An efficient method to synthesize TNAD by the nitration of 1,4,5,8-tetraazabicyclo-[4,4,0]-decane with N2O5 and acidic ionic liquids

Article abstract of DOI:10.1016/j.cclet.2013.12.015

An experimental study was carried out on the direct nitration of 1,4,5,8-tetraaza-bicyclo-[4,4,0]-decane to synthesize 1,4,5,8-tetranitro-1,4,5, 8-tetraazabicyclo-[4,4,0]-decane (TNAD) with N₂O₅ catalyzed by acidic ionic liquids. Var

Full text of DOI:10.1016/j.cclet.2013.12.015

Chinese Chemical Letters 25 (2014) 423–426
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
Original article
An efficient method to synthesize TNAD by the nitration of 1,4,5,8-
tetraazabicyclo-[4,4,0]-decane with N O and acidic ionic liquids
2
5
Xiao-Feng Cao, Bin-Dong Li *, Min Wang
Chemical Engineering College, Nanjing University of Science and Technology, Nanjing 210094, China
A R T I C L E I N F O
A B S T R A C T
Article history:
An experimental study was carried out on the direct nitration of 1,4,5,8-tetraaza-bicyclo-[4,4,0]-decane
Received 12 August 2013
to synthesize 1,4,5,8-tetranitro-1,4,5,8-tetraazabicyclo-[4,4,0]-decane (TNAD) with N
acidic ionic liquids. Various ionic liquids, such as [HMim]X, [(CH SO HMim]X and [Capl]X (X = pTSO ,
), and various parameters such as equivalents of ionic liquid, molar ratio of N to the
starting material, reaction time and temperature, and solvent were investigated. Ionic liquid
2 5
O catalyzed by
Received in revised form 9 December 2013
Accepted 10 December 2013
Available online 24 December 2013
À
À
2
)
4
3
À
À
NO
3
, HSO
4
2 5
O
[
(CH
(CH
2
)
)
4
4
SO
SO
3
3
HMim]HSO
HMim]HSO
4
4
showed better catalytic activity. In the presence of 3% molar ratio of
ionic liquid to the staring material, the yield of 1,4,5,8-tetranitro-1,4,5,8-
Keywords:
[
2
1
,4,5,8-Tetraazabicyclo-[4,4,0]-decane
tetraazabicyclo-[4,4,0]-decane was improved by 6.2% compared to the system without ionic liquid.
2 5
N O
ß 2013 Bin-Dong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Inert solvent
Acidic ionic liquids
TNAD
1
. Introduction
generates HCl. The yield of the second step is low and all nitrolyses
employ HNO
the presence of HNO
3
or H
2
SO
4
as solvent. The yields can be improved in
–Ac O, but this reaction requires a large
Cyclic nitramines constitute an important class of highly
3
2
energetic materials whose synthesis and properties have been
extensively studied. 1,4,5,8-Tetranitro-1,4,5,8-tetraazabicyclo-
excess of nitric acid and acetic anhydride in more than 2 h, which
adds considerable expense. Also the high reaction temperature
makes the reaction dangerous. In short, these methods inevitably
showed some weaknesses such as poor yield, environmental
pollution, low reaction rate, and inconvenient waste disposal.
In recent years, various cleaner nitration approaches have been
[
4,4,0]-decane was first synthesized by Willer [1] and it is an
energetic compound used as a main ingredient in composite
explosives and propellants. TNAD can yield a lower pressure
exponent than that of RDX and HMX, the rate of change in space of
the temperature gradient is negligible for these propellants and the
rate of mass diffusion is believed to be smaller compared with the
rate of mass convection [2,3]. The compatibility of TNAD with
other energetic components and inert materials is one of the most
stringent aspects of TNAD [4]. In practical applications, it is
responsible for releasing the reactivity in these compounds when
detonated [5].
explored. N
studied for several years. Millar et al. [9] introduced N
inert solvent into the synthesis of nitramines and nitrate esters.
Talawer et al. [10] succeeded in finding several N –inert solvents
as green and mild systems. Zhi et al. [11] reported that PEG200-
DAIL with N could increase the yield of HMX significantly.
2
O
5
employed as a green nitrating reagent had been
2 5
O
in an
2 5
O
2 5
O
Cheng et al. [12] improved the yield of RDX by 10.5% using ionic
liquid as a catalyst.
The synthesis of TNAD using conventional reagents involved
the nitrolysis of 1,4,5,8-tetranitroso-1,4,5,8-tetraazabicyclo-
The past few years have witnessed a growing interest in ionic
liquids (ILs) as solvent and catalyst for certain organic reactions. In
the presence of ionic liquids, the conversions of the nitration of
aromatic compounds have a significant improvement [13–17].
Here we combined the advantage of acidic ionic liquid with
[
4,4,0]-decane [1,6,7] and the nitration of 1,4,5,8 -tetraazabicy-
clo-[4,4,0]-decane with HNO /Ac O as the nitrating reagents [8].
3
2
However, the yields of nitrolysis reactions are below 60% and the
sequence involves more than two steps. The yield of the first step of
the nitrolysis is very high, but the disposal is difficult because it
2 5
N O -inert solvents. We attempted nitration of 1,4,5,8-tetrazabi-
cyclo-[4,4,0]-decane using the green nitrating agent, dinitration
pentoxide, in the presence of acidic ionic liquids. In this reaction,
the temperature is lower, there is no acidic waste and the solvent
can be used repeatedly. The results are presented in this letter.
*
Corresponding author.
E-mail address: libindong@mail.njust.edu.cn (B.-D. Li).
1
001-8417/$ – see front matter ß 2013 Bin-Dong Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2013.12.015

4
24
X.-F. Cao et al. / Chinese Chemical Letters 25 (2014) 423–426
2
. Experimental
8
0
5
All chemicals were purchased from commercial sources and
7
used for the reaction without further purification. The melting
points were obtained with a WRS-1B Digital Melting Apparatus.
The IR spectra were recorded on a Nexus 870FT-IR spectrometer
70
65
À1
1
and expressed in cm
. H NMR was recorded on a Bruker DRX
5
00 MHz spectrometer.
6
5
5
4
0
5
0
5
2 5
2.1. Preparation of N O [18]
P
2
O
5
was added slowly to a distillation flask containing freshly
distilled nitric acid (100%) and reaction temperature should be
kept below 10 8C. Slow distillation affords N with the liberation
of nitrogen oxides. The collected N was a white/yellow solid.
The product was warmed slowly to 10 8C so that any liquid
nitrogen oxides were discarded. It is important that the N used
is free of nitrogen oxides. Caution: N is highly corrosive and
2 5
O
2
O
5
30
40
50
60
70
Time/min
2 5
O
Fig. 1. The effect of reaction time on the nitration. Reaction conditions: n(1,4,5,8-
2 5
O
tetraazabicyclo-[4,4,0]-decane)/n(N
5 8C.
2
O
5
) = 1:6,
2
N O
5
/CH
2
Cl
2
(30 mmol/30 mL),
liberates toxic nitrogen oxide. Small amounts can be quickly
neutralized with copious amount of water.
2
1
3
TMS):
d
6.5 (s, 2H), 4.4 (m, 4H), 2.5 (m, 4H). C NMR (125 MHz,
2.2. Preparation of acidic ionic liquids
DMSO, TMS):
d
46.9, 69.9.
À
À
3À
4À
[
HMim]X (X = pTSO , NO , HSO ) were synthesized accord-
ing to the procedures reported by Lu et al. [12].
1
3. Results and discussion
[
HMim]pTSO: H NMR (500 MHz, D
2
O, TMS): d 2.21 (s, 3H), 3.69
(
[
2
s, 3H), 7.17 (d, 2H), 7.20 (d, 2H), 7.54 (s, 2H), 8.31 (s, 1H).
1
In our initial study, the nitration of 1,4,5,8-tetraazabicyclo-
HMim]NO
H), 8.70 (s, 1H). [HMim]HSO
3
: H NMR (500 MHz, D
2
1
O, TMS):
d
3.80 (s, 3H), 7.46 (s,
H NMR (500 MHz, D O, TMS):
3.69 (s, 3H), 7.21 (s, 2H), 8.43 (s, 1H).
2 5
[4,4,0]-decane (prepared according to [8]) using N O in inert
4
:
2
solvent in the range of reaction temperatures, reaction times,
molar ratios and solvents were examined.
d
À À 3À 4À
[
(CH
2
)
4
SO
3
HMim]X (X = pTSO , NO , HSO ) were synthe-
It can be seen from Fig. 1 that the yield of TNAD increased and
the reaction rate decreased gradually with time. Most of the
reaction was occurred in 50 min. The yield was 77.6% and did not
change after 60 min.
Subsequently the effect of reaction temperature on nitration
was explored and the results are shown in Table 1. When the
reaction temperature was 0 8C, only 15.8% yield was obtained in
60 min and the yield increased as the reaction temperature
increased from 0 8C to 25 8C. Continuing to rise the reaction
temperature had an adverse effect on the yield. The reason may be
sized according to the procedures reported by Qi et al. [19].
1
[
(CH
m, 2H), 1.51 (t, 2H), 2.11 (s, 3H), 2.69 (t, 2H), 3.60 (s, 3H), 7.08 (d,
H), 7.18 (d, 2H), 7.42 (d, 2H), 8.40 (s, 1H). [(CH SO HMim]pTSO:
2
)
4
SO
3 4 2
HMim]HSO : H NMR (500 MHz, D O, TMS): d 1.46
(
1
1
2
)
4
3
H NMR (500 MHz, D
2
O, TMS):
d
2.03 (s, 3H) 2.13 (m, 2H), 2.76
(t, 2H), 3.75 (s, 3H), 4.12 (t, 2H) 7.15 (d, 2H), 7.21 (d, 2H) 7.38 (s,
2
H), 8.34 (s, 1H).
À
À
3À
4À
[
Capl]X (X = pTSO , NO , HSO ) were synthesized according
to the procedures reported by Cheng et al. [20].
1
[
Capl]pTSO: H NMR (500 MHz, D
2
O, TMS): d 1.61–1.77 (m, 6H),
higher temperature made the N decomposed more rapidly.
2
O
5
2
.41 (s, 3H), 2.49 (t, 2H), 3.26 (t, 2H), 7.38 (d, 2H), 7.71 (d, 2H).
1
The effect of molar ratio of N O to 1,4,5,8-tetraazabicyclo-
2 5
[
Capl]NO
3
:
H NMR (500 MHz, D
.34 (t, 2H), 3.10 (t, 2H). [Capl]HSO
1.37–1.57 (m, 6H), 2.16 (t, 2H), 3.02 (t, 2H).
2
O, TMS):
d
1.41–1.61 (m, 6H),
1
[4,4,0]-decane was investigated and the results are summarized in
Table 2. It was observed that the yields were improved
2
4
:
H NMR (500 MHz, D O,
2
TMS):
d
2 5
significantly as the amount of N O increased. The reason was
+
that N
agent that can improve the yield of TNAD. However, excessive
resulted in lower yield. That may be because of that fact that
2 5 2
O could produce more NO , which was a good nitrating
2.3. Preparation of 1,4,5,8-tetraazabicyclo-[4,4,0]-decane [8]
2 5
N O
This compound was obtained as a white powder, mp 205–
À1
2 5
higher concentration N O cleaved the cyclic structure of the
2
2
8
07.6 8C [lit. [8]: 210–230 8C]. IR (KBr, cm ):
n
3160(s), 2940(s),
product.
890(s), 2800(s), 1490(m), 1340(m), 1310(w), 1150(s), 950(s),
60(s).
Table 3 shows the results of the nitration of 1,4,5,8-tetra-
zabicyclo-[4,4,0]-decane using N in various inert solvents.
2 5
O
It was observed that the yields were improved significantly in
more polar solvents. The reason was that polar solvent could
2
.4. General procedure for the synthesis of TNAD catalyzed by acidic
ionic liquids
To a cold (0 8C) vigorously stirred solution of N
2
O
5
(30 mmol)
Table 1
a
and CH Cl (30 mL), an indicated amount of ionic liquid was added.
2
2
Effect of reaction temperature on the nitration.
A given amount of 1,4,5,8-tetraazabicyclo-[4,4,0]-decane was
added in portions to keep the temperature below 5 8C. The
reaction was carried out at 25 8C for 60 min, and then the mixture
was cooled to 20 8C and poured into 50 g of ice water. The solid
product was collected by filtration and rinsed with water, the pure
No.
T (8C)
Yield (%)
Purity (%)
1
2
3
4
5
0
15
25
35
45
15.8
46.9
77.6
73.4
70.5
99.7
99.2
99.4
99.5
99.4
product was obtained after recrystallization from DMSO and dried
À1
in vacuum. Mp 231.5–232.3 8C; IR (KBr, cm ):
2
n
3040(w),
a
Reaction conditions: n(1,4,5,8-tetraazabicyclo-[4,4,0]-decane)/n(N
/CH Cl (30 mmol/30 mL), 60 min.
2 5
O ) = 1:6,
1
960(w), 1550(s), 1280(s), 1060(m); H NMR (500 MHz, DMSO,
N
2
O
5
2
2

X.-F. Cao et al. / Chinese Chemical Letters 25 (2014) 423–426
425
Table 2
Table 4
a
a
Effect of molar ratio on the nitration.
Nitration of 1,4,5,8-tetraazabicyclo-[4,4,0]-decane in various ILs.
b
No. n(N
2
O
5
):n(1,4,5,8-tetraazabicyclo-[4,4,0]-decane) Yield (%) Purity (%)
No.
IL
Yield (%)
Purity (%)
1
2
3
4
5
4:1
5:1
6:1
7:1
8:1
37.3
62.1
77.6
69.3
67.6
99.3
99.5
99.8
99.4
99.4
1
2
3
4
5
6
7
8
9
[HMim]HSO
[HMim]NO
[HMim]pTSO
4
89.1
88.4
87.3
89.4
88.8
87.9
88.3
87.6
86.2
99.4
99.6
99.2
99.3
99.3
99.5
99.4
99.8
99.5
3
[(CH
[(CH
[(CH
)
2 4
)
2 4
)
2 4
SO
3
SO
3
SO
3
HMim]HSO
HMim]NO
HMim]pTSO
4
3
a
Reaction conditions: N
2
O
5
/CH
2
Cl
2
(30 mmol/30 mL), 60 min, 25 8C.
[Capl]HSO
[Capl]NO
[Capl]pTSO
4
3
Table 3
Effect of solvent on the nitration.
a
Reaction conditions: n(1,4,5,8-tetraazabicyclo-[4,4,0]-decane)/n(N
/CH NO (30 mmol/30 mL).
The catalyst amount is 3% molar ratio to 1,4,5,8-tetrazabicyclo-[4,4,0]-decane.
2 5
O ) = 1:6,
a
6
0 min, 25 8C, N
2
O
5
3
2
b
No.
Solvent
Yield (%)
Purity (%)
1
2
3
4
CH
CHCl
CH Cl
CCl
3
NO
2
3
2
4
83.2
79.5
77.6
71.4
99.5
99.6
99.2
99.8
NO2
N
NO2
N
2
H
N
H
N
NO2+
N O
2
5
a
2 5
Reaction conditions: n(1,4,5,8-tetraazabicyclo-[4,4,0]-decane)/n(N O ) = 1:6,
3
2
0 mmol N O
5
, solvent 30 mL, 25 8C, 60 min.
ILs
N
H
N
H
N
N
+
promote the production of NO
2
from N
2
NO .
2
O
5
. The yield of TNAD
NO2
NO2
reached 83.2% in the presence of CH
3
Numerous papers have reported that strong acidic catalysts
Scheme 1. Possible mechanism for electrophilic nitration.
could promote the formation of electrophilic nitronium ions
+
(NO
2
) from N
2
O
5
[21,22]. The effect of the amount of ionic liquid
on the nitration of 1,4,5,8-tetrazabicyclo-[4,4,0]-decane was
investigated using [(CH SO HMim]HSO in the range of 1%–5%
4. Conclusion
2
)
4
3
4
mol ratio to 1,4,5,8-tetrazabicyclo-[4,4,0]-decane, and the results
are shown in Fig. 2. It was observed that the yield could be
In conclusion, a new efficient process to synthesize TNAD from
1,4,5,8-tetraazabicyclo-[4,4,0]-decane in 89.4% yield was success-
increased to 89.4%, however, further increasing the [(CH
2
)
4
SO
3
H-
fully developed using N
2
O
5
2 4 3 4 3 2
and [(CH ) SO HMim]HSO in CH NO .
Mim]HSO loading would decrease the yield. The reason may be
4
The combination of IL and N O
2 5
seems to be a useful nitrating
that an appropriate acidity was necessary for the nitration
reaction. It is important to emphasize that ILs must be used dry
to provide the yield achieved.
system. However, the nitration of other nitrogen heterocyclic
compounds using this mild reaction system should be further
studied.
Then the reaction was compared in several IL systems. Based on
the data in Table 4, the conclusion could be drawn that all ILs have
catalytic activity in the nitration. Compared to the system without
ILs, the yield of TNAD increased by 3.0%–6.2% under the mild
Acknowledgment
We are grateful for the financial support from the Nature
Science Foundation of Jiangsu Province (No. BK2011697).
2 4 3
conditions indicated in Table 4. The IL [(CH ) SO HMim]X showed
better catalytic activity than other ILs. This might be related to the
acidity of the cations (Scheme 1).
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