Peterson allenation using (Z)-(1-lithio-1-alkenyl)trimethylsilanes

Article abstract of DOI:10.1055/s-2006-951474

Lithium alkoxides of β-silylallylic alcohols underwent the Peterson elimination in DMF to give allenes. Allenes were also directly obtained by a Peterson allenation reaction from carbonyl compounds using (Z)-(1-lithio-1- alkenyl)trimethylsilanes in one po

Full text of DOI:10.1055/s-2006-951474

LETTER
2577
Peterson Allenation Using (Z)-(1-Lithio-1-alkenyl)trimethylsilanes
A
N
ewPetersonA
k
llenation
R
ea
i
ction ra Tsubouchi, Takashiro Kira, Takeshi Takeda*
Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, Koganei,
Tokyo 184-8588, Japan
Fax +81(42)3887034; E-mail: takeda-t@cc.tuat.ac.jp
Received 5 July 2006
R13Si
R13Si
Abstract: Lithium alkoxides of b-silylallylic alcohols underwent
the Peterson elimination in DMF to give allenes. Allenes were also
directly obtained by a Peterson allenation reaction from carbonyl
compounds using (Z)-(1-lithio-1-alkenyl)trimethylsilanes in one
pot.
MH
R2
R3
R4
R2
R3
R4
M = K, Na
1
6
OH
OM
R3
M+
–
Peterson elimination
R13Si
Key words: alcohols, allenes, carbonyl, elimination, silicon
O
R4
R2
R2
R3
2
– R13SiOM
R4
4
M
The Peterson elimination has been widely used for the
preparation of alkenes from b-hydroxysilanes.1 It has
been shown that the elimination proceeds readily from the
alkoxides of b-hydroxysilanes that have considerable ion-
ic character on the oxygen atom, such as with a sodium or
potassium counterion.2 The alkenes were also obtained in
one pot from carbonyl compounds by condensation with
a-silyl carbanions stabilized by an electron-withdrawing
group at the anionic carbon; the overall transformation is
called the Peterson olefination.
R2
OSiR1
R3
1
3
R2
OSiR1
3
R4
R3 R4
Protodesilylation
5
3
Scheme 1
Peterson elimination along this line and here describe the
first one-pot Peterson allenation.
The (Z)-b-(trimethylsilyl)allylic alcohols 1 were treated
with butyllithium (1.2 equiv) in ether at 0 °C to form the
alkoxides 6, which were then treated with DMF and
warmed to 50 °C to produce the allenes 2 in good yields
(Scheme 2, Table 1).8 It is noteworthy that better yields of
2 were obtained when ether rather than THF was used for
the preparation of 6 (Table 1, entry 2) and that HMPA was
also effective for the elimination (Table 1, entry 3).
If the Peterson elimination is applied to b-silylallylic alco-
hols 1, allenes 2 should be obtained. In this regard, several
researchers investigated sodium or potassium hydride-
mediated Peterson elimination of 1 in THF or HMPA
solutions (Scheme 1). However, allyl silyl ethers 3 were
produced as the sole products via a 1,3 C(sp2)-to-O silyl
migration in these cases.3,4 Tius et al. observed the forma-
tion of 1-(4-methoxyphenyl)-1,2-nonadiene from the
corresponding b-(triethylsilyl)allylic alcohol by treatment
with potassium hydride in THF in low yield (10%) with
the allyl silyl ether 3 as a predominant product.5 These
results suggest to us that intermediates proposed for the
Peterson elimination (cyclic silicates 4, or vinyl anion
species 5 generated by the 1,3-silyl migration of 4) may be
rapidly protonated with the as yet unreacted alcohol 1,
leading to allyl silyl ethers in preference to the elimination
product.
SiMe3
BuLi
R1
R2
R3
2
1
Et2O
DMF
OLi
6
Scheme 2
The conventional transformation of silyl alcohols 1 into
allenes 2 requires a two-step procedure. The alcohols 1 are
first transformed into chlorides, acetates, or trifluoroace-
tates, which are then treated with fluoride ion to give al-
lenes.5,6,9 Compared with these two-step procedures, our
method enjoys an advantage that it does not require an ex-
tra transformation.
We expected that this problem would be circumvented
based on the following thesis: after the complete forma-
tion of the lithium alkoxides 6, inactive for the Peterson
elimination in a low polar solvent due to the covalent
character of the Li–O bond,6 the elimination would be
initiated by increase in the solvent polarity by addition of
an aprotic polar solvent.7 We have thus studied the
The present method was successfully extended to a direct
transformation of carbonyl compounds 7 to allenes 2
utilizing
(Z)-(1-lithio-1-alkenyl)trimethylsilanes
8
(Scheme 3).10 The halogen–lithium exchange reaction of
(1-halo-1-alkenyl)silanes with tert-butyllithium in ether at
–78 °C was used to generate the corresponding organo-
lithium species (1.5 equiv) which were allowed to react
with ketones or aldehydes 7 to provide the lithium
SYNLETT 2006, No. 16, pp 2577–2580
0
4
.1
0
.2
0
0
6
Advanced online publication: 22.09.2006
DOI: 10.1055/s-2006-951474; Art ID: U08206ST
© Georg Thieme Verlag Stuttgart · New York

2578
LETTER
Table 1 Formation of Allenes 2 from (Z)-b-Silylallylic Alcohols 1
In conclusion, we have developed the Peterson allenation
using (Z)-(1-lithio-1-alkenyl)trimethylsilanes. Its success
results from the appropriate choice of the metal cation of
the alkoxides and the control of solvent polarity. Further
study on the synthetic application of this new carbonyl al-
lenation is currently underway.
Entry Silyl alcohol 1
Time (h)a Product (yield %)
3
SiMe3
Ph
Hex
Hex
Ph
1
2a (86)
OH
1a
1a
2b
3d
2
3
3
2a (46)c
2a (73)
Acknowledgment
1a
This work was carried out under the 21st Century COE program of
‘Future Nano-Materials’ in Tokyo University of Agriculture &
Technology.
Ph
SiMe3
Hex
Hex
4
5
Ph
2b (87)
OH
References and Notes
1b
(1) (a) Ager, D. J. Org. React. 1990, 38, 1. (b) Kano, N.;
Kawashima, T. In Modern Carbonyl Olefination; Takeda,
T., Ed.; Wiley-VCH: Weinheim, 2004, 18.
3
3
2
SiMe3
Ph
Ph
OH
(2) Hudrlik, P. F.; Peterson, D. J. Am. Chem. Soc. 1975, 97,
1464.
Ph
Ph
2c (83)
1c
(3) Sato, F.; Tanaka, Y.; Sato, M. J. Chem. Soc., Chem.
Commun. 1983, 165.
Ph
Ph
Me3Si
Ph
Ph
(4) Wilson, S. R.; Georgiadis, G. M. J. Org. Chem. 1983, 48,
4143.
6
7
Ph
Ph
OH
OH
2d (90)
(5) (a) Tius, M. A.; Pal, S. K. Tetrahedron Lett. 2001, 42, 2605.
(b) The transformation of disilanyl propargyl ethers to
silylallenes, which is suggested to involve the Peterson
elimination of lithium b-silylallylic alkoxides, has been
reported: Suginome, M.; Matsumoto, A.; Ito, Y. J. Org.
Chem. 1996, 61, 4884. (c) The preparation of D4-(4H-
pyranyl)[3]cumulenes by reaction of aromatic aldehydes and
ketones with lithiated acetylenic pyranes has been reported:
Doney, J. J.; Chen, C. H. Synthesis 1983, 491.
1d
Me3Si
Ph
Ph
2e (77)
1e
a Reaction time after addition of DMF.
b Treated with BuLi at –78 °C in THF for 1 h.
c The silyl ether 3 was also obtained (25%).
d HMPA was used as a co-solvent.
(6) The lithium alkoxides of (Z)-b-silylallylic alcohols 6 can be
prepared in ether, see: Chan, T. H.; Mychajlowskij, W.; Ong,
B. S.; Harpp, D. N. J. Org. Chem. 1978, 43, 1526.
(7) For the effect of solvent polarity on silyl migration, see:
Shinokubo, H.; Miura, K.; Oshima, K.; Utimoto, K.
Tetrahedron 1996, 52, 503.
alkoxides 6 in situ. DMF was then added to the solutions
of 6 at 0 °C and the mixtures were warmed to 50 °C. The
various allenes 2 were obtained in good to high yields
when using (1-bromo-1-alkenyl)silanes 911 as precursors
of 86 (Table 2). Whereas, the similar reaction using the
corresponding iodides 1012 resulted in the formation of 2
in poor yields.13 In some cases a higher reaction tempera-
ture (80 °C) was required to attain satisfactory yields.
(8) Typical Procedure for the Preparation of Allenes 2 from
(Z)-b-Silylallylic Alcohols 1: n-BuLi (1.6 M in hexane, 0.23
mL, 0.37 mmol) was added dropwise to an Et2O solution
(0.9 mL) of 1d (97 mg, 0.30 mmol) at 0 °C under argon.
After 15 min, DMF (4.2 mL) was added in one portion, and
the mixture was warmed to 50 °C and stirred for 3 h. The
reaction was quenched by addition of H2O and the products
were extracted into Et2O. The organic layer was washed with
H2O and dried (Na2SO4). The solvent was concentrated
under reduced pressure and the crude product was purified
by PTLC (hexane–EtOAc, 98:2) to give 2d (63 mg, 90%).
IR (neat): 3061, 3027, 2921, 2852, 1955, 1602, 1496, 1453,
847, 750, 698 cm–1; 1H NMR (300 MHz, CDCl3): d = 2.68–
2.85 (m, 5 H), 4.66 (d, J = 7.1 Hz, 2 H), 5.07–5.15 (m, 1 H),
7.20–7.38 (m, 10 H); 13C NMR (75 MHz, CDCl3): d = 40.9,
41.8, 75.8, 93.1, 125.9, 128.1, 129.2, 140.4, 207.9; Anal.
Calcd for C18H18: C, 92.26; H, 7.74. Found: C, 92.06; H,
8.02.
The vinylallenes 2m and 2n were produced by reaction of
a,b-unsaturated carbonyl compounds 7g and 7h with 9b
(Table 2, entries 11 and 12). Since little is known about
the preparation of vinylallenes by carbonyl olefination,14
the present reaction provides a useful method for the
synthesis of vinylallenes.
O
7
(9) (a) Bratovanov, S.; Bienz, S. Main Group Met. Chem. 1996,
19, 769. (b) Torres, E.; Larson, G. L.; McGarvey, G. J.
Tetrahedron Lett. 1988, 29, 1355. (c) Larson, G. L.; Torres,
E.; Morales, C. B.; McGarvey, G. J. Organometallics 1986,
5, 2274.
SiMe3
SiMe3
tBuLi
Et2O
R2
R3
6
2
R1
R1
DMF
X
Li
8
9
(X = Br)
10 (X = I)
(10) Typical Procedure for the Allenation of Carbonyl
Compounds 7: A solution of 9c (115 mg, 0.45 mmol) in
Et2O (0.6 mL) was placed in a flask under argon and t-BuLi
(1.5 M in pentane, 0.35 mL, 0.53 mmol) was added dropwise
Scheme 3
Synlett 2006, No. 16, 2577–2580 © Thieme Stuttgart · New York

LETTER
A New Peterson Allenation Reaction
2579
Table 2 Formation of Allenes 2 by Carbonyl Allenation
Entry
Vinyl bromide 9
Carbonyl compound 7
Temp (°C)
Product
2e
Yield (%)
SiMe3
O
1
2
50
80
62
73
Br
Ph
Ph
9a
9a
7a
7a
2e
Ph
Ph
SiMe3
Br
Ph
Ph
3
7a
80
88
9b
Ph
2f
O
Ph
4
5
9b
50
50
77
91
7b
Ph
2g
Ph
SiMe3
Br
7a
Ph
Ph
Ph
9c
2h
Me
O
6
7
9c
50
50
64
49
Ph
Ph
Ph
Me
7c
2i
SiMe3
Br
O
2a
Hex
Ph
H
9d
7d
O
Ph
Ph
H
8
9b
80
74
Ph
Ph
Ph
2j
7e
Ph
O
9
9b
9c
80
50
64
74
Ph
H
Ph
7f
2k
Ph
Ph
10
7e
Ph
2l
O
11
12
9b
9b
50
50
84
48
7g
Ph
2m
O
H
Ph
7h
2n
Synlett 2006, No. 16, 2577–2580 © Thieme Stuttgart · New York

2580
LETTER
(11) (1-Bromo-1-alkenyl)silanes 9 were prepared from
at –78 °C. After stirring for 2 h at –78 °C, a solution of 7a
(72 mg, 0.30 mmol) in Et2O (0.3 mL) was added dropwise.
The mixture was slowly warmed to 0 °C and DMF (4.2 mL)
was added in one portion. The mixture was heated at 50 °C
for 2 h, and the reaction was quenched by addition of H2O.
The usual work-up and purification gave 2h (89 mg, 91%).
IR (neat): 3061, 3027, 2921, 1947, 1601, 1496, 1453, 745,
694 cm–1; 1H NMR (300 MHz, CDCl3): d = 2.35–2.54 (m, 4
H), 2.73–2.88 (m, 4 H), 6.18 (quin, J = 3.0 Hz, 1 H), 7.11–
7.30 (m, 15 H); 13C NMR (75 MHz, CDCl3): d = 33.9, 34.6,
96.5, 107.5, 125.8, 126.48, 126.53, 128.3, 128.40, 128.44,
135.5, 141.9, 202.4; Anal. Calcd for C25H24: C, 92.54; H,
7.46. Found: C, 92.28; H, 7.59.
alkynylsilanes by hydroalumination followed by treatment
with bromine, see: Zweifel, G.; Lewis, W. J. Org. Chem.
1978, 43, 2739.
(12) Zweifel, G.; Murray, R. E.; On, H. P. J. Org. Chem. 1981,
46, 1292.
(13) A similar reaction of 3-phenylpropanal with 1-lithio-1-
(trimethylsilyl)-1-octene, prepared from the corresponding
iodide 10d by treatment with tert-butyllithium,9a gave 2a in
8% yield and the protodesilylation product, 1-phenyl-4-
undecen-3-ol, was isolated in 66% yield. The Peterson
elimination of 1a in the presence of lithium iodide gave 2a
in only 18% yield. Decrease of the yield might, therefore, be
attributable to iodide ion generated by the lithium–halogen
exchange.
(14) Shono, T.; Itoh, K.; Tsubouchi, A.; Takeda, T. Org. Biomol.
Chem. 2005, 3, 2914.
Synlett 2006, No. 16, 2577–2580 © Thieme Stuttgart · New York