Oxidation of 2-Pyridyldimethylsilyl Group to Hydroxyl Group by H2O2/KF. Implication of Fluoride Ion Accelerated 2-Pyridyl-Silyl Bond Cleavage

Full text of DOI:10.1021/jo990740u

J . Org. Chem. 1999, 64, 8709-8714
8709
Oxid a tion of 2-P yr id yld im eth ylsilyl Gr ou p
to Hyd r oxyl Gr ou p by H2O2/KF . Im p lica tion
of F lu or id e Ion Acceler a ted 2-P yr id yl-Silyl
Bon d Clea va ge
Kenichiro Itami, Koichi Mitsudo, and J un-ichi Yoshida*
Department of Synthetic Chemistry and Biological
Chemistry, Graduate School of Engineering,
Kyoto University, Yoshida, Kyoto 606-8501, J apan
Fleming and co-workers found that the PhMe2Si-C bond
can be cleaved oxidatively in two steps (eq 2).9 These two
Received May 3, 1999
In tr od u ction
Silicon-carbon bonds are generally quite stable to most
of the synthetic reagents and manipulations including
oxidants. Therefore, the oxidative cleavage of silicon-
carbon bond is one of the challenging topics in silicon
chemistry.1-7 In 1983, Tamao and co-workers have found
that the silicon-carbon bonds can be cleaved by hydrogen
peroxide to afford the corresponding alcohol (eq 1).8 This
was the first bona fide case of the practical oxidative
cleavage of silicon-carbon bonds. The only limitation
might be that it requires at least one electron-withdraw-
ing group such as an alkoxy group on silicon. In 1984,
landmark achievements have served to galvanize the
preexisting interest in the silicon-based reagents in the
synthetic community. To date, certain silyl groups have
been well recognized as important hydroxyl group sur-
rogates in modern organic synthesis. Listed in Chart 1
are the other representative silyl groups which can be
oxidatively converted to hydroxyl group.10-21
Recently, we have developed a 2-pyridyldimethylsilyl
(2-PyMe2Si) group as a multifunctional phase tag in
solution phase synthesis.22 The 2-PyMe2Si group makes
the phase switching feasible, thereby enabling easy
purification of 2-pyridylsilylated compounds by simple
acid-base extraction. Phase tagging (introduction of
2-PyMe2Si group to organic molecules) is easily ac-
complished by the rhodium(I)-catalyzed hydrosilylation
of alkenes. When confronted with the detagging of the
phase tag (removal of 2-PyMe2Si group), we searched for
a convenient method for the oxidative cleavage of the
2-PyMe2Si-C bond. We examined Tamao’s procedure for
the detagging protocol and found that the 2-PyMe2Si
* To whom correspondence should be addressed. Tel: (81)-75-753-
5651. Fax: (81)-75-753-5911. E-mail: yoshida@sbchem.kyoto-u.ac.jp.
(1) For excellent reviews on the oxidative cleavage of silicon-carbon
bond, see: (a) Tamao, K. Advances in Silicon Chemistry; J AI Press
Inc.: Greenwich, CT, 1996; Vol. 3, p 1. (b) J ones, G. R.; Landais, Y.
Tetrahedron 1996, 52, 7599.
(2) (a) Ager, D. J . Tetrahedron Lett. 1980, 21, 4759. (b) Miller, J .
A.; Zweifel, G. J . Am. Chem. Soc. 1981, 103, 6217.
(3) (a) Stork, G.; Colvin, E. J . Am. Chem. Soc. 1971, 93, 2080. (b)
Bu¨chi, G.; Wu¨est, H. J . Am. Chem. Soc. 1978, 100, 294. (c) Cunico, R.
F. J . Organomet. Chem. 1981, 212, C51. (d) Kuwajima, I.; Urabe, H.
Tetrahedron Lett. 1981, 22, 5191. (e) Fleming, I.; Newton, T. W. J .
Chem. Soc., Perkin Trans. 1 1984, 119. (f) Bulman Page, P. C.;
Rosenthal, S. Tetrahedron Lett. 1986, 27, 1947.
(4) (a) Ochiai, M.; Nagao, Y. J . Synth. Org. Chem., J pn. 1986, 44,
660. (b) Wilson, S. R., Augelli-Szafran, C. E. Tetrahedron 1988, 44,
3983. (c) Fujii, T.; Hirao, T.; Ohshiro, Y. Tetrahedron Lett. 1993, 34,
5601.
(5) (a) Yoshida, J .; Murata, T.; Isoe, S. Tetrahedron Lett. 1986, 27,
3373. (b) Koizumi, T.; Fuchigami, T.; Nonaka, T. Chem. Express 1986,
1, 355. (c) Yoshida, J .; Murata, T.; Isoe, S. Tetrahedron Lett. 1987, 28,
211. (d) Yoshida, J .; Murata, T.; Isoe, S. J . Organomet. Chem. 1988,
345, C23. (e) Koizumi, T.; Fuchigami, T.; Nonaka, T. Bull. Chem. Soc.
J pn. 1989, 62, 219. (f) Yoshida, J .; Maekawa, T.; Murata, T.; Matsu-
naga, S.; Isoe, S. J . Am. Chem. Soc. 1990, 112, 1962. (g) Yoshida, J .
Topics Curr. Chem. 1994, 170, 39. (h) Yoshida, J . J . Synth. Org. Chem.,
J pn. 1995, 53, 69.
(6) Mizuno, K.; Yasueda, M.; Otsuji, Y. Chem. Lett. 1988, 229.
(7) (a) Mu¨ller, R. Organometal. Chem. Rev. 1966, 1, 359. (b) Tamao,
K.; Kakui, T.; Kumada, M. J . Am. Chem. Soc. 1978, 100, 2268. (c)
Tamao, K.; Yoshida, J .; Kumada, M. J . Synth. Org. Chem., J pn. 1980,
38, 769. (d) Kumada, M.; Tamao, K.; Yoshida, J . J . Organomet. Chem.
1982, 239, 115. (e) Tamao, K.; Kakui, T.; Akita, M.; Iwahara, T.;
Kanatani, R.; Yoshida, J .; Kumada, M. Tetrahedron 1983, 39, 983.
(8) (a) Tamao, K.; Ishida, N.; Tanaka, T.; Kumada, M. Organome-
tallics 1983, 2, 1694. (b) Tamao, K.; Ishida, N. J . Organomet. Chem.
1984, 269, C37. (c) Tamao, K.; Kumada, M.; Maeda, K. Tetrahedron
Lett. 1984, 25, 321. (d) Tamao, K.; Maeda, K. Tetrahedron Lett. 1986,
27, 65. (e) Tamao, K.; Nakajima, T.; Sumiya, R.; Arai, H.; Higuchi, N.;
Ito, Y. J . Am. Chem. Soc. 1986, 108, 6090. (f) Tamao, K.; Nakajo, E.;
Ito, Y. J . Org. Chem. 1987, 52, 957. (g) Tamao, K.; Nakajo, E.; Ito, Y.
J . Org. Chem. 1987, 52, 4412. (h) Tamao, K.; Yamauchi, T.; Ito, Y.
Chem. Lett. 1987, 171. (i) Tamao, K.; Nakagawa, Y.; Arai, H.; Higuchi,
N.; Ito, Y. J . Am. Chem. Soc. 1988, 110, 3712. (j) Tamao, K. J . Synth.
Org. Chem., J pn. 1988, 46, 861. (k) Tamao, K.; Ishida, N.; Ito, Y.;
Kumada, M. Org. Synth. 1990, 69, 96.
(9) (a) Fleming, I.; Henning, R.; Plaut, H. Chem. Commun. 1984,
29. (b) Fleming, I.; Henning, R.; Parker, D. C.; Plaut, H. E.; Sanderson,
P. E. J . J . Chem. Soc., Perkin Trans. 1 1995, 317.
(10) (a) Fleming, I.; Ghosh, S. K. Chem. Commun. 1992, 1775. (b)
Fleming, I.; Ghosh, S. K. Chem. Commun. 1992, 1777.
(11) (a) Corey, E. J .; Chen, Z. Tetrahedron Lett. 1994, 35, 8731. (b)
Kno¨lker, H.; Wanzl, G. Synlett 1995, 378.
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Magar, S. S.; Desai, R. C.; Fuchs, P. L. J . Org. Chem. 1992, 57, 5360.
(13) (a) Fleming, I.; Winter, S. B. D. Tetrahedron Lett. 1993, 34,
7287. (b) Fleming, I.; Winter, S. B. D. Tetrahedron Lett. 1995, 36, 1733.
(14) Stork, G. Pure Appl. Chem. 1989, 61, 439.
(15) Hunt, J . A.; Roush, W. R. Tetrahedron Lett. 1995, 36, 501.
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(17) (a) Chan, T. H.; Pellon, P. J . Am. Chem. Soc. 1989, 111, 8737.
(b) Chan, T. H.; Nwe, K. T. J . Org. Chem. 1992, 57, 6107.
(18) van Delft, F. L.; van der Marel, G. A.; van Boom, J . H. Synlett
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(21) Kopping, B.; Chatgilialoglu, C.; Zehnder, M.; Giese, B. J . Org.
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10.1021/jo990740u CCC: $18.00 © 1999 American Chemical Society
Published on Web 10/21/1999

8710 J . Org. Chem., Vol. 64, No. 23, 1999
Ch a r t 1. Rep r esen ta tive Silyl Gr ou p s for Oxid a tion
Notes
Ta ble 1. H2O2 Oxid a tion of 1 u n d er Sever a l Con d ition s
Sch em e 1
entry H2O2 (equiv) KF (equiv) KHCO3 (equiv) yield (%)a
1
12
12
12
12
20
30
0
1.1
0
0
2.0
2.0
2.0
0
59
13
61
77
82
2
2.0
2.0
1.6
2.0
2.0
3b
4
5
6
a
b
Determined by GC analysis. Reaction without MeOH.
the amount of H2O2 resulted in higher yields (entries 5
and 6). Finally, the highest yield (82%) was observed
when 30 equiv of H2O2 was employed in the reaction
(entry 6). Interestingly, this H2O2 oxidation was found
to be characteristic to the 2-pyridyl group since neither
n-octyl(3-pyridyl)dimethylsilane (2) nor n-octylphenyldi-
methylsilane (3) gave 1-octanol under the best reaction
conditions for 1 (entry 6).
group can be easily converted to a hydroxyl group by
hydrogen peroxide in the presence of fluoride ion (eq 3).
Mech a n istic Hyp oth esis. We were delighted to find
that the 2-PyMe2Si-C bond can be oxidatively cleaved
to give the corresponding alcohol with the modified
Tamao procedure. However, there are several critical
questions to be addressed; why is this transformation
characteristic to the 2-PyMe2Si group and how the
2-PyMe2Si-C bond is cleaved. There might be two
possibilities for the mechanism of this oxidation. One
possibility is that 1 undergoes direct cleavage of the
2-PyMe2Si-C bond (Scheme 1, a). The second possibility
is a two-step mechanism involving the initial cleavage
of the 2-Py-Si bond (Scheme 1, b).
However, this observation was rather surprising since
the oxidation of related PhMe2Si group has been already
known to occur only in Fleming’s two-step procedure but
not with Tamao’s procedure. This prompts us to examine
the reaction conditions and mechanism of the cleavage
of the 2-PyMe2Si-C bond in detail. In this paper we
report the results of this study.
Resu lts a n d Discu ssion
Oxid a tive Clea va ge of th e 2-P yMe2Si-C Bon d
Usin g Ta m a o’s P r oced u r e. We first chose to follow the
lead of Tamao who has reported several reaction condi-
tions for the H2O2 oxidation of silicon-carbon bonds. The
oxidation of n-octyl(2-pyridyl)dimethylsilane (1) under
several conditions was examined, and the results are
depicted in Table 1. Reaction did not proceed at all in
the absence of KF (entry 1). When 2.0 equiv of KF was
employed, the oxidation proceeded smoothly to afford
1-octanol in 59% yield (entry 2). The absence of methanol
had a detrimental effect on yield (entry 3). Increase of
Qu en ch in g th e Rea ction a t th e Ha lfw a y. We
considered that the full analysis of the products at the
halfway of the reaction should be instrumental in ad-
dressing these issues. Therefore, the oxidation of n-octyl-
(2-pyridyl)dimethylsilane (1) was quenched by the addi-
tion of H2O and Et2O in 2 h (eq 4). The reaction gave
14% of n-octyl(hydroxy)dimethylsilane (4), 2% of n-octyl-
(methoxy)dimethylsilane (5), and 43% of pyridine to-
gether with 51% of 1-octanol and 19% of unchanged 1.
Identification of hydroxysilane 4 intimates its interme-
diacy in the oxidation of 1. Chan reported the Si-C bond

Notes
J . Org. Chem., Vol. 64, No. 23, 1999 8711
Ta ble 2. Exa m in a tion of th e Con ver sion of 1 to 5
entry KF (equiv) KHCO3 (equiv) conversion (%)a yield (%)a
1
2.0
2.0
2.0
1.0
0
2.0
2.0
0
2.0
2.0
100
100
100
100
4
72
60
74
81
4
2b
3
4c
5
a
b
Determined by GC analysis. Reaction for 20 h at 20 °C.
cleavage of the aminomethylsilanes under Tamao’s H2O2
oxidation conditions (eq 5).17 Although the mechanism
c Reaction for 20 h.
Ta ble 3. H2O2 Oxid a tion of 4 a n d 5a
entry
R
temperature (°C)
yield (%)
1
H
H
H
Me
Me
Me
20
50
50
20
50
50
53
76
11
58
68
31
2
3b
4
has not been clarified, hydroxysilane was detected at the
halfway of the reaction as well.17a
5
6b
Attem p t to Con ver t 2-P yr id ylsila n e to Hyd r oxy-
sila n e. Encouraged by the detection of 4 at the halfway
of the reaction, the feasibility of the direct conversion of
2-pyridylsilane 1 to hydroxysilane 4 has been examined.
The reactions were performed with or without KF and
KHCO3 in H2O/THF (1/20) at 50 °C for 2 h. H2O2 was
omitted from the reactions since hydroxysilanes are
already known to undergo H2O2 oxidation. However, the
reactions did not proceed at all to recover the starting
material 1 in quantitative yields.
a
All reactions were performed with 30% H2O2 (30 equiv), KF
(2.0 equiv), and KHCO3 (2.0 equiv) in MeOH/THF (1:1) under
argon for 8 h. Reaction without KF.
b
4 in 88% yield (91% conversion). The reaction without
KHCO3 gave almost identical yield of 4 (92% yield at 93%
conversion). On the other hand, the absence of KF
substantially slowed the reaction (50% yield at 50%
conversion).
Attem p t to Con ver t 2-P yr id ylsila n e to Meth oxy-
sila n e. Next, we turned our attention to the contamina-
tive production of methoxysilane 5 at the halfway of the
reaction (eq 4) and the feasibility of the initial conversion
of 1 to 5 has been examined. Again, the reactions were
performed in the absence of H2O2 since alkoxysilanes are
also known to undergo H2O2 oxidation. The results were
depicted in Table 2. When the reaction was performed
in the absence of H2O2 but otherwise identical to the
optimized conditions in eq 3, 5 was obtained in 72% yield
(entry 1). The reaction without KHCO3 also gave 5 in
nearly identical yield (74%, entry 3). Decreasing the
amount of KF to 1.0 equiv slowed the reaction rate but
gave 5 in 81% yield at 100% conversion (entry 4).
However, when the reaction was carried out in the
absence of KF, only a trace amount of 5 was formed
(entry 5). The role of KF has not yet been completely
elucidated; however, this addend clearly accelerated the
reaction. These observations shown in Table 2 and the
failure of the direct conversion of 1 to 4 strongly denote
that 5 is the initial intermediate in the oxidation of 1.
Attem p t to Con ver t Meth oxysila n e to Hyd r oxysi-
la n e. On the assumption that 4 might form by the
hydrolysis of 5 at the halfway of the reaction, we next
examined the hydrolysis of 5 in the absence of H2O2. The
reactions were performed with or without KF and KHCO3
in MeOH/THF/H2O (1/1/1) at 50 °C for 2 h. When the
reactions were carried out in the presence of KF (2.0
equiv) and KHCO3 (2.0 equiv), 5 was hydrolyzed to give
H2O2 Oxid a tion of Hyd r oxysila n e a n d Meth oxy-
sila n e. Hydroxysilanes11b and alkoxysilanes8 are already
known to undergo H2O2 oxidation. To firmly validate that
this was also true for our conditions, we next examined
the H2O2 oxidation of 4 and 5 (Table 3). As we expected,
both 4 and 5 underwent H2O2 oxidation to give 1-octanol
in 76 and 68% yields, respectively. Again, the absence of
KF had a detrimental effect in the oxidation (entries 3
and 6).
Mech a n ism of 2-P yMe2Si-C Bon d Clea va ge. Sup-
ported by the experimental results mentioned above, we
propose that the H2O2 oxidation of 1 proceeds by the
mechanism shown in Scheme 2.23 Initially, 2-pyridylsi-
lane (1) reacted with methanol in the presence of fluoride
ion to afford methoxysilane (5). Under the reaction
conditions, this methoxysilane may undergo either hy-
drolysis to afford hydroxysilane (4) or the H2O2 oxidation
to give 1-octanol as a final product. A mechanism
involving the initial formation of perhydroxysilane (6)
seems to be also possible. This may account for the fact
that the best yields through the stepwise reactions are
lower than the one-pot reaction yield. Preliminary result
on the m-CPBA oxidation of 1 in nonalcoholic solvent
(23) Alternatively, one could expect that the oxidation of the pyridyl
group first occurs to give the corresponding N-oxide, which can then
undergo â-elimination to give 4 and 2-hydroxypyridine or 2-methoxy-
pyridine. However, none of these products except 4 were detected in
the reaction mixture, which suggests that the mechanism involving
N-oxide â-elimination is not the case.

8712 J . Org. Chem., Vol. 64, No. 23, 1999
Notes
Sch em e 2
such as DMF also supports the possibility of this reaction
pathway, albeit with lower yield (eq 6).
The question which we must consider next is the
remarkable effect of 2-pyridyl group and the fluoride ion
acceleration on the cleavage of 2-Py-Si bond (1 to 5).
Webster had proposed in his pioneering work that the
solvolysis of 2-pyridyltrimethylsilane by alcohols and
water proceeds via cyclic transition state as shown in eq
7.24 In our case, methanolysis or hydrolysis in the absence
hexacoordinate transition state, the 2-pyridyl-silyl bond
should be weakened so that it is readily cleaved to result
in the formation of methoxysilane and pyridine even at
20 °C.
Con clu sion
We have observed the remarkable effect of the 2-pyr-
idyl group on the oxidative cleavage of carbon-silicon
bond under Tamao’s conditions. Mechanistic studies
revealed that the H2O2 oxidation of 1 proceeds by the
initial cleavage of the 2-Py-Si bond assisted by KF
followed by normal Tamao oxidation of the resulting
methoxysilane.
of fluoride ion was extremely slow presumably because
of the steric hindrance around the silicon atom.
A tentative rationalization of our results in the fluoride
ion accelerated cleavage of 2-Py-Si bond is given in eq
8. In this intermediate, the potassium ion is coordinated
with the nitrogen and the silicon is coordinated with
fluoride ion and methanol oxygen. Thus, the reaction
occurs only with 2-pyridylsilane but not with the corre-
sponding 3-pyridyl and phenylsilanes. The ab initio
molecular orbital calculations of the model compound
support the feasibility of the proposed intermediate (eq
9, Figure 1).25 According to the calculations, 2-PySiH3 and
KF form the stable complex (7) where the silicon atom
adopt pentacoordination (Figure 1). Complex 7 was found
to be -22.9 kcal/mol stable than 2-PySiH3 and KF at the
MP2/LANL2DZ level. Presumably, the resulting penta-
coordinated complex is further attacked by MeOH to
afford the proposed hexacoordinate complex (eq 8). In the
Exp er im en ta l Section
Gen er a l Meth od s. Unless otherwise noted, 1H, 13C, and 29Si
NMR spectra were measured at 300, 75, and 60 MHz, respec-
tively. Unless otherwise noted, all materials were obtained from
commercial suppliers and used without further purification.
Tetrahydrofuran (THF) and diethyl ether (Et2O) were freshly
distilled under argon from sodium benzophenone ketyl prior to
use. Methanol was distilled from Mg(OMe)2.
(25) The ab initio molecular orbital calculations were carried out
at the MP2/LANL2DZ level with geometry optimization using Gauss-
ian 98, Revision A.6.: Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.;
Scuseria, G. E.; Robb, M. A.; Cheeseman, J . R.; Zakrzewski, V. G.;
Montgomery J r., J . A.; Stratmann, R. E.; Burant, J . C.; Dapprich, S.;
Millam, J . M.; Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.;
Tomasi, J .; Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli,
C.; Adamo, C.; Clifford, S.; Ochterski, J .; Petersson, G. A.; Ayala, P.
Y.; Cui, Q.; Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari,
K.; Foresman, J . B.; Cioslowski, J .; Ortiz, J . V.; Stefanov, B. B.; Liu,
G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R.
L.; Fox, D. J .; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara,
A.; Gonzalez, C.; Challacombe, M.; Gill, P. M. W.; J ohnson, B.; Chen,
W.; Wong, M. W.; Andres, J . L.; Gonzalez, C.; Head-Gordon, M.;
Replogle, E. S.; Pople, J . A. Gaussian, Inc., Pittsburgh, PA, 1998.
(24) (a) Anderson, D. G.; Bradney, M. A. M.; Webster, D. E. J . Chem.
Soc. (B) 1968, 450. (b) Anderson, D. G.; Webster, D. E. J . Chem. Soc.
(B) 1968, 765. (c) Anderson, D. G.; Webster, D. E. J . Chem. Soc. (B)
1968, 1008.

Notes
J . Org. Chem., Vol. 64, No. 23, 1999 8713
saturated aq NaHCO3 (3 × 5 mL). The organic phase was dried
over K2CO3 and concentrated in vacuo. The residue was purified
by column chromatography (silica gel, hexane/EtOAc ) 5/1 as
eluents) to give 2 (351 mg, 43%) as a pale yellow oil: 1H NMR
(500 MHz): δ 0.27 (s, 6 H), 0.72-0.79 (m, 2 H), 0.86 (t, J ) 7.0
Hz, 3 H), 1.19-1.32 (m, 12 H), 7.23 (ddd, J ) 7.4, 4.9, 1.0 Hz, 1
H), 7.75 (dt, J ) 7.4, 1.9 Hz, 1 H), 8.55 (dd, J ) 4.9, 1.9 Hz, 1
H), 8.66 (dd, J ) 1.9, 1.0 Hz, 1 H); 13C NMR (125 MHz): δ -3.3,
14.1, 15.4, 22.6, 23.7, 29.17, 29.19, 31.8, 33.5, 123.1, 134.4, 141.2,
149.8, 154.0; 29Si NMR (60 MHz): δ -3.0; IR (neat) 1574, 1559,
1393, 1250 cm-1; HRMS m/e calcd for C15H27NSi: 249.1913,
found 249.1919. Anal. Calcd for C15H27NSi: C, 72.22; H, 10.91;
N, 5.61. Found: C, 72.12; H, 11.19; N, 5.57.
Typ ica l P r oced u r e for th e H2O2 Oxid a tion of 1 (Ta ble
1, en tr y 6). To a mixture of KF (116 mg, 2.0 mmol) and KHCO3
(200 mg, 2.0 mmol) in MeOH (2.5 mL) and THF (2.5 mL) were
added 1 (248 mg, 1.0 mmol) and then aq 30% H2O2 (3.42 g, 30
mmol) under argon. The mixture was stirred at 50 °C for 12 h.
After cooling to room temperature, the reaction mixture was
treated with water (20 mL). The mixture was extracted with
Et2O (5 × 20 mL), and the combined organic phase was washed
successively with 15% aq Na2S2O3 (20 mL). Drying over Na2-
SO4 and removal of the solvents under reduced pressure afforded
the crude 1-octanol. The yield of 1-octanol was 82% as judged
by capillary GC analysis using n-pentadecane as an internal
standard.
Qu en ch in g th e H2O2 Oxid a tion of 1 a t th e Ha lfw a y. To
a mixture of KF (116 mg, 2.0 mmol) and KHCO3 (200 mg, 2.0
mmol) in MeOH (2.5 mL) and THF (2.5 mL) were added 1 (248
mg, 1.0 mmol) and then aq 30% H2O2 (3.42 g, 30 mmol) under
argon. The mixture was stirred at 50 °C for 2 h. After cooling to
room temperature, the reaction mixture was treated with water
(5 mL) and was extracted with Et2O (3 × 10 mL). The aqueous
phase was basified to pH 14 by adding NaOH pellet and was
extracted with Et2O (3 × 10 mL). The combined organic phase
was washed successively with 15% aq Na2S2O3 (20 mL). Drying
over MgSO4 and careful removal of the solvents under reduced
pressure afforded the crude products. Yields of the detected
products were determined as follows either by capillary GC
analysis using n-pentadecane as an internal standard or by NMR
analysis using hexamethyldisilane as an internal standard: 1
(19%, NMR), 1-octanol (51%, GC), 4 (14%, NMR), 5 (2%, NMR),
and pyridine (43%, NMR).
m -CP BA Oxid a tion of 1. To a mixture of m-CPBA (175 mg,
1.02 mmol) and KF (31 mg, 0.53 mmol) in DMF (1.0 mL) was
added 1 (124 mg, 0.50 mmol) at room temperature under argon.
After stirring for 20 h at room temperature, the reaction mixture
was worked-up by the same procedure as that used for the H2O2
oxidation of 1. The yield of 1-octanol was 46% as judged by
capillary GC analysis using n-pentadecane as an internal
standard.
Attem p t to Con ver t 1 to 4. To a mixture of KF (116 mg,
2.0 mmol) and KHCO3 (200 mg, 2.0 mmol) in H2O (0.25 mL)
and THF (5.0 mL) was added 1 (249 mg, 1.0 mmol) under argon.
The mixture was stirred at 50 °C for 2 h. After cooling to room
temperature, the reaction mixture was treated with water (5
mL) and was extracted with Et2O (3 × 10 mL). Drying over
MgSO4 and removal of the solvents under reduced pressure
afforded 1 (98% by GC analysis).
F igu r e 1. Geometry of 7 (MP2/LANL2DZ).
Dim eth yl(2-p yr id yl)sila n e. To a solution of 2-bromopyridine
(40.4 g, 255.5 mmol) in Et2O (80 mL) was added dropwise a
n-hexane solution of n-butyllithium (255 mmol) at -72 °C under
argon. The mixture was stirred at -72 °C for an additional 2 h.
The resultant solution of 2-pyridyllithium was added to a
solution of chlorodimethylsilane (23.2 g, 245.6 mmol) in Et2O
(60 mL) at -72 °C. After stirring at room temperature for 1 h,
the mixture was washed with H2O (4 × 100 mL), and then the
organic phase was dried over Na2SO4. Removal of the solvent
under reduced pressure and subsequent distillation afforded the
title compound in 86% purity as judged by capillary GC. Second
distillation afforded the title compound (12.1 g, 36%) as a
colorless liquid in a pure form: bp 68-72 °C/20 mmHg. 1H NMR
(300 MHz): δ 0.40 (d, J ) 3.9 Hz, 6 H), 4.46 (septet, J ) 3.9 Hz,
1 H), 7.22 (ddd, J ) 7.5, 4.8, 1.2 Hz, 1 H), 7.54 (ddd, J ) 7.5,
1.8, 1.2 Hz, 1 H), 7.60 (td, J ) 7.5, 1.8 Hz, 1 H), 8.77 (ddd, J )
4.8, 1.8, 1.2 Hz, 1 H); 13C NMR (75 MHz): δ -4.8, 123.1, 129.8,
134.2, 150.4, 165.8; 29Si NMR (60 MHz): δ -19.3 (d, J ) 3.6
Hz); IR (neat) 2124, 1576, 1559, 1420, 1248 cm-1; HRMS m/e
calcd for C7H11NSi: 137.0661, found 137.0658.
Dim eth yl(3-p yr id yl)sila n e. By the similar procedure to that
used to prepare dimethyl(2-pyridyl)silane, the title compound
was obtained from 3-bromopyridine (78%) as a pale yellow
1
liquid: bp (bulb-to-bulb distillation) 120-150 °C/20 mmHg. H
NMR (300 MHz): δ 0.38 (d, J ) 3.9 Hz, 6 H), 4.46 (septet, J )
3.9 Hz, 1 H), 7.30 (dd, J ) 7.5, 4.8 Hz, 1 H), 7.85 (dt, J ) 7.5,
1.8 Hz, 1 H), 8.60 (dd, J ) 4.8, 1.8 Hz, 1 H), 8.71 (t, J ) 1.8 Hz,
1 H); 13C NMR (75 MHz): δ -4.3, 123.3, 132.4, 141.7, 150.3,
154.5; 29Si NMR (60 MHz): δ -18.0 (d, J ) 3.6 Hz); IR (neat)
2124, 1574, 1557, 1395, 1252 cm-1. Anal. Calcd for C7H11NSi:
C, 61.25; H, 8.08; N, 10.20. Found: C, 61.05; H, 8.18; N, 10.00.
Dim eth yl(1-octyl)(2-p yr id yl)sila n e (1). To a solution of
dimethyl(2-pyridyl)silane (1.10 g, 8.01 mmol) in Et2O (10 mL)
was added dropwise a solution n-octyllithium (6.57 mmol, 0.55
M in Et2O) under argon at -72 °C over 1 h. After stirring at
room temperature for 17 h, the mixture was washed with H2O
(3 × 30 mL). The organic phase was additionally extracted with
1 N aq HCl (5 × 30 mL). The aqueous phase was basified to pH
14 by adding NaOH pellet and was extracted with Et2O (3 × 50
mL). Drying over Na2SO4 and removal of the solvents under
reduced pressure afforded 1 (1.18 g, 72%) as a colorless oil: 1H
NMR (500 MHz): δ 0.30 (s, 6 H), 0.80-0.84 (m, 2 H), 0.86 (t,
J ) 7.1 Hz, 3 H), 1.20-1.37 (m, 12 H), 7.18 (ddd, J ) 7.7, 5.0,
1.5 Hz, 1 H), 7.48 (dt, J ) 7.7, 1.5 Hz, 1 H), 7.57 (td, J ) 7.7, 1.5
Hz, 1 H), 7.77 (dt, J ) 5.0, 1.5 Hz, 1 H); 13C NMR (125 MHz):
δ -3.6, 14.1, 14.8, 22.6, 23.7, 29.22, 29.23, 31.9, 33.5, 122.6,
129.0, 133.8, 150.1, 168.0; 29Si NMR (60 MHz): δ -4.4; IR (neat)
1576, 1559, 1417, 1246 cm-1; HRMS m/e calcd for C15H27NSi:
249.1913, found 249.1911. Anal. Calcd for C15H27NSi: C, 72.22;
H, 10.91; N, 5.61. Found: C, 72.31; H, 10.63; N, 5.63.
Attem p t to Con ver t 1 to 5 (Ta ble 2, en tr y 1). To a mixture
of KF (116 mg, 2.0 mmol) and KHCO3 (200 mg, 2.0 mmol) in
MeOH (2.0 mL) and THF (2.0 mL) was added 1 (249 mg, 1.0
mmol) under argon. The mixture was stirred at 50 °C for 2 h.
After cooling to room temperature, the reaction mixture was
treated with water (5 mL) and was extracted with Et2O (3 × 20
mL). Drying over MgSO4 and removal of the solvents under
reduced pressure afforded 5 (100% conversion, 72% yield by GC
analysis).
Attem p t to Con ver t 5 to 4. To a solution of KF (116 mg,
2.0 mmol) in MeOH (3.0 mL), THF (3.0 mL), and H2O (3.0 mL)
was added 5 (202 mg, 1.0 mmol) under argon. The mixture was
stirred at 50 °C for 2 h. After cooling to room temperature, the
reaction mixture was treated with water (5 mL) and was
extracted with Et2O (3 × 20 mL). Drying over MgSO4 and
removal of the solvents under reduced pressure afforded 4 (93%
conversion, 92% yield by NMR analysis).
Dim eth yl(1-octyl)(3-p yr id yl)sila n e (2). To a solution of
dimethyl(3-pyridyl)silane (403 mg, 2.94 mmol) in Et2O (10 mL)
was added dropwise a solution n-octyllithium (3.24 mmol, 0.55
M in Et2O) under argon at -72 °C over 1 h. After stirring at
room temperature for 17 h, the mixture was washed with

8714 J . Org. Chem., Vol. 64, No. 23, 1999
Notes
H2O2 Oxid a tion of 4 (Ta ble 3, en tr y 2). To a mixture of
KF (116 mg, 2.0 mmol) and KHCO3 (200 mg, 2.0 mmol) in MeOH
(3.0 mL) and THF (3.0 mL) were added 4 (188 mg, 1.0 mmol)
and then aq 30% H2O2 (3.42 g, 30 mmol) under argon. The
mixture was stirred at 50 °C for 5 h. After cooling to room
temperature, the reaction mixture was treated with water (20
mL) and was extracted with Et2O (5 × 20 mL). The combined
organic phase was washed successively with 15% aq Na2S2O3
(20 mL). Drying over MgSO4 and removal of the solvents under
reduced pressure afforded the crude 1-octanol. The yield of
1-octanol was 76% as judged by capillary GC analysis using
n-pentadecane as an internal standard.
(3.0 mL) and THF (3.0 mL) was added 5 (202 mg, 1.0 mmol)
and then aq 30% H2O2 (3.42 g, 30 mmol) under argon. The
mixture was stirred at 50 °C for 5 h. After cooling to room
temperature, the reaction mixture was treated with water (20
mL) and was extracted with Et2O (5 × 20 mL). The combined
organic phase was washed successively with 15% aq Na2S2O3
(20 mL). Drying over MgSO4 and removal of the solvents under
reduced pressure afforded the crude 1-octanol. The yield of
1-octanol was 68% as judged by capillary GC analysis using
n-pentadecane as an internal standard.
H2O2 Oxid a tion of 5 (Ta ble 3, en tr y 5). To a mixture of
KF (58 mg, 1.0 mmol) and KHCO3 (200 mg, 2.0 mmol) in MeOH
J O990740U