Copper(I) tert-butoxide-promoted 1,4 Csp2-to-O silyl migration: Stereospecific allylation of (Z)-γ-trimethylsilyl allylic alcohols

Article abstract of DOI:10.1021/ol016837w

Formula presented The cyclic silyl ethers, 2,2-dimethyl-1-oxa-2-sila-3-cyclopentenes, were produced by the treatment of (Z)-γ-trimethylsilyl allylic alcohols with a catalytic or stoichiometric amount of lithium tert-butoxide. On the other hand, successive

Full text of DOI:10.1021/ol016837w

ORGANIC
LETTERS
2001
Vol. 3, No. 23
3811-3814
Copper(I) tert-Butoxide-Promoted 1,4
C -to-O Silyl Migration: Stereospecific
sp2
Allylation of (Z)-γ-Trimethylsilyl Allylic
Alcohols
Haruhiko Taguchi, Kazushi Ghoroku, Makoto Tadaki, Akira Tsubouchi, and
Takeshi Takeda*
Department of Applied Chemistry, Tokyo UniVersity of Agriculture and Technology,
Koganei, Tokyo 184-8588, Japan
takeda-t@cc.tuat.ac.jp
Received October 1, 2001
ABSTRACT
The cyclic silyl ethers, 2,2-dimethyl-1-oxa-2-sila-3-cyclopentenes, were produced by the treatment of (Z)-γ-trimethylsilyl allylic alcohols with a
catalytic or stoichiometric amount of lithium tert-butoxide. On the other hand, successive treatment of the alcohols with copper(I) tert-
butoxide and allylic halides followed by the tetrabutylammmonium fluoride assisted hydrolysis produced the allylation products, 2,5-alkadien-
1-ols, with complete retention of configuration of the double bond.
Transmetalation of organosilicon compound through the
Brook-type rearrangement is an attractive approach to
system and suggested that a formal C-2 carbanion cannot
be formed by the treatment of 2-(tert-butyldimethylsilyl)-3-
(hydroxymethyl)furan with sodium hydride in DMF.2 Kim
and Magriotis reported that the treatment of 1-iodo-3-
(trimethylsilyloxy)-1-propene derivatives with excess tert-
3
produce reactive organometallic species. Although 1,4 Csp -
to-O silyl migrations have been employed for the preparation
2
of various carbanions,1 1,4 Csp -to-O silyl migration has
2
provided so far little synthetic significance. Spinazze´ and
butyllithium affords the 1,4 O-to-Csp silyl migration product
2
Keay studied the 1,4 Csp -to-O silyl migration of a furan
exclusively, indicating that the preparation of vinylmetal
2
species by 1,4 Csp -to-O silyl migration of the lithium salts
(1) (a) Woodbury, R. P.; Rathke, M. W. J. Org. Chem. 1978, 43, 1947-
1949. (b) Matsuda, I.; Murata, S.; Ishii, Y. J. Chem. Soc., Perkin Trans. 1
1979, 26-30. (c) Isobe, M.; Kitamura, M.; Goto, T. Tetrahedron Lett. 1979,
3465-3468. (d) Fleming, I.; Floyd, C. D. J. Chem. Soc., Perkin Trans.
1981, 969-976. (e) Takeda, T.; Naito, S.; Ando, K.; Fujiwara, T. Bull.
Chem. Soc. Jpn. 1983, 56, 967-968. (f) Takeda, T.; Ando, K.; Fujiwara,
T. Chem. Lett. 1983, 1285-1288. (g) Brook, A. G.; Chrusciel, J. J.
Organometallics 1984, 3, 1317-1381. (h) Isobe, M.; Ichikawa, Y.;
Funabashi, Y.; Mio, S.; Goto, T. Tetrahedron 1986, 42, 2863-2872. (i)
Tietze, L. F.; Geissler, H.; Gewert, J. A.; Jakobi, U. Synlett 1994, 511-
512. (j) Jankowski, P.; Raubo, P.; Wicha, J. Synlett 1994, 985-992. (k)
Shinokubo, H.; Miura, K.; Oshima, K.; Utimoto, K. Tetrahedron 1996, 52,
503-514. (l) Smith, A. B., III.; Boldi, A. M. J. Am. Chem. Soc. 1997, 119,
6925-6926. (m) Bra¨uer, N.; Michel, T.; Schaumann, E. Tetrahedron 1998,
54, 11481-11488. (n) Smith, A. B., III; Pitram, S. M. Org. Lett. 1999, 1,
2001-2004. (o) Moser, W. H. Tetrahedron 2001, 57, 2065-2084.
of γ-silyl allylic alcohols 1 is not feasible.3 In contrast to
2
this result, they also found the formation of the 1,4 Csp -
to-O silyl migration product, the trimethylsilyl ether of
cinnamyl alcohol, by the treatment of (Z)-3-phenyl-3-
(trimethylsilyl)-2-propen-1-ol 1d with a catalytic amount of
tert-butyllithium. It is suggested that the intermediate vinyl-
lithium stabilized with the phenyl moiety would be produced
partially in equilibrium, and the protonation of the vinyl-
(2) Spinazze´, P. G.; Keay, B. A. Tetrahedron Lett. 1989, 30, 1765-
1768.
(3) Kim, K. D.; Magriotis, P. A. Tetrahedron Lett. 1990, 31, 6137-
6140.
10.1021/ol016837w CCC: $20.00 © 2001 American Chemical Society
Published on Web 10/24/2001

lithium with the starting alcohol 1d serves to displace the
unfavorable equilibrium to the product formation.4
1e were recovered unchanged when being treated with
lithium tert-butoxide under similar conditions. This observa-
tion agrees with the result of the reaction of the (Z)-4-
(triisopropylsilyl)-4-(trimethylsilyl)-3-propen-2-ol with a cata-
lytic amount of methyllithium reported by Lautens and co-
workers.4
In connection with our continuous study on the preparation
and reaction of group 14 vinylmetals,5 we were intrigued
2
with the 1,4 Csp -to-O silyl migration of conformationally
rigid γ-trimethylsilyl allylic alcohols 1a and 1b.6 Unlike the
reaction of cinnamyl alcohol derivative 1d described above,
the treatment of 1a and 1b with a stoichiometric or catalytic
amount of lithium tert-butoxide at room temperature for 24
h gave the cyclic silyl ethers 1-oxa-2-silacyclopent-3-enes
2a and 2b as sole products (Scheme 1). These results, indeed,
Recently, we found that the vinylsilanes bearing a 2-py-
ridylthio group at the carbon R to the trimethylsilyl group
reacted with allylic halides in the presence of CuI-KF to
produce the cross-coupling products.5e We tentatively assume
that the reaction proceeds via transmetalation of silicon to
copper assisted by the intramolecular coordination of nitrogen
to silicon. Therefore it is anticipated that the hyper-
coordinated silicon compound 4 reacts with electrophiles at
Scheme 1
2
its Csp -carbon via the formation of a Brook-type rearrange-
ment product, the vinylcopper species 5 (Scheme 2). Then
Scheme 2
we investigated the preparation of copper(I) alkoxides of (Z)-
γ-trimethylsilyl allylic alcohols 6 and their reaction with
allylic halides 7.
indicate the formation of intermediary pentavalent silicon
anions 3. Generally the alkenyl group is protonated prefer-
entially to the alkyl group in hypervalent silicon compounds.7
The unusual formation of silacycle 2 would be explained
by the protonolysis of the methyl group trans to the donor
atom in the pentacoordinate system 3.8 The similar activation
As expected, the treatment of the cyclic alcohol 1a with
copper(I) tert-butoxide (1.5 equiv), prepared in situ by the
reaction of copper(I) iodide with lithium tert-butoxide,10 in
2
THF at room temperature predominantly gave the 1,4 Csp -
3
of Csp -Si bond by the intramolecular nucleophilic attack
to-O silyl migration product 8a, and the formation of a small
amount of the cyclic silyl ether 2a was observed (Scheme
3).
at silicon has been studied.9 In marked contrast to the above
results, the conformationally more flexible alcohols 1c and
(4) Lautens, M.; Delanghe, P. H. M.; Goh, J. B.; Zhang, C. H. J. Org.
Chem. 1995, 60, 4213-4227.
Scheme 3
(5) (a) Takeda, T.; Sugi, S.; Nakayama, A.; Suzuki, Y.; Fujiwara, T.
Chem. Lett. 1992, 819-822. (b) Takeda, T.; Kabasawa, Y.; Fujiwara, T.
Tetrahedron 1995, 51, 2515-2524. (c) Takeda, T.; Matsunaga, K.;
Kabasawa, Y.; Fujiwara, T. Chem. Lett. 1995, 771-772. (d) Takeda, T.;
Matsunaga, K.; Uruga, T.; Takakura, M.; Fujiwara, T. Tetrahedron Lett.
1997, 38, 2879-2882. (e) Takeda, T.; Uruga, T.; Gohroku, K.; Fujiwara,
T. Chem. Lett. 1999, 821-822.
(6) The following two methods were employed for the setereoselective
preparation of (Z)-γ-trimethylsilyl allylic alcohols 1. (Z)-â-Trimethylsilyl-
R,â-unsaturated ketones were prepared by the tin(IV) chloride promoted
reaction of R-trimethylsilyl thioacetals with enol trimethylsilyl ethers
followed by the elimination of thiophenol similarly to the synthesis of (Z)-
â-tributylstannyl-R,â-unsaturated ketones.5a,b The reduction of the silyl
ketones with lithium aluminum hydride gave the secondary alcohols 1a-
c. The primary alcohols 1d-f were prepared from acylsilanes. Their
olefination using ethyl trimethylsilyl acetate (for 1d and 1e) or diethyl
ethoxycarbonylmethylphosphonate (for 1f) followed by DIBAH reduction
gave the alcohols 1. Fujiwara, T.; Sawabe, K.; Takeda, T. Tetrahedron 1997,
53, 8349-8370.
The successive treatment of 1a with copper(I) tert-butoxide
(1.5 equiv) and methallyl chloride 7a (1.2 equiv) for 23 h at
room temperature produced the trimethylsilyl ether of dienyl
alcohol 9a in 92% yield. The tetrabutylammmonium fluoride
assisted hydrolysis of 9a afforded the alcohol 10a in 80%
overall yield (Scheme 4).
(7) Cella, J. A.; Cargioli, J. D.; Williams, E. A. J. Organomet. Chem.
1980, 186, 13-17.
(8) Similar reversal of selectivity in cleavage of mixed tetraorganotin
compounds by halogens has been reported: Jousseaume, B.; Villeneuve, P.
J. Chem. Soc., Chem. Commun., 1987, 513-514. Also see ref 5a.
(9) (a) Eaborn, C.; Mahmoud, F. M. S. J. Organomet. Chem. 1981, 209,
13-16. (b) Hudrlik, P. F.; Abdallah, Y. M.; Hudrlik, A. M. Tetrahedron
Lett. 1992, 33, 6743-6746. (c) Hudrlik, P. F.; Abdallah, Y. M.; Hudrlik,
A. M. Tetrahedron Lett. 1992, 33, 6747-6750.
Under similar reaction conditions, the coupling reactions
of several (Z)-γ-trimethylsilyl allylic alcohols 1 including
(10) Tsuda, T.; Hashimoto, T.; Saegusa, T. J. Am. Chem. Soc. 1972, 94,
658-659.
3812
Org. Lett., Vol. 3, No. 23, 2001

Table 1. Stereospecific Allylation Promoted by Copper(I) tert-Butoxide
a A 1.2 equiv portion of copper(I) tert-butoxide was used
Org. Lett., Vol. 3, No. 23, 2001
3813

copper compounds have been suggested to be active species
of these reactions, and indeed, copper(I) acetylides were
isolated as intermediates in a certain case.11g Although
palladium-catalyzed cross-coupling reactions of functional-
ized alkenylsilanes and alkenylsilacyclobutanes with organic
halides are employed for the preparation of various olefinic
compounds,12 the synthetic application of copper(I)-promoted
reactions of alkenylsilanes is generally restricted because the
silanes should have an electronegative ligand such as fluorine
and are only applied to the preparation of symmetrical 1,3-
dienes by homocoupling.11a,d,e
Scheme 4
In summary, we have developed the copper(I) tert-
2
butoxide-promoted 1,4 Csp -to-O silyl migration of (Z)-γ-
trimethylsilyl allylic alcohols. The intermediates of this
migration react with allylic halides to afford the cross-
coupling products, dienyl alcohols, with retention of con-
figuration. It should be noted that this reaction provides a
useful method for the preparation of reactive alkenylmetal
species or their equivalents under mild conditions. Studies
aimed at broadening the scope of this reaction and under-
standing its mechanism are currently in progress.
the conformationally flexible acyclic compounds with allylic
chlorides 7 were performed, and the allylation products 10
were obtained with complete retention of configuration
regardless of their conformational mobility (Table 1). In some
cases, DMF was the solvent of choice (see entries 8, 10,
and 13).
Contrary to the above results, the reaction of (E)-allylic
alcohol 1f with methallyl chloride 7a was found to be messy,
and the formation of the corresponding dienyl alcohol 10i
was not observed (entry 14). This result clearly shows that
the formation of pentavalent silicate by intramolecular
coordination is indispensable for the allylation.
Supporting Information Available: Experimental pro-
cedures and characterization data for compounds 1a-f, 2a,
2b, 9a, and 10a-h. This material is available free of charge
via the Internet at http://pubs.acs.org.
OL016837W
In the past few years, copper(I) salt promoted self- and
cross-coupling reactions of organosilicon compounds have
become a subject of increasing research interest.11 Organo-
Y.; Hirabayashi, K.; Mori, A.; Hiyama, T. Chem. Commun. 1997, 1039-
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Lett. 1997, 639-640. (g) Ito, H.; Arimoto, K.; Sensui, H.; Hosomi, A.
Tetrahedron Lett. 1997, 38, 3977-3980. (h) Nishihara, Y.; Ikegashira, K.;
Mori, A.; Hiyama, T. Tetrahedron Lett. 1998, 39, 4075-4078.
(11) (a) Yosida, J.; Tamao, K.; Kakui, T.; Kumada, M. Tetrahedron Lett.
1979, 1141-1144. (b) Urata, H.; Fuchikami, T. Tetrahedron Lett. 1991,
32, 91-94. (c) Lermontov, S. A.; Rakov, I. M.; Zefirov, N. S. Tetrahedron
Lett. 1996, 37, 4051-4054. (d) Kang, S.-K.; Kim, T.-H.; Pyun, S.-J. J.
Chem. Soc., Perkin Trans. 1 1997, 797-798. (e) Ikegashira, K.; Nishihara,
(12) (a) Hatanaka, Y.; Hiyama, T. Synlett 1991, 845-853. (b) Horn, K.
A. Chem. ReV. 1995, 95, 1317-1350. (c) Suginome, H.; Kinugasa, H.; Ito,
Y. Tetrahedron Lett. 1994, 35, 8635-8638. (d) Denmark, S. E.; Choi, J.
Y. J. Am. Chem. Soc. 1999, 121, 5821-5822. (e) Denmark, S. E.; Yang,
S.-M. Org. Lett. 2001, 3, 1749-1752 and references therein.
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Org. Lett., Vol. 3, No. 23, 2001