1,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene: Regioselective ring opening of its α,β-epoxybis(silane) with some nucleophiles

Article abstract of DOI:10.1016/j.jorganchem.2009.01.030

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyllithium, (Me₃Si)₃CLi, in Et₂O gives disubstituted vinylbis(silane) 1 which reacts with MCPBA in CH₂Cl₂ at r.t. to

Full text of DOI:10.1016/j.jorganchem.2009.01.030

Journal of Organometallic Chemistry 694 (2009) 1907–1911
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Journal of Organometallic Chemistry
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1,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene: Regioselective ring opening of its
a,b-epoxybis(silane) with some nucleophiles
*
Kazem D. Safa , Khatereh Ghorbanpour, Akbar Hassanpour, Shahin Tofangdarzadeh
Organosilicon Research Laboratory, Faculty of Chemistry, University of Tabriz, 51664 Tabriz, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyllithium, (Me3Si)3-
CLi, in Et2O gives disubstituted vinylbis(silane) 1 which reacts with MCPBA in CH2Cl2 at r.t. to afford mix-
ture of mono and disubstituted epoxybis(silanes) 3 and 2. Vinylbis(silane) 1 can be completely converted
into epoxybis(silane) 2 with an excess amount of MCPBA. The compound 2 was reacted with various
reagents such as HX (X = Cl, Br), H2SO4, LiAlH4 and MeLi/CuI and give the related products.
Ó 2009 Elsevier B.V. All rights reserved.
Received 10 November 2008
Received in revised form 10 January 2009
Accepted 15 January 2009
Available online 22 January 2009
Keywords:
Vinylbis(silane)
Tris(trimethylsilyl)methyllithium
Peterson reaction
a,b-Epoxybis(silane)
Ring opening reaction
1. Introduction
bis(silane) derivative 2 with hydrogen halides, lithium aluminum
hydride, organocuprate and sulfuric acid in methanol.
Vinylsilanes are important synthetic intermediates in stereo-
controlled organic synthesis. Vinylbis(silanes) might be anticipated
to possess broadly similar attributes to vinylsilanes for use in syn-
thesis [1–3]. In contrast to vinylsilanes, however, vinylbis(silanes)
are a relatively unexplored class of materials [4]. Their use as pre-
cursors for the preparation of ketones as well as variety of impor-
tant organosilicon intermediates such as acylsilanes, epoxysilanes,
1-halovinylsilanes, silyl enol ethers, (E)-alkenylsilanes, silyl enol
acetates, etc. stimulates interest in their synthetic availability [5,6].
We have recently reported [7] a convenient and stereoselective
2. Results and discussion
It has been previously shown that 1,4-bis[2,2-bis(trimethyl-
silyl)ethenyl]benzene (1) was prepared from reaction of ethylene
glycol silylation-one-pot deethenative silylative coopling cycliza-
tion/Grignard reagent treatment–Heck coupling [5,8]. The Peterson
olefination, the reaction of an a-silyl organometallic (usually orga-
nolithium) reagent with an aldehyde or ketone to yield an olefin, is
a useful alternative to the Wittig reaction [9,10]. Herein, 1 has been
prepared from Peterson olefination of terephthalaldehyde with
[(trimethylsilyl)methyl]lithium, (Me3Si)3CLi [11], (Scheme 1). This
method of preparing functionalized silanes is limited by the read-
iness with which (Me3Si)3CLi abstracts a proton, if one is available,
rather than attacking at carbon [12].
route for the synthesis of a-silyl-a,b-unsaturated enones from 1,1-
bis(trimethylsilyl)-2-phenylethylene and some acyl chlorides in
the presence of AlCl3. The addition of an electrophile to a vinylsi-
lane results in the build-up of electrophilic character b in the C–
Si bond. A side from electrophilic substitution, one of the synthet-
ically most useful transformations of vinylsilanes is epoxidation
and hydrolysis of the resultant epoxysilanes with acid to reveal a
carbonyl group, in which the carbonyl carbon originally bore the
silyl substituent. Given the utility of acylsilanes in synthesis and
the now readily availability of vinylbis(silanes), then the develop-
ment of a method to convert vinylbis(silanes) into acylsilanes via
epoxybis(silanes) would be of value [4].
Epoxidation of vinylsilanes furnish
a,b-epoxysilanes, a class of
compounds of considerable interest to the organic chemists [13].
The presence of trialkyl group provides regioselective control in
the opening of epoxide by variety of nucleophiles. The compound
1 was reacted with MCPBA in CH2Cl2 at room temperature for 4 h
and gave both mono and disubstituted epoxybis(silanes) 3 and 2.
In order to optimize conditions for the formation of 2, we
decided to investigate the reaction of 1 (1 mmol) with various
amount of MCPBA (Table 1). When 2 mmol of MCPBA was used,
for 18 h, the major product was 2. In the reaction of 1 with
3 mmol of MCPBA the epoxybis(silane) 2 was the sole product
formed.
In this paper, we wish to report the synthesis and the reactivity
of 1,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene (1) and its epoxy-
* Corresponding author. Tel.: +98 411 3393124; fax: +98 411 3340191.
E-mail address: dsafa@tabrizu.ac.ir (K.D. Safa).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.01.030

1908
K.D. Safa et al. / Journal of Organometallic Chemistry 694 (2009) 1907–1911
Me3Si
Me3Si
Me3Si
OLi
OLi
H
SiMe3
SiMe3
SiMe3
Ether
OHC
CHO
2 (Me3Si)3CLi
+
H
-2 Me3SiOLi
Me3Si
Me3Si
SiMe3
SiMe3
HC
CH
(1)
Scheme 1. Preparation of 1,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene via Peterson protocol.
Table 1
Treatment of epoxybis(silane) 2 with MCPBA.
1:MCPBA
1:1a
1:2
1:3
2
3
25.6%
70.4%
92.5%
3.54%
96%
–
a
Yields obtained by PTLC.
Table 2
Yields of the reaction of epoxybis(silane) 4 with HX (X = Cl, Br).
Time/temperature
14 h/r.t.
14 h/reflux
79.5%
17%
86%
9%
–
24 h/reflux
5a
6a
5b
6b
7b
7.5%a
88.5%
5%
20%
70%
96%
trace
83.5%
12%
–
a
Yields calculated by GC–mass spectrometry.
It has been reported [14] that the reaction of epoxybis(silane)
stereoselective. However, this is not the case for the direct addi-
tion/elimination sequences. For example, the condensation of
(Me3Si)2CHLi with benzaldehyde gave a mixture of stereoisomers
(E/Z = 1.4/1) [14].
Halovinylsilanes are useful for the synthesis of geometrically
defined trisubstituted alkenes, and as synthetic equivalents of car-
bonyl anions and cations [4,15]. One method for 1-halovinylsilane
synthesis could be via reaction of epoxybis(silane) with hydrogen
with LiAlH4 gave the b-hydroxybis(silane) without any formation
of vinylsilane by Peterson-type reaction. However, in the case of
epoxybis(silane) 2, Peterson-type olefination was found to take
place after or concurrently with the addition, to give the corre-
sponding vinylsilane 4 stereoselectively (Scheme 2). The extremely
high stereoselectivity of the compound 4 (only trans–trans) is
worth mentioning. It has been well documented that acid or base
catalyzed elimination from isolated b-hydroxysilanes is highly
Me3 Si
I
SiMe 3
I
MeLi/CuI
(2)
HC
CH
Me 3Si
SiMe3
H
LiAlH4/ Ether
(2)
HC
CH
H
(8)
ZZ: EE= 98:2%
(4)
Scheme 2. Reaction of epoxybis(silane) 2 with LiAlH4.
Scheme 3. Treatment of 2 with methylcopper reagent (MeLi/CuI 2:1).

K.D. Safa et al. / Journal of Organometallic Chemistry 694 (2009) 1907–1911
1909
SiMe3
O
SiMe3
O
O
H2SO4/MeOH
Me3Si
CH2
CH2
SiMe3
Me3Si
O
SiMe3
(2)
(10)
H+
MeOH
MeOH
Me3Si
SiMe3
O
SiMe3
SiMe3
Me3Si
HO
SiMe3
OH
-2
MeOSiMe3
HC
CH
H+
-2
+
O
+
H
(9)
H
Scheme 4. The plausible mechanism for the formation of acylsilane 10.
halides. Reaction of epoxybis(silane) 2 with aqueous HX (X = Cl, Br)
in THF at room temperature gave the compounds 5, 6 and 7 with
excellent stereocontrol. It is worth noting that in the case of HCl,
we did not detect the halohydrin 7a. Formation of the E-alkene is
most likely greatly favored due to pronounced differences in
eclipsing intraction between the two possible conformations for
syn elimination [4,16]. The effect of temperature on the reaction
was also examined (Table 2). Heating hydrogen halides with
epoxybis(silane) 2 gave only halovinylsilane 5a for 24 h with excel-
lent control over alkene geometry. However, in the case of hydro-
gen bromide the both 5b and 6b were observed, noting that the
compound 5b was the major product.
disubstituted epoxybis(silane) 2 and 3. Whenever 3-fold the mole
ratio of MCPBA was used, 2 was the sole product formed. We have
also investigated the reaction of epoxybis(silane) 2 with a variety
of nucleophiles. On treatment with acids, the epoxybis(silane) 2 pro-
vides halovinylsilane 5, hybrid of halovinylsilane and halohydrin 6,
halohydrin 7, and acylsilane 10. It is noteworthy that, heating and
prolongation of the reaction time play crucial role in the percentage
of the compounds 5, 6 and 7. Interestingly, reaction of methylcopper
reagent with epoxybis(silane) 2 gave iodovinylsilane 8 .This trans-
formation is quite different from those observed in the literature.
In these reactions all the evidences are consistent with the bis(si-
lyl)-substituted carbon being the site of nucleophilic attack.
Mechanistic studies of halovinylsilane formation from epoxy-
bis(silane), indicate that the preferred site of nucleophilic attack
in epoxybis(silanes) is at the disilyl-substituted carbon. The rea-
4. Experimental
sons for the preference for
are not completely obvious. The
dered and ring opening at the
ditions) might be expected to produce a highly stabilized b-silyl
cation. However, the lack of b-opening, although remarkable, is
perhaps less surprising in view of the relative orientation of the
C–Si bond. Also the b-C–O bond greatly deviates from the parallel
alignment that is favorable for stabilization of a developing posi-
tive b-charge by the silicon initial coordination of the nucleophile
with both silicon and carbon. Coordination of the nucleophile to
a
-opening of the
-position is frequently more hin-
-position (under electrophilic con-
a,b-epoxy silanes
4.1. Solvents and reagents
a
a
The reactions were carried out under dry argon. Solvents were
dried by standard methods. Substrates for the preparation of
tris(trimethylsilyl)methyllithium, viz. Me3SiCl (Merck), Li (Merck),
CHCl3 (Merck), and substrate for the preparation of 1,4-bis[2,2-
bis(trimethyl silyl)ethenyl]benzene, viz. terephthalaldehyde
(Merck) and MCPBA (Acros) were used as received.
4.2. Spectra
silicon followed by 1,2-rearrangement to the
been suggested for the -opening reactions [17].
It has also been reported [18] that reaction of
a
-carbon has also
The 1H NMR and 13C NMR were recorded with a Bruker FT-
400 MHz spectrometer at room temperature and CDCl3 as a sol-
vent. The mass spectra were obtained with a GC–mass Agilent,
quadrupole mode 5973 N instrument, operating at 70 eV. The FTIR
spectra were recorded on a Bruker-Tensor 270 spectrometer. Ele-
mental analyses were carried out with an elementar vario EL III
instrument.
a
a,b-epoxysilanes
with organocuprate reagents result in regiospecific opening of the
epoxide ring to form b-hydroxyalkylsilanes. Surprisingly, in the
reaction of epoxybis(silane) 2 with methylcopper reagent (MeLi/
CuI 2:1), the iodovinylsilane 8 was the major product (Scheme
3). This is in contrast to the results of
a,b-epoxysilanes with
organocuprate reagents [18]. FT-IR, NMR (1H and 13C), and mass
spectrometry data has confirmed the formation of the iodovinylsi-
lane 8 [8]. The scope and mechanisms of this reaction are under
investigation.
4.3. Synthesis of products 1–10
4.3.1. Preparation of 1,4-bis[1,1-bis(trimethylsilyl)ethenyl]benzene (1)
Tris(trimethylsilyl)methyllithium (50 mmol) and terephtalalde-
hyde 3.4 g (25 mmol) in ether (30 cm3) was refluxed for 18 h, and
then poured into water and extracted into ether. The organic layer
was washed with water and dried (MgSO4). The solvent was evap-
orated to give a semi-liquid which was crystallized on ethanol to
give 69% white crystal 1. (m.p. 95 °C). FTIR (KBr, cmÀ1): 3119 (CH
vinyl), 3062 (Ar), 2954 (CH), 1640–1403 (C@C, Ar), 1249, 921 and
837 (C–Si); 1H NMR (400 MHz, CDCl3): d 0.00 and 0.20 (s, 18H,
SiMe3), 7.13 (s, 4H, Ar), 7.73 (s, 2H, vinyl); 13C NMR (CDCl3): d
À0.45 and 1.20 (SiMe3), 126.3–140.3 (Ar), 145.2 and 153.6
(C@C); m/z (EI): 418 (24%, [M]+), 217 (23%), 171 (26%,
[CH@C(SiMe2)]+), 73 (100%, [SiMe3]+). Anal. Calc. for C22H42Si4: C,
63.0; H, 10.0. Found: C, 62.8; H, 9.8%.
Epoxybis(silane) 2 was treated with H2SO4 (Conc.) in MeOH at
room temperature and converted to the related acylsilane 10. This
reaction may proceed [19] by the protonation of the oxygen of
epoxide, followed by a nucleophilic attack of MeOH on a trimeth-
ylsilyl group, inducing the trimethylsilylmethyl ether elimination,
and generating the corresponding a-silyl enol 9. a-Silyl enol 9 then
converts to the related acylsilane 10 (Scheme 4).
3. Conclusion
We demonstrated the convenient one-pot preparation of 1,4-
bis[2,2-bis(trimethylsilyl)ethenyl]benzene (1) via Peterson proto-
col. Treatment of 1 with MCPBA affords the mixture of mono and

1910
K.D. Safa et al. / Journal of Organometallic Chemistry 694 (2009) 1907–1911
4.3.2. Typical procedure for the preparation of epoxybis(silanes) (2)
A mixture of vinylbis(silane) 1 (4 g, 9.6 mmol), MCPBA (75% w/
w pure) and CH2Cl2 (150 cm3) was stirred at room temperature for
18 h. The reaction was washed with aq. NaHCO3 (5 Â 80 cm3),
water (80 cm3), brine (80 cm3) and dried (MgSO4). The solvent
was evaporated and the residue was purified by column chroma-
tography (2:3 n-hexane:CH2Cl2) to give a white solid, epoxy-
bis(silane) 2 (Rf = 0.57, m.p. 99–100 °C). FTIR (KBr, cmÀ1): 2957
(CH), 1516–1408 (Ar), 1254 (C–Si), 1177 (C–O), 934 and 844 (C–
Si); 1H NMR (400 MHz, CDCl3): d À0.19 and 0.14 (s, 18 H, SiMe3),
4.10 (s, 2H, HC–O), 7.28 (d, 4H, J = 1.59 Hz, Ar); 13C NMR (CDCl3):
d À3.1 and À1.3 (SiMe3), 54.4 and 6o.4 (C–O), 125.2, 136.4 and
139.4 (Ar); Anal. Calc. for C22H42Si4O2: C, 58.6; H, 9.0. Found: C,
58.5; H, 8.6%.
(CDCl3): d À3.2 (SiMe3), 66.9 (C–Cl), 128.3–137.4 (C@C, Ar); m/z
(EI): 347 (6%, [M+4]+), 345 (18%, [M+2]+), 343 (24%, [M]+), 342
(84%, [MÀ1]+), 183 (11%), 95 (76%), 73 (100%, [SiMe3]+). Anal. Calc.
for C16H24Si2Cl2: C, 55.9; H, 6.9. Found: C, 55.9; H, 6.5%.
6a: (Rf = 0.68 2:3 n-hexane:CH2Cl2, m.p. 116–118 °C), FTIR (KBr,
cmÀ1): 3512 (OH), 3102 (CH vinyl), 3047 (Ar), 2957 (CH), 1645
(C@C), 1609–1411 (Ar), 1250 (C–Si), 1033 (C–O), 927 and 837
(C–Si); 1H NMR (400 MHz, CDCl3): d 0.02, 0.14 and 0.26 (s, 9H,
SiMe3), 2.24 (s, 1H, OH), 5.07 (s, 1H, HC–OH), 6.84 (s, 1H, vinyl),
7.53 (d, 2H, J = 8.37 Hz, Ar), 7.69 (d, 2H, J = 8.36 Hz, Ar); 13C NMR
(CDCl3): d À3.2, À1.0 and À0.8 (SiMe3), 55.8 (C–Cl), 77.8 (C–OH),
126.6–141.0 (C@C, Ar). Anal. Calc. for C19H34Si3Cl2O: C, 52.6; H,
7.2. Found: C, 52.7; H, 6.9%.
4.3.7. Analytical data for 5b, 6b and 7b
4.3.3. Analytical data for previously described mono-substituted
epoxybis(silane) 3
5b: (Rf = 0.93 2:3 n-hexane:CH2Cl2, m.p. 75–77 °C), FTIR (KBr,
cmÀ1): 3084 (CH vinyl), 3025 (Ar), 2957 (CH), 1636–1406 (C@C,
Ar), 1247, 901 and 840 (C–Si); 1H NMR (400 MHz, CDCl3): d 0.28
(s, 18H, SiMe3), 7.20 (s, 2H, vinyl), 7.72 (s, 4H, Ar); 13C NMR
(CDCl3): d À2.8 (SiMe3), 53.8 (C–Br), 127.9–136.7 (C@C, Ar); m/z
(EI): 436 (9%, [M+4]+), 434 (36%, [M+2]+), 433 (9%, [MÀ1]+), 432
(64%, [M]+), 183 (11%), 139 (45%), 73 (100%, [SiMe3]+). Anal. Calc.
for C16H24Si2Br2: C, 44.4; H, 5.5. Found: C, 44.5; H, 5.5%.
6b: (Rf = 0.59 2:3 n-hexane:CH2Cl2, m.p. 94–96 °C), FTIR (KBr,
cmÀ1): 3472 (OH), 3045 (CH vinyl), 3024 (Ar), 2955 (CH), 1628–
1411 (C@C, Ar), 1249 (C–Si), 1032 (C–O), 955 and 837 (C–Si); 1H
NMR (400 MHz, CDCl3): d 0.13, 0.19 and 0.31 (s, 9H, SiMe3), 2.33
(d, 1H, J = 4.77 Hz, OH), 5.15 (d, 1H, J = 4.66 Hz, HC–OH), 7.25–
7.69 (m, 5H, vinyl and Ar); 13C NMR (CDCl3): d À2.8, À0.1 and
0.1 (SiMe3), 53.8 (C–Br), 77.4 (C–OH), 126.7–141.1 (C@C, Ar). Anal.
Calc. for C19H34Si3Br2O: C, 45.0; H, 5.7. Found: C, 44.7; H, 5.4%.
7b: (Rf = 0.17 2:3 n-hexane:CH2Cl2), m.p. 69–70 °C), FTIR (KBr,
cmÀ1): 3524 (OH), 3031 (Ar), 2954 (CH), 1635–1409 (Ar), 1249
(C–Si), 1038 (C–O), 964 and 839 (C–Si); 1H NMR (400 MHz, CDCl3):
d 0.10 and 0.16 (s, 18H, SiMe3), 1.86 (s, 2H, OH), 5.20 (d, 2H,
J = 1.06 Hz, HC–OH), 7.54 (s, 4H, Ar); 13C NMR (CDCl3): d 0.0 and
0.3 (SiMe3), 53.9 (C–Br), 77.4 (C–OH), 126.7–141.2 (Ar). Anal. Calc.
for C22H44Si4Br2O2: C, 43.2; H, 7.2. Found: C, 43.6; H, 7.2%.
Purification by column chromatography (2:3 n-hexane:CH2Cl2)
gave a white solid epoxybis(silane) 3 (Rf = 0.83, m.p.78–79 °C). FTIR
(KBr, cmÀ1): 3032 (CH vinyl), 2959 (C–H), 1617–1402 (C@C, Ar),
1253 (C–Si), 1096 (C–O), 938 and 838 (C–Si); 1H NMR (400 MHz,
CDCl3): d À0.17, À0.01, 0.15 and 0.18(s, 9H, SiMe3), 4.16 (s, 1H,
HC–O), 7.10 (d, 2H, J = 7.98 Hz, Ar), 7.20 (d, 2H, J = 8.09 Hz, Ar),
7.71(s, 1H, vinyl); 13C NMR (CDCl3): d À3.0, À1.2, À0.4 and 1.2
(SiMe3), 54.4 and 60.5 (C–O), 125.1–142.2 (Ar), 145.2 and 153.5
(C@C); Anal. Calc. for C22H24Si4O: C, 58.7; H, 9.4. Found: C, 58.3;
H, 9.0%.
4.3.4. Reaction of epoxybis(silane) 2 with LiAlH4
To 305 mg (8.04 mmol) of LiAlH4 in 50 cm3 of anhydrous ether
cooled in an ice bath was added 400 mg (0.96 mmol) of epoxy-
bis(silane) 2, and the reaction mixture was allowed to warm to
room temperature with stirring for 150 min. The mixture was
cooled in N2/ethyl acetate bath (À78 °C), and cold aqueous NaHCO3
was added dropwise, and was allowed to warm to room tempera-
ture. Ether was added, the layers were separated, and the aqueous
layer was extracted with ether (2 Â 30 cm3). The combined organic
layers were dried (MgSO4) and the solvent was evaporated and the
residue separated by preparative TLC on silica gel (4:1 n-hex-
ane:Et2O) to give 67.5% white solid 4 (Rf = 0.43, m.p. 52–54 °C).
FTIR (KBr, cmÀ1): 3070 (CH vinyl), 3038 (Ar), 2925 (CH), 1647
(C@C), 1601–1405 (Ar), 1246, 987 and 845 (C–Si); 1H NMR
4.3.8. Reaction of eppoxybis(silane) 2 with MeLi/CuI
To a mixture of 1.7 g (17.95 mmol) of CuI in 15 cm3 of anhy-
drous ether at -45 °C was added 17.95 mmol of methyllithium
[1.12 cm3 (17.95 mmol) MeI in 5 cm3 anhydrous ether was added
dropwise into 250 mg (35.9 mmol) Li in 15 cm3 anhydrous ether]
dropwise. The resulting reaction mixture was stirred for 1 h at
À45 °C. Then a solution of 500 mg (1.1 mmol) of epoxybis(silane)
2 in 10 cm3 of anhydrous ether was added dropwise and the result-
ing mixture was stirred [2 h at À45 °C, 23 h (À45 °C ? r.t.)]. Then
50 cm3 of saturated NaHCO3 was poured into the reaction mixture,
the layers were separated, the aqueous layer was extracted three
times with ether, and then the combined organic layers were
washed with saturated NaHCO3 followed by water, dried (MgSO4),
and concentrated. The residue was separated by TLC on silica gel
(n-hexane) to give 69.36% white solid 8 (Rf = 0.39, m.p. 118–
120 °C). FTIR (KBr, cmÀ1): 3065 (CH vinyl), 3021 (Ar), 2954 (CH),
1664 (C@C), 1626–1399 (Ar), 1244, 906 and 837 (C–Si); 1H NMR
(400 MHz, CDCl3): d 0.27 (s, 18H, SiMe3), 7.27 (s, 2H, vinyl), 7.62
(s, 4H, Ar); 13C NMR (CDCl3): d À2.3 (SiMe3), 110.9 (C–I), 127.2–
142.7 (C@C, Ar); m/z (EI): 526 (67%, [M]+), 185 (30%), 73 (100%,
[SiMe3]+). Anal. Calc. for C16H24Si2I2: C, 38.5; H, 6.6. Found: C,
38.1; H, 6.6%.
(400 MHz, CDCl3):
d
À0.15 (s, 18H, SiMe3), 6.47 (d, 2H,
J = 19.13 Hz, vinyl), 6.85 (d, 2H, J = 19.13 Hz, vinyl), 7.39 (s, 4H,
Ar); 13C NMR (CDCl3): d À2.2 (SiMe3), 125.5–142.1 (C@C, Ar); m/z
(EI): 274 (30%, [M]+), 259 (23%, [M–Me]+), 201 (10%, [M–SiMe3]+),
187(70%), 147(30%), 99 (8%, [HC@CHSiMe3]+), 73 (100%, [SiMe3]+).
Anal. Calc. for C16H26Si2: C, 70.0; H, 9.0. Found: C, 69.7; H, 8.7%.
4.3.5. General procedure for the preparation of 5, 6 and 7
A
mixture of epoxybis(silane) 2 (500 mg, 1.1 mmol), HX
(2 mol dmÀ3; 5 cm3) and THF (20 cm3) was stirred at 70 °C. After
14 h the reaction mixture was cooled, Et2O (30 cm3) was then
added and the mixture was washed with saturated aq. Na2CO3
(2 Â 30 cm3), aq. Na2S2O3 (1 mol dmÀ3; 30 cm3), water (30 cm3)
and brine (30 cm3). The organic layer was dried (MgSO4) and evap-
orated to give a residue which was purified by TLC (silica gel) (2:3
n-hexane:CH2Cl2) to give white solids 5 and 6.
(As explained in the text, at room temperature 5, 6 and 7b were
obtained).
4.3.6. Analytical data for 5a and 6a
5a: (Rf = 0.93 2:3 n-hexane:CH2Cl2, m.p.78–80 °C), FTIR (KBr,
cmÀ1): 3130 (CH vinyl), 3087 (Ar), 2956 (CH), 1635–1406 (C@C,
Ar), 1246, 921 and 837 (C–Si); 1H NMR (400 MHz, CDCl3): d 0.27
(s, 18H, SiMe3), 6.84 (s, 2H, vinyl), 7.73 (s, 4H, Ar); 13C NMR
4.3.9. Preparation of acylsilane 10
Concentrated H2SO4 (18 mol dmÀ3; 0.19 cm3, 3.4 mmol) was
added dropwise to
a stirred solution of epoxybis(silane) 2
(400 mg, 0.96 mmol) in MeOH (6 cm3) at 25 °C. After 90 min at re-

K.D. Safa et al. / Journal of Organometallic Chemistry 694 (2009) 1907–1911
1911
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flux condition, the mixture of the reaction was cooled and satu-
rated aq. NaHCO3 (30 cm3) was added to the reaction mixture
and the residue was extracted with Et2O (3 Â 30 cm3). The com-
bined organic layers were washed successively with water
(30 cm3) and brine (30 cm3), dried (MgSO4) and evaporated. Purifi-
cation of the residue by TLC on silica gel (1:1 n-hexane:ether) gave
a yellow oil, 40% yield, the acylsilane 10 (Rf = 0.43). FTIR (KBr,
cmÀ1): 3032 (Ar), 2957 (CH), 1705 (CO), 1607–1418 (Ar), 1254
and 844 (C–Si); 1H NMR (400 MHz, CDCl3): d 0.10 (s, 18H, SiMe3),
3.80 (s, 4H, CH2), 7.20 (m, 4H, Ar); m/z (EI): 307 (100%, [M+1]+),
233 (3%, [MÀSiMe3]+), 207 (6%), 73 (15%, [SiMe3]+).
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