Synthesis of nitro, nitroso, azo, and azido derivatives of (4-R 1-5-R2-1,2,3-triazol-1-yl)-1,2,5-oxadiazoles by oxidation and diazotization of the corresponding amines

Article abstract of DOI:10.1007/s11172-006-0058-9

Nitro-, nitroso-, and azo-1,2,5-oxadiazoles with 4-R¹-5-R ²-1,2,3-triazol-1-yl substituents were synthesized by oxidation of amino-(1,2,3-triazol-1-yl)-1,2,5-oxadiazoles (aminotriazolylfurazans). Azido-1,2,5-oxadiazole was prepared b

Full text of DOI:10.1007/s11172-006-0058-9

Russian Chemical Bulletin, International Edition, Vol. 54, No. 8, pp. 1915—1922, August, 2005
1915
Synthesis of nitro, nitroso, azo, and azido derivatives of
(4ꢀR1ꢀ5ꢀR2ꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxadiazoles by
oxidation and diazotization of the corresponding amines
L. V. Batog,ꢀ L. S. Konstantinova, and V. Yu. Rozhkov
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation
Fax: +7 (495) 135 5328. Еꢀmail: mnn@ ioc.ac.ru
Nitroꢀ, nitrosoꢀ, and azoꢀ1,2,5ꢀoxadiazoles with 4ꢀR1ꢀ5ꢀR2ꢀ1,2,3ꢀtriazolꢀ1ꢀyl substituents
were synthesized by oxidation of aminoꢀ(1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxadiazoles (aminotriꢀ
azolylfurazans). Azidoꢀ1,2,5ꢀoxadiazole was prepared by diazotization of amino(triazoꢀ
lyl)furazan followed by treatment of the diazonium salt with sodium azide. Depending on the
nature of the substituents and the reagent, triazolylfurazans can undergo destruction to give
aminoꢀRꢀfurazans (R = NO2, N3, aminofurazanylazo), the amino group being formed from
the triazole ring.
Key words: 4ꢀaminoꢀ3ꢀ(1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxadiazoles, aminofurazans, oxidation,
hydrogen peroxide, dibromoisocyanurates, dichloroisocyanurates, hypohalogenites, diazotizaꢀ
tion, nitroꢀ, nitrosoꢀ, azoꢀ, and azidofurazans.
Recently, we developed a number of general methods
for the synthesis of previously unknown 4ꢀRꢀ3ꢀ(4ꢀR1ꢀ5ꢀ
R2ꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxadiazoles (triazolylfuraꢀ
zans) using 1,3ꢀdipolar cycloaddition of azidofurazans to
substituted acetylenes,1 morpholinonitroethylene,2 and
1,3ꢀdicarbonyl compounds.3 Study of the biological acꢀ
tivities of some of these compounds has shown that
triazolylfurazan derivatives are NO donors (exert selecꢀ
tive potentiating action on the NOꢀdependent activation
of soluble guanylate cyclase4). Therefore, it appeared perꢀ
tinent to study a number of chemical transformations of
triazolylfurazans in order to reach other functionally subꢀ
stituted derivatives of this class of compounds. Among
the structures we synthesized, an essential place is occuꢀ
pied by compounds having an NH2 group in the furaꢀ
zan ring.
This study deals with the transformation of amino(triꢀ
azolyl)furazans 1a—k into triazolylfurazans with nitro (2),
nitroso (3), azo (4), azoxy (5), and azide (6) groups in the
furazan ring through oxidation (by both peroxide and
singleꢀelectron oxidants) and diazotization followed by
treatment of the diazonium salts with sodium azide. We
meant to elucidate the influence of the triazole ring and
the nature and the position of substituents in this ring on
the reactivity of the amino group in the furazan ring.
The oxidation of the amino group in compounds 1a—f
to the nitro group was carried out using a number of
potent oxidative mixtures: 30% H2O2 with conc. H2SO4
and (NH4)2S2O8 or Na2WO4•2H2O, 30% H2O2 with 60%
oleum, conc. H2O2 with H2SO4 and Na2WO4•2H2O, and
CF3CO3H. Some of these mixtures have been successꢀ
fully used to convert various aminofurazans into nitro
derivatives.5—8 We found that the outcome of oxidation of
amines 1a—f depends not only on the reaction conditions
but also on the nature of substituents in the triazole ring.
It was shown that amines 1a—e can be oxidized to nitro
derivatives in good yields (52—90%) only on treatment
with a mixture of conc. H2O2 with conc. H2SO4 and
Na2WO4•2H2O (component molar ratio 86 : 39 : 3 per
mole of the amine) when the reaction is carried out at
room temperature or above, while amine 1f can be oxiꢀ
dized only using CF3CO3H (Scheme 1).
Nitro compound 2f is not formed under conditions
favorable for the synthesis of compounds 2a—e. When
CF3CO3H is taken for oxidation of amines 1a—c, the
triazole ring cleaves (see also Schemes 2 and 3) to give
3ꢀaminoꢀ4ꢀnitrofurazan (7) (yield up to 99%), or more
extensive destruction takes place. The oxidation of isomer
mixture 1a,b with CF3CO3H gave compound 7 in a nearly
quantitative yield. The use of a mixture of 30% H2O2 and
60% oleum for oxidation of these amines afforded nitro
compounds in only 10—15% yields. In the synthesis of
isomeric nitro(triazolyl)furazans 2a,b, no substantial inꢀ
fluence of the substituent position was found.
Nitro derivatives 2a—d,f were obtained in the crystalꢀ
line state; their physicochemical and spectroscopic charꢀ
acteristics are presented in Tables 1 and 2. Nitro comꢀ
pound 2e was isolated as an oil difficult to purify. The
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1859—1865, August, 2005.
1066ꢀ5285/05/5408ꢀ1915 © 2005 Springer Science+Business Media, Inc.

1916
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
Batog et al.
Scheme 1
nitroso derivative 3c (see Scheme 2), which was obtained
in a pure state in 39% yield. Under the same conditions,
amines 1a and 1b are converted into intensively blueꢀ
colored compounds (on chromatography they give blueꢀ
colored spots with Rf 0.61 and 0.43, respectively; elution
with CHCl3—Мe2CO—МeOH, 10 : 2 : 1). It can be sugꢀ
gested that these substances are nitroso derivatives 3a
and 3b (see Scheme 2). However, they were not isolated,
as being relatively stable in solutions at 0 °C, they apꢀ
peared unstable on attempted isolation by concentrating
or evaporation of solutions to dryness; according to TLC,
they were converted into mixtures of compounds.
Under conditions of synthesis of nitroso compounds
3a, a compound with Rf 0.36 (CHCl3—Me2CO—MeOH,
10 : 2 : 1) is formed as a byꢀproduct; this compound has
not been isolated in a pure state. Having assumed that this
can be azoxy derivative 5, we attempted to prepare this
product by oxidizing amine 1a with milder mixtures, used
normally for the synthesis of azoxy derivatives from
aminofurazans.7 It was found that compound 1a is not
oxidized with 30% H2O2 mixed with conc. H2SO4 or
conc. H2O2 mixed with Na2WO4•2H2O in CH2Cl2; treatꢀ
ment of this amine with (NH4)2S2O8 in water at 70 °C
induces destructive oxidation, giving rise to diaminoazoꢀ
furazan (9) (60%) (see Scheme 2).
Singleꢀelectron oxidants such as potassium permanꢀ
ganate in HCl, sodium dibromoisocyanurate (DBI), and
hypohalogenites have been used successfully for the prepaꢀ
ration of azo compounds from heterocyclic amines,10 in
particular, from diamines of the furazan series.11—13 In
order to prepare azofurazans 4, we studied the oxidation
of amines 1a,b,f—k (see Scheme 3) by the above oxidants
and by sodium dichloroisocyanurate (DCI). It was found
that the possibility of formation of azo compounds under
these conditions also depends on the nature of the subꢀ
stituent in the triazole ring. For example, amines 1f—k
are converted into azo compounds 4a—f in high yields
(see Scheme 3), whereas amines 1a and 1b, containing a
hydroxymethyl group, undergo destruction of the triazole
ring (see also Schemes 1 and 2); on treatment with КМnO4
in HCl, this results in the formation of azo compound 9,
while in the case of DBI, the reaction gives a multicomꢀ
ponent mixture of products containing, according to TLC
and mass spectra,14 macrocycle 10 and diamine 11. The
structures of azo derivatives 4a—f were determined relyꢀ
ing on the set of data of elemental analysis and spectroꢀ
R1
R2
R1
R2
a
b
c
d
e
f
H
CH2OH
H
CH2OH
H
H
H
g
h
i
j
k
COOH
COOEt
COOMe
COOEt
COMe
H
H
CH2OH
CH2OH
CH2Cl
Ph
COOMe
Me
Me
NO2
i. H2O2 (85—90%)—H2SO4 (conc.), Na2WO4.
product structure was confirmed by transforming it into
amino derivative 8 on treatment with morpholine (see
Scheme 1). The structure of 8 was established using the
set of data from elemental analysis, IR, 1H NMR,
13C NMR, and mass spectra (see Tables 1 and 2).
Little has been reported9 on the synthesis of nitrosoꢀ
furazans by oxidation of aminofurazans with ammonium
persulfate in H2SO4. For the targeted synthesis of nitꢀ
roso(triazolyl)furazans 3 by oxidation of amines 1a,b,e,
we used the same oxidative mixture as for the preparation
of the corresponding nitro derivatives; however, in order
to stop the oxidation after the formation of nitroso comꢀ
pounds, the reaction was carried out at low temperature
(–5 to 5 °C) and using a 1.5—2.3 times lower excess of the
oxidative mixture components with respect to the amine.
Conditions were selected for the oxidation of amine 1e to
1
scopy (IR, H and 13C NMR, and mass spectra) (see
Tables 1 and 2). Compounds 9—11 are apparently the
products of oxidation of diaminofurazan formed initially
upon destruction.
It was found15 that aminofurazans containing elecꢀ
tronꢀwithdrawing substituents are smoothly converted into
azides on diazotization with nitrosylsulfuric acid in a mixꢀ
ture of concentrated H2SO4 and H3РO4 followed by treatꢀ
ment of the diazonium salt with sodium azide. Therefore,

(4ꢀR1ꢀ5ꢀR2ꢀTriazolꢀ1ꢀyl)1,2,5ꢀoxadiazole derivatives Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
1917
Scheme 2
R1 = H, R2 = CH2OH (a); R1 = CH2OH, R2 = H (b); R1 = Ph, R2 = H (e)
Scheme 3
4: R1 = NO2, R2 = H (a); R1 = COOH, R2 = H (b); R1 = COOEt, R2 = H (c); R1 = R2 = COOMe (d); R1 = COOEt, R2 = Me (e); R1 = COMe,
2 = Me (f)
R
Reagents: i. NaNO2/H+, NaN3; ii. KMnO4/HCl, DBI, NaOCl; iii. DCI; iv. AcOBr; v. KMnO4/HCl; vi. DBI; vii. NaNO2/H2SO4,
H3PO4, NaN3.
we attempted to synthesize azido(triazolyl)furazans unꢀ
der these conditions using amines 1a,f as examples. Comꢀ
pound 1f was converted into azide 6 in a high yield,
whereas amine 1a underwent destruction of the triazole
ring to give 3ꢀazidoꢀ4ꢀaminofurazan (12) (23%) (see
Scheme 3) and, perhaps, more extensive decomposition.
The structure of azide 6 was determined based on elꢀ
emental analysis and in combination with spectroscopic
characteristics (see Tables 1 and 2).
furazans 1 into NO2, NO, N=N, and N3 groups. The
reactivity of amino(triazolyl)furazans 1 in the oxidation
and diazotization followed by treatment of the diazonium
salt with sodium azide was found to depend appreciably
on both the nature of the substituent in the triazole ring
and the nature of the reagent. Amines 1 behave similarly
to known aminofurazans with electronꢀwithdrawing subꢀ
stituents; however, in some reactions the triazole ring is
unstable, which results in the formation of a new amino
group at the furazan ring. Depending on the reaction
conditions, these transformations gave aminofurazans with
As a result of this study, we identified the conditions
for the transformation of the amino group in triazolylꢀ

1918
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
Batog et al.
Table 1. Some physicochemical characteristics of the compounds synthesized
Comꢀ
pound
Yield
(%)
(method)
M.p./°C
(solvent)
Rf
Found
Calculated
Molecular
formula
(%)
N
(solvent)
С
Н
2a
2b
2c
2d**
2f
67
52
39—40*
0.61 (СНСl3—Ме2СО–МеОН,
10 : 2 : 1)
0.43 (СНСl3—Me2CO—MeOH,
10 : 2 : 1)
0.37 (CHCl3—Me2CO—MeOH,
10 : 2 : 1)
0.89 (CHCl3—Me2СO—MeOH,
28.74
28.31
28.65
28.31
29.89
29.76
26.38
26.05
21.32
21.15
49.59
49.21
24.10
24.63
30.58
30.94
37.41
37.84
36.14
36.10
40.81
40.68
40.31
40.78
21.79
21.53
56.31
56.38
2.01
1.90
1.95
1.90
2.72
2.50
1.30
1.31
0.48
0.44
2.50
2.56
0.78
0.52
1.18
1.04
2.60
2.72
2.32
2.27
3.43
3.41
3.01
2.93
0.49
0.45
4.79
4.70
39.57
39.62
39.75
39.62
34.98
34.71
36.16
36.45
43.63
43.18
34.70
34.51
49.73
50.26
43.11
43.30
37.52
37.83
31.92
31.57
35.24
35.58
40.22
40.76
56.67
56.51
28.07
28.19
С5Н4N6O4
68—69
(ССl4)
103—104
(ether)
C5H4N6O4
80
C6H6N6O5
89.2
70
83—84
C5H3N6O3Cl
C4HN7O5
(СНСl3)
110—112
(СНСl3)
114—115
(РhH)
174—175
(СНСl3)
176—178*
10 : 2 : 1)
0.74
(PhH—AcOEt, 3 : 1)
0.47
(PhH)
0.69
(PhH—AcOEt, 2 : 1)
0.70
3c
4a
4b
4c
4d
4e
4f
39
C10H6N6O2
C8H2N14O6
C10H4N12O6
C14H12N12O6
C16H12N12O10
C16H16N12O6
C14H12N12O4
C6HN9O3
81 (A)
99 (B)
79 (A)
80 (B)
97
(PhH—AcOEt, 5 : 1)
0.88 (CHCl3—Мe2CO—MeOH,
10 : 2 : 1)
201—202
(РhH)
184—185*
81 (A)
96 (B)
91
0.62
(PhH—AcOEt, 5 : 1)
0.38
(PhH—AcOEt, 3 : 1)
0.43
(PhH—AcOEt, 3 : 1)
0.66
(PhH—AcOH, 3 : 1)
0.60
163—164
(МеОН)
159—160
83
76
69
(МеОН)
6
153 (decomp.)
20
nD 1.5872
8
162—163
(РhH)
C14H14N6O3
(PhH—AcOEt, 3 : 1)
* Not recrystallized.
** Found Cl, 15.35%; calculated, Cl — 15.38%.
Scheme 4
NO2 (7), N = N (9), and N3 groups (12); these are formed
from the amino group in the initial amine 1. This is indiꢀ
cated, for example, by the fact that aminonitrofurazan 7 is
formed in solutions of nitro(triazolyl)furazan 2a on storꢀ
age, as shown by TLC. In the absence of sodium azide in
the reaction mixture, no azide 12 is formed after diazotiꢀ
zation of amine 1a (i.e., the azide group in 12 is not
formed due to the destruction of the triazole ring).
diazo compounds 13 and 14 and their subsequent hydroꢀ
lysis (Scheme 4). A similar process16 also takes place
in some reactions of azides with 1,3ꢀdicarbonyl comꢀ
pounds, which give amines instead of 1ꢀsubstituted
1,2,3ꢀtriazoles.
Experimental
Apparently, the destruction of the triazole ring in
triazolylfurazans involves the intermediate formation of
The reactions were monitored and the product purity was
checked by TLC on Silufol UVꢀ254 plates (Czechia). IR spectra

(4ꢀR1ꢀ5ꢀR2ꢀTriazolꢀ1ꢀyl)1,2,5ꢀoxadiazole derivatives Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
Table 2. Spectroscopic characteristics of the compounds synthesizeda
1919
Comꢀ
pound
NMR (δ, J/Hz)
IR, ν/cm–1
1Н
13С
2a
4.78 (s, 2 H, CH2);
5.89 (s, 1 H, OH);
8.00 (s, 1 H, Н(4´))
4.71 (s, 2 H, СН2);
5.57 (s, 1 H, OH);
8.64 (s, 1 H, Н(5´))
4.62, 4.65 (both s,
2 H each, СН2);
54.80 (CH2); 113.18 (CH);
142.31 (CCH2); 146.21 (N(1´)C);
156.05 (CNO2)
56.28 (CH2); 125.48 (С(5´));
146.38 (N(1´)C); 150.77 (CCH2);
155.86 (CNO2)
53.10 (CH2); 54.05 (CH2);
138.27 (CCH2); 144.60 (CCH2);
149.91 (N(1´)C); 156.33 (CNO2)
3380, 1615, 1575, 1540, 1410, 1375, 1265,
1235, 1095, 1045, 980
2bb
2cb
3265, 3185, 1620, 1575, 1510, 1455, 1395,
1375, 1315, 1265, 1230, 1185, 1065, 1045,
1030, 985
3430, 3300, 3260, 2990, 2940, 2870, 1630,
1575, 1480, 1460, 1420, 1380, 1360, 1320,
1190, 1180, 1140, 1070, 1050, 1030, 1000,
980, 875
5.91 (s, 1 H, ОН)
2d
5.42 (s, 2 H, CH2);
8.78 (s, 1 H, H(5´))
35.52 (CH2); 127.20 (CH);
144.96 (CCH2); 145.49 (N(1´)C);
155.61 (CNO2)
3135 (CH), 3100, 1600, 1560, 1500, 1430,
1380, 1365, 1310, 1270, 1250, 1215, 1180,
1145, 1050, 1035, 1000, 980, 890, 830,
820, 765
2f
9.65 (s, 1 H, H(5´))
3145 (CH), 1610, 1570, 1560, 1530, 1395,
1380, 1350, 1290, 1180, 1170, 1040, 980,
900, 870, 830
3160 (CH), 1600, 1530, 1490, 1460, 1410,
1370, 1320, 1280, 1245, 1220, 1190, 1180,
1080, 1055, 1020, 985, 960, 940, 880, 830,
810, 775
3150 (CH), 1590, 1570, 1560, 1530, 1390,
1300, 1220, 1030, 980, 830, 760
3150 (CH), 1720 (CO), 1600, 1480, 1420,
1365, 1280, 1165, 1065, 1025, 985, 880, 760
3195, 3170 (CH), 3000, 2950, 2915 (Et),
1750, 1730 (CO), 1600, 1570, 1380,
1340, 1270, 1235, 1150, 1040, 775
3cc
7.54 (m, 3 H, Ph);
8.10 (d, 2 H, Ph,
J = 7.30);
9.14 (s, 1 H, CH)
9.76 (s, 1 H, H(5´))
121.98, 122.73, 126.60, 128.77 (Ph);
129.60 (C(5´)); 143.15; 148.99;
165.7 (CNO)
4a
4b
4c
127.47 (C(5´)); 146.15 (C(4));
153.26 (C(4´)); 157.30 (C(3))
121.44 (C—COOH); 127.66 (C(5´));
146.36 (N(1´)C); 157.49 (C—N=N)
13.97 (Me); 61.26 (CH2); 130.21;
130.48; 130.72; 139.77; 159.04 (C=O)
7.35 (s, 1 H, OH);
8.84 (s, 1 H, H(5´))
1.35 (t, 6 H, 2 Me,
J = 7.20); 4.35 (q,
4 H, 2 CH2, J = 7.20);
9.10 (s, 2 H, 2 CH)
4.11, 4.43 (both s,
3 H each, Me)
4d
4e
4f
53.48 (Me); 54.56 (Me);
2970, 1755, 1730 (CO), 1590,
1570, 1450, 1310, 1265, 1240, 1210, 1100,
1060, 998, 810
121.85 (C—CO); 138.47 (C—CO);
146.28 (N(1´)C); 157.17 (C—N=N);
158.72 (C=O); 161.21 (C=O)
9.44 (CH3CH2); 13.90 (CH3Ar);
60.81 (CH2); 136.26; 142.16;
144.73; 157.94; 159.78 (C=O)
1.40 (t, 3 H, Me,
J = 7.78); 2.65 (s, 3 H,
Me); 4.42 (m, 2 H,
CH2, J = 7.78)
2.62, 2.68 (both s,
3 H each, Me)
2980, 2300, 1730 (CO), 1620, 1570, 1510,
1420, 1380, 1340, 1290, 1260, 1130, 1080,
1020, 980, 910, 860, 850, 780, 710
140.63 (CMe); 142.62 (CAr);
144.80 (C—CO); 157.99 (C—N=N);
192.31 (C=O)
1700 (CO), 1680, 1580, 1560, 1500, 1470,
1390, 1380, 1360, 1300, 1220, 1100, 1070,
1020, 980, 960, 910, 890, 860, 700
6b
8c
9.59 (s, 1 H, H (5´))
125.74 (C(5´)); 144.75 (C(3));
149.76 (CN3); 154.78 (CNO2)
47.98; 65.22; 123.23; 125.81;
128.16; 128.73; 128.92; 143.87;
147.84; 154.74
3160 (CH), 2190, 2150 (N3), 1590, 1550,
1460, 1421, 1390, 1330, 1250, 1030, 980, 830
3124 (CH), 2972, 2924, 2896, 2856, 1596,
1568, 1436, 1268, 1248, 1240, 1116, 1068,
1012, 984, 840, 772
3.18 (t, 4 H, О(СН2)2,
J = 5.14); 3.70 (t, 4 H,
N(CH2)2, J = 5.14);
7.44 (m, 3 H, Ph);
8.20 (d, 2 H, Ph, J = 7.35);
8.60 (s, 1 H, СН)
a The 1H and 13C NMR spectra of compounds 2a—d,f, 3c, 4a,c,e,f, and 6 were recorded in DMSOꢀd6; those of compounds 4b,d
were run in acetoneꢀd6; those of compound 8, in an acetoneꢀd6—DMSOꢀd6 mixture (1 : 1).
b The 14N NMR spectra of compounds 2b, 2c, and 6 were recorded in DMSOꢀd6: –37.94 (2b); –37.87 (2c); –27.20, –28.70,
–147.50 (6).
c MS (m/z, Irel;(%)) for nitroso compound 3c: 242 [M]+ (1.67), 184 [M – NO – N2]+ (18), 156 (22.8), 145 (71.98), 102 (100),
89 (58.80); for morpholino derivatives 8: 298 [M]+ (1), 270 [M – N2]+ (10), 240 [M – N2 – NO]+ (100).

1920
Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
Batog et al.
were measured in КВr pellets on URꢀ20 and Specord Mꢀ80
spectrometers. The 13C and 1H NMR spectra of the compounds
were recorded on Bruker WMꢀ250 (operating at 62.80 and
250 МHz, respectively) and Bruker AMꢀ300 (operating at
75.5 and 300 МHz, respectively) spectrometers. The 13C and
1H chemical shifts were referred to the DMSOꢀd6 solvent
(δ 39.5; δ 2.5). The 14N NMR spectra were recorded on a
Bruker AMꢀ300 instrument (21.5 МHz) in the δ scale. The
chemical shifts were referred to external МeNO2. Mass spectra
were run on a Varian MAT CH 6 instrument (70 eV). The meltꢀ
ing points were measured on a Boetius hot stage.
(4×20 mL), and the solvent was evaporated to dryness to give
0.26 g (99%) of 3ꢀaminoꢀ4ꢀnitrofurazan (7) identical to an auꢀ
thentic sample in Rf and IR spectrum.6
Nitroso(triazolyl)furazans 3a,b. Na2WO4•2H2O (4.2 g,
13.3 mmol) was added at 11—16 °C to 85% H2O2 (9 mL), and
then conc. H2SO4 (8 mL, 150 mmol) was added dropwise at
5—10 °C. The mixture was cooled to 0 °C and amine 1a or 1b
(1.82 g, 10 mmol) was added. The mixture was stirred for
15—20 min until intensive blue color appeared, cooled to –5 °C,
poured into ice (50 g), extracted with benzene (4×150 mL), and
dried with МgSO4 (10 min). Evaporation of the solvent to dryꢀ
ness gave 1.27 g and 1.17 g of product mixtures, which we were
unable to identify.
C
H
Oxidation of amines 1a—f with peroxide reagents
3ꢀNitrosoꢀ4ꢀ(4ꢀphenylꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxaꢀ
diazole (3c). Na2WO4•2H2O (1.6 g, 5.1 mmol) was added at
11—16 °C to 85% H2O2 (3.6 mL, 144.6 mmol), then conc.
H2SO4 (3.5 mL, 65.6 mmol) was added dropwise at 5—10 °C.
The reaction mixture was cooled to –5 °C, amine 1e (0.6 g,
2.63 mmol) was added, and the mixture was stirred at this temꢀ
perature for 5 min, poured onto ice, and extracted with benzene
(3×30 mL). The extract was washed with water, dried with
МgSO4, and concentrated in vacuo to 1/3 of the initial volume,
and the starting amine (0.05 g) was filtered off. The mother
liquor was passed through a column with L40/100 silica gel (with
benzene as the eluent). Evaporation of the solvent and drying
in vacuo gave compound 3c (greenꢀcolored).
4ꢀ[4ꢀ(4ꢀPhenylꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxadiazolꢀ3ꢀ
yl]morpholine (8). Morpholine (0.2 g, 2.32 mmol) was added to
a solution of compound 2e (0.3 g, 1.16 mmol) (containing a
minor impurity of starting 1e) in benzene (10 mL). The mixture
was stirred for 30 min at room temperature, concentrated in vacuo
to 1/4 its initial volume, and passed through a column with
L40/100 silica gel (elution with benzene). The solvent was evapoꢀ
rated in vacuo, water (10 mL) was added to the oily residue, and
compound 8 was filtered off
Nitro(triazolyl)furazans 2a—e (general procedure). Sodium
tungstate Na2WO4•2H2O (4.8 g, 15.3 mmol) was added with
cooling (10—16 °C) and stirring to 90% H2O2 (10.8 mL,
441 mmol). At 15—20 °C, concentrated H2SO4 (10.5 mL,
394 mmol) was added dropwise and an amine 1a—e (5 mmol)
was added in portions. The reaction mixture acquired an intenꢀ
sive lightꢀblue color. The cooling was removed. Within 1 h after
decoloration, the mixture was poured into 200 mL of ice water.
The products were isolated by method A or B.
A. The 3ꢀ(4ꢀchloromethylꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ4ꢀnitroꢀ
1,2,5ꢀoxadiazole (2d) precipitate was filtered off and dried in air.
The mother liquor was extracted with CH2Cl2 (4×50 mL) and
concentrated to dryness to give an additional amount of comꢀ
pound 2d.
B. The mixture was extracted with CH2Cl2 (4×100 mL); the
combined extracts were dried with MgSO4, and the solvent was
evaporated in vacuo to give 1ꢀ(4ꢀnitroꢀ1,2,5ꢀoxadiazolꢀ3ꢀyl)ꢀ
1Hꢀ1,2,3ꢀtriazolꢀ4ꢀylmethanol (2b) in the crystalline state and
compound 2a,c,e as an oil. The oily product 2a was cooled at a
dryꢀice temperature to hardening, water (3 mL) was added, and
the precipitate was filtered off and dried in air to give 1ꢀ(4ꢀnitroꢀ
1,2,5ꢀoxadiazolꢀ3ꢀyl)ꢀ1Hꢀ1,2,3ꢀtriazolꢀ5ꢀylmethanol (2a). Ether
(3 mL) was added to oily product 2c, the mixture was vigorously
shaken and, after 30 min, 4ꢀhydroxymethylꢀ1ꢀ(4ꢀnitroꢀ1,2,5ꢀ
oxadiazolꢀ3ꢀyl)ꢀ1Hꢀ1,2,3ꢀtriazolꢀ5ꢀylmethanol (2c) was collected
on a filter. Oily product 2e (Rf 0.84, elution with AcOЕt—C6H6,
3 : 1) containing some initial 1e (TLC data) was converted into
the morpholine derivative 8 (see below).
3ꢀNitroꢀ4ꢀ(4ꢀnitroꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxadiazole
(2f). Trifluoroacetic anhydride (9 mL) was slowly added dropwise
at 0 °C to 85% H2O2 (1.1 mL) in MeCN (15 mL), the cooling
was removed, the reaction mixture was warmedꢀup to room
temperature, and amine 1f (1 g, 5.1 mmol) was added. The
mixture was stirred for 3 h at room temperature and for 1 h at
30 °C, poured into ice water (150 mL), and extracted with
CHCl3 (4×50mL). The extract was washed with cold water and
dried with МgSO4, the solvent was evaporated in vacuo to give
compound 2f.
Synthesis of azo derivatives 4a—f from amines 1f—k
4,4´ꢀAzobisꢀ3,3´ꢀ(4ꢀnitroꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ1,2,5ꢀ
oxadiazole (4a). A. Water (45 mL) was added dropwise at room
temperature to a stirred solution of amine 1f (0.3 g, 1.5 mmol) in
concentrated HCl (45 mL). Subsequently, a solution of КМnO4
(3 g, 19 mmol) in water (60 mL) was added over a period of 1 h.
After 4 h, oxalic acid was added until the solution became colorꢀ
less. The precipitate was filtered off, washed with water, and
dried in air to give azo compound 4a.
B. Chlorine was bubbled at 0—2 °C through a solution of
NaOH (0.4 g, 10 mmol) in water (20 mL) to a neutral pH. Then
a solution of amine 1f (0.2 g, 1 mmol) in МeOH (20 mL) was
quickly added, the mixture was stirred for 10 min at 6—8 °C,
AcOEt (5 mL) was added, and the mixture was stirred for
an additional 15 min. The mixture was extracted with benꢀ
zene (4×20 mL), dried with МgSO4, and concentrated in vacuo.
Benzene (10 mL) was added to the oily residue and the mixꢀ
ture was left for 16 h; the precipitated crystals were filtered
off, washed with hexane, and dried in air to give azo comꢀ
pound 4a.
Treatment of amines 1a,b with CF3CO3H. Trifluoroacetic
anhydride (8.4 mL, 60 mmol) was added dropwise at 5—10 °C to
conc. H2O2 (1.58 mL, 64 mmol) in CH2Cl2 (5 mL), and a
mixture of amines 1a,b (0.36 g, 2 mmol) was added. Cooling was
terminated and the reaction mixture was kept for 30 min at
20 °C and poured into ice water (20 mL). The organic phase was
separated from the aqueous one, the aqueous phase was neuꢀ
tralized with NaHCO3 to рH 7 and extracted with CH2Cl2
4,4´ꢀAzobisꢀ3,3´ꢀ(4ꢀcarboxyꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ (4b)
and 4,4´ꢀazobisꢀ3,3´ꢀ(4,5ꢀdimethoxycarbonylꢀ1Hꢀ1,2,3ꢀtriazolꢀ
1ꢀyl)ꢀ1,2,5ꢀoxadiazoles (4d). A (general procedure). Dibromoꢀ

(4ꢀR1ꢀ5ꢀR2ꢀTriazolꢀ1ꢀyl)1,2,5ꢀoxadiazole derivatives Russ.Chem.Bull., Int.Ed., Vol. 54, No. 8, August, 2005
1921
isocyanurate (0.87 g, 3 mmol) was added to a suspension of
amine 1g or 1i (1 mmol) in MeCN (30 mL). After 24 h, the
precipitate was filtered off, the mother liquor was evaporated to
dryness in vacuo, the residue was washed with benzene (50 mL)
(for the extraction of compound 4b) or CH2Cl2 (for the extracꢀ
tion of compound 4d), and the extracts were concentrated
in vacuo to a small volume and passed through a column with
LS5/40 silica gel (elution with benzene) to give azo compound 4b
and 4d, respectively.
B (general procedure). A solution of КМnO4 (1.1 g,
6.9 mmol) in water (36 mL) was added dropwise with stirring to
a suspension of amine 1g or 1i (1 mmol) in 18% HCl (36 mL).
Slight warmingꢀup is observed. After 1 h, oxalic acid was added
until the solution became colorless. The precipitate was filtered
off, washed with water (200 mL) and dried in air to give azo
compound 4b and 4d, identical to the compound prepared by
procedure A in Rf and IR spectra.
4,4´ꢀAzobisꢀ3,3´ꢀ(4ꢀethoxycarbonylꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ
1,2,5ꢀoxadiazole (4c). A solution of Br2 (2.2 mL) in MeCN
(10 mL) and then amine 1h (1.32 g, 6 mmol) were added dropwise
at 15 °C to a suspension of AcONa•3H2O (5.7 g, 42 mmol) in
MeCN (50 mL). After 1 h, the precipitate was filtered off and the
mother liquor was concentrated to dryness. Benzene (150 mL)
was added to the solid residue and the mixture was refluxed for
10 min. Solvent evaporation and drying in vacuo gave azo comꢀ
pound 4c.
4,4´ꢀAzobisꢀ3,3´ꢀ(4ꢀethoxycarbonylꢀ5ꢀmethylꢀ1Hꢀ1,2,3ꢀ
triazolꢀ1ꢀyl)ꢀ1,2,5ꢀoxadiazole (4e). Sodium dichloroisocyanurate
(5.5 g, 25 mmol) was added to a solution of amine 1j (1 g,
4.2 mmol) in 50% AcOH (40 mL), and the mixture was stirred at
room temperature for 1 h and extracted with CHCl3. The exꢀ
tract was washed with water and dried with МgSO4. The solvent
was evaporated to dryness in vacuo. The crystalline product was
washed with a CHCl3—ether mixture, 1 : 1, to give azo comꢀ
pound 4e.
4,4´ꢀAzobisꢀ3,3´ꢀ(4ꢀacetylꢀ5ꢀmethylꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀ
yl)ꢀ1,2,5ꢀoxadiazole (4f). Sodium dichloroisocyanurate (3.6 g,
16 mmol) was added to a solution of amine 1k (0.5 g, 2.4 mmol)
in 50% AcOH (50 mL). The reaction mixture was stirred at
room temperature for 1 h and extracted with AcOЕt, the extract
was washed with water and dried with МgSO4, and the solvent
was evaporated to dryness in vacuo. The crystalline residue was
washed with CCl4 and water to give azo compound 4f.
Treatment of amines 1a,b with oxidants (KMnO4 in HCl;
DBI). A (general procedure). A solution of КМnO4 (1 g,
3.1 mmol) in H2O (36 mL) was added dropwise to a cooled
(15 °C) suspension of the corresponding amine (0.18 g, 1 mmol)
in 18% HCl (36 mL). After 1 h, oxalic acid was added until the
solution became colorless. The precipitate was filtered off,
washed with water, and dried in air to give 0.07 g (39%) and
0.08 g (41%) of compound 9 from amines 1a and 1b, respecꢀ
tively.
B. Dibromoisocyanurate (1.12 g, 4 mmol) was added to
a solution of 1a (0.18 g, 1 mmol) in MeCN (60 mL). After
24 h, the precipitate was filtered off and the solvent was
evaporated to dryness in vacuo to give 0.10 g of a product mixꢀ
ture (containing macrocycle 10, diamine 11 (m/z 384 [M]+ and
388 [М]+, respectively; Rf 0.85 and 0.60, respectively; elution
with C6H6—AcOEt, 5 : 1), and a number of unidentified comꢀ
pounds).
Synthesis of 3ꢀazidoꢀ4ꢀ(4ꢀnitroꢀ1Hꢀ1,2,3ꢀtriazolꢀ1ꢀyl)ꢀ
1,2,5ꢀoxadiazole (6). Amine 1f (1.5 g, 7.6 mmol) was added in
portions at 2 °C to nitrosylsulfuric acid prepared from concenꢀ
trated H2SO4 (6 mL, 113 mmol) and NaNO2 (0.52 g, 7.54 mmol)
by a known procedure.17 Then H3РO4 (d = 1.7 g cm–3) (6 mL,
104 mmol) was added dropwise at 2—7 °C. The mixture was
kept for 2 h at 2 °C. A solution of NaN3 (2.43 g, 37 mmol)
in water (15 mL) was added at 2—7 °C. After gas evoluꢀ
tion had ceased, the reaction mixture was diluted with cold
water (100 mL) and extracted with CH2Cl2 (4×100 mL),
the extract was washed with water (2×50 mL) and dried with
МgSO4, and the solvent was evaporated in vacuo to give 1.5 g
of azide 6 as a thick yellowish oil. Purification on a column with
L40/100 silica gel (elution with CH2Cl2) gave azide 6 as a colorꢀ
less oil.
Treatment of amine 1a with nitrosylsulfuric acid and sodium
azide. Amine 1a (0.18 g, 1 mmol) was added in portions at 2 °C
to stirred nitrosylsulfuric acid prepared from H2SO4 (1 mL) and
NaNO2 (0.07 g, 1 mmol) by a known procedure.17 Orthophosꢀ
phoric acid (1 mL) (d = 1.7 g cm–3) was added at 2—5 °C, the
mixture was kept at this temperature for 1 h, and a solution of
NaN3 (0.32 g, 5 mmol) in H2O (2 mL) was slowly added
dropwise. After gas evolution had ceased, the reaction mixture
was diluted with water (20 mL) and extracted with CH2Cl2
(3×10 mL), the extract was washed with water (3×10 mL) and
dried with МgSO4, and the solvent was evaporated in vacuo to
give 0.03 g (23%) of 3ꢀazidoꢀ4ꢀaminofurazan (12), identical to
an authentic sample in the IR spectrum.15
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Received September 8, 2004;
in revised form November 26, 2004