Sensitivities of some imidazole-1-sulfonyl azide salts

Article abstract of DOI:10.1021/jo202264r

Imidazole-1-sulfonyl azide hydrochloride, an inexpensive and effective diazotransfer reagent, was recently found to be impact sensitive. To identify safer-to-handle forms of this reagent, several different salts of imidazole-1-sulfonyl azide were prepared, and their sensitivity to heat, impact, friction, and electrostatic discharge was quantitatively determined. A number of these salts exhibited improved properties and can be considered safer than the aforementioned hydrochloride. The solid-state structures of the chloride and less sensitive hydrogen sulfate were determined by single-crystal X-ray diffraction in an effort to provide some insight into the different properties of the materials.

Full text of DOI:10.1021/jo202264r

Article
pubs.acs.org/joc
Sensitivities of Some Imidazole-1-sulfonyl Azide Salts
Niko Fischer,† Ethan D. Goddard-Borger,‡ Robert Greiner,† Thomas M. Klapotke,*,† Brian W. Skelton,§
̈
and Jorg Stierstorfer†
̈
†Energetic Materials Research, Department of Chemistry, University of Munich (LMU), Butenandtstrasse 5-13, D-81377, Germany
‡Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
§School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia
S
* Supporting Information
ABSTRACT: Imidazole-1-sulfonyl azide hydrochloride, an in-
expensive and effective diazotransfer reagent, was recently found
to be impact sensitive. To identify safer-to-handle forms of this
reagent, several different salts of imidazole-1-sulfonyl azide were
prepared, and their sensitivity to heat, impact, friction, and
electrostatic discharge was quantitatively determined. A number
of these salts exhibited improved properties and can be con-
sidered safer than the aforementioned hydrochloride. The solid-
state structures of the chloride and less sensitive hydrogen
sulfate were determined by single-crystal X-ray diffraction in an effort to provide some insight into the different properties of the
materials.
INTRODUCTION
RESULTS AND DISCUSSION
■
■
In recent times, organic azides have attracted considerable atten-
tion because of the facile reactions that these high energy,
kinetically stable molecules undergo.1 Their use in dipolar
cycloadditions, investigated in detail by Huisgen and co-
workers in the 1960s2 and popularized in the past decade by
the revelation that such reactions are catalyzed by various
metals,3 is particularly noteworthy. As a consequence of this
popularity, there is a considerable interest in synthetic method-
ologies for the preparation of organic azides. The diazo-transfer
reaction is one such method and involves the conversion of a
primary amine into an organic azide by the action of a powerful
diazo donor (most commonly a sulfonyl azide). For the
reaction to proceed in a facile manner, the sulfonyl azide must
be adjoined to a strong electron-withdrawing group; trifluoro-
methanesulfonyl azide is most commonly used because
arylsulfonyl azides are, for the most part, simply not reactive
enough. To circumvent the problems of high cost and insta-
bility associated with using trifluoromethanesulfonyl azide,
imidazole-1-sulfonyl azide hydrochloride 1·HCl was developed
as an inexpensive and shelf-stable alternative diazo-transfer
reagent with comparable efficacy.4 The shock sensitivity and
thermal stability of activated, low-molecular weight azides has
always been cause for concern,1,5,6 and after hearing of an
explosion that occurred during the synthesis of 1·HCl4 we
sought to quantify the sensitivity of 1 and a number of its salts
toward impact, friction, and electrostatic discharge to provide
a rational assessment of the relative safety of these compounds.
It was anticipated that the sensitivity of reagent 1 to various
stimuli could be “tuned”, for better or worse, by crystallization
with different acids.
Imidazole-1-sulfonyl azide 1 is easily prepared by the addition
of 2 molar equiv of imidazole to chlorosulfonyl azide preformed
in situ by the reaction of equimolar quantities of sodium azide
and sulfuryl chloride in acetonitrile (Scheme 1).4 This product
Scheme 1. Synthesis of Different Salts of 1
can be precipitated from the crude solution as the pure hydro-
chloride salt 1·HCl by treatment with ethanolic hydrogen
chloride. Partitioning 1·HCl between an organic solvent and
aqueous sodium bicarbonate proved to be a convenient method
for obtaining organic solutions of pure 1. Solutions of 1 in ethyl
acetate were treated with sulphuric acid, toluenesulfonic acid,
perchloric acid, or tetrafluoroboric acid to precipitate the cor-
responding salts 1·H2SO4, 1·TsOH, 1·HClO4, and 1·HBF4, re-
spectively. Similarly, treatment of a solution of 1 in diethyl
ether with methanesulfonic acid provided the corresponding
salt 1·MsOH.
The ability of these salts to act as diazo donors was con-
firmed by the conversion of 4-aminobenzoic acid into
4-azidobenzoic acid under standard diazo-transfer reaction
conditions (Table 1).4 All of the reactions provided product in
Received: November 9, 2011
Published: January 23, 2012
© 2012 American Chemical Society
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some even higher. However, in practice, when drying samples,
using or storing the materials, it is advisible to use temperatures
less than 60 °C. This provides a particularly large margin for
error for the more thermostable salts like 1·HBF4 and
1·H2SO4.
Table 1. Different Anions Do Not Significantly Affect the
Efficacy of Reagent 1
The sensitivities of each substance to mechanical stimuli
were assessed. Impact sensitivity tests were carried out accord-
ing to STANAG 44897 modified instructions8 using a BAM
1·HCl 1·H2SO4 1·MsOH 1·TsOH 1·HClO4 1·HBF4
(Bundesanstalt fur Materialforschung) drophammer,9 while
yield (%)
63
63
61
70
57
64
̈
friction sensitivity tests were carried out according to STANAG
448710 modified instructions11 using the BAM friction tester.
The sensitivity of each compound toward electrical discharge
was also determined using the electric spark tester ESD 2010
EN.12 These data, together with decomposition temperatures
and nitrogen content (percentage by weight) of each material,
are presented in Table 2. When interpreting the data presented
comparable isolated yield, demonstrating that the different anions
do not significantly affect the efficacy of the reagent.
Differential scanning calorimetry (DSC) was performed on 1
and all of its salts to determine their melting points and decom-
position onset temperatures. The thermal behavior of these
materials is displayed as DSC plots in a temperature range
from 20 to 400 °C in Figure 1. Since none of the compounds
a
Table 2. Sensitivity Data for 1 and Its Salts
sensitivity
impact friction
ESD
(J)
percentage nitrogen dec temp
compd
(J)
(N)
(w/w, %)
(°C)
1
<1
6
72
240
240
192
>360
<5
40.5
33.4
25.8
26.0
20.3
25.6
26.8
112
102
131
88
1·HCl
0.50
0.30
0.10
0.70
0.15
0.50
1·H2SO4
1·MsOH
1·TsOH
1·HClO4
1·HBF4
40
40
30
<1
40
114
140
146
240
a
ESD is an acronym for electrostatic discharge. The technique used to
determine these values cannot be applied to 1 because it is a liquid
under standard conditions.
in Table 2, one should note that the larger a value is for a
given test, the less sensitive that material is to that given form
of stimulus. Further, subsequent descriptions of materials as
“insensitive”, “less sensitive”, “sensitive”, “very sensitive”, or
“extremely sensitive” are based on the UN Recommendations
on the Transport of Dangerous Goods.13
What is quite remarkable about the data in Table 2 is that
the properties of the materials vary significantly, ranging from
extremely sensitive to insensitive, even though they all contain
the same energetic species. The parent compound 1, as well as
the perchlorate 1·HClO4, is very sensitive toward impact, as one
would expect. The previously reported chloride 1·HCl and the
tosylate 1·TsOH are sensitive to impact and should be handled
with care. The hydrogen sulfate 1·H2SO4, mesylate 1·MsOH,
and tetrafluoroborate 1·HBF4 are insensitive to impact. A similar
trend is observed for the friction sensitivity of the compounds.
The parent sulfonyl azide 1 and its perchlorate salt 1·HClO4
are again of concern: classified as very sensitive and extremely
sensitive, respectively. The other salts have higher values and are
only considered sensitive to friction, except for the tosylate
1·TsOH, which is insensitive to friction. Values determined for
electrostatic discharge (ESD) are strongly dependent on the
grain size of the crystalline material, thus differing between
batches of each material and for technical reasons cannot be
determined for a liquid like 1. Nevertheless, all of the salts
returned values in the range of 0.10−0.70 J, indicating that
none were particularly sensitive toward electrostatic discharge.
From these results, several recommendations can be made.
The parent compound 1, as a neat liquid, should be handled
with extreme caution and ideally would never be isolated but
Figure 1. DSC plots of compound 1 and its various salts (exothermic = ↑,
endothermic = ↓).
crystallized as hydrates or with included solvent, as indicated by
elemental analyses, the small endothermic peaks of each DSC
curve can be assigned as the melting point for each salt, while
the exothermic peaks can be ascribed to decomposition. De-
composition temperatures for each compound are defined by
the lowest onset temperature of the exotherms.
Interestingly, the temperature at which decomposition
commences varies considerably; from the low value of 88 °C
for 1·MsOH, to the parent compound 1 at 112 °C, up to 146 °C,
as observed for 1·HBF4. The only salt with a relatively large
liquid range (>50 °C) was 1·HBF4, which melted at 92−94 °C
but did not begin to decompose until it reached a temperature
of 146 °C. From the DSC data, it is evident that all of the
materials can be used at a temperature less than 88 °C and
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instead prepared and used only in solution. As expected, the
perchlorate 1·HClO4 is even more hazardous than 1 and
should not be prepared by those without expertise in handling
energetic materials. The hydrochloride salt 1·HCl has com-
parable impact sensitivity (not to be confused with energetic
yield) to RDX (cyclotrimethylenetrinitramine), a commonly
used high explosive, and must be handled with caution. On the
other hand, the relatively high decomposition temperature,
impact insensitivity, low friction, and ESD sensitivities of the
hydrogensulfate 1·H2SO4 and the tetrafluoroborate 1·HBF4
make these two materials safe to manipulate, although all the
usual precautions taken when handling energetic laboratory
reagents should still be observed.
Another issue worthy of consideration, especially if these
reagents are to be kept in bulk, is the question of shelf stability.
If not stored with desiccation, the hygroscopic hydrochloride
1·HCl discolors and liquefies over the course of a few weeks,
producing a brown oil that smells of hydrazoic acid. The hydro-
gensulfate 1·H2SO4 is less hygroscopic, remaining unchanged
after storage for several months under ambient conditions.
However, after more than one year, this salt also discolored and
liquefied with the liberation of hydrazoic acid. Only the tetra-
fluoroborate 1·HBF4 remained unaffected by storage under
ambient conditions for one year. Thus, one can conclude that
1·HBF4 has the most favorable characteristics of all the salts
investigated but that 1·H2SO4 is a less expensive, viable alter-
native if stored with the exclusion of moisture.
The solid-state structures of 1·HCl and 1·H2SO4, two salts
with quite different sensitivities, were determined by single-
crystal X-ray diffraction to see if some insight might be gained
into why the former salt is more sensitive to mechanical stimuli
than the latter. The structures of both materials were solved
(see the Experimental Section for details) and found to crystallize
in the monoclinic space group P21/c with four molecules to each
unit cell. The molecular moiety of each solid is depicted in the
Supporting Information (Figure S1). The bond lengths and
angles associated with both imidazole moieties and counterions
are commensurate with literature values,14 while those associated
with the sulfonyl azide moiety did not differ significantly between
structures.
Figure 2. Comparison of the intermolecular interactions in crystals of
1·HCl and 1·H2SO4. (A) View on the hydrogen bonds in the structure
of 1·HCl. Symmetry codes: (i) x, 1.5 − y, 0.5 + z; (ii) −1 + x, y, z; (iii)
−x, 2 − y, 1 − z. (B) View on the hydrogen bonds in the structure of
1·H2SO4. Symmetry codes: (i) x, y, 1 + z; (ii) −1 + x, y, z; (iii) −1 + x,
0.5 − y, −0.5 + z; (iv) −1 + x, 0.5 − y, −0.5 + z; (v) x, y, −1 + z; (vi)
−x, −y, 2 − z.
CONCLUSION
■
Since all of the compounds investigated were equally good
diazo donors, the choice of ideal reagent comes down to a con-
sideration of their safety. All things considered, the tetrafluor-
oborate 1·HBF4 and the hydrogen sulfate 1·H2SO4 are the
safest-to-handle materials, although the tetrafluoroborate 1·HBF4
is superior in that it has a longer shelf life than the hydrogen
sulfate 1·H2SO4. However, the hydrogen sulfate 1·H2SO4 is
easier and less expensive to prepare than the tetrafluoroborate
1·HBF4 and can be stored with the exclusion of moisture to
prolong its shelf life, making it the recommended alternative to
the hydrochloride 1·HCl. None of these compounds were found
to be completely insensitive, which restricts options for trans-
portation and thereby commercialization. Formulation of one of
these salts with additives may provide a solution to this problem
and further extend shelf life.17
The main difference between these materials lies in their
molar volumes, density and the number of intermolecular
hydrogen bonding contacts made (Table 3, Figure 2). The more
Table 3. Molar Volume, Density, And Hydrogen Bonding in
1·HCl and 1·H2SO4
VM
classical H-bonds
per molecule
nonclassical H-
bonds per molecule
(cm3mol−1
)
ρ (g cm‑3)
1·HCl
1·H2SO4
122.4
144.8
1.713
1.873
1
2
3
4
sensitive salt, 1·HCl, has a smaller molar volume, lower den-
sity, and fewer hydrogen bonds than the less sensitive salt,
1·H2SO4. The greater molar volume of 1·H2SO4 leads to a
lower calculated lattice enthalpy (according to Jenkins’ equa-
tion15,16 ΔLH (1·H2SO4) = 484.5 kJ mol−1, ΔLH (1·HCl) =
506.4 kJ mol−1) but translates to fewer high energy azide groups
per unit volume in the solid. Its greater density and more
extensive network of hydrogen bonds may act as an energy sink
to suppress decomposition.
EXPERIMENTAL SECTION
■
Caution! Imidazole-1-sulfonyl azide and its salts are energetic materials
with sensitivities toward shock and friction. Therefore, proper safety
precautions (safety glass, face shield, earthened equipment and shoes,
Kevlar gloves, and ear plugs) should be employed while synthe-
sizing and handling the compounds described. Specifically, neat
imidazole-1-sulfonyl azide and its chloride and perchlorate salts are
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very sensitive and have to be handled with great care. Plastic suction
filters and spatulas are recommended for the isolation of the crystalline
materials described. Mother liquors and other waste, which may
contain the highly explosive sulfonyl diazide, should be treated with
excess sodium nitrite and acidified to destroy azide-containing species.
Imidazole-1-sulfonyl azide (1) as well as its hydrochloride (2) was
prepared according to literature procedures.4 Unfortunately, all de-
scribed compounds suffer from partial decomposition during the
NMR experiments in DMSO-d6, so that in all cases remaining unde-
composed material besides a decomposition product can be observed.
Presumably from the 3-azidosulfonyl-3H-imidazol-1-ium cation the
azidosulfonyl moiety is cleaved off resulting in the respective 1,3H-
imidazol-1-ium salts. Because of the polar character of the described
compounds and resulting solubility problems, it was not possible to
gain NMR data from different solvents such as CDCl3, CD3OD, or
acetone-d6. The NMR signals of the decomposition product can be
identified in all recorded spectra and are marked with an asterisk in the
experimental procedures.
3-Azidosulfonyl-3H-imidazol-1-ium 4-Toluenesulfonate
(1·TsOH). Imidazole-1-sulfonyl azide hydrochloride 1 (4.19 g, 20 mmol)
was suspended in EtOAc (50 mL). Under stirring, a saturated solution
of NaHCO3 (50 mL) was added. After 1 dissolved under gas evolution,
the phases were separated. The organic phase was dried over MgSO4
and subsequently treated with a solution of p-toluenesulfonic acid mono-
hydrate (3.8 g, 20 mmol) in EtOAc (35 mL). Then the reaction mixture
was cooled with an ice bath, and a small amount of hexane was added. The
precipitate was filtered off and washed with Et2O to give 3.29 g (9.53 mmol,
48%) of 1·TsOH as a white powder. DSC (5 °C min−1, °C): 111−114 °C
(mp); 114 °C (dec 1); 155 °C (dec 2). IR (KBr, cm−1): 3440 (br),
3157 (s), 3086 (s), 3058 (s), 2969 (m), 2554 (m), 2418 (m), 2305
(m), 2172 (vs), 1584 (m), 1495 (m), 1438 (vs), 1226 (vs), 1173 (vs),
1119 (vs), 1057 (s), 1011 (vs), 874 (m), 817 (m), 778 (vs), 682 (vs),
644 (vs), 566 (vs). Raman (1064 nm, 400 mW, 25 °C, cm−1): 3185
(12), 3158 (11), 3065 (100), 2984 (16), 2924 (53), 2872 (13), 2177
(58), 1601 (45), 1496 (18), 1450 (28), 1383 (22), 1318 (16), 1244
(10), 1213 (41), 1182 (20), 1123 (72), 1086 (27), 1060 (18), 1035
(27), 1014 (34), 982 (42), 803 (98), 777 (40), 685 (24), 651 (13),
637 (27), 605 (13), 584 (36), 483 (30), 466 (33), 402 (27), 363 (79),
318 (26), 293 (84), 232 (37). 1H NMR (DMSO-d6, 25 °C, ppm): δ =
14.28 (s, br, NH), 9.08* (t, CH, J = 1.2 Hz), 8.73 (dd, CH, J1 = 0.9 Hz,
J2 = 1.7 Hz), 8.00 (dd, CH, J1/2 = 1.1 Hz), 7.67* (d, CH, J = 1.4 Hz),
3-Azidosulfonyl-3H-imidazol-1-ium Hydrogen Sulfate
(1·H2SO4). Sulfuric acid (3.9 g, 39.85 mmol; in 20 mL EtOAc)
was added slowly to a solution of imidazole-1-sulfonyl azide 1 (6.9 g,
39.85 mmol; in 20 mL EtOAc) at 0 °C. The reaction mixture was
stirred for 1 h at rt. The precipitate was filtered, washed, and dried in
vacuo to give 9.3 g (29.52 mmol, 74%) of 1·H2SO4 as a white,
crystalline powder. DSC (5 °C min−1, °C): 105−108 °C (mp), 131 °C
(dec). IR (KBr, cm−1) 3110 (s), 3084 (s), 2969 (s), 2864 (s), 2177
(s), 1586 (m), 1516 (m), 1460 (w), 1431 (s), 1302 (m), 1233 (vs),
1191 (s), 1152 (vs), 1127 (vs), 1100 (vs), 1067 (s), 1018 (s), 983
(m), 872 (m), 834 (m), 774 (s), 740 (m); Raman (1064 nm, 400 mW,
25 °C, cm−1): 3187 (13), 3157 (23), 3113 (13), 2174 (100), 1588
(20), 1518 (23), 1462 (70), 1426 (26), 1329 (19), 1304 (44), 1236
(24), 1192 (35), 1146 (12), 1129 (18), 1103 (13), 1071 (48), 1021
(83), 984 (41), 899 (24), 780 (67), 646 (15), 617 (18), 599 (19), 585
(90), 486 (36), 467 (55), 430 (15), 411 (26), 372 (71), 362 (48), 322
−
7.51 (d, CH (p-TolSO3 , J = 8.0 Hz), 7.39 (dd, CH, J1 = 0.9 Hz, J2 =
−
1.7 Hz), 7.14 (d, CH, (p-TolSO3 , J = 8.0 Hz), 2.29 (s, CH3). 13C
NMR (DMSO-d6, 25 °C, ppm): δ = 145.4 (C1, p-TolSO3−), 138.8 (C4,
p-TolSO3−), 138.4, 134.9*, 130.5, 128.8 (C3/5, p-TolSO3−), 126.1(C2/6
,
p-TolSO3−), 119.9*, 119.5, 21.3 (CH3). m/z (FAB+): 174.2
+
−
[HImSO2N3 ]. m/z (FAB−): 171.1 [C7H7SO3 ]. Anal. Calcd for
C10H11N5O5S2: C, 34.78; H, 3.21; N, 20.28; S, 18.57. Found: C, 34.62;
H, 3.34; N, 20.14; S, 18.81. BAM drophammer: >30 J; friction tester:
>360 N; ESD: 0.7 J.
3-Azidosulfonyl-3H-imidazol-1-ium Perchlorate (1·HClO4).
Imidazole-1-sulfonyl azide (1) (13.8 g, 79.7 mmol) and perchloric
acid (60%, 5.2 mL, 79.7 mmol) were dissolved in 30 mL of EtOAc
each. Then the perchloric acid solution was slowly added to the
imidazole-1-sulfonyl azide solution at 0 °C. After the reaction mixture
was stirred for 1 h at rt, the white precipitate was filtered off and dried
in vacuo to give 3.9 g (14.25 mmol, 18%) of 1·HClO4 as a white
powder. DSC (5 °C min−1, °C): 115−117 °C (mp); 140 °C (dec). IR
(KBr, cm−1): 3168 (s), 2172 (s), 1581 (m), 1512 (m), 1446 (s), 1327
(m), 1284 (m), 1222 (m), 1197 (s), 1157 (s), 1121 (s), 1083 (vs),
1059 (vs), 981 (m), 888 (w), 779 (vs), 746 (m). Raman (1064 nm,
400 mW, 25 °C, cm−1): 3183 (9), 3170 (8), 2171 (47), 1580 (5),
1512 (8), 1444 (42), 1328 (14), 1286 (15), 1224 (23), 1196 (16),
1156 (7), 1134 (9), 1113 (17), 1078 (14), 983 (32), 938 (101), 930
(43), 910 (11), 788 (49), 627 (28), 590 (59), 485 (24), 462 (46), 365
1
(25), 203 (26). H NMR (DMSO-d6, 25 °C, ppm): δ = 14.30 (s, br,
−
NH+), 12.42 (s, br, HSO4 ), 9.06* (t, CH, J = 1.1 Hz), 8.69 (dd, CH,
J1 = 0.8 Hz, J2 = 1.5 Hz), 7.98 (dd, CH, J1/2 = 1.5 Hz), 7.66* (d, CH,
J = 1.2 Hz), 7.37 (dd, CH, J1 = 0.9 Hz, J2 = 1.7 Hz). 13C NMR
(DMSO-d6, 25 °C, ppm): δ = 138.3, 134.9*, 130.6, 119.8*, 119.5. m/z
+
−
(FAB+): 174.0 [HImSO2N3 ]. m/z (FAB−): 96.9 [HSO4 ]. Anal.
Calcd for C3H5N5O6S2: C, 13.28; H, 1.86; N, 25.82; S, 23.64. Found:
C, 13.61; H, 2.03; N, 26.11; S, 23.29. BAM drophammer: >40 J;
friction tester: >240 N; ESD: 0.3 J.
3-Azidosulfonyl-3H-imidazol-1-ium Methanesulfonate
(1·MsOH). Imidazole-1-sulfonyl azide 1 (8.66 g, 50 mmol) was diluted
with 10 mL of Et2O. Then methanesulfonic acid (4.81 g, 50 mmol)
was added dropwise under stirring at 0 °C. The precipitate was filtered
off, washed with EtOH and Et2O, and dried in vacuo, yielding 11.50 g
(42.7 mmol, 85%) of 1·MsOH as a white powder. DSC (5 °C min−1, °C):
75−78 °C (mp), 88 °C (dec). IR (KBr, cm−1): 3439 (br), 3107 (s),
3058 (s), 2908 (s), 2761 (s) 2704 (s), 2661 (s), 2577 (m), 2173
(vs), 1629 (w), 1580 (m), 1508 (m), 1449 (m), 1428 (vs), 1322 (m),
1195 (vs), 1161 (vs), 1135 (vs), 1103 (m), 1059 (vs), 981 (w), 834
(s), 780 (vs), 638 (s), 584 (s), 562 (s), 535 (m). Raman (1064 nm,
400 mW, 25 °C, cm−1): 3178 (17), 3120 (28), 3035 (49), 3020 (41),
2947 (100), 2179 (100), 1582 (10), 1514 (10), 1471 (66), 1444 (32),
1424 (21),1321 (25), 1302 (24), 1244 (11), 1189 (28), 1124 (12),
1058 (26), 1031 (59), 981 (30), 966 (12), 785 (96), 769 (25),
581 (60), 555 (22), 546 (21), 523 (12), 482 (22), 467 (28), 375 (29),
357 (36), 343 (24), 320 (11). 1H NMR (DMSO-d6, 25 °C, ppm): δ =
14.88 (s, br, MeSO3H), 14.28 (s, br, NH), 9.03* (t, CH, J = 1.2 Hz),
8.76 (dd, CH, J1 = 0.8 Hz, J2 = 1.6 Hz), 7.99 (dd, CH, J1/2 = 1.6 Hz),
7.63* (d, CH, J = 1.4 Hz), 7.39 (dd, CH, J1 = 0.8 Hz, J2 = 1.6 Hz),
2.46 (s, CH3SO3−). 13C NMR (DMSO-d6, 25 °C, ppm): δ = 138.4,
134.9*, 129.9, 119.8*, 119.6, 40.9 (CH3SO3−). m/z (FAB+): 174.1
1
(35), 359 (48), 330 (20), 210 (16). H NMR (DMSO-d6, 25 °C,
ppm): δ = 14.52 (s, br, HClO4), 14.27 (s, br, NH), 9.04* (CH), 8.76
(CH), 8.00 (CH), 7.66* (s, CH), 7.41 (CH). 13C NMR (DMSO-d6,
25 °C, ppm): δ = 138.4, 134.8*, 130.4, 119.8*, 119.6. m/z (FAB+):
+
−
174.0 [HImSO2N3 ]. m/z (FAB−): 98.9 [ClO4 ]. Anal. Calcd for
C3H4ClN5O6S: C, 13. 17; H, 1.47; N, 25.60; S, 11.72. Found: C,
13.11; H, 1.53; N, 25.55; S, 11.47. BAM drophammer: <1 J (!);
friction tester: <5 N (!); ESD: 0.15 J.
3-Azidosulfonyl-3H-imidazol-1-ium Tetrafluoroborate
(1·HBF4). At 0 °C, a solution of 54% fluoroboric acid in Et2O (3.25 g,
20 mmol) was slowly added to a solution of imidazole-1-sulfonyl azide
(1) in 25 mL of EtOAc (3.46 g, 20 mmol). A white precipitate in-
stantly formed. It was filtered off and washed with Et2O to give 3.20 g
(12.3 mmol, 61%) of 1·HBF4 as a white powder. DSC (5 °C min−1, °C):
92−94 °C (mp); 146 °C (dec). IR (KBr, cm−1): 3426 (s), 3168 (m), 3059
(m), 2167 (s), 1629 (w), 1580 (m), 1509 (w), 1438 (s), 1322 (w), 1294
(m), 1195 (vs), 1124 (vs), 1105 (vs), 1083 (vs), 1064 (vs), 1036 (vs), 834
(vw), 778 (s), 640 (s), 601 (m), 584 (m). Raman (1064 nm, 400 mW,
25 °C, cm−1): 3198 (15), 3173 (11), 3132 (10), 2166 (83), 1586 (11),
1446 (63), 1432 (29), 1324 (15), 1287 (14), 1230 (23), 1198 (20), 1143
(11), 1068 (16), 976 (31), 783 (64), 771 (51), 649 (21), 597 (102), 483
(34), 465 (42), 361 (71), 325 (30). 1H NMR (DMSO-d6, 25 °C, ppm):
δ = 14.21 (s, br, NH), 9.04* (t, CH, J = 1.2 Hz), 8.80 (dd, CH, J1 = 1.1 Hz,
+
[HImSO2N3 ]. m/z (FAB): 95.0 [MeSO3−]. Anal. Calcd for
C4H7N5O5S2: C, 17.84; H, 2.62; N, 26.01. Found: C, 17.46; H,
2.76; N, 25.88. BAM drophammer: >40 J; friction tester: >192 N;
ESD: >0.1 J.
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dx.doi.org/10.1021/jo202264r | J. Org. Chem. 2012, 77, 1760−1764

The Journal of Organic Chemistry
Article
J2 = 2.2 Hz), 8.02 (dd, CH, J1/2 = 1.3 Hz), 7.66* (d, CH, J = 1.5 Hz),
7.43 (dd, CH, J1 = 1.1 Hz, J2 = 2.1 Hz). 13C NMR (DMSO-d6, 25 °C,
ppm): δ = 138.4, 134.9*, 130.0, 119.8*, 119.6. m/z (FAB+): 174.1
[HImSO2N3+]. m/z (FAB−): 87.0 [BF4−]. Anal. Calcd for
C3H4BF4N5O2S: C, 13.81; H, 1.54; N, 26.84; S, 12.29. Found: C,
13.78; H, 1.77; N, 26.43; S, 12.59. BAM drophammer: >40 J; friction
tester: >240 N; ESD: 0.5 J.
(7) NATO standardization agreement (STANAG) on explosives,
impact sensitivity tests, no. 4489, 1st ed., Sep 17, 1999.
(8) WIWEB-Standardarbeitsanweisung 4-5.1.02, Ermittlung der
Explosionsgefahrlichkeit, hier der Schlagempfindlichkeit mit dem
̈
Fallhammer, Nov 8, 2002.
(9) http://www.bam.de, accessed February 7, 2012.
(10) NATO standardization agreement (STANAG) on explosive,
friction sensitivity tests, no. 4487, 1st ed., Aug 22, 2002.
(11) WIWEB-Standardarbeitsanweisung 4-5.1.03, Ermittlung der
ASSOCIATED CONTENT
* Supporting Information
Crystal structures (discussion, ORTEP figure of molecular unit,
■
Explosionsgefahrlichkeit oder der Reibeempfindlichkeit mit dem
̈
S
Reibeapparat, Nov 8, 2002.
(12) http://www.ozm.cz, accessed February 7, 2012.
(13) Impact: insensitive >40 J, less sensitive ≥35 J, sensitive ≥4 J,
very sensitive ≤3 J; friction: Insensitive >360 N, less sensitive = 360 N,
sensitive <360 N a. > 80 N, very sensitive ≤80 N, extreme sensitive
≤10 N. According to the UN Recommendations on the Transport of
Dangerous Goods (+) indicates: not safe for transport.
(14) Quick, A.; Williams, D. J. Can. J. Chem. 1976, 54, 2465−2469.
(15) Jenkins, H. D. B.; Roobottom, H. K.; Passmore, J.; Glasser, L.
Inorg. Chem. 1999, 38, 3609−3620.
and crystallographic data and parameters) of 1·HCl and
1
1·H2SO4. H and 13C NMR spectra of 1·H2SO4, 1·MsOH,
1·TsOH, 1·HClO4, and 1·HBF4. This material is available free
of charge via the Internet at http://pubs.acs.org/.
AUTHOR INFORMATION
Corresponding Author
*E-mail: tmk@cup.uni-muenchen.de.
■
(16) Jenkins, H. D. B.; Tudela, D.; Glasser, L. Inorg. Chem. 2002, 41,
2364−2367.
ACKNOWLEDGMENTS
(17) (a) Depernet, D.; Franco̧ is, B. WO 02/057210 A1, PCT/FR02/
■
00189, US 2002/0107416; Chem. Abstr. 2002, 137, 109123. (b) Ozanne,
A.; Pouysegu, L.; Depernet, D.; Francois, B.; Quideau, S. Org. Lett.
2003, 5 (16), 2903−2906.
Financial support of this work by the Ludwig-Maximilian
University of Munich (LMU), the U.S. Army Research
Laboratory (ARL), the Armament Research, Development and
Engineering Center (ARDEC), the Strategic Environmental
Research and Development Program (SERDP), and the Office
of Naval Research (ONR Global, title: “Synthesis and Character-
ization of New High Energy Dense Oxidizers (HEDO) - NICOP
Effort”) under contract nos. W911NF-09-2-0018 (ARL),
W911NF-09-1-0120 (ARDEC), W011NF-09-1-0056
(ARDEC), and 10 WPSEED01-002/WP-1765 (SERDP) is
gratefully acknowledged. We acknowledge collaborations with
Dr. Mila Krupka (OZM Research, Czech Republic) in the devel-
opment of new testing and evaluation methods for energetic
materials and with Dr. Muhamed Sucesca (Brodarski Institute,
Croatia) in the development of new computational codes to
predict the detonation and propulsion parameters of novel
explosives. We are indebted to and thank Drs. Betsy M. Rice
and Brad Forch (ARL, Aberdeen, Proving Ground, MD) and
Mr. Gary Chen (ARDEC, Picatinny Arsenal, NJ) for many help-
ful and inspired discussions and support of our work. Mr. Stefan
Huber is thanked for performing the sensitivity tests.
́
̧
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