1104 J. Chin. Chem. Soc., Vol. 52, No. 6, 2005
Bandgar et al.
well with aromatic b-keto esters in good to excellent yields
(entries k-m). It is important to mention that this methodol-
ogy is highly specific only for the b-keto esters. Other esters
like simple esters, a-halo esters and unsaturated esters (n-q)
failed to undergo transesterification. An attempt to carry out
the transesterification of b-keto esters with other nucleo-
philes like phenols, thiophenols and amines (entries r-t) un-
der the same reaction conditions failed. It is also important to
note that NaIO4, KIO4 worked better than CaCl2 in terms of
yields and reaction time.
ACKNOWLEDGEMENT
SSP thanks UGC, New Delhi, for teacher fellowship
under FIP scheme.
Received March 17, 2005.
REFERENCES
The catalysts NaIO4, KIO4 and CaCl2 are weak Lewis
acids and therefore, they might be accepting a loan pair of
electrons from both the carbonyl groups. As a result of this,
carbonyl ester becomes more reactive due to the good leaving
group -OR2 and therefore nucleophilic attack with R3OH is
accelerated and results in the formation of transesterified
products.
1. Otera, J. Chem Rev. 1993, 1449.
2. Benetti, S.; Romagnoli, R.; De Risi, C.; Giampiera, S.;
Vinicio, Z. Chem. Rev. 1995, 95, 1065.
3. Taber, D. F.; Amedio, Jr. J. C.; Patel, Y. K. J. Org. Chem.
1985, 50, 3618.
4. Gilbert, J. C.; Kelly, T. R. J. Org. Chem. 1988, 53, 449.
5. Otera, J.; Dan-oh, N.; Nozaki, H. J. Org. Chem. 1991, 56,
5307.
In conclusion, we have demonstrated that NaIO4, KIO4
and CaCl2 are efficient and selective catalysts for transester-
ification of b-keto esters. The ready availability of these neu-
tral inexpensive commercial catalysts is an important advan-
tage. The superiority and flexibility of this method over the
existing methods lies in ease of operation and the simplicity
in the workup involving filtration of the catalysts. The short
reaction time and good to excellent yields using inexpensive
catalysts are attractive features of this protocol.
6. Otera, J.; Yano, T.; Kawabata, A.; Nozaki, H. Tetrahedron
Lett. 1986, 27, 2383.
7. (a) Chavan, S. P.; Zubaidha, P. K.; Dantale, S. W.;
Keshavaraja, A.; Ramaswamy, A. V.; Ravindranathan, T.
Tetrahedron Lett. 1996, 37, 233. (b) Chavan, S. P.; Subbarao,
Y. T.; Dantale, S. W.; Shivappa, R. Synth Commun. 2001,
31(2), 289.
8. Reddy, B. M.; Reddy, V. R.; Manohar, B. Synth Commun.
1999, 29, 1235.
9. Lakshmi Kantam, M.; Neeraja, B.; Bharathi, B.; Venkat
Reddy, Ch. Catalysis Letters 1999, 62, 67.
10. Balaji, B. S.; Shashidharan, M.; Kumar, R.; Chanda, B. M.
Chem. Commun. 1996, 707. (b) Balaji, B. S.; Chanda, B. M.
Tetrahedron 1998, 54, 13237.
11. Ponde, D. E.; Deshpande, V. H.; Bulbule, V. J.; Sudalai, A.;
Gajare, A. S. J. Org. Chem. 1998, 63, 1058.
12. Kumar, P.; Pande, R. K. Synlett. 2000, 2, 251.
13. Habi, A.; Gravel, D. Tetrahedron Lett. 1994, 35, 4315.
14. (a) Fujoita, T.; Tanak, M.; Norimine, Y.; Seumunc, H. J. Org.
Chem. 1997, 62, 3824. (b) Shapiro, G.; Marli, M. J. Org.
Chem. 1997, 62, 7076.
15. Mottet, C.; Hamelin, O.; Garavel, G.; Depres, J. P.; Greene,
A. E. J. Org. Chem. 1999, 64, 1380.
16. Kumar, B.; Kumar, H.; Parmar, A. Ind. J. Chem. (B) 1993,
32, 292.
17. Pavel, K. Tetrahedron Lett. 1998, 39, 4223.
18. (a) Evans, D. A.; Morrissey, M. M.; Dorow, R. L. J. Am.
Chem. Soc. 1985, 107, 4346. (b) Evans, D. A.; Weber, A. E.
Ibid 1987, 109, 7151.
19. (a) Carol, M. F. J. Am. Chem. Soc. 1940, 704. (b) Kimel, W.;
Cope, A. C. J. Am. Chem. Soc. 1943, 65, 1992.
20. Cordowa, A.; Janda, K. D. J. Org. Chem. 2001, 66, 1906.
21. Bandgar, B. P.; Pandit, S. S.; Uppala, L. S. OPPI 2003,
35(2), 219.
EXPERIMENTAL SECTION
All chemicals are of analytical grade. IR spectra were
recorded on a Bomen FT-IRMB-104 Spectrophotometer with
1
zinc selenide optics. H NMR were recorded on a Brucker
AC-300 spectrometer (300 MHz) in CDCl3 using TMS as an
internal standard. CHN analyses were recorded on a Vario-
EL analyzer. TLC was monitored on 0.25 mm E. Merck pre-
coated silica gel plates (60F-254).
General Procedure
A mixture of b-keto esters (5 mmol), alcohol (5 mmol)
and catalysts (1 mmol) in toluene (20 mL) was heated at 100-
110 °C in a round bottom flask provided with a distillation
condenser to remove methanol or ethanol. After completion
of reaction (TLC), the catalysts were filtered, and the filtrate
was concentrated to get crude product which was purified by
column chromatography on silica gel (petroleum ether:ethyl
acetate) to afford the ester as a viscous colorless liquid in ex-
cellent yields.