December 1998
SYNLETT
1345
Regeneration of Ketones from Oximes in Solid State on Wet Silica Supported Sodium
Bismuthate under Microwave Irradiation
Alok Kumar Mitra*, Aparna De and Nilay Karchaudhuri
Department of Chemistry, University of Calcutta, 92, Acharya Prafulla Chandra Road, Calcutta - 700 009, India
Fax: +91 33 351 9755
Received 5 September 1998
Abstract: Microwave irradiation of ketoximes on wet silica supported
sodium bismuthate under environmentally friendly solvent-free
condition provides a fast, efficient and simple method for regeneration
of ketones in high yields.
oven (2450 MHz) operating at full power (1200 w) for the specified
time. After completion of the reaction (monitored by TLC) the product
was extracted with dichloromethane (3x10 ml). All the compounds
1
obtained were characterised by H NMR spectroscopy and by
comparison with infrared spectra of authentic samples.
Protection of carbonyl compounds as oximes is of great interest to
organic chemists, as they are readily prepared and highly stable
1
compounds . Oximes are extensively used for purification and
characterisation of carbonyl compounds and in the preparation of
2
amides via Beckmann rearrangement . Their syntheses from non-
3
carbonyl compounds provide an alternative route to aldehydes and
ketones. Although quite a number of methods for the conversion of
oximes to carbonyls are available, the discovery of newer efficient and
fast methods is the goal of the organic chemists. Some of the methods
reported earlier for deoximation of carbonyl compounds consist of
4
a
4b
periodic
acid
,
pyridinium
chlorochromate
,
pyridinium
4
c
4d
chlorochromate-H O , triethylammonium chlorochromate , Raney
2
2
4
e
4f
nickel
,
chromic anhydride-chlorotrimethylsilane , dinitrogen
4
g
4h
4i
4j
tetroxide , Dowex-50 , dimethyl dioxirane , t-butylhydroperoxide ,
persulphate-silica4k
,
manganese
4n
triacetate ,
4l
N-
.
ammonium
4
m
4o
haloamides , sodium periodate-silica , Des-Martin periodinane
Some of these reagents suffer from one or the other disadvantages like
4
j
4b,c
long reaction time , difficulties in isolation of products , and also
lacking easy availability and causing explosion under excessive heating
during preparation
4
o
.
Recently the growing interest in the application of microwave
5
irradiation in chemical reaction enhancement is due to high reaction
rates and formation of cleaner products. The solvent-free reactions4
under this condition are especially appealing for providing an
environmentally benign system. Herein we wish to report a solid state
n,6
In conclusion, we have developed a solvent-free method for the facile
cleavage of a variety of ketoximes using wet silica supported sodium
bismuthate under microwave irradiation.
deoximation procedure using sodium bismuthate (NaBiO ) supported
3
on wet silica under microwave irradiation. The reaction proceeds
efficiently in high yields at ambient pressure within a few minutes
(
Table 1). To the best of our knowledge, this is the first report of
Acknowledgement: The authors are grateful to the CSIR, the UGC,
New Delhi and the University of Calcutta for providing financial
support for this work.
deoximation using sodium bismuthate.
Among several mineral supports viz. alumina, silica, clay etc. examined,
silica was found to give best results. The optimum ratio of the substrate
to the reagent for deoximation is found to be 1:2 (mole/mole). The
reaction remains incomplete if lower amounts of the reagent are used or
in the absence of silica support. The dry reagent decomposes under
microwave irradiation. By conventional heating method (oil bath) at
References and Notes:
1.
Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis, John Wiley and Sons, New York, 1991, p 214.
2
.
a) Donaruma, L. G.; Heldt, W. Z. Organic Reactions 1960, 11, 1;
b) Bosch, A. I.; Cruz, P.; Diez-Barra, E.; Loupy, A.; Langa, P.
Synlett. 1995, 1259.
1
10ºC, the reaction was still incomplete after 24 h. The reagent has wide
applicability for deoximation of aliphatic, aromatic ketoximes and
dioximes of α- and β-diketones. However, the deoximation of
aldoximes under similar reaction condition results in a complex mixture
of products.
3.
4.
a) Kabalka, G. W.; Pace, R. D.; Wadgaonkar, P. P. Synth. Commun.
1990, 20, 2453; b) Barton, D. H. R.; Beaton, J. M. J. Am. Chem.
Soc. 1961, 83, 4083; c) Barton, D. H. R.; Beaton, J. M.; Geller, L.
E.; Pechet, M. J. Am. Chem. Soc. 1961, 83, 4076.
General procedure : The reagent was prepared by adding silica gel (20
g, 230-400 mesh, SRL) to a stirred solution of NaBiO3 (6.5 g, 23.35
mmol) in 30 ml of water. After removal of water, the resulting powder
was dried in an oven at 120ºC for 12 h. The reagent (2.3 g) was
moistened with water (0.5 ml) and was mixed with the neat ketoxime (1
a) Araujo, H. C.; Ferriera, G. A. L.; Mahajan, J. R. J. Chem. Soc.
Perkin Trans. 1 1974, 2257; b) Maloney, J. R.; Lyle, R. E.;
Saavedra, J. E.; Lyle, G. G. Synthesis 1978, 212; c) Drabowiez, J.
Synthesis 1980, 125; d) Rao, C. G.; Radhakrishna, A. S.; Singh, B.
B.; Bhatnagar, S. P. Synthesis 1983, 808; e) Curran, D. P.; Brill, J.
7
mmol) in a 25 ml Erlenmeyer flask . The flask was then placed in an
alumina bath (heat sink) inside a BPL-SANYO domestic microwave