Oxidation of benzyl alcohols and acyloins with (NO3)3CeBrO3

Article abstract of DOI:10.1081/SCC-100103267

Trinitratocerium(IV) bromate (TNCB) was prepared by the reaction of cerium(IV) ammonium nitrate (CAN) with sodium bromate. The oxidizing ability of this compound was observed in the oxidation of benzyl alcohols and acyloins to the corresponding carbonyl compounds.

Full text of DOI:10.1081/SCC-100103267

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OXIDATION OF BENZYL
ALCOHOLS AND ACYLOINS
WITH (NO3)3CeBrO3
F. Shirini a , H. Tajik a , A. Aliakbar a & A. Akbar a
a Department of Chemistry, Faculty of Sciences,
Guilan University, Rasht, Iran
Version of record first published: 16 Aug 2006.
To cite this article: F. Shirini , H. Tajik , A. Aliakbar & A. Akbar (2001):
OXIDATION OF BENZYL ALCOHOLS AND ACYLOINS WITH (NO3)3CeBrO3 , Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 31:5, 767-770
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SYNTHETIC COMMUNICATIONS, 31(5), 767–770 (2001)
OXIDATION OF BENZYL ALCOHOLS AND
ACYLOINS WITH (NO3)3CeBrO3
F. Shirini,* H. Tajik, A. Aliakbar, and A. Akbar
Department of Chemistry, Faculty of Sciences, Guilan
University, Rasht-Iran
ABSTRACT
Trinitratocerium(IV)bromate (TNCB)was prepared by
the reaction of cerium(IV)ammonium nitrate (CAN)with
sodium bromate. The oxidizing ability of this compound
was observed in the oxidation of benzyl alcohols and acyloins
to the corresponding carbonyl compounds.
Cerium(IV)compounds represent the most notable oxidants among
lanthanide reagents. In particular, ceric ammonium nitrate (CAN)has
been utilized extensively for a variety of oxidative transformations.1
Unfortunately oxidation with this reagent suffers from various disadvan-
tages.2 This reagent is not effective in the oxidation of benzyl alcohol in
refluxing acetonitrile and after 2.5 h, benzyl alcohol was isolated intact.3
Sodium bromate which has also been used in the oxidation of
organic compounds,4 was also quite ineffective in the oxidation of benzyl
alcohol.3
In this communication we report a synergistic effect between ceric
ammonium nitrate (CAN)and sodium bromate in trinitratocerium(IV)
bromate, (NO3)3CeBrO3,5–7 which is quite stable and capable of oxidizing
benzyl alcohols and acyloins in refluxing acetonitrile.
* Corresponding author.
767
Copyright & 2001 by Marcel Dekker, Inc.
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768
SHIRINI ET AL.
Table 1. Oxidation of Benzyl Alcohols and Acyloins with TNCB in Refluxing
Acetonitrile
Oxidant Reaction
Substrate Time (h)Product
Yield
%
Entry
Substrate
1
2
3
4
5
6
7
8
9
Benzyl alcohol
4
4
4
4
4
6
1
1
1
2.5
5.5
5
Benzaldehyde
92
2-Chlorobenzyl alcohol
4-Chlorobenzyl alcohol
4-Bromobenzyl alcohol
4-Methyl benzyl alcohol
1-Phenyl ethanol
Benzoin
2-Chlorobenzaldehyde 90
4-Chlorobenzaldehyde 85
4-Bromobenzaldehyde 86
4-Methylbenzaldehyde 85
7.5
6.5
2.5
0.25
0.25
0.75
Acetophenone
Benzil
4,40-Dimethoxybenzil
82
92
85
90
4,40-Dimethoxybenzoin
Furoin
Furil
Different benzyl alcohols were oxidized to the corresponding benzal-
dehydes (Table 1). Acyloins, as ꢀ-hydroxy ketones, were also effectively
oxidized to the corresponding diketones with quantitative amounts of the
reagent, in low reaction times and in high yields (Table 1).
It is noted that the over-oxidation of the produced benzaldehydes to
their corresponding benzoic acid and C-C bond cleavage of the acyloins,
which are the common reactions in the oxidations with ceric ammonium
nitrate,8,9 were not observed during the course of the reaction.
In order to show the synergistic effect in TNCB we have compared
some of the results with some of those obtained by CAN and NaBrO3 in the
same conditions3 (Table 2).
The ease of preparation, handling, stability and mildness of this
compound makes it a particular bench reagent. Full investigations of the
oxidation of different classes of organic compounds with this reagent are
under way.
EXPERIMENTAL
Preparation of Trinitratocerium(IV) Bromate(TNCB)
To a solution of sodium bromate (0.151 g, 1 mmol)in water (10 ml)at
70ꢀC a solution of CAN (0.548 g, 1 mmol)in water (3 ml)was added with
vigorous stirring. The resulting mixture was stirred at 70ꢀC for 30 min, and
cooled to room temperture, whereupon a yellow precipitate was produced.

BENZYL ALCOHOLS AND ACYLOINS
769
Table 2. Comparison of Some of the Results Obtained by the Oxidation with
TNCB(1)with Some of Those Obtained by CAN(2)and NaBrO
Acetonitrile
in Refluxing
3
(Oxidant/Substrate)(h)(Yield%)
(1)(2()3)
Entry
Substrate
Product
1
2
Benzyl alcohol
Furoin
Benzaldehyde
Furil
(4)(2.5)(92)
(1)(0.75)(90)
(4)(2.5)(0)
(1)(2)(0)
(4)(2.5)(0)
(1)(2)(0)
This precipitate was collected by filteration, washed with water and acetone
several times and dried in vacuo (0.317 g, 70%).
General Procedure for the Oxidation of Benzyl Alcohols and
Acyloins with TNCB
A solution of the substrate (1 mmol)in acetonitrile (3 ml)was treated
with 1–6 molar equivalents of the reagent and the reaction mixture was
refluxed with stirring for 0.25–6 h. The progress of the reaction was mon-
itored by TLC. After completion of the reaction, the reaction mixture was
cooled, filtered and the solid residue was washed with acetonitrile several
times (2Â5 ml). Evaporation of the solvent followed by column chromato-
graphy on silica gel, gave the corresponding carbonyl compounds from
good to high yields. The product of each reaction was identified by its
refractive index (nD)or mp, IR and NMR spectra and was compared
with those reported for the authentic samples.10–12
ACKNOWLEDGMENT
We are thankful to Guilan University Research Council for the partial
support of this work.
REFERENCES
1. Ho, T.-L.; Organic Syntheses by Oxidation with Metal Compounds;
Mijs, W.J., de Jonge. C.R.H.I., Eds.; Plenum Press: New York, 1986.
2. Firouzabadi, H.; Iranpoor, N. Synth. Commun. 1983, 13, 1143.

770
SHIRINI ET AL.
3. Shirini, F.; Tajik, H.; Aliakbar, A.; Akbar, A. Our personal observa-
tions.
4. Veeraiah, T.; Periasmay, M. Synth. Commun. 1989, 19, 2151.
5. IR (KBr): 1620, 1380, 840 Cmꢀ1 (characteristics for the nitrate anion)
and 760 Cmꢀ1 (characteristics for the bromate anion). See Miller, F.A.;
Wilkins, C.H. Anal. Chem. 1952, 24, 1253.
6. The analysis of nitrate and bromate anions and cerium(IV)in the
precipitate showed that Ce(IV)/NOꢀ3 /BrO3ꢀ is 1/3/1.
7. This compound is insoluble in water, ethanol, acetone, acetonitrile,
dichloromethane, benzene and toluene. It gradually decomposes
above 370ꢁC to an unidentified product.
8. Ho, T.-L. Synthesis 1970, 560.
9. Ho, T.-L. Synthesis 1973, 347.
10. Fluka Catalog, Chemicals and Biochemicals (1996–97).
11. Aldrich Catalog, Handbook of Fine Chemicals (1990–91).
12. Aldrich Library of Infrared Spectra, J. Pouchet Charles. Aldrich
Chemical Company, Inc (1970).
Received in the U.K. December 20, 1999