N-bromosuccinimide/cerium ammonium nitrate: An efficient reagent for stereo-controlled deamination of ketoaziridines

Article abstract of DOI:10.3184/174751914X14176157994656

An efficient and novel method for the deamination of trans-1-alkyl (H or benzoyl)-2-aroyl aziridines in a completely stereo-controlled reaction in the presence of N-bromosuccinimide/cerium (IV) ammonium nitrate is described. In comparison with the previous reported work, this reaction reveals a substituent-reactivity relationship and important role for the substituent on C1 and C2 in determining whether deamination or oxidation reaction takes place.

Full text of DOI:10.3184/174751914X14176157994656

JOURNAL OF CHEMICAL RESEARCH 2014
VOL. 38 DECEMBER, 731–733
RESEARCH PAPER 731
N-bromosuccinimide/cerium ammonium nitrate: an efficient reagent for
stereo-controlled deamination of ketoaziridines
Heshmat Allah Samimi*, Elham Salehi and Farkhondeh Dadvar
Department of Chemistry, Faculty of Sciences, Shahrekord University, PO Box 115, Shahrekord, Iran
An efficient and novel method for the deamination of trans-1-alkyl (H or benzoyl)-2-aroyl aziridines in a completely stereo-
controlled reaction in the presence of N-bromosuccinimide/cerium (IV) ammonium nitrate is described. In comparison with the
previous reported work, this reaction reveals a substituent-reactivity relationship and important role for the substituent on C1
and C2 in determining whether deamination or oxidation reaction takes place.
Keywords: ketoaziridine, deamination, stereo-controlled, N-bromosuccinimide, cerium ammonium nitrate
Aziridines are an important class of saturated heterocycles which
Initially, a variety of N–H 2-benzoyl-3-aryl aziridines
(1a–f) was prepared via the Gabriel–Cromwell procedure
by bromination of the related α,β-unsaturated carbonyl
1,2
21
are often used as synthetic intermediates. The strained three-
membered ring of aziridine reacts with a variety of nucleophilic
or electrophilic reagents affording valuable products which are
compounds followed by the reaction of ammonia solution
3,4
15,21
important in synthetic or mechanistic studies.
(30%) in methanol at room temperature.
The aziridines
Aziridines have been classified as ‘activated’ or ‘non-
activated’accordingtowhetherornotnucleophilicring-opening
reactions proceed in the absence of a positive charge on the
nitrogen. The presence of electron-withdrawing substituents
activates the ring, which then reacts easily with nucleophiles
to form ring-opened products. Efforts, have been devoted to
the development of the reactions of activated’ aziridines with
different reagents over the past decade, leading to a variety of
were identified by comparison of their melting points and
2
2,23
spectroscopic data with those from the literature.
We examined the reaction of 1a with NBS in CH CN/H O
3
2
which afforded a chalcone by a the deamination reaction in
low yield. The reaction of aziridine with NBS/CAN (1:0.2)
in CH CN/H O (9:1) was also examined. This gave trans-
3
2
chalcone in excellent yield by the deamination reaction
(Scheme 1).
5,6
the products In contrast to activated aziridines, non-activated
In further investigations, the deamination reaction in the
presence of NBS/CAN (1:0.2) was then extended to a variety
of N–H 2-benzoyl-3-aryl aziridines (1a–f). The results are
summarised in Table 1. We observed the formation of the
trans-alkenes (2a–f) as exclusive products of the deamination
reaction (Scheme 2). The products were characterised by their
7,8
aziridines are relatively inert towards nucleophilic reagents.
Among the reactions of aziridines, the deamination of
aziridines has been attractive for mechanistic, structural,
thermodynamic and theoretical reasons. Several methods have
9
–11
been described for the deamination of a variety of aziridines.
We have explored different reactions of 2-aroyl-3-aryl
aziridines affording functionalised and other valuable
13
1
spectral data ( C NMR, H NMR, IR and melting point) and
in the case of known products by comparison of their melting
12–20
N-containing compounds.
In continuation of our research
24,25
points and spectroscopic data with reported values.
activities in the field of the reactions of aziridines, we have
found that N-bromosuccinimide (NBS)/cerium (IV) ammonium
nitrate (CAN) is a suitable reagent for deamination of N–H,
N-aryl and N-aroyl 2-benzoyl-3-phenyl aziridines. This study
shows that substituents on C1 and C2 aziridines have a more
important role in determining the reactions, deamination
or oxidation, with NBS/CAN rather than substituents on the
N-atom of the aziridine ring.
After successful application of this methodology to non-
activated aziridines, in order to investigate the scope of the
reaction, the reaction of trans-1,2-dibenzoyl-3-aryl aziridine
15
14
(
3a,b), and trans-1-benzyl-2-benzoyl-3-aryl aziridine (4a,b),
were subsequently examined under the same conditions
Scheme 3). These reactions afforded only trans-chalcone by
(
the deamination reaction.
Another striking feature of this reaction was that other
aziridines in the presence of NBS/CAN (1:1) in CH CN/H O
3
2
resulted in carbonyl compounds. Both aryl aziridines and
aliphatic aziridines in the presence of NBS/CAN have been
oxidised (Scheme 4). A related report uses β-cyclodextrins in
H
N
O
NBS/CAN
CH CN/H O
O
Ph
Ph
Ph
3
2
Ph
1
a
2a
Table 1 Deamination of trans-2-benzoyl-3-aryl aziridines (1) with NBS/CAN
Entry
Ar1
C6H5
4-NO C H
Time/h
Yield/%a,b
M.p./°C
55–57d
M.p./°C
56–58c
Scheme 1 Reaction of 2-benzoyl-3-phenyl aziridine with NBS/CAN.
1
1
a
b
1
1.5
1
1.5
1
1
91
86
94
88
81
89
165–166d 164–166c
2
6
4
210d
209–211c
108–111c
114–115c
113–115
H
1c
1d
1e
1f
2,4-Cl C H
2
6
3
4
N
O
111–112d
115–116d
113–115
NBS/CAN
2-NO C H
2
6
4
O
Ar1
Ph
Ar1
4-OMeC H
6
CH CN/H O
3
2
Ph
4-ClC H
1
a–f
2a–f
6
4
a
Isolated yield after purification.
Scheme 2 Transformation of trans-2-benzoyl-3-phenylaziridine (1) to the
corresponding trans-chalcone (2).
b
All the products were identified by spectroscopic (IR, H NMR, 13C NMR)
1
and elemental analyses.
Identified by comparison of their melting points and spectroscopic data
c
2
4,25
with those reported.
d
Literature experimental melting points.24,25
*
Correspondent. E-mail: samimi-h@sci.sku.ac.ir
JCR1402951_FINAL.indd 731
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732 JOURNAL OF CHEMICAL RESEARCH 2014
R
N
O
H
N
NBS/CAN
O
Ar
Ph
O
K Cr O
2 2 7
Ar
CH CN/H O
ArCHO
3
2
Ph
2
Ar
CH CN/reflux
3
Ph
R= PhCOCl, Ar=Ph (3a), 4-NO C H (3b)[15] 2a (83%) 2b(89%)
R= BzCl, Ar=Ph (4a), 4-NO C H (4b)[14]
2
6
4
1a,b
2
a (87%) 2b(81%)
2
6 4
Scheme 3 Transformation of N-alkyl, N-benzoyl 2-benzoyl-3-phenyl
aziridines to the corresponding trans-chalcone with NBS/CAN.
Scheme 5 The reaction of ketoaziridine with a strong oxidising agent.
addition to NBS to catalyse the same transformation. These
reaction conditions also work well for epoxides to provide the
corresponding α-hydroxy ketones.
removed the reaction mixture was diluted with water and extracted
with ether (3×10 mL). The crude product was purified by column
chromatography on silica gel using n-hexane/ethyl acetate as eluent,
provided the corresponding trans-chalcone 2 (81–94%) (Table 1).
2
6,27
A comparison of the reactions in Scheme 4 shows that the
substituents on C2 of the aziridines ring have a more important
role than substituents on the nitrogen atom of the aziridines
ring in determining the reactions, oxidation or deamination of
aziridine. By changing the substituents such as benzoyl, alkyl,
tosyl or H on the nitrogen atom of the ketoaziridines ring (A,
Scheme 4), the reaction afforded only trans-chalcone of the
deamination reaction. On the other hand, replacing of hydrogen
atom on C2 of the aziridine ring with tosyl on the nitrogen atom
of aziridine ring (B and C, Scheme 4) led to α-tosyl amino
carbonyl compounds of the oxidation reaction.
Deamination of N‑benzoyl and/or N-benzyl ketoaziridines (3a–b) and
(4a–b); general procedure
CAN (0.2 mmole) was added to a solution of acetonitrile: water (9:1)
(10 mL), NBS (1 mmol), N-benzoyl and/or N-benzyl 2-benzoyl-
3-phenyl aziridine (1 mmol) and the mixture was left stirring at
room temperature (Scheme 3). After completion of the reaction, the
solvent was removed the reaction mixture was diluted with water and
extracted with ether (3×10 mL). The crude product was purified by
column chromatography on silica gel using n-hexane/ethyl acetate
as eluent, to provide the corresponding trans-chalcone 2 (81–89%)
(Scheme 3).
In another attempt, to investigate the possibility of oxidation
reaction with this class of compounds, we examined the
reaction of 2-benzoyl-3-aryl aziridines in the presence of
some oxidising agents such MnO and KMnO in acetonitrile
(
E)-1,3-Diphenylprop-2-en-1-one (2a): Pale yellow solid; m.p.
5
6–58 °C; IR (KBr): 3042, 3021, 1682, 1593, 883, 774, 699, 682.
1
H NMR (400 MHz, CDCl ) (δ, ppm): 8.10–7.98 (m, 2H), 7.74 (d,
J=15.6 Hz, 1H), 7.65–7.35 (m, 9H). C NMR (100 MHz, CDCl ) (δ,
3
2
4
.
13
3
No reaction between 1a and MnO or KMnO occurs even
2
4
ppm): 190.5, 144.6, 138.2, 134.9, 132.8, 130.5, 128.9, 128.6, 128.5,
under refluxing conditions. The reaction of aziridine (1a,b)
128.4, 122.2.
with K Cr O was also examined at room temperature, which
2
2
7
(E)-3-(4-Nitrophenyl)-1-phenylprop-2-en-1-one (2b): Pale brown
afforded benzaldehyde in 67 and 74% yield (Scheme 5).
In conclusion, this work describes a novel method for the
deamination of trans-1-alkyl (H or benzoyl)-2-aroyl aziridines
in a completely stereo-controlled reaction in the presence of
NBS/CAN. In comparison with the previous work, this reaction
reveals a substituent-reactivity relationship and an important
role of the substituent on the C1 and C2 in determining whether
a deamination or a oxidation reaction occurs.
1
solid; m.p. 164–166 °C; IR (KBr): 3062, 1660, 1597, 1518. H NMR
(
400 MHz, CDCl ) (δ, ppm): 7.55–7.58 (t, J=7.62, 7.67 Hz, 2H),
3
7.64–7.67 (t, J=7.55 Hz, 1H), 7.66–7.69 (d, J=15.88 Hz, 1H), 7.82 (d,
J=8.7 Hz, 2H), 7.83–7.87 (d, J=15.88 Hz, 1H), 7.07 (d, J=7.69 Hz,
13
2H), 8.31 (d, J=8.59 Hz, 2H). C NMR (100 MHz, CDCl ) (δ, ppm):
3
189.4, 141.4, 141.2, 137.7, 133.3, 128.8, 128.7, 128.6, 125.7, 124.2.
(
E)-3-(2,4-Dichlorophenyl)-1-phenylprop-2-en-1-one (2c): Yellow
1
solid; m.p. 209–211 °C; IR (KBr): 3037, 1658, 1596. H NMR
(
400 MHz, CDCl ) (δ, ppm): 8.50 (s, 1H), 8.14 (dd, J=7.6, 1.98 Hz,
3
Experimental
1H), 8.03 (d, J=8.3 Hz, 1H), 7.80 (d, J=15.82 Hz, 1H), 7.66 (d,
13
J=15.82 Hz, 1H), 7.61–7.70 (m, 5H). C NMR (100 MHz, CDCl ) (δ,
All yields refer to isolated products after purification by column
chromatography or distillation in vacuum. Products were
3
ppm): 189.8, 138.1, 136.7, 134.8, 133.2, 128.1, 123.3.
(E)-3-(2-nitrophenyl)-1-phenylprop-2-en-1-one (2d): Off yellow
1
13
characterised by IR, H NMR and C NMR spectra, TLC, melting
points. NMR spectra were recorded on a Bruker AMX-400
solid; m.p. 108–111 °C; IR (KBr): 3049, 1661, 1605, 1580, 1524, 858,
1
1
13
780, 743, 682, 666. H NMR (400 MHz, CDCl
3
) (δ, ppm): 8.49 (s,
spectrometer ( H at 400 MHz and C at 100 MHz) in CDCl with
3
1
H), 8.26–8.28 (dt, J=2.1, 8.1 Hz, 1H)., 8.0 (q, J=1.4, 7.2 Hz, 2H),
.9 (d, J=7.7 Hz, 1H), 7.80–7.86 (d, J=15.6 Hz, 1H), 7.65–7.67 (d,
J=15.6 Hz, 1H), 7.62–7.63 (m, 2H), 7.52–7.56 (q, J=0.6, 7.5 Hz, 2H).
chemical shift values in ppm downfield from TMS and IR spectra
were recorded on
All solvents used were dried and distilled according to standard
procedures.
7
a FTIR spectroscope JASCO, FT/IR-6300.
13
C NMR (100 MHz, CDCl ) (δ, ppm): 189.6, 148.7, 141.5, 137.5, 136.6,
3
134.3, 133.3, 130.0, 128.8, 128.6, 124.6, 124.5, 122.4.
Deamination of ketoaziridines (1a–f); general procedure
CAN (0.2 mmol) was added into a solution of acetonitrile: water
(E)-3-(4-Methoxyphenyl)-1-phenylprop-2-en-1-one (2e): Pale
yellow solid; m.p. 114–115 °C; IR (KBr): 3056, 2935, 1658, 1596, 1268.
1
(
(
(
9:1) (10 mL), NBS (1 mmol), N–H 2-benzoyl-3-phenyl aziridine
1a–f) (1 mmol) and the mixture was left stirring at room temperature
Scheme 2). After completion of the reaction, the solvent was
H NMR (400 MHz, CDCl ) (δ, ppm): 8.03 (dd, J=8.4 Hz, J=1.9,
3
2H), 7.80 (d, J=15.8 Hz, 1H), 7.63 (d, J=8.6 Hz, 2H), 7.53–7.46 (m,
3H), 7.43 (d, J=15.6 Hz, 1H), 6.91 (d, J=8.6 Hz, 2H), 3.83 (s, 3H).
R =PhCO
1
O
R =H, Bz, PhCO
2
This work
Ph
Ph
Ph
R2
2
N
NBS/CAN
CH CN/H O
R =H
O
1
Ph
R1
3
2
Previous work26-27
R =Ts
2
NHTs
Scheme 4 The substituent effect on the deamination or oxidation reaction of aziridines with NBS/CAN.
JCR1402951_FINAL.indd 732
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JOURNAL OF CHEMICAL RESEARCH 2014 733
1
3
C NMR (100 MHz, CDCl ) (δ, ppm): 190.6, 161. 6, 144.9, 138.4,
4
5
6
7
8
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32.4, 130.6, 130.3, 128.5, 128.4, 127.8, 119.7.
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1
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3
J=15.7 Hz, 1H), 7.58 (m, 2H), 7.55 (dd, J=7.7, 1.9 Hz, 1H), 7.50 (m,
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1
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1
0
11
Oxidation of ketoaziridines (1a–b); general procedure
K Cr O (0.5 mmole) was added to a solution of acetonitrile: water
12
H.A. Samimi, Z. Shams and A.R. Momeni, J. Iran. Chem. Soc., 2012, 9,
2
2
7
705.
(4:1) (10 mL), and N–H 2-benzoyl-3-phenyl aziridine (1 mmole)
13
H.A. Samimi and S. Mohammadi, J. Iran. Chem. Soc.,2014, 11, 69.
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and the mixture was refluxed. After completion of the reaction, the
solvent was removed and the reaction mixture was diluted with water
and extracted with ether (3×10 mL). The crude product was purified
by column chromatography on silica gel using n-hexane/ethyl acetate
as eluent to provide the corresponding benzaldehyde (Scheme 5)
1
4
15 H.A. Samimi, M. Mamaghani and Kh. Tabatabeian, J. Heterocyclic
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(67–74%).
1
8
19
We are thankful to Research Council of Shahrekord University
for supporting this work.
2
0
H.A. Samimi and B.M. Yamin, J. Chem. Res., 2014, 38, 358.
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Received 20 October 2014; accepted 7 November 2014
Paper 1402951 doi: 10.3184/174751914X14176157994656
Published online: 19 December 2014
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