JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
Preparation of Nano Silica Supported Sodium Hydrogen Sulfate: As an Efficient
Catalyst for the Trimethyl, Triethyl and t-Butyldimethyl Silylations of Aliphatic and
Aromatic Alcohols in Solution and under Solvent-free Conditions
Abdolreza Abri* and Somayeh Ranjdar
Chemistry Department, Faculty of Science, Azarbaijan Shahid Madani University, Tabriz, Iran
(Received: Nov. 7, 2013; Accepted: Feb. 15, 2014; Published Online: ??; DOI: 10.1002/jccs.201300586)
Nano silica supported sodium hydrogen sulfate has been prepared by mixing NaHSO4 with activated
Nano silicagel. We wish to report a new method for the synthesis of trimethyl (TMS), triethyl (TES) and
t-butyldimethyl silyl (TBS) ethers from benzylic, allylic, propargylic alcohols, phenols, naphtholes and
some of phenolic drugs in the solution and under solvent-free conditions.
Keywords: Silyl ethers; Phenolic drugs; TMSCl; TESCl; TBSCl; Nano silica; NaHSO4.
INTRODUCTION
Hexamethyldisilazane (HMDS) is considered as one
Preparation of silyl ethers with NaHSO4.
SiO2 (nano)/Et3N, in solution and under sol-
vent-free condition
Scheme 1
of the most useful reagents for this protection due to its
availability, cheapness and stability. Although HMDS has
easy handling and requires no special precautions, the low
silylating power is the main drawback to its application. A
variety of catalysts have been reported to improve the
silylating power of this reagent, such as zirconium sulpho-
phenyl phosphonate,1 K-10 montmorillonite,2 LiClO4,3
chlorotrimethylsilane,4 ZrCl4,5 silica chloride,6 trichloro-
isocyanuric acid,7 Al(HSO4)3,8 1,3-dibromo-5,5-diethyl-
barbituric acid,9 Fe(HSO4)3,10 and nitrogen ligand com-
plexes of metal chlorides.11 Although these procedures
have been improved, most of them suffer from disadvan-
tages such as long reaction times, forceful reaction condi-
tions, low selectivity, tedious work-up and use of toxic or
expensive reagents. Hence, introduction of new methods to
circumvent these problems is still in demand.
EXPERIMENTAL
Synthesis of silyl ethers were carried out under dry argon to
exclude oxygen and moisture from the reaction systems.
Materials: Chemicals were purchased from Fluka, Merk
and Aldrich chemical companies. Different methods are used dur-
ing multi-step synthesis to protect alcoholic hydroxyl groups
such as trimethylsilylation, which is one of the most widely used
methods for this purpose. All of trimethylsilyl ethers and some of
triethylsilyl ethers and tert-butyldimethyl silyl ethers are known
compounds, and were characterized by spectra analyses, compar-
isons with authentic samples (IR and NMR), and also by silica-gel
polygram SILG/UV 254 plates.
Measurements: 1H-NMR spectra were recorded on a
Brucker 400 AC spectrometer in CDCl3. The Infrared spectra
were recorded on a Shimadzu FT IR-408 spectrophotometer.
General procedure for the preparation of silyl ethers in
CH3CN: To a mixture of the substrate (1 mmol), triethylamine (1
mmol) and NaHSO4.SiO2 (nano) (0.03 mmol) in CH3CN (5 mL),
chlorosilane (1 mmol) was added dropwise within 10 min with
stirring at room temperature. After completion of the reaction,
(TLC or GC), water was added (10 mL) and the organic layer was
separated, dried (MgSO4) and filtered. Evaporation of the solvent
Recently, the use of metal hydrogen sulfates in or-
ganic reactions has become the focus of research area.12-16
In this paper, we investigated the applicability of nano sil-
ica instead of silica with Sodium hydrogen sulfate and use
chlorosilane instead of HMDS in these reactions. We report
an efficient method for the synthesis of silyl ethers of alco-
hols, phenols, naphtols and some of phenolic drugs with
chlorosilanes in the presence of NaHSO4.SiO2 (nano)/
Et3N, both in solution and under solvent-free conditions
(Scheme 1). Different types of alcohols and phenols were
subjected to trimethyl, triethyl and t-butyldimethyl silyl-
ations using this method at room temperature and under
completely heterogeneous reaction conditions (Tables
1-3).
* Corresponding author. Tel.: +98-412-432-7541; Fax: +98-412-432-7541; E-mail: ar.abri@azaruniv.edu
J. Chin. Chem. Soc. 2014, 61, 000-000
© 2014 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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