Metal salts as novel catalysts for efficient transesterification of β-ketoesters

Article abstract of DOI:10.1081/SCC-100104427

Ethyl/methyl β-ketoesters with alcohols in presence of catalytic amount of anhydrous metal salts (FeSO₄, CuSO₄) undergo smooth transesterification.

Full text of DOI:10.1081/SCC-100104427

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METAL SALTS AS NOVEL CATALYSTS FOR EFFICIENT
TRANSESTERIFICATION OF β-KETOESTERS
a
a
a
B. P. Bandgar , V. S. Sadavarte & L. S. Uppalla
a
School of Chemical Sciences, S.R.T.M. University, Vishnupuri, Organic Chem. Res. Lab.,
Nanded, 431 606, India
Published online: 09 Nov 2006.
To cite this article: B. P. Bandgar , V. S. Sadavarte & L. S. Uppalla (2001) METAL SALTS AS NOVEL CATALYSTS FOR
EFFICIENT TRANSESTERIFICATION OF β-KETOESTERS, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 31:13, 2063-2066, DOI: 10.1081/SCC-100104427
To link to this article: http://dx.doi.org/10.1081/SCC-100104427
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SYNTHETIC COMMUNICATIONS, 31(13), 2063–2066 (2001)
METAL SALTS AS NOVEL CATALYSTS
FOR EFFICIENT TRANSESTERIFICATION
OF b-KETOESTERS
B. P. Bandgar,* V. S. Sadavarte, and L. S. Uppalla
Organic Chem. Res. Lab., School of Chemical Sciences,
S.R.T.M. University, Vishnupuri, Nanded-431 606, India
ABSTRACT
Ethyl/methyl b-ketoesters with alcohols in presence of cataly-
tic amount of anhydrous metal salts (FeSO , CuSO ) undergo
smooth transesterification.
4
4
Transesterification, one of the effective methods for ester synthesis is
usually conducted under acidic or basic conditions. Although quite a few
methods are reported for transesterification, they are not general as far as
b-ketoesters are concerned. Normal reactions of transesterification are equi-
librium driven reactions where usage of excess of one of the reactants in
mandatory to obtain good yields. The reported methods include use of
1
2
3,4
reagents as DMAP, t-butyl acetoacetate, tetrabutyl distannoxanes,
5
solid super acids like sulfated SnO to effect transesterification. In some
2
1
a,b
of these methods
toxic and expensive reagents in relatively large amounts
2
are used. The t-butyl acetoacetate method is restricted to t-butyl esters, thus
lack of generality. It was therefore felt necessary to develop a suitable meth-
odology for interconversion of readily available esters by transesterification.
*
Corresponding author. Fax: 0091-2462-29245.
063
2
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
2
064
BANDGAR, SADAVARTE, AND UPPALLA
We wish to report FeSO and CuSO as novel, efficient, inexpensive and
4
4
neutral catalysts for transesterification of b-ketoesters (Scheme).
Scheme.
Various b-ketoesters were prepared by treating methyl/ethyl b-keto-
ester with equivalent amount of alcohol (primary, secondary, tertiary,
benzylic, allylic) in the presence of catalytic amount of unhydrous FeSO4
or CuSO in at 808C toluene with a distillation condenser to remove metha-
4
nol/ethanol. The effectiveness of protocol is self explained by its selectivity
towards b-ketoesters, whereas normal esters are found to be unreactive. The
selectivity towards transesterification of b-ketoesters is due to the fact that
carbonyl group of ketone enhances the reactivity of ester by chelation with
the catalyst, and this is the crucial step for success of the reaction. The
another most important point to be noted that rather unreactive
t-butanol also gave good result yielding t-butyl ester in moderate yield.
The protocol also allows use of allylic alcohols for transesterification and
1
b
this may be contrasted to the reported method where presence of mol-
ecular sieves in large excess in addition to stoichiometric amounts of DMAP
is required for effective exchange.
In conclusion we have demonstrated that unhydrous FeSO or CuSO4
4
are efficient, inexpensive and general catalysts to effect transesterification.
The superiority and flexibility of the methodology lies in ease of operation
coupled with simplicity in the workup which involves mere filtration of
FeSO or CuSO followed by evaporation of the solvent.
4
4
EXPERIMENTAL
IR spectra were recorded on Bomem MB 104 FTIR Spectro-
1
meter whereas H NMR were recorded on AC 300 F NMR instrument
(
300 MHz).
General Procedure
b-Ketoester (5 mmol), alcohol (5 mmol), unhydrous FeSO /CuSO
(100 mg) in toluene (20 ml) as heated to 80 C in a round bottom flask with
distillation condenser to remove methanol/ethanol. After completion of
4
4
ꢀ

ORDER
REPRINTS
TRANSESTERIFICATION OF b-KETOESTERS
2065
Table. Tansesterification of b-Ketoesters Catalysed by Metal Sulfates
a
5
Yields are of isolated products.
b
Products are characterised by spectral analysis.

ORDER
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2
066
BANDGAR, SADAVARTE, AND UPPALLA
reaction (TLC) the mixture was cooled, filtered and filtrate was concentrated
and chromatographed on SiO (hexane: ethyl acetate, 9:1) to afford ester, a
colourless viscous liquid in excellent yield.
2
ACKNOWLEDGMENT
VSS thanks CSIR, New Delhi for junior research fellowship.
REFERENCES
1. a) Taber, D.F.; Amedio, Jr. J.C. and Patle, Y.K. J. Org. Chem. 1985, 50,
3618. b) Gilbrt, J.C.; Kelly, T.A. J. Org. Chem. 1998, 53, 449.
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27, 2383.
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. Otera, J.; Danoh, N.; Nozaki, H. J. Org. Chem. 1991, 5301.
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37, 223.
Received in the Netherlands September 14, 2000

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