"Zeofen," an efficient reagent for oxidative deprotection of trimethylsilyl ethers under microwave irradiation in solventless system

Article abstract of DOI:10.1081/SCC-100104458

The efficient and environmentally friendly oxidative deprotection of trimethylsilyl ethers using zeofen under microwave irradiation in solvent free condition is described.

Full text of DOI:10.1081/SCC-100104458

This article was downloaded by: [University of North Carolina]
On: 11 November 2014, At: 04:08
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer
House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic
Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
“ZEOFEN,” AN EFFICIENT REAGENT FOR OXIDATIVE
DEPROTECTION OF TRIMETHYLSILYL ETHERS UNDER
MICROWAVE IRRADIATION IN SOLVENTLESS SYSTEM
a
a
a
a
Majid M. Heravi , Dariush Ajami , Mitra Ghassemzadeh & Kourosh Tabar-Hydar
a
Chemistry & Chemical Engineering Research Center of Iran , P.O. Box 14335-186,
Tehran, Iran
Published online: 09 Nov 2006.
To cite this article: Majid M. Heravi , Dariush Ajami , Mitra Ghassemzadeh & Kourosh Tabar-Hydar (2001) “ZEOFEN,”
AN EFFICIENT REAGENT FOR OXIDATIVE DEPROTECTION OF TRIMETHYLSILYL ETHERS UNDER MICROWAVE IRRADIATION IN
SOLVENTLESS SYSTEM, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 31:14, 2097-2100, DOI: 10.1081/SCC-100104458
To link to this article: http://dx.doi.org/10.1081/SCC-100104458
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of
the Content. Any opinions and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied
upon and should be independently verified with primary sources of information. Taylor and Francis shall
not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other
liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

SYNTHETIC COMMUNICATIONS, 31(14), 2097–2100 (2001)
‘
‘ZEOFEN,’’ AN EFFICIENT REAGENT FOR
OXIDATIVE DEPROTECTION OF
TRIMETHYLSILYL ETHERS UNDER
MICROWAVE IRRADIATION IN
SOLVENTLESS SYSTEM
Majid M. Heravi,* Dariush Ajami, Mitra Ghassemzadeh,
and Kourosh Tabar-Hydar
Chemistry & Chemical Engineering Research Center of Iran,
P.O. Box 14335-186, Tehran, Iran
ABSTRACT
The efficient and environmentally friendly oxidative deprotec-
tion of trimethylsilyl ethers using zeofen under microwave
irradiation in solvent free condition is described.
The protection of certain functional groups and the deprotection of
the protected derivatives constitute important process in the synthetic chem-
istry of polyfunctional molecules including the total synthesis of natural
1
products.
The trimethylsilyl group is one of the most useful protecting groups
2
for alcohols and phenols in multistage organic synthesis. In recent years
direct oxidation of trimethylsilyl ethers to the corresponding carbonyl
compounds has been research interest of many laboratories including our
3
own. Most of these reagents dealing with direct oxidative deprotection of
*
Corresponding author.
2
097
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
2
098
HERAVI ET AL.
trimethylsilyl ethers are based on chromium. However there is a serious
4
drawback against oxidants base on chromium. They are corrosive and
irritants for the skin and sensitive parts of body such as eyes. They are
also toxic to human and to the environment. Derivatives of Cr(VI) in par-
5
ticular are well known carcinogens.
In recent years the acceleration of a wide range of chemical reactions
6
using microwave dielectric heating has been reported. The great majority of
these reactions have been performed in the solution phase but now a days
7
solid state reactions have attracted much attention.
Recently, we have introduced zeofen (zeolite HZSM-5 supported
8
iron(III) nitrate) as a user friendly and long lasting oxidizing agent.
Extending our work on the oxidative capability in this communication we
wish to report the ability of this efficient, non-toxic and non-polluting
reagent for oxidative deprotection of trimethylsilyl ethers under microwave
irradiation in very short time.
The oxidative deprotection reactions were carried out simply by
mixing 1–1.2 equiv. of zeofen with 1 equiv. of trimethylsilyl ethers in a beaker
under microwave irradiation (900 W) for 2 min. For example benzylsilyl
ether was oxidatively deprotected to benzaldehyde in almost quantitative
yield after 20 sec. It is worth mentioning that in the absence of zeolite the
reaction is very slow and more seriously, molten ferric nitrate and/or its
degradation product(s) adhered to the walls of the reaction vessel, forming
an intractable solid mass which made the isolation of carbonyl compounds
difficult and led to erratic results. Several examples illustrating this method
are summarized in Table 1. It is noteworthy that unlike other oxidative
deprotection methods, the major drawback of over oxidation of the ensuing
aldehydes, has not been observed under the reaction conditions.
EXPERIMENTAL
All compounds employed and obtained are known and were identified
by comparison of their physical data with those of authentic samples. Yields
refer to isolated products. Zeofen was prepared according to reported pro-
8
cedure. A national microwave (MW) oven operating at 2450 MHz were
used.
Oxidative Deprotection of Benzyl Trimethylsilyl Ether.
A Typical Procedure
Zeofen (equivalent to 1.2 mmol of ferric nitrate) was gradually added
to benzyl trimethylsilyl ether (0.18 g, 1 mmol) in a beaker and mixed with

ORDER
REPRINTS
ZEOFEN
2099
Table 1. Oxidative Deprotection of Trimethylsilyl Ethers with Zeofen Under
Microwave Irradiation in Solvent Free Condition
a
Time
(sec.)
Yield
(%)
Entry
Substrate
OSiMe
2-MeOC H CH OSiMe
Product
PhCHO
2-MeOC H CHO
1
2
3
4
5
6
7
8
9
PhCH
2
3
20
20
20
60
120
120
120
120
120
98
90
90
88
82
89
80
82
78
6
4
2
3
3
6
4
4-MeOC
4-MeC
2-NO -5-Me-C H CH OSiMe
H
6 4
CH
2
OSiMe
4-MeOC
4-MeC
2-NO -5-Me-C H CHO
6
4
H CHO
H
6 4
CH
2
OSiMe
3
6 4
H CHO
2
6
3
2
3
2
6
3
c-
6
H
11O CS iMe
3
Cyclohexanone
6 2
C H13CH CHO
C
6
H13CH
2
OSiMe
3
(E) PhCH ¼ CHCH
2
OSiMe
(–) Mentholtrimethylsilyl ether
3
(E)-PhCH ¼ CHCHO
Menthone
a
Yields based on the isolation of 2,4-dinitrophenylhydrazine derivatives.
spatula. The beaker was placed under microwave irradiation for 20 sec. The
product was extracted with methylene chloride and was passed through a
small bed of silica gel to afford pure benzaldehyde (Table 1).
REFERENCES
1
2
3
. Green, T.W. and Wuts, P.G.M. ‘‘Protective Groups in Organic
Synthesis’’, 2nd ed., John Wiley & Sons: New York, 1991.
. Olah, G.A. and Klumpp, D.A. Synthesis 1997, 744 and references cited
therein.
. a) Heravi, M.M.; Ajami, D.; Mojtahedi, M.M. and Tabar-Hydar, K. J.
Chem. Res. 1998, 620; b) Heravi, M.M.; Ajami, D. and Tabar-Hydar,
K. Monatsh. Chem. 1999, 130, 337; c) Heravi, M.M.; Ajami, D. and
Ghassemzadeh, M. Synthesis 1999, 393 and references cited therein; d)
Heravi, M.M.; Tajbakhsh, M. and Ghassemzadeh, M. Z. Naturforsch.
1999, 54b, 394.
4. Page, G. and Loar, G.W. In Kirk-Ottmer ‘‘Encyclopedia of Chemical
Technology’’, 4th ed., Wiley: New York, 1998.

ORDER
REPRINTS
2
5
6
7
8
100
HERAVI ET AL.
. Nriagu, J.O. and Nieboer, E. ‘‘Chromium in the Natural and Human
Environments’’, Eds., Wiley: New York, 1998.
. a) Mingas, D.P. and Baghurst, D.R. Chem. Soc. Rev. 1991, 20 1; b)
Abramvoich, R.A. Org. Prep. Proced. Int. 1991, 23, 685.
. Heravi, M.M.; Ajami, D.; Mojtahedi, M.M. and Ghassemzadeh, M.
Tetrahedron Lett. 1999, 40, 56 and references cited therein.
. Heravi, M.M.; Ajami, D.; Aghapour, K. and Ghassemzadeh, M. Chem.
Commun. 1999, 833.
Received in Japan June 20, 2000

Request Permission or Order Reprints Instantly!
Interested in copying and sharing this article? In most cases, U.S. Copyright
Law requires that you get permission from the article’s rightsholder before
using copyrighted content.
All information and materials found in this article, including but not limited
to text, trademarks, patents, logos, graphics and images (the "Materials"), are
the copyrighted works and other forms of intellectual property of Marcel
Dekker, Inc., or its licensors. All rights not expressly granted are reserved.
Get permission to lawfully reproduce and distribute the Materials or order
reprints quickly and painlessly. Simply click on the "Request
Permission/Reprints Here" link below and follow the instructions. Visit the
U.S. Copyright Office for information on Fair Use limitations of U.S.
copyright law. Please refer to The Association of American Publishers’
(AAP) website for guidelines on Fair Use in the Classroom.
The Materials are for your personal use only and cannot be reformatted,
reposted, resold or distributed by electronic means or otherwise without
permission from Marcel Dekker, Inc. Marcel Dekker, Inc. grants you the
limited right to display the Materials only on your personal computer or
personal wireless device, and to copy and download single copies of such
Materials provided that any copyright, trademark or other notice appearing
on such Materials is also retained by, displayed, copied or downloaded as
part of the Materials and is not removed or obscured, and provided you do
not edit, modify, alter or enhance the Materials. Please refer to our Website
User Agreement for more details.
Order now!
Reprints of this article can also be ordered at
http://www.dekker.com/servlet/product/DOI/101081SCC100104458