Silylation of Hydroxyl Groups
J. Chin. Chem. Soc., Vol. 56, No. 6, 2009 1263
CONCLUSION
X-ray diffraction (XRD) of silica-supported tin chlo-
ride
In conclusion, a practical, efficient and convenient
method for the silylation of hydroxyl compounds was de-
scribed. Also, we prepared and introduced SnCl4 supported
on silica gel as an efficient and reusable catalyst. There-
fore, we think that this method can be a useful addition to
the present methodologies for the silylation of hydroxyl
groups.
Powder X-ray diffraction measurement was performed
using a D8 Advance Diffractometer made by Bruker AXS
Company in Germany. The strongest peaks of the XRD pat-
tern correspond to the SiO2 plane with the other peaks in-
dexed as the (35), (53), and (67) planes of supported tin
chloride.
General procedure
EXPERIMENTAL SECTION
To a stirred solution containing the hydroxyl com-
pound (1 mmol) and HMDS (0.8 mmol) in CH3CN (2 mL)
was added silica supported Sn(Cl)4-n (0.015 g) and stirred
at room temperature. When the reaction was complete GC
(or TLC, n-hexane-EtOAc, 9:1) analysis, CH2Cl2 was added
(10 mL), and silica supported Sn(Cl)4-n was removed by fil-
tration. The solvent was evaporated and the trimethylsilyl
ether was isolated almost as a pure product. Further purifi-
cation was carried out by short column chromatography on
silica gel eluting with ethyl acetate/petroleum ether, if nec-
essary.
General
Chemicals were purchased from Merck, Fluka and
Aldrich Chemical Companies. IR spectra were run on a
1
Shimadzu Infra Red Spectroscopy FT-IR-8000. The H
NMR were run on a JEOL NMR-Spectrometer FX 90Q and
a Bruker Avance (DRX 500 MHz). Melting points were re-
corded on a Melting Point SMP1 apparatus in open capil-
lary tubes and are uncorrected. With TLC using silica gel
SILG/UV 254 plates the progress of reaction was followed.
All of the products are known and characterized by com-
parison of their spectral (IR, 1H-NMR), TLC and physical
data with those reported in the literature.14-22
ACKNOWLEDGEMENT
Catalyst preparation
We are thankful to the Persian Gulf University Re-
search Council for partial support of this work.
Silica gel 60 (0.063-0.200 mesh) was washed with 1
M HCl, followed by deionized water, 30% H2O2, and de-
ionized water again. After being washed, the silica was
dried overnight at 373 K in vacuum to give preconditioned
silica gel.2
Received March 6, 2009.
REFERENCES
1. Choudhary, D.; Paul, S.; Gupta, R.; Clark, J. H. Green
Chem. 2006, 8, 479-482.
Preparation of silica-supported tin chloride
4.0 g of preconditioned silica was first refluxed in to-
luene for 2 h. Then tin chloride (5.5 mL) was added to this
mixture and allowed to react for 1 day under refluxing con-
dition. Then, the mixture was filtered and washed three
times with absolute ethanol and dried at 373 K to give
5.137 g of product (0.2 g equal to 0.6 mmol H+).
2. Li, Z.; Ma, X.; Liu, J.; Feng, X.; Tian, G.; Zhu, A. J. Mol.
Catal. A Chem. 2007, 272, 132.
3. Jyothi, T. M.; Kaliya, M. L.; Herskowitz, M.; Landau, M. V.
Chem. Commun. 2001, 992.
4. Greene, T. W.; Wutes, P. G. M. Greene’s Protective Groups
in Organic Synthesis, 4th ed.; Wiley: New York, 2007.
5. Van Look, G.; Simchen, G.; Heberle, J. Silylating Agents, 2nd
ed.; Fluka, Buches: Switzerland, 1995.
FT-IR spectrum of silica-supported tin chloride
The FT-IR spectrum of the catalyst is shown in Fig. 2.
The catalyst is solid, and its solid state IR spectrum was re-
corded using the KBr disk technique. For silica (SiO2), the
major peaks are broad antisymmetric Si-O-Si stretching
from 1200 to 1000 cm-1 and symmetric Si-O-Si stretching
near 802 cm-1, and bending modes of Si-O-Si lie around
470 cm-1. For the O-Sn-Cl group, the FT-IR absorption
range of the O-Sn asymmetric stretching modes lies around
500-550 cm-1.29 The spectrum also shows a broad Si-OH
stretching absorption from 3600-3000 cm-1.
6. Zolfigol, M.-A.; Mohammadpoor-Baltork, I.; Habibi, D.;
Mirjalili, B.-F.; Bamoniri, A. Tetrahedron Lett. 2003, 44,
8165.
7. Corey, E. J.; Sinder, B. B. J. Am. Chem. Soc. 1972, 94, 2549.
8. Olah, G. A.; Gupta, B. G. B.; Narang, S. C.; Malhotra, R. J.
Org. Chem. 1979, 44, 4272.
9. Sa, B. A. D.; McLeod, D.; Verkade, J. G. J. Org. Chem. 1997,
62, 5057.
10. Lalonde, M.; Chan, T. H. Synthesis 1985, 817.
11. Gauttret, P.; El-Ghamarti, S.; Legrand, A.; Coutrier, D.;
Rigo, B. Synth. Commun. 1996, 26, 707.