Eco-friendly Pt-Mo/ZrO2 solid acid catalyst for selective protection of carbonyl compounds

Article abstract of DOI:10.1081/SCC-100104330

An easy method for protection of carbonyl compounds has been carried out in excellent yields under catalysis of Pt-Mo/ZrO₂ in toluene at 383 K.

Full text of DOI:10.1081/SCC-100104330

This article was downloaded by: [Umeå University Library]
On: 22 April 2014, At: 09:57
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
ECO-FRIENDLY Pt–Mo/ZrO2 SOLID ACID CATALYST FOR
SELECTIVE PROTECTION OF CARBONYL COMPOUNDS
Benjaram M. Reddy a , Vangala R. Reddy a & D. Giridhar a
a Inorganic and Physical Chemistry Division , Indian Institute of Chemical Technology ,
Hyderabad, 500 007, India
Published online: 16 Aug 2006.
To cite this article: Benjaram M. Reddy , Vangala R. Reddy & D. Giridhar (2001) ECO-FRIENDLY Pt–Mo/ZrO2 SOLID ACID
CATALYST FOR SELECTIVE PROTECTION OF CARBONYL COMPOUNDS, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 31:12, 1819-1823, DOI: 10.1081/SCC-100104330
To link to this article: http://dx.doi.org/10.1081/SCC-100104330
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(12), 1819–1823 (2001)
ECO-FRIENDLY Pt–Mo/ZrO2 SOLID ACID
CATALYST FOR SELECTIVE PROTECTION
OF CARBONYL COMPOUNDS
Benjaram M.Reddy, * Vangala R.Reddy, and D.Giridhar
Inorganic and Physical Chemistry Division, Indian Institute of
Chemical Technology, Hyderabad – 500 007, India
ABSTRACT
An easy method for protection of carbonyl compounds has
been carried out in excellent yields under catalysis of Pt–Mo/
ZrO2 in toluene at 383 K.
The carbonyl function, as present in aldehydes and ketones, is the most
versatile functional group in organic synthesis. During a synthetic sequence a
carbonyl group may have to be protected against encounter by various
reagents such as acidic, basic, oxidizing and reducing agents. One of the
most useful protecting methods of carbonyl compounds is acetalization
or thioacetalization1 and the protective groups are acyclic or cyclic acetals
and ketals. Recently, different catalytic systems such as SOCl2–SiO2,2
HY Zeolite,3 Mg–ZnTf,4 natural clay,5 and modified days such as
Montmorlonite-KSH6 and Ce-Montmorlonite7 have been attempted for
effecting the acetalization or thioacetalization reactions. However, most of
these reported catalysts show many disadvantages such as a rapid catalyst
deactivation, production of wasteful products, low product yields, and severe
reaction conditions. In view of the environmental concern, there is a global
* Corresponding author.
1819
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
1820
REDDY, REDDY, AND GIRIDHAR
effort to replace the conventional catalysts by new solid acids, which can be
easily separable from the products, less toxic, and reusable. In this commu-
nication we report an efficient eco-friendly Pt–Mo/ZrO2 solid acid catalyst for
selective protection of various aldehydes and ketones including a, b unsatu-
rated carbonyl compounds with ethane-1,2-diol as protecting group.
The importance of sulfated ZrO2 as a solid super-acid for various
catalytic applications has been identified recently.8 However, the
sulfated zirconia undergoes rapid deactivation due to loss of sulfate ions
during activation and catalytic run. Very recent investigations reveal that
WOx-ZrO2 and MoOx- ZrO2 are another set of alternative catalysts in reac-
tions requiring stronger acid sites.9–11 The major advantage of tungsten or
molybdenum modified zirconia over sulfated ZrO2 is that there is no loss of
SO24À ion during thermal activation and catalytic run, hence, less deactiva-
tion. The present study discloses that Pt-MoO3/ZrO2 is an interesting and
multifunctional catalyst, much superior to the earlier reported catalysts. The
use of a reusable heterogeneous catalyst in achieving selective protection of
carbonyl compounds is very significant from the point of view of its com-
mercial implications.
Preparation of Catalyst: Zirconium hydroxide was prepared from an
aqueous solution of ZrOCl2 (Loba Chemie, GR grade) by adding NH4OH
solution (Ranbaxy, LR grade) drop-wise from a burette upto pH 8. The
obtained precipitate was washed several times until free from chloride ions
and dried at 393 K for 48 h. Ammonium heptamolybdate (J T Baker,
England, GR grade) aqueous solution of adequate concentration (9 wt.%)
was added to the oven dried hydroxide and the excess water was evaporated
on a water bath. The resulting sample was oven dried again at 393 K for 48 h
and calcined at 873 K for 6 h in a flow of oxygen. The calcined sample was
impregnated with hexachloroplatinic acid (Loba Chemie, GR grade) sol-
ution to obtain 0.5 wt.% of platinum containing catalyst by an incipient
wetness technique. The resulting sample was oven dried at 393 K for 48 h
and calcined at 873 K for 6 h in a flow of oxygen. The X-ray powder diffrac-
tion analysis of Pt-Mo/ZrO2 and Mo/ZrO2 samples show that the former
contains more tetragonal zirconia which is known to be responsible for
strong acidity of these catalysts.12,13
General Procedure for Protecting of Carbonyl Group: Equimolar
ratio of carbonyl compound and ethylene glycol with the Pt-Mo/ZrO2
catalyst (0.3 g) along with the solvent toluene was heated at 383 K in a
round bottom flask provided with a Dean-Stark apparatus having conden-
ser to remove the water from the reaction mixture. After completion of the
reaction (ca. 6 h), the catalyst was filtered off and the filtrate was concen-
trated and chromatographed on SiO2 to obtain the cyclic acetal in good
yields. The results are summarized in Table 1. The results thus show that the

ORDER
REPRINTS
Pt–Mo/ZrO2 SOLID ACID CATALYST
1821
Table 1. Protection of Carbonyl Functions with Ethane-1,2-diol in the Presence of
Eco-friendly Pt-Mo/ZrO2 Solid Acid Catalyst
aBased on NMR.

ORDER
REPRINTS
1822
REDDY, REDDY, AND GIRIDHAR
Pt-Mo/ZrO2 will be ideally suited for the selective protection of carbonyl
compounds. The main advantage of this catalyst is easy operation and
simplicity in the workup, which involves mere filtration of the catalyst
and its reusability.
The CH analysis data for various product molecules is as follows:
C7H12O2 (Entry 1): C, 65.62; H, 9.37. Found: C, 65.5; H, 9.43. C8H14O2
(Entry 2): C, 67.60; H, 9.85. Found: C, 66.5; H, 9.53. C9H16O2 (Entry 3): C,
69.23; H, 10.25. Found: C, 68.7; H, 9.89. C10H12O2 (Entry 4): C, 73.17; H,
7.31. Found: C, 73.2; H, 7.20. C11H12O2 (Entry 5): C, 75.00; H, 6.81. Found:
C, 73.4; H, 7.1. C10H12O3 (Entry 6): C, 63.82; H, 6.38. Found: C, 62.85; H,
6.21. C9H9NO4 (Entry 7): C, 65.06; H, 6.02. Found: C, 65.5; H, 5.85.
C9H9ClO2 (Entry 8): C, 67.60; H, 9.85. Found: C, 65.7; H, 9.61.
C9H9NO4 (Entry 9): C, 65.06; H, 6.02. Found: C, 64.5; H, 5.95.
ACKNOWLEDGMENT
Thanks are due to CSIR, New Delhi for the award of senior research
fellowship to VRR.
REFERENCES
1. Kocienski, P.J. Protecting Groups, Eds., D. Enders, R. Noyori and
B.M. Trost, Georg Thieme Veriag, Stuttgrat, New York, 1994;
Greene, T.W. and Wuts, P.G.M. Protective Groups in Organic
Synthesis, 2nd ed., J. Wiley: New York, 1991.
2. Kamitori, Y.; Hojo, M.; Masuda, R.; Kimura, T. and Yoshida, T.
J. Org. Chem. 1986, 51, 1427.
3. Kumar, P.; Reddy, R.S.; Singh, A.P. and Pandey, B. Tetrahedron Lett.
1992, 33, 825.
4. Corey, E.J. and Shimoji, K. Tetrahedron Lett. 1983, 24, 169.
5. Ponde, D.E.; Deshpande, V.H.; Bulbule, V.J.; Sudalai, A. and
Gajare, A.S. J. Org. Chem. 1998, 63, 1058; and references therein.
6. Villemin, D.; Labiad, B. and Hamadi, M. J. Chem. Soc. Chem.
Commun. 1992, 1192.
7. Tateiwa, J.; Horiuchi, H. and Uemura, S. J. Org. Chem. 1995, 60, 4039.
8. Arata, K. Adv. Catal. 1990, 37, 165.
9. Hino, M. and Arata, K. J. Chem. Soc. Chem. Commun. 1987, 1259.
10. Manohar, B.; Reddy, V.R. and Reddy, B.M. Synth. Commun. 1998,
28, 3183.

ORDER
REPRINTS
Pt–Mo/ZrO2 SOLID ACID CATALYST
1823
11. Reddy, B.M. and Reddy, V.R. Synth. Commun. 1999, 29, 2789.
12. Hino, M. and Arata, K. Appl. Catal. A: General 1998, 169, 151.
13. Vaudagna, S.R.; Canavese, S.A.; Comelli, R.A. and Figoli, N.S. Appl.
Catal. A: General 1998, 168, 93.
Received in the USAAugust 30, 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/101081SCC100104330