Tetrameric DABCO-bromine complex: A novel reagent for regeneration of carbonyl compounds from aldoximes and ketoximes

Article abstract of DOI:10.1080/00397910500406476

An efficient and convenient conversion of aldoximes and ketoximes to the corresponding carbonyl compounds with tetrameric DABCO-bromine complex is reported. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910500406476

Synthetic Communicationsw, 36: 581–585, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500406476
Tetrameric DABCO–Bromine Complex: A
Novel Reagent for Regeneration of Carbonyl
Compounds From Aldoximes and Ketoximes
Majid M. Heravi and Fateme Derikvand
Department of Chemistry, School of Sciences, Azzahra University,
Vanak, Tehran, Iran
Mitra Ghassemzadeh
Chemistry & Chemical Engineering Research Center of Iran, Tehran, Iran
Abstract: An efficient and convenient conversion of aldoximes and ketoximes to the
corresponding carbonyl compounds with tetrameric DABCO–bromine complex is
reported.
Keywords: Aldehydes, DABCO, deprotection, ketones, oximes
Protection of carbonyl compounds as oximes is of great interest to synthetic
chemists, because they are readily prepared and highly stable compounds.[1]
They are useful synthetic intermediates en route to amines[2] and nitriles.[3]
Oximes are extensively used for characterization of carbonyl compounds
and in the preparation of amides via Beckman rearrangement.[4] Because
oximes can be prepared from noncarbonyl compounds,[5–9] the regeneration
of carbonyl compounds from oximes provides an alternative method for
preparation of aldehydes and ketones.
Several methods for the regeneration of carbonyl compounds from their
oximes such as clay-supported ammonium chlorochromate,[10] clyfen,[11]
thallium(III) nitrate/HZSM5,[12] zeofen,[13] oxone/wet alumina,[14] bismuth
Received in Poland July 28, 2005
Address correspondence to Majid M. Heravi, Department of Chemistry, School
of Sciences, Azzahra University, Vanak Tehran, Iran. Fax: 00982/8047861;
E-mail: mmh1331@yahoo.com
581

582
M. M. Heravi, F. Derikvand, and M. Ghassemzadeh
nitrate/DABCO (1,4–Diazobicyclof2,2,2goctane),[15] and clay-supported
bistrimethysilyl chromate (BTSC)[16] have been reported by our group.
Recently the problem of regeneration of aldehydes from oximes from
available methods has been extensively reviewed.[17] Although some of
these methods are carried out under mild reaction conditions, most of them
require strong acidic media, a strong oxidizing agent, rare or poisonous
reagents, or sometimes long reaction times. Thus there is still a need to
develop a new and facile procedure for the regeneration of carbonyl
compounds from oximes.
In view of these limitations, we decided to develop a practical and general
approach for oxidative cleavage of oximes. We have recently reported on the
application of hexamethylenetetramine–bromine[18] as an efficient oxidant
and the synthesis and structure elucidation of tetrameric DABCO-bromine
(TDB) as a new oxidative active bromine complex for use as a selective
oxidant for oxidation of alcohols to carbonyl compounds.[19]
To broaden the scope and applications of this new and efficient reagent,
in this communication we report the oxidative cleavage of aldoxime and
ketoxime derivatives using this new reagent.
The oxidation reaction is conduced by stirring the TDB complex with
aldoximes and ketoximes in a mixture of chloroform and water at room temp-
erature (Scheme 1). Various aldoximes and ketoximes were converted to
parent carbonyl compounds. No overoxidation to carboxylic acid was
observed in any case. The results are shown in Table 1.
TDB is very stable at room temperature, is not affected by ordinary
exposure to light, air, or water, and has no offensive odor of bromine or
amine. Ease of workup and the stability of the regent make it a safe and con-
venient source of active bromine.
In conclusion, the present communication describes a simple, inexpen-
sive, efficient, and convenient conversion of oximes to their carbonyl
compounds using the TDB complex. We hope that the present deprotection
methodology of oximes find wide application in organic synthesis because
of the simplicity of workup and use of readily prepared oxidant under
natural and mild conditions.
EXPERIMENTAL
All products were known, and their physical and spectroscopic data were
compared with those of authentic samples.
Scheme 1.

Table 1. Oxidative cleavage of oximes with tetrameric DABCO–bromine (TDB)
Mpb/bpc(8C)
Reported[20]
Time
(min)
Yielda
(%)
Entry
Substrate
Product
Observed
1
2
3
4
5
6
7
8
9
2-Nitro-benzaldoxime
3-Nitro-benzaldoxime
4-Nitro-benzaldoxime
Benzophenone oxime
4-Nitro-benzophenone oxime
4-Methyl-banzaldoxime
2-Methoxy-benzaldoxime
Heptanaldoxime
2-Nitro-benzaldehde
3-Nitro-benzaldehde
4-Nitro-benzaldehde
Benzophenone
90
90
92
94
93
88
90
50
51
80
63
44
57
43.4–44b
58b
60
45
102
201
82
103b
202c
4-Nitro-benzophenone
4-Methyl-benzaldehyde
2-Methoxy-benzaldehyde
Heptanal
75
80–82b
204–205c
243–244c
171c
120
60
204
243
170
222
60
25
3-Phenyl-propanaldoxime
3-Phenyl-propanal
223c
aYields were obtained by GC analysis.
bMelting point.
cBoiling point.

584
M. M. Heravi, F. Derikvand, and M. Ghassemzadeh
Preparation of the Tetrameric DABCO–Bromine (TDB)
A solution of bromine (20.0 g, 125 mmol) in chloroform (100 mL) was
added dropwise with stirring to a solution of DABCO (6.72 g, 60 mmol)
in chloroform (100 mL). A yellow solid appeared as the bromine was
taken up. The mixture was stirred for an additional 1 h; then the yellow
solid was collected by vacuum filtration. Yield 23.12 g (98%), decomp.
160–1658C.
Regeneration of Carbonyl Compounds from Their Oximes by TDB:
General Procedure
A mixture of oxime (1 mmol) and TDB (0.262 g, 0.166 mmol) in chloroform
(10 mL) and water (3 mL) was stirred at room temperature (258C) until the
yellow color of the complex disappeared. The progress of the reaction was
monitored by TLC using petroleum ether–ethyl acetate (10:3) as eluent.
Upon the completion of reaction, the chloroform layer was washed succes-
sively with solution of 1% HCl, 3% sodium bicarbonate, and water. The
organic layer was dried over MgSO4, filtered, and evaporated to dryness
under reduced pressure to afford the corresponding carbonyl compounds in
good yields.
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