Selective reduction of the nitro group in the presence of the azoxy group. Synthesis of 2-(alkyl-NNO-azoxy)anilines

Article abstract of DOI:10.1023/A:1015463912286

Tin(II) chloride selectively reduces the aromatic nitro group to the amino group, the azoxy group remaining intact. This allows the preparation of 2-(R-NNO-azoxy)anilines from 2-(R-NNO-azoxy)nitrobenzenes bearing electron-donating or weak electron-withdrawing substituents (Me or Br) in the benzene ring and alkyl substituents at the distal N atom of the azoxy group. The presence of electron-withdrawing substituents at the azoxy group (for example, CO2Et) leads to a change in the direction of the reaction resulting in selective reduction of the azoxy group to the hydrazo group.

Full text of DOI:10.1023/A:1015463912286

Russian Chemical Bulletin, International Edition, Vol. 51, No. 2, pp. 311—318, February, 2002
311
Organic Chemistry
Selective reduction of the nitro group in the presence of the azoxy group.
Synthesis of 2ꢀ(alkylꢀNNOꢀazoxy)anilines

D. L. Lipilin, A. M. Churakov, Yu. A. Strelenko, and V. A. Tartakovsky
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5328. Eꢀmail: churakov@cacr.ioc.ac.ru
Tin(II) chloride selectively reduces the aromatic nitro group to the amino group, the azoxy
group remaining intact. This allows the preparation of 2ꢀ(RꢀNNOꢀazoxy)anilines from
2ꢀ(RꢀNNOꢀazoxy)nitrobenzenes bearing electronꢀdonating or weak electronꢀwithdrawing subꢀ
stituents (Me or Br) in the benzene ring and alkyl substituents at the distal N atom of the azoxy
group. The presence of electronꢀwithdrawing substituents at the azoxy group (for example,
CO2Et) leads to a change in the direction of the reaction resulting in selective reduction of the
azoxy group to the hydrazo group.
Key words: nitrosobenzenes, nitrobenzenes, anilines, azoxy compounds, reduction of the
nitro group.
Anilines containing the RꢀNNOꢀazoxy group in the
ortho position can serve as the starting compounds for the
construction of various heterocyclic skeletons. Thus comꢀ
pounds of the benzoꢀ1,2,3,4ꢀtetrazine series (benzoꢀ
1,2,3,4ꢀtetrazine 1,3ꢀdioxides,1 benzoꢀ1,2,3,4ꢀtetrazine
precursors of anilines. Previously,1,6 we have found that
2ꢀ(tertꢀbutylꢀNNOꢀazoxy)aniline can be synthesized by
selective reduction of the nitro group in 2ꢀ(tertꢀbutylꢀ
NNOꢀazoxy)nitrobenzene with SnCl2. The aim of the
present study was to reveal the scope of the selective reꢀ
duction of the nitro group in the presence of the azoxy
group.
1ꢀoxides,2
2ꢀ(tertꢀbutyl)ꢀ6ꢀoxoꢀ2,6ꢀdihydrobenzoꢀ
1,2,3,4ꢀtetrazine 4ꢀoxides,3 and benzoditetrazine tetroxꢀ
ides4) and 1ꢀhydroxybenzoꢀ1,2,3ꢀtriazole 3ꢀoxides5 were
synthesized from 2ꢀ(tertꢀbutylꢀNNOꢀazoxy)anilines.
Anilines of the aboveꢀmentioned type can be prepared6
from orthoꢀbromoꢀ(tertꢀbutylꢀNNOꢀazoxy)benzenes conꢀ
taining electronꢀwithdrawing substituents in the ring by
nucleophilic replacement of bromine by reaction with
ammonia. However, this procedure is unsuitable for comꢀ
pounds containing electronꢀdonating substituents. In this
case, the corresponding nitro compounds can serve as
Results and Discussion
Synthesis of the starting compounds. The approach to
(azoxy)nitrobenzenes is based on the oxidation of the
corresponding nitroanilines 1 to nitroso compounds 2
followed by the reactions with N,Nꢀdibromoamines acꢀ
cording to the Kovacic method7 (Scheme 1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 295—301, February, 2002.
1066ꢀ5285/02/5102ꢀ311 $27.00 © 2002 Plenum Publishing Corporation

312
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 2, February, 2002
Lipilin et al.
Scheme 1
Compounds 3h—m (Scheme 2) bearing different substituꢀ
ents R at the distal N atom of the azoxy group were
synthesized starting from N,Nꢀdibromoamines, which
were generated in situ from the amine or its salt and
dibromoisocyanuric acid (DBI) as the brominating agent
(cf. lit. data12). It should be noted that 2,4,6ꢀtrichloroꢀ
aniline and 3ꢀaminoꢀ4ꢀmethylfurazan did not give stable
N,Nꢀdibromo derivatives and the mechanism of formaꢀ
tion of the azoxy group in these processes is, conceivably,
different from the mechanism of the Kovacic reaction.
Scheme 2
a
b
c
d
e
f
X1
X2
X3
H
H
H
Br
H
H
Me
H
H
H
Me
H
H
Me
Me
Br
H
Br
3: R = Me (h); Pri (i); 1ꢀAd (j); 2,4,6ꢀCl3C6H2 (k);
4ꢀmethylfurazanꢀ3ꢀyl (l); CO2Et (m)
Reduction of nitro compounds. The nitro and azoxy
groups are generally reduced with the same reagents unꢀ
der similar conditions.13 Reliable data on selective reducꢀ
tion of the nitro group in the presence of the azoxy group
are lacking in the literature. Our attempts to reduce comꢀ
pound 2a using reducing agents usually employed for
the reduction of the nitro group (Fe/HCl, Zn/AcOH,
N2H4/Raney Ni, or H2S) afforded complex mixtures of
products.
We succeeded in performing selective reduction of the
nitro group in orthoꢀ(tertꢀbutylꢀNNOꢀazoxy)nitrobenzenes
3a—e under the action of SnCl2 in the presence of HCl.
The reactions gave rise to the corresponding anilines 4a—e
in 69—95% yields (Scheme 3, Table 1).
Nitrosobenzenes 2a,b were prepared by oxidation of
the corresponding anilines 1a,b with Caro's acid (cf. lit.
data8), compounds 2c,d were obtained by oxidation of
neutralized Caro's acid (cf. lit. data9), and ortho,orthoꢀdiꢀ
substituted nitrosobenzene 2e was synthesized by oxidaꢀ
tion with 30% H2O2 (cf. lit. data10). Oxidation of weakly
basic aniline 1f presented the most substantial difficulties.
Standard methods failed and it was possible to prepare
compound 2f only by oxidation with a calculated amount
of trifluoroperacetic acid.*
Solutions of all the resulting nitroso compounds in
organic solvents were greenꢀcolored. The 1H NMR specꢀ
tra of all these compound, except for 2e, have one set of
signals corresponding to the monomeric forms. In the
spectrum of nitroso compound 2e, signals belonging to
the dimer are observed along with signals corresponding
to the monomer. The amount of the dimer increased as
the temperature was lowered (33% at 297 K and 75%
at 273 K).
Scheme 3
Nitro compounds 3a—g containing different substituꢀ
ents Х in the benzene ring (see Scheme 1) were syntheꢀ
sized from the corresponding nitrosobenzenes 2a—g
and N,Nꢀdibromoꢀtertꢀbutylamine prepared beforehand.
a
b
c
d
e
X1
X2
X3
H
H
H
Br
H
H
Me
H
H
H
Me
H
H
Me
Me
* Trifluoroperacetic acid was first used for oxidation of weakly
basic ortho,orthoꢀdisubstituted anilines to nitroso compounds in
our previous study.11
Substituents in the benzene ring, which are either elecꢀ
tronꢀdonating (Me in compounds 3c—e) or weak elecꢀ

Synthesis of 2ꢀ(alkylꢀNNOꢀazoxy)anilines
Table 1. Reduction of (azoxy)nitrobenzenes 3
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 2, February, 2002
313
amine did not take place. The reasons for high resistance
of the hydroxyamino group in compound 5 to reduction
remain unclear.
Starting
compound
[3]
/mol L–1
t a/h Reaction Yield Purification
product (%) techniqueb
Variations in aliphatic substituents at the distal N atom
of the azoxy group (R = Me, Pri, But, or 1ꢀAd) have
virtually no effect on the yields of amines 4 (Scheme 6,
Table 1). The electronꢀwithdrawing 2,4,6ꢀtrichlorophenyl
group in compound 3k diminishes the yield of the target
amine to 10%, whereas reduction of (azoxy)nitrobenzene
3l (R = 4ꢀmethylfurazanꢀ3ꢀyl) afforded a mixture of prodꢀ
ucts among which the target amine was not detected.
3a
3b
3c
3d
3e
3f
3g
3h
3i
0.35
0.50
0.15
0.15
0.16
0.19
0.19
0.37
0.19
0.16
0.06
0.18
2
3.5
3
3
3
4
2
1
4a
4b
4c
4d
4e
5
4g
4h
4i
69
95
78
90
82
36
93
81
82
90
10
93
A
B, C
A
A
A
B, C
A
B, C
A, D
A
2.5
2.5
4
3j
3k
3m
4j
4k
6
Scheme 6
B, C
c
2
—
a Reaction time.
b See Experimental.
c The product was isolated without additional purification.
tronꢀwithdrawing (Br in compound 3b), have no effect on
the selectivity of reduction. The ortho arrangement of the
nitro and azoxy groups is not essential. Thus only the
nitro group is reduced in compound 3g in which the nitro
group is at the para position with respect to the azoxy
group (Scheme 4).
In the presence of the ethoxycarbonyl substituent at
the distal N atom of the azoxy group, the regioselectivity
of the reaction changes radically: the nitro group remained
intact, while the azoxy group was reduced to the hydrazo
group to form compound 6 (Scheme 7). The physicoꢀ
chemical and spectroscopic characteristics of this comꢀ
pound are identical with those for a sample14 prepared
by the independent synthesis from orthoꢀnitrophenylꢀ
hydrazine and ethyl chloroformate.
Scheme 4
Scheme 7
In the case of reduction of dibromoꢀsubstituted comꢀ
pound 3f, the nitro group was transformed into the
hydroxyamino group after which the process was stopped
(Scheme 5). Under more drastic conditions, hydroxyꢀ
lamine 5 was obtained in lower yield, but reduction to
Scheme 5
14N NMR spectroscopy is a convenient method for
the analysis of the purity of the reaction products and
selectivity of reduction (Table 2) because the signals of
the azoxy and nitro groups are rather narrow and are
clearly seen in the spectra. These signals are located in the
known region and the chemical shifts depend only slightly
on the nature of the substituents (δN for the NO2 and

314
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 2, February, 2002
Lipilin et al.
Table 2. 14N NMR spectra (in acetoneꢀd6) of (azoxy)nitroꢀ
benzenes 3a—m and their reduction products
forded paraꢀbromoꢀsubstituted anilines (for example,
4b → 7b) (see Scheme 8). In these cases, the orthoꢀbromoꢀ
substituted isomer was formed only in trace amounts.
orthoꢀBromination takes place if the para position is subꢀ
stituted (4d,e → 7d,e) (Scheme 9). Under the action of
2 equiv. of the brominating reagent, the ortho,paraꢀdiꢀ
bromo derivatives were obtained (4b,h—j → 8b,h—j) (see
Scheme 8). A mixture of hydrochloric acid and 30% H2O2
is a convenient reagent for chlorination of anilines. Acꢀ
cording to this procedure, dichloroaniline 9a was preꢀ
pared from aniline 4a in a yield higher than 60% (see
Scheme 8).
Starting
comꢀ
pound
δ
(∆ν1/2/Hz)
Prodꢀ
uct
δ
N (∆ν1/2/Hz)
N
N(O)=N
NO2
N(O)=N NH2
3aa
3b
3c
3d
3e
3f
3g
3h
3i
–56 (30) –14 (50)
–58 (40) –17 (50)
–56 (130) –15 (210) 4c –46 (90) –316 (700)
–55 (90) –15 (140) 4d –46 (100) –326 (650)
–56 (130) –15 (150) 4e –48 (150)
–62 (90) –21 (140) –57 (150)
–55 (450) –15 (190) 4g –51 (180)
–52 (70) –14 (90)
–59 (80) –17 (90)
–50 (40) –14 (50)
–50 (90) –16 (80)
–50 (70) –15 (60)
–50 (40) –16 (50)
4aa –48 (100) –323 (800)
4b –49 (130) –319 (1300)
—
—
—
5
4h –43 (90) –321 (500)
4i –50 (130) –319 (600)
4j –47 (160) –322 (850)
4k –41 (180) –324 (750)
Scheme 9
3j
3k
3l
—
6
—
—
—
3m
–9 (110)b
a See lit. data.6
b For the NO2 group.
RN=N(O) groups (R = Ar, Alk, or COOR) range from
–14 to –21 and from –41 to –62, respectively).
2ꢀAzoxyanilines containing the halogen atoms in the
ortho and para positions are more conveniently preꢀ
pared by halogenation of the corresponding anilines 4
(Scheme 8) rather than by reduction of 2ꢀ(azoxy)nitroꢀ
benzenes. Thereby, the range of compounds of this class
can be substantially extended.
X = H (d), Me (e)
Thus, the aromatic nitro group is selectively reduced
to the amino group in the presence of the azoxy group
only if the distal N atom of the latter bears electronꢀ
donating alkyl substituents. In the presence of the elecꢀ
tronꢀwithdrawing substituent, such as CO2Et, the regioꢀ
selectivity of the reaction changes and the azoxy group is
selectively reduced to the hydrazo group. The reactions
involving compounds with aryl or hetaryl substituents
(R = 2,4,6ꢀCl3C6H2 or 4ꢀmethylfurazanꢀ3ꢀyl) produce
mixtures of products. In the latter case, the rate of reducꢀ
tion of the nitro group is apparently comparable to that of
the azoxy group.
Scheme 8
Experimental
The IR spectra were recorded on a Specord Mꢀ80 spectromꢀ
eter. The mass spectra were obtained on a Kratos MSꢀ30 instruꢀ
ment (EI, 70 eV); for the chlorineꢀ and bromineꢀcontaining
fragments, only the peaks for the 35Cl and 79Br isotopes are
1
reported. The H, 13C, 14N, and 15N NMR spectra were meaꢀ
sured on a Bruker AMꢀ300 spectrometer operating at 300.13,
75.5, 21.5, and 30.4 MHz, respectively. The chemical shifts in
the 14N and 15N NMR spectra are given in the δ scale relative to
MeNO2. The course of the reactions was monitored by TLC on
Silufol UVꢀ254 plates; silica gel was used for column chromaꢀ
tography. oꢀNitronitrosobenzene (2a),8 pꢀnitronitrosobenzene
(2g),8 4ꢀmethylꢀ2ꢀnitronitrosobenzene (2c),9 N,Nꢀdibromoꢀtertꢀ
butylamine,15 and 2ꢀ(tertꢀbutylꢀNNOꢀazoxy)nitrobenzene (3a)6
were prepared according to procedures described previously.
4ꢀBromoꢀ2ꢀnitronitrosobenzene (2b). A solution of Caro's
acid, which was prepared from concentrated H2SO4 (7 mL) and
ammonium peroxydisulfate (18.2 g, 0.08 mol) followed by diluꢀ
a
But
H
b
But
Br
h
i
j
R
X
Me
H
Pri
H
Ad
H
Bromination of anilines with 1 equiv. of Br2 in AcOH
in the presence of AcONa or with 1 equiv. of NBS afꢀ

Synthesis of 2ꢀ(alkylꢀNNOꢀazoxy)anilines
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 2, February, 2002
315
tion with water to 50 mL, was added with stirring to a suspension
of 4ꢀbromoꢀ2ꢀnitroaniline (1b) (6.6 g, 30 mmol) in concenꢀ
trated H2SO4 (7.5 mL) and water (1.2 mL). The reaction mixꢀ
ture was stirred at 20 °C for 5 h and then kept for one day
without stirring. The precipitate that formed was filtered off,
thoroughly washed on a filter with water, and dried in air. Comꢀ
pound 2b was obtained in a yield of 1.6 g (23%) as yellow
crystals, m.p. 128—130 °C. Found (%): C, 31.32; H, 1.37;
Br, 34.76; N, 12.01. C6H3BrN2O3. Calculated (%): C, 31.20;
H, 1.31; Br, 34.59; N, 12.13. IR (KBr), ν/cm–1: 1540, 1350
(NO2). 1H NMR (CDCl3), δ: 6.36 (d, 1 H, J = 8.7 Hz); 7.8 (dd,
1 H, J = 8.7 Hz, J = 2.0 Hz); 8.21 (d, 1 H, J = 2.0 Hz).
Found (%): C, 23.20; H, 0.67; Br, 51.98; N, 9.41. C6H2Br2N2O3.
Calculated (%): C, 23.25; H, 0.65; Br, 51.57; N, 9.04. IR (KBr),
1
ν/cm–1: 1540, 1340 (NO2). H NMR (acetoneꢀd6), δ: 8.15 and
8.58 (both br.s, 1 H each). 14N NMR (acetoneꢀd6), δ: –16.9
(NO2, ∆ν = 220 Hz). MS, m/z: 308 [M]+.
1/2
Preparation of azoxy compounds 3b—g by reactions of
nitrosobenzenes 2b—g with N,Nꢀdibromoꢀtertꢀbutylamine (genꢀ
eral procedure). Dibromoꢀtertꢀbutylamine ButNBr2 (1.28 g,
5.25 mmol) was added with stirring to a solution of a nitroso
compound (5 mmol) in CH2Cl2 (220 mL). The reaction mixture
was kept for ∼16 h and then the solvent was evaporated. The
products were purified by column chromatography when needed.
1ꢀ(4ꢀBromoꢀ2ꢀnitrophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide
(3b). M.p. 57—59 °C. Found (%): C, 39.57; H, 4.11; Br, 26.57;
N, 13.82. C10H12BrN3O3. Calculated (%): C, 39.75; H, 4.00;
Br, 26.45; N, 13.91. IR (KBr), ν/cm–1: 1540, 1350 (NO2); 1490
14N NMR (CDCl3), δ: –17.2 (NO2, ∆ν
= 80 Hz). MS,
1/2
m/z: 230 [M]+.
5ꢀMethylꢀ2ꢀnitronitrosobenzene (2d). A neutralized solution
of Caro's acid, which was prepared from concentrated H2SO4
(16 mL) and ammonium peroxydisulfate (22 g, 0.1 mol) folꢀ
lowed by dilution to 300 mL and neutralization with a concenꢀ
trated ammonia to pH 6, was added with stirring to a solution of
5ꢀmethylꢀ2ꢀnitroaniline (1d) (2.28 g, 15 mmol) in dioxane
(25 mL). The reaction mixture was kept at 20 °C for two days.
The precipitate that formed was filtered off, washed on a filter
with water, and recrystallized from C6H6. Compound 2d was
obtained in a yield of 0.7 g (28%) as paleꢀyellow crystals, m.p.
138—140 °C (with decomp.). Found (%): C, 50.22; H, 3.41;
N, 16.98. C7H6N2O3. Calculated (%): C, 50.61; H, 3.64;
1
(N(O)=N). H NMR (acetoneꢀd6), δ: 1.41 (s, 9 H); 7.88 (d,
1 H, J = 8.8 Hz); 8.09 (dd, 1 H, J = 8.8 Hz, J = 2.2 Hz); 8.26 (d,
1 H, J = 2.2 Hz). 13C NMR (acetoneꢀd6), δ: 25.4, 60.8, 124.5,
127.8, 128.5, 137.6. MS, m/z: 301 [M]+.
2ꢀ(tertꢀButyl)ꢀ1ꢀ(4ꢀmethylꢀ2ꢀnitrophenyl)diazene 1ꢀoxide
(3c). M.p. 35—38 °C. Found (%): C, 55.84; H, 6.35; N, 18.36.
C11H15N3O3. Calculated (%): C, 55.69; H, 6.37; N, 17.71.
IR (thin layer), ν/cm–1: 1540, 1360 (NO2); 1490 (N(O)=N).
1H NMR (acetoneꢀd6), δ: 1.45 (s, 9 H); 2.61 (s, 3 H); 7.5 (d,
1 H, J = 8.1 Hz); 7.62 (dd, 1 H, J = 8.1 Hz, J = 2.2 Hz); 7.68 (d,
1 H, J = 2.2 Hz). 13C NMR (acetoneꢀd6), δ: 21.4, 25.8, 61.0,
125.7, 125.9, 134.8, 141.4. MS, m/z: 237 [M]+.
2ꢀ(tertꢀButyl)ꢀ1ꢀ(5ꢀmethylꢀ2ꢀnitrophenyl)diazene 1ꢀoxide
(3d). Yellow oil. Found (%): C, 55.60; H, 6.32; N, 17.83.
C11H15N3O3. Calculated (%): C, 55.69; H, 6.37; N, 17.71.
IR (thin layer), ν/cm–1: 1540, 1360 (NO2); 1480 (N(O)=N).
1H NMR (acetoneꢀd6), δ: 1.45 (s, 9 H); 2.47 (s, 3 H); 7.59 (dd,
1 H, J = 8.3 Hz, J = 2.1 Hz); 7.66 (d, 1 H, J = 2.1 Hz); 7.96 (d,
1 H, J = 8.3 Hz). MS, m/z: 237 [M]+.
2ꢀ(tertꢀButyl)ꢀ1ꢀ(2,3ꢀdimethylꢀ6ꢀnitrophenyl)diazene 1ꢀoxide
(3e). M.p. 64—66 °C. Found (%): C, 57.35; H, 6.85; N, 16.93.
C12H17N3O3. Calculated (%): C, 57.36; H, 6.82; N, 16.72.
IR (KBr), ν/cm–1: 1530, 1340 (NO2); 1500 (N(O)=N). 1H NMR
(acetoneꢀd6), δ: 1.46 (s, 9 H); 2.25 and 2.46 (both s, 3 H each);
7.53 (d, 1 H, J = 8.8 Hz). 13C NMR (acetoneꢀd6), δ: 13.8, 20.7,
25.6, 60.7, 123.2, 123.9, 131.1, 132.7, 140.8, 147.2. MS,
m/z: 251 [M]+.
1
N, 16.86. IR (KBr), ν/cm–1: 1520, 1350 (NO2). H NMR (acꢀ
etoneꢀd6), δ: 2.26 (s, 3 H); 6.45 (d, 1 H, J = 1.2 Hz); 7.88 (dd,
1 H, J = 8.5 Hz, J = 1.2 Hz); 8.17 (d, 1 H, J = 8.5 Hz).
13C NMR (acetoneꢀd6), δ: 21.3, 111.7, 125.2, 127.4, 133.9,
137.1, 146.3. 14N NMR (acetoneꢀd6), δ: –8.5 (NO2, ∆ν
140 Hz). MS, m/z: 166 [M]+.
=
1/2
2,3ꢀDimethylꢀ6ꢀnitronitrosobenzene (2e). A 30% aqueous soꢀ
lution of H2O2 (8 mL) was added with stirring to a solution of
2,3ꢀdimethylꢀ6ꢀnitroaniline (1e) (1.66 g, 10 mmol) in AcOH
(40 mL) and H2SO4 (2 mL) and then the reaction mixture was
stirred at 20 °C for 12 h. The product that precipitated was
filtered off, washed on a filter with water, and dried in air.
Compound 2e was obtained in a yield of 0.67 g (38%) as lemonꢀ
yellow crystals, m.p. 144—146 °C. Found (%): C, 53.46; H, 4.32;
N, 15.81. C8H8N2O3. Calculated (%): C, 53.33; H, 4.48;
N, 15.55. IR (KBr), ν/cm–1: 1530, 1360 (NO2). In the 1H NMR
spectrum (acetoneꢀd6), the monomer 2e : dimer 2e ratios were
2 : 1 and 1 : 3 at 25 and 0 °C, respectively. 1H NMR of monomer
2e (acetoneꢀd6, 25 °C), δ: 2.71 and 2.88 (both s, 3 H each); 7.50
2ꢀ(tertꢀButyl)ꢀ1ꢀ(2,4ꢀdibromoꢀ6ꢀnitrophenyl)diazene 1ꢀoxide
(3f). M.p. 77—79 °C. Found (%): C, 31.66; H, 2.92; Br, 42.51;
N, 10.84. C10H11Br2N3O3. Calculated (%): C, 31.52; H, 2.91;
Br, 41.94; N, 11.03. IR (KBr), ν/cm–1: 1520, 1370 (NO2); 1500
1
and 7.78 (both d, 1 H each, J = 8.1 Hz). H NMR of dimer 2e
(acetoneꢀd6, 0 °C), δ: 2.44 and 2.52 (both s, 3 H each); 7.70 and
8.02 (both d, 1 H each, J = 8.1 Hz). 14N NMR of monomer 2e
(acetoneꢀd6, 25 °C), δ: –8.8 (NO2, ∆ν1/2 = 60 Hz). 14N NMR of
1
(N(O)=N). H NMR (acetoneꢀd6), δ: 1.48 (s, 9 H); 8.42 and
8.57 (both d, 1 H each, J = 2.2 Hz). 13C NMR (acetoneꢀd6), δ:
25.6, 61.9, 116.9, 119.3, 128.7, 142.2. MS, m/z: 379 [M]+.
2ꢀ(tertꢀButyl)ꢀ1ꢀ(4ꢀnitrophenyl)diazene 1ꢀoxide (3g). M.p.
97—99 °C. Found (%): C, 53.62; H, 5.82; N, 18.91. C10H13N3O3.
dimer 2e (acetoneꢀd6, 0 °C), δ: –12.4 (NO2, ∆ν = 220 Hz).
1/2
MS, m/z: 180 [M]+.
2,4ꢀDibromoꢀ6ꢀnitronitrosobenzene (2f). Trifluoroacetic anꢀ
hydride (CF3CO)2O (0.71 mL, 3.5 mmol) was added to a stirred
mixture of CH2Cl2 (5 mL) and 80% aqueous H2O2 (0.15 mL) at
0 °C. The reaction mixture was kept for 10 min and then slowly
added with stirring to a solution of 2,4ꢀdibromoꢀ6ꢀnitroaniline
(1f) (0.5 g, 1.7 mmol) in CH2Cl2 (10 mL) at 20 °C. Then the
reaction mixture was stirred for 2 h and washed with a solution
of NaHCO3 (2×10 mL). The organic layer was dried with MgSO4
and the solvent was evaporated. Compound 2f was obtained in a
yield of 0.5 g (95%) as brightꢀyellow crystals, m.p. 72—74 °C.
Calculated (%): C, 53.80; H, 5.87; N, 18.82. IR (KBr), ν/cm–1
1530, 1340 (NO2); 1480 (N(O)=N). H NMR (acetoneꢀd6), δ:
1.49 (s, 9 H); 8.38 (m, 4 H). 13C NMR (acetoneꢀd6), δ: 25.7,
60.0, 124.4, 125.2, 125.9, 150.4. MS, m/z: 223 [M]+.
:
1
Preparation of azoxy compounds 3h—m by reactions of
oꢀnitronitrosobenzene (2a) with amines and DBI (general proceꢀ
dure). Amine (in the case of 3j—m) or its salt (in the case of
3h—i) (3 mmol) and DBI (0.9 g, 3.3 mmol) were added with
stirring to a solution of oꢀnitronitrosobenzene (2a) (0.41 g,

316
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 2, February, 2002
Lipilin et al.
2.7 mmol) in MeCN (20 mL) and then the reaction mixture was
stirred at 20 °C for 5 h (3h,j,m) or 10 h (3i,k,l). The precipitate
of cyanuric acid was filtered off, the filtrate was concentrated to
dryness, and the product was extracted from the solid residue
with CH2Cl2 or light petroleum. Azoxy compounds 3h—m were
purified by column chromatography on silica gel when needed.
2ꢀMethylꢀ1ꢀ(2ꢀnitrophenyl)diazene 1ꢀoxide (3h). Redꢀorange
oil. Found (%): C, 46.35; H, 3.85; N, 22.86. C7H7N3O3. Calcuꢀ
lated (%): C, 46.41; H, 3.89; N, 23.20. IR (KBr), ν/cm–1: 1540,
vent was evaporated. In some cases, the products were purified
by chromatography on silica gel (CHCl3 (C) or C6H6 (D) as the
eluent).
1ꢀ(2ꢀAminophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide (4a) was
identical with the authentic sample, m.p. 30—32 °C (lit. data2:
m.p. 30—31 °C).
1ꢀ(2ꢀAminoꢀ4ꢀbromophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide
(4b) was identical with the authentic sample, m.p. 81—83 °C
(lit. data2: m.p. 81.5—82 °C).
1ꢀ(2ꢀAminoꢀ4ꢀmethylphenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide
(4c). Orangeꢀyellow oil. Found (%): C, 63.78; H, 8.25; N, 20.39.
C11H17N3O. Calculated (%): C, 63.74; H, 8.27; N, 20.27.
IR (KBr), ν/cm–1: 1480 (N(O)=N); 3340, 3460 (NH2).
1H NMR (acetoneꢀd6), δ: 1.45 (s, 9 H); 2.24 (s, 3 H); 6.3 (br.s,
2 H); 6.45 (dd, 1 H, J = 8.8 Hz, J = 1.7 Hz); 6.71 (d, 1 H, J =
1.7 Hz); 7.82 (d, 1 H, J = 8.8 Hz). 13C NMR (acetoneꢀd6),
δ: 21.2, 26.3, 59.2, 117.5, 118.6, 125.1, 133.2, 142.7. MS,
m/z: 207 [M]+.
1
1350 (NO2); 1500 (N(O)=N). H NMR (acetoneꢀd6), δ: 3.38
(s, 3 H); 7.83 (m, 1 H); 7.91 (m, 2 H); 8.07 (m, 1 H). MS,
m/z: 181 [M]+.
2ꢀIsopropylꢀ1ꢀ(2ꢀnitrophenyl)diazene 1ꢀoxide (3i). Orangeꢀ
yellow oil. Found (%): C, 51.62; H, 5.35; N, 20.86. C9H11N3O3.
Calculated (%): C, 51.67; H, 5.30; N, 20.09. IR (thin layer),
ν/cm–1: 1540, 1350 (NO2); 1480 (N(O)=N). 1H NMR (acꢀ
etoneꢀd6), δ: 1.26 (d, 6 H, J = 5.9 Hz); 4.26 (sept, 1 H, J =
5.9 Hz); 7.86 (m, 2 H); 8.04 (m, 2 H). 13C NMR (acetoneꢀd6),
δ: 19.3, 53.1, 127.9, 128.6, 134.5, 137.6, 141.5, 144.6. MS,
m/z: 209 [M]+.
2ꢀ(Adamantanꢀ1ꢀyl)ꢀ1ꢀ(2ꢀnitrophenyl)diazene 1ꢀoxide (3j).
M.p. 163—166 °C. Found (%): C, 64.21; H, 6.35; N, 13.61.
C16H19N3O3. Calculated (%): C, 63.77; H, 6.36; N, 13.94.
IR (KBr), ν/cm–1: 1540, 1350 (NO2); 1490 (N(O)=N). 1H NMR
(acetoneꢀd6), δ: 1.76 (m, 6 H); 2.12 (m, 3 H); 2.18 (m, 6 H);
7.76 (m, 1 H); 7.85 (m, 2 H); 8.04 (m, 1 H). 13C NMR (acꢀ
etoneꢀd6), δ: 30.1, 36.2, 37.9, 62.0, 125.7, 126.1, 132.0, 134.7.
MS, m/z: 301 [M]+.
2ꢀEthoxycarbonylꢀ1ꢀ(2ꢀnitrophenyl)diazene 1ꢀoxide (3k).
M.p. 117—119 °C. Found (%): C, 45.60; H, 3.75; N, 17.87.
C9H9N3O5. Calculated (%): C, 45.19; H, 3.79; N, 17.57.
IR (KBr), ν/cm–1: 1540, 1340 (NO2); 1510 (N(O)=N); 1680
(C=O). 1H NMR (acetoneꢀd6), δ: 1.38 (t, 3 H, J = 7.4 Hz); 4.44
(q, 2 H, J = 7.4 Hz); 7.95 (m, 2 H); 8.07 (m, 1 H); 8.16 (m,
1 H). 13C NMR (acetoneꢀd6), δ: 14.4, 65.4, 126.4, 134.2, 135.2,
141.2, 143.8, 156.9. MS, m/z: 239 [M]+.
1ꢀ(2ꢀAminoꢀ5ꢀmethylphenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide
(4d). M.p. 78—80 °C. Found (%): C, 63.56; H, 8.21; N, 20.30.
C11H17N3O. Calculated (%): C, 63.74; H, 8.27; N, 20.27.
IR (thin layer), ν/cm–1: 1470 (N(O)=N); 3350, 3460 (NH2).
1H NMR (acetoneꢀd6), δ: 1.46 (s, 9 H); 2.23 (s, 3 H); 6.10 (br.s,
2 H); 6.81 (d, 1 H, J = 8.5 Hz); 7.02 (dd, 1 H, J = 8.5 Hz, J =
1.7 Hz); 7.69 (d, 1 H, J = 1.7 Hz). MS, m/z: 207 [M]+.
1ꢀ(2ꢀAminoꢀ5,6ꢀdimethylphenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxꢀ
ide (4e). M.p. 100—102 °C. Found (%): C, 65.28; H, 8.75;
N, 18.41. C12H19N3O. Calculated (%): C, 65.13; H, 8.65;
N, 18.99. IR (KBr), ν/cm–1: 1480 (N(O)=N); 3340, 3430
1
(NH2). H NMR (DMSOꢀd6), δ: 1.44 (s, 9 H); 2.00 (s, 3 H);
2.13 (s, 1 H); 4.60 (br.s, 2 H); 6.61 and 6.82 (both d, 1 H each,
J = 8.1 Hz). 13C NMR (DMSOꢀd6), δ: 13.3, 18.7, 25.4, 59.0,
113.9, 124.5, 128.0, 130.0, 136.7, 137.8. MS, m/z: 221 [M]+.
1ꢀ(4ꢀAminophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxide (4g).
M.p. 141—143 °C. Found (%): C, 62.07; H, 7.85; N, 21.33.
C10H15N3O. Calculated (%): C, 62.15; H, 7.82; N, 21.74. IRꢀ
1
1ꢀ(2ꢀNitrophenyl)ꢀ2ꢀ(2,4,6ꢀtrichlorophenyl)diazene 1ꢀoxide
(3l). M.p. 123—125 °C. Found (%): C, 41.67; H, 1.72; Cl, 31.23;
N, 12.26. C12H6Cl3N3O3. Calculated (%): C, 41.59; H, 1.72;
Cl, 30.69; N, 12.13. IR (KBr), ν/cm–1: 1540, 1340 (NO2); 1470
(KBr), ν/cm–1: 1460 (N(O)=N); 3350, 3440 (NH2). H NMR
(acetoneꢀd6), δ: 1.49 (s, 9 H); 6.2 (br.s, 2 H); 6.66 (d, 1 H, J =
8.1 Hz); 7.85 (d, 1 H, J = 8.8 Hz). 13C NMR (acetoneꢀd6),
δ: 21.2, 26.3, 59.2, 117.5, 118.6, 125.1, 133.2, 142.7. MS,
m/z: 193 [M]+.
1ꢀ(2ꢀAminophenyl)ꢀ2ꢀmethyldiazene 1ꢀoxide (4h). Yellowꢀ
brown oil. Found (%): C, 55.79; H, 6.09; N, 27.57. C7H9N3O.
1
(N(O)=N). H NMR (acetoneꢀd6), δ: 7.68 (s, 2 H); 8.01 and
8.21 (both m, 2 H each). 13C NMR (acetoneꢀd6), δ: 126.4,
126.9, 129.5, 129.7, 134.1, 134.5, 135.0, 138.8, 141.5, 144.1.
MS, m/z: 345 [M]+.
Calculated (%): C, 55.62; H, 6.00; N, 27.80. IR (KBr), ν/cm–1
:
1
2ꢀ(4ꢀMethylfurazanꢀ3ꢀyl)ꢀ1ꢀ(2ꢀnitrophenyl)diazene 1ꢀoxide
(3m). M.p. 58—60 °C. Found (%): C, 43.61; H, 2.85; N, 28.56.
C9H7N5O4. Calculated (%): C, 43.38; H, 2.83; N, 28.11.
IR (KBr), ν/cm–1: 1540, 1360 (NO2); 1490 (N(O)=N). 1H NMR
(acetoneꢀd6), δ: 2.46 (s, 3 H); 8.04 and 8.24 (both m, 2 H each).
13C NMR (acetoneꢀd6), δ: 8.6, 126.4, 126.9, 134.3, 135.3, 142.1,
144.1, 150.2, 155.9. MS, m/z: 249 [M]+.
Reduction of nitrobenzenes 3a—m with SnCl2 (general proceꢀ
dure). A solution of SnCl2•2 H2O (7 mmol) in concentrated
HCl (6.3 mL) was added with stirring to a solution of nitro
compounds 3a—m (2 mmol) in EtOH, whereupon the reaction
mixture slightly warmed up. Then the mixture was stirred at
20 °C until the starting compound disappeared completely (see
Table 1) and poured into water (a tenfold excess with respect to
EtOH). The solution was alkalified to рH 7—8 and extracted
with AcOEt (A) or extracted from an acidic solution (B). The
extract was washed with brine and dried with MgSO4. The solꢀ
1470 (N(O)=N); 3320, 3410 (NH2). H NMR (acetoneꢀd6), δ:
3.40 (s, 3 H); 6.30 (br.s, 2 H); 6.64 (t, 1 H, J = 8.2 Hz); 6.93 (d,
1 H, J = 8.2 Hz); 7.21 (t, 1 H, J = 8.2 Hz); 7.96 (d, 1 H, J =
8.2 Hz). 13C NMR (acetoneꢀd6), δ: 39.6, 116.4, 118.8, 125.2,
132.6, 143.5. MS, m/z: 151 [M]+.
1ꢀ(2ꢀAminophenyl)ꢀ2ꢀisopropyldiazene 1ꢀoxide (4i). Orangeꢀ
yellow oil. Found (%): C, 60.59; H, 7.13; N, 23.56. C9H13N3O.
Calculated (%): C, 60.32; H, 7.31; N, 23.45. IR (thin layer),
ν/cm–1: 1500 (N(O)=N); 3350, 3470 (NH2). 1H NMR (acꢀ
etoneꢀd6), δ: 1.26 (d, 6 H, J = 6.6 Hz); 4.35 (sept, 1 H, J =
6.6 Hz); 6.40 (br.s, 2 H); 6.67 (dt, 1 H, J = 8.1 Hz, J = 1.5 Hz);
6.93 (dd, 1 H, J = 8.1 Hz, J = 1.5 Hz); 7.21 (dt, 1 H, J = 8.1 Hz,
J = 1.5 Hz); 7.92 (dd, 1 H, J = 8.1 Hz, J = 1.5 Hz). MS,
m/z: 179 [M]+.
2ꢀ(Adamantanꢀ1ꢀyl)ꢀ1ꢀ(2ꢀaminophenyl)diazene 1ꢀoxide (4j).
M.p. 122—124 °C. Found (%): C, 71.03; H, 7.51; N, 15.08.
C16H21N3O. Calculated (%): C, 70.82; H, 7.80; N, 15.49.

Synthesis of 2ꢀ(alkylꢀNNOꢀazoxy)anilines
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 2, February, 2002
317
IR (KBr), ν/cm–1: 1490 (N(O)=N); 3340, 3490 (NH2).
1H NMR (acetoneꢀd6), δ: 1.80 (m, 6 H); 2.22 (m, 3 H); 2.24
(m, 6 H); 6.30 (br.s, 2 H); 6.62 (dt, 1 H, J = 8.2 Hz, J = 1.5 Hz);
6.90 (dd, 1 H, J = 8.2 Hz, J = 1.5 Hz); 7.18 (dt, 1 H, J = 8.2 Hz,
J = 1.5 Hz); 7.92 (dd, 1 H, J = 8.2 Hz, J = 1.5 Hz). 13C NMR
(acetoneꢀd6), δ: 30.2, 37.5, 38.5, 60.8, 116.3, 118.7, 125.2, 132.3.
MS, m/z: 271 [M]+.
1ꢀ(2ꢀAminoꢀ3ꢀbromoꢀ5,6ꢀdimethylphenyl)ꢀ2ꢀ(tertꢀbutyl)diꢀ
azene 1ꢀoxide (7e). NꢀBromosuccinimide (21 mg, 0.13 mmol)
was added with stirring to a solution of aniline 4e (24 mg,
0.109 mmol) in MeCN (2 mL). The reaction mixture was stirred
at 20 °C for 1.5 h, the solvent was evaporated, the product was
extracted from the solid residue with hot light petroleum
(4×5 mL), and the solvent was evaporated. Amine 7e was obꢀ
tained in a yield of 31 mg (94%), m.p. 148—150 °C. Found (%):
C, 48.16; H, 5.99; Br, 26.71; N, 13.91. C12H18BrN3O. Calcuꢀ
lated (%): C, 48.01; H, 6.04; Br, 26.62; N, 14.00. IR (KBr),
ν/cm–1: 1490 (N(O)=N); 3340, 3420 (NH2). 1H NMR (acꢀ
etoneꢀd6), δ: 1.46 (s, 9 H); 2.04 and 2.14 (both s, 3 H each); 4.50
(br.s, 2 H); 7.26 (s, 1 H). 13C NMR (acetoneꢀd6), δ: 14.0, 18.9,
25.9, 60.4, 107.2, 128.2, 129.7, 133.7, 136.7. 14N NMR (acꢀ
etoneꢀd6), δ: –49.8 (∆ν1/2 = 110 Hz). MS, m/z: 298 [M]+.
1ꢀ(2ꢀAminoꢀ3,4,5ꢀtribromophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene
1ꢀoxide (8b). NꢀBromosuccinimide (1.1 g, 6.1 mmol) was added
with stirring to a solution of aniline 4b (0.8 g, 3 mmol) in CH2Cl2
(30 mL). The reaction mixture was stirred at 20 °C for 5 h and
then kept without stirring for ∼16 h. The solution was concenꢀ
trated to dryness, the product was extracted from the solid resiꢀ
due with hot light petroleum (3×50 mL), and the solvent was
evaporated. Amine 8b was obtained in a yield of 1.22 g (95%),
m.p. 105—106 °C. Found (%): C, 27.86; H, 2.76; Br, 55.82;
N, 9.61. C10H12Br3N3O. Calculated (%): C, 27.94; H, 2.81;
Br, 55.76; N, 9.77. IR (KBr), ν/cm–1: 1470 (N(O)=N); 3290,
3470 (NH2). 1H NMR (acetoneꢀd6), δ: 1.48 (s, 9 H); 6.90 (br.s,
2 H); 8.29 (s, 1 H). 13C NMR (acetoneꢀd6), δ: 26.0, 60.4, 109.0,
114.8, 128.6, 131.5, 133.4 (br), 141.6. 14N NMR (acetoneꢀd6),
1ꢀ(2ꢀAminophenyl)ꢀ2ꢀ(2,4,6ꢀtrichlorophenyl)diazene 1ꢀoxide
(4k). M.p. 127—129 °C. Found (%): C, 45.86; H, 2.52; Cl, 33.78;
N, 13.41. C12H8Cl3N3O. Calculated (%): C, 45.53; H, 2.55;
Cl, 33.60; N, 13.27. IR (KBr), ν/cm–1: 1500 (N(O)=N); 3370,
1
3490 (NH2). H NMR (acetoneꢀd6), δ: 5.30 (br.s, 2 H); 6.71
(t, 1 H, J = 8.1 Hz); 7.06 (d, 1 H, J = 8.8 Hz); 7.26 (s, 2 H);
7.35 (t, 1 H, J = 8.1 Hz); 8.10 (d, 1 H, J = 8.8 Hz). MS,
m/z: 315 [M]+.
2ꢀ(tertꢀButyl)ꢀ1ꢀ(4,6ꢀdibromoꢀ2ꢀhydroxyaminophenyl)diꢀ
azene 1ꢀoxide (5). M.p. 128—130 °C. Found (%): C, 32.34;
H, 3.55; Br, 43.37; N, 14.31. C10H13Br2N3O2. Calculated (%):
C, 32.72; H, 3.57; Br, 43.54; N, 14.45. IR (KBr), ν/cm–1: 1480
(N(O)=N); 3380, 3420 (NHOH). 1H NMR (acetoneꢀd6), δ:
1.46 (s, 9 H); 7.32 and 7.53 (both d, 1 H each, J = 2.2 Hz); 7.80
(br.s, 1 H); 8.20 (br.s, 1 H). MS, m/z: 365 [M]+.
Ethyl 2ꢀ(2ꢀnitrophenyl)hydrazinecarboxylate (6). M.p.
72—74 °C. IR (KBr), ν/cm–1: 1530, 1340 (NO2); 1700 (C=O);
3290 (NHNH). 1H NMR (acetoneꢀd6), δ: 1.21 (t, 3 H, J =
6.6 Hz); 4.14 (q, 2 H, J = 6.6 Hz); 6.90 (t, 1 H, J = 8.1 Hz); 7.28
(d, 1 H, J = 8.8 Hz); 7.59 (t, 1 H, J = 8.1 Hz); 8.13 (d, 1 H, J =
8.8 Hz); 8.50 and 9.10 (both br.s, 1 H each). 13C NMR (acꢀ
etoneꢀd6), δ: 14.9, 62.1, 115.5, 118.9, 126.7, 137.0, 146.9, 157.3.
MS, m/z: 225 [M]+.
δ: –51.3 (∆ν = 130 Hz). MS, m/z: 425 [M]+.
1/2
1ꢀ(2ꢀAminoꢀ4,5ꢀdibromophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxꢀ
ide (7b). NꢀBromosuccinimide (0.2 g, 1.1 mmol) was added with
stirring to a solution of aniline 4b (0.3 g, 1.125 mmol) in CH2Cl2
(20 mL). The reaction mixture was stirred at 20 °C for 30 min,
the solvent was evaporated, the product was extracted from the
solid residue with light petroleum (hereinafter, 40—70 °C,
3×20 mL), and the solvent was evaporated. Amine 7b was obꢀ
tained in a yield of 0.302 g (77%), m.p. 102—104 °C (from
hexane). Found (%): C, 34.36; H, 3.72; Br, 45.58; N, 11.76.
C10H13Br2N3O. Calculated (%): C, 34.21; H, 3.73; Br, 45.52;
N, 11.97. IR (KBr), ν/cm–1: 1470 (N(O)=N); 3310, 3430 (NH2).
1H NMR (acetoneꢀd6), δ: 1.44 (s, 9 H); 6.57 (br.s, 2 H); 7.28
and 8.19 (both s, 1 H each). 13C NMR (acetoneꢀd6), δ: 26.0,
59.7, 108.4, 122.5, 127.9, 129.2, 132.7 (br), 143.8. 14N NMR
1ꢀ(2ꢀAminoꢀ3,5ꢀdibromophenyl)ꢀ2ꢀmethyldiazene 1ꢀoxide
(8h). Sodium acetate (1.83 g, 22.6 mmol) was added with stirꢀ
ring to a solution of aniline 4h (1.64 g, 10.9 mmol) in glacial
AcOH (11 mL) and then a solution of Br2 (3.5 g, 21.8 mmol) in
AcOH (5.5 mL) was added over 5 min. The reaction mixture
was stirred for 5 min, poured into water (100 mL), and extracted
with hexane (4×50 mL). The solvent was evaporated and the
product was purified by column chromatography (CHCl3 as the
eluent). Amine 8h was obtained in a yield of 1.52 g (45%), m.p.
63—65 °C. Found (%): C, 27.26; H, 2.32; Br, 51.58; N, 13.46.
C7H7Br2N3O. Calculated (%): C, 27.21; H, 2.28; Br, 51.72; N,
13.60. IR (KBr), ν/cm–1: 1470 (N(O)=N); 3350, 3440 (NH2).
1H NMR (acetoneꢀd6), δ: 3.43 (s, 3 H); 6.61 (br.s, 2 H); 7.74
and 8.09 (both d, 1 H each, J = 2.3 Hz). 13C NMR (acetoneꢀd6),
δ: 40.0, 106.2, 112.1, 127.6, 134.6 (br), 137.9, 140.5. 14N NMR
(acetoneꢀd6), δ: –50.9 (∆ν
= 130 Hz); –318 (br). MS,
1/2
m/z: 349 [M]+.
(acetoneꢀd6), δ: –47.9 (∆ν
= 80 Hz); –314 (br). MS,
1/2
1ꢀ(2ꢀAminoꢀ3ꢀbromoꢀ5ꢀmethylphenyl)ꢀ2ꢀ(tertꢀbutyl)diazene
1ꢀoxide (7d). NꢀBromosuccinimide (0.34 g, 1.9 mmol) was added
with stirring to a solution of aniline 4d (0.36 g, 1.74 mmol) in
MeCN (7.2 mL). The reaction mixture was stirred at 20 °C for
1 h. Then the solvent was evaporated, the product was extracted
from the solid residue with hot light petroleum (3×25 mL), and
the solvent was evaporated. Amine 7d was obtained in a yield of
0.45 g (91%), m.p. 125—127 °C. Found (%): C, 46.11; H, 5.57;
Br, 27.84; N, 14.49. C11H16BrN3O. Calculated (%): C, 46.17;
H, 5.64; Br, 27.92; N, 14.68. IR (KBr), ν/cm–1: 1500 (N(O)=N);
3330, 3470 (NH2). 1H NMR (acetoneꢀd6), δ: 1.49 (s, 9 H); 2.22
(s, 3 H); 6.00 (br.s, 2 H); 7.34 and 7.73 (both d, 1 H each, J =
1.5 Hz). 13C NMR (acetoneꢀd6), δ: 20.4, 26.5, 59.9, 111.5,
125.3, 126.6, 136.3, 138.4. 14N NMR (acetoneꢀd6), δ: –49.1
(∆ν1/2 = 200 Hz). MS, m/z: 285 [M]+.
m/z: 307 [M]+.
1ꢀ(2ꢀAminoꢀ3,5ꢀdibromophenyl)ꢀ2ꢀisopropyldiazene 1ꢀoxide
(8i). NꢀBromosuccinimide (0.89 g, 5 mmol) was added with
stirring to a solution of aniline 4i (0.43 g, 2.275 mmol) in MeCN
(9.5 mL) and then the reaction mixture was stirred at 20 °C for
5 h. The precipitate of succinimide was filtered off and washed
on a filter with a small amount of CH2Cl2. The filtrate was
concentrated, the product was extracted from the residue with
hot light petroleum, and the extract was passed through a
short column with silica gel (CHCl3 as the eluent). Amine 8i
was obtained in a yield of 0.73 g (92%) as an orangeꢀyelꢀ
low oil. Found (%): C, 32.18; H, 3.24; Br, 47.96; N, 12.32.
C9H11Br2N3O. Calculated (%): C, 32.07; H, 3.29; Br, 47.42;
N, 12.47. IR (KBr), ν/cm–1: 1480 (N(O)=N); 3350, 3470
(NH2). 1H NMR (acetoneꢀd6), δ: 1.29 (d, 6 H, J = 7.4 Hz); 4.37

318
Russ.Chem.Bull., Int.Ed., Vol. 51, No. 2, February, 2002
Lipilin et al.
(sept, 1 H, J = 7.4 Hz); 6.63 (br.s, 2 H); 7.77 and 8.11 (both d,
1 H each, J = 2.2 Hz). 13C NMR (acetoneꢀd6), δ: 19.8, 52.6,
127.7, 137.8. 14N NMR (acetoneꢀd6), δ: –52.4 (∆ν1/2 = 100 Hz),
–312 (∆ν1/2 = 700 Hz). MS, m/z: 335 [M]+.
References
1. A. M. Churakov, S. L. Ioffe, and V. A. Tartakovsky,
Mendeleev Commun., 1991, 101.
2ꢀ(Adamantanꢀ1ꢀyl)ꢀ1ꢀ(2ꢀaminoꢀ3,5ꢀdibromophenyl)diazene
1ꢀoxide (8j). NꢀBromosuccinimide (0.92 g, 5.16 mmol) was
added with stirring to a solution of aniline 4j (0.7 g, 2.58 mmol)
in MeCN (10 mL) and then the reaction mixture was stirred at
20 °C for 2.5 h. The precipitate that formed was filtered off and
washed on a filter with a small amount of CH2Cl2. The filtrate
was concentrated, the product was extracted from the residue
with hot light petroleum, and the extract was passed through a
short column with silica gel (CHCl3 as the eluent). Amine 8j
was obtained in a yield of 0.92 g (83%), m.p. 118—120 °C.
Found (%): C, 44.65; H, 4.50; Br, 37.32; N, 9.69.
C16H19Br2N3O. Calculated (%): C, 44.78; H, 4.46; Br, 37.79;
N, 9.79. IR (KBr), ν/cm–1: 1490 (N(O)=N); 3310, 3470 (NH2).
1H NMR (acetoneꢀd6), δ: 1.75 (m, 6 H); 2.10 and 2.24 (both m,
3 H each); 6.60 (br.s, 2 H); 7.76 and 8.06 (both d, 1 H each, J =
2. A. M. Churakov, O. Yu. Smirnov, Yu. A. Strelenko, S. L.
Ioffe, V. A. Tartakovsky, Yu. T. Struchkov, F. M. Dolgushin,
and A. I. Yanovsky, Mendeleev Commun., 1994, 122.
3. A. M. Churakov, O. Yu. Smirnov, Yu. A. Strelenko, S. L.
Ioffe, V. A. Tartakovsky, Yu. T. Struchkov, F. M. Dolgushin,
and A. I. Yanovsky, Mendeleev Commun., 1996, 22.
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Kachala, and V. A. Tartakovsky, Org. Lett., 1999, 1, 721.
5. E. T. Apasov, A. M. Churakov, Yu. A. Strelenko, S. L. Ioffe,
and V. A. Tartakovsky, Tetrahedron, 1995, 51, 6775.
6. A. M. Churakov, O. Yu. Smirnov, S. L. Ioffe, Yu. A.
Strelenko, and V. A. Tartakovsky, Izv. Akad. Nauk, Ser.
Khim., 1994, 1620 [Russ. Chem. Bull., 1994, 43, 1532 (Engl.
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2.1 Hz). 14N NMR (acetoneꢀd6), δ: –52.65 (∆ν = 140 Hz).
1/2
MS, m/z: 427 [M]+.
1ꢀ(2ꢀAminoꢀ3,5ꢀdichlorophenyl)ꢀ2ꢀ(tertꢀbutyl)diazene 1ꢀoxꢀ
ide (9a). A 30% aqueous solution of H2O2 (1.6 mL) was added
dropwise with stirring to a solution of aniline 4a (1.2 g, 7 mmol)
in concentrated HCl (10 mL) at 50—60 °C. Then the reaction
mixture was heated for 5 min, cooled, poured into water (50 mL),
and neutralized with an aqueous solution of sodium carbonate.
The product was extracted with ether (3×100 mL), the extract
was dried with MgSO4, the solvent was concentrated, and the
product was purified by column chromatography (CH2Cl2 as
the eluent). Amine 9a was obtained in a yield of 1.12 g (61%),
m.p. 33—34 °C. Found (%): C, 45.76; H, 5.02; Cl, 27.17;
N, 16.19. C10H13Cl2N3O. Calculated (%): C, 45.82; H, 5.00;
Cl, 27.05; N, 16.03. IR (KBr), ν/cm–1: 1490 (N(O)=N); 3360,
3490 (NH2). 1H NMR (acetoneꢀd6), δ: 1.47 (s, 9 H); 6.30
(br. s, 2 H); 7.25 and 7.95 (both d, 1 H each, J = 2.3 Hz).
9. M. J. Mijs, S. E. Hoekstra, R. M. Ulmann, and E. Halinga,
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[Russ. Chem. Rev., 1993, 62, 143 (Engl. Transl.)].
13. M. Hudlicky, Reduction in Organic Chemistry, Wiley, New
York, 1984.
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1985, 22, 1089.
15. W. Gottardi, Monatsh. Chem., 1973, 104, 1681.
14N NMR (acetoneꢀd6), δ: –51.4 (∆ν
m/z: 261 [M]+.
= 120 Hz). MS,
Received May 15, 2001;
in revised form September 3, 2001
1/2