Chemistry of Tetraazapentalenes

Article abstract of DOI:10.1021/jo972252x

2,4,8,10-Tetranitrobenzotriazolo[2,1-a]benzotriazole (TACOT), although thermally very stable and insensitive as an explosive, is susceptible to attack by nucleophiles. Reaction with azide ion results in displacement of nitro groups at the 4,10-positions, treatment with methoxide ion effects displacement of the hydrogen atom at the 1-position and scission of the remote triazole ring, while "vicarious nucleophilic animation" displaces all the aromatic hydrogens. 3,5,7-Trinitro-1,2,3-triazolo[2,1-a]benzotriazole and 3,5,7-trinitro-1,2,3-triazolo[1,2-a]benzotriazole are prepared readily by nitration of the parent triazolobenzotriazoles. However they are thermally less stable than TACOT and more sensitive to initiation by impact. Furthermore, attempted further nitration and reaction with nucleophiles such as azide and methoxide ions both effect scission of the triazole ring to leave 4,6-dinitrobenzotriazole.

Full text of DOI:10.1021/jo972252x

3352
J . Org. Chem. 1998, 63, 3352-3356
Ch em istr y of Tetr a a za p en ta len es
Karen L. Altmann, Andrew P. Chafin, Lawrence H. Merwin, and William S. Wilson*
Research and Technology Group, Naval Air Warfare Center Weapons Division,
China Lake, California 93555-6100
Richard Gilardi
Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, D.C. 20375-5341
Received December 11, 1997
2,4,8,10-Tetranitrobenzotriazolo[2,1-a]benzotriazole (TACOT), although thermally very stable and
insensitive as an explosive, is susceptible to attack by nucleophiles. Reaction with azide ion results
in displacement of nitro groups at the 4,10-positions, treatment with methoxide ion effects
displacement of the hydrogen atom at the 1-position and scission of the remote triazole ring, while
“vicarious nucleophilic amination” displaces all the aromatic hydrogens. 3,5,7-Trinitro-1,2,3-triazolo-
[2,1-a]benzotriazole and 3,5,7-trinitro-1,2,3-triazolo[1,2-a]benzotriazole are prepared readily by
nitration of the parent triazolobenzotriazoles. However they are thermally less stable than TACOT
and more sensitive to initiation by impact. Furthermore, attempted further nitration and reaction
with nucleophiles such as azide and methoxide ions both effect scission of the triazole ring to leave
4,6-dinitrobenzotriazole.
In tr od u ction
The extreme thermal and chemical stability (mp
237-8 °C; sublimes unchanged at atmospheric pressure)
of benzotriazolo[2,1-a]benzotriazole (1; dibenzo-1,3a,4,-
6a-tetraazapentalene)1 (Figure 1) have made this an
attractive ring system around which to construct insensi-
tive and thermally stable energetic materials. Thus the
tetranitro derivative 2 (TACOT, so-named to reflect the
tetraa zacyclooctatetraene core initially assumed for
these compounds)2 is the most thermally stable explosive
known,3 although its explosive performance is modest at
best.4 Attempts to enhance the performance of 2 by
further derivatization and improvement of the oxygen
balance have formed the basis for a recent series of
papers5 and encouraged us to present the results of our
own research into the varied chemistry of tetraazapen-
talenes.
F igu r e 1. Numbering system for benzotriazolo[2,1-a]benzo-
triazoles.
Two obvious targets for potentially insensitive but
powerful tetraazapentalenes are the tetraaminotetranitro
derivative (3) and the octanitro variant (4). The former
compound should have increased density and ensured
stability and insensitivity, as a consequence of hydrogen
bonding between the alternating amino and nitro groups,
but improvement in performance would be modest (Table
1). The latter compound should have markedly enhanced
density and performance, but stability and insensitivity
would be limited to that conferred by the inherent
stability of the dibenzotetraazapentalene skeleton, mod-
erated by the chemical lability of the vicinal nitro groups.
(1) Carboni, R. A.; Castle, J . E. J . Am. Chem. Soc. 1962, 84, 2453.
Carboni, R. A.; Kauer, J . C.; Castle, J . E.; Simmons, H. E. J . Am. Chem.
Soc. 1967, 89, 2618.
(2) Carboni, R. A.; Kauer, J . C.; Hatchard, W. R.; Harder, R. J . J .
Am. Chem. Soc. 1967, 89, 2626.
(3) Benson, F. R. The High Nitrogen Compounds; Wiley-Inter-
science: New York, 1984; p 394. Urbanski, T.; Vasudeva, S. K. J . Sci.
Ind. Res. 1978, 37, 250.
(4) (a) Densities (F) quoted are those calculated by the method of
Cichra, D. A.; Holden, J . R.; Dickinson, C. Estimation of Normal
Densities of Explosive Compounds from Empirical Atomic Volumes;
Silver Spring, MD, Naval Surface Weapons Center report TR 79-273.
Available from the National Technical Information Service, U.S.
Department of Commerce, Springfield, VA 22161, Feb 1980. (b)
Explosive performance (velocity of detonation (Dv) and detonation
pressure (PCJ )) were calculated using the method of Rothstein, L. R.;
Petersen, R. Propellants Explos. 1979, 4, 56; 1981, 6, 91. (c) Impact
sensitivity is measured using the Bureau of Mines impact machine
with Type 12 tools. A 2.5 Kg weight is dropped onto a 35 mg sample
on garnet paper resting on a flat tool steel anvil, and the 50% drop
height (h50%) is that at which an explosive event occurs in 50% of tests.
(5) (a) Subramanian, G.; Boyer, J . H.; Buzatu, D.; Stevens, E. D.;
Trudell, M. L. J . Org. Chem. 1995, 60, 6110. (b) Subramanian, G.;
Boyer, J . H.; Trudell, M. L.; Koppes, W. M.; Sitzmann, M. E.; Nock, L.
A.; Gilardi, R.; Russell, T. P. J . Org. Chem. 1996, 61, 1898. (c)
Subramanian, G.; Eck, G.; Boyer, J . H.; Stevens, E. D.; Trudell, M. L.
J . Org. Chem. 1996, 61, 5801.
Resu lts a n d Discu ssion
Carboni originally proposed the structure 2,4,8,10-
tetranitrobenzotriazolo[2,1-a]benzotriazole (2) for TACOT,2
but more recent authors have clouded the picture with
reference to different structures, and even mixtures of
positional isomers.6 We have confirmed that nitration
of 1 occurs preferentially at the 2(and 8)-positions fol-
lowed by the 4(and 10)-positions. Selective mono-, di-,
and trinitration may be obtained by careful choice of
(6) Urbanski, T. Chemistry and Technology of Explosives, Vol. 4;
Pergamon Press: Oxford, 1984; p 211. Meyer, R. Explosives, 2nd ed.;
Verlag Chemie: Weinheim, 1981; p 323.
S0022-3263(97)02252-4 CCC: $15.00 © 1998 American Chemical Society
Published on Web 04/23/1998

Chemistry of Tetraazapentalenes
J . Org. Chem., Vol. 63, No. 10, 1998 3353
Ta ble 1. Exp losive P er for m a n ce of
Sch em e 2. Nu cleop h ilic Scission of Tr ia zole Rin g
Ben zotr ia zolo[2,1-a ]ben zotr ia zoles4
mp (°C) F (g/mL) Dv (m/s) PCJ (kbar) h50% (cm)
R ) H (2)
R ) NH2 (3)
R ) NO2 (4)
410
1.82
1.86
2.00
7060
7570
8590
203
250
346
>200
Sch em e 1. Nu cleop h ilic Disp la cem en t in TACOT
Sch em e 3. Vica r iou s Nu cleop h ilic Su bstitu tion
(VNS)
pound. Surprisingly, 7 proved resistant to both hydroly-
sis to the 4,10-diamino compound and to further nitration
and gave only decomposition under forcing conditions.
Initial uncertainty regarding the course of the nucleo-
philic displacement by azide ion prompted us to examine
the reaction of 2 at ambient temperature with methanolic
sodium methoxide, selected to provide a convenient signal
for NMR analysis (Scheme 2). However, the reaction
took a substantially different course; instead of displace-
ment of a nitro group, addition of methoxyl occurred at
the 1-position, followed by scission of the remote triazole
ring to give 2-(2′-amino-3′,5′-dinitrophenyl)-7-methoxy-
4,6-dinitrobenzotriazole (8). The structure was deduced
on the basis of IR, NMR (1H, 13C, and short- and long-
range coupling experiments), and mass spectroscopy and
was confirmed by X-ray crystallographic analysis.8 While
nucleophilic attack of benzotriazolo[2,1-a]benzotriazole
and its derivatives at the 1-position has not previously
been reported, there is precedent for scission of the
triazole ring in the reduction of 1 with lithium aluminum
hydride, in its oxidation with peracetic acid and in the
reaction of its 2-bromo- and 2,8-dibromo derivatives with
cuprous cyanide.2a It should also be noted that the
methoxyl group in 8 is quite labile and undergoes facile
nucleophilic displacement by ammonia, by azide ion, or
even by adventitious moisture.7
A method frequently convenient for the synthesis of
polyaminopolynitroaromatics is the so-called “vicarious
nucleophilic substitution” of hydrogen (VNS) on a suit-
able polynitroaromatic. An early transformation of this
type was Meisenheimer’s synthesis of 2,4-diamino-1,3-
dinitrobenzene by treatment of m-dinitrobenzene with
hydroxylamine under basic conditions at ambient tem-
perature.10 More recent VNS reagents have included
4-amino-1,2,4-triazole,11 sulfenamides,12 and trimethyl-
hydrazinium iodide,13 each with a strong base in a polar
aprotic solvent at ambient temperature. Subjecting 2 to
the VNS conditions using either hydroxylamine or tri-
methylhydrazinium iodide gave a very insoluble red solid,
which melts with decomposition at 350 °C and which was
provisionally identified as 1,3,7,9-tetraamino-2,4,8,10-
tetranitrobenzotriazolo[2,1-a]benzotriazole (3) (Scheme
reaction conditions, but duplication of Carboni’s mixed
acid nitration at 60 °C gave a single pure isomer, fully
consistent by 1H and 13C NMR spectroscopy with 2.7 The
material reproduced in these laboratories was identical
in all respects with the commercial product obtained from
DuPont. Final confirmation of the structure was afforded
by X-ray crystallographic analysis.8
Further nitration of 2 to 4 cannot be achieved by direct
methods; a more productive approach might be selective
reduction of two of the nitro groups to amines, followed
by nitration at the now activated positions and finally
reoxidation of the amines, in the manner used to prepare
polynitroaromatics such as hexanitrobenzene.9 Unfor-
tunately, selective reduction of the nitro groups in
TACOT proved difficult, but a variant of this approach
suggested itself. Treatment of 2 with lithium azide in
DMF at 80-85 °C was reported to give, by nucleophilic
displacement of one pair of nitro groups, a single sym-
metrical diazidodinitro compound, whose structure could
not be assigned unequivocally at that time.2 Apparently
the same compound was obtained using sodium azide in
DMSO at 100 °C5a and was tentatively assigned the
structure 5 (4,10-diazido-2,8-dinitrobenzotriazolo[2,1-a]-
benzotriazole) on the basis of its 1H NMR spectrum
(Scheme 1). Reaction of this material with triphenylphos-
phine in ethanol or benzene, at ambient temperature or
under reflux, gave an exceedingly insoluble purple solid
presumed on the basis of infrared and mass spectroscopy
to be the bis(triphenylphosphinimine) 6. Hydrolysis of
this phosphinimine required more vigorous conditions
than are usually necessary, but concentrated hydrochloric
acid in acetic acid under reflux gave 4,10-bis(acetamido)-
2,8-dinitrobenzotriazolo[2,1-a]benzotriazole (7), whose
structure was confirmed by X-ray crystallographic analy-
sis of a solvated crystal grown from DMSO,8 thereby also
supporting the structure 5 for the diazidodinitro com-
(7) Wilson, W. S. Unpublished results.
(8) The authors have deposited atomic coordinates for structures
with the Cambridge Crystallographic Data Centre. The coordinates
may be obtained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, U.K.
(9) Nielsen, A. T.; Atkins, R. L.; Norris, W. P. J . Org. Chem. 1979,
44, 1181. Nielsen, A. T.; Atkins, R. L.; Norris, W. P.; Coon, C. L.;
Sitzmann, M. E. J . Org. Chem. 1980, 45, 2341.
(10) Meisenheimer, J .; Patzig, E. Chem. Ber. 1906, 39, 2533.
(11) Katritzky, A. R.; Laurenzo, K. S. J . Org. Chem. 1986, 51, 5039.
(12) Makosza, M.; Bialecki, M. J . Org. Chem. 1992, 57, 4784.
(13) Pagoria, P. F.; Mitchell, A. R.; Schmidt, R. D. J . Org. Chem.
1996, 61, 2934.

3354 J . Org. Chem., Vol. 63, No. 10, 1998
Altmann et al.
Sch em e 6. Nitr a tion of
1,2,3-Tr ia zolo[2,1-a ]ben zotr ia zole (12)
F igu r e 2. Explosive performance properties of isomeric
trinitrobenozotriazoles.
Sch em e 4. Syn th esis of
1,2,3-Tr ia zolo[2,1-a ]ben zotr ia zole (12)
Sch em e 7. Nitr a tion of
1,2,3-Tr ia zolo[1,2-a ]ben zotr ia zole (14)
Sch em e 5. Syn th esis of
1,2,3-Tr ia zolo[1,2-a ]ben zotr ia zole (14)
lene to 2-azidonitrobenzene. In contrast to that of 1, 12
and 14 have melting points of only 108-9 and 121-2
°C.2a,14
Nitration of 1,2,3-triazolo[2,1-a]benzotriazole (12) can
be achieved selectively, occurring first at the 7-position
which is followed by nitration at the 3- and 5-positions.
Thus, while 12 is unaffected by treatment with 25% nitric
acid, 45% nitric acid gives the 7-nitro derivative (15, 39%)
and the 3,7-dinitro compound (16, 58%), and 70% nitric
acid yields a mixture of 16 (52%) and the 5,7- and 3,5-
isomers 17 (23%) and 18 (ca. 5% by NMR, but not
isolated). Clean trinitration to 3,5,7-trinitro-1,2,3-tria-
zolo[2,1-a]benzotriazole (9) was achieved using 3 equiv
of 100% nitric acid in 98% sulfuric acid at ambient
temperature. In contrast with the stability of TACOT
(2) to these conditions, however, nitration of 12 with a
12-fold excess of 100% nitric acid in 98% sulfuric acid
resulted in disruption of the triazole ring to leave the
previously known15 4,6-dinitrobenzotriazole (19). The
structures of 9, 15, 16, 17, and 18 (Scheme 6) were
3). The low solubility made purification difficult and
recrystallization and solution state NMR spectroscopy
impossible, but solid state NMR is consistent with the
assigned structure, as is the infrared spectrum which
shows the presence of -NO2’s and two distinct -NH2’s,
but no CH’s. The mass spectrum does not show the
expected parent ion at m/z 448. However, the base peak
at m/z 239 corresponds to diaminodinitrobenzotriazole,
a fragment ion expected from 3. In common with other
high nitrogen compounds, and particularly other tet-
raazapentalenes, elemental analysis for nitrogen is low
but carbon and hydrogen are in reasonable agreement
with the values expected.
Tr ia zoloben zotr ia zoles. If the thermal and chemical
stability of the dibenzo-1,3a,4,6a-tetraazapentalene (ben-
zotriazolo[2,1-a]benzotriazole) ring system were also
found in the monobenzo compounds, then the latter may
similarly provide appropriate bases from which to design
new insensitive energetic materials. For example, the
isomeric trinitro compounds 9 and 10 (Figure 2) should
be more energetic than TACOT (2) as a consequence of a
more favorable oxygen balance, and further substitution
should lead to even more powerful explosives.
1
assigned on the basis of H and 13C NMR spectroscopy;
the structures of 9 and 17 were confirmed unequivocally
by X-ray crystallographic analysis.8
Nitration of 1,2,3-triazolo[1,2-a]benzotriazole (14) with
70% nitric acid gave a complex mixture of mono- and
dinitro derivatives, from which was isolated the 3,5-
dinitro compound (20, 47%). Trinitration to 3,5,7-trini-
tro-1,2,3-triazolo[1,2-a]benzotriazole (10) was achieved
cleanly and in 80% yield using 3 equiv of 100% nitric acid
in 98% sulfuric acid at ambient temperature (Scheme 7).
In the absence of crystals suitable for X-ray analysis,
The parent heterocyclic ring systems 1,2,3-triazolo[2,1-
a]benzotriazole (12; 2,3-benzo-1,3a,4,6a-tetraazapenta-
lene) and 1,2,3-triazolo[1,2-a]benzotriazole (14; 1,2-benzo-
1,3a,4,6a-tetraazapentalene) were prepared by heating
2-(2′-nitrophenyl)-1,2,3-triazole (11) and 1-(2′-nitrophen-
yl)-1,2,3-triazole (13) respectively in trialkyl phosphite
(Schemes 4 and 5). The isomeric aryltriazoles may be
prepared in a 3:1 ratio from 1,2,3-triazole and 2-fluoroni-
trobenzene and separated by vacuum distillation, but 13
is more conveniently obtained by cycloaddition of acety-
1
structural assignment of 20 and 10 was based on H and
13C NMR spectroscopy and on analogy with the related
compounds described above.
With melting points (decomposition) of 250-3 °C and
265-6 °C, respectively, the trinitro compounds 9 and 10
(14) Kauer, J . C.; Carboni, R. A. J . Am. Chem. Soc. 1967, 89, 2633.
(15) Nietzki, R.; Hagenbach, H. Ber. 1897, 30, 543.

Chemistry of Tetraazapentalenes
J . Org. Chem., Vol. 63, No. 10, 1998 3355
reaction was carried out in ethanol at ambient temperature
for 24 h or in benzene solution under reflux for 4 h. This
material was too insoluble in the available deuterated solvents
(including cloroform, acetone, hot DMSO, hot DMF, and
methanol) for measurement of NMR spectra, but the IR
spectra displayed clean, sharp signals, with a notable absence
of any azide signals around 2100 cm-1. The compound was
tentatively identified with the structure 6. IR: 1600, 1515,
1495, 1440 cm-1. M/z: 848 (parent ion, discernible), 278, 78
(base peak).
are thermally quite stable, without however approaching
the unprecedented stability of TACOT. On the other
hand, 9 and 10 each have a 50% drop height (h50%) of 26
cm in the dropweight impact test, indicating a sensitivity
comparable with RDX (cyclotrimethylenetrinitramine).
While it is possible that the sensitivity may be a
consequence of the asymmetry of the triazolobenzotri-
azole nuclei, these results suggest that energetic materi-
als based on the triazolo[2,1-a]triazole ring system may
also be rather sensitive. Finally, attempted nucleophilic
attack of either 9 or 10 with azide or methoxide ion also
gave 4,6-dinitrobenzotriazole (19), although the parent
heterocycle 12 was inert to attack by methoxide ion.
Clearly the nitrotriazole ring is prone to rupture by either
electrophilic (NO2+) or nucleophilic (MeO-) species, and
it is probable that the initial processes in impact initia-
tion of 9 and 10 are also localized in this portion of the
molecule(s).
4,10-Bis(acetam ido)-2,8-din itr oben zotr iazolo[2,1-a ]ben -
zotr ia zole (7). 4,10-Bis(triphenylphosphinimino)-2,8-dini-
trobenzotriazolo[2,1-a]benzotriazole (6) (0.58 g, 0.68 mmol) was
added to glacial acetic acid (50 mL), followed by concentrated
hydrochloric acid (5 mL), and the mixture was heated under
reflux with stirring for 48 h, during which time a brick red
solid was formed. The solid was filtered off and washed by
heating overnight in ethanol (50 mL) under reflux. Filtration
and drying gave 0.23 g (82%). Recrystallization from DMSO
gave 4,10-bis(acetamido)-2,8-dinitrobenzotriazolo[2,1-a]ben-
zotriazole (7)8 (solvated with 2 mol of DMSO) (0.22 g, 67%),
mp 408 °C (dec) (endotherm at ca. 130 °C; loss of DMSO). IR:
3260, 1670, 1605 cm-1 1H NMR (DMSO-d6): 10.63 (br s, 2H,
.
Con clu sion
NH's), 9.22 (d, J ) 2.06 Hz, H1,7), 8.74 (d, J ) 2.06 Hz, H3,9),
2.53 (s, 12H, (CH3)2SO), 2.33 (s, 6H, COCH3’s). 13C NMR
(DMSO-d6): 169.6 (CO’s), 142.5 (C2,8), 140.7 (C1a,7a), 128.1
(C4,10), 117.3 (C4a,10a), 110.4 (C1,7), 103.0 (C3,9), 39.7 ((CH3)2SO),
23.5 (CH3’s). (Assignments are not unequivocal.) M/z: 412
(parent ion), 370, 328 (base peak), 282, 78, 63. DMSO was
also separated and detected (78 (parent ion), 63 (base peak)).
2-(2′-Am in o-3′,5′-d in it r op h en yl)-7-m et h oxy-4,6-d in i-
tr oben zotr ia zole (8). 2,4,8,10-Tetranitrobenzotriazolo[2,1-
a]benzotriazole (TACOT, 2) (1.00 g, 3.6 mmol) was added to
methanolic sodium methoxide (1.00 g sodium metal in 100 mL
of methanol) at ambient temperature. The solid appeared to
dissolve to give a deep red solution, whereupon an orange solid
started to appear. After the reaction mixture was stirred at
ambient temperature for 24 h, the solid was filtered off and
washed with a little cold methanol (10 mL) to give a dirty
orange solid. Suspension in methanol (100 mL) and stirring
at ambient temperature for 3 h gave a clean orange solid (1.13
g), probably a Meisenheimer salt. (1H NMR (DMSO-d6): 9.04
(br s, NH2), 9.02 (s, 1H), 8.90 (d, J ) 2.76 Hz, 1H), 8.80 (d, J
) 2.76 Hz, 1H), 3.07 (s, OCH3, 6H).) Suspension in water (100
mL) and acidification with 37% hydrochloric acid gave a clean
yellow solid (0.85 g), recrystallized from acetone/ethanol to give
8 as ochre/yellow crystals (0.76 g),8 mp 229-232 °C. IR: 3400,
Although it is thermally very stable and explosively
insensitive, 2,4,8,10-tetranitrobenzotriazolo[2,1-a]benzo-
triazole (TACOT) is surprisingly susceptible to a variety
of nucleophilic substitution reactions. Reaction with
azide ion results in displacement of the nitro groups at
the 4,10-positions. Reaction with methoxide ion affords
displacement of the hydrogen atom at the 1(7)-position,
followed by scission of the remote triazole ring. Vicarious
nucleophilic amination apparently yields the tetrami-
notetranitro compound.
The trinitrotriazolobenzotriazoles have less thermal
stability and are quite sensitive to initiation by impact.
Furthermore, they are susceptible to both electrophilic
and nucleophilic attack, yielding 4,6-dinitrobenzotriazole
on attempted further nitration or when treated with
azide or methoxide ion. The annelated nitrotriazole ring
appears to be responsible for this thermal, explosive, and
chemical reactivity, and triazolobenzotriazoles are prob-
ably not a viable source of insensitive explosive ingredi-
ents.
3280, 3100, 1625, 1580, 1535 cm-1 1H NMR (DMSO-d6): 9.09
.
(s, H5), 9.07 (d, J ) 2.80 Hz, H4′), 8.87 (d, J ) 2.80 Hz, H6′),
8.45 (br s, NH2), 4.75 (s, OCH3). 13C NMR (DMSO-d6): 152.1
(C7), 144.3 (C2′), 140.8 (C3a), 138.4 (C7a), 133.6 (C5′), 132.8 (C4),
131.9 (C3′), 128.7 (C6), 128.2 (C6′), 126.7 (C1′), 125.4 (C4′), 124.4
(C5), 63.7 (OCH3). (Note: NMR spectra should be run on
freshly prepared solutions, due to instability of 8 in this
solvent.) M/z: 420 (parent ion and base peak), 406, 405, 333,
328, 239, 209.
1,3,7,9-Tet r a a m in o-2,4,8,10-t et r a n it r ob en zot r ia zolo-
[2,1-a ]ben zotr ia zole (3). (a ) 1,1,1-Trimethylhydrazinium
iodide13 (0.58 g, 2.9 mmol) and sodium methoxide (0.31 g, 5.8
mmol) were added with stirring to dry DMSO (8 mL) at
ambient temperature. 2,4,8,10-Tetranitrobenzotriazolo[2,1-a]-
benzotriazole (TACOT, 2) (0.23 g, 0.6 mmol) was added, and
the mixture was stirred at ambient temperature overnight
before being quenched in water (50 mL). The resultant fine
precipitate was filtered off and washed with water (2 × 50
mL) and then ethanol (50 mL) before being dried to give a dark
red brown solid (0.24 g, 90%), mp 350 °C (dec). IR: 3403, 3366,
3295, 3251, 1619, 1583, 1507 cm-1. M/z: 239 (base peak), 224,
118, 91, 77, 68, 67. Anal. Calcd for C12H8N12O8: C, 32.15; H,
1.80; N, 37.50. Found: C, 32.01; H, 2.08; N, 33.35.
Exp er im en ta l Section
WARNING: Compounds described in this report are po-
tentially explosive and may be subject to accidental initiation
by such environmental stimuli as impact, friction, heat, or
electrostatic discharge. Appropriate precautions should there-
fore be taken in their handling and/or use.
4,10-Dia zid o-2,8-d in itr oben zotr ia zolo[2,1-a ]ben zotr i-
a zole (5). 2,4,8,10-Tetranitrobenzotriazolo[2,1-a]benzotriazole
(TACOT, 2) (3.10 g, 8.0 mmol) was added to DMSO (65 mL),
and the mixture was heated to 100 °C. Sodium azide (1.95 g,
30.0 mmol) was added slowly and with stirring, and the
mixture was heated at 100 °C for 1 h, turning very deep red
in color. The mixture was allowed to cool to ambient temper-
ature overnight, and the orange solid was filtered off and
washed with ethanol (10 mL) and finally ether (10 mL) to give
5 (1.33 g, 46%), mp 197 °C (dec) (lit.5a mp 200 °C (dec)). IR:
2120, 1600, 1525, 1360 cm-1. 1H NMR (DMSO-d6, 35 °C): 9.03
(d, J ) 1.92 Hz, H1,7), 8.15 (d, J ) 1.92 Hz, H3,9).
4,10-Bis(t r ip h en ylp h osp h in im in o)-2,8-d in it r ob en zo-
tr ia zolo[2,1-a ]ben zotr ia zole (6). Triphenylphosphine (0.80
g, 3.1 mmol) was dissolved in benzene (200 mL) at ambient
temperature, and 4,10-diazido-2,8-dinitrobenzotriazolo[2,1-a]-
benzotriazole (5) (0.50 g, 1.3 mmol) was added. The reaction
mixture was stirred for 48 h to give a purple solution and a
dark purple solid. Filtration gave a purple solid (1.00 g, 90%),
mp 377 °C (dec). The same product was obtained when the
(b) Potassium hydroxide (2.00 g, 36 mmol) was dissolved
in water (20 mL) and cooled in an ice/water bath. Hydroxy-
lamine hydrochloride (0.20 g, 2.88 mmol) was added in
portions, followed by 2,4,8,10-tetranitrobenzotriazolo[2,1-a]-
benzotriazole (TACOT, 2) (0.20 g, 0.52 mmol). The reaction

3356 J . Org. Chem., Vol. 63, No. 10, 1998
Altmann et al.
mixture was stirred at ambient temperature overnight to give
an orange suspension. Acidification with concentrated hydro-
chloric acid gave a mustard-colored suspension. Filtration,
washing with water (2 × 50 mL) and ethanol (50 mL), and
finally drying gave a brown solid (0.20 g, 87%), identical with
that described above.
(0.22 g, 53%) identified by 1H NMR and mass spectrum as 4,6-
dinitrobenzotriazole (19).15
R ea ct ion of 3,5,7-Tr in it r o-1,2,3-t r ia zolo[2,1-a ]b en zo-
tr ia zole (9) w ith Sod iu m Meth oxid e. A solution of 3,5,7-
trinitro-1,2,3-triazolo[2,1-a]benzotriazole (9) (0.29 g, 1 mmol)
in acetonitrile (35 mL) was added to a solution of sodium
methoxide (0.023 g of sodium (1 mmol) in 15 mL of methanol)
at 0 °C. After 16 h of stirring at ambient temperature, the
solution was evaporated to dryness to give an orange solid.
This material was initially insoluble in dichloromethane, but
dissolved on addition of 50 mL of 1 N hydrochloric acid. The
organic layer was dried over magnesium sulfate and the
solvent removed to give an orange glassy solid (0.258 g;
solvated) identical to an authentic sample of 4,6-dinitroben-
zotriazole (19).15
3,5-Din itr o-1,2,3-tr iazolo[1,2-a ]ben zotr iazole (20). 1,2,3-
Triazolo[1,2-a]benzotriazole (14) (0.158 g, 1 mmol) was added
to 70% nitric acid (7 mL) held below 5 °C in an ice/water bath.
After 3 h below 5 °C, the solution was poured into H2O (50
mL) to give a fine suspension. Extraction with chloroform (3
× 25 mL), drying over magnesium sulfate, and evaporation of
the chloroform extract gave an orange solid (0.096 g), shown
by 1H NMR to be a complex mixture. Filtration of the aqueous
mother liquor gave an orange solid (0.117 g, 47%), identified
by 1H NMR as 3,5-dinitro-1,2,3-triazolo[1,2-a]benzotriazole.
Crystallization from acetonitrile gave 0.075 g of orange crystals
(mp 265-266 °C). 1H NMR (DMSO-d6): 9.44 (s, 1H), 9.31 (d,
J ) 2.53 Hz, 1H), 8.53 (dd, J m= 2.35, 9.51 Hz, 1H), 8.26 (dd,
J ) 0.53, 9.49 Hz, 1H); (acetone-d6): 9.50 (dd, J ) 0.60, 2.40
Hz, 1H), 9.14 (s, 1H), 8.59 (dd, J ) 2.12, 9.30 Hz, 1H), 8.21
(dd, J ) 0.62, 9.45 Hz, 1H). 13C NMR (DMSO-d6): 146.73,
142.25, 135.49, 122.90, 120.82, 117.92, 111.31. Anal. Calcd
for C8H4N6O4: C, 38.72; H, 1.62; N, 33.87. Found: C, 39.22/
38.99; H, 0.95/0.83; N, 34.31/34.08.
Nitr a tion of 1,2,3-Tr ia zolo[2,1-a ]ben zotr ia zole (12). (a )
Nitr a tion w ith 45% Nitr ic Acid . 1,2,3-Triazolo[2,1-a]ben-
zotriazole (12) (0.316 g, 2 mmol) was added to water (10 mL)
and cooled below 5 °C in an ice bath while 70% nitric acid (16
mL) was added. After 1 h below 10 °C, the solution was poured
into water (100 mL). The precipitate was filtered off and
washed with water and ether to give a brick red solid (0.160
g, 39%), which was recrystallized from acetonitrile (50 mL) to
give 7-n itr o-1,2,3-tr ia zolo[2,1-a ]ben zotr ia zole (15) (0.09 g,
25%), mp 245 °C (dec). 1H NMR (DMSO-d6): 8.95 (d, J ) 2.43
Hz, 1H), 8.78 (d, J ) 1.41 Hz, 1H), 8.53 (d, J ) 1.41 Hz, 1H),
8.33 (dd, J ) 2.33, 9.39 Hz, 1H), 7.80 (d, J ) 9.03 Hz, 1H).
Anal. Calcd for C8H5N5O2: C, 47.30; H, 2.48; N, 34.47.
Found: C, 45.65/45.42; H, 1.46/1.30, N, 33.52/33.49. The
reaction filtrate was extracted with ether (4 × 50 mL) to give
1
a brown solid (0.29 g, 53%), identified by H NMR as mainly
3,7-dinitro-1,2,3-triazolo[2,1-a]benzotriazole (16).
(b) Nitr a tion w ith 70% Nitr ic Acid . 1,2,3-Triazolo[2,1-
a]benzotriazole (12) (0.429 g, 2.7 mmol) was added to 70%
nitric acid (15 mL) held below 5 °C in an ice/water bath. After
3 h below 5 °C, the solution was poured into water (100 mL)
and extracted with chloroform (2 × 30 mL). The extract was
dried over magnesium sulfate and evaporated to dryness to
1
give an orange solid (0.537 g, 80%), shown by H NMR to be
a mixture of three isomeric dinitro compounds. Purification
by column chromatography (silica gel eluted with 40% ethyl
acetate/hexanes), followed by crystallization from acetonitrile,
gave 3,7-d in it r o-1,2,3-t r ia zolo[2,1-a ]b en zot r ia zole (16)
(0.130 g, 19%), mp 250-253 °C. 1H NMR (DMSO-d6): 9.48
(s, 1H), 9.24 (d, J ) 2.02 Hz, 1H), 8.50 (dd, J ) 2.16, 9.32 Hz,
1H), 8.31 (d, J ) 9.32 Hz, 1H). Anal. Calcd for C8H4N6O4: C,
38.72; H, 1.62; N, 33.87. Found: C, 39.31/39.09; H, 0.90/1.10;
N, 34.22/34.30. Further elution gave a yellowish orange solid
(0.18 g) which, after recrystallization from 10 mL of CH3CN,
3,5,7-Tr in itr o-1,2,3-tr iazolo[1,2-a ]ben zotr iazole (10). Ni-
tric acid (100%) (1.04 mL, 25 mmol) was added dropwise to a
solution of 1,2,3-triazolo[1,2-a]benzotriazole (14) (1.20 g, 7.6
mmol) in 98% sulfuric acid (30 mL) held below 5 °C in an ice/
water bath. The solution was allowed to warm to ambient
temperature, stirred for 20 min, and then poured into cold
water (200 mL). The precipitate was filtered off, washed with
water, and dried to give a bright yellow solid (1.78 g, 80%),
mp 283-286 °C. Recrystallization from acetonitrile (100 mL)
gave a bright yellow solid (1.213 g, 54%), mp 293-294 °C. IR
1
gave red crystals (0.04 g; 6%) identified by H and 13C NMR
as 5,7-d in itr o-1,2,3-tr ia zolo[2,1-a ]ben zotr ia zole (17).8 1H
NMR (DMSO-d6): 9.29 (d, J ) 2.08 Hz, 1H), 9.07 (d, J ) 1.39
Hz, 1H), 9.04 (d, J ) 2.09 Hz, 1H), 8.69 (d, J ) 1.37 Hz, 1H).
13C NMR (DMSO-d6): 142.8, 140.3, 136.6, 130.8, 122.0, 119.6,
113.1, 109.4
(KBr): 2923, 2852, 1522, 1285 cm-1 1H NMR (CD3CN): 9.70
.
(d, J ) 2.06 Hz, 1H), 9.32 (d, J ) 2.08 Hz, 1H), 8.93 (s, 1H);
(CD2Cl2): 9.89 (d, J ) 2.07 Hz, 1H), 9.49 (d, J ) 2.07 Hz, 1H),
8.82 (s, 1H); (DMSO-d6): 9.60 (s, 1H), 9.59 (d, J ) 1.7 Hz, 1H),
9.26 (d, J ) 2.0 Hz, 1H). 13C NMR (CD2Cl2): 140.13, 139.96,
135.34, 134.18, 123.13, 120.45, 116.67. Anal. Calcd for
C8H3N7O6: C, 32.78; H, 1.03; N, 33.45. Found: C, 32.93; H,
0.38; N, 33.48.
R ea ct ion of 3,5,7-Tr in it r o-1,2,3-t r ia zolo[1,2-a ]b en zo-
tr ia zole (10) w ith Sod iu m Azid e. A mixture of 3,5,8-
trinitro-1,2,3-triazolo[1,2-a]benzotriazole (10) (0.200 g, 0.68
mmol), 18-crown-6 (0.1 g), and finely powdered sodium azide
(0.3 g, 4.6 mmol) in acetonitrile (50 mL) was refluxed for 18
h. The solution was cooled and the solvent removed to give
0.29 g of a red solid (clearly solvated), identical to an authentic
sample of 4,6-dinitrobenzotriazole.
(c) Nitr a tion w ith 100% Nitr ic Acid (3 equ iv) in 98%
Su lfu r ic Acid . 1,2,3-Triazolo[2,1-a]benzotriazole (12) (6.32
g, 40 mmol) was dissolved in 98% sulfuric acid (100 mL) below
5 °C in an ice bath. Then 100% nitric acid (5 mL, 121 mmol)
was added dropwise. The solution was stirred at 5 °C for 3 h
and then poured into cold water (700 mL). The precipitate
was filtered off, washed with water, and then dried to give an
orange solid (10.73 g, 92%). Recrystallization from acetonitrile
(1.4 L) gave 3,5,7-t r in it r o-1,2,3-t r ia zolo[2,1-a ]b en zot r i-
a zole (9)8 (6.38 g, 55%), mp 271-272 °C. The mother liquors
were concentrated and cooled to give a further 2.21 g (18%)
for a total yield of 73%. IR (KBr): 3103.4 (m), 1544.0 (s),
1
1329.3 (s), 1144.0 (s) cm-1. H NMR (DMSO-d6): 9.75 (d, J )
2.06 Hz, 1H), 9.65 (s, 1H), 9.21 (d, J ) 2.06 Hz, 1H); (CD3CN):
9.44 (d, J ) 2.05 Hz, 1H), 9.28 (d, J ) 2.04 Hz, 1H), 9.03 (s,
1H). 13C NMR (DMSO-d6): 141.3, 141.1, 138.0, 134.2, 121.8,
120.4, 118.0, 115.1. M/z: 293 (80%, M+), 277 (10%). Anal.
Calcd for C8H3N7O6: C, 32.78; H, 1.03; N, 33.45. Found: C,
33.23; H, 0.54; N, 33.67.
Ack n ow led gm en t . The authors are pleased to
acknowledge the financial support of the Office of Naval
Research, Mechanics Division, and the sponsorship of
Scientific Officer, Dr. Richard S. Miller.
(d ) Nitr a tion w ith Excess 100% Nitr ic Acid (12 equ iv)
in 98% Su lfu r ic Acid . 1,2,3-Triazolo[2,1-a]benzotriazole (12)
(0.316 g, 2 mmol) was dissolved in 98% sulfuric acid (15 mL).
After the solution was cooled to below 5 °C in an ice/water
bath, 100% nitric acid (1.0 mL, 24 mmol) was added dropwise.
The cooling bath was removed and replaced by an oil bath at
45 °C. After 16 h at 45 °C, the mixture was cooled and poured
into ice water (100 mL). The clear bright yellow solution was
extracted with chloroform (3 × 40 mL) to give an orange solid
Su p p or tin g In for m a tion Ava ila ble: Crystal data collec-
tion, data reduction and structure solution and refinement for
compounds 2, 7, 8, 9, and 17 (30 pages). This material is
contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
J O972252X