The reaction of butatrienolates with aldehydes for the syntheses of α-vinylidene acylsilanes

Article abstract of DOI:10.1246/bcsj.77.1937

Lithium butatrienolates were prepared in situ by the 1,4-elimination from 2-butynyl trimethylsilyl ethers along with a retro-Brook rearrangement. The addition reaction of the enolates with the aldehydes afforded β-hydroxy-α-vinyl-idene acylsilanes.

Full text of DOI:10.1246/bcsj.77.1937

Short Articles
Bull. Chem. Soc. Jpn., 77, 1937–1938 (2004) 1937
O
OH
R'
R'
The Reaction of Butatrienolates
with Aldehydes for the Syntheses
of ꢀ-Vinylidene Acylsilanes
n-BuLi
R'
R'
R3SiO
R3SiO
TMSOTf
Et3N
OTMS
R'
R3SiO
R'
CH2Cl2, 0 °C
ꢀ
Arai, Kyoji Tsuchikama, and Shunsuke Maekawa
1a-c
Takanori Shibata, Kyoko Takami, Yoshikazu
Scheme 2.
silyl-protection of the obtained alcohols (Scheme 2).
Department of Chemistry, School of Science and
Engineering, Waseda University, Shinjuku-ku,
Tokyo 169-8555
When the reaction of the t-butyldimethylsilyl-protected
ether 1a with benzaldehyde was examined, the corresponding
ꢀ-hydroxy-ꢁ-vinylidene acylsilane 2a was obtained in moder-
ate yield along with the formation of several unidentified prod-
ucts derived from 1a. The t-butyldiphenylsilyl ether 1b gave
the better result, a 72% yield. The more bulky silyl group prob-
ably stabilized the lithium salt. Actually, at the higher reaction
temperature (ꢁ20 ꢂC), the butatrienolate decomposed to give a
complex mixture.
Received May 18, 2004; E-mail: tshibata@waseda.jp
Lithium butatrienolates were prepared in situ by the
1,4-elimination from 2-butynyl trimethylsilyl ethers along
with a retro-Brook rearrangement. The addition reaction of
the enolates with the aldehydes afforded ꢀ-hydroxy-ꢁ-vinyl-
idene acylsilanes.
OH
2 equiv
n-BuLi
OTMS
Ph
R3Si
PhCHO
•
THF, -40 °C
R3SiO
O
1a (SiR3= Sit-BuMe )
1b (SiR3= Sit-BuPh22)
2a 46%
2b 72%
The aldol addition of enolates with aldehydes is one of the
most important carbon–carbon forming reactions. In particular,
the addition of ꢁ-silyl-substituted enolates gives acylsilanes,1
which are useful synthetic intermediates for various transfor-
mations.2 When ꢁ-silyl-substituted allenolates (propadieno-
lates), which were prepared by the retro-Brook rearrangement
of allenyllithiums, were used, the reaction with aldehydes gave
ꢁ-methylene acylsilanes.3,4 Here we disclose that the addition
reaction of ꢁ-silyl-substituted butatrienolates with aldehydes
affords ꢁ-vinylidene acylsilanes.
ð1Þ
The reaction of aldehydes with two butatrienolates was ex-
amined (Table 1). Alkyl and ꢁ,ꢀ-unsaturated aldehydes were
also substrates and the corresponding ꢀ-hydroxy-ꢁ-vinylidene
acylsilanes 2c, d were obtained in good yields (Entries 1, 2).
Only a trace amount of the 1,4-adduct was obtained in Entry
2. The dimethyl-substituted butatrienolate prepared from 1c
also reacted with aldehydes to give ꢁ-vinylidene acylsilanes
2e–g in acceptable yields (Entries 3–5).
The unique reactivity of the cumulated carbon–carbon dou-
ble bond is anticipated, which could not be realized in simple
alkenes or conjugate systems. Recently, allenes (propadienes)
were comprehensively studied as unique reagents for transition
metal-catalyzed reactions, however, the synthetic use of the
butatriene component is limited.7 This paper discloses that
the aldol reaction of lithium butatrienolate with aldehydes
proceeded, and that ꢀ-hydroxy-ꢁ-vinylidene acylsilanes were
obtained.
The 1,4-elimination of trimethylsilanol from 1,4-disiloxy-2-
butyne using 2 equivalent amounts of base gives the lithiated
butatriene A.5 C-lithium A is known to exist in equilibrium
with O-lithium B through a (retro-)Brook rearrangement.6
We subjected the in situ prepared lithium butatrienolates to a
reaction with aldehydes (Scheme 1).
1,4-Disiloxy-2-butynes 1a–c, the precursors for butatrieno-
lates, were readily available from the addition of the lithium
salt of 1-siloxy-2-propyne to ketones along with the trimethyl-
Experimental
2 equiv
n-BuLi
General. 1H NMR spectra were measured with a JNM AL-
400 spectrometer and 13C NMR spectra were measured with a
JEOL Lambda 500 spectrometer using tetramethylsilane as an in-
ternal standard and CDCl3 as a solvent. IR spectra were recorded
with a Horiba FT730 spectrophotometer. High-resolution mass
spectral analyses (FAB) were performed on a JEOL JMS-
SX102A. All reactions were examined using an Ar balloon.
1-[3-(t-Butyldimethylsiloxy)prop-1-ynyl]-1-trimethylsiloxy-
cyclohexane (1a). Pale yellow oil. 1H NMR ꢂ 0.09 (s, 6H), 0.15
(s, 9H), 0.88 (s, 9H), 1.19–1.22 (m, 1H), 1.40–1.64 (m, 7H), 1.78–
1.81 (m, 2H), 4.33 (s, 2H); 13C NMR ꢂ ꢁ5:1, 2.1, 18.3, 23.1, 25.3,
25.8, 41.1, 51.8, 69.9, 83.6, 88.6; IR (neat) 1094 cmꢁ1; HRMS
m=z calcd for C18H35O2Si2 (Mþ ꢁ 1): 339.2176. Found:
339.2151.
OTMS
R'
R'
- TMSOH
R3SiO
LiO
R'
R'
Li
R3SiO
R'
R'
•
•
•
•
R3Si
A
B
OH
R"
R'
R'
H3O+
R"CHO
•
R3Si
O
Scheme 1.
Published on the web October 9, 2004; DOI 10.1246/bcsj.77.1937

1938 Bull. Chem. Soc. Jpn., 77, No. 10 (2004)
Ó 2004 The Chemical Society of Japan
Table 1. The Reaction of in Situ Prepared Lithium Butatrie-
nolates with Aldehydes
127.7, 128.3, 129.3, 129.4, 133.3, 133.4, 135.7, 209.0, 233.9; IR
(neat) 3444, 1941, 1577 cmꢁ1; HRMS m=z calcd for C29H39O2Si
(Mþ þ 1): 447.2719. Found: 447.2711.
1-(t-Butyldiphenylsilyl)-2-(cyclohexylidenemethylene)-3-hy-
1
droxyhex-4-en-1-one (2d). Yellow oil. H NMR ꢂ 1.01 (s, 9H),
1.03–1.06 (m, 2H), 1.19–1.25 (m, 4H), 1.40–1.42 (m, 3H), 1.49–
1.52 (m, 1H), 1.69 (d, J ¼ 6:4 Hz, 3H), 3.38 (d, J ¼ 5:5 Hz, 1H),
5.00 (dd, J ¼ 5:5, 5.5 Hz, 1H), 5.49 (dd, J ¼ 5:5, 15.2 Hz, 1H),
5.65–5.73 (m, 1H), 7.30–7.70 (m, 10H); 13C NMR ꢂ 17.7, 18.7,
25.3, 26.3, 26.3, 26.9, 29.0, 29.0, 70.2, 110.6, 115.3, 126.9,
127.7, 127.7, 129.4, 129.4, 131.2, 133.3, 133.3, 135.7, 135.8,
209.4, 233.4; IR (neat) 3451, 1942, 1577 cmꢁ1; HRMS m=z calcd
for C29H36O2Si (Mþ): 444.2485. Found: 444.2483.
Entry
1
R00
Yield/%
1
2
3
4
5
1b
1b
1c
1c
1c
n-Pr
CH3CH=CH
Ph
n-Pr
CH3CH=CH
71 (2c)
85 (2d)
72 (2e)
65 (2f)
60 (2g)
1-(t-Butyldiphenylsilyl)-3-hydroxy-2-(isopropylidenemethyl-
ene)-3-phenylpropan-1-one (2e). Yellow oil. 1H NMR ꢂ 0.70 (s,
3H), 0.77 (s, 3H), 0.98 (s, 9H), 3.64 (d, J ¼ 5:8 Hz, 1H), 5.61 (d,
J ¼ 5:8 Hz, 1H), 7.22–7.60 (m, 15H); 13C NMR ꢂ 17.8, 18.0,
18.6, 26.8, 71.9, 105.1, 116.4, 126.1, 127.2, 127.7, 127.7, 127.9,
128.4, 129.4, 133.0, 133.0, 135.6, 135.6, 142.3, 212.8, 233.4; IR
(neat) 3515, 1954, 1593 cmꢁ1; HRMS m=z calcd for C29H33O2Si
(Mþ þ 1): 441.2250. Found: 441.2217.
1-[3-(t-Butyldiphenylsiloxy)prop-1-ynyl]-1-trimethylsiloxy-
cyclohexane (1b). Pale yellow oil. 1H NMR ꢂ 0.18 (s, 9H), 1.05
(s, 9H), 1.19–1.25 (m, 2H), 1.44–1.60 (m, 6H), 1.79–1.82 (m, 2H),
4.37 (s, 2H), 7.37–7.76 (m, 10H); 13C NMR ꢂ 2.2, 19.3, 23.2, 25.4,
26.7, 41.2, 52.8, 70.0, 83.4, 88.7, 127.6, 129.6, 133.0, 135.4; IR
(neat) 1097 cmꢁ1; HRMS m=z calcd for C28H39O2Si2 (Mþ
ꢁ
1): 463.2489. Found: 463.2446.
1-(t-Butyldiphenylsiloxy)-4-methyl-4-trimethylsiloxypent-2-
1-(t-Butyldiphenylsilyl)-3-hydroxy-2-(isopropylidenemethyl-
1
ene)hexan-1-one (2f). Yellow oil. H NMR ꢂ 0.82 (s, 3H), 0.86
1
yne (1c). Pale yellow oil. H NMR ꢂ 0.17 (s, 9H), 1.05 (s, 9H),
(s, 3H), 0.90 (t, J ¼ 7:2 Hz, 3H), 1.01 (s, 9H), 1.25–1.65 (m, 4H),
3.08 (d, J ¼ 5:8 Hz, 1H), 4.49 (dt, J ¼ 5:8, 5.8 Hz, 1H), 7.33–7.66
(m, 10H); 13C NMR ꢂ 14.0, 18.1, 18.2, 18.7, 18.9, 26.8, 37.4, 68.9,
104.5, 115.8, 127.7, 127.7, 129.4, 129.4, 133.1, 133.2, 135.6,
212.2, 234.0; IR (neat) 3451, 1947, 1585 cmꢁ1; HRMS m=z calcd
for C26H35O2Si (Mþ þ 1): 407.2406. Found: 407.2409.
1.43 (s, 6H), 4.34 (s, 2H), 7.37–7.72 (m, 10H); 13C NMR ꢂ 1.9,
19.2, 26.7, 32.8, 52.7, 66.5, 81.1, 90.0, 127.7, 129.7, 133.2,
135.6; IR (neat) 1113 cmꢁ1; HRMS m=z calcd for C25H35O2Si2
(Mþ ꢁ 1): 423.2176. Found: 423.2199.
1-(t-Butyldimethylsilyl)-2-(cyclohexylidenemethylene)-3-hy-
1
droxy-3-phenylpropan-1-one (2a). Yellow oil. H NMR ꢂ 0.17
1-(t-Butyldiphenylsilyl)-3-hydroxy-2-(isopropylidenemethyl-
ene)hex-4-en-1-one (2g). Yellow oil. 1H NMR ꢂ 0.83 (s, 3H),
0.87 (s, 3H), 1.01 (s, 9H), 1.69 (d, J ¼ 6:0 Hz, 3H), 3.21 (d, J ¼
6:3 Hz, 1H), 4.93 (dd, J ¼ 6:3, 6.3 Hz, 1H), 5.51 (dd, J ¼ 6:3,
15.0 Hz, 1H), 5.66–5.74 (m, 1H), 7.33–7.67 (m, 10H); 13C NMR
ꢂ 17.7, 18.1, 18.2, 18.7, 26.8, 70.2, 104.7, 115.4, 127.1, 127.7,
127.7, 129.4, 131.3, 133.1, 133.1, 135.6, 135.6, 135.7, 212.3,
233.4; IR (neat) 3451, 1947, 1587 cmꢁ1; HRMS m=z calcd for
C26H31O2Si (Mþ ꢁ 1): 403.2094. Found: 403.2082.
(s, 6H), 0.90 (s, 9H), 1.02–1.10 (m, 1H), 1.21–1.30 (m, 1H), 1.46–
1.65 (m, 4H), 1.89–2.02 (m, 3H), 2.10–2.15 (m, 1H), 3.79 (d, J ¼
2:4 Hz, 1H), 5.66 (d, J ¼ 2:4 Hz, 1H), 7.23–7.33 (m, 5H);
13C NMR ꢂ ꢁ5:4, ꢁ5:3, 16.8, 25.4, 26.0, 26.1, 26.6, 30.4, 30.4,
72.0, 108.9, 117.5, 126.4, 127.1, 128.0, 141.9, 210.1, 235.9; IR
(neat) 3487, 1946, 1575 cmꢁ1; HRMS (FAB) m=z calcd for
C22H31O2Si (Mþ ꢁ 1): 355.2094. Found: 355.2090.
1-(t-Butyldiphenylsilyl)-2-(cyclohexylidenemethylene)-3-hy-
droxy-3-phenylpropan-1-one (2b). To a THF solution (2 mL)
of silyl ether 1b (139.4 mg, 0.30 mmol) was added BuLi (0.72
mmol, 1.59 mol/L hexane solution) dropwise at ꢁ40 ꢂC, and
the mixture was stirred for 10 min. To the resulting mixture was
added benzaldehyde (95.5 mg, 0.90 mmol) at ꢁ40 ꢂC. After being
stirred for 10 min, the reaction mixture was quenched with sat.
NH4Cl (aq), and the organic materials were then extracted with
Et2O. The extracts were then washed with brine and dried over
MgSO4. After evaporation of the solvent, the crude products were
purified by thin-layer chromatography (hexane/ethyl ace-
This research was supported by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Culture, Sports, Sci-
ence and Technology.
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2
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1.26–1.32 (m, 1H), 3.77 (d, J ¼ 4:0 Hz, 1H), 5.71 (d, J ¼ 4:0
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4
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1.55 (m, 3H), 3.18 (d, J ¼ 5:5 Hz, 1H), 4.52 (dt, J ¼ 5:5, 5.5
Hz, 1H), 7.34–7.73 (m, 10H); 13C NMR ꢂ 14.0, 18.6, 18.9, 25.2,
26.1, 26.1, 26.8, 28.8, 29.0, 37.2, 68.8, 110.4, 115.5, 127.6,
5
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7