Conversion of alkylbenzenes to carbonyl compounds by NaBrO3 in the presence of NH4Cl and Bu4NHSO4

Article abstract of DOI:10.1081/SCC-120002504

Alkylbenzenes are oxidized selectively to their carbonyl compounds by sodium bromate in the presence of NH₄Cl or Bu₄NHSO₄.

Full text of DOI:10.1081/SCC-120002504

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CONVERSION OF ALKYLBENZENES TO CARBONYL
COMPOUNDS BY NaBrO3 IN THE PRESENCE OF NH4Cl
AND Bu4NHSO4
Ahmad Shaabani a , Ayoob Bazgir a & Masoomeh Abdoli a
a Chemistry Department, Shahid Beheshti University, P.O. Box 19395-4716, Tehran, Iran
Version of record first published: 16 Aug 2006
To cite this article: Ahmad Shaabani, Ayoob Bazgir & Masoomeh Abdoli (2002): CONVERSION OF ALKYLBENZENES
TO CARBONYL COMPOUNDS BY NaBrO3 IN THE PRESENCE OF NH4Cl AND Bu4NHSO4 , Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:5, 675-678
To link to this article: http://dx.doi.org/10.1081/SCC-120002504
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SYNTHETIC COMMUNICATIONS, 32(5), 675–678 (2002)
CONVERSION OF ALKYLBENZENES
TO CARBONYL COMPOUNDS BY
NaBrO3 IN THE PRESENCE OF
NH4Cl AND Bu4NHSO4
Ahmad Shaabani,* Ayoob Bazgir, and
Masoomeh Abdoli
Chemistry Department, Shahid Beheshti University,
P.O. Box 19395-4716, Tehran, Iran
ABSTRACT
Alkylbenzenes are oxidized selectively to their carbonyl
compounds by sodium bromate in the presence of NH4Cl or
Bu4NHSO4.
Bromate ion has recently been studied, as an oxidizing agent in con-
nection with oscillating reactions, such as Belousov-Zhabotinsky reaction.1
However bromate ion as a cheap, light and simple multi oxidant system in
organic syntheses are rarely employed in the literature.
Standard redox potential of the bromate ion, BrOꢀ3 , is 0.61 V in
neutral and alkaline aqueous solution while in aqueous acidic media it
has a potential of 1.52 V.2,3 Therefore, pH of the media drastically affect
standard redox potential and oxidation ability of BrOꢀ3 ion. Due to low
standard redox potential in neutral or weak acidic media, BrOꢀ3 have usually
*Corresponding author.
675
Copyright & 2002 by Marcel Dekker, Inc.
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SHAABANI, BAZGIR, AND ABDOLI
6
been used under strong acidic media such as HBr,4 H2SO4,5 HClO4 and
HOAc7 for the oxidation of organic compounds.
Recently, we have introduced a new method8–10 for oxidation of
organic compounds under mild reaction conditions by using NaBrO3/
NH4Cl8 as oxidizing agent. We wish to report application of NaBrO3 for
the oxidation of alkylbenzenes in the presence of NH4Cl or Bu4NHSO4
to extend the synthetic use of NaBrO3 (Scheme 1). The results of oxidation
of alkylbenzenes to carbonyl compounds by NaBrO3/NH4Cl and NaBrO3/
Bu4NHSO4 are summarized in Table 1.
Scheme 1.
We have observed that NaBrO3/Bu4NHSO4 is a more efficient oxidi-
zing agent than NaBrO3/NH4Cl for the conversion of alkylbenzenes to
aldehydes and ketones. Moreover, tetrabutylammonium bromate as a phase
transfer reagent was produced in situ from tetrabutylammonium hydrogen-
sulfate and sodium bromate which was suitable for application in our
two-phase system. Monosubstituted alkylbenzenes were oxidized at the
benzylic carbon and corresponding aldehydes and ketones were isolated
(Entries 1–4). While o-xylene resisted to oxidation (Entry 6), only one of the
two methyls on p-xylene was oxidized (Entry 5). Diphenylmethane was also
oxidized into benzophenone by NaBrO3/Bu4NHSO4 in high yield (Entry 8).
We found that, the present method is cheap, safe and convenient for
the oxidation of alkylbenzenes to carbonyl compounds in comparison with
cerium ammonium nitrate (CAN),11 NaBrO3/CAN12 and NaBrO3/CeO2/
HOAc,13 in which large quantities of the expensive cerium compounds are
needed.
EXPERIMENTAL
All products are known compounds and were identified by com-
parison of their physical and spectral data with those of authentic samples.
Melting points were determined in open capillaries using an oil-bath and are
not corrected. IR spectra were run at neat films or as KBr pellets on a

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CONVERSION OF ALKYLBENZENES
677
Table 1. Oxidation of Alkylbenzenes to Carbonyl Compounds by NaBrO3ÁNH4Cl
and NaBrO3ÁBu4NHSO4 in Acetonitrile–Water at 80ꢀC
1
Shimadzu 470 spectrometer. H NMR spectra were recorded at 90 MHz on
a JEOL EX-90 instrument with CDCl3 as solvent and Me4Si as an internal
standard.
Typical procedure: Diphenylmethane (0.842 g, 5 mmol) was added to a
mixture of NaBrO3 (0.750 g, 5 mmol) and Bu4NHSO4 (0.400 g, 0.118 mmol)
in aqueous acetonitrile (CH3CN/H2O ¼ 7: 3, (v/v), 10 ml). The mixture was
stirred at 80ꢁC for 24 h, while was followed by TLC. Then the reaction

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SHAABANI, BAZGIR, AND ABDOLI
mixture was extracted with methylene dichloride (2 ꢂ 10 ml). The combined
organic layers were dried over MgSO4. Evaporation of the solvent fur-
nished the product which was isolated as its 2,4-dinitrophenylhydrazone
derivative.
ACKNOWLEDGMENT
Financial support by the Research Council of Shahid Beheshti
University is acknowledged.
REFERENCES
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Received in the UK September 19, 2000

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