Facile one-step conversion of ketones into α-azidoketones using [hydroxy(tosyloxy)iodo]benzene and sodium azide in the presence of a phase-transfer catalyst under solvent-free conditions

Article abstract of DOI:10.1080/00397910600602644

We have described a one-step, solvent-free synthesis of α-azidoketones from the corresponding ketones that requires relatively benign [hydroxy(tosyloxy) iodo]-benzene reagent, sodium azide, and phase-transfer catalyst at room temperature. Generality of th

Full text of DOI:10.1080/00397910600602644

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Facile One‐Step Conversion of
Ketones into α‐Azidoketones using
[Hydroxy(tosyloxy)iodo]benzene and Sodium
Azide in the Presence of a Phase‐Transfer
Catalyst under Solvent‐Free Conditions
Dalip Kumar a , Swapna Sundaree a & V. S. Rao a
a Chemistry Group , Birla Institute of Technology and Science , Pilani, India
Published online: 18 Aug 2006.
To cite this article: Dalip Kumar , Swapna Sundaree & V. S. Rao (2006) Facile One‐Step Conversion of
Ketones into α‐Azidoketones using [Hydroxy(tosyloxy)iodo]benzene and Sodium Azide in the Presence of a
Phase‐Transfer Catalyst under Solvent‐Free Conditions, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 36:13, 1893-1896
To link to this article: http://dx.doi.org/10.1080/00397910600602644
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Synthetic Communicationsw, 36: 1893–1896, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600602644
Facile One-Step Conversion
of Ketones into a-Azidoketones
using [Hydroxy(tosyloxy)iodo]benzene
and Sodium Azide in the Presence
of a Phase-Transfer Catalyst
under Solvent-Free Conditions
Dalip Kumar, Swapna Sundaree, and V. S. Rao
Chemistry Group, Birla Institute of Technology and Science, Pilani, India
Abstract: We have described a one-step, solvent-free synthesis of a-azidoketones
from the corresponding ketones that requires relatively benign [hydroxy(tosyloxy)
iodo]-benzene reagent, sodium azide, and phase-transfer catalyst at room temperature.
Generality of the protocol has been demonstrated by synthesizing various a-azidoke-
tones high in yield and purity within a short time.
Keywords: a-Azidoketone, [hydroxy(tosyloxy)iodo]benzene, phase-transfer catalyst,
solvent-free synthesis
INTRODUCTION
a-Azidoketones are well known for their application in organic synthesis,
particularly in the synthesis of heterocyclic compounds such as pyrroles,[1]
1-pyrazines,[2] and oxazoles.[3] Pyrolysis of a-azidoketones leads to a-imino-
ketones or acylimidazoles if b-carbon atoms are not present.[4] The oxidative
Received December 20, 2005
The work entitled “A Facile One-Step Conversion of Ketones into a-Azidoketones
Using [Hydroxy(tosyloxy)iodo]benzene and Sodium Azide in Presence of Phase
Transfer Catalyst Under Solvent-Free Conditions” has not been published elsewhere
and that it has not been submitted simultaneously for publication elsewhere.
Address correspondence to Dalip Kumar, Chemistry Group, Birla Institute of Tech-
nology and Science, Pilani 333 031, India. E-mail: dalipk@bits-pilani.ac.in
1893

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D. Kumar, S. Sundaree, and V. S. Rao
ring cleavage of steroidal a-azidoketones to produce cyano carboxylic acids
has also been reported.[5]
a-Azidoketones photochemically and thermally are labile compounds,
and utilized in the generation of other functionalities such as amine via
reduction, imines via rearragement, and triazoles and related heterocycles
via cycloaddition. Therefore, many methods for the synthesis of a-azidoke-
tones have been reported in the literature. Most commonly, the a-azidoke-
tones are prepared by the nucleophillic substitution reaction of
a-haloketones or a-nosyloxy ketone.[4,6] More recently, the direct conversion
of olefins into a-azidoketones was effected by azidotrimethylsilane–
chromium trioxide.[7] Apart from these, a novel oxidative conversion of trii-
sopropylsilyl enol ethers into a-azidoketones with sodium azide and ceric
ammonium nitrate has been reported.[8] We report a one-step synthesis of
a-azidoketones from the corresponding ketones using [hydroxy(tosylox-
y)iodo]-benzene and sodium azide in presence of a phase-transfer catalyst
under solvent-free conditions (Scheme 1).
RESULTS AND DISCUSSION
Initially, we attempted to synthesize a-azidoacetophenone (Table 1, entry 1)
by mixing acetophenone with [hydroxy(tosyloxy)iodo]benzene, followed by
sodium azide. No trace of a-azidoacetophenone was detected even after
48 h. However, when we added an equimolar quantity of tetrabutylammonium
bromide (TBAB) to the reaction mixture, we observed formation of exclu-
sively a-azidoacetophenone in high yield. [A representative procedure is
this: 1-phenyl-1,3-butandione (100 mg, 0.62 mmol) and [hydroxy(tosyloxy)iodo]
benzene (300 mg, 0.74 mmol) were mixed for 3 min with a pestle and mortar at
room temperature. The reaction mixture turned creamish yellow; sodium
azide (40 mg, 0.60 mmol) and tetrabutylammonium bromide (35 mol %)
were added and mixed with the contents for 3 min. The dark brown
semisolid reaction mixture was taken into water and extracted with dichloro-
methane (5 mL). The organic phase was dried over anhydrous sodium sulfate
and concentrated on a rotary evaporator. The residue was percolated through a
column of silica gel using ethyl acetate/hexane (1/9) as eluent to afford the
pure product in 96% yield.] The formation of a-azidoacetophenone (caution:
explosive) was indicated by a characteristic peak of azide functionality in IR
Scheme 1.

Ketones into a-Azidoketones
1895
Table 1. Synthesis of some a-azidoketones from ketones under solvent-free conditions
Time Yielda
IR
(%) n(cm21
)
Entry
Substrate
Product
(min)
1
40
87
94
2100
2100
2
3
40
40
89
2100
4
5
25
6
82
96
2110
2125
6
7
8
20
5
90
82
65
2125
2050
2090
10
9
10
76
2095
aYields refer to pure isolated products, which were identified by the comparison of
their IR and NMR spectral data with those of the known compounds.
at n ¼ 2100cm21. The amount of TBAB required for optimum condition was
35 mol%. Following this procedure, synthesis of substituted a-azidoketones
(Table 1, entries 2–3) was undertaken, and we found that all the substituted acet-
ophenones behaved similarly. In the case of b-dicarbonyl compounds (Table 1,
entries 4–6), the reaction is faster and yields of the products were high. Among

1896
D. Kumar, S. Sundaree, and V. S. Rao
the b-dicarbonyl compounds, the 1-phenyl-butan-1,3-dione most rapidly
generates in situ the corresponding a-tosyloxyketone and ultimately a-azidoke-
tone. The scope of this protocol was further extended for the synthesis of cyclic
a-azidoketones (Table 1, entries 7–9). In case of cyclic ketones, both in situ
generation of tosyloxyketones and subsequent reaction with sodium azide
were rapid. All the cyclic ketones reacted under analogous conditions to form
the corresponding cyclic a-azidoketones in good yields.
In conclusion, we have developed a one-step synthesis of a-azidoketones
from ketones.
ACKNOWLEDGMENTS
Financial support from the Institute is gratefully acknowledged.
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