An efficient transition metal-free aziridination of alkenes with Chloramine-T using aqueous H2O2/HBr

Article abstract of DOI:10.1016/j.tetlet.2004.09.155

The combination of aqueous H₂O₂ and HBr was found to be an efficient transition metal-free green catalytic system for the aziridination of a variety of alkenes under very mild reaction conditions.

Full text of DOI:10.1016/j.tetlet.2004.09.155

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 8731–8732
An efficient transition metal-free aziridination of alkenes with
Chloramine-T using aqueous H2O2/HBr
Suman L. Jain, Vishal B. Sharma and Bir Sain*
Chemical and Biosciences Division, Indian Institute of Petroleum, Dehradun 248 005, India
Received 23 July 2004; revised 14 September 2004; accepted 20 September 2004
Abstract—The combination of aqueous H2O2 and HBr was found to be an efficient transition metal-free green catalytic system for
the aziridination of a variety of alkenes under very mild reaction conditions.
Ó 2004 Elsevier Ltd. All rights reserved.
10
Aziridination of alkenes is an important transformation
as aziridines are very important synthetic building
blocks, extensively used as electrophiles1 and synthetic
intermediates in the preparation of a wide range of
nitrogen-containing compounds.2 Among the various
methods reported in the literature, the metal catalyzed
reaction of nitrenes, generated in situ, with olefins is
an efficient method for the preparation of aziridines.
In this context [N-(p-tolylsulfonyl)imino]phenyliodinane
(PhI@NTs)3 has been shown to be a very convenient
nitrene precursor for aziridination in the presence of sev-
eral transition metal-based catalysts.4 However, there
are drawbacks with the use of PhI@NTs, it is expensive,
yields iodobenzene in equimolar amounts, and oxygen-
ated hydrocarbons are dominant by-products.5 N-Chlo-
ronium salts of sulfonamides such as Chloramine-T
together with several metal catalysts have been used as
a cheap, convenient, and practical nitrogen source for
aziridination,6 but the methods suffer from certain draw-
backs such as the use of transition metals as catalysts
and lower yields of the products due to competing
hydrogen abstraction and insertion reactions. In recent
years much attention has been paid to the development
of transition metal-free catalyst systems in order to
obtain more efficient processes. For example, bromine-
based catalysts such as phenyltrimethylammonium
tribromide,7 pyridiniumbromide perbromide,8 and N-
bromamides9 are very efficient catalysts for the aziridin-
ation of olefins using Chloramine-T as the nitrogen
source, but these systems are not easily accessible. A
recent report by Neumann and co-workers
on the
use of a combination of hydrogen peroxide and hydro-
halic acid as a green halogenating agent for arenes in-
spired us to explore the potential of such a transition
metal-free system for aziridination of alkenes. In this
letter we describe, for the first time, a very simple and
highly efficient aziridination of alkenes with Chloramine-
T using aqueous H2O2 and HBr.
The aziridination of a variety of alkenes was carried out
to test the generality of this method and the results are
summarized in Table 1. All the alkenes used were effi-
ciently converted to their corresponding aziridines in
excellent yields with Chloramine-T using aqueous
H2O2/HBr as catalyst (20mol%) in acetonitrile at room
temperature, in the presence of MgSO4 as a water-trap-
ping agent under a nitrogen atmosphere (Scheme 1).
Among the various alkenes studied, aromatic substi-
tuted alkenes bearing electron-donating groups on the
Table 1. H2O2/HBr catalyzed aziridination of olefins with Chlor-
amine-T11
Entry Olefin
Reaction time (h) Yielda (%)
1
Styrene
5.0
3.5
4.0
2.5
6.5
5.0
5.5
75
86
80
92
72
75
55
45
60
67
2
4-Methylstyrene
3-Methylstyrene
a-Methylstyrene
Methyl methacrylate
Cyclohexene
3
4
5
6
7
Vinylcyclohexane
8
trans-Methyl cinnamate 10.0
9
10
4-Chlorostyrene
Cycloheptene
8.0
5.0
Keywords: Aziridination; Olefins; H2O2; HBr; Nitrene.
*
Corresponding author. Tel.: +91 135 2660071; fax: +91 135
2660098; e-mail addresses: birsain@iip.res.in; birsain@hotmail.com
a Isolated yields.
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.09.155

8732
S. L. Jain et al. / Tetrahedron Letters 45 (2004) 8731–8732
3
R
R1
R2
R1
R2
R3
H2O2/HBr (20 mol%), Chloramine-T
CH3CN, MgSO4, N2
4
R4
R
N
Ts
Scheme 1.
Vol. 42, Part 1, pp 1–214; (b) Padwa, A.; Woolhouse, A.
D. Aziridines and Fused Ring Derivatives. In Comprehen-
sive Heterocyclic Chemistry; Lwowski, W., Ed.; Pergamon:
Oxford, 1984; Vol. 7, pp 47–93.
H2O2
HBr
+
HOBr
C
C
1
2. (a) Padwa, A.; Woolhouse, A. D. In Comprehensive
Heterocyclic Chemistry: The Structure, Reactions, Synthe-
sis and Uses of Heterocyclic Compounds; Katritzky, A. R.,
Rees, C. W., Eds.; Pergamon Press: Oxford, 1984; Vol. 7,
p 47; (b) Kemp, J. E. In Comprehensive Organic Synthesis;
Trost, B. M., Fleming, I., Eds.; Pergamon: Oxford, 1991;
Vol. 7, p 469.
+
Br
C
C
Br
2
3. Yamada, Y.; Yamamoto, T.; Okawara, M. Chem. Lett.
1975, 361–362.
Cl
Ts
-
Br
Cl
N
4. (a) Evans, D. A.; Faul, M. M.; Bilodeau, M. T. J. Org.
Chem. 1991, 56, 6744–6746; (b) Evans, D. A.; Faul, M.
M.; Bilodeau, M. T.; Anderson, B. A.; Barnes, D. M. J.
Am. Chem. Soc. 1993, 115, 5328–5329; (c) Li, Z.; Conser,
K. R.; Jacobsen, E. N. J. Am. Chem. Soc. 1993, 115, 5326–
5327; (d) Evans, D. A.; Faul, M. M.; Bilodeau, M. T. J.
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Br
C
-
-
OH
C
Br
C
C
N
N - Ts
4
Ts
Cl
3
C
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-
Br
+
5. Simkhovich, L.; Gross, Z. Tetrahedron Lett. 2001, 42,
8089–8092.
Ts
Scheme 2.
6. (a) Ando, T.; Minakata, S.; Ryu, I.; Komatsu, M.
Tetrahedron Lett. 1998, 39, 309–312; (b) Vyas, R.;
Chanda, B. M.; Bedekar, A. W. Tetrahedron Lett. 1998,
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11. Typical experimental procedure: To a stirred solution of
hydrogen peroxide (aq 30%, 0.023ml, 20mol%) in aceto-
nitrile (5ml) was added hydrobromic acid (48%, 0.033ml,
20mol%), 4-methylstyrene (118mg, 1mmol), Chloramine-
T trihydrate (337mg, 1.2mmol) and MgSO4 (100mg)
under a nitrogen atmosphere at 25°C. Stirring was
continued for 3.5h and the reaction progress was moni-
tored by TLC (SiO2) using ethyl acetate/hexane (4:6) as
eluent. After completion, the solvent was evaporated
under reduced pressure. The residue obtained was purified
through a short silica gel column using hexane/ethyl
acetate (4:1) as eluent. Evaporation of the solvent yielded
benzene ring were found to be more reactive. The pres-
ence of a water-trapping agent was found to be essential
for this reaction as in its absence, lower yields of aziri-
dines were obtained.
Although the mechanism of this reaction is not clear at
this stage, the reaction probably involves the formation
of hypobromous acid by the reaction of aq hydrogen per-
oxide with hydrobromic acid, which acts as a source of
bromonium ions. The bromonium ion reacts with olefin
1 to afford intermediate 2, which undergoes ring opening
by Ts(Cl)NÀ to give b-bromo-N-chloro-p-toluenesulfon-
amide 3. Attack of OHÀ on the N–Cl group of presumed
intermediate 3 generates the anion 4 subsequent cycliza-
tion of which yields the aziridine (Scheme 2).7
Acknowledgements
We thank the Director, IIP, for his kind permission to
publish these results. S.L.J. and V.B.S. thank CSIR,
New Delhi, for the award of Research Fellowships.
References and notes
N-(p-tolylsulfonyl)-2-(p-methylphenyl)aziridine
(yield
1. (a) Deyrup, J. A. In The Chemistry of Heterocyclic
Compounds; Hassner, A., Ed.; Wiley: New York, 1983;
247mg, 80%). Similarly, other aziridines were prepared
via this procedure.