Yoshio Nishimura et al.
COMMUNICATIONS
[2] R. Amemiya, M. Yamaguchi, Adv. Synth. Catal. 2007,
349, 1011–1014.
formed. Apparently, 20 and 21 are the products de-
rived from the deprotonation of 15 with GaCl3 to
form disilylated gallium species 17. It is suggested
that GaCl3 is able to deprotonate the allylic position
of allylsilanes.
In summary, GaCl3 deprotonated allylic positions of
cyclopentadienes, silylated 1,4-dienes, and silylated
1,3-diene, and the resulted allylgalliums underwent re-
gioselective ethynylation reactions. A silyl group on
the olefin of 1,4-dienes was suggested to enhance the
acidity of the allylic positions.
[3] Our previous works using GaCl3 and GaR3 as bases;
a) Y. Nishimura, M. Yamaguchi, Chem. Commun. 2008,
35–48; b) Y. Nishimura, Y. Miyake, R. Amemiya, M.
Yamaguchi, Org. Lett. 2006, 8, 5077–5080; c) Y. Nishi-
mura, R. Amemiya, M. Yamaguchi, Tetrahedron Lett.
2006, 47, 1839–1843; d) R. Amemiya, Y. Miyake, M.
Yamaguchi, Tetrahedron Lett. 2006, 47, 1797–1800;
e) R. Amemiya, M. Yamaguchi, Eur. J. Org. Chem.
2005, 5145–5150; f) R. Amemiya, Y. Nishimura, M. Ya-
maguchi, Synthesis 2004, 1307–1314.
[4] a) K. S. Feldman, C. M. Kraebel, M. Parvez, J. Am.
Chem. Soc. 1993, 115, 3846–3847; b) K. S. Feldman,
C. K. Weinreb, W. J. Youngs, J. D. Bradshaw, J. Org.
Chem. 1994, 59, 1213–1215; c) K. S. Feldman, C. K.
Weinreb, W. J. Youngs, J. D. Bradshaw, J. Am. Chem.
Soc. 1994, 116, 9019–9026; d) K. S. Feldman, D. A.
Mareska, C. K. Weinreb, M. Chasmawala, Chem.
Commun. 1996, 865–866.
[5] Synthesized using following methods; a) H. Chen,
M. Z. Deng, J. Organomet. Chem. 2000, 603, 189–193;
b) H. Yasuda, T. Nishi, K. Lee, A. Nakamura, Organo-
metallics 1983, 2, 21–27; see supporting information.
[6] a) M. Schlosser, A. Zellner, F. Leroux, Synlett 2001,
1830–1836; b) H. E. Zimmerman, V. Cirkva, L. Jiang,
Tetrahedron Lett. 2000, 41, 9585–9587; c) Y. Naruta, Y.
Nishigaichi, K. Maruyama, J. Org. Chem. 1991, 56,
2011–2017; d) W. Oppolzer, R. L. Snoeden, Helv.
Chim. Acta 1980, 63, 555–562.
Experimental Section
Ethynylation of1
Under an argon atmosphere, to a mixture of GaCl3 (176 mg,
1.0 mmol), tert-butyldiphenylsilanol (256 mg, 1.0 mmol), and
2.6-di(tert-butyl)-4-methylpyridine (205 mg, 1.0 mmol) in o-
dichlorobenzene were added 1,2,3,4,5-pentamethylcyclopen-
tadiene 1 (68 mg, 0.5 mmol) and chlorotriisopropylsilylacety-
lene 2 (432 mg, 2.0 mmol). The mixture was heated at
1708C, and stirred for 6 h, when water (10 mL) was added.
The organic materials were extracted with ether. The com-
bined organic layers were washed with water, brine, dried
over MgSO4, and concentrated under reduced pressure. The
residue was purified by flash column chromatography
(hexane) giving 3; yield: 126 mg (80%).
[7] P. W. Rabideau, D. L. Huser, J. Org. Chem. 1983, 48,
4266–4271.
[8] H. Yasuda, Y. Ohnuma, M. Yamauchi, H. Tani, A. Na-
kamura, Bull. Chem. Soc. Jpn. 1979, 52, 2036–2045.
[9] a) S. Florio, L. Ronzini, R. Sgarra, Tetrahedron Lett.
1990, 31, 2327–2330; b) H. Yasuda, K. T. Nishi, S.
Miyanaga, A. Nakamura, Organometallics 1985, 4,
359–367; c) H. Yasuda, K. Nagasuna, M. Akita, K.
Lee, A. Nakamura, Organometallics 1984, 3, 1470–
1478; d) H. Yasuda, M. Yamauchi, A. Nakamura, T.
Sei, Y. Kai, N. Yasuoka, N. Kasai, Bull. Chem. Soc.
Jpn. 1980, 53, 1089–1100.
Acknowledgements
The authors thank JSPS for financial support (Nos. 18850004
and 18790004).
References
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1274
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2008, 350, 1271 – 1274