Cyclic tetrasiloxanetetraols: Formation, isolation, and characterization

Article abstract of DOI:10.1246/cl.2009.364

Hydrolysis of trialkoxysilanes having various substituents gave cyclic tetrasiloxanetetraols with all-cis isomer as the major fraction in the presence of equimolar amounts of water and sodium hydroxide. All stereoisomers of phenyl derivative were produced

Full text of DOI:10.1246/cl.2009.364

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Chemistry Letters Vol.38, No.4 (2009)
Cyclic Tetrasiloxanetetraols: Formation, Isolation, and Characterization
ꢀ
Ryuichi Ito, Yuriko Kakihana, and Yusuke Kawakami
School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi 923-1292
(Received January 21, 2009; CL-090074; E-mail: kawakami@jaist.ac.jp)
Hydrolysis of trialkoxysilanes having various substituents
As a typical example, phenyltrimethoxysilane (9.9 g,
50 mmol) was added to 2-propanol (50 mL), water (0.9 mL,
50 mmol), and sodium hydroxide (2.0 g, 50 mmol) at room tem-
perature, and stirred for a few hours. Formed crystalline material
was collected, dissolved in THF or ether and carefully neutral-
ized with acetic acid. Selected results on the formation of all-
cis cyclic tetrasiloxanetetraol are summarized in Table 1. Rea-
sonable yields were obtained for all the substituents examined.
Vinyl, vinylphenyl, and bromophenyl derivatives gave higher
yield, but the products could be isolated only as sodium or potas-
gave cyclic tetrasiloxanetetraols with all-cis isomer as the major
fraction in the presence of equimolar amounts of water and so-
dium hydroxide. All stereoisomers of phenyl derivative were
produced by isomerization of the all-cis isomer in the presence
of hydrochloric acid, and isolated and identified.
Brown originally reported the formation of all-cis cyclic
tetraphenyltetrasiloxanetetraol, all-cis-phenyl-T4 from phenyl-
trichlorosilane in the formation of octahedral octaphenyloctasil-
sesquioxane, phenyl-T8, and commented on the possibility of
sium salt, or trimethylsilyl derivatives.
Aromatic derivatives showed only one 29Si signal10 at
1
the compound as an intermediate. We reported formation and
isolation of all-cis-phenyl-T4 in 2-propanol from phenyltrimeth-
ꢁ
69:7, ꢁ67:2, ꢁ68:4, and ꢁ68:8 ppm, respectively. The iso-
butyl derivative gave only one peak at ꢁ57:9 ppm, which is
very close to the reported value (ꢁ59:7) for all-cis isopropyl
oxysilane in the presence of equimolar amounts of sodium hy-
2
3
droxide. Russian scientists, Shchegolikhina et al., Klement’ev
4
29
derivative. The Si signal at ꢁ69:7 ppm for phenyl-T4 was
5
3
et al., and Makarova et al. reported formation, characteriza-
3b,5,11
thought to be due to all-cis isomer.
Other aromatic deriva-
tion,3 isomerization, and derivatization of all-cis-phenyl-, or
vinyl-T4 derivatives. Meanwhile, Matsumoto et al. reported
the formation of an isomeric mixture of phenyl(isopropyl)tetra-
siloxane containing cis–cis–trans isomer as the major compo-
nent, and commented on the unlike isomerization of all-cis-
phenyl-T4.6b Formation of completely or imcompletely con-
densed polyhedral oligosilsesquioxane is not a simple reaction,
but includes many steps of equilibration depending on the reac-
,5
4
5
tives are also considered to be all-cis. Methoxyphenyl, naphthyl,
and methoxynaphthyl derivatives are good intermediates for
further functionalization via electrophilic substitution reactions.
By selecting suitable reaction conditions all-cis isomers could
be obtained for substituents examined.
When phenyl-T4 was obtained by the hydrolysis of phenyl-
trichlorosilane, stereoisomers other than all-cis seemed to be
29
present in the product, evidenced by Si NMR shown in
7
tion conditions. Nevertheless, the all-cis T4 might be a possible
8
Figure 1a. There are four stereoisomers in the tetramer, which
should give 6 signals. Overlapping of the signal may have occur-
red. Since only limited information was available on the iso-
merization, and separation of the stereoisomers depending on
the condition, isomerization of all-cis-phenyl-T4 (0.68 g, 1.25
mmol) was carried out in acetone (10 mL) with 1 M hydrochloric
acid (4 mL) at room temperature. After 10 min, the products re-
key intermediate for the formation of various T8 and detailed
study on the formation, isolation, and characterization of T4
having various substituents was carried out. Synthetic scheme
is shown in Scheme 1.
NaO
ONa
R
HO
OH
R
R
R
O
O
O
O
Si
O
Si
Si
O
Si
O
þ
H2O, NaOH
Solvent
CH3COOH
mained as one peak in SEC, and showed ½M þ Naꢂ ¼ 575:50 in
RSi(OR')3
O
1
0
THF or Ether
MALDI-TOF MS, consistent with the cyclic tetrasiloxanetet-
29
Si
Si
Si
Si
NaO
ONa
HO
OH
raol, but apparently four new peaks appeared in Si at ꢁ70:5
R' = Me, Et
R
R
R
R
(
weak), ꢁ70:4, ꢁ70:2, and ꢁ70:1 with the consumption of the
Scheme 1. Formation of all-cis cyclic tetrasiloxanetetraol.
peak of all-cis at ꢁ69:7 ppm. Configuration of one silicon atom
Table 1. All-cis cyclic tetrasiloxanetetraols
Trialkoxysilane
Solvent
Hexane
Product
Time/h
48
Yield/%
34
93
30–40
44
29Si NMR/ppm
i-BuSi(OMe)3
[i-Bu(OH)SiO]4
i-Pr(OH)SiO]4
ꢁ57:9
6b
6a
[
ꢁ59:7
PhSi(OMe)3
-MeOPhSi(OMe)3
-BrPhSi(OEt)3
2-Propanol
1-Butanol
EtOH
[Ph(OH)SiO]4
[4-MeOPh(OH)SiO]4
[4-BrPh(OH)SiO]4
20
48
48
ꢁ69:7
ꢁ67:2
—
4
4
trace
419
[
4-BrPh(ONa)SiO]4
—
—
—
—
ꢁ68:4
ꢁ68:8
VinylSi(OEt)3
Hexane–EtOH
[Vi(OK)SiO]4
15
34
7
71
30
6
3
c
4
9
4
-VinylPhSi(OEt)3
NpSi(OMe)3
-MeONpSi(OMe)3
EtOH
1-Butanol
1-Butanol
[4-ViPh(ONa)SiO]4
[Np(OH)SiO]4
69
19
4
[4-MeONp(OH)SiO]4
Copyright Ó 2009 The Chemical Society of Japan

Chemistry Letters Vol.38, No.4 (2009)
365
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also reported one Si at ꢁ58:97 for cis–trans–cis isomer and
three signals at ꢁ59:69, ꢁ59:12, and ꢁ59:00 for cis–cis–trans
6
b
isomer similar to our result.
In conclusion, all-cis cyclic tetrasiloxane tetraols with vari-
ous substituents were synthesized, and four stereo isomers of
cyclic phenyltetrasiloxanetetraol were identified with the aid
2
9
of Si NMR and XRD. By selecting suitable reaction condition
all-cis isomer could be obtained for substituents examined.
References and Notes
1
2
3
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2000, 19, 1077. b) O. I. Shchegolikhina, Y. A. Pozdnyakova, Y. A.
Molodtsova, S. D. Korkin, S. S. Bukalov, L. A. Leites, K. A.
Lyssenko, A. S. Peregudov, N. Auner, D. E. Katsoulis, Inorg. Chem.
2002, 41, 6892. c) O. I. Shchegolikhina, Y. A. Pozdnyakova, A. A.
Chetverikov, A. S. Peregudov, M. I. Buzin, E. V. Matukhina, Russ.
Chem. Bull. 2007, 56, 83.
4
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I. Y. Klement’ev, V. E. Shklover, M. A. Kulish, V. S. Tikhonov,
E. V. Volkova, Dokl. Akad. Nauk SSSR. 1981, 259, 1371.
N. N. Makarova, I. M. Petrova, P. V. Petrovskii, A. V. Kaznacheev,
L. M. Volkova, M. A. Shcherbina, N. P. Bessonova, S. N. Chvalun,
Y. K. Godovskii, Russ. Chem. Bull. 2004, 53, 1983.
6
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a) M. Unno, K. Takada, H. Matsumoto, Chem. Lett. 1998, 27, 489.
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Chem. Soc. 2005, 127, 2256.
29
Figure 1. Identification of phenyl-T4 by Si NMR.
a) R. H. Baney, M. Itoh, A. Sakakibara, T. Suzuki, Chem. Rev. 1995,
95, 1409. b) V. Chandrasekhar, R. Boomishankar, S. Nagendran,
Chem. Rev. 2004, 104, 5847. c) F. J. Feher, D. A. Newman, J. F.
Walzer, J. Am. Chem. Soc. 1989, 111, 1741. d) F. J. Feher, T. A.
Budzichowski, R. L. Blanski, K. J. Weller, J. W. Ziller, Organome-
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Sugahara, K. Kuroda, C. Kato, J. Chem. Soc., Chem. Commun.
Figure 2. Structure of isomer with Rf ¼ 0:64: a) ORTEP and b)
hydrogen bonding.
in the ring might have been inverted as can be understood by the
following assignment of the cis–cis–trans isomer.
A mixture of phenyl-T4 (1.0 g, 1.81 mmol) shown in
Figure 1a was used for separation. A major part of the all-cis
isomer was removed by precipitation after dissolving in ether
1
989, 208. k) Z. Li, Y. Kawakami, Chem. Lett. 2008, 37, 804.
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8
9
1
2
M. Ronchi, M. Pizzotti, A. O. Biroli, P. Macchi, E. Lucenti, C.
Zucchi, J. Organomet. Chem. 2007, 692, 1788.
0 NMR (1H at 500 MHz, 13C at 125 MHz, and 29Si at 99 MHz) spectra
(
5 mL) and pouring into hexane (20 mL) (ꢃ25%, Rf ¼ 0:05).
By two fold chromatography after removal of the all-cis
isomer, three isomers with Rf ¼ 0:29 (ꢃ40%), 0.53 (ꢃ15%),
in ppm were obtained on a Varian model Unity INOVA. MALDI-
TOF MS was performed with a Voyager DE RP. XRD was per-
formed on a Rigaku RAXIS RAPID imaging plate area detector with
graphite monochromated Cu Kꢀ radiation. Indexing was performed
from three oscillations exposed for 36 s. The crystal-to-detector dis-
tance was 127.4 mm. The exposure rate was 12.0 s/deg. Readout was
performed in the 0.100 mm pixel mode. The structure was solved by
direct methods and expanded using Fourier techniques. Some non-
hydrogen atoms were refined anisotropically, while the rest were
refined isotropically. Hydrogen atoms were refined using the riding
model. All calculations were performed using CrystalStructure crys-
tallographic software except for refinement performed using
SHELXL-97. Crystallographic data for all-trans isomer reported in
here have been deposited with the Cambridge Crystallographic Data
Center as supplementary publication No. CCDC 683440.
2
9
0
.64 (ꢃ1%) (toluene–ether = 1:1) were separated, whose Si
are also shown in Figures 1b–1d. It was clearly shown that pos-
sibly 6 signals appeared as five overlapped signals in Figure 1a.
To further confirm the structure, a single crystal of the isomer
2
9
with Rf ¼ 0:64; Si at ꢁ70:5 (Figure 1e) was analyzed by
XRD.10 The ORTEP structure is shown in Figure 2.
It was definitely confirmed that this isomer is all-trans con-
sistent with the NMR assignment. This compound actually forms
hydrogen-bonded dimer in the unit cell as shown in Figure 2b.
29
Other fractions with Rf ¼ 0:29; Si at ꢁ70:5, ꢁ70:2, ꢁ70:1,
2
9
and Rf ¼ 0:53; Si at ꢁ70:4 were reasonably concluded as
cis–cis–trans and cis–trans–cis isomer, respectively by consider-
ing symmetry of the molecule.
Matsumoto et al. reported the XRD of cis,cis,trans- and cis,
trans,cis-tetrasiloxanetetraol with isopropyl substituents. They
11 F. J. Feher, J. J. Schwab, D. Soulivong, J. W. Ziller, Main Group
Chem. 1997, 2, 123.
Published on the web (Advance View) March 21, 2009; doi:10.1246/cl.2009.364