Highly efficient and chemoselective conversion of aldehydes to acylals catalyzed with tungsten hexachloride (WCL6)

Article abstract of DOI:10.1081/SCC-120002503

Different types of aldehydes react chemoselectively with acetic anhydride in the presence of a catalytic amount of tungsten hexachloride (WCl₆) to produce the corresponding gem-diacetates in good to excellent yields.

Full text of DOI:10.1081/SCC-120002503

This article was downloaded by: [Stony Brook University]
On: 20 December 2014, At: 11:41
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
HIGHLY EFFICIENT AND CHEMOSELECTIVE
CONVERSION OF ALDEHYDES TO ACYLALS CATALYZED
WITH TUNGSTEN HEXACHLORIDE (WCl )
6
a
a
a
Babak Karimi , Gholam-Reza Ebrahimian & Hassan Seradj
a
Department of Chemistry , Institute for Advanced Studies in Basic Sciences (IASBS) ,
P.O. Box 45195-159, Gava Zang, Zanjan, Iran
Published online: 16 Aug 2006.
To cite this article: Babak Karimi , Gholam-Reza Ebrahimian & Hassan Seradj (2002) HIGHLY EFFICIENT AND
CHEMOSELECTIVE CONVERSION OF ALDEHYDES TO ACYLALS CATALYZED WITH TUNGSTEN HEXACHLORIDE (WCl ), Synthetic
6
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:5, 669-673, DOI:
10.1081/SCC-120002503
To link to this article: http://dx.doi.org/10.1081/SCC-120002503
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, 32(5), 669–673 (2002)
HIGHLY EFFICIENT AND
CHEMOSELECTIVE CONVERSION
OF ALDEHYDES TO ACYLALS
CATALYZED WITH TUNGSTEN
HEXACHLORIDE (WCl6)
Babak Karimi,* Gholam-Reza Ebrahimian,
and Hassan Seradj
Department of Chemistry, Institute for
Advanced Studies in Basic Sciences (IASBS),
P.O. Box 45195-159, Gava Zang, Zanjan, Iran
ABSTRACT
Different types of aldehydes react chemoselectively with acetic
anhydride in the presence of a catalytic amount of tungsten
hexachloride (WCl ) to produce the corresponding gem-
6
diacetates in good to excellent yields.
The reaction of aldehydes with organic acid anhydrides to give the
1
corresponding acylals has been known for a long time. 1,1-Diacetates are
2
useful protective group for aldehydes, and synthetically important precur-
3
sors for the preparation of 1-acetoxydienes for Diels-Alder reactions. On the
other hand, relative acid stability of 1,1-diacetates is compared with the
4
corresponding O,O-acetals, is an interesting feature of such gem-diacetates
*
Corresponding author. Fax: þ98 (241) 4249023; E-mail: karimi@iasbs.ac.ir
69
6
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
6
70
KARIMI, EBRAHIMIAN, AND SERADJ
as carbonyl protecting groups. The preparation of 1,1-diacetates, generally,
has been achieved by the reaction of aldehydes with acetic anhydride under
1
the catalysis of strong protic acids such as H SO , H PO and CH SO H,
,5
6
2
8
4
3
4
9
3
3
7
4
10
and Nafion-H. Lewis acids such as ZnCl , FeCl , PCl , I , Sc(OTf ) ,
11
2
3
3
2
3
1
and solid acidic catalysts like zeolites, expansive graphite, and clay have
2
13
14
1
5
also been shown as alternative catalysts for the formation of 1,1-diacetates.
Although, in a number of these methods some improvement has been
observed, in practice the yields of the desired acylals and the chemo-
selectivity and rate of the reactions were not always satisfactory. We have
developed new applications of tungsten hexachloride (WCl ) as either an
6
oxophilic metal chloride or a powerful Lewis acid in recent years. In this
regard, chemoselective dithioacetalization of carbonyl compounds and
1
transdithioacetalization of acetals, deoxygenation of sulfoxides and reduc-
6
1
7
tive dimerization of sulfonyl chlorides, chemoselective acetalization of
1
carbonyl compounds, deprotection of acetals, and one-pot ring expan-
8
19
2
0
sion-chlorination of 1,3-dithiolanes and 1,3-dithianes have been reported.
This communication wish to report that WCl in CH Cl or in the
6
2
2
absence of solvent can act as an efficient catalyst for the chemoselective con-
version of aldehydes to the corresponding 1,1-diacetates (table). As shown
in the table various types of aromatic aldehydes bearing either electron-
withdrawing or electron-releasing group including cinnamaldehyde were
converted to their acylals in the presence of Ac O (1 ml) and WCl
2
6
(
1
1–4mol%) under solvent-free conditions in excellent yields (table, Entries
2
0
–6). Aliphatic aldehydes as well as a,b-unsaturated aldehydes were also
furnished the corresponding acylals in good to excellent yields under
the same reaction conditions (table, Entries 7 and 8). When benzaldehyde
or 4-nitrobenzaldehyde (1 mmol) allowed to react with 1 ml acetic anhydride
at room temperature in CH Cl as solvent, TLC analysis of the reaction
2
2
mixture after 15 min indicate almost the complete disappearance of starting
aldehydes. After work up, the corresponding 1,1-diacetate were also isolated
in excellentyields(table, Entries9and10). As shown in the scheme, when a1 : 1
mixture of benzaldehyde and acetophenone allowed to react with acetic
anhydride (1 ml) in the presence of WCl (1 mol%), and the reaction mixture
6
Scheme.

ORDER
REPRINTS
CONVERSION OF ALDEHYDES TO ACYLALS
671
Table. Tungsten Hexachloride Catalyzed Formation of gem-Diacetates
worked up after 3 min, NMR analysis of the crude products consisted of a
1
: 1 mixture of benzaldehyde diacetyl acetal and acetophenone.
These experiments clearly indicated the ability of the method for
chemoselective protection of aldehydes as 1,1-diacetates in keto aldehydes.
In light of the simplicity of the procedure, excellent yields of the pro-
duct and high yields of the product, this procedure could be an alternative

ORDER
REPRINTS
6
72
KARIMI, EBRAHIMIAN, AND SERADJ
for the available methods of this transformation. Further investigation
on the new applications of WCl and its related reagents are ongoing in
our laboratories.
6
EXPERIMENTAL
General Procedure for the Preparation of 1,1-Diacetates
To a solution of aldehyde (2 mmol) and freshly distilled acetic anhy-
dride (2 ml) in anhydrous CH Cl (25 ml) or under solvent-free conditions,
2
2
tungsten hexachloride (0.02–0.08 mmol) was added at room temperature
and the mixture was stirred for the time indicated in the table. Progress
of the reaction was monitored by TLC or GC. After completion of the
reaction the reaction was quenched with water (25 ml), and the mixture
was extracted with CH Cl (2 Â 25 ml). The organic layer was separated,
2
2
and washed with saturated NaHCO (2 Â 25 ml) and water (15 ml) and
3
dried over anhydrous Na SO . Evaporation of the solvent under reduced
2
4
pressure gave the almost pure 1,1-diacetate.
ACKNOWLEDGMENTS
The author thanks the Institute for Advanced Studies in Basic
Sciences (IASBS) Research Council for partial support of this work. We
also appreciate Prof. Habib Firouzabadi for donation of WCl6.
REFERENCES
1. Goegory, M.J. J. Chem. Soc. B 1970, 1201.
2. Greene, T.W.; Wuts, P.G.M. Protective Groups in Organic Synthesis,
2nd Ed.; Wiley: New York, 1991; 184–185.
3
4
5
. Held, H.; Rengstle, A.; Mayer, D. In Ullman’s Encyclopedia of Industrial
Chemistry, 5th Ed.; Gerhartz, W., Ed.; VCH: New York, Vol. A1, p. 68.
. Kochhar, K.S.; Bal, B.S.; Deshpande, R.P.; Rajadhyaksha, S.N.;
Pinnick, H.W. J. Org. Chem. 1983, 48, 1765.
. Tomita, M.;Kikuchi, T.; Bessho, K.; Hori, T.;Inubushi, Y. Chem. Pharm.
Bull. 1963, 11, 1484.
. Freeman, I.; Karchefski, E.M. J. Chem. Eng. Data 1977, 22, 355.
6
7
8
. Olah, G.A.; Mehrotra, A.K. Synthesis 1982, 962.
. Scriabire, I. Bull. Chem. Soc. Fr. 1961, 1194.

ORDER
REPRINTS
CONVERSION OF ALDEHYDES TO ACYLALS
673
9
. Michie, J.K.; Miller, J.A. Synthesis 1981, 824.
0. Deka, N.; Kalita, D.J.; Borah, R.; Sarma, J.C. J. Org. Chem. 1997,
2, 1563.
1
6
1
1
1. Aggarwal, V.K.; Fonquerna, S.; Vennall, G.P. Synlett 1998, 849.
2. (a) Gigante, B.; Pereira, C.; Marcelo-Curto, M.J.; Carreyre, H.;
Perot, G.; Guisnet, M. Synthesis 1995, 1077; (b) Kumar, P.; Hegda, V.R.;
Kumar, T.P. Tetrahedron Lett. 1995, 36, 601.
1
1
1
3. Jin, T.S.; Du, G.Y.; Zhang, Z.H.; Li, T.S. Synth. Commun. 1997,
2
7, 2261.
4. (a) Zhang, Z.H.; Li, T.S.; Fu, C.G. J. Chem. Res., (Synop) 1997, 174;
b) Li, T.S.; Zhang, Z.H.; Gao, Y.J. Synth. Commun. 1998, 28, 4665.
(
5. For a review of different methods for preparation of 1,1-diacetates see:
Sydnes, L.K.; Sandberg, M. Tetrahedron 1997, 53, 12679.
16. Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synlett 1998, 739.
17. Firouzabadi, H.; Karimi, B. Synthesis 1999, 500.
18. Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synth. Commun. 1999,
2
9, 2255.
9. Firouzabadi, H.; Iranpoor, N.; Karimi, B. J. Chem. Res., (Synop)
998, 664.
0. Firouzabadi, H.; Iranpoor, N.; Karimi, B. Synlett 1999, 413.
1
2
1
Received in the UK June 12, 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/101081SCC120002503