Regeneration of carbonyl compounds by cleavage of C=N bonds under mild and completely heterogeneous conditions

Article abstract of DOI:10.1016/j.tetlet.2003.08.031

Oximes, hydrazones, semicarbazones and azines are converted to the corresponding carbonyl compounds using a combination of Zr(HSO₄) ₄ and wet SiO₂ in good to high yields under completely heterogeneous conditions.

Full text of DOI:10.1016/j.tetlet.2003.08.031

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 7463–7465
Regeneration of carbonyl compounds by cleavage of CꢀN bonds
under mild and completely heterogeneous conditions
F. Shirini,a,* M. A. Zolfigol,b A. Safari,a I. Mohammadpoor-Baltorkc and B. F. Mirjalilid
aDepartment of Chemistry, College of Science, Guilan University, Rasht, Iran
bDepartment of Chemistry, College of Science, Bu-Ali Sina University, Hamadan, Iran
cDepartment of Chemistry, College of Science, Isfahan University, Isfahan, Iran
dDepartment of Chemistry, College of Science, Yazd University, Yazd, Iran
Received 23 June 2003; revised 29 July 2003; accepted 8 August 2003
Abstract—Oximes, hydrazones, semicarbazones and azines are converted to the corresponding carbonyl compounds using a
combination of Zr(HSO4)4 and wet SiO2 in good to high yields under completely heterogeneous conditions.
© 2003 Published by Elsevier Ltd.
The regeneration of carbonyl compounds from stable
and readily prepared oximes, hydrazones, semicarba-
zones and azines has received considerable attention in
recent years.1–4 Since many valuable reactions have
been developed to prepare oximes,5–8 an efficient deoxi-
mation could lead to new methods of preparing car-
bonyl compounds as well.9 Some of the reported
methods of generating carbonyl compounds from
oximes invariably require long reaction times, expensive
or hazardous reagents and the formation of over-oxi-
dized products leading to low yields.10–12 Little atten-
tion has been paid to the conversion of hydrazones,
semicarbazones and azines to the corresponding car-
bonyl compounds, and only a few reports are available
dealing with these reactions.13–16
It should be noted that the above-mentioned reactions
did not proceed using Zr(HSO4)4 or wet SiO2 alone,
even after prolonged heating.
As shown in Table 1, desemicarbazonation reactions
using this method proceed at room temperature and in
the presence of 0.25 mmol of Zr(HSO4)4, while other
reactions proceed using higher amounts of the reagent
under reflux conditions. Therefore, this methodology
can be used for the selective regeneration of carbonyl
compounds from semicarbazones in the presence of
oximes, hydrazones and azines at room temperature.
This is exemplified by competitive reactions between
4-phenylacetophenone semicarbazone and 4-chloroace-
tophenone oxime and between acetophenone semicar-
bazone and 3-acetylpyridine phenylhydrazone (Table 1,
entries 26, 27).
In continuation of our studies on the development of
new methods for cleavage of carbonꢁnitrogen double
bonds,15–17 we wish to report that Zr(HSO4)4 in the
18
The mildness of the reaction conditions, high efficiency,
selectivity, reasonable yields of products, simple and
clean work-up and heterogeneous reaction conditions
are among the advantages of this new method.
presence of wet SiO2, can be used for the efficient
conversion of oximes, hydrazones, semicarbazones and
azines to the corresponding carbonyl compounds. All
reactions were performed under mild and completely
heterogeneous conditions in good to high yields (Table
1).19
Acknowledgements
Keywords: oximes; hydrazones; semicarbazones; azines; hetero-
geneous conditions.
* Corresponding author. Fax: +98 131 3220066; e-mail: shirini@
guilan.ac.ir
We are thankful to the Guilan University Research
Council for partial support of this work.
0040-4039/$ - see front matter © 2003 Published by Elsevier Ltd.
doi:10.1016/j.tetlet.2003.08.031

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F. Shirini et al. / Tetrahedron Letters 44 (2003) 7463–7465
Table 1. Regeneration of carbonyl compounds from their corresponding oximes, hydrazones, semicarbazones and azinesa
Entry
Substrate
Product
Zr(HSO4)4/
Conditions
Time (h)
Yield (%)b
substrate
1
2
4-Methoxybenzaldehyde
semicarbazone
3-Nitrobenzaldehyde
semicarbazone
4-Methoxybenzaldehyde
3-Nitrobenzaldehyde
0.25
0.25
rt
rt
0.03
0.07
90
85
3
4
Acetophenone semicarbazone
4-Bromoacetophenone
semicarbazone
Acetophenone
4-Bromoacetophenone
0.25
0.25
rt
rt
0.25
0.12
90
82
5
6
4-Phenylacetophenone
semicarbazone
5-Methyl-2-furaldehyde
semicarbazone
4-Phenylacetophenone
5-Methyl-2-furaldehyde
0.25
0.25
rt
rt
0.13
0.2
90
90
7
8
9
10
11
12
Cyclopentanone semicarbazone
Cyclohexanone semicarbazone
4-Chlorobenzaldehyde oxime
3-Nitrosalicylaldehyde oxime
4-Chloroacetophenone oxime
2,4%-Dibromoacetophenone
oxime
Cyclopentanone
Cyclohexanone
4-Chlorobenzaldehyde
3-Nitrosalicylaldehyde
4-Chloroacetophenone
2,4%-Dibromoacetophenone
0.25
0.25
0.75
0.75
0.75
0.75
rt
rt
Reflux
Reflux
Reflux
Reflux
0.42
0.3
0.75
4.5
1
85
92
80
85
80
90
0.25
13
14
15
16
17
18
1-Naphthaldehyde oxime
4-Acetylpyridine oxime
a-Tetralone oxime
1-Naphthaldehyde
4-Acetylpyridine
a-Tetralone
0.75
0.75
0.75
0.75
0.75
1.5
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
2.2
0.25
0.3
0.75
0.8
1.5
80
85
82
90
85
90
Camphor oxime
Camphor
Cyclohexanone oxime
4-Methylbenzaldehyde-4-nitro-
phenylhydrazone
Cyclohexanone
4-Methylbenzaldehyde
19
20
4-Acetylpyridine
phenylhydrazone
Cyclopentanone
4-Acetylpyridine
Cyclopentanone
1.5
1.5
Reflux
Reflux
2.8
1.5
85
90
phenylhydrazone
21
22
23
Benzaldehyde azine
4-Hydroxybenzaldehyde azine
2-Ethoxybenzaldehyde azine
Benzaldehyde
4-Hydroxybenzaldehyde
2-Ethoxybenzaldehyde
1.5
1.5
1.5
Reflux
Reflux
Reflux
3.75
3.25
1.25
89
85
85
24
Salicylaldehyde
Salicylaldehyde
1.5
Reflux
2.8
84
25
1.5
Reflux
1
80
26
27
4-Phenylacetophenone
semicarbazone+4-chloro-
acetophenone oxime
Acetophenone
4-Phenylacetophenone
+4-chloroacetophenone
0.25
0.25
rt
rt
0.13
0.25
100c+5c
100c+0c
Acetophenone+3-acetylpyridine
semicarbazone+3-acetylpyridine
phenylhydrazone
a Products were characterized by their physical constants, comparison with authentic samples and IR and NMR spectroscopy.
b Isolated yield.
c GC yield.
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