Reductive deoximation of aryloximes into hydrocarbons by hydrazine/KOH: A novel application of the wolff-kishner reduction

Article abstract of DOI:10.1080/00397910600638747

We report the reductive deoximation of different substituted aryl, diaryl, and aralkyloximes into the respective methyl or methylene derivatives by hydrazine hydrate/KOH at reflux in satisfactory yields. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600638747

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Reductive Deoximation of Aryloximes into
Hydrocarbons by Hydrazine/KOH: A Novel
Application of the Wolff–Kishner Reduction
H. M. Nanjundaswamy a & M. A. Pasha b
a Chemical Examination Section , Public Health Institute , Bangalore, India
b Department of Studies in Chemistry, Central College Campus , Bangalore
University , Bangalore, India
Published online: 16 Feb 2007.
To cite this article: H. M. Nanjundaswamy & M. A. Pasha (2006) Reductive Deoximation of Aryloximes
into Hydrocarbons by Hydrazine/KOH: A Novel Application of the Wolff–Kishner Reduction, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 36:15,
2183-2187, DOI: 10.1080/00397910600638747
To link to this article: http://dx.doi.org/10.1080/00397910600638747
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Synthetic Communicationsw, 36: 2183–2187, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600638747
Reductive Deoximation of Aryloximes
into Hydrocarbons by Hydrazine/KOH:
A Novel Application of the Wolff–Kishner
Reduction
H. M. Nanjundaswamy
Chemical Examination Section, Public Health Institute, Bangalore, India
M. A. Pasha
Department of Studies in Chemistry, Central College Campus,
Bangalore University, Bangalore, India
Abstract: We report the reductive deoximation of different substituted aryl, diaryl, and
aralkyloximes into the respective methyl or methylene derivatives by hydrazine
hydrate/KOH at reflux in satisfactory yields.
Keywords: Aryloximes, deoximation, hydrocarbons, hydrazine hydrate, Wolff–
Kishner reduction
INTRODUCTION
Carbonyl compounds occupy a central position in organic syntheses. Oximes
are used extensively for the protection[1] of carbonyl function. Numerous
methods have been developed for their oxidative,[2] reductive,[3] and hydro-
lytic[4] conversion to carbonyl compounds, dehydration to nitriles,[5]
reduction to amines,[6] and conversion to amides[7] by the Beckmann
rearrangement. There are no reports available in the literature on the direct
conversion of oximes to hydrocarbons; hence the recovery of the parent
Received January 6, 2006
Address correspondence to M. A. Pasha, Department of Studies in Chemistry,
Central College Campus, Bangalore University, Bangalore 560 001, India. E-mail:
m_af_pasha@yahoo.co.in
2183

2184
H. M. Nanjundaswamy and M. A. Pasha
hydrocarbon from an oxime derivative is interesting, which led us to develop a
method for the key transformation in organic syntheses. Herein we present a
transformation of oximes to the corresponding hydrocarbons as shown in
Scheme 1.
In a typical experiment, benzophenone oxime (10 mmol) is treated with
hydrazine hydrate (2 mL) and 15 mL of diethylene glycol as a solvent. The
contents are refluxed for 1 h and then subjected to the Wolff–Kishner
procedure. After completion of the reaction (monitored by TLC, with
light petroleum [40–608C] and comparison with authentic hydrocarbon
prepared in a parallel experiment from benzophenone by the Clemmensen
reduction), the product was found to be diphenylmethane in 85% yield.
Encouraged by this result, we extended this reaction to other substituted
oximes. To verify the suitability of the method for reductive deoximation
of oximes into the respective hydrocarbons, different substituted oximes
were subjected to the same reaction condition, and the results are summar-
ized in Table 1. It is clear that different substituted oximes can be readily
converted into the respective hydrocarbons under these reaction conditions
in high yields. Although diaryl and arylalkyloximes furnish the expected
methyl or methylene derivatives, dialkyl oximes such as camphor oxime,
carvone oxime, and cyclohexyl oxime give a complex mixture of
products under these reaction conditions. The Wolff–Kishner reduction of
carbonyl compounds by hydrazine hydrate, in the presence of a base
either in an autoclave or in a sealed tube, into the respective hydrocarbons
is known to proceed via the formation of respective hydrazones.[8] Recently,
we have shown that oximes can readily be converted into the respective
hydrazones in excellent yields on treatment with hydrazine hydrate in
refluxing ethanol.[9] Because oximes can be readily converted into hydra-
zones, the present reaction is expected to proceed by the formation of
hydrazone intermediates. A plausible mechanism for the formation of
hydrocarbons from oximes via hydrazone intermediates is shown in
Scheme 2.
EXPERIMENTAL
1
The H NMR spectra of all the products were recorded on Bruker 400-MHz
and 500-MHz spectrometers as CDCl3 solutions with TMS as the internal
standard.
Scheme 1. R ¼ phenyl or substituted phenyl groups; R0 ¼ alkyl or aryl group.

Reductive Deoximation of Aryloximes
2185
Table 1. Reductive deoximation of substituted oximes into the corresponding
hydrocarbons by hydrazine/KOH/diethylene glycol at refluxa
Bp or mp (8C)
Total Yield
time (h) (%) Found
Entry
1
Oximes
Productb
Lit.[10]
4.5
85
82
79
163c
107d
131d
268d
2
3
4.5
110.6
136.2
4.75
4
5
4.5
4.5
80
78
43c
42–45
174
168d
6
7
4.75
4.5
75
77
117e 221–222
179d 184–185
aCaution: Hydrazine hydrate is toxic and corrosive in nature, handle carefully.
1
bProducts were characterized by comparison of their IR and H NMR spectra with
authentic samples.
cMelting point.
dBoiling point at 690 Torr.
eBoiling point at 5 Torr.
General Procedure
A solution of oxime (10 mmol), diethylene glycol (15 mL), and hydrazine
hydrate (2 mL, 99–100%) was refluxed for 1 h. After the removal of the
unreacted hydrazine hydrate and water by distillation between 100–1208C,

2186
H. M. Nanjundaswamy and M. A. Pasha
Scheme 2.
the reaction mixture was treated with KOH pellets (30 mmol) under reflux for
3.5 h. Water (25 mL) was added and extracted with ether (25 mL). The ether
layer was washed successively with water, dil. HCl, and water; dried over
anhydrous Na2SO4; and concentrated. The crude was then subjected to
silica-gel chromatography using light petroleum–acetone (95:5) as an
eluent to get the pure hydrocarbon.
CONCLUSION
In conclusion, we have developed a novel reductive deoximation of
aryl oximes into respective hydrocarbons in high yields without the need
for specialized reducing agents.
ACKNOWLEDGMENT
H. M. Nanjundaswamy thanks the joint director of Public Health Institute and
the commissioner of H & F W Services, Bangalore, India, for encouragement
and SIF, Indian Institute of Science, Bangalore, India for providing the NMR
facility.
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