Synthesis of 2-methylidene-1-silacyclohexanes by intramolecular hydrosilylation

Article abstract of DOI:10.1016/j.jorganchem.2008.03.007

The preparation of various (hex-5-ynyl)silanes was achieved following two different synthetic approaches from readily available materials such as 4-bromobutene, 6-iodohexyne and chlorosilanes. Different reaction conditions for intramolecular hydrosilylation were tested to prepare the corresponding 2-methylidene-1-silacyclohexanes. Notably, the use of Speier's catalyst allowed the regioselective formation of the desired products in moderate yields.

Full text of DOI:10.1016/j.jorganchem.2008.03.007

Journal of Organometallic Chemistry 693 (2008) 2033–2040
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Journal of Organometallic Chemistry
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Synthesis of 2-methylidene-1-silacyclohexanes by intramolecular hydrosilylation
*
*
Silvia Díez-González , Luis Blanco
Laboratoire de Synthèse Organique et Méthodologie, Institut de Chimie Moléculaire et des Matériaux d’Orsay, UMR 8182 (Associé au CNRS), Bât. 420,
Univerité de Paris Sud, 91405 Orsay, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The preparation of various (hex-5-ynyl)silanes was achieved following two different synthetic
approaches from readily available materials such as 4-bromobutene, 6-iodohexyne and chlorosilanes.
Different reaction conditions for intramolecular hydrosilylation were tested to prepare the corresponding
2-methylidene-1-silacyclohexanes. Notably, the use of Speier’s catalyst allowed the regioselective forma-
tion of the desired products in moderate yields.
Received 13 February 2008
Received in revised form 5 March 2008
Accepted 5 March 2008
Available online 18 March 2008
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Alkyne
Cyclization
Hydrosilylation
Platinum
Vinylsilane
1. Introduction
the complete selectivity of this reaction, the formation of dimers
and oligomers considerably lowers the yield of the desired
The unique properties of silicon [1] have led to its wide
utilization in organic chemistry as protective group [2], tempo-
rary tether [3] or in the Peterson reaction [4], Sakurai reaction
[5] and Tamao oxidation [6]. The hydrosilylation of alkenes
and alkynes is one of the most powerful methods for the forma-
tion of Si–C bonds [7]. The intramolecular version of this reac-
tion is an elegant approach to the synthesis of silacycles. Even
though few examples of intramolecular hydrosilylation of al-
kynes have been reported, it is commonly acknowledged that
it can lead to the formation of three different types of silacycles
according to the cyclization mode (endo or exo) and the regiose-
lectivity of the addition of the Si–H bond (trans or cis): endo-
trans, exo-trans or exo-cis. To date, no example of endo-cis intra-
molecular hydrosilylation is known. The selectivity of this reac-
tion depends on the nature of the alkynyl chain and on the
catalytic system.
product. The same cyclization mode has been observed from silyl
ether derivatives of homopropargylic alcohols to yield methylid-
eneoxasilacyclopentanes [9]. In these examples, the platinum-
catalyzed reaction of disubstituted alkynes generates vinylsilanes
of defined E configuration, which is in accordance with the
commonly accepted Chalk–Harrod mechanism [10]. The forma-
tion of Z-vinylsilanes by ruthenium-catalyzed intramolecular
hydrosilylation has been recently reported [11]. However,
cationic ruthenium-based systems yielded endo-trans products
which can be rationalized with a new mechanistic pathway
involving the formation of a ruthenacyclopropene intermediate
[12]. The same trans addition of a hydrosilane onto a substituted
carbon–carbon triple bond has been reported in Lewis acid-
catalyzed intramolecular hydrosilylation [13], but in this case
the alkynyl chain length was shown to govern the cyclization
mode.
In the case of platinum-catalyzed intramolecular hydrosilyla-
tion, the cis addition of hydrosilanes on the triple bond is usually
observed. For instance, the reaction of a (pent-4-ynyl)silane in
the presence of hexachloroplatinic acid (Speier’s catalyst) leads
to the formation of a methylidenesilacyclopentane resulting of
an exo-cis cyclization as the only cyclic product [8]. Despite
We were interested in the preparation of 2-methylidene-1-sila-
cyclohexanes because the synthesis of such vinylsilanes is still
challenging despite numerous publications concerning the forma-
tion of silacycles [14]. To the best of our knowledge, prior to our
recent report about the preparation of this type of silacyclohexanes
from di- or trihalosilanes and a dibromohexene [15], the only re-
ported unsubstituted 2-methylidene-1-silacyclohexane had been
prepared by a Wittig reaction with a 2-silacyclohexan-1-one [16].
Herein, we report the preparation of (hex-5-ynyl)silanes by two re-
lated synthetic approaches and their subsequent intramolecular
hydrosilylation to yield a number of 2-methylidene-1-silacyclo-
hexanes (Scheme 1).
* Corresponding authors. Present address: Institute of Chemical Research of
Catalonia (ICIQ), Av. Països Catalans, 16, 43007 Tarragona, Spain (S. Díez-González).
E-mail addresses: sdiez@iciq.es (S. Díez-González), lublanco@icmo.u-psud.fr
(L. Blanco).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.03.007

2034
S. Díez-González, L. Blanco / Journal of Organometallic Chemistry 693 (2008) 2033–2040
R
Cl
H
Me
Cl
H
+
Si
+
Si
Br
R
R'
Cl
R'
R
Si
Si
Si
R'
H
H2PtCl6
Cyclohexane, rfx
X
Br
Br
R
Me
Cl
Si
R'
Cl
6
92%
Cl
1) (Hex)MgBr, THF, RT
2) LiAlH4, Et2O, rfx
R
H
+
Si
Br
R'
Cl
Br
7
31.5%
Me
Scheme 1. Retrosynthetic approaches for the preparation of 2-methylidene-1-
silacyclohexanes.
Si
Hex
H
Scheme 3. Preparation of (4-bromobutyl)silane (7).
2. Results and discussion
magnesium bromide in THF followed by an in situ reduction with
LiAlH4 (Scheme 3).
2.1. Preparation of (hex-5-ynyl)hydrosilanes
Next, we carried out the substitution reaction of the bromine
atom by an ethynyl group. The conditions previously reported for
the substitution of an iodine atom (1.3 equiv. of ethynyllithium/
ethylenediamine in DMSO at room temperature for 2 h) [8] led to
the formation of the expected alkyne in low yield due to a low con-
version (Table 1, entry 1). Optimization studies on this reaction for
our system showed that yields could be improved with longer
reaction times or by using larger excess of the lithium complex
(Table 1, entries 2 and 3). On the contrary, some degradation prod-
ucts were detected when the reaction temperature was raised to
50 °C (Table 1, entry 4). Finally, the best results were obtained in
THF using hexamethylphosphorous triamide (HMPA) as additive
(Table 1, entries 5 and 7). The reaction time was optimized to 2 h
at room temperature in order to avoid any undesirable decomposition
(Table 1, entries 5 and 6).
Surprisingly, these optimized conditions for the synthesis of 8
did not allow us to obtain the hexynylsilanes 9 and 10 (Scheme
4). From methylphenylsilane 4, a complex mixture was obtained
and only the disubstituted product 11 could be partially identified
[18]. In this particular case, the hydrogen atom on the silicon cen-
ter is in a pseudo-benzylic position, which may explain its higher
reactivity. On the other hand, reaction of the dimethylsilane 5 un-
der the same conditions led to the formation of degradation prod-
In order to test the intramolecular hydrosilylation of alkynes, a
number of (hex-5-ynyl)hydrosilanes were synthesized. Our initial
efforts were focused on a similar approach to the one reported
for the preparation of (pent-4-ynyl)hydrosilanes [8]. The plati-
num-catalyzed hydrosilylation of 4-bromobutene by chlorometh-
ylphenylsilane
1 [17] or chlorodimethylsilane in refluxing
cyclohexane led to the formation of the corresponding (4-bromo-
butyl)chlorosilanes 2 and 3 in excellent yields after distillation
(Scheme 2). The subsequent substitution of the chlorine on the sil-
icon atom by a hydride was achieved after treatment with LiAlH4
(Scheme 2). No significant reduction of the alkyl chain was ob-
served under these reaction conditions. Noteworthy, even though
the formation of the chlorosilanes 2 and 3 is extremely clean, they
must be distilled before being engaged in the next step; otherwise
total decomposition, with liberation of a gas (probably dihydrogen)
is observed during the concentration of 4 and 5. We believe that
despite the work-up of the reduction reaction, remaining traces
of platinum species might catalyze this decomposition reaction.
A similar approach was employed for the preparation of (4-bro-
mobutyl)hexylsilane 7. The hydrosilylation of 4-bromobutene by
dichloromethylsilane, under the conditions described above, led
to the formation of (4-bromobutyl)silane 6 in high yield (Scheme
3). The hexylsilane 7 was obtained after reaction of 6 with hexyl-
ucts. These experiments clearly show how such
a simple
modification in the nature of the substituents on the silicon atom
can dramatically change the reactivity of the molecule.
These results led us to exchange the bromine by an iodine on
silanes 4 and 5 prior to the reaction with the ethynyllithium
Me
R
H
+
Br
Si
Cl
R = Ph
1
H2PtCl6
Cyclohexane, rfx
Table 1
Optimization studies for the preparation of (hex-5-ynyl)silane 8
Br
Br
Li/EDA
R = Ph
R = Me
2
3
92%
97%
Me
Me
Me
R
Si
Si
Si
3
Hex
H
Hex
H
Cl
Solvent, T
7
8
Entry
Solvent
Equivalent [Li]
T (°C)
Time (h)
Yield (%)
LiAlH4
Et2O, rfx
1
2
3
4
5
6
7
DMSO
DMSO
DMSO
DMSO
THF/HMPA
THF/HMPA
THF/HMPA
1.3
2.2
2.2
2.2
2.2
2.2
2.2
20
20
20
50
20
20
À10
2
3
5
5
2
4
7
36
46
60
53
78
37
74
Br
R = Ph
R = Me
4
5
87%
83%
Me
R
Si
H
Scheme 2. Preparation of (4-bromobutyl)silanes 4 and 5.

S. Díez-González, L. Blanco / Journal of Organometallic Chemistry 693 (2008) 2033–2040
2035
Br
Me
Y
Cl
H
Me
R
+
Si
Si
I
H
R = Ph
R = Me
4
5
Mg*,THF, 40˚C
Li/EDA
THF/HMPA, RT
Me
Y
Si
H
R = Ph
Me
Y = Ph
9
10
14
35%
26%
64%
Me
Si
R
Y = Me
Y = Cl
Si
3
3
H
Ph
11
R = Ph
9
Scheme 6. Preparation of (hex-5-ynyl)silanes under Barbier-type conditions.
R = Me 10
Scheme 4. Attempts of preparation of (hex-5-ynyl)silanes 9 and 10.
A last precursor for the intramolecular hydrosilylation was pre-
pared from the chlorosilane 14 by reaction with allylmagnesium
chloride at room temperature (Scheme 7). The isolated yield in all-
ylsilane 15 after purification, even if moderate, seems acceptable
for this kind of substrate.
(Scheme 5). In this case, the expected hexynylsilanes could be iso-
lated with similar yields to the ones reported in the synthesis of
(pent-4-ynyl)silanes [8].
Our alternative approach for the synthesis of (hex-5-ynyl)si-
lanes relies on the one-pot reaction of an halohexyne with a chlo-
rosilane in the presence of activated magnesium (Barbier-type
conditions) [19]. For this transformation, the protection of the ter-
minal triple bond was not necessary, but the reaction temperature
must be carefully controlled at 40 °C in order to avoid undesired
carbometallation reactions. Under these conditions, hexynylsilanes
9 and 10 could be successfully synthesized in moderate yields.
Moreover, chloro(hexynyl)silane 14, which would be difficult to
prepare by the first approach, was also prepared in good yield
(Scheme 6).
Besides the possibility of carbometallated by-products forma-
tion, the main difficulty of this reaction is that it takes place in
the presence of two different types of acidic protons, acetylenic
and propargylic. Alternatively, organozinc and organocuprate re-
agents are commonly known for their weakly ionic carbon–metal
bonds, therefore acidic protons are well tolerated in their presence
2.2. Preparation of 2-methylidene-1-silacyclohexanes
To access the 2-methylidene-1-silacyclohexanes, we tested the
intramolecular hydrosilylation of the corresponding (hex-5-ynyl)-
silanes in the presence of hexachloroplatinic acid in refluxing
cyclohexane. Of note, these reactions were carried out in air after
we observed that an inert atmosphere inhibited the cyclization
process. In fact, in some platinum-catalyzed hydrosilylation reac-
tions, it has been postulated that the oxygen acts as a co-catalyst
[23]. It is believed that the presence of oxygen prevents the irre-
versible agglomeration of colloidal-platinum particles formed from
the catalyst and its coordination to the intermediate species, mak-
ing them more reactive towards the unsaturation.
After slow addition of a solution of the starting material over a
refluxing suspension of the catalyst (final concentration =
0.025 M), the reaction mixture was quickly filtered over silica gel
in order to separate the platinum species and avoid the total oli-
gomerization of the formed methylidenesilacyclohexanes during
the concentration step. Results obtained under these conditions
are presented in Table 2. A good yield was obtained for the silane
16 bearing an hexyl chain on the silicon atom. For silanes 17 and
20, the spectroscopic data were identical to the products obtained
from a dibromohexene and dihalosilanes [15]. Even though an
important formation of oligomers was detected by GC, it is worth
noting that the formation of silacycloheptenes, resulting of an endo
cyclization, was never detected.
[20]. The preparation of organozinc iodides, followed by
a
transmetallation with CuCNÁ2LiCl leads to the formation of
RCu(CN)ZnI-type reagents which can react with diverse organic
electrophiles [21]. We attempted the synthesis of this type of re-
agent from 6-iodohexyne and used dichloromethylsilane as elec-
trophile. After the addition of the copper salt, the reaction
mixture turned red, implying the formation of the desired organo-
cuprate intermediate. However, the 1H NMR spectrum of the reac-
tion mixture did not show any signal attributable to the desired
product 14. After distillation of the crude, the 1H NMR of the iso-
lated fraction was in accordance with the major formation of
carbometallated products [22].
Dimethylsilacyclohexane 18 (Table 2, entry 3) proved to be
unstable on silica gel and when its purification was attempted by
vacuum distillation only decomposition products were obtained.
The crude silane 18 could be characterized however by 1H NMR
and LRMS [24]. Remarkably, the allylsilane 15 yielded some cyclic
product albeit in low yield (Table 2, entry 5). In this case, a lower
reaction temperature (70 °C) and a higher dilution (0.007 M) were
required to avoid the complete oligomerization of the species in
the reaction mixture.
NaI
I
Br
Me
R
Me
R
Si
Si
3
3
H
H
H
Butanone, rfx
4
5
R = Ph
R = Me
89%
12
13
69%
Li/EDA
Me
R
MgCl
Me
12 or 13
Si
3
DMSO, RT
Si
14
3
H
THF, RT
34%
R = Ph
R = Me
32%
16%
9
15
10
Scheme 5. Preparation of (hex-5-ynyl)silanes 9 and 10.
Scheme 7. Preparation of allyl(hex-5-ynyl)silane 15.

2036
S. Díez-González, L. Blanco / Journal of Organometallic Chemistry 693 (2008) 2033–2040
Table 2
3. Conclusions
Platinum-catalyzed intramolecular hydrosilylation of (hex-5-ynyl)silanes
H
We have prepared a series of (hex-5-ynyl)silanes using two dif-
ferent approaches. The reaction of chlorohydrosilanes and 6-iodo-
Y
H2PtCl6 (8.10-3 mol %)
Cyclohexane, reflux
Y
Si
Si
Me
Me
hexyne with activated magnesium represents
a direct and
convenient strategy for the preparation of this family of products.
On the other hand, the synthetic approach from chlorohydrosilanes
and a bromobutene remains interesting since it highlights the
great influence of the substitution on the silicon atom on the reac-
tivity of the molecule.
Different catalytic systems have been studied for the intramo-
lecular hydrosilylation of these (hex-5-ynyl)silanes. The best re-
sults were achieved in the presence of Speier’s catalyst, with
which the cyclization takes place in a complete selective exo-cis
manner. The reported moderate yields can be rationalized by the
fact that the starting material and the expected product can lead
to the significant formation of oligomers under the reaction condi-
tions. Taking into account the few rare reports in the literature
concerning the synthesis of exo-cyclic vinylsilanes, the simplicity
of this strategy is remarkable.
It is important to note that this methodology is complementary
to our previous work in which 2-methylidene-1-silacyclohexanes
were prepared from a dibromohexene and halosilanes under Grig-
nard or Barbier-type conditions. We hope that the present hydro-
silylation-based approach will find an extention to the
diastereoselective synthesis of more complex cyclic products. The
study of the potential reactivity of these 2-methylidene-1-silacy-
clohexanes is currently ongoing in our laboratories.
Entry
Y
SM
Product
Yield (%)
1
2
3
4
5
Hexyl
Ph
Me
Cl
Allyl
8
9
10
14
15
16
17
18
19
20
66
42
Not isolateda
0
18b
a
Reaction in refluxing pentane.
Reaction at 70 °C with a final concentration of 0.007 M.
b
On the other hand, the 1H NMR of the crude product obtained
from chlorosilane 14 showed the complete consumption of this
starting material as well as the appearance of two doublets at
5.23 and 5.48 ppm which suggest formation of a cyclic product.
However, no singlet assignable to a methyl group bound to a chlo-
rosilane was observed. We were aware of the instability of 2-
methylidenesilacyclohexanes under the reaction conditions [25],
but in this case a filtration over silica gel was not possible. At-
tempts of separation by vacuum evaporation, even extremely fast,
only led to the recovery of complex mixture of oligomerization
products. It is probable that the higher reactivity of 14 and/or 19
eases their oligomerization while in the reaction mixture.
We tried to overcome this difficulty by testing the initiation of
the hydrosilylation of 14 with benzoyl peroxide [26]. However,
the reaction, after 15 h in refluxing cyclohexane, resulted princi-
pally in the recovery of the starting material.
4. Experimental
4.1. General considerations
Along with Speier’s catalyst, Wilkinson’s catalyst, [(Ph3P)3RhCl],
is one of the most commonly used catalyst for the hydrosilylation
reaction. The intermolecular hydrosilylation of 1-alkynes catalyzed
by this rhodium complex has been reported to lead to the formation
of cis-1-silylalkenes in good yields [27]. In this case, the trans addi-
tion observed is surprising as it is generally accepted that transition
metal complexes promote cis addition of hydrosilanes on triple
bonds. In the present case, the rhodium-catalyzed cyclization of
the silane 9 led to the formation of a mixture 80/20 of methylid-
enesilacyclohexane 17 and 3-silacyclohept-1-ene (21) (Scheme 8)
[28]. Similar results were observed when cyclohexane was replaced
by benzene. However, as it had already been reported in the pres-
ence of this catalyst [29], the main products of this reaction are olig-
omers which explains the extremely low yield in cyclic products.
Finally, we studied the Lewis acid-catalyzed hydrosilylation of
one of our substrates. While no reaction was observed with (hex-
5-ynyl)silane 9 in the presence of AlCl3, the major formation of
oligomers was observed when a solution of EtAlCl2 was used. After
purification by flash chromatography, 26% of the starting material
was recovered along with 3% of a silanol resulting from the hydro-
lysis of the Si–H bond in 9 [30]. This result indicates that the use of
a disubstituted silaalkyne might be necessary in order to form a
cyclic product [19].
All reactions were carried out in dry glassware under an argon
atmosphere unless otherwise indicated. All commercially available
chemicals were used as received. 4-Bromobut-1-ene [31] and 6-
iodohex-1-yne [32] were synthesized according to the literature
procedures. Hexachloroplatinic acid and sodium iodide were kept
in presence of P2O5 at atmospheric pressure. Solvents were dis-
tilled from appropriate drying agents. Column chromatography
was performed on silica gel SDS (70–200 lm). 1H NMR and 13C
NMR were recorded on Bruker spectrometers at room temperature.
Chemical shifts (d) are reported with respect to tetramethylsilane
as internal standard in ppm. Assignments of some 1H and 13C
NMR signals rely on COSY, HSQC (or HMBC), DEPT and/or TOCSY
experiments on a DRX 400 spectrometer. The infrared spectra were
performed on a FT-IR Spectrum One spectrometer. All of them
were made on a film of pure product placed in between two so-
dium chloride pellets. The low-resolution mass spectra in elec-
tronic impact were registered on
a Nermag R10-10-type
spectrometer coupled to an OKI DP125 chromatographer. The
high-resolution mass spectra were made on a Finnigan MAT 95 S
spectrometer (precision: 5/1000e). The elemental analyses were
performed by the elemental analysis service of the Institut de Chi-
mie des Substance Naturelles de Gif-sur-Yvette (France).
4.2. Chloromethylphenylsilane (1)
Ph
Ph
[(Ph3P)3RhCl]
Solvent, rfx
Me
R
Si
Si
In a round-bottom-flask, 4 mL (29.1 mmol) of methylphenylsi-
lane were added over 8.04 g (59.8 mmol) of anhydrous CuCl2 and
0.17 g (0.9 mmol) of CuI. After 5 h of stirring under a regular lamp,
the reaction mixture was washed with dry pentane and filtered un-
der argon. Concentration of the filtrate, followed by vacuum distil-
lation, afforded 4.20 g of chloromethylphenylsilane 1 as a colorless
oil (92%). B.p. 56 °C/5 mm Hg. Spectroscopic data were in accor-
dance with a commercial sample of the title compound.
Si
3
Me
+
Me
H
9
17
80
86
21
20
14
Cyclohexane
Benzene
9%
6%
Scheme 8. Rhodium-catalyzed intramolecular hydrosilylation of silane 9.

S. Díez-González, L. Blanco / Journal of Organometallic Chemistry 693 (2008) 2033–2040
2037
4.3. (4-Bromobutyl)chloromethylphenylsilane (2)
CH2), 33.4 (CH2–CH2Br), 35.9 (CH2Br); LRMS (70 eV) m/z (relative
intensity) 181 (10, M+–15), 179 (9, M+–15), 153 (6), 151 (6), 140
(7), 139 (100), 138 (8), 125 (51), 123 (50), 59 (69), 56 (32), 43
(13); IR 2959 (m), 2931 (m), 2112 (S, mSi–H), 1591 (m), 1271 (m),
1250 (S, dSi–CH3), 887 (SS), 836 (S) cmÀ1; HRMS Calc. for C6H15BrSi:
194.0126. Found: 194.0121.
Over 20 mL of refluxing cyclohexane containing a little grain of
H2PtCl6 (ꢀ1 mg), 4 g (25.6 mmol) of chloromethylphenylsilane 1
and 1.71 mL (16.7 mmol) of 4-bromobutene were added. After
12 h at reflux, the solvent was evaporated and the crude product
was purified by vacuum distillation to yield 6.31 g of the title com-
pound as a colorless oil (92%). B.p. 101 °C/0.08 torr; 1H NMR
(250 MHz, CDCl3) d 0.72 (s, 3 H, Si–CH3), 1.02–1.21 (m, 2H, Si–
CH2), 1.54–1.76 (m, 2H, Si–CH2–CH2), 1.95 (quintet, J = 6.3 Hz, 2H,
CH2–CH2Br), 3.43 (t, J = 6.3 Hz, 2H, CH2Br), 7.37–7.56 (m, 3H, CHAr),
7.56–7.73 (m, 2H, CHAr); 13C NMR (62.9 MHz, CDCl3) d 0.2 (Si–CH3),
17.0 (Si–CH2), 21.6 (Si–CH2–CH2), 33.1 (CH2–CH2Br), 35.5 (CH2Br),
128.1 (m-CHAr), 130.4 (p-CHAr), 133.2 (o-CHAr), 134.9 (C); LRMS
(70 eV) m/z (relative intensity) 279 (3, M+–15), 277 (10, M+–15),
275 (8, M+–15), 236 (12), 221 (24), 219 (20), 157 (46), 157 (17),
155 (100), 133 (12), 105 (14), 91 (72), 79 (14), 78 (15), 77 (18), 65
(35), 63 (74), 56 (16), 55 (22), 53 (11); IR 3073 (m, m@CH), 3056 (m,
m@CH), 3028 (m, m@CH), 2964 (S), 2937 (S), 2168 (S, mSi–H), 1591 (w,
mC@C), 1429 (S, mSi–Ar), 1258 (SS, dSi–CH3), 1116 (SS, dSi–Ar), 900 (S),
789 (S) cmÀ1; HRMS Calc. for C11H16BrClSi: 289.9893. Found:
289.9890.
4.7. (4-Bromobutyl)dichloromethylsilane (6)
Following the procedure described for the preparation of 2 with
3 mL (28.8 mmol) of dichloromethylsilane and 2.25 mL
(22.2 mmol) of 4-bromobutene, 4.90 g of the title compound were
isolated after vacuum distillation (88%). B.p. 40 °C/0.12 torr; 1H
NMR (250 MHz, CDCl3) d 0.80 (s, 3H, Si–CH3), 1.08–1.22 (m, 2H,
Si–CH2), 1.60–1.79 (m, 2H, Si–CH2–CH2), 1.99 (quintet, J = 7.0 Hz,
2H, CH2–CH2Br), 3.44 (t, J = 7.0 Hz, 2H, CH2Br); 13C NMR
(62.9 MHz, CDCl3) d 5.1 (Si–CH3), 20.5 (Si–CH2), 21.0 (Si–CH2–CH2),
32.7 (CH2–CH2Br), 34.8 (CH2Br); LRMS (70 eV) m/z (relative inten-
sity) 250 (1, M+), 248 (1, M+), 237 (14), 235 (32), 233 (18), 179 (11),
135 (11), 118 (3), 117 (15), 116 (5), 114 (100), 113 (89), 63 (11), 56
(42), 55 (16); IR 2938 (S), 1262 (S, dSi–CH3), 1224 (m), 810 (S), 788
(SS), 748 (S), 702 (S) cmÀ1; HRMS Calc. for C5H11BrCl2Si: 247.9190.
Found: 247.9176.
4.4. (4-Bromobutyl)chlorodimethylsilane (3)
4.8. (4-Bromobutyl)hexylmethylsilane (7)
Following the procedure described for the preparation of 2 with
6 mL (54 mmol) of chlorodimethylsilane and 3.7 mL (36 mmol) of
4-bromobutene, 7.53 g of the title compound were isolated after
vacuum distillation (97%). B.p. 80 °C/5 mm Hg. Spectroscopic data
were consistent with previously reported data for this compound
[33].
A THF solution of hexylmagnesium bromide was prepared from
0.38 g (16 mmol) of magnesium turnings activated with 85 lL
(1 mmol) of 1,2-dibromoethane and 2.1 mL (15 mmol) of 1-bromo-
hexane in 12 mL of dry THF. 7.2 mL of this Grignard solution were
added over 2.26 g (9.02 mmol) of dichlorosilane 6 in 10 mL of THF
cooled at 0°C. After 12 h of stirring at room temperature, THF was
evaporated and the remaining mixture was treated with dry pen-
tane. The resulting suspension was filtered under argon through
a canula to separate the magnesium salts. The filtrate was concen-
trated, then added over 14.5 mL (5.78 mmol) of a diethyl ether
solution 0.4 M in LiAlH4. After 12 h of reflux, the reaction mixture
was allowed to cool down to ambient temperature and treated
with cold water. After extraction of the aqueous phase with diethyl
ether, the combined organic phases were dried over sodium sul-
fate, then concentrated. The crude product was purified by vacuum
distillation to obtain 0.75 g of the title compound as a colorless oil
(31.5% over three steps). B.p. 84 °C/0.9 torr; 1H NMR (200 MHz,
CDCl3) d: 0.06 (d, J = 3.5 Hz, 3H, Si–CH3), 0.50–0.71 (m, 4H, CH2–
Si–CH2), 0.90 (t, J = 5.5 Hz, 3H, CH2–CH3), 1.18–1.40 (m, 8H, CH2–
CH2–CH2–CH2–CH3), 1.43–1.60 (m, 2H, CH2–CH2–CH2Br), 1.87
(quintet, J = 6.9 Hz, 2H, CH2–CH2Br), 3.43 (t, J = 6.9 Hz, 2H, CH2Br),
3.78 (sextet, J = 3.5 Hz, 1H, Si–H); 13C NMR (62.9 MHz, CDCl3) d:
À6.2 (Si–CH3), 11.9 (Si–CH2), 12.7 (Si–CH2), 14.2 (CH2–CH3), 22.7
(CH2Hex), 23.2 (Si–CH2–CH2), 24.5 (CH2Hex), 31.7 (CH2Hex), 33.0
(CH2Hex), 33.5 (CH2–CH2Br), 36.1 (CH2Br); LRMS (70 eV) m/z (rela-
tive intensity) 266 (1, M+), 264 (1, M+), 181 (47), 179 (44), 153
(27), 151 (28), 140 (6), 139 (98), 138 (7), 137 (100), 131 (7), 129
(6), 124 (8), 123 (97), 99 (18), 73 (23), 72 (7), 71 (7), 69 (11), 59
(22); IR 2957 (S), 2923 (SS), 2855 (S), 2106 (S, mSi–H), 1456 (S),
1270 (m), 1251 (S, dSi–CH3), 958 (m), 881 (S) cmÀ1; HRMS calcd
for C11H25BrSi: 264.0909. Found: 264.0911.
4.5. (4-Bromobutyl)methylphenylsilane (4)
Over 32 mL (7.01 mmol) of a 0.22 M solution of LiAlH4 in diethyl
ether, 6.16 g (21.1 mmol) of chlorosilane 2 were added. After 12 h at
reflux, the reaction mixture was cooled down to ambient tempera-
ture and treated with 50 mL of cold water. After extraction of the
aqueous phase with diethyl ether, the combined organic phases
were dried over sodium sulfate. The crude product was purified
by vacuum distillation to yield 4.74 g of the title compound as a col-
orless oil (87%). B.p. 95 °C/4 mbar; 1H NMR (200 MHz, CDCl3) d 0.34
(d, J = 3.6 Hz, 3H, Si–CH3), 0.78–0.94 (m, 2H, Si–CH2), 1.44–1.65 (m,
2H, Si–CH2–CH2), 1.91 (quintet, J = 6.9 Hz, 2H, CH2–CH2Br), 3.40 (t,
J = 6.9 Hz, 2H, CH2Br), 4.36 (sextet, J = 3.6 Hz, 1H, Si–H), 7.30–7.47
(m, 3H, m-CHAr +p-CHAr), 7.47–7.60 (m, 2H, o-CHAr); 13C NMR
(62.9 MHz, CDCl3) d À5.8 (Si–CH3), 12.4 (Si–CH2), 22.9 (Si–CH2–
CH2), 33.4 (CH2–CH2Br), 35.8 (CH2Br), 127.8 (m-CHAr), 129.3 (p-
CHAr), 134.2 (o-CHAr), 136.0 (C); LRMS (70 eV) m/z (relative inten-
sity) 258 (0.1, M+), 256 (0.1, M+), 243 (13), 241 (11), 202 (11), 201
(20), 200 (12), 199 (17), 187 (36), 185 (36), 152 (70), 150 (68),
124 (19), 122 (16), 121 (100), 105 (33), 69 (12), 43 (13); IR 2930
(m), 2115 (S, mSi–H), 1427 (S, mSi–Ar), 1251 (m, dSi–CH3), 1115 (S, dSi–Ar),
879 (SS), 701 (S) cmÀ1; HRMS Calc. for C11H17BrSi: 256.0291.
Found: 256.0293.
4.6. (4-Bromobutyl)dimethylsilane (5)
Following the procedure described for the preparation of chlo-
rosilane 4 with 7.53 g (32.8 mmol) of chlorosilane 3, 5.31 g of the
title compound were isolated after vacuum distillation (83%). B.p.
58 °C/5 mm Hg; 1H NMR (200 MHz, CDCl3) d 0.10 (d, J = 3.8 Hz,
6 H, Si–CH3), 0.54–0.70 (m, 2H, Si–CH2), 1.41–1.60 (m, 2H, Si–
CH2–CH2), 1.91 (quintet, J = 6.4 Hz, 2H, CH2–CH2Br), 3.43 (t,
J = 6.4 Hz, 2H, CH2Br), 3.77–3.84 (m, 1H, Si–H); 13C NMR
(62.9 MHz, CDCl3) d À4.6 (Si–CH3), 13.2 (Si–CH2), 22.9 (Si–CH2–
4.9. Hexyl(hex-5-ynyl)methylsilane (8)
In a round-bottom-flask, 38 mg (0.42 mmol) of ethynyllithium/
ethylenediamine complex were stirred in 0.3 mL (8.8 mmol) of
hexamethylphosphorous triamide and 1 mL of THF for 20 min be-
fore addition of 49 lL (0.19 mmol) of (4-bromobutyl)silane 7. After
2 h of stirring at ambient temperature, the reaction mixture was
diluted with pentane and washed with cold water. After extraction

2038
S. Díez-González, L. Blanco / Journal of Organometallic Chemistry 693 (2008) 2033–2040
of the aqueous phase with pentane, the combined organic phases
were washed with water and brine, then dried over sodium sulfate
and concentrated. Purification of the crude product by column
chromatography (pentane) afforded 31 mg of the title compound
as a colorless oil (78%). 1H NMR (400 MHz, CDCl3) d: 0.07 (d,
J = 3.5 Hz, 3H, Si–CH3), 0.48–0.69 (m, 4H, CH2–Si–CH2), 0.91 (t,
J = 6.8 Hz, 3H, CH2–CH3), 1.16–1.40 (m, 8H, CH2–CH2–CH2–CH2–
CH3), 1.48 (quintet, J = 8.0 Hz, 2H, Si–CH2–CH2), 1.58 (quintet,
J = 7.3 Hz 2H, CH2–CH2–C„CH), 1.95 (t, J = 2.5 Hz, 1H, C„CH),
2.20 (dt, J = 2.5, 7.3 Hz, 2H, CH2–C„CH), 4.79 (octet, J = 3.5 Hz,
1H, Si–H); 13C NMR (62.9 MHz, CDCl3) d: À6.3 (Si–CH3), 12.2 (Si–
CH2), 12.6 (Si–CH2), 14.1 (CH2–CH3), 18.0 (CH2–C„CH), 22.6
(CH2Hex), 23.6 (Si–CH2–CH2), 24.4 (CH2Hex), 31.6 (CH2Hex), 31.8
(CH2–CH2–C„CH), 32.9 (CH2 Hex), 68.1 (C„CH), 84.6 (C„CH); IR
3313 (S, m„CH), 2957 (S), 2923 (SS), 2856 (S), 2106 (S, mSi–H or mC„C),
1459 (m), 1251 (S, dSi–CH3), 881 (F), 630 (S) cmÀ1; Elemental anal-
ysis Calc. for C13H26Si: C, 74.20; H, 12.45. Found: C, 74.35; H,
12.38%.
cmÀ1; HRMS Calc. for C8H16Si: 140.1021. Found: 140.1016. Ele-
mental analysis Calc. for C8H16Si: C, 68.49; H, 11.49. Found: C,
68.12; H, 11.67%.
4.12. (4-Iodobutyl)methylphenylsilane (12)
Over 1.22 g (8.14 mmol) of sodium iodide in 8 mL of refluxing
butanone, 1.61 g (6.27 mmol) of (4-bromobutyl)silane 4 were
added. After 14 h of reaction, the reaction mixture was cooled
at ambient temperature, then filtered. The filtrate was diluted
with pentane and washed successively with water, an aqueous
solution 0.1 M of sodium bicarbonate, water, a saturated aqueous
solution of sodium thiosulfate and brine, then dried over sodium
sulfate and concentrated. The crude product was purified by vac-
uum distillation to obtain 1.69 g of the title compound as a color-
less oil (89%). B.p. 88 °C/0.1 mbar; 1H NMR (200 MHz, CDCl3) d:
0.37 (d, J = 3.4 Hz, 3H, Si–CH3), 0.78–0.93 (m, 2H, Si–CH2), 1.42–
1.59 (m, 2H, Si–CH2–CH2), 1.87 (quintet, J = 6.6 Hz, 2H, CH2–
CH2I), 3.18 (t, J = 6.6 Hz, 2H, CH2I), 4.36 (sextet, J = 3.4 Hz, 1H,
Si–H), 7.33–7.44 (m, 3H, m-CHAr + p-CHAr), 7.48–7.60 (m, 2H, o-
CHAr); 13C NMR (50.3 MHz, CDCl3) d: 5.7 (Si–CH3), 6.5 (Si–CH2),
12.3 (Si–CH2–CH2), 25.2 (CH2–CH2I), 36.5 (CH2I), 127.9 (m-CHAr),
129.3 (p-CHAr), 134.2 (o-CHAr), 136.1 (C); LRMS (70 eV) m/z (rela-
tive intensity) 304 (1, M+), 290 (8), 289 (57), 245 (24), 233 (52),
226 (19), 122 (22), 121 (100), 105 (28), 100 (9), 99 (87), 43 (7);
IR 3067 (m, m@CH), 3044 (m, m@CH), 3056 (m, m@CH), 2926 (F),
2144 (SS, mSi–H), 1427 (S, mSi–Ar), 1251 (S, dSi–CH3), 1200 (m), 1115
(SS, dSi–Ar), 878 (SS), 850 (SS), 723 (S); HRMS Calc. for C11H17ISi:
304.0139. Found: 304.0121.
4.10. (Hex-5-ynyl)methylphenylsilane (9)
(A) Following the procedure described for the preparation of 8
with 1.69 g (5.56 mmol) of (4-iodobutyl)phenylsilane 12 and
0.62 g (6.76 mmol) of ethynyllithium/ethylenediamine complex
in 4 mL of DMSO, 0.36 g of the title compound were isolated as a
colorless oil after vacuum distillation (32%). (B) In a three-neck
round-bottom-flask, 0.47 g (20 mmol) of magnesium turnings,
0.17 mL (2 mmol) of 1,2-dibromethane and 5 mL of THF were
introduced. This mixture was gently heated until gas evolution
and then a solution containing 1.5 mL (10 mmol) of chlorosilane
1 and 1.5 mL (10 mmol) of 6-iodohexyne in 5 mL of THF were
added in a rate that allowed to maintain the reaction mixture tem-
perature below 40 °C (Caution: this reaction is very exothermic,
specially in the beginning of the addition). Once the addition fin-
ished, the reaction mixture was stirred at 40 °C for two hours be-
fore being cooled at ambient temperature and filtered in order to
separate the unreacted magnesium. The filtrate was diluted with
diethyl ether and treated with a saturated solution of ammonium
chloride. After extraction of the aqueous phase with diethyl ether,
the combined organic phases were washed with water until neu-
trality, then dried over sodium sulfate and concentrated. Purifica-
tion of the crude material by vacuum distillation afforded 0.14 g
of the title compound as a colorless oil (35%). B.p. 64 °C/0.08 torr.
Spectroscopic data were consistent with previously reported data
for this compound [19].
4.13. (4-Iodobutyl)dimethylsilane (13)
Following the procedure described for the preparation of 12
with 3.66 g (18.8 mmol) of (4-bromobutyl)silane 5, 3.15 g of the ti-
tle compound were isolated as a colorless oil after vacuum distilla-
tion (69%). B.p. 82 °C/5 mm Hg; 1H NMR (200 MHz, CDCl3) d: 0.09
(d, J = 3.6 Hz, 6H, Si–CH3), 0.54–0.68 (m, 2H, Si–CH2), 1.37–1.53
(m, 2H, Si–CH2–CH2), 1.86 (quintet, J = 6.8 Hz, 2H, CH2–CH2I),
3.20 (t, J = 6.8 Hz, 2H, CH2I), 3.38–3.93 (m, 1H, Si–H); 13C NMR
(50.3 MHz, CDCl3) d À4.5 (Si–CH3), 6.8 (Si–CH2), 13.0 (Si–CH2–
CH2), 25.3 (CH2–CH2I), 36.5 (CH2I); LRMS (70 eV) m/z (relative
intensity) 242 (2, M+), 227 (42), 186 (14), 185 (31), 171 (38), 127
(2), 87 (12), 73 (17), 60 (18), 59 (100), 57 (7), 44 (7), 43 (33); IR
2957 (m), 2926 (m), 2111 (S, mSi–H), 1249 (S, dSi–CH3), 1201 (m),
888 (SS), 836 (m) cmÀ1; HRMS Calc. for C6H15ISi: 241.9988. Found:
241.9986.
4.11. (Hex-5-ynyl)dimethylsilane (10)
4.14. Chloro(hex-5-ynyl)methylsilane (14)
(A) Following the procedure described for the preparation of the
8 with 1.58 g (6.5 mmol) of (4-iodobutyl)silane 13 and 0.72 g
(7.9 mmol) of ethynyllithium/ethylenediamine complex in 5 mL
of DMSO, 0.15 g of the title compound were isolated as a colorless
oil after vacuum distillation (16%). (B) Following the procedure B
described for the preparation of 9 with 1.1 mL (10 mmol) of chlo-
rodimethylsilane and 1.5 mL (10 mmol) of 6-iodohexyne, 0.36 g
of the title compound were isolated after vacuum distillation
(26%). B.p. 62 °C/40 mm Hg; 1H NMR (200 MHz, CDCl3) d: 0.08 (d,
J = 3.4 Hz, 6H, Si–CH3), 0.53–0.68 (m, 2H, Si–CH2), 1.36–1.65 (m,
4H, Si–CH2–CH2–CH2), 1.95 (t, J = 2.8 Hz, 1H, C„CH), 2.20 (dt,
J = 2.8, 7.6 Hz, 2H, CH2–C„CH), 3.86–3.94 (m, 1H, Si–H); 13C
NMR (62.9 MHz, CDCl3) d: À4.6 (Si–CH3), 13.6 (Si–CH2), 18.0
(CH2–C„CH), 23.5 (Si–CH2–CH2), 31.7 (CH2–CH2–C„CH), 68.1
(C„CH), 84.4 (C„CH); LRMS (70 eV) m/z (relative intensity) 140
(2, M+), 139 (11), 125 (66), 99 (16), 98 (100), 97 (34), 83 (57), 80
(13), 69 (23), 67 (13), 59 (42), 43 (18); IR 3312 (S, m„CH), 2935
(S), 2112 (S, mSi–H), 1250 (S, dSi–CH3), 889 (SS), 836 (m), 630 (m)
Following the procedure B described for the preparation of 9
with 2.1 mL (20 mmol) of dichloromethylsilane and 1.5 mL
(10 mmol) of 6-iodohexyne, 1.03 g of the title compound were iso-
lated after filtration under argon through a cannula, followed by
vacuum distillation (64%). B.p. 85 °C/10 mm Hg; 1H NMR
(200 MHz, CDCl3) d: 0.52 (d, J = 3.3 Hz, 3H, Si–CH3), 0.87–1.12 (m,
2H, Si–CH2), 1.40–1.74 (m, 4H, Si–CH2–CH2–CH2), 1.96 (t,
J = 2.6 Hz, 1H, C„CH), 2.22 (dt, J = 2.6, 6.4 Hz, 2H, CH2–C„CH),
4.82 (sextet, J = 3.3 Hz, 1H, Si–H); 13C NMR (62.9 MHz, CDCl3) d:
1.2 (Si–CH3), 16.2 (Si–CH2), 18.0 (CH2–C„CH), 22.0 (Si–CH2–CH2),
31.5 (CH2–CH2–C„CH), 68.1 (C„CH), 84.4 (C„CH); LRMS
(70 eV) m/z (relative intensity) 125 (36, M+ÀCl), 109 (6), 99 (13),
98 (11), 97 (100), 95 (26), 85 (24), 83 (17), 79 (21), 71 (29), 69
(17), 59 (67), 55 (12), 45 (51), 43 (77); IR 3306 (m, m„CH), 2937
(S), 2863 (m), 2162 (S, mSi–H), 2119 (w, mC„C), 1258 (S, dSi–CH3),
1095 (S), 891 (SS), 635 (m) cmÀ1; Elemental analysis Calc. for
C7H13ClSi: C, 52.31; H, 8.15. Found: C, 52.55; H, 8.01%.

S. Díez-González, L. Blanco / Journal of Organometallic Chemistry 693 (2008) 2033–2040
2039
4.15. Allyl(hex-5-ynyl)methylsilane (15)
4.18. 1-Methyl-2-methylidene-1-phenyl-1-silacyclohexane (17)
Over 0.46 g (2.8 mmol) of chlorosilane 14 in 3 mL of THF,
1.55 mL (2.8 mmol) of a THF solution 1.8 M in allylmagnesium
chloride were added. After 14 h of stirring at room temperature,
the reaction mixture was treated with a saturated solution of
ammonium chloride. After extraction of the aqueous phase with
diethyl ether, the combined organic phases were washed with
water until neutrality, then dried over sodium sulfate and concen-
trated. Purification of the crude product by column chromatogra-
Following the general procedure for the intramolecular hydrosi-
lylation, from 51 mg (0.25 mmol) of silane 9 and after purification
by column chromatography (pentane), 21 mg of the title com-
pound were isolated as a colorless oil (42%). Spectroscopic data
were consistent with previously reported data for this compound
[15].
4.19. 1-Allyl-1-methyl-2-methylidene-1-silacyclohexane (20)
phy (pentane) afforded 0.16 g of the title compound as
a
colorless oil (34%). 1H NMR (250 MHz, CDCl3) d: 0.09 (d,
J = 3.5 Hz, 3H, Si–CH3), 0.55–0.73 (m, 2H, Si–CH2–CH2), 1.36–1.70
(m, Si–CH2–CH2–CH2) and 1.52 (d, J = 6.5 Hz, Si–CH2–CH@) (6H),
1.95 (t, J = 2.6 Hz, 1H, C„CH), 2.21 (dt, J = 2.6, 6.6 Hz, 2H, CH2–
C„CH), 3.78–3.87 (m, 1H, Si–H), 4.87 (d, J = 9.8 Hz, 1H, CH@CH2
cis), 4.90 (d, J = 18.7 Hz, 1H, CH@CH2 trans), 5.82 (ddt, J = 6.5, 9.8,
18.7 Hz, 1H, Si–CH2–CH@); 13C NMR (62.9 MHz, CDCl3) d: À6.7
(Si–CH3), 11.7 (Si–CH2), 18.0 (CH2–C„CH), 20.3 (Si–CH2–CH@),
23.4 (Si–CH2–CH2), 31.7 (CH2–CH2–C„CH), 68.1 (C„CH), 84.5
(C„CH), 113.3 (CH@CH2), 134.7 (CH@CH2); LRMS (70 eV) m/z (rel-
ative intensity) 151 (3, M+À15), 126 (8), 99 (16), 98 (15), 97 (100),
95 (30), 85 (21), 83 (21), 83 (15), 79 (19), 71 (26), 69 (17), 67 (10),
59 (74), 57 (10), 55 (17), 53 (13), 45 (65), 43 (91); IR 3310 (S, m„CH),
3078 (m, m@CH), 2934 (SS), 2115 (SS, mSi–H), 1631 (S, mC@C), 1419 (m,
d@CH), 2153 (S, dSi–CH3), 1159 (m), 992 (S, d@CH), 882 (S), 812 (S), 632
(S) cmÀ1; Elemental analysis Calc. for C10H18Si: C, 72.21; H, 10.91.
Found: C, 72.39; H, 11.15%.
Following the general procedure for the intramolecular hydrosi-
lylation but at 70 °C and with a final calculated concentration of
0.007 M, from 139 mg (0.83 mmol) of silane 15 and after purifica-
tion by column chromatography (pentane), 25 mg of the title com-
pound were isolated as a colorless oil (18%). Spectroscopic data
were consistent with previously reported data for this compound
[15].
Acknowledgements
The CNRS is gratefully acknowledged for financial support of
this work. S. D.-G. Thanks the Education, Research and Universities
Department of the Basque Government (Spain) for a doctoral
fellowship.
References
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4.16. General procedure for the intramolecular hydrosilylation of
(hex-5-ynyl)silanes
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6956;
In a two-neck round-bottom-flask with a condenser fitted with
a calcium chloride guard, a little grain of hexachloroplatinic acid
(ꢀ1 mg) and 6.5 mL of cyclohexane were heated to reflux. A solu-
tion of 0.25 mmol of a (hex-5-ynyl)silane in 3.5 mL of cyclohexane
was then added over 40 min. At the end of the addition, the reac-
tion mixture was cooled down to ambient temperature, then fil-
tered over a plug of silica gel (diethyl ether). After evaporation of
the solvent, the crude product was purified by column
chromatography.
4.17. 1-Hexyl-1-methyl-2-methylidene-1-silacyclohexane (16)
Following the general procedure for the intramolecular hydrosi-
lylation, from 53 mg (0.25 mmol) of silane 8 and after purification
by column chromatography (pentane), 35 mg of the title com-
pound were isolated as a colorless oil (66%). 1H NMR (200 MHz,
CDCl3) d: 0.08 (s, 3H, Si–CH3), 0.60 (ddd, J = 4.6, 9.7, 14.0 Hz, Si–
CH2Cy) and 0.60–0.73 (m, Si–CH2Hex) (3H), 0.74 (ddd, J = 4.6, 7.1,
14.0 Hz, 1H, Si–CH2Cy), 0.92 (t, 3H, J = 6.8 Hz, CH3–CH2), 1.13–
1.39 (m, 8H, CH2–CH2–CH2–CH2–CH3), 1.39–1.52 (m, 1H, Si–CH2–
CH2–CH2Cy), 1.52–1.64 (m, 1H, Si–CH2–CH2–CH2Cy), 1.64–1.86 (m,
2H, Si–CH2–CH2Cy), 2.25–2.41 (m, 2H, Si–C–CH2), 5.10 (d, J = 3.5
Hz, 1H, C@CH2), 5.45 (d, J = 3.5 Hz, 1H, C@CH2). 13C NMR
(50.3 MHz, CDCl3) d: À5.5 (Si–CH3), 12.8 (Si–CH2Hex), 13.6 (Si–
CH2Cy), 14.1 (CH3–CH2), 22.6 (CH2Hex), 23.7 (CH2Hex), 24.5 (Si–
CH2–CH2Cy), 31.0 (Si–CH2–CH2–CH2Cy), 31.6 (CH2Hex), 33.3 (CH2Hex),
39.9 (Si–C–CH2), 121.2 (C@CH2), 152.3 (C@CH2); LRMS (70 eV) m/z
(relative intensity) 210 (6, M+), 195 (2), 127 (16), 126 (52), 125
(86), 111 (27), 109 (11), 99 (27), 98 (21), 97 (100), 95 (19), 85
(21), 83 (26), 81 (11), 73 (17), 71 (40), 69 (16), 59 (61), 58 (10),
57 (11), 55 (17), 45 (29), 43 (49); HRMS Calc. for C13H26Si:
210.1804. Found: 210.1804. Elemental analysis Calc. for C13H26Si:
C, 74.20; H, 12.45. Found: C, 74.04; H, 12.61%.
(b) J.A. Marshall, M.M. Yanik, Org. Lett. 2 (2000) 2173–2175;
(c) S.E. Denmark, W. Pan, Org. Lett. 3 (2001) 61–64.
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(b) A.J. Chalk, J.F. Harrod, J. Am. Chem. Soc. 87 (1965) 16–21;
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[11] (a) S.E. Denmark, W. Pan, Org. Lett. 4 (2002) 4163–4166;
(b) S.V. Maifeld, M.N. Tran, D. Lee, Tetrahedron Lett. 46 (2005) 105–108.
[12] (a) B.M. Trost, Z.T. Ball, J. Am. Chem. Soc. 125 (2002) 30–31;
(b) L.W. Chung, Y.-D. Wu, B.M. Trost, Z.T. Ball, J. Am. Chem. Soc. 125 (2003)
11578–11582.
[13] T. Sudo, N. Asao, Y. Yamamoto, J. Org. Chem. 65 (2000) 8919–8923.
[14] (a) For reviews, see: J. Hermanns, B. Schmidt, J. Chem. Soc. Perkin Trans. 1
(1998) 2209–2230;
(b) For reviews, see: J. Hermanns, B. Schmidt, J. Chem. Soc. Perkin Trans 1
(1999) 81–102.
[15] S. Díez-González, L. Blanco, J. Organomet. Chem. 691 (2006) 5531–5539.
[16] (a) A.G. Brook, S.A. Fieldhouse, J. Organomet. Chem. 10 (1967) 235–246;
(b) For
the
preparation
of
related
2-methylidene-3-phenyl-1-
silacyclohexanes, see: Y. Takeyama, K. Nozaki, K. Matsumoto, K. Oshima, K.
Utimoto, Bull. Chem. Soc. Jpn. 64 (1991) 1461–1466;
(c) For the preparation of 2-formylmethylidene-1-silacycloalkanes, see: F.
Monteil, I. Machuda, H. Alper, J. Am. Chem. Soc. 117 (1995) 4419–4420.
[17] Chloromethylphenylsilane
1
was prepared by solvent-free selective
monochlorination of the methylphenylsilane by CuCl2 in the presence of a
sub-stoichiometric quantity of CuI, see A. Kunai, T. Kawakami, E. Toyoda, M.
Ishikawa, Organometallics 11 (1992) 2708–2711.

2040
S. Díez-González, L. Blanco / Journal of Organometallic Chemistry 693 (2008) 2033–2040
[18] The 1H NMR spectrum of 11 was similar to the one of 9 but it presented an
extra singlet at 2.52 ppm, assignable to the acetylenic hydrogen of the second
triple bond.
[19] L.A. Aronica, M.A. Caporusso, P. Salvadori, J. Org. Chem. 64 (1999) 9711–9714.
[20] E. Negishi, Organometallics in Organic Synthesis, Wiley, New York, 1980.
[21] (a) H.P. Knoess, M.T. Furlong, M.J. Rozema, P. Knochel, J. Org. Chem. 56 (1991)
5974–5978;
protons. In LRMS an ion at m/z = 140, which correspond to the formula weight
of the desired product, was obtained.
[25] When a THF solution 0.025 M of 2-methylidene-1-silacyclohexane 17 was
heated at 40 °C in the presence of hexachloroplatinic acid, 40% of the silane
was converted after only one hour, as determined by GC and 1H NMR.
[26] (a) R.A. Benkeser, Y. Nagal, J.L. Noe, R.F. Cunico, P.H. Gund, J. Am. Chem. Soc. 86
(1964) 2446–2451;
(b) P. Knochel, M.C.P. Yeh, J. Org. Chem. 53 (1988) 2392–2394.
[22] B.p. 61 °C/25 mm Hg. The 1H NMR spectrum of this fraction presented
different signals between 0.45 and 0.65 ppm which shows the presence of
more than one product with a methyl group on the silicon atom, as well as two
massifs between 1.50–1.90 and 2.12–2.52 ppm and a singlet at 4.72 ppm.
These signals could be attributed to products of general structure:
(b) A.G. Brook, J.B. Pierce, J. Am. Chem. Soc. 85 (1965) 2566–2571.
[27] (a) I. Ojima, M. Kumagai, Y. Nagai, J. Organomet. Chem. 66 (1974) C14–
C15;
(b) K.A. Brady, T.A. Nile, J. Organomet. Chem. 206 (1981) 299–304.
[28] We recently reported the formation of this silacycloheptene by radical
cyclization of the corresponding (4-bromobutyl)ethynylsilane, see Ref. [15].
[29] I. Ojima, S. Inaba, T. Kogure, J. Organomet. Chem. 55 (1973) C7–C8.
[30] The structure of this silanol was confirmed by its 1H NMR spectrum which was
similar to the one of silane 9 and presented a singlet at 1.81 ppm, assignable to
the hydrogen of the hydroxyl group. The IR spectrum also showed a broad
band at 3295 cmÀ1, characteristic of alcohols.
[31] G.A. Kraus, K. Landgrebe, J. Chem. Soc., Chem. Commun. (1984) 885–886.
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2918.
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112 (1990) 797–801.
MeR1R2Si
H
.
[23] L.N. Lewis, J. Am. Chem. Soc. 112 (1990) 5998–6004.
[24] The 1H NMR spectrum of the crude product showed the total conversion of the
starting material and presented the characteristic signals of this family of
products, notably two doublets at 5.14 and 5.45 ppm due to the olefinic