K.; Otake, Y.; Yoshino, H.; Kuwahara, E.; Oshima, K.;
Matsubara, S. Bull. Chem. Soc. Jpn 2001, 74, 753.
(8) Matsubara, S.; Oshima, K.; Matsuoka, H.; Matsumoto, K.; Ishikawa,
K.; Matsubara, E. Chem. Lett. 2005, 34, 952.
(9) Matsubara, S.; Ukai, K.; Toda, N.; Utimoto, K.; Oshima, K. Synlett
2000, 995.
(13) Takahashi, T.; Xi, Z.; Fischer, R.; Huo. S.; Xi, C.; Nakajima, K. J.
Am. Chem. Soc. 1997, 119, 4561.
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Org. Lett., Vol. 7, No. 22, 2005

Scheme 6
Scheme 7
the reaction between propargylic bromide and bis(iodozin-
cio)methane (5) in the presence of palladium catalyst, which
affords butadienyl zinc species in situ.9 In the present case,
however, treatment of 1a with bis(iodozincio)methane (5)
in the presence of nickel catalyst prepared from Ni(cod)2
and (2-furyl)3P resulted in the quantitative recovery of 1a.
For these reasons, we prefer Scheme 1. Even in this case,
the carbometalation of arylnickel iodide to propargylic ether
1 occurs under equilibrium and transmetalation of the alkenyl
nickel species 2 with bis(iodozincio)methane should be the
crucial reaction for these transformations.17
Acknowledgment. This work was supported financially
by the Japanese Ministry of Education, Science, Sports, and
Culture. Financial support from Chugai Pharmaceutical Co.,
Ltd. and Takahashi Industrial and Economical Research
Foundation are also acknowledged.
tains an iodozinciomethylzincation as the first step (eq 1 in
Scheme 7), and the other is formation of allenylzinc 14 as
an intermediate by nickel-catalyzed SN2′ reaction (eq 2 in
Scheme 7). In some cases, nickel-catalyzed carbozincation
is a reasonable route, as reported previously.14-16 A route
similar to that in eq 2 was shown in our previous report about
Supporting Information Available: Experimental details
and spectral data. This material is available free of charge
via the Internet at http://pubs.acs.org.
(14) Negishi E.; Miller, J. A. J. Am. Chem. Soc. 1983, 105, 6761.
(15) Stu¨demann, T.; Ibrahim-Ouali, M.; Knochel, P. Tetrahedron Lett.
1998, 54, 1299.
OL051557S
(16) Kimura, M.; Ezoe, A.; Mori, M.; Tamaru, Y. J. Am. Chem. Soc.
2005, 127, 201.
(17) Nakao, Y.; Oda, S.; Hiyama, T. J. Am. Chem. Soc. 2005, 127, 13904.
Org. Lett., Vol. 7, No. 22, 2005
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