The carbon-silicon bond cleavage of organosilicon compounds in supercritical water

Article abstract of DOI:10.1246/bcsj.77.2071

Arylsilanes, alkenylsilanes, allylic silanes, and alkylsilanes were found to undergo extremely facile and rapid C-Si bond cleavage in supercritical water. Rapid C-Si bond cleavage occurred even with robust unactivated tetraalkylsilanes. The control experiments revealed the dramatic difference between the supercritical and subcritical conditions, and that between supercritical water and supercritical methanol, attesting to a unique reactivity of supercritical water in C-Si bond cleavage. It was also found that acids, such as HCl, HBr, and H₂SO₄, promote C-Si bond cleavage in supercritical water.

Full text of DOI:10.1246/bcsj.77.2071

Ó 2004 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 77, 2071–2080 (2004) 2071
The Carbon–Silicon Bond Cleavage of Organosilicon Compounds
in Supercritical Water
ꢀ
ꢀ
ꢀ;1
Kenichiro Itami, Koji Terakawa, Jun-ichi Yoshida, and Okitsugu Kajimoto
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering,
Kyoto University, Nishikyo-ku, Kyoto 615-8510
1Department of Chemistry, Graduate School of Science, Kyoto University,
Kitashirakawa-Oiwakecho, Kyoto 606-8502
Received May 26, 2004; E-mail: yoshida@sbchem.kyoto-u.ac.jp
Arylsilanes, alkenylsilanes, allylic silanes, and alkylsilanes were found to undergo extremely facile and rapid C–Si
bond cleavage in supercritical water. Rapid C–Si bond cleavage occurred even with robust unactivated tetraalkylsilanes.
The control experiments revealed the dramatic difference between the supercritical and subcritical conditions, and that
between supercritical water and supercritical methanol, attesting to a unique reactivity of supercritical water in C–Si
bond cleavage. It was also found that acids, such as HCl, HBr, and H2SO4, promote C–Si bond cleavage in supercritical
water.
In recent years, considerable attention has been directed to-
ward a new medium for chemical synthesis (reaction and sep-
aration) for many reasons.1 For example, the execution of or-
ganic reactions in water (or aqueous media)2 has received par-
ticular attention by organic chemists, since it allows ‘‘green’’
or environmentally benign chemical processes.3 In addition,
the exploitation of unique properties of water, such as hydro-
phobic effects, hydrogen-bonding interactions, and high polar-
ity, has been a recent topic of interest, and many interesting
chemical reactions in water have been continuously reported
very recently.4,5
Supercritical water (scH2O, the critical temperature: 374 ꢁC,
the critical pressure: 22.1 MPa) has been attracting increasing
attention because of its unique physical and chemical proper-
ties, which are very different from those of ambient water.6
For example, because the dielectric constant is much lower,
many organic compounds are miscible in scH2O. Furthermore,
the ion-dissociation constant of water initially increases as the
temperature rises, and drops dramatically at the critical point
under a constant-pressure condition.
Because of its harsh conditions and miscibility of organic
compounds and oxygen, scH2O has tended to be used as a me-
dium for the oxidative treatment of organic waste, or for the
degradation of waste synthetic polymers, vegetable oils, and
biomass. Recently, however, many researchers have set out
to use scH2O as a medium of chemical synthesis. Many exam-
ples have proved that selective transformation and bond forma-
tion are plausible instead of complete decomposition of organ-
ic compounds. These include the Diels–Alder reaction,7
Friedel–Crafts alkylation,8 Beckmann and pinacol rearrange-
ments,9 ester hydrolysis,10 and Pd-catalyzed Mizoroki–Heck
reaction.11
new reaction medium, but also as a Lewis basic donor (activa-
tor) for silicon under supercritical conditions. Our continuing
interests in silicon-based organic synthesis13 and in aqueous
organic reactions14 have led us to explore the feasibility of sil-
icon-based organic synthesis in scH2O, which has not been re-
ported to date. During the course of this study, we discovered
an extremely facile C–Si bond cleavage of organosilicon com-
pounds in scH2O for the first time, which serves as a starting
point toward the development of silicon-based organic synthe-
sis in scH2O (Eq. 1).15
Supercritical Water
ð1Þ
R
SiMe2X
R H
C–Si BOND CLEAVAGE
R = aryl, alkenyl, allyl, and alkyl
X = OH, Cl, OEt, OSiR'3, SiMe3, Me
In this paper, we report on the full details of this study.
Results and Discussion
Examined Organosilicon Compounds. In this study, a
wide array of organosilicon compounds with different structur-
al and electronic properties was examined. They are shown in
Fig. 1. We began our research by examining arylsilanes, al-
kenysilanes, and allylic silanes, which usually exhibit high re-
activity toward C–Si bond cleavage. As for more robust alkyl-
silanes, compounds with heteroatom on silicon were initially
examined. Most challenging tetraalkylsilanes were examined
in detail, including the effect of additives.
Apparatus.
Reactions of organosilicon compounds in
scH2O were carried out, as shown in Fig. 2 (see Experimental
Section for details). As usual, the reactions could be conducted
directly in a stainless-steel container (SUS316), submerged in
a dissolved salt bath (NaNO2/KNO3) of high temperature
(method A). However, any positive or negative effect of the
stainless-steel reactor (metallic surface) cannot be excluded
Organosilicon compounds have been extensively utilized in
modern organic synthesis.12 Taking the high oxophilicity of
silicon into account, water would be expected not only as a
Published on the web November 11, 2004; DOI 10.1246/bcsj.77.2071

2072 Bull. Chem. Soc. Jpn., 77, No. 11 (2004)
C–Si Bond Cleavage in Supercritical Water
by using this method.16 Therefore, most of the reactions in this
study (except for reactions using 3 and 4) were performed in a
sealed quartz tube placed in a stainless-steel container (method
B).17 To avoid breakage of the quartz ampoule due to a pres-
sure increase, a calculated amount of water was added to the
stainless tube to maintain a balanced pressure. The temperature
was monitored by a thermocouple inserted through the top end
of the stainless-tube container. The stainless tube was sub-
merged in a dissolved salt bath (NaNO2/KNO3), whose tem-
perature was controlled. After a specified time, the tube was
removed and cooled in a water bath. The reaction products
were analyzed by standard methods, such as capillary GC,
GC–MS, and NMR. Although we have never experienced an
accident, all reactions in supercritical water should be per-
formed with great care due to the high-temperature/pressure
conditions.
Arylsilanes. Electrophilic cleavage of C–Si bonds in aryl-
silanes has been extensively utilized in organic synthesis be-
cause a coming electrophile always occupies the position
where the silyl group has been attached.18 This ipso substitu-
tion is extremely useful in the regioselective carbon–carbon
and carbon–heteroatom bond formations at aromatic rings. It
is generally assumed that proton transfer, rather than desilyla-
tion, is the rate-determining step of this reaction.19 Thus, we
began our research by subjecting arylsilanes to scH2O. When
trimethylphenylsilane (1) was subjected ꢁto scH2O, C–Si bond
cleavage occurred within 30 min at 390 C to give benzene in
72% yield (Eq. 2).
Arylsilanes
Alkenylsilanes
Allylicsilanes
SiMe3
R
SiMe3
3: R = n-C10H21
R
SiMe3
4: R = n-C9H19
R
1: R = H
2: R = n-C4H9
Alkylsilanes with heteroatom on silicon
SiMe3
H
scH2O
ð2Þ
RSiMe2OH
n-C12H25SiMe2X
n-C12H25SiMe2H
72%
390 °C, 27 MPa
5: R = n-C12H25
7: X = Cl
11
30 min
1
6: R = n-C10H21CH(CH3)
8: X = OEt
Me3Si(OSiMe2)nOSiMe3
(n = 0, 1, 2)
9: X = OSiMe2C12H25
10: X = SiMe3
observed by GC-MS
Tetraalkylsilanes
As judged by GC–MS analysis, siloxanes Me3Si(OSiMe2)n-
OSiMe3 (n ¼ 0{2) were found in the reaction mixture under
these conditions. Similarly, (4-butylphenyl)trimethylsilane
(2) also underwent rapid C–Si bond cleavage within 30 min
RSiMe3
n-C12H25SiR3
14: R = Et
(n-C12H25)4Si
12: R = n-C12H25
13: R = n-C10H21CH(CH3) 15: R = i-Pr
16
ꢁ
Fig. 1. Examined organosilicon compounds in this study.
at 390 C to give butylbenzene in 91% yield (Eq. 3).
thermocouple
Method A
supercritical
condition
substrates
water
stainless steel
container (SUS316)
dissolved bath (NaNO2/KNO3)
Method B
supercritical
condition
substrates
water
quartz ampoule
Fig. 2. Methods for the reactions of organosilicon compounds in supercritical water.

K. Itami et al.
Bull. Chem. Soc. Jpn., 77, No. 11 (2004) 2073
cenes increased to >95/5. This is in a sharp contrast with
the reaction of 3 in scH2O after 5 min (19/81; Eq. 4). Quite
interestingly, the competitive reaction of 3 and 4 indicated a
faster C–Si bond cleavage of 3 in scH2O, although the opposite
reactivity order is generally observed in the reaction with elec-
trophiles.20 Indeed, when we subjected a 1:1 mixture of 3 and
4 into a benzene solution of HI at room temperature,21 allylic
silane 4 underwent protodesilylation faster than alkenylsilane 3
(Eq. 6),
SiMe3
H(D)
scH2O or scD2O
ð3Þ
390 °C, 30 min
Bu
Bu
2
scH2O: 91% yield
scD2O: 74% yield, >95% D
As expected, the use of D2O resulted in the introduction of
deuterium (>95% D) at the position where the silyl group
was previously bonded.18 Though efficient C–Si bond cleavage
occurred under scH2O, supercritical conditions are not neces-
sarily required for the C–Si bond cleavage for these reactive
organosilicon compounds. For example,ꢁ1 did undergo C–Si
bond cleavage in subcritical water (350 C).
HI
3 (0.045 mmol)
4 (0.045 mmol)
3 (0.025 mmol)
4 (0.014 mmol)
n-C10H21
ð6Þ
+
C6D6
rt, 15 h
(0.050 mmol)
Alkenylsilanes. Encouraged by these promising results,
we next examined alkenylsilanes. The reactions were conduct-
ed directly in a stainless-steel container (method A in Fig. 2),
because an unavoidable explosion occurs during breakage of
the quartz ampoule with method B. When alkenylsilane (3)
was subjected to scH2O (390 ꢁC, 30 min), efficient C–Si bond
cleavage occurred to give a mixture of dodecenes in 71% yield
(Eq. 4).
which clearly implicates that 4 is more reactive than 3 under
typical desilylation conditions. Under these conditions, the iso-
merization of 1-dodecene to other dodecenes was not ob-
served. Therefore, the results demonstrated herein imply a
unique desilylation in scH2O, though the elucidation of mech-
anistic origin must await further investigations.
Alkylsilanes with Heteroatom on Silicon. Having estab-
lished the rapid C–Si bond cleavage of somewhat reactive or-
ganosilicon compounds (arylsilanes, alkenylsilanes, and allylic
silanes), we next examined the reactions of alkylsilanes, which
are known to be much less reactive toward C–Si bond cleavage
than the organosilanes mentioned before.12 Thus, we began by
investigating alkylsilanes having a heteroatom on silicon, since
such a heteroatom allows the activation of alkylsilanes by a
nucleophile, such as a fluoride ion, to achieve otherwise diffi-
cult C–Si bond functionalizations.22
scH2O
n-C10H21
ð4Þ
n-C10H21
SiMe3
390 °C, 27 MPa
3
+ other dodecenes
reaction time
yield
1-dodecene/other dodecenes
1 min
5 min
30 min
31%
67%
71%
84/16
19/81
6/94
Alkylsilanol 5 was our first choice in this investigation
(Table 1). Under the supercritical conditions (380 ꢁC, 3 h), al-
kylsilanol 5 underwent efficient C–Si bond cleavage in water,
giving dodecane in 68% yield (entry 1). Raising the tempera-
ture (390–410 ꢁC) had little effect on the product yield (entries
2–4). However, the desilylation was extremely sluggish at 350
ꢁC (subcritical conditions) and the corresponding siloxane 9
was obtained in 30% yield (entry 5). When the reaction time
was shortened (20, 10, and 5 min), the conversion of 5 was de-
creased (entries 6–8). In the reaction mixture of these reac-
tions, siloxane 9 was obtained in considerable yields (3–
32%). The use of D2Oꢁin place of H2O also resulted in C–Si
bond cleavage at 390 C with the introduction of deuterium
(>95% D) at the position where the silyl group had been pre-
viously bonded (entry 9). Interestingly, it was found that the
addition of HCl (1.0 equiv to 5) had a beneficial effect on
the C–Si bond cleavage, giving dodecane in 88% yield at
The expected 1-dodecence was obtained only in small
amounts. The initial desilylation product (1-dodecene) seemed
to isomerize into thermodynamically more stable inner alkenes
under the reaction conditions. Indeed, isomerization into inner
alkenes was observed when 1-dodecene was subjected to
ꢁ
scH2O at 390 C (ratio of 1-dodecene and other dodecenes:
76/24 after 5 min; 4/96 after 180 min). In line with these
results, when the reactions of 3 were performed in a shorter
reaction time (5 min and 1 min), the ratio of 1-dodecene and
other dodecenes increased to 19/81 and 84/16, respectively
(Eq. 4).
Allylic Silanes. Allylic silanes, another class of reactive
organosilicon compounds, were also investigated. Because
the reaction using these substrates also resulted in an unavoid-
able explosion during breakage of the quartz ampoule with
method B, the reactions were conducted directly in a stain-
less-steel container (method A). Similarly to alkenylsilane 3,
allylic silane 4 also underwent rapid C–Si bond cleavage in
scH2O (Eq. 5).
ꢁ
390 C (entry 10). However, the addition of excess HCl (2.0
equiv to 5) did not cause a further increase in the yield (entry
11). The addition of HCl also had a dramatic enhancement of
ꢁ
scH2O
C–Si bond cleavage in subcritical water (350 C), giving do-
ð5Þ
n-C10H21
n-C9H19
SiMe3
390 °C, 27 MPa
decane in 93% yield (entry 12). Moreover, in addition to
HCl, NaOH was also found to promote the C–Si bond cleavage
of 5 in scH2O (entry 13). However, the addition of NaCl had
little effect on the product yield (entry 14). With these interest-
ing C–Si bond cleavage reactions of alkylsilanol 5 in hand, we
next examined the reaction in supercritical methanol. When 5
was subjected to supercritical methanol, no C–Si bond cleav-
age occurred, and only the corresponding methoxysilane was
obtained in 53% yield (entry 15).
4
+ other dodecenes
reaction time
yield
1-dodecene/other dodecenes
5 min
55%
79%
>95/5
83/17
30 min
In this case, 1-dodecene was found to be a major product (83%
selectivity), even after 30 min. When the reaction time was
shortened to 5 min, the ratio of 1-dodecene and other dode-

2074 Bull. Chem. Soc. Jpn., 77, No. 11 (2004)
Table 1. C–Si Bond Cleavage of Alkylsilanol 5 under Various Conditions
C–Si Bond Cleavage in Supercritical Water
n-C12H25SiMe2OH
n-C12H26
5
Entry
Medium
T/ꢁC
Time/min
Additive (equiv)
Conv/%a)
Yield/%a)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
D2O
H2O
H2O
H2O
H2O
H2O
MeOH
380
390
400
410
350
390
390
390
390
390
390
350
390
390
390
180
180
180
180
180
20
—
—
—
—
—
—
—
—
100
100
100
100
70
83
68
55
100
100
100
100
100
100
100
68
68
67
66
11b)
30c)
20d)
12e)
54f)
88
10
5
180
180
180
180
180
180
180
—
HCl (1.0)
HCl (2.0)
HCl (1.0)
NaOH (1.0)
NaCl (1.0)
—
88
93
85
64
0g)
a) Determined by GC analysis using tetradecane as an internal standard. b) 9 was obtained in 30%. c) 9
was obtained in 3%. d) 9 was obtained in 16%. e) 9 was obtained in 32%. f) Deuterium incorporation
was estimated to be greater than 95% as judged by NMR analysis. g) C12H25SiMe2OMe was obtained
in 53%.
Table 2. C–Si Bond Cleavage of Alkylsilanes with Heteroatom on Silicon
scH2O
n-C12H25SiMe2X
n-C12H26
390 °C, 3 h
Entry
X
Additive (equiv)
Conv/%a)
Yield/%a)
1
2
3
4
5
6
7
Cl (7)
OEt (8)
OEt (8)
OSiMe2C12H25 (9)
OSiMe2C12H25 (9)
SiMe3 (10)
—
—
HCl (1.0)
—
HCl (1.0)
—
HCl (1.0)
100
100
100
100
100
100
100
89
23
72
46
88
56
91
SiMe3 (10)
a) Determined by GC analysis using tetradecane as an internal standard.
In addition to the primary alkyl–silyl bond, a secondary
alkyl–silyl bond of alkylsilanol was also cleaved in scH2O.
Thus, when 6 was subjected in scH2O (390 C, 27 MPa) for
3 h, a desilylation product (dodecane) was obtained in 55%
yield (Eq. 7).
lylation was less efficient when ethoxysilane 8, siloxane 9, and
disilane 10 were used (entries 2, 4, and 6). However, the addi-
tion of HCl gave rise to higher yields of the desilylation prod-
ucts (entries 3, 5, and 7).
ꢁ
During these studies, we found an interesting reactivity of
alkylsilane 11 that has a Si–H bond in scH2O. When alkyl-
Me
ꢁ
scH2O
silane 11 was subjected to scH2O (390 C, 30 min), alkylsila-
nol 5 (50%) and its dimer 9 (18%) were found in the reaction
mixture together with dodecane (Eq. 8).
n-C12H26
ð7Þ
n-C10H21
SiMe2OH
390 °C, 27 MPa
3 h
55%
6
n-C12H26
The efficiency was somewhat lower than the corresponding
primary alkyl–silyl bond (Table 1, entry 2).
(12%)
scH2O
5 (50%)
9 (18%)
n-C12H25SiMe2OH
(n-C12H25SiMe2)2O
ð8Þ
n-C12H25SiMe2H
390 °C, 27 MPa
Having established the efficient C–Si bond cleavage of
alkylsilanols in scH2O, we subsequently examined other alkyl-
silanes with heteroatom on silicon (Table 2). All reactions
11
30 min
ꢁ
When the reaction was carried out in 380 C for 1 h, alkyl-
silanol 5 became the exclusive product (Eq. 9).
ꢁ
were carried out at 390 C for 3 h. The reaction using chloro-
silane 7 gave dodecane in 89% yield (entry 1). The higher
yield, as compared to that with the corresponding alkylsilanol
5 (Table 1, entry 2), may be due to the effect of HCl generated
in situ. Compared with alkylsilanol and chlorosilane, the desi-
scH2O
n-C12H25SiMe2H
n-C12H25SiMe2OH
5 (72%)
ð9Þ
380 °C, 24 MPa
11
1 h

K. Itami et al.
Bull. Chem. Soc. Jpn., 77, No. 11 (2004) 2075
Since the reactions were performed under oxygen-free condi-
tions (the quartz ampoule was flame sealed after three
freeze–pump–thaw cycles), the present transformation most
likely proceeded through hydrolysis of the Si–H bond.23 This
may be an interesting alternative to the existing Si–H to Si–
OH transformations, since it does not require any oxidants24
or metal catalysts.25 It is noteworthy that this method does
not suffer from the production of disiloxane, which has often
been a bane in the existing synthetic methods of silanol.
Tetraalkylsilanes. The successful desilylation of function-
alized alkylsilanes finally led us to the ultimate challenge, the
C–Si bond cleavage of unactivated tetraalkylsilanes. It has
been stated by Armitage in his comprehensive review that
‘‘Tetraalkylsilanes are remarkably stable compounds. The sil-
icon–carbon bond is strong and almost non-polar. It is there-
fore only broken under the most vigorous conditions, unless
assisted by an alkyl group possessing an activating substituent
suitably placed.’’26 Therefore, the cleavage of the C–Si bonds
in robust tetraalkylsilanes has been a subject of great interest in
organic chemistry. Previously, strong acids,27–29 bases,30,31 or
metal salts32–43 were required to accomplish the C–Si bond
cleavage of unactivated tetraalkylsilanes.44,45
(entries 4 and 5) or in supercritical methanol (entry 6).
The effect of substituents on silicon was subsequently ex-
amined (Table 4). The desilylation of secondary alkylsilane
ꢁ
13 was less efficient (1%) at 390 C (entry 3). This may be
due to the steric hindrance around the silicon atom. The same
tendency was observed when Et3Si and i-Pr3Si groups were at-
tached in place of the Me3Si group (entries 5 and 7). Such a
considerable reactivity difference may be useful for selective
desilylation from a compound bearing several different silyl
groups. However, in all cases, the addition of HCl again accel-
erated the cleavage of these sterically hindered C–Si bonds,
and the reactions completed within 30 min (entries 4, 6, and 8).
When tetra(1-dodecyl)silane (16) was used as a substrate,
368% of 1-dodecane was fꢁormed under the influence of HCl
(1.0 equiv) in scH2O (390 C, 30 min) (Eq. 10).
scH2O
ð10Þ
(n-C12H25)4Si
n-C12H26
390 °C, 0.5 h
1 equiv HCl
16
368%
This result unambiguously verifies that all C–Si bonds of tet-
raalkylsilanes are cleaved in scH2O.
We next examined the effect of several other additives in
the reaction of tetraalkylsilanes 14 in scH2O (Table 5). As al-
ready mentioned, the addition of 1.0 equiv of HCl gave rise to
the production of dodecane in 79% yield (entry 2). Reducing
the amount (0.1 equiv) of HCl resulted in a somewhat lower
yield of dodecane (65%, entry 3). Other acids, such as HBr
and H2SO4, also promoted C–Si bond cleavage, giving dodec-
ane in high yields (93% and 75% yields, respectively). Inter-
Beyond our imagination, this transformation was found to
be extremely rapid in scH2O (Table 3). Primary alkyltrime-
thylsꢁilane 12 underwent expeditious C–Si bond cleavage at
390 C within 30 min giving dodecane in 72% yield (entry
1).46 By adding HCl, we increased the yield to 88% (entry
2). The desilylation was extremely inefficient in subcritical
water (entry 3), or entirely sluggish in refluxing HCl/H2O
Table 3. C–Si Bond Cleavage of Tetraalkylsilane 12 under Various Conditions
n-C12H25SiMe3
n-C12H26
12
Entry
Medium
T/ꢁC
Time/h
Additive (equiv)
Conv/%a)
Yield/%a)
1
2
3
4
5
6
H2O
H2O
H2O
H2O
H2O
MeOH
390
390
350
110
110
390
0.5
0.5
0.5
14
14
0.5
—
HCl (1.0)
—
—
HCl (1.0)
—
100
100
35
3
4
20
72
88
11b)
0
0
1
a) Determined by GC analysis using tetradecane as an internal standard. b) 5 was obtained
in 9%.
Table 4. Effect of Substituents on Silicon
scH2O
C12H25SiR3
C12H26
390 °C, 0.5 h
Additive (equiv)
Entry
Silane
Conv/%a)
Yield/%a)
1
2
3
4
5
6
7
8
n-C12H25SiMe3 (12)
12
n-C10H21CH(CH3)SiMe3 (13)
13
n-C12H25SiEt3 (14)
14
n-C12H25Si(i-Pr)3 (15)
15
—
HCl (1.0)
—
HCl (1.0)
—
HCl (1.0)
—
HCl (1.0)
100
100
8
100
11
100
9
100
72
88
1
74
4
79
2
80
a) Determined by GC analysis using tetradecane as an internal standard.

2076 Bull. Chem. Soc. Jpn., 77, No. 11 (2004)
C–Si Bond Cleavage in Supercritical Water
Table 5. Effect of Additive in C–Si Bond Cleavage of Tetraalkylsilanes
scH2O
n-C12H25SiR3
n-C12H26
390 °C, 0.5 h
additive
12: R = Me
14: R = Et
Entry
Silane
Additive (equiv)
Conv/%a)
Yield/%a)
1
2
3
4
5
6
7
8
9
14
14
14
14
14
14
12
12
12
—
11
100
100
100
100
4
100
83
81
4
79
65
93
75
1
72
58b)
33c)
HCl (1.0)
HCl (0.1)
HBr (1.0)
H2SO4 (1.0)
NaOH (1.0)
—
NaOH (1.0)
MeOH (1.0)
a) Determined by GC analysis using tetradecane as an internal standard. b) Silanol 5
was obtained in 12%. c) Silanol 5 was obtained in 4%.
Acetonitrile (CH3CN) and triethylamine (Et3N) were distilled
estingly, however, NaOH (1.0 equiv) did not exhibit any pro-
moting effect (entry 6). Rather, we found that NaOH actually
inhibits C–Si bond cleavage in scH2O through control experi-
ments using 12 as a substrate (entries 7 and 8). These results
are in sharp contrast with those obtained in reactions using al-
kylsilanol 5 (Table 1, entries 1 and 13). We also found an in-
hibiting effect of MeOH (1.0 equiv) in C–Si bond cleavage
(entry 9).
over CaH2. N,N-Dimethylformamide (DMF) was distilled over
P2O5. Ethyl acetate (EtOAc) was distilled over K2CO3. Caution-
ary Notes: Although we have never experienced an accident, all
reactions in supercritical water should be performed with great
care due to the high temperature/pressure conditions.
Typical Procedure for the Reaction of Organosilicon Com-
pounds in Supercritical Water (Method B, Fig. 2). Unless oth-
erwise noted, all reactions were performed in a quartz ampoule
placed in a stainless-steel tube container in order to avoid any in-
fluence of a stainless reactor (Houser’s technique).17 Quartz am-
poules (inside diameter: 4.5 mm; thickness: 0.7 mm) of approxi-
mately 3 mL in total volume were used as the reactor vessels.
An ampoule was filled with 0.1 mmol of organosilicon compound
and 420 mg of water. After three freeze–pump–thaw cycles, the
ampoule was immediately flame sealed and placed in a SUS316
stainless-steel tube (volume: 11.85 mL; lengh: 145 mm; outside
diameter: 12.7 mm). The stainless tube was used as a container
to hold the ampoule during heating. To avoid breakage of the
quartz ampoule due to a pressure increase, a calculated amount
of water was added to the stainless tube to maintain a balanced
pressure. The temperature was monitored by a thermocouple in-
serted through the top end of the stainless-tube container. The
stainless tube was submerged in a dissolved salt bath (NaNO2/
KNO3), whose temperature was controlled. After a specified time,
the tube was removed and cooled in an ice bath. The reaction
products were analyzed by standard methods, such as capillary
GC, GC–MS, and NMR. As for the silicon-containing product,
we observed the formation of silica-like solid after the reactions,
although it has not yet been identified.
Conclusion
In conclusion, it was found that arylsilanes, alkenylsilanes,
allylic silanes, and alkylsilanes undergo extremely facile and
rapid C–Si bond cleavage in supercritical water. The rapid
C–Si bond cleavage occurred even with robust unactivated tet-
raalkylsilanes. Control experiments revealed a dramatic differ-
ence between the supercritical and subcritical conditions, and
that between supercritical water and supercritical methanol, at-
testing to a unique reactivity of supercritical water in C–Si
bond cleavage. It is noteworthy that acids such as HCl, HBr,
and H2SO4 promote C–Si bond cleavage in supercritical water.
During this study, we also found the facile conversion of hy-
drosilane to silanol in supercritical water. Although further in-
vestigations are clearly needed to elucidate the mechanism of
C–Si bond cleavage, the results demonstrated herein imply a
unique desilylation in supercritical water, which might be use-
ful not only in organic synthesis, but also in material manufac-
turing.
Experimental
General. 1H and 13C NMR spectra were recorded on Varian
GEMINI-2000 (1H 300 MHz, 13C 75 MHz) and JEOL A-500
(1H 500 MHz, 13C 125 MHz) spectrometers in CDCl3 with chem-
ical shifts referenced to internal standards (7.26 ppm 1H, 77.0
ppm 13C). EI and CI mass spectra were recorded on a JMS-
SX102A spectrometer. FAB mass spectra were recorded on a
JMS-HX110A spectrometer. Infrared spectra were recorded on
Shimadzu FTIR-8100 spectrophotometer. Gel permeation chro-
matography was carried out with Japan Analytical Industry LC-
918. Unless otherwise noted, all materials, anhydrous tetrahydro-
furan (THF), and anhydrous diethyl ether (Et2O) were obtained
from commercial suppliers and used without further purification.
Reactions using 3 and 4 were carried out directly in the stain-
less reactor (method A, Fig. 2).
Procedure for Competitive Protodesilylation of 3 and 4 in
Organic Solvent (Eq. 6).
To a mixture of alkenylsilane 3
(10.8 mg, 0.045 mmol), allylic silane 4 (10.8 mg, 0.045 mmol),
and toluene (internal standard, 7.8 mg, 0.085 mmol) in C6D6
(0.6 mL) was added a drop of HI at room temperature. The result-
1
ant mixture was monitored by H NMR. 1-Dodecene was formed
in 0.050 mmol after standing the mixture for 15 h; 56% (0.025
mmol) of alkenylsilane 3 and 32% (0.014 mmol) of allylic silane
4 remained unchanged. The isomerization of 1-dodecene to other
dodecenes was not observed under these conditions.

K. Itami et al.
Bull. Chem. Soc. Jpn., 77, No. 11 (2004) 2077
(4-Butylphenyl)trimethylsilane (2). To a solution of 1,4-di-
bromobenzene (12.76 g, 50.0 mmol) in Et2O (100 mL) was added
a solution of BuLi (50.0 mmol, 1.53 M) in hexane at ꢂ78 ꢁC and
the reaction mixture was stirred at ꢂ78 ꢁC for 4 h. To this mixture
To a solution of dodec-1-en-3-ol (9.22 g, 50.0 mmol), triethyl-
amine (6.07 g, 60.0 mmol), and 4-(dimethylamino)pyridine (619
mg, 5.07 mmol) in CH2Cl2 (50 mL) was added trifluoroacetic an-
ꢁ
hydride (13.01 g, 61.9 mmol) at 0 C. After the mixture was stir-
ꢁ
was added chlorotrimethylsilane (6.18 g, 56.8 mmol) at ꢂ78 C
red at 0 ꢁC for 2 h, and then at room temperature for 2 h, H2O was
added to the mixture, and the organic phase was separated. The
aqueous phase was extracted with CH2Cl2 (four times). The com-
bined organic phase was dried over MgSO4. Removal of the sol-
vents under reduced pressure and subsequent distillation afforded
3-trifluoroacetoxy-1-dodecene (11.40 g, 81%) as a colorless liq-
uid: bp 69 ꢁC/1.1 mmHg. 1H NMR (300 MHz) ꢀ 0.88 (t, J ¼
6:9 Hz, 3H), 1.15–1.40 (m, 14H), 1.60–1.85 (m, 2H), 5.29 (d, J ¼
10:5 Hz, 1H), 5.35 (d, J ¼ 17:4 Hz, 1H), 5.37 (q, J ¼ 6:9 Hz, 1H),
5.80 (ddd, J ¼ 17:4, 10.5, 6.9 Hz, 1H).
and the reaction mixture was stirred for 10 min. After the mixture
was stirred at room temperature for 2 h, H2O was added to the
mixture, and the organic phase was separated. The aqueous phase
was extracted with Et2O (three times) and the combined organic
phase was washed with brine. Drying over MgSO4 and removal
of the solvents under reduced pressure afforded (4-bromophenyl)-
trimethylsilane quantitatively.
To a solution of (4-bromophenyl)trimethylsilane (5.63 g, 24.7
mmol) in THF (50 mL) was added a solution of BuLi (29.6 mmol,
1.53 M) in hexane at room temperature. After the mixture was
stirred at room temperature for 2 h, H2O was added to the mixture,
and the organic phase was separated. The aqueous phase was ex-
tracted with Et2O (three times) and the combined organic phase
was dried over MgSO4. Removal of the solvents under reduced
pressure and subsequent distillation afforded 2 (3.04 g, 60%) as
A solution of [Pd(dba)2] (345 mg, 0.60 mmol, 3 mol%), hexa-
methyldisilane (5.85 g, 40.0 mmol), and 3-trifluoroacetoxy-1-do-
decene (5.63 g, 20.1 mmol) in THF (110 mL) was stirred at room
temperature for 6 h. The removal of the solvents under reduced
pressure and subsequent distillation afforded 4 (4.20 g, 87%,
E=Z ¼ 92=8) as colorless liquid: bp 85–86 ꢁC/0.8 mmHg.
1H NMR (300 MHz) ꢀ ꢂ0:02 (s, 9H), 0.88 (t, J ¼ 6:9 Hz, 3H),
1.20–1.35 (m, 14H), 1.39 (d, J ¼ 7:5 Hz, 2H), 1.96 (q, J ¼ 6:9
Hz, 2H), 5.23 (dt, J ¼ 15:1, 6.9 Hz, 1H), 5.36 (dt, J ¼ 15:1, 7.5
Hz, 1H). 13C NMR (75 MHz) ꢀ ꢂ2:0, 14.1, 22.6, 22.7, 29.1,
29.4, 29.5, 29.6, 30.0, 31.9, 32.8, 125.9, 129.0. HRMS (EI) m=z
calcd for C15H32Si: 240.2273, found 240.2273.
1-Dodecyldimethylsilanol (5). Compound 5 was prepared us-
ing a procedure developed by Chang.49 The mixture of 11 (6.23 g,
27.3 mmol), [RuCl2(p-cymene)]2 (334 mg, 0.55 mmol, 2 mol%),
and H2O (970 mg, 54.5 mmol) in CH3CN (82 mL) was stirred at
room temperature for 4 h under air. Removal of the solvents under
reduced pressure and subsequent distillation afforded 5 (3.97 g,
60%) as a colorless liquid: bp 109 ꢁC/0.8 mmHg. 1H NMR
(300 MHz) ꢀ 0.12 (s, 6H), 0.55–0.63 (m, 2H), 0.88 (t, J ¼ 6:9
Hz, 3H), 1.20–1.40 (m, 21H). 13C NMR (125 MHz) ꢀ ꢂ0:3,
14.1, 17.8, 22.7, 23.1, 29.36, 29.38, 29.58, 29.65, 29.68, 29.7,
31.9, 33.4. HRMS (CI) m=z calcd for C14H33OSi [M þ H]:
245.2301, found 245.2293.
2-Dodecyldimethylsilanol (6). To a suspension of Mg (244.3
mg, 10.0 mmol) in Et2O (4 mL) was added a solution of 2-bromo-
dodecane (2.51 g, 10.1 mmol) in Et2O (2 mL) at room tempera-
ture. The reaction mixture was stirred for 2 h, and chlorodimethyl-
silane (1.27 g, 13.5 mmol) was added to the mixture at room tem-
perature. After stirring the mixture at room temperature for 14 h,
H2O was added to the mixture, and the organic phase was separat-
ed. The organic phase was washed with brine. The aqueous phase
was extracted with Et2O (three times) and the combined organic
phase was dried over MgSO4. Removal of the solvents under re-
duced pressure and subsequent distillation afforded 2-dodecyldi-
methylsilane (1.52 g, 66%) as colorless liquid: bp 96 ꢁC/1.5
mmHg. 1H NMR (300 MHz) ꢀ 0.03 (d, J ¼ 3:6 Hz, 3H), 0.04
(d, J ¼ 3:6 Hz, 3H), 0.65–0.80 (m, 1H), 0.88 (t, J ¼ 6:9 Hz,
3H), 0.94 (d, J ¼ 7:2 Hz, 3H), 1.15–1.35 (br, 16H), 1.35–1.50
(m, 2H), 3.70–3.80 (m, 1H).
A mixture of 2-dodecyldimethylsilane (728.2 mg, 3.19 mmol),
[RuCl2(p-cymene)]2 (36.7 mg, 0.06 mmol, 2 mol%), and H2O
(114.4 mg, 6.35 mmol) in CH3CN (10 mL) was stirred at room
temperature for 5 h under air. Removal of the solvents under re-
duced pressure and subsequent silica-gel chromatography afforded
6 (642.4 mg, 82%) as colorless oil. 1H NMR (300 MHz) ꢀ 0.10 (s,
6H), 0.60–0.75 (m, 1H), 0.88 (t, J ¼ 7:2 Hz, 3H), 0.95 (d, J ¼ 7:2
Hz, 3H), 1.20–1.35 (m, 16H), 1.40–1.50 (m, 3H). 13C NMR (125
ꢁ
1
a colorless liquid: bp 136 C/27 mmHg. H NMR (300 MHz) ꢀ
0.25 (s, 9H), 0.93 (t, J ¼ 7:5 Hz, 3H), 1.30–1.45 (m, 2H), 1.55–
1.65 (m, 2H), 2.60 (t, J ¼ 7:5 Hz, 2H), 7.19 (d, J ¼ 7:8 Hz,
2H), 7.44 (d, J ¼ 7:8 Hz, 2H). 13C NMR (75 MHz) ꢀ ꢂ1:1,
14.0, 22.4, 33.6, 35.6, 127.9, 133.3, 137.0, 143.6. HRMS (EI)
m=z calcd for C13H22Si: 206.1491, found 206.1493. Anal. Calcd
for C13H22Si: C, 75.65; H, 10.74%. Found: C, 75.95; H, 10.84%.
(E)-1-Dodecenyltrimethylsilane (3). Compound 3 was pre-
pared using a procedure developed by Chan.47 To a suspension
of KOBut (8.41 g, 74.9 mmol) in hexane (40 mL) was added a so-
lution of BuLi (75.0 mmol, 1.57 M) in hexane at 0 ꢁC, and the
ꢁ
mixture was stirred at 0 C for 10 min and at room temperature
for 35 min. To this mixture were added Et2ꢁO (50 mL) and allyl-
trimethylsilane (8.70 g, 76.1 mmol) at ꢂ78 C. After the mixture
was stirred at 0 ꢁC for 1 h, a solution of 1-bromononane (15.63 g,
75.4 mmol) in Et2O (20 mL) was added to the mixture at ꢂ78 ꢁC.
After the mixture was stirred at room temperature for 14 h, H2O
was added to the mixture and the organic phase was separated.
The organic phase was washed with aq Na2S2O3 solution. Drying
over MgSO4 and removal of the solvents under reduced pressure
afforded 3 (8.69 g, 48%) as a colorless liquid: 1H NMR (300
MHz) ꢀ 0.04 (s, 9H), 0.88 (t, J ¼ 6:9 Hz, 3H), 1.20–1.45 (m,
16H), 2.09 (td, J ¼ 6:9, 6.3 Hz, 2H), 5.61 (dt, J ¼ 18:3, 1.5 Hz,
1H), 6.02 (dt, J ¼ 18:3, 6.3 Hz, 1H). 13C NMR (125 MHz) ꢀ
ꢂ1:1, 14.1, 22.7, 28.7, 29.2, 29.4, 29.5, 29.63, 29.64, 31.9, 36.8,
129.4, 147.4. HRMS (EI) m=z calcd for C15H32Si: 240.2273,
found 240.2274. Anal. Calcd for C15H32Si: C, 74.91; H,
13.41%. Found: C, 74.61; H, 13.70%.
2-Dodecenyltrimethylsilane (4). Compound 4 was prepared
using a procedure developed by Tsuji.48 To a solution of vinyl-
magnesium bromide (60.0 mmol, 1.0 M) in THF was added dec-
anal (7.86 g, 50.3 mmol) at 0 ꢁC. After the mixture was stirred at 0
ꢁC for 1 h and then at room temperature for 66 h, an aq HCl solu-
tion was added to the mixture, and the organic phase was separat-
ed. The aqueous phase was extracted with Et2O (four times). The
combined organic phase was dried over MgSO4. Removal of the
solvents under reduced pressure and subsequent distillation afford-
ꢁ
ed dodec-1-en-3-ol (7.92 g, 86%) as a colorless liquid: bp 82 C/
1.2 mmHg. 1H NMR (300 MHz) ꢀ 0.88 (t, J ¼ 6:9 Hz, 3H), 1.15–
1.40 (m, 14H), 1.45–1.60 (m, 3H), 4.09 (qt, J ¼ 6:6, 1.2 Hz, 1H),
5.10 (dt, J ¼ 10:5, 1.5 Hz, 1H), 5.22 (dt, J ¼ 17:1, 1.5 Hz, 1H),
5.87 (ddd, J ¼ 17:1, 10.5, 6.6 Hz, 1H).

2078 Bull. Chem. Soc. Jpn., 77, No. 11 (2004)
C–Si Bond Cleavage in Supercritical Water
MHz) ꢀ ꢂ2:1, ꢂ2:0, 13.4, 14.1, 20.9, 22.7, 28.6, 29.3, 29.6 (two
carbons), 29.7, 29.8, 31.1, 31.9. HRMS (EI) m=z calcd for
C14H32OSi: 244.2222, found 244.2223.
1-Dodecyldimethylsilane (11). To a suspension of Li (596
mg, 85.2 mmol) in Et2O (20 mL) was added a solution oꢁf 1-bro-
mododecane (10.63 g, 42.6 mmol) in Et2O (30 mL) at 0 C. The
reaction mixture was stirred for 4 h, and chlorodimethylsilane
Chloro(1-dodecyl)dimethylsilane (7). To a solution of di-
chlorodimethylsilane (21.4 g, 165.8 mmol) in THF (40 mL) was
added a solution of 1-dodecylmagnesium bromide (78 mmol,
1.56 M) in THF at room temperature. After stirring the mixture
at room temperature for 16 h, hexane (60 mL) was added to the
mixture. Filtration through CeliteÒ, removal of the solvents under
reduced pressure, and distillation afforded 7 (17.6 g, 86%) as a
ꢁ
(4.34 g, 45.9 mmol) was added to the mixture at 0 C. After stir-
ring the mixture at room temperature for 14 h, H2O was added to
the mixture and the organic phase was separated. The organic
phase was washed with brine. The aqueous phase was extracted
with Et2O (three times) and the combined organic phase was dried
over MgSO4. Removal of the solvents under reduced pressure and
subsequent diꢁstillation afforded 11 (6.24 g, 64%) as a colorless
ꢁ
1
colorless liquid: bp 105 C/0.25 mmHg. H NMR (300 MHz) ꢀ
0.40 (s, 6H), 0.75–0.85 (m, 2H), 0.88 (t, J ¼ 6:9 Hz, 3H), 1.20–
1.45 (m, 20H). 13C NMR (125 MHz) ꢀ 1.7, 14.1, 19.0, 22.7,
23.0, 29.3, 29.4, 29.5, 29.66, 29.68, 29.69, 31.9, 33.0. HRMS
(EI) m=z calcd for C14H31ClSi: 262.1884, found 262.1885.
1-Dodecyl(ethoxy)dimethylsilane (8). To a solution of imid-
azole (1.71 g, 25.2 mmol) and ethanol (1.18 g, 25.6 mmol) in
DMF (45 mL) was added 7 (6.67 g, 25.4 mmol) at 0 ꢁC. After stir-
ring the mixture at room temperature for 19 h, brine was added to
the mixture and the organic phase was separated. The aqueous
phase was extracted with Et2O (three times), and the combined or-
ganic phase was dried over MgSO4. Removal of the solvents un-
der reduced pressure and subsequent distillation afforded 8 (3.97
g, 57%) as colorless liquid: bp 102 ꢁC/1.1 mmHg. 1H NMR
(300 MHz) ꢀ 0.08 (s, 6H), 0.50–0.62 (m, 2H), 0.87 (t, J ¼ 6:6
Hz, 3H), 1.18 (t, J ¼ 7:2 Hz, 3H), 1.20–1.40 (m, 20H), 3.65 (q,
J ¼ 7:2 Hz, 2H). 13C NMR (125 MHz) ꢀ ꢂ2:1, 14.1, 16.4, 18.5,
22.7, 23.2, 29.4 (two carbons), 29.59, 29.66, 29.69, 29.71, 31.9,
33.5, 58.2. IR (neat) 2957, 2924, 2855, 1466, 1458, 1250, 1109,
1082, 947, 839, 779 cmꢂ1. HRMS (CI) m=z calcd for C16H37OSi
[M þ H]: 273.2614, found 273.2614.
1
liquid: bp 84 C/0.8 mmHg. H NMR (300 MHz) ꢀ 0.05 (d, J ¼
3:6 Hz, 6H), 0.50–0.62 (m, 2H), 0.88 (t, J ¼ 6:9 Hz, 3H), 1.20–
1.40 (m, 20H), 3.83 (heptet, J ¼ 3:6 Hz, 1H). 13C NMR (125
MHz) ꢀ ꢂ4:4, 14.1, 14.2, 22.7, 24.4, 29.38, 29.40, 29.60, 29.67,
29.70, 29.72, 31.9, 33.3. HRMS (EI) m=z calcd for C14H31Si
[M ꢂ H]: 227.2195, found 227.2200.
1-Dodecyltrimethylsilane (12). To a suspension of Li (418
mg, 60.2 mmol) in Et2O (10 mL) was added a solution of 1-bro-
mododecane (7.63 g, 30.6 mmol) in Et2O (10 mL) at 0 ꢁC, and the
mixture was stirred at 0 ꢁC for 2 h. Chlorotrimethylsilane (3.80 g,
35.0 mmol) was then added to the reaction mixture at 0 ꢁC. After
stirring the mixture at room temperature for 10 h, H2O was added
to the reaction mixture and the organic phase was separated. The
aqueous phase was extracted with Et2O (three times) and the com-
bined organic phase was dried over Na2SO4. Removal of the sol-
vents under reduced pressure and subsequent distillation afforded
12 (2.28 g, 31%) as a colorless liquid: bp 86 ꢁC/1.0 mmHg.
1H NMR (300 MHz) ꢀ ꢂ0:04 (s, 9H), 0.42–0.50 (m, 2H), 0.88
(t, J ¼ 6:9 Hz, 3H), 1.20–1.35 (m, 20H). 13C NMR (75 MHz) ꢀ
ꢂ1:6, 14.1, 16.7, 22.7, 23.9, 29.39, 29.43, 29.64, 29.67, 29.70,
29.74, 31.9, 33.7. HRMS (EI) m=z calcd for C14H31Si
[M ꢂ Me]: 227.2195, found 227.2197. Anal. Calcd for C15H34Si:
C, 74.29; H, 14.13%. Found: C, 74.45; H, 14.26%.
1,3-Di(1-dodecyl)-1,1,3,3-tetramethyldisiloxane (9).
To a
solution of 5 (717 mg, 2.93 mmol) and triethylamine (296 mg,
2.93 mmol) in EtOAc (3 mL) was added 7 (828 mg, 2.93 mmol)
at room temperature. After stirring the mixture at room tempera-
ture for 22 h, H2O was added to the mixture and organic phase
was separated. The aqueous phase was extracted with Et2O (five
times) and the combined organic phase was dried over MgSO4.
Removal of the solvents under reduced pressure and subsequent
silica-gel chromatography (hexane) afforded 9 (1.13 g, 82%) as
colorless oil: 1H NMR (300 MHz) ꢀ 0.02 (s, 12H), 0.45–0.55
(m, 4H), 0.88 (t, J ¼ 6:9 Hz, 6H), 1.20–1.35 (m, 40H). 13C NMR
(125 MHz) ꢀ 0.4, 14.1, 18.4, 22.7, 23.3, 29.40, 29.45, 29.65,
29.70, 29.74, 29.76, 32.0, 33.5. HRMS (CI) m=z calcd for
C28H63OSi2 [M þ H]: 471.4417, found 471.4423.
2-Dodecyltrimethylsilane (13). To a suspension of Mg (246
mg, 10.1 mmol) in THF (3 mL) were added a few drops of 1,2-di-
bromoethane, and then a solution of 2-bromododecane (2.49 g,
10.0 mmol) in THF (3 mL) at room temperature and the mixture
was stirred at room temperature for 1 h. Chlorotrimethylsilane
(1.20 g, 11.0 mmol) and CuCN50 (50.2 mg, 0.55 mmol) were then
added to the reaction mixture at 0 ꢁC. After stirring the mixture at
room temperature for 16 h, an aq NaOH solution was added to the
reaction mixture at 0 ꢁC and the organic phase was separated. The
aqueous phase was extracted with Et2O (three times) and the com-
bined organic phase was dried over MgSO4. Removal of the sol-
vents under reduced pressure and subsequent gel permeation chro-
matography afforded 13 (534 mg, 22%) as a colorless liquid:
1H NMR (500 MHz) ꢀ ꢂ0:07 (s, 9H), 0.51–0.58 (m, 1H), 0.87
(t, J ¼ 7:1 Hz, 3H), 0.88 (t, J ¼ 7:3 Hz, 3H), 1.00–1.30 (m,
18H). 13C NMR (125 MHz) ꢀ ꢂ3:2, 14.0, 14.1, 19.5, 22.7, 28.6,
29.4, 29.67, 29.71, 29.75, 29.83, 31.7, 31.9. IR (neat) 2955,
2855, 1489, 1466, 1248, 855, 833, 749, 689 cmꢂ1. HRMS (EI)
m=z calcd for C15H34Si: 242.2430, found 242.2435. Anal. Calcd
for C15H34Si: C, 74.29; H, 14.13%. Found: C, 74.18; H, 13.90%.
1-Dodecyltriethylsilane (14). To a suspension of Li (406 mg,
58.5 mmol) in Et2O (10 mL) was added a solution of 1-bromodo-
decane (7.25 g, 29.1 mmol) in Et2O (10 mL) at 0 ꢁC, and the mix-
1-(1-Dodecyl)-1,1,2,2,2-pentamethyldisilane (10). To a sus-
pension of Mg (609 mg, 25.1 mmol) in Et2O (7 mL) was added a
solutꢁion of 1-bromododecane (6.31 g, 25.3 mmol) in Et2O (6 mL)
at 0 C and the mixture was stirred at room temperature for 4 h.
Chloropentamethyldisilane (4.19 g, 25.1 mmol) was then added
to the reaction mixture at room temperature. After stirring the
mixture at room temperature for 12 h, an aq HCl solution was add-
ed to the reaction mixture, and the organic phase was separated.
The aqueous phase was extracted with Et2O (five times) and the
combined organic phase was dried over MgSO4. Removal of the
solvents under reduced pressure and subsequent distillation afford-
ed 10 (4.10 g, 54%) as colorless liquid: bp 121 ꢁC/1.1 mmHg.
1H NMR (300 MHz) ꢀ 0.01 (s, 6H), 0.04 (s, 9H), 0.50–0.60 (m,
2H), 0.88 (t, J ¼ 7:2 Hz, 3H), 1.20–1.35 (m, 20H). 13C NMR
(125 MHz) ꢀ ꢂ4:3, ꢂ2:0, 14.1, 14.9, 22.7, 24.6, 29.4 (two car-
bons), 29.64, 29.68, 29.71, 29.73, 31.9, 33.8. HRMS (EI) m=z
calcd for C17H40Si2: 300.2669, found 300.2666.
ꢁ
ture was stirred at 0 C for 2 h. Chlorotriethylsilane (4.87 g, 32.3
ꢁ
mmol) was then added to the reaction mixture at 0 C. After stir-
ring the mixture at room temperature for 16 h, H2O was added to
the reaction mixture and the organic phase was separated. The
aqueous phase was extracted with Et2O (three times) and the com-

K. Itami et al.
Bull. Chem. Soc. Jpn., 77, No. 11 (2004) 2079
bined organic phase was dried over MgSO4. Removal of the sol-
vents under reduced pressure and subsequent distillation afforded
14 (5.08 g, 61%) as a colorless liquid: bp 114 ꢁC/1.0 mmHg.
1H NMR (300 MHz) ꢀ 0.45–0.48 (m, 2H), 0.49 (q, J ¼ 7:8 Hz,
6H), 0.88 (t, J ¼ 6:9 Hz, 3H), 0.92 (t, J ¼ 7:8 Hz, 9H), 1.20–
1.30 (m, 20H). 13C NMR (125 MHz) ꢀ 3.4, 7.5, 11.3, 14.1, 22.7,
23.9, 29.4 (two carbons), 29.66, 29.69, 29.73, 29.76, 32.0, 34.0.
HRMS (EI) m=z calcd for C16H35Si [M ꢂ Et]: 255.2508, found
255.2504.
4
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5
Recent examples: a) C. J. Li and W. C. Zhang, J. Am.
Chem. Soc., 120, 9102 (1998). b) S. Otto, J. B. F. N. Engberts,
and J. C. T. Kwak, J. Am. Chem. Soc., 120, 9517 (1998). c) G.
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6
E. Savage, Chem. Rev., 99, 603 (1999). c) D. Broll, C. Kaul, A.
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¨
Zehner, Angew. Chem., Int. Ed., 38, 2998 (1999). d) M. Siskin
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1-Dodecyltriisopropylsilane (15). To a suspension of Li (283
mg, 40.8 mmol) in Et2O (8 mL) was added a solution of 1-bromo-
dodecane (5.08 g, 20.4 mmol) in Et2O (8 mL) at 0 ꢁC, and the
ꢁ
mixture was stirred at 0 C for 3 h. To this mixture were added
triisopropylsilyl triflate (6.87 g, 22.4 mmol) and then hexamethyl-
ꢁ
ꢁ
phosphoramide (8 mL) at 0 C. After stirring the mixture at 0 C
for 2 h, and then at room temperature for 15 h, H2O was added to
the reaction mixture and the organic phase was separated. The
aqueous phase was extracted with Et2O (three times) and the com-
bined organic phase was dried over MgSO4. Filtration through a
short silica gel pad (hexane), removal of the solvents under re-
duced pressure, and subsequent distillation afforded 15 (1.51 g,
23%) as a colorless liquid: bp 132 ꢁC/0.9 mmHg. 1H NMR
(300 MHz) ꢀ 0.50–0.60 (m, 2H), 0.88 (t, J ¼ 6:9 Hz, 3H),
0.95–1.00 (m, 3H), 1.02 (s, 18H), 1.20–1.40 (m, 20H). 13C NMR
(125 MHz) ꢀ 9.4, 11.0, 14.1, 18.9, 22.7, 24.3, 29.3, 29.4, 29.68
(two carbons), 29.73, 29.74, 32.0, 34.5. IR (neat) 2959, 2924,
1464, 884, 733, 693, 656 cmꢂ1. HRMS (EI) m=z calcd for
Reviews: a) O. Kajimoto, Chem. Rev., 99, 355 (1999). b) P.
¨
7
a) M. B. Korzenski and J. W. Kolis, Tetrahedron Lett., 38,
5611 (1997). b) Y. Harano, H. Sato, and F. Hirata, J. Am. Chem.
Soc., 122, 2289 (2000).
8
a) A. R. Katritzky, S. M. Allin, and M. Siskin, Acc. Chem.
Res., 29, 399 (1996). b) K. Chandler, F. Deng, A. K. Dillow, C. L.
Liotta, and C. A. Eckert, Ind. Eng. Chem. Res., 36, 5175 (1997).
i
C18H39Si [M ꢂ Pr]: 283.2821, found 283.2813. Anal. Calcd for
C21H46Si: C, 77.21; H, 14.19%. Found: C, 77.04; H, 14.45%.
Tetra(1-dodecyl)silane (16). To a suspension of Li (304 mg,
43.8 mmol) in Et2O (10 mL) was added a solution of 1-bromodo-
decane (5.51 g, 22.1 mmol) in Et2O (10 mL) at 0 ꢁC, and the mix-
9
a) B. Kuhlmann, E. M. Arnett, and M. Siskin, J. Org.
Chem., 59, 5377 (1994). b) J. An, L. Bagnell, T. Cablewski,
C. R. Strauss, and R. W. Trainor, J. Org. Chem., 62, 2505
(1997). c) Y. Ikushima, K. Hatakeda, O. Sato, T. Yokoyama,
and M. Arai, J. Am. Chem. Soc., 122, 1908 (2000).
10 H. Oka, S. Yamago, J. Yoshida, and O. Kajimoto, Angew.
Chem., Int. Ed., 41, 623 (2002).
ꢁ
ture was stirred at 0 C for 5 h. To this mixture was added tetra-
ꢁ
chlorosilane (538 mg, 3.17 mmol) at 0 C. After stirring the mix-
ꢁ
ture at 0 C for 1 h and then at room temperature for 70 h, H2O
was added to the reaction mixture and the organic phase was sep-
arated. The aqueous phase was extracted with Et2O (three times)
and the combined organic phase was dried over MgSO4. Removal
of the solvents under reduced pressure, and subsequent gel perme-
ation chromatography afforded 16 (1.81 g, 81%) as colorless oil.
1H NMR (300 MHz) ꢀ 0.40–0.50 (m, 8H), 0.88 (t, J ¼ 7:2 Hz,
12H), 1.20–1.35 (br, 80H). 13C NMR (125 MHz) ꢀ 12.5, 14.1,
22.7, 23.9, 29.34, 29.40, 29.66, 29.70, 29.74, 29.76, 32.0, 33.9.
IR (neat) 2922, 2853, 1466, 766, 722 cmꢂ1. HRMS (EI) m=z calcd
for C36H75Si [M ꢂ C12H25]: 535.5638, found 535.5637.
11 a) P. Reardon, S. Metts, C. Crittendon, P. Daugherity, and
E. J. Parsons, Organometallics, 14, 3810 (1995). b) J. Diminnie,
S. Metts, and E. J. Parsons, Organometallics, 14, 4023 (1995).
12 M. A. Brook, ‘‘Silicon in Organic, Organometallic, and
Polymer Chemistry,’’ John Wiley & Sons, New York (2000).
13 a) K. Itami, K. Mitsudo, and J. Yoshida, J. Org. Chem., 64,
8709 (1999). b) K. Itami, T. Nokami, and J. Yoshida, Org. Lett., 2,
1299 (2000). c) K. Itami, K. Mitsudo, T. Kamei, T. Koike, T.
Nokami, and J. Yoshida, J. Am. Chem. Soc., 122, 12013 (2000).
d) K. Itami, T. Nokami, and J. Yoshida, J. Am. Chem. Soc.,
123, 5600 (2001). e) K. Itami, T. Koike, and J. Yoshida, J. Am.
Chem. Soc., 123, 6957 (2001). f) K. Itami, T. Kamei, and J.
Yoshida, J. Am. Chem. Soc., 123, 8773 (2001). g) K. Itami, K.
Mitsudo, and J. Yoshida, Angew. Chem., Int. Ed., 40, 2337
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Yoshida, J. Org. Chem., 66, 3970 (2001). i) K. Itami, T. Nokami,
Y. Ishimura, K. Mitsudo, T. Kamei, and J. Yoshida, J. Am. Chem.
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J. Yoshida, J. Org. Chem., 67, 2645 (2002). k) K. Itami, K.
Mitsudo, and J. Yoshida, Angew. Chem., Int. Ed., 41, 3481
(2002). l) K. Itami, K. Mitsudo, T. Nokami, T. Kamei, T. Koike,
and J. Yoshida, J. Organomet. Chem., 653, 105 (2002). m) K.
Itami, M. Mineno, T. Kamei, and J. Yoshida, Org. Lett., 4, 3635
(2002). n) K. Itami, T. Kamei, M. Mineno, and J. Yoshida, Chem.
Lett., 2002, 1084. o) K. Itami, T. Kamei, and J. Yoshida, J. Am.
Chem. Soc., 125, 14670 (2003).
This work was supported by CREST of Japan Science and
Technology Corporation. We thank Dr. Hiroyuki Oka for tech-
nical assistance and valuable suggestions.
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