Reactions of vicinal nitroamines with sulfur monochloride - A short and convenient route to fused 1,2,5-thiadiazoles and their N-oxides

Article abstract of DOI:10.1016/j.tetlet.2013.03.134

A convenient synthetic approach to fused 1,2,5-thiadiazoles and their N-oxides from vicinal nitroamines and sulfur monochloride has been developed.

Full text of DOI:10.1016/j.tetlet.2013.03.134

Tetrahedron Letters 54 (2013) 3075–3078
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Tetrahedron Letters
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Reactions of vicinal nitroamines with sulfur monochloride—a short
and convenient route to fused 1,2,5-thiadiazoles and their N-oxides
Lidia S. Konstantinova a, Ekaterina A. Knyazeva a, Natalia V. Obruchnikova a, Yuri V. Gatilov b,
Andrey V. Zibarev b, Oleg A. Rakitin a,
⇑
a N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospekt, 47, 119991 Moscow, Russia
b N.N. Vorozhtsov Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Lavrentiev Ave., 9, 630090 Novosibirsk, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
A convenient synthetic approach to fused 1,2,5-thiadiazoles and their N-oxides from vicinal nitroamines
and sulfur monochloride has been developed.
Received 9 January 2013
Revised 28 February 2013
Accepted 28 March 2013
Available online 11 April 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Sulfur-nitrogen heterocycles
Fused 1,2,5-thiadiazoles
2,1,3-Benzothiadiazole N-oxides
ortho-Nitroanilines
Sulfur monochloride
Fused 1,2,5-thiadiazoles have attracted much attention because
of their interesting chemical properties and various possibilities in
use as antibacterial and antiviral agents, agrochemicals, and as p-
been cyclized previously in the presence of S2Cl2 to give the corre-
sponding fused 1,2,5-thiadiazoles,4,5 however, to the best of our
knowledge, no direct exchange of oxygen with a sulfur atom in a
1,2,5-oxadiazole ring is known. Lawesson’s reagent, which per-
forms well in this exchange with various classes of compounds,6
does not react with 2,1,3-benzoxadiazole, even on heating to
150–160 °C in 1,2-dichlorobenzene.7 Further study of the synthesis
of 1,2,5-thiadiazoles led us to a new and even more unexpected
transformation of vic-amino-nitro derivatives into fused 1,2,5-thi-
adiazoles through their 1-oxides. In this Letter we report the syn-
thesis of fused 1,2,5-thiadiazoles from o-nitroamines and sulfur
monochloride.
We have studied the reaction between 3,4-dinitro- 3 and 4-ami-
no-3-nitro-1,2,5-oxadiazoles 4 and sulfur monochloride. Treat-
ment of compound 3 with S2Cl2 in the presence of pyridine in
acetonitrile under conditions similar to those used for the synthe-
sis of bicycle 2 from oxadiazole 13 gave no reaction, and starting
material 3 was recovered in almost quantitative yield. Treatment
of compound 4 with the same mixture led to derivative 2 in mod-
erate yield (Scheme 2).
type building blocks for organic electronics, particularly for both
low- and high-molecular weight organic light-emitting diodes
(OLEDs).1 Recently 1,2,5-thiadiazole derivatives were recognized
as efficient electron acceptors and were successfully used for the
preparation of radical-anion salts revealing antiferromagnetic ex-
change interactions in their spin systems,2 and conductive
charge-transfer complexes also possessing photoconductivity.3
Although methods for the preparation of fused 1,2,5-thiadiazoles
are numerous and well elaborated,1 there is still a lack of syntheses
of derivatives containing electron-deficient heterocycles or elec-
tron-withdrawing groups.
Recently, it was found that 3,4-diamino-1,2,5-oxadiazole (1), on
treatment with sulfur monochloride and pyridine in acetonitrile
gave, unexpectedly, [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2)
in high yield (Scheme 1).3
The main feature of this transformation is that two processes
occur simultaneously: formation of a 1,2,5-thiadiazole ring via
base-assisted condensation of a vic-diamine with sulfur monochlo-
ride, and exchange of the oxygen atom in the 1,2,5-oxadiazole ring
with a sulfur atom. The first reaction can be envisaged easily be-
cause 3,4-diamino-1,2,5-thiadiazole and o-phenylenediamine have
NH2
N
N
py
N
N
N
N
S
S
O
+ S2Cl2
MeCN
NH2
2
, 75%
1
⇑
Corresponding author. Tel.: +7 499 135 53 27; fax: +7 499 135 53 28.
E-mail address: orakitin@ioc.ac.ru (O.A. Rakitin).
Scheme 1. Synthesis of [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (2) from 3,4-
diamino-1,2,5-oxadiazole (1).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.03.134

3076
L. S. Konstantinova et al. / Tetrahedron Letters 54 (2013) 3075–3078
NH2
NO2
DMF—a solvent, which is frequently used in S2Cl2 reactions10—gave
amidine 5 in 60% yield (Scheme 3). Thus, DMF was not a suitable
solvent for the reactions of anilines with S2Cl2.
NO2
NO2
N
N
N
N
N
N
py
N
N
O
+ S2Cl2
S
S
O
MeCN
The type of a base used was important for the success of reac-
tions with S2Cl2 in other solvents (acetonitrile or chloroform). Tri-
ethylamine and N-ethyldiisopropylamine did not catalyze these
reactions at room temperature or at reflux. Treatment of 2,4-dini-
troaniline with S2Cl2 and 1,4-diazabicyclooctane (DABCO) in MeCN
led to a mixture of the target thiadiazole together with uncon-
sumed starting material, even in the presence of a large excess of
reagents. Reaction of 2,4-dinitroaniline with a fivefold excess of
S2Cl2 and pyridine led, selectively, after prolonged refluxing, to 5-
nitro-2,1,3-benzothiadiazole (6) in a moderate yield (Scheme 4).11
On further investigation of the reaction between 2,4-dinitroan-
iline and S2Cl2 it was found that the transformation could be
stopped at the formation of 6-nitro-2,1,3-benzothiadiazole 1-oxide
(7) using DABCO as the base and chloroform as the solvent. Deriv-
ative 7 can be converted into compound 6 in high yield with S2Cl2
and pyridine in acetonitrile using the same protocol as for 2,4-dini-
troaniline (Scheme 4). The structures of compounds 6 and 7 were
4
3
2, 49%
Scheme 2. Synthesis of compound 2 from oxadiazole 4.
The results obtained suggested an important role of the amino
group in the transformation of the oxadiazole ring into a thiadia-
zole. Although it is the second example where an oxygen atom in
a 1,2,5-oxadiazole ring is exchanged by a sulfur atom, the forma-
tion of the second 1,2,5-thiadiazole ring from the vic-amino-nitro
moiety was even more surprising because no similar reaction
was described previously in the literature. Since the basicity of
compound 4 (pKaBH+ = À4.46)8 is near to that of o-nitroanilines
(pKaBH+ of 2,4-dinitroaniline is À4.52),9 we tried to extend these
S2Cl2 reactions to readily available or commercial 2,4,6-trinitroan-
iline, 2,4-dinitroaniline, and o-nitroaniline.
In an attempt to find the best conditions for the synthesis of
benzothiadiazoles, we investigated the reaction of 2,4-dinitroani-
line with sulfur monochloride in detail. Treatment of S2Cl2 in
NO2
H
N
H
N
NH2
NO2
NH2
NO2
py
Sn
N
NMe2
+ S2Cl2
NH2
NO2
+
MeCN
NO2
+ Me2NCHO + S2 Cl2
O2N
NO2
O2N
10,10%
42%
5, 60%
Scheme 3. Reaction of 2,4-dinitroaniline with S2Cl2 in DMF.
n = 1,2
Scheme 6. Reaction of o-nitroaniline with S2Cl2.
NH2
NO2
N
N
N
N
py
DABCO
CHCl3
S
+ S2Cl2
S
MeCN
O2N
O2N
O2N
O
6, 33%
7
, 38%
S2Cl2, py, MeCN
83%
Scheme 4. Synthesis of fused 1,2,5-thiadiazoles 6 and 7.
Figure 1. XRD structures of compounds 6 and 7 (displacement ellipsoids at 30%).
NO2
NO2
NO2
NO2
NH2
NO2
Cl
N
N
py
N
N
DABCO
CHCl
+
S
+ S2Cl2
S
MeCN
O2N
3 O2N
O2N
NO2
O2N
O
8, 29%
9, 37%
17%
Scheme 5. Synthesis of thiadiazole 9 and its 1-oxide 8.

L. S. Konstantinova et al. / Tetrahedron Letters 54 (2013) 3075–3078
3077
NH2
NO2
N
S S
base
-SO
N
N
S2Cl2/py
N
N
Cyc
+ S2Cl2
Cyc
Cyc
Cyc
S
S
NO2
11
Scheme 7. A suggested mechanism for the synthesis of fused 1,2,5-thiadiazoles and their 1-oxides.
O
12
13
confirmed by X-ray diffraction (XRD, Fig. 1).12 The compounds
R
R
were also characterized by elemental analyses and spectral data
N
N
1 min
N
N
(NMR, MS, and IR).11
S
S
190 oC (R = H)
Treatment of 2,4,6-trinitroaniline (picramide) with a mixture of
S2Cl2 and DABCO in chloroform gave 4,6-dinitro-2,1,3-benzothiadi-
azole 1-oxide (8) in moderate yield (Scheme 5). Although a solu-
O2N
O2N
O
200o C (R = NO2)
6 (78%)
9 (67%)
7, 8
tion of compound
8 was unstable on storage at room
R = H, (6, 7); R = NO2 (8, 9)
temperature in organic solvents (e.g., chloroform or acetonitrile),
its structure was confirmed by the aforementioned methods. Reac-
tion of picramide with a mixture of S2Cl2 and pyridine in acetoni-
trile led to the formation of 4,6-dinitro-2,1,3-benzothiadiazole (9)
(37%) together with picryl chloride (17%) (Scheme 5).
The more basic compound o-nitroaniline reacted differently in
the presence of S2Cl2 and pyridine in chloroform, and gave a mix-
ture of bis-anilines 10 in low yields connected by one or two sulfur
atoms (NMR, MS, and IR), the 2-nitro group on the benzene ring re-
mained intact (Scheme 6).
S-
R
R
R
N+
N
N
N
S
- S
O
N
O
O2N
N
O
O2N
O2N
14
Scheme 8. Thermolysis of 1-oxides 7 and 8.
The described reaction provides a new synthetic pathway to
fused 1,2,5-thiadiazoles and their 1-oxides from vic-nitroamines.
To the best of our knowledge, this reaction was previously un-
known. The closest formal analogy is the reaction of nitroanilines
with (NSCl)3 affording 2,1,3-benzothiadiazoles.13 However, the
reaction pathways seem to be very different since the latter reac-
tion is thought to proceed via vicarious nucleophilic substitution
of hydrogen.14 Furthermore, persistent sulfur-nitrogen radicals
were detected in anilines/(NSCl)3 reaction mixtures by EPR.14
The key steps of the reactions described in this work may be ex-
plained by the sulfurization of the amine with sulfur monochloride
in the presence of the base to give N-thiosulfinylamines 11, as has
been described for other anilines,15 followed by cyclization into
1,2,5-thiadiazole 1-oxide 12 via a cycloaddition/retrocycloaddition
with extrusion of sulfur monooxide (SO) (the latter is thermody-
namically unstable and decomposes very rapidly).16 Final forma-
tion of 1,2,5-thiadiazole 13 from its 1-oxide 12 was confirmed by
separately converting the N-oxide 12 into 13 using the conditions
of the cyclization reaction (see Scheme 7). The obtained results
showed that vic-nitro-amines containing strong electron-with-
drawing substituents (nitro groups) on the benzene ring or at-
tached to an electron-deficient heterocycle (1,2,5-oxadiazole) can
take part in this reaction, since the ortho-nitro group should be
activated toward nucleophilic attack of an N-thiosulfinyl moiety.
It should be emphasized that 1,2,5-thiadiazole 1-oxides are rare
compounds. They have been obtained by the reaction of sulfur mono-
The reaction contributes to synthetic approaches to sulfur-nitrogen
heterocycles via sulfur chlorides and nitrogen reagents.24 The ni-
trated 2,1,3-benzothiadiazoles synthesized are of interest as pre-
cursors of persistent radical anions.2,25 The described
experimental procedures may serve as an efficient basis for a
new synthesis of 1,2,5-thiadiazoles fused with both carbo- and
heterocycles.
Acknowledgments
We gratefully acknowledge financial support from the Royal
Society (RS International Joint Project 2010/R3), from the Russian
Foundation for Basic Research (Project 13-03-00072), from the Pre-
sidium of the Russian Academy of Sciences (Programme No. 8, Pro-
ject 8.14) and from the Leverhulme Trust (Project IN-2012-094).
References and notes
1. (a) Koutentis, P. A. In Comprehensive Heterocyclic Chemistry III; Katritzky, A. R.,
Ramsden, C. A., Scriven, E. F. V., Taylor, R. J. K., Eds.; Elsevier: Oxford, 2008; pp
516–564. Vol. 5, Chapter 5.09; (b) Koutentis, P. A. In Science of Synthesis; Storr,
R. C., Gilchrist, T. L., Eds.; Georg Thieme Verlag KG: Stuttgart, 2003; pp 297–
348. Vol. 13, Chapter 13.11; (c) Todres, Z. V. Chalcogenadiazoles: Chemistry and
Applications; CRC Press/Taylor & Francis: Boca Raton, 2012.
2. (a) Zibarev, A. V.; Mews, R. In Selenium and Tellurium Chemistry: From Small
Molecules to Biomolecules and Materials; Woollins, J. D., Laitinen, R. S., Eds.;
Springer: Berlin, 2011; pp 123–149; (b) Gritsan, N. P.; Zibarev, A. V. Izv. Akad.
Nauk. Ser. Khim. 2011, 2091–2100 (Russ. Chem. Bull., 2011, 60, 2131–2140).
3. Pushkarevsky, N. A.; Lonchakov, A. V.; Semenov, N. A.; Lork, E.; Buravov, L. I.;
Konstantinova, L. S.; Silber, G. T.; Robertson, N.; Gritsan, N. P.; Rakitin, O. A.;
Woollins, J. D.; Yagubskii, E. B.; Beckmann, J.; Zibarev, A. V. Synth. Met. 2012,
162, 2267–2276.
4. Komin, A. P.; Street, R. W.; Carmack, M. J. Org. Chem. 1975, 40, 2749–2752.
5. Weinstock, L. M.; Davis, P.; Handelsman, B.; Tull, R. J. J. Org. Chem. 1967, 32,
2823–2829.
6. Ozturk, T.; Ertas, E.; Mert, O. Chem. Rev. 2007, 107, 5210–5278; (b) Brayton, D.;
Jacobsen, F. E.; Cohen, S. M.; Farmer, P. J. Chem. Commun. 2006, 206–208; (c)
Jesberger, M.; Davis, T. P.; Barner, L. Synthesis 2003, 1929–1958; (d) Cava, M. P.;
Levinson, M. I. Tetrahedron 1985, 41, 5061–5087.
chloride with o-aminonitroso derivatives17–19 and -dioximes.20 The
a
thermal behavior of these compounds was not investigated previ-
ously. We attempted to open the 1,2,5-thiadiazole ring to give o-nitr-
osothionitroso compounds 14 (similar to the ring-opening
transformation of 1,2,5-oxadiazole 1-oxides into o-dinitroso deriva-
tives).21 Earlier, reversible transformation of 2,1,3-benzothiadiazole
1-oxide into the corresponding o-nitrosothionitroso derivative was
observed in an argon matrix under low-temperature photochemical
conditions.22 In the thermal experiments, however, oxides 7 and 8,
upon heating at 190–200 °C, lose an oxygen atom to produce thi-
adiazoles 6 and 9 in high yields (Scheme 8). The thermal extrusion
of an oxygen atom from 1,2,5-oxadiazole 1-oxides is rare.23
7. Nagornikova, S. I.; Makarov, A. Yu.; Zibarev, A. V. unpublished results.
8. Tselinskii, I. V.; Mel’nikova, S. F.; Vergizov, S. N. Chem. Heterocycl. Compd. 1981,
17, 228–232.
9. Tamura, K.; Dan, M.; Moriyoshi, T. J. Chem. Res. (M) 1990, 849–865.
10. Rakitin, O. A.; Konstantinova, L. S. Adv. Heterocycl. Chem. 2008, 96, 175–229.
11. General procedure for the reaction of vic-amino-nitro derivatives with S2Cl2 and
pyridine in acetonitrile. S2Cl2 (0.72 mL, 9.00 mmol) was added dropwise to a
stirred solution of the vic-amino-nitro derivative (2.0 mmol) and pyridine
In conclusion, a new reaction, namely that of vicinal nitroam-
ines with sulfur monochloride, has been described as a one-pot
synthetic route to fused 1,2,5-thiadiazoles and their 1-oxides.

3078
L. S. Konstantinova et al. / Tetrahedron Letters 54 (2013) 3075–3078
(0.96 mL, 12.0 mmol) in dry MeCN (20 mL) under argon at À25 °C. The mixture
www.ccdc.cam.uk/conts/retrieving.html.
Compound 6: triclinic, space group P1, a = 5.7385(4), b = 7.8571(5),
ꢀ
was stirred for 20 h at room temperature and then refluxed for 15 h. The
mixture was cooled to 20 °C, filtered and the solvent evaporated under reduced
pressure. The residue was separated by column chromatography (silica gel
Merck 60, hexane/CH2Cl2 mixtures).
c = 8.3539(5) Å,
Z = 2, Dc = 1.734 g cmÀ3
R1 = 0.0309 (1779 I >2 (I)).
a = 112.262(2), b = 93.986(2), c
= 91.902(2)°, V = 347.02(4) Å3,
,
l
(Mo
K
a
) = 0.419 cmÀ1
, 2016 unique reflections,
r
ꢀ
1,2,5Thiadiazolo[3,4-c][1,2,5]thiadiazole (2b). Yield 49%. Colorless needles, mp
Compound 7: triclinic, space group P1, a = 4.1585(2), b = 9.5722(5),
116–118 °C (Lit.3 mp 117–118 °C).
c = 9.7750(6) Å,
V = 358.08(3) Å3, Z = 2, Dc = 1.829 g cmÀ3
unique reflections, R1 = 0.0295 (1885 I >2 (I)).
13. Domschke, G.; Heimbold, I. Z. Chem. 1987, 27, 31–32.
a
= 106.169(2),
b = 101.536(2),
c
= 98.104(2)°,
5-Nitro-2,1,3-benzothiadiazole (6). Yield 33%. Colorless needles, mp 126–127 °C
(Lit.26 mp 128 °C).
,
l
(Mo ,
K
a
) = 0.424 cmÀ1
2102
r
4,6-Dinitro-2,1,3-benzothiadiazole (9). Yield 37%. Light yellow solid, mp 127–
128 °C (Lit.27 mp 136–138 °C). 1H NMR (300 MHz, CDCl3) d: 9.33 (1H, d, CH, J
3.0), 9.37 (1H, d, CH, J 3.0). 13C NMR (75 MHz, CDCl3) d: 121.1, 125.4, 139.7,
147.1, 148.4, 155.2. MS (EI, 70 eV), m/z (%): 226 (M+, 65), 92 (25), 83 (30), 64
14. Domschke, G.; Mayer, R.; Bleisch, S.; Bartl, A.; Stasko, A. Magn. Reson. Chem.
1990, 28, 797–806.
15. (a) Inagaki, Y.; Okazaki, R.; Inamoto, N. Tetrahedron Lett. 1975, 16, 4575–4578;
(b) Inagaki, Y.; Okazaki, R.; Inamoto, N. Bull. Chem. Soc. Jpn. 1979, 52, 1998–
2001; (c) Okazaki, R.; Unno, M.; Inamoto, N. Chem. Lett. 1987, 16, 2293–2294;
(d) Sasaki, S.; Hatsushiba, H.; Yoshifuji, M. Chem. Commun. 1998, 2221–2222.
16. Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements; Butterworth-
Heinemann: Oxford, 1997.
17. Yavolovskii, A. A.; Kuklenko, E. A.; Ivanov, E. I. Chem. Heterocycl. Compd. 1996,
32, 856–858.
18. Yavolovskii, A. A.; Timofeev, O. S.; Ivanov, E. I. Chem. Heterocycl. Compd. 1998,
34, 976–978.
(15), 46 (15), 30 (100). IR (KBr),
1570, 1537, 1342 (NO2).
m
max, cmÀ1: 3111, 3078 (C–H), 1619 (C@N),
General procedure for the reaction of vic-amino-nitro derivatives with S2Cl2 and
DABCO in chloroform. S2Cl2 (0.80 mL, 5.0 mmol) was added dropwise to a
stirred solution of the vic-amino-nitro derivative (1.0 mmol) and DABCO
(1.12 g, 10.00 mmol) in CHCl3 (15 mL) under argon at À30 °C. The mixture was
stirred for 48 h at ambient temperature, refluxed for 5 h, cooled to 20 °C, and
worked-up as described above (silica gel Merck 60 was pretreated with
triethylamine prior to chromatography).
6-Nitro-2,1,3-benzothiadiazole 1-oxide (7). Yield 38%. Yellow solid, mp 149–
150 °C.
19. Yavolovskii, A. A.; Kishichenko, V. D.; Olijnichenko, O. A.; Ivanov, E. I. Russ. J.
Gen. Chem. 2005, 75, 457–460 (Zh. Obshch. Khim. 2005, 75, 493–496).
20. Pilgram, K. J. Org. Chem. 1970, 35, 1165–1169.
21. Nikonov, G. N.; Bobrov, S. In Comprehensive Heterocyclic Chemistry III; Katritzky,
A. R., Ramsden, C. A., Scriven, E. F. V., Taylor, R. J. K., Eds.; Elsevier: Oxford,
2008; pp 316–396. Vol. 5, Chapter 5.05.
22. Pedersen, C. L.; Lohse, C.; Polyakoff, M. Acta Chem. Scand. B 1978, 32, 625–631.
23. (a) Perera, R. C.; Smalley, R. K.; Rogerson, L. G. J. Chem. Soc., C 1971, 1348–1354;
(b) Takakis, I. M.; Hadjimihalakis, P. M. J. Heterocycl. Chem. 1991, 28, 1373–
1386.
24. (a) Garcia-Valverde, M.; Torroba, T. Eur. J. Org. Chem. 2006, 849–861; (b)
Torroba, T. J. Prakt. Chem. 1999, 341, 99–113.
25. (a) Larina, L.; Lopyrev, V. Nitroazoles: Synthesis, Structure and Applications;
Springer: Berlin, 2009; (b) Todres, Z. V. Ion-Radical Organic Chemistry: Principles
and Applications; CRC Press/Taylor & Francis: Boca Raton, 2009; (c) Todres, Z. V.
Organic Ion Radicals; CRC Press: Boca Raton, 2002.
26. Gieren, A.; Betz, H.; Huebner, T.; Lamm, V.; Neidlein, R.; Droste, D. Z.
Naturforsch. B 1984, 39, 485–496.
Anal. Calcd for C6H3N3O3S (197.17) C, 36.55; H, 1.53; N, 21.31. Found C, 36.37;
H, 1.46; N, 21.23. 1H NMR (300 MHz, CDCl3) d: 8.03 (1H, d, CH J 9.0), 8.27 (1H,
dd, CH, J 3.0 and 9.0), 8.46 (1H, d, CH, J 3.0). 13C NMR (75 MHz, CDCl3) d: 111.9,
124.6, 125.0, 138.1, 145.7, 151.2. MS (EI, 70 eV), m/z (%): 197 (M+, 65), 181 (90),
167 (40), 151 (15), 135 (80), 89 (35), 46 (100). IR (KBr),
m
max, cmÀ1: 3091, 2926
(C–H), 1596 (C@N), 1564, 1504, 1335 (NO2).
4,6-Dinitro-2,1,3-benzothiadiazole 1-oxide (8). Yield 29%. Dark yellow solid, mp
186–187 °C. Anal. calcd for C6H2N4O5S (242.17) C, 29.76; H, 0.83; N, 23.14.
Found C, 29.83; H, 0.75; N, 23.02. 1H NMR (300 MHz, CDCl3) d: 8.94 (1H, d, CH, J
3.0), 9.19 (1H, d, CH, J 3.0). 13C NMR (75 MHz, CDCl3) d: 118.1, 121.3, 124.2,
124.3, 129.3, 141.6. MS (EI, 70 eV), m/z (%): 242 (M+, 20), 226 (10), 196 (5), 64
(25), 46 (15), 30 (100). IR (KBr):
1515, 1332 (NO2).
mmax = 3071, 2923 (C–H), 1608 (C@N), 1539,
Thermolysis of 1,2,5-thiadiazole 1-oxides 7 and 8. Compound 7 or 8 (20 mg) was
heated for 1 min under argon at 190 °C (7) or at 200 °C (8). The residue was
separated by column chromatography (silica gel Merck 60, gradual elution
with light petroleum or mixtures with CH2Cl2). Yields: 6 (78%), 9 (67%).
12. XRD structures of compounds 6 (CCDC 929367) and 7 (CCDC 929368) will be
discussed elsewhere, crystallographic data can be obtained free of charge via
27. Pesin, V. G.; Khaletskii, A. M.; Sergeev, V. A. J. Gen. Chem. USSR (Engl. Transl.)
1963, 33, 1714–1719.