Mechanistic study on the base-promoted reaction of allylphenylsilanes to alkenylsilanols

Article abstract of DOI:10.1246/bcsj.81.623

On treatment of allylphenylsilanes with t-BuOK and 18-crown-6 in DMSO, isomerization of the olefinic double bond and subsequent substitution of the phenyl group with a hydroxy group took place smoothly to afford alkenylsilanol derivatives in good yields. The reaction mechanism was investigated using ¹⁸O-labeled sulfoxide. We found that a (methylsulfinyl)methyl anion generated from DMSO participated in this reaction.

Full text of DOI:10.1246/bcsj.81.623

Ó 2008 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 81, No. 5, 623–629 (2008)
623
Mechanistic Study on the Base-Promoted Reaction
of Allylphenylsilanes to Alkenylsilanols#
ꢀ1;2
Shigeaki Imazeki,
Hiroo Sugawara,1 Atsunori Sano,1 and Takahiko Akiyama2
1Chemical Products Research Laboratories, Wako Pure Chemical Industries, Ltd., 1633 Matoba, Kawagoe 350-1101
2Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588
Received November 20, 2007; E-mail: imazeki.shigeaki@wako-chem.co.jp
On treatment of allylphenylsilanes with t-BuOK and 18-crown-6 in DMSO, isomerization of the olefinic double
bond and subsequent substitution of the phenyl group with a hydroxy group took place smoothly to afford alkenylsilanol
derivatives in good yields. The reaction mechanism was investigated using 18O-labeled sulfoxide. We found that a
(methylsulfinyl)methyl anion generated from DMSO participated in this reaction.
Temporary silicon connection pioneered by Stork achieved
Ph
Ph
t-BuOK / 18-crown-6
t
t
regiospecific and stereoselective formation of C–C bonds by
bringing together two reaction partners by means of an even-
tually removable silicon atom.1 The silicon-tethered reaction
has been established as an efficient method for the stereoselec-
tive construction of ring systems by numerous types of reac-
tions, such as ionic, radical, photochemical, and cycloaddition
reactions.2 Alkenylsilanols are considered to be useful syn-
thetic units for silyl-tethered reactions. Furthermore, alkenyl-
silanols have been utilized as sila-analogs of the Katsuki–
Sharpless asymmetric epoxidation,3 and in accelerating the
Simmons–Smith reaction, as observed with allylic alcohols.4
Palladium-catalyzed cross coupling has been achieved with
silanols.5 Also the organic chemistry of silanols involving pre-
parative methods as well as applications towards organic syn-
thesis was reported by Hirabayashi and Mori.6 However, little
attention has been given to the synthetic utilization of silanols
because of their instability to moisture, heat, acid, and base,
which has made syntheses and isolation difficult. Although a
number of synthetic methods for alkenylsilanols have been
reported, there remains a lack of excellent synthetic method
for the preparation of alkenylsilanols.7 In order to overcome
the above-mentioned drawbacks, we have developed a sim-
ple base-promoted protocol for the preparation of alkenyl-
silanols from readily available allylsilanes under t-BuOK and
18-crown-6 in DMSO (Scheme 1).8 Anderson and co-workers
reported also the formation of silanols by treating alkenyl-
silanes with t-BuOK and 18-crown-6 in undried THF.9 They
proposed that hydroxide anions could form pentavalent silicon
species, and this reaction was followed by the substitution of a
phenyl group with a hydroxy group.
Si Bu
Si Bu
DMSO / rt
OH
Ph
1a
2a
Scheme 1.
tion of the olefinic double bond took place at room tempera-
ture to afford corresponding alkenylsilane 4a in 82% yield
(Entry 1). The isomerization was completed in 15 min when
DMF was used as solvent (Entry 2). In marked contrast, in
DMSO the reaction course was dramatically changed to give
alkenylsilanol derivative 2a in 80% yield (Entry 3). Addition
of 18-crown-6 improved the yield of 2a to 89% (Entry 4).
Among the bases tested, KH (yield of 2a: 67%), NaH
(12%), and n-BuLi (0%) were not effective. However, when
n-BuLi was employed in DMSO, isomerized alkenylsilane
4a was obtained in 80% yield.
Thus, the base-promoted preparation of 2a was accomplish-
ed by adding t-BuOK and 18-crown-6 to allylsilane 1a in
DMSO at room temperature, and the effect of silyl substitu-
ent was examined under the optimized reaction conditions
(Table 2). Allylsilanes 1 bearing a sterically hindered silyl
group also afforded the corresponding silanols 2 in good
yields. Allyltriphenylsilane 1c gave 2c in 71% yield when
the reaction was carried out initially at ꢁ45 ꢂC and gradually
warmed to room temperature (Entry 3). When allyldimethyl-
phenylsilane was employed, the major product was a disilox-
ane, which was formed by dehydration of dimethylphenylsila-
nol (Entry 4). These results indicate that a t-butyldiphenylsilyl
group is the best for the synthesis of 2.
The results with other allyl-t-butyldiphenylsilanes are
shown in Table 3. Transformation of 2-methyl-2-propenyl-
silane 1e into the corresponding alkenylsilanol 2e was achiev-
ed in 62% yield (Entry 2). When 2-butenylsilane 1f was em-
ployed, the corresponding alkenylsilanol 2f and allylsilanol
5f were obtained each in 20% yield and silanol 3a was ob-
tained in 50% yield (Entry 3). Isomerization using 3-methyl-
2-butenylsilane 1g did not occur but rather gave 3-methyl-2-
butenylsilanol 5g in 22% yield (Entry 4). Isomerization of
In this reaction, the origin of the hydroxy oxygen was of
great interest and studies on the reaction mechanism were
important from the viewpoint of organosilicon chemistry.
We report herein the mechanism of the base-promoted reaction
of allylphenylsilanes in detail.
At the outset, we used several solvents to promote the reac-
tion of allyl-t-butyldiphenylsilane 1a (Table 1). On treatment
of 1a with 1.5 molar amounts of t-BuOK in THF, isomeriza-
Published on the web May 14, 2008; doi:10.1246/bcsj.81.623

624 Bull. Chem. Soc. Jpn. Vol. 81, No. 5 (2008)
Table 1. Effect of Solvent
Mechanism on the Reaction of Allylphenylsilanes
Ph
Ph
Ph
Ph t-BuOK (1.5 mol. amt.)
t
t
t
Si Bu
t
+
HO Si Bu
Si Bu
+
Si Bu
Ph
Ph
rt
OH
Ph
1a
Entry
2a
3a
4a
Solvent
Time/min
Yield of 2a/%
Yield of 3a/%
Yield of 4a/%
1
2
3
4
THF
DMF
DMSO
DMSOa)
12
15
25
15
0
0
80
89
0
0
7
10
82
90
0
0
a) 18-crown-6 (0.36 molar amount) was added.
Table 2. Effect of Silyl Group
R1
R1
R1
t-BuOK / 18-crown-6
Si R2
OH
HO Si R2
Ph
Si R2
+
DMSO / rt
Ph
1
2
3
Entry
R1
R2
Allylsilane
Yield of 2/%
Yield of 3/%
1
2
3
4
t-Bu
i-Pr
Ph
Ph
i-Pr
Ph
1a
1b
1c
1d
2a: 89
2b: 52
2c: 71a)
2d: 0
3a: 10
3b: 29
3c: 19
3d: 44a),b)
Me
Me
a) The reaction was carried out initially at ꢁ45 ꢂC in a mixture of DMSO and THF (v/v = 1/4)
and gradually warmed to rt. b) Isolated as disiloxane produced by dehydration of the silanol.
Table 3. Effect of Allyl Substituents
Ph
Ph
Ph t-BuOK / 18-crown-6
t
t
R2 Si Bu
t
R1 Si Bu
+
HO Si Bu
DMSO / rt
Ph
OH
Ph
1
2
3a
Entry
1
R1
Allylsilane
Conditions
R2
Yield of 2/% Yield of 3a/%
1a
1e
1f
rt/15 min
rt/70 min
rt/30 min
2a: 89
2e: 62
10
20
50
2
3
2f: 20
5f: 20
4
1g
rt/55 min
5g: 22
54
5
6
1h
1i
50 ꢂC/20 min
rt/80 min
2h: 97
2i: 0
0
Ph
Ph
99
the olefinic double bond was dependent on the stability of the
double bond. Although the present transformation generally
proceeded smoothly at room temperature, 3-silylcyclohexene
1h required heating at 50 ꢂC for 20 min (Entry 5). The sub-
stitution of the phenyl group with a hydroxy group on the sil-
icon atom is the rate-determining step as the isomerization of
the double bond took place smoothly at room temperature.
Among these results, the allyl group was a good leaving group
in comparison with the vinyl group. Cinnamylsilane 1i af-
forded only silanol 3a because the cinnamyl moiety was a
good leaving group (Entry 6).
The reactivity of allylsilane 1c was compared with that of
alkenylsilane 4c (Table 4). Whereas alkenylsilanol 2c was ob-
tained in good yield using alkenylsilane 4c at room tempera-
ture, 1c afforded 2c in low yield. This result proved that the
allyl moiety is a good leaving group.
It should be noted that corresponding silyl ether 6 was ob-
tained in high yield by a one-pot procedure when the present
reaction was quenched by the addition of methyl iodide
(Scheme 2).

S. Imazeki et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 5 (2008)
Table 4. Comparison of Allylsilane with Vinylsilane in Reactivity
625
Ph
HO Si Ph
Ph
Ph
Si Ph
OH
Ph t-BuOK / 18-crown-6
+
R1 Si Ph
Ph
DMSO / rt / 20 min
2c
3c
Entry
R1
Silane
1c
Yield of 2c/%
Yield of 3c/%
1
2
23
68
70
26
4c
Ph
Ph
Si Bu
Ph
t-BuOK / 18-crown-6
MeI
t
t
Si Bu
DMSO / rt
OMe
1a
6 (77%)
Scheme 2.
In order to clarify the participation of a (methylsulfinyl)-
Ph
methyl anion, other sulfoxides were examined (Table 5).
When dibutyl sulfoxide and dodecyl methyl sulfoxide were
used, the yield of 2a decreased (Entries 2 and 3). This reduc-
tion of yield could be brought about by steric hindrance of the
ꢀ-carbanions of these sulfoxides. It is noted that 2a was not
obtained at all when di-t-butyl sulfoxide was used.
Finally, a labeling experiment was performed. 18O-Labeled
dibutyl sulfoxide 7 was obtained by treating dibutyl sul-
fide with N-bromosuccinimide in H218O–MeOH solution
(Scheme 5). GC-MS analysis of the sulfoxide showed that
its 18O content was 90%. When the reaction was carried out
under standard reaction conditions employing 7 as solvent,
18O-labeled silanol (2a-18O) was obtained (Scheme 6).
The combination of t-BuOK with DMSO is used to cleave
C–Si bonds.10,11 The present transformation was found to pro-
t
Si Bu
Ph
t-BuOK / 18-crown-6
t
OH
Si Bu
DMSO-d6 / rt
Ph
D
D
1a
2a-D
D content: α:70%, γ:87%
Scheme 3.
Use of DMSO-d6 as solvent led to the incorporation of
deuterium at both ꢀ and ꢁ positions to silicon (Scheme 3).
On the other hand, deuterium was not incorporated at the
alkenyl moiety when the reaction mixture was treated with
D2O (Scheme 4). Only deuterium exchange of the hydroxy
group occurred. These results suggest that a (methylsulfinyl)-
methyl anion generated from DMSO took part in the isomeri-
zation of the double bond.
Ph
Ph
t-BuOK / 18-crown-6
D2O
t
t
Si Bu
Si Bu
DMSO / rt
OH
Ph
1a
2a (74%)
Scheme 4.
Table 5. Effect of Sulfoxide
t-BuOK (2.0 mol. amt.)
Ph
Ph
Ph
Ph
18-crown-6
t
t
t
t
Si Bu
+
HO Si Bu
+
Si Bu
OH
Si Bu
Ph
Ph
sulfoxide
Ph
1a
2a
3a
4a
Entry
1
Sulfoxide
Conditions
Yield of 2a/%
Yield of 3a/%
Yield of 4a/%
DMSO
rt/15 min
89
10
0
O
S
2
50 ꢂC/4 h
49
39
0
24
9
19
45
93
Bu
Bu
O
3a)
50 ꢂC/4 h
50 ꢂC/4 h
S
n-C12H25
O
S
4
0
a) THF was used as solvent.

626 Bull. Chem. Soc. Jpn. Vol. 81, No. 5 (2008)
Mechanism on the Reaction of Allylphenylsilanes
18O
S
S
NBS
nBu nBu
+
MeOH-H218O
Bu
Bu
(1.0 mol. amt.)
(1.1 mol. amt.) (18O content: 95%)
7 (88%, 18O content: 90%)
Scheme 5.
and CDCl3 was used as an internal standard (ꢂ 77.0) for 13C NMR.
Analytical thin-layer chromatography (TLC) was performed on
commercial Merck plates coated with silica gel 60 F-254. Visual-
ization was accomplished with UV light. All reagents were com-
mercially available from Wako Pure Chemical Industries Ltd.,
Japan.
Ph
Si tBu
18OH
Ph
t-BuOK / 18-crown-6
7 / 50 °C
t
Si Bu
Ph
1a
2a-18O (18O content: 53%)
Scheme 6.
t-Butyldiphenyl-2-propenylsilane (1a).
Allylmagnesium
chloride was prepared from allyl chloride and magnesium in
THF according to standard procedure. t-Butylchlorodiphenyl-
silane (25 g, 90.96 mmol) was added to the Grignard reagent
(150 mL, 181.91 mmol, 1.21 mol Lꢁ1) at room temperature. After
being stirred at reflux for 3.5 h, the reaction mixture was quenched
by adding 1 mol dmꢁ3 HCl solution at 0 ꢂC. The aqueous layer
was extracted with EtOAc. The combined organic layers were
washed with brine, dried over anhydrous Na2SO4, and concentrat-
ed to dryness. Purification of the crude mixture by column chro-
matography (SiO2, hexane/EtOAc = 30/1, v/v) gave t-butyl-
diphenyl-2-propenylsilane (1a) in 91% yield.
Colorless oil. Rf ¼ 0:6 (hexane/EtOAc = 30/1). 1H NMR
(400 MHz, CDCl3) ꢂ 7.62–7.60 (4H, m), 7.37–7.32 (6H, m),
5.77 (1H, ddt, J ¼ 17:0, 10.0, 7.8 Hz), 4.90 (1H, dd, J ¼ 17:0,
3.1 Hz), 4.79 (1H, dd, J ¼ 10:0, 3.1 Hz), 2.18 (2H, dd, J ¼ 7:8,
1.2 Hz), 1.07 (9H, s). 13C NMR (100 MHz, CDCl3) ꢂ 135.9, 134.6,
134.4, 129.0, 127.5, 114.5, 27.9, 18.9, 18.6. IR (neat) 2928, 2859,
1470, 1427, 1157, 1104, 895, 820, 764, 732, 697, 624, 613, 578,
482, 425 cmꢁ1. MS(EI) m=z (%) 280 (5), 223 (100), 182 (50), 146
(60). Found: C, 81.55; H, 8.90%. Calcd for C19H24Si: C, 81.36; H,
8.62%.
ceed via initial isomerization of the olefinic double bond fol-
lowed by substitution of the phenyl group with a hydroxy
group. The fact that treatment with methyl iodide furnished
corresponding silyl ether 6 in good yield (Scheme 2) suggests
that a silanolate anion would be formed in the present reaction.
On the basis of our experimental data, we propose the fol-
lowing mechanism for the reaction of 1a (Scheme 7). Initially,
base-catalyzed isomerization of the olefinic double bond took
place smoothly to afford alkenylsilane 4a.12 Attack of a (meth-
ylsulfinyl)methyl anion to the silicon atom, followed by proton
abstraction from DMSO, gave sulfonium salt 8 via penta-coor-
dinate silicate species. The nucleophilic attack of 8 by a nu-
cleophile afforded silanolate intermediate 9. When an allyl-
silane bearing a less sterically hindered silyl substituent was
employed, (methylsulfinyl)methyl anion easily attacked the
silyl moiety, leading to the elimination of the allyl group to
form silanol 3.
Conclusion
In conclusion, we have designed a facile method for the
preparation of alkenylsilanols from allylsilanes by use of
t-BuOK in DMSO. In addition, we have elucidated the reaction
mechanism on the basis of labeling experiments.
Diisopropylphenyl-2-propenylsilane (1b). A dibutyl ether
solution of PhLi (154 mL, 324 mmol, 2.10 mol Lꢁ1) was added
to a solution of dichlorodiisopropylsilane (50.0 g, 270 mmol)
in THF (100 mL) at 0 ꢂC. After being stirred at room tempera-
ture for 2 h, allylmagnesium chloride (360 mL, 540 mmol, 1.50
mol Lꢁ1), generated by the reaction of allyl chloride and magne-
sium in another flask, was added to the reaction mixture at 0 ꢂC.
After being stirred at reflux for 3 h, the reaction was quenched
by adding 1 mol dmꢁ3 HCl solution at 0 ꢂC. The aqueous layer
Experimental
NMR spectra were measured in CDCl3 on an AL400 instru-
ment (JEOL, 400 MHz for 1H, 100 MHz for 13C). Tetramethyl-
silane (TMS) (ꢂ 0) served as an internal standard for 1H NMR
Ph
Ph
Ph
t
Si Bu
t
t
Si Bu
Si Bu
Ph
Ph
Ph
H
H
O
S
H
O
S
H2C
S
CH3
CH2
H2C
O
Ph
Ph
Ph
Ph
Ph
Si Bu
Ph
t
DMSO
t
t
t
Si Bu
Si Bu
Si Bu
O-
O
O
9
H3C
S
Nu
O
H3C
S
CH2
CH2
S
H3C
CH2
8
Scheme 7.

S. Imazeki et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 5 (2008)
627
was extracted with EtOAc. The combined organic layers were
washed with brine, dried over anhydrous Na2SO4, and concentrat-
ed to dryness. Purification of the crude mixture by column chro-
matography (SiO2, hexane/EtOAc = 30/1, v/v) gave allyldiiso-
propylphenylsilane (1b) in 85% yield.
1470, 1426, 1103, 819, 729, 697, 669, 605, 505, 481, 456, 418,
401 cmꢁ1. MS(EI) m=z (%) 308 (10), 251 (100), 182 (40), 174
(50). Found: C, 82.09; H, 9.33%. Calcd for C21H28Si: C, 81.75;
H, 9.15%.
3-(t-Butyldiphenylsilyl)-1-cyclohexene (1h).
3-Chloro-1-
Colorless oil. Rf ¼ 0:8 (hexane/EtOAc = 30/1). 1H NMR
(400 MHz, CDCl3) ꢂ 7.52 (2H, d, J ¼ 6:1 Hz), 7.38–7.34 (3H, m),
5.91 (1H, dddd, J ¼ 16:8, 10.0, 8.1, 8.0 Hz), 4.98 (1H, d, J ¼ 16:8
Hz), 4.86 (1H, d, J ¼ 10:0 Hz), 1.94 (2H, d, J ¼ 8:1 Hz), 1.29
(2H, dq, J ¼ 7:6, 7.1 Hz), 1.05–0.94 (12H, m). 13C NMR (100
MHz, CDCl3) ꢂ 139.6, 135.1, 133.7, 128.7, 127.5, 113.2, 27.6,
18.6, 18.5, 18.4, 18.3, 10.8, 10.6. IR (neat) 2930, 2855, 1472,
1419, 1110, 888, 820, 764, 739, 710, 611, 573, 423 cmꢁ1. MS(EI)
m=z (%) 232 (10), 190 (100), 153 (50), 146 (30), 112 (50). Found:
C, 77.90; H, 10.70%. Calcd for C15H24Si: C, 77.51; H, 10.41%.
Triphenyl-2-propenylsilane (1c). White crystals; mp 95.4–
96.6 ꢂC (hexane). Rf ¼ 0:6 (hexane/EtOAc = 30/1). 1H NMR
(400 MHz, CDCl3) ꢂ 7.58–7.51 (6H, m), 7.44–7.32 (9H, m), 5.88
(1H, dddd, J ¼ 15:3, 10.0, 7.8, 2.1 Hz), 4.93 (1H, dd, J ¼ 15:3,
1.6 Hz), 4.87 (1H, d, J ¼ 10:0 Hz), 2.39 (2H, d, J ¼ 7:8 Hz).
13C NMR (100 MHz, CDCl3) ꢂ 135.7, 134.5, 133.7, 129.5, 127.8,
115.0, 21.3. IR (neat) 3039, 1627, 1485, 1427, 1155, 1110, 1044,
1027, 996, 932, 892, 771, 728, 695, 588, 472, 434 cmꢁ1. MS(EI)
m=z (%) 300 (60), 259 (50), 223 (100), 146 (50), 69 (10). Found:
C, 83.77; H, 6.89%. Calcd for C21H20Si: C, 83.94; H, 6.71%.
Dimethylphenyl-2-propenylsilane (1d). Colorless oil. Rf ¼
0:8 (hexane/EtOAc = 30/1). 1H NMR (400 MHz, CDCl3) ꢂ
7.51–7.48 (2H, m), 7.34–7.32 (3H, m), 5.77 (1H, ddt, J ¼ 18:9,
8.5, 7.8 Hz), 4.84 (1H, d, J ¼ 18:9 Hz), 4.83 (1H, d, J ¼ 8:5
Hz), 1.74 (2H, d, J ¼ 7:8 Hz), 0.27 (3H, s), 0.26 (3H, s). 13C NMR
(100 MHz, CDCl3) ꢂ 138.6, 134.5, 133.5, 128.9, 127.7, 113.3,
23.86, ꢁ3:4. IR (neat) 3069, 2957, 1629, 1427, 1248, 1192,
1155, 1113, 1035, 991, 931, 893, 831, 816, 725, 696, 645, 568,
466 cmꢁ1. MS(EI) m=z (%) 176 (70), 135 (100), 99 (70), 58
(30). Found: C, 75.24; H, 9.33%. Calcd for C11H16Si: C, 74.93;
H, 9.15%.
cyclohexene (1.65 g, 14.12 mmol) was added to a solution of tri-
butylstannyl chloride (1.31 g, 4.03 mmol) and magnesium (0.29 g,
12.10 mmol) in THF (10 mL) at reflux. After being stirred at reflux
for 3.5 h, the reaction was quenched by adding 1 mol dmꢁ3 HCl
solution at 0 ꢂC. The aqueous layer was extracted with EtOAc.
The combined organic layers were washed with brine, dried over
anhydrous Na2SO4, and concentrated to dryness. Purification of
the crude mixture by distillation (130–145 ꢂC, 7 Torr) gave 3-(tri-
butylstannyl)-1-cyclohexene in 93% yield as colorless oil. An ether
solution of MeLi (3.4 mL, 3.88 mmol, 1.14 mol Lꢁ1) was added to
a solution of the allylstannane (1.44 g, 3.88 mmol) in THF (30 mL)
at ꢁ90 ꢂC. After being stirred at ꢁ90 ꢂC for 2 h, t-butyldiphenyl-
chlorosilane (2.13 g, 7.74 mmol) was added to the reaction mix-
ture at ꢁ90 ꢂC. After being stirred at ꢁ78 ꢂC for 1.5 h, the reaction
was quenched by adding 1 mol dmꢁ3 HCl solution at 0 ꢂC. The
aqueous layer was extracted with EtOAc. The combined organic
layers were washed with brine, dried over anhydrous Na2SO4,
and concentrated to dryness. Purification of the crude mixture
by column chromatography (SiO2, hexane/EtOAc = 50/1, v/v)
gave 3-(t-butyldiphenylsilyl)-1-cyclohexene (1h) in 70% yield.
White crystals; mp 81.4–82.5 ꢂC (hexane). Rf ¼ 0:4 (hexane).
1H NMR (400 MHz, CDCl3) ꢂ 7.67 (2H, dd, J ¼ 1:3, 6.5 Hz),
7.57 (2H, dd, J ¼ 1:5, 6.3 Hz), 7.38–7.30 (6H, m), 5.88 (1H, d,
J ¼ 10:0 Hz), 5.68–5.65 (1H, m), 2.39–2.36 (1H, m), 1.97–1.93
(2H, m), 1.87–1.83 (1H, m), 1.69–1.65 (2H, m), 1.45–1.39 (1H,
m), 1.11 (9H, s). 13C NMR (100 MHz, CDCl3) ꢂ 136.1, 134.6,
128.8, 128.4, 127.3, 126.2, 29.0, 25.2, 25.1, 23.69, 23.3, 19.0.
IR (neat) 2922, 2854, 2360, 1461, 1425, 1102, 889, 821, 737,
717, 698, 626, 599, 536, 501, 482, 467, 437 cmꢁ1. MS(EI) m=z
(%) 320 (15), 263 (15), 240 (100), 186 (50), 183 (30). Found:
C, 81.33; H, 9.02%. Calcd for C22H28Si: C, 82.43; H, 8.80%.
t-Butyl(2-methyl-2-propenyl)diphenylsilane (1e). Colorless
1
3-Phenyl-2-propenyl-t-butyldiphenylsilane (1i):
Prepared
oil. Rf ¼ 0:4 (hexane). H NMR (400 MHz, CDCl3) ꢂ 7.64–7.60
according to the method for the preparation of 1h. Colorless oil.
Rf ¼ 0:4 (hexane/EtOAc = 40/1). 1H NMR (400 MHz, CDCl3)
ꢂ 7.64–7.60 (4H, m), 7.37–7.31 (6H, m), 7.19–7.12 (5H, m), 6.23–
6.21 (2H, m), 2.33 (2H, d, J ¼ 7:1 Hz), 1.09 (9H, s). 13C NMR
(100 MHz, CDCl3) ꢂ 141.3, 138.2, 135.9, 134.3, 129.8, 129.1,
128.4, 127.5, 126.2, 125.5, 114.5, 28.0, 18.6, 18.2. IR (neat)
2928, 2856, 1470, 1154, 1104, 998, 961, 819, 733, 697, 604,
520, 481 cmꢁ1. MS(EI) m=z (%) 357 (5), 299 (100), 240 (50), 222
(40), 183 (30). Found: C, 84.69; H, 7.65%. Calcd for C25H28Si: C,
84.21; H, 7.91%.
(4H, m), 7.40–7.24 (6H, m), 4.56 (2H, d, J ¼ 5:7 Hz), 2.20
(2H, s), 1.38 (3H, s), 1.05 (9H, s). 13C NMR (100 MHz, CDCl3)
ꢂ 143.5, 136.2, 134.9, 129.0, 127.4, 110.8, 27.8, 22.2, 18.6. IR
(neat) 2928, 2855, 1615, 1427, 1103, 819, 799, 733, 697, 676,
607, 526, 498, 461, 443, 427 cmꢁ1. MS(EI) m=z (%) 294 (5),
237 (100), 182 (30), 160 (50). Found: C, 81.33; H, 9.02%. Calcd
for C20H26Si: C, 81.57; H, 8.90%.
2-Butenyl-t-butyldiphenylsilane (1f). Colorless oil. Rf ¼ 0:8
(hexane/EtOAc = 40/1). (E=Z ¼ 3=1) 1H NMR (400 MHz,
CDCl3) ꢂ 7.62–7.58 (4H, m), 7.40–7.34 (6H, m), 5.38–5.23 (2H,
m), 2.12–2.04 (2H, m), 1.52 (E, 2.25H, d, J ¼ 7:3 Hz), 1.42 (Z,
0.75H, d, J ¼ 6:6 Hz), 1.05 (9H, s). 13C NMR (100 MHz, CDCl3)
ꢂ 136.0, 134.7, 128.9, 127.6, 126.4 (E), 125.7 (Z), 124.8 (E),
122.7 (Z), 27.8, 18.5, 18.0 (E), 16.9 (E), 12.7 (Z), 12.0 (Z). IR
(neat) 2929, 2856, 1471, 1426, 1104, 963, 820, 753, 735, 697,
665, 651, 604, 512, 481, 458, 411 cmꢁ1. MS(EI) m=z (%) 294
(5), 237 (100), 182 (40), 160 (40). Found: C, 81.25; H, 8.77%.
Calcd for C20H26Si: C, 81.57; H, 8.90%.
Typical Procedure for Preparation of (E)-t-Butylphenyl-1-
propenylsilanol (2a). A solution of t-butyldiphenyl-2-propenyl-
silane (1a) (49.0 mg, 0.17 mmol) in DMSO (0.5 mL) and 18-
crown-6 (16.6 mg, 0.06 mmol) were successively added to potas-
sium t-butoxide (35.3 mg, 0.31 mmol) at room temperature. After
being stirred at room temperature for 15 min, the reaction was
quenched by adding 1 mol dmꢁ3 HCl solution. The aqueous layer
was extracted with EtOAc. The combined organic layers were
washed with brine, dried over anhydrous Na2SO4, and concentrat-
ed to dryness. Purification of the crude mixture by column chro-
matography (SiO2, hexane/EtOAc = 7/1, v/v) gave (E)-t-butyl-
phenyl-1-propenylsilanol (2a) in 89% yield (E=Z ¼ 97=3).
t-Butyl(3-methyl-2-butenyl)diphenylsilane (1g). Colorless
oil. Rf ¼ 0:8 (hexane/EtOAc = 40/1). 1H NMR (400 MHz,
CDCl3) ꢂ 7.60–7.57 (4H, m), 7.38–7.30 (6H, m), 5.16 (1H, t, J ¼
8:1 Hz), 2.02 (2H, d, J ¼ 8:1 Hz), 1.55 (3H, s), 1.38 (3H, s), 1.06
(9H, s). 13C NMR (100 MHz, CDCl3) ꢂ 135.9, 135.0, 128.8, 127.7,
127.3, 119.3, 28.0, 25.8, 18.4, 17.6, 12.6. IR (neat) 2927, 2855,
1
Colorless oil. Rf ¼ 0:4 (hexane/EtOAc = 7/1). H NMR (400
MHz, CDCl3) ꢂ 7.62–7.55 (2H, m), 7.43–7.32 (3H, m), 6.32 (1H,
dq, J ¼ 18:6, 6.2 Hz), 5.92 (1H, dq, J ¼ 18:6, 1.7 Hz), 2.35–2.29

628 Bull. Chem. Soc. Jpn. Vol. 81, No. 5 (2008)
Mechanism on the Reaction of Allylphenylsilanes
(1H, br), 1.87 (3H, dd, J ¼ 6:2, 1.7 Hz), 0.95 (9H, s). 13C NMR
(100 MHz, CDCl3) ꢂ 147.6, 134.4, 129.0, 127.3, 127.1, 124.4,
26.6, 25.5, 18.4. IR (neat) 3376, 2929, 2856, 1618, 1471, 1427,
1390, 1361, 1111, 985, 939, 819, 761, 735, 698, 608, 492, 476
cmꢁ1. MS(EI) m=z (%) 220 (5), 163 (100), 137 (20), 123 (90).
Found: C, 71.01; H, 8.96%. Calcd for C13H20OSi: C, 70.85; H,
9.15%.
(E)-Diisopropyl-1-propenylsilanol (2b). Colorless oil. Rf ¼
0:5 (hexane/EtOAc = 7/1). 1H NMR (400 MHz, CDCl3) ꢂ 6.24
(1H, dq, J ¼ 17:8, 5.3 Hz), 5.57 (1H, dq, J ¼ 17:8, 1.6 Hz), 1.93–
1.82 (1H, br), 1.85 (3H, dd, J ¼ 5:3, 1.6 Hz), 1.28–1.18 (2H, m),
1.08–0.92 (12H, m). 13C NMR (100 MHz, CDCl3) ꢂ 135.4, 125.3,
22.8, 17.2, 12.7. IR (neat) 3365, 2928, 2850, 1618, 1472, 1425,
1390, 1362, 1111, 985, 939, 819, 765, 610, 495 cmꢁ1. MS(EI)
m=z (%) 172 (10), 129 (100), 76 (40). Found: C, 63.10; H,
11.99%. Calcd for C9H20OSi: C, 62.72; H, 11.70%.
1111, 998, 819, 737, 698, 606, 502, 487, 431 cmꢁ1. MS(EI) m=z
(%) 248 (20), 191 (100), 179 (20), 123 (20). Found: C, 72.90;
H, 10.11%. Calcd for C15H24OSi: C, 72.52; H, 9.74%.
t-Butyl(1-cyclohexenyl)phenylsilanol (2h).
Colorless oil.
Rf ¼ 0:4 (hexane/EtOAc = 10/1). 1H NMR (400 MHz, CDCl3)
ꢂ 7.66–7.60 (2H, m), 7.38–7.31 (3H, m), 6.30 (1H, m), 2.20–
2.11 (2H, m), 2.11–2.04 (2H, m), 2.02–1.94 (1H, br), 1.65–1.55
(4H, m), 1.00 (9H, s). 13C NMR (100 MHz, CDCl3) ꢂ 140.8,
135.7, 134.5, 134.4, 129.2, 127.5, 28.0, 26.9, 25.7, 22.9, 22.2,
18.88. IR (neat) 3419, 2927, 2855, 1609, 1471, 1427, 1361,
1061, 936, 800, 738, 696, 612, 553, 506, 478 cmꢁ1. MS(EI) m=z
(%) 260 (10), 203 (100), 123 (30). Found: C, 74.03; H, 9.60%.
Calcd for C16H24OSi: C, 73.79; H, 9.29%.
t-Butyldiphenylsilanol (3a). Colorless oil. Rf ¼ 0:4 (hexane/
EtOAc = 7/1). 1H NMR (400 MHz, CDCl3) ꢂ 7.72–7.70 (4H, m),
7.40–7.35 (6H, m), 2.35–2.29 (1H, br), 1.06 (9H, s). 13C NMR
(100 MHz, CDCl3) ꢂ 135.1, 134.7, 129.6, 127.7, 26.6, 19.1. IR
(neat) 3445, 2929, 2856, 1674, 1598, 1471, 1112, 820, 741,
700, 607, 505 cmꢁ1. MS(EI) m=z (%) 256 (5), 199 (100). Found:
C, 74.88; H, 7.95%. Calcd for C16H20OSi: C, 74.95; H, 7.86%.
(E)-Diphenyl-1-propenylsilanol (2c).
White crystals; mp
135.2–137.4 ꢂC (hexane). Rf ¼ 0:4 (hexane/EtOAc = 7/1).
1H NMR (400 MHz, CDCl3) ꢂ 7.60–7.57 (4H, m), 7.42–7.32 (6H,
m), 6.28 (1H, dq, J ¼ 18:6, 6.0 Hz), 5.98 (1H, d, J ¼ 18:6 Hz),
3.01–2.82 (1H, br), 1.86 (3H, d, J ¼ 6:0 Hz). 13C NMR (100
MHz, CDCl3) ꢂ 148.2, 135.1, 134.9, 134.5, 129.7, 127.8, 127.7,
126.2, 22.7. IR (neat) 3246, 3068, 2360, 2324, 1427, 1117, 997,
831, 736, 709, 694, 506 cmꢁ1. MS(EI) m=z (%) 240 (45), 199
(100), 163 (20), 147 (15), 123 (70). Found: C, 74.66; H, 6.99%.
Calcd for C15H16OSi: C, 74.95; H, 6.71%.
(E)-t-Butyldiphenyl-1-propenylsilane (4a).
A solution of
t-butyldiphenyl-2-propenylsilane (1a) (48.1 mg, 0.17 mmol) in
DMF (0.5 mL) was added to potassium t-butoxide (38.5 mg,
0.34 mmol) at room temperature. After being stirred at room tem-
perature for 15 min, the reaction was quenched by adding
1 mol dmꢁ3 HCl solution. The aqueous layer was extracted with
EtOAc. The combined organic layers were washed with brine,
dried over anhydrous Na2SO4, and concentrated to dryness. Puri-
fication of the crude mixture by column chromatography (SiO2,
hexane/EtOAc = 25/1, v/v) gave 4a in 90% yield.
Colorless oil. Rf ¼ 0:5 (hexane/EtOAc = 25/1). 1H NMR
(400 MHz, CDCl3) ꢂ 7.62–7.57 (4H, m), 7.39–7.30 (6H, m),
6.08–6.03 (2H, m), 1.90 (3H, dd, J ¼ 2:9, 1.5 Hz), 1.07 (9H, s).
13C NMR (100 MHz, CDCl3) ꢂ 147.7, 136.2, 135.1, 128.9, 127.5,
124.6, 27.3, 23.0, 18.1. IR (neat) 2958, 2928, 2856, 1617, 1457,
1192, 1104, 1049, 819, 697, 605, 506, 486 cmꢁ1. MS(EI) m=z
(%) 223 (100), 183 (40), 146 (15), 105 (25). Found: C, 81.41;
H, 8.84%. Calcd for C19H24Si: C, 81.36; H, 8.62%.
(E)-t-Butylphenyl-1-propenylsilyl Methyl Ether (6). A solu-
tion of t-butyldiphenyl-2-propenylsilane (1a) (47.4 mg, 0.17
mmol) in DMSO (0.5 mL) and 18-crown-6 (13.4 mg, 0.05 mmol)
were successively added to potassium t-butoxide (28.4 mg,
0.25 mmol) at room temperature. After being stirred at that tem-
perature for 20 min, the reaction was quenched by adding methyl
iodide (119.9 mg, 0.84 mmol). After stirring the reaction mixture
for 10 min, water was added. The aqueous layer was extracted
with EtOAc. The combined organic layers were washed with
brine, dried over anhydrous Na2SO4, and concentrated to dryness.
Purification of the crude mixture by column chromatography
(SiO2, hexane/EtOAc = 40/1, v/v) gave t-butylphenyl-1-pro-
penylsilyl methyl ether (6) in 77% yield.
t-Butyl-(2-methyl-1-propenyl)phenylsilanol (2e). Colorless
oil. Rf ¼ 0:4 (hexane/EtOAc = 7/1). 1H NMR (400 MHz,
CDCl3) ꢂ 7.62–7.59 (2H, m), 7.40–7.33 (3H, m), 5.51 (1H, s),
2.08–1.93 (1H, br), 1.92 (3H, s), 1.72 (3H, s), 0.94 (9H, s).
13C NMR (100 MHz, CDCl3) ꢂ 157.6, 135.2, 134.8, 129.6,
127.7, 117.7, 26.6, 25.9, 24.0, 18.4. IR (neat) 3421, 2929, 2856,
1617, 1471, 1427, 1361, 1111, 1007, 939, 807, 737, 698, 607,
502, 447 cmꢁ1. MS(EI) m=z (%) 177 (100), 122 (50). Found: C,
72.01; H, 9.11%. Calcd for C14H22OSi: C, 71.73; H, 9.46%.
(E)-(1-Butenyl)-t-butylphenylsilanol (2f).
Colorless oil.
1
Rf ¼ 0:4 (hexane/EtOAc = 7/1). H NMR (400 MHz, CDCl3) ꢂ
7.60–7.57 (2H, m), 7.41–7.40 (3H, m), 6.37 (1H, dt, J ¼ 18:7,
6.3 Hz), 5.88 (1H, dd, J ¼ 18:7, 1.1 Hz), 2.18 (2H, dq, J ¼ 7:6,
6.3 Hz), 2.12–2.04 (1H, br), 0.96 (3H, t, J ¼ 7:6 Hz), 0.95 (9H,
s). 13C NMR (100 MHz, CDCl3) ꢂ 153.6, 136.0, 134.5, 129.3,
127.5, 121.7, 27.8, 26.0, 18.4, 17.9. IR (neat) 3411, 2929, 2856,
2360, 1471, 1427, 1391, 1361, 1112, 998, 819, 737, 698, 606,
503, 486, 431 cmꢁ1. MS(EI) m=z (%) 177 (100), 122 (50). Found:
C, 71.50; H, 9.56%. Calcd for C14H22OSi: C, 71.73; H, 9.46%.
(E)-(2-Butenyl)-t-butylphenylsilanol (5f).
Colorless oil.
1
Rf ¼ 0:4 (hexane/EtOAc = 7/1). H NMR (400 MHz, CDCl3) ꢂ
7.62–7.57 (2H, m), 7.41–7.40 (3H, m), 5.42–5.36 (2H, m),
2.48–2.36 (1H, br), 1.85 (2H, d, J ¼ 7:1 Hz), 1.56 (3H, d, J ¼
5:1 Hz), 0.93 (9H, s). 13C NMR (100 MHz, CDCl3) ꢂ 135.2, 134.1,
129.5, 127.4, 125.5, 125.0, 27.8, 27.0, 19.1, 18.6. IR (neat) 3411,
2929, 2856, 2360, 1471, 1427, 1391, 1361, 1112, 998, 819, 737,
698, 606, 503, 486, 431 cmꢁ1. MS(EI) m=z (%) 177 (100), 122
(50). Found: C, 71.52; H, 9.56%. Calcd for C14H22OSi: C, 71.73;
H, 9.46%.
Colorless oil. Rf ¼ 0:4 (hexane/EtOAc = 40/1). 1H NMR
(400 MHz, CDCl3) ꢂ 7.61–7.53 (2H, m), 7.42–7.30 (3H, m), 6.35
(1H, dq, J ¼ 18:8, 6.1 Hz), 5.84 (1H, d, J ¼ 18:8 Hz), 3.50 (3H,
s), 1.84 (3H, d, J ¼ 6:1 Hz), 0.92 (9H, s). 13C NMR (100 MHz,
CDCl3) ꢂ 146.0, 135.2, 134.1, 129.3, 127.5, 123.1, 51.7, 26.0,
23.0, 18.3. IR (neat) 2930, 2856, 1617, 1472, 1427, 1188, 1082,
988, 823, 734, 700, 611, 503 cmꢁ1. MS(EI) m=z (%) 177 (100),
137 (40), 107 (20). Found: C, 71.49; H, 9.61%. Calcd for C14H22-
OSi: C, 71.73; H, 9.46%.
t-Butyl(3-methyl-2-butenyl)phenylsilanol (5g).
Colorless
oil. Rf ¼ 0:4 (hexane/EtOAc = 7/1). 1H NMR (400 MHz,
CDCl3) ꢂ 7.61–7.57 (2H, m), 7.40–7.34 (3H, m), 5.30 (1H, dd,
J ¼ 7:6, 1.3 Hz), 2.39–2.28 (1H, br), 1.83 (2H, dd, J ¼ 12:2, 7.6
Hz), 1.64 (3H, s), 1.57 (3H, s), 0.96 (9H, s). 13C NMR (100 MHz,
CDCl3) ꢂ 135.8, 134.2, 130.7, 129.4, 127.5, 118.2, 26.1, 25.8,
18.5, 17.8, 13.9. IR (neat) 3414, 2929, 2856, 1471, 1427, 1361,
Dibutyl Sulfoxide-18O (7).
(10.00 g, 68.36 mmol) in dried methanol (20 mL) and water-18O
A solution of dibutyl sulfide

S. Imazeki et al.
Bull. Chem. Soc. Jpn. Vol. 81, No. 5 (2008)
629
(2.00 g, 100.00 mmol) was added to N-bromosuccinimide (13.14
g, 75.19 mmol) and the temperature was kept at 10 ꢂC. After being
stirred and keeping the reaction mixture at 0 ꢂC for 45 min,
CH2Cl2 was added. The organic layers were washed successively
with sat. NaHCO3, brine, dried over anhydrous Na2SO4, and con-
centrated to dryness. Purification of the crude mixture by distilla-
tion (122–125 ꢂC, 3 Torr) gave dibutyl sulfoxide-18O (6) in 88%
(18O content: 90%) yield as colorless crystals.
W. Waldmann, VCH, Weinheim, 1995, p. 135.
3
Chem. Commun. 1988, 1280; K. Yamamoto, Y. Kawanami, M.
Miyazawa, J. Chem. Soc., Chem. Commun. 1993, 436; L. H. Li,
D. Wang, T. H. Chan, Tetrahedron Lett. 1997, 38, 101.
T. H. Chan, L. M. Chen, D. Wang, J. Chem. Soc.,
4 K. Hirabayashi, A. Mori, T. Hiyama, Tetrahedron Lett.
1997, 38, 461.
5
K. Hirabayashi, Y. Nishihara, A. Mori, T. Hiyama, Tetra-
Colorless crystals. mp 32.3–34.1 ꢂC. Rf ¼ 0:2 (hexane/
EtOAc = 1/1). 1H NMR (400 MHz, CDCl3) ꢂ 2.69 (4H, t,
J ¼ 7:7 Hz), 1.79–1.71 (4H, m), 1.59–1.42 (4H, m), 0.97 (6H, t,
J ¼ 7:3 Hz). 13C NMR (100 MHz, CDCl3) ꢂ 51.0, 23.1, 21.7,
12.7. IR(neat) 2656, 2928, 2871, 1466, 1412, 983, 920, 736,
427 cmꢁ1. MS(EI) m=z (%) 164 (30), 146 (50), 108 (60), 89
(100), 61 (60). Found: C, 59.01; H, 11.55%. Calcd for C8H1818OS
(18O content: 90%): C, 59.14; H, 11.73%.
hedron Lett. 1998, 39, 7893; K. Hirabayashi, J. Kawashima, Y.
Nishihara, A. Mori, T. Hiyama, Org. Lett. 1999, 1, 299; S. E.
Denmark, D. Wehrli, Org. Lett. 2000, 2, 565.
6 K. Hirabayashi, A. Mori, J. Synth. Org. Chem., Jpn. 2000,
58, 926.
7
S. M. Sieburth, W. Mu, J. Org. Chem. 1993, 58, 7584;
A. Mori, T. Hishida, Y. Soga, Y. Kawakami, Chem. Lett. 1995,
107; A. Mori, H. Sato, K. Mizuno, T. Hiyama, K. Shintani, Y.
Kawakami, Chem. Lett. 1996, 517; K. Takaku, H. Shinokubo,
K. Oshima, Tetrahedron Lett. 1996, 37, 6781.
The authors are grateful to Drs. Takumi Tanaka and Kazuo
Shiraki for helpful discussion. The authors also thank Drs.
Shigeru Kobayashi and Ryohiko Kinoshita for advice and
encouragement.
8
9
T. Akiyama, S. Imazeki, Chem. Lett. 1997, 1077.
J. C. Anderson, A. Flaherty, J. Chem. Soc., Perkin Trans. 1
2000, 3025; J. C. Anderson, S. Anguille, R. Bailey, Chem. Com-
mun. 2002, 2018.
10 Tetramethylsilane is cleaved by t-BuOK in DMSO: C. C.
Price, J. R. Sowa, J. Org. Chem. 1967, 32, 4126.
11 P. F. Hudrlik, A. M. Hudrlik, A. K. Kulkarni, J. Am. Chem.
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H. Nakamura, P. G. Andersson, Y. Ito, J. Am. Chem. Soc. 1993,
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