Triazidation of 2,4,6-trifluorobenzenes

Article abstract of DOI:10.1016/j.jfluchem.2013.07.009

1,3,5-Trichloro-2,4,6-trifluorobenzene and 1-bromo-3,5-dichloro-2,4,6- trifluorobenzene undergo selective defluorination on heating in dimethylsulfoxide with sodium azide to form 1,3,5-triazido-2,4,6- trichlorobenzene and 1,3,5-triazido-2-bromo-4,6-dichlorobenzene in high yields. The azidation of 1,3,5-tribromo-2,4,6-trifluorobenzene under similar reaction conditions leads to the mixture of 1,3-diazido-2,4,6-tribromo-5-fluorobenzne and 1,3,5-triazido-2,4,6-tribromobenzene in the 1:2 ratio, respectively. 1,3,5-Triazido-2,4,6-tribromobenzene can be obtained as a sole product in high yield if the azidation of 1,3,5-tribromo-2,4,6-trifluorobenzene with sodium azide is carried out in aqueous acetone. The triazides obtained are the first readily available 1,3,5-triazidobenzenes that may find a wide practical use as new photoactive cross-linking reagents for polymer chemistry and as starting compounds in organic synthesis and photochemical preparation of new organic magnetic materials.

Full text of DOI:10.1016/j.jfluchem.2013.07.009

Accepted Manuscript
Title: Triazidation of 2,4,6-trifluorobenzenes
Author: Sergei V. Chapyshev Alexander V. Chernyak
PII:
S0022-1139(13)00264-9
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2013.07.009
FLUOR 8158
To appear in:
FLUOR
Received date:
Revised date:
Accepted date:
13-6-2013
11-7-2013
16-7-2013
Please cite this article as: S.V. Chapyshev, A.V. Chernyak, Triazidation
of 2,4,6-trifluorobenzenes, Journal of Fluorine Chemistry (2013),
http://dx.doi.org/10.1016/j.jfluchem.2013.07.009
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*Graphical Abstract - Pictogram
F
N3
X
F
X
F
X
X
NaN3
Me2SO, 90o C
N3
N3
Y
Y
X = Y = Cl or Br
X = Cl, Y = Br
81-98%
Page 1 of 14

*Graphical Abstract - Synopsis
1,3,5-Trichloro-2,4,6-trifluorobenzene and 1-bromo-3,5-dichloro-2,4,6-trifluorobenzene undergo
selective defluorination on heating in dimethylsulfoxide with sodium azide to form 1,3,5-
triazido-2,4,6-trichlorobenzene and 1,3,5-triazido-2-bromo-4,6-dichlorobenzene in high yields.
The azidation of 1,3,5-tribromo-2,4,6-trifluorobenzene under similar reaction conditions leads to
the mixture of 1,3-diazido-2,4,6-tribromo-5-fluorobenzne and 1,3,5-triazido-2,4,6-
tribromobenzene in the 1:2 ratio, respectively. 1,3,5-Triazido-2,4,6-tribromobenzene can be
obtained as a sole product in high yield if the azidation of 1,3,5-tribromo-2,4,6-trifluorobenzene
with sodium azide is carried out in aqueous acetone. The triazides obtained are the first readily
available 1,3,5-triazidobenzenes that may find a wide practical use as new photoactive cross-
linking reagents for polymer chemistry and as starting compounds in organic synthesis and
photochemical preparation of new organic magnetic materials.
Page 2 of 14

*Highlights (for review)
-
Simple and efficient synthesis of 1,3,5-triazidobenzenes from commercially available
2,4,6-trifluorobenzenes.
-
-
Selective defluorination of bromofluoro- and chlorofluoro-substituted benzenes.
Effect of substituents on defluorination of 2,4,6-trifluorobenzenes.
Page 3 of 14

*Manuscript
Triazidation of 2,4,6-trifluorobenzenes
Sergei V. Chapyshev,* Alexander V. Chernyak
Institute of Problems of Chemical Physics, Russian Academy of Sciences,142432 Chernogolovka,
Moscow Region, Russian Federation
A B S T R A C T
1,3,5-Trichloro-2,4,6-trifluorobenzene and 1-bromo-3,5-dichloro-2,4,6-trifluorobenzene undergo
selective defluorination on heating in dimethylsulfoxide with sodium azide to form 1,3,5-triazido-
2,4,6-trichlorobenzene and 1,3,5-triazido-2-bromo-4,6-dichlorobenzene in high yields. The
azidation of 1,3,5-tribromo-2,4,6-trifluorobenzene under similar reaction conditions leads to the
mixture of 1,3-diazido-2,4,6-tribromo-5-fluorobenzne and 1,3,5-triazido-2,4,6-tribromobenzene in
the 1:2 ratio, respectively. 1,3,5-Triazido-2,4,6-tribromobenzene can be obtained as a sole product
in high yield if the azidation of 1,3,5-tribromo-2,4,6-trifluorobenzene with sodium azide is carried
out in aqueous acetone. The triazides obtained are the first readily available 1,3,5-triazidobenzenes
that may find a wide practical use as new photoactive cross-linking reagents for polymer chemistry
and as starting compounds in organic synthesis and photochemical preparation of new organic
magnetic materials.
Keywords:
Fluorobenzenes
Azidobenzenes
Triazidation
Nucleophilic Substitution
Chemoselectivity
Cross-linking reagents
Corresponding author: Fax: +7 496 5223507.
E-mail address: chap@icp.ac.ru
1
Page 4 of 14

1. Introduction
Aromatic polyazides are widely used as starting materials in organic synthesis and as
photoactive cross-linking reagents in polymer chemistry and lithography [1-6]. Most of aromatic
polyazides are prepared by azidation of the corresponding halides. Thus, triazidopyridines 11-20 are
readily obtained in high yields by azidation of halides 1-10 in various organic solvents at room
temperature (Scheme 1) [7]. Similar reactions are also used for the synthesis of 2,4,6-
triazidopyrimidines and 2,4,6-triazido-s-triazine [8,9]. At the same time, just two 1,3,5-
triazidobenzenes have been synthesized by azidation of phenylhalides. The reaction of trichloride
21 with an excess of sodium azide in acetonitrile at room temperature gave triazide 23 in 95% yield
(Scheme 2) [10]. Similarly, the reaction of trichloride 22 with an excess of trimethylsilylazide in
acetonitrile at room temperature afforded triazide 24 in 98% yield (Scheme 2) [11]. However, due
to commercial inaccessibility of trichlorides 21 and 22, both triazides 23 and 24 have not found a
wide practical application. Triazide 23 has been used as precursor of high-spin nitrenes. The
photolysis of this triazide allowed the preparation of the first trinitrene with six unpaired electrons
and the ground septet spin-state [12]. Recently, similar high-spin nitrenes were obtained by the
photolysis of triazides 12-14 and 16-18 [13].
X
N3
R1
R2
X
R1
N3
R2
N3
NaN3
DMSO or
Me2CO
X
N
N
1
2
1
2
1:
11:
12:
13:
X = F, R = R = H
R = R = H
1
2
2: X = R1 = R2 = F
3: X = R1 = R2 = Cl
R = R = F
1
2
R = R = Cl
1
2
4:
5:
6:
14: R1 = R2 = Br
15: R1 = R2 = I
X = R = R = Br
1
2
X = F, R = R = I
1
2
1
2
16:
17:
18:
X = Cl, R = R = CN
R = R = CN
1
2
7: X = R1 = F, R2 = Cl
8: X = R1 = Cl, R2 = CN
R = F, R = Cl
1
2
R = Cl, R = CN
1
2
9:
10:
19: R1 = F, R2 = CN
20: R1 = Cl, R2 = CF3
X = R = F, R = CN
X = R = Cl, R = CF3
1
2
Scheme 1.
N3
Cl
NaN3 or
Me3SiN3
R1
N3
R1
N3
R1
R1
Cl
MeCN, r.t.
Cl
R2
R2
1
2
21:
23: R1 = R2 = CN
R = R = CN
1
2
22: R1 = SO2CF3, R2 = NO2
R = SO2CF3, R = NO2
24:
Scheme 2.
2
Page 5 of 14

In continuation of our studies aimed at the design of new organic magnetic materials from
aromatic polyazides [13], we have developed a simple and efficient method of preparation of
triazidobenzenes 29-31 from commercially available trifluorobenzenes 25-27, representing an
interesting example of chemoselective defluorination of chlorofluoro- and bromofluoro-substituted
benzenes with sodium azide (Scheme 3). The results of these studies are reported in the present
work.
F
N3
F
Br
Br
X
X
X
F
X
F
NaN3
+
DMSO, 90o C
N3
N3
N3
N3
Br
Y
Y
29: X = Y = Cl
32
25:
X = Y = Cl
26: X = Cl, Y = Br
27:
30:
31:
X = Cl, Y = Br
X = Y = Br
X = Y = Br
28: X = Y = H
Scheme 3.
2. Results and discussion
In contrast to fluoropyridines 1, 2, 5, 7 and 9, trifluorobenzene 25 did not react with sodium
azide in dimethylsulfoxide at room temperature. However, on heating at 90 ºC for 1 h, the reaction
of 25 with an excess of sodium azide gave triazide 29 in 98% yield. Similarly, triazidation of
trifluoride 26 with sodium azide in dimethylsulfoxide at 90 ºC afforded triazide 30 in 88% yield.
Not very high yield of triazide 30 in the reaction was explained by a high solubility of this triazide
in dimethylsulfoxide and water. The chemoselective defluorination of benzenes 25 and 26 in the
reactions with sodium azide occurred in strict accord with theoretical expectations. According to
theory, the reactivity of phenyl halides in SNAr reactions decreases in the order of fluoride >
chloride > bromide > iodide [14]. This effect is explained by the two-step mechanism of such
reactions, in which the formation of -complexes such as 33 is the rate-determining stage (Scheme
4).
N3
N3
F
F
N3
Cl
Cl
F
Cl
Cl
F
Cl
Cl
F
k2
k1


F
k1
F
F
F
Cl
Cl
Cl
34
33
25
Scheme 4.
3
Page 6 of 14

Unexpectedly, the reaction of trifuoride 27 with an excess of sodium azide in dimethylsulfoxide
at 90 ºC for 1 h stopped at the stage of formation of equilibrium mixture of diazide 32 and triazide
31 in the 1:2 ratio, respectively. The more prolonged (6 h) heating of the reaction mixture did not
noticeably change the ratio between two azides. The column chromatography separation of the
reaction products afforded triazide 31 and diazide 32 in 56 and 30% yields, respectively. Triazide
31 isolated from the reaction appeared to be poorly soluble in acetone. This finding allowed us to
prepare triazide 31 as a sole product in 81% yield, owing to precipitation of this triazide from the
reaction of 27 with sodium azide in aqueous acetone. All our attempts to azidate trifluoride 28,
using various azidating agents and reaction conditions appeared to be ineffectual. The reactions
studied demonstrated that efficiency of triazidation of trifluorides 25-27 strongly depends on
electron-deficiency of the starting compounds. Chlorine-substituted trifluorides 25 and 26 readily
undergo the azidation until triazides 29 and 30. The replacement of two electron-negative fluorine
atoms for the azido groups in bromine-substituted trifuoride 27 leads to diazide 32 possessing
already low reactivity toward the azide anion. Finally, trifluoride 28 does not react at all with
sodium azide.
It is important to note that 1,3,5-triazidobenzenes cannot be prepared by azidation of
hexafluorobenzene 35 or its hexachloro- and hexabromo-substituted analogs. According to the
literature data, hexafluorobenzene 35 reacts with an excess of sodium azide in dimethylsulfoxide at
room temperature to give diazide 36, tetraazide 37 and hexaazide 38 (Scheme 5) [15].
N3
F
N3
F
N3
N3
N3
N3
N3
N3
N3
N3
F
F
F
F
F
F
F
F
NaN3
+
+
DMSO, r.t.
N3
F
N3
F
37
38
36
35
Scheme 5.
Our studies showed that reactions of hexachlorobenzene 39 and hexabromobenzene 40 with an
excess of sodium azide in dimethylsulfoxide at 90 ºC for 2 h give the mixtures of azides 41/43 = 2/1
and 42/44 =3/1 as the major products (Scheme 6).
4
Page 7 of 14

X
X
N3
X
X
X
N3
N3
X
X
X
X
X
X
X
X
NaN3
+
DMSO, 90o C
X
X
39:
40: X = Br
X = Cl
43: X = Cl
44:
41: X = Cl
42:
X = Br
X = Br
Scheme 6.
Triazides 29-31 represent white solid materials that are almost insensitive toward impact and
friction. Thus, for instance, they do not explode on intense grinding in a mortar or strong
hammering. As usual, aromatic polyazides are very sensitive toward impact and friction if their
molecules contain nitrogen more than 70% of the molecular weight [7d]. After melting, triazides
29-31 transform into transparent, colorless liquids that do not decompose on heating until 140 ºC.
Owing to relatively low sensitivity toward impact and friction as well as simplicity of preparation
from commercially available precursors, triazides 29-31 may be of interest as promising
photoactive cross-linking reagents for polymer chemistry and lithography. Moreover, recent
theoretical studies have predicted that a septet trinitrene formed in the photolysis of triazide 31
should possess the strongest magnetic properties among all organic hexaradicals [13f].
3. Conclusions
Trifluorobenzenes 25 and 26 readily undergo chemoselective defluorination on heating in
dimethylsulfoxide with sodium azide to form triazides 29 and 30 in high yields. The azidation of
trifluorobenzene 27 under similar reaction conditions leads to the mixture of triazide 31 and diazide
32 in the 2:1 ratio, respectively. The equilibrium between diazide 32 and triazide 31 can be shifted
to the side of the triazide formation if azidation of 32 is carried out in aqueous acetone. Compounds
29-31 are the first readily available 1,3,5-triazidobenzenes that may find a wide practical use as new
photoactive cross-linking reagents for polymer chemistry and as starting compounds in organic
synthesis and photochemical preparation of new organic magnetic materials.
5
Page 8 of 14

4. Experimental
4.1. Materials and instruments
Melting points were obtained on a Fischer-Johns Model 12-144 melting point apparatus. TLC
analyses were carried out on silica gel 60F254-precoated aluminum sheets with detection by UV
light. 13C, 15N and 19F NMR spectra were recorded on a Bruker Avance III 500 MHz NMR
spectrometer (125, 50 and 470 MHz for 13C, 15N and 19F, respectively), using TMS (C = 0 ppm),
CD3NO2 (N = 0 ppm) and C6F6 (F = –163.0 ppm) as internal standards. IR spectra were recorded
on a Perkin-Elmer Spectrum 100 FT-IR instrument. UV/Vis spectra were recorded on a Varian Cary
1 UV/Vis spectrometer. Elemental analyses were performed on a CHNS/O Vario Microcube
Elemental analyzer. High-resolution and electron impact mass spectral analyses were performed in
the Department of Structural Studies at the Zelinsky Institute of Organic Chemistry, Moscow.
Sodium azide, acetone, ethanol, dimethylsulfoxide, 1,3,5-trichloro-2,4,6-trifluorobenzene and 1-
bromo-3,5-dichloro-2,4,6-trifluorobenzene were obtained from commercial sources and used
without further purification. 1,3,5-Tribromo-2,4,6-trifluorobenzene was prepared by bromination of
commercially available 1,3,5-trifluorobenzene according to the literature procedure [16].
4.2. Safety precautions
Azides 29–32 are typical representatives of high-energy materials that can show unpredictable
behavior. To minimize risks, it is recommended to work with these triazides in quantities less than 5
g, avoiding any impacts (e.g., shock, grinding, pressing, etc.) on the azide crystals. Due to a high
sensitivity toward UV light and moderate thermal stability, azides 29–32 are recommended to store
in a dark place at temperature below 15 ºC.
4.3. Synthetic procedures
4.3.1. 1,3,5-Triazido-2,4,6-trichlorobenzene (29)
A solution of 1,3,5-trichloro-2,4,6-trifluorobenzene (25) (2.35 g, 10 mmol) and NaN3 (2.6 g, 40
mmol) in Me2SO (30 mL) was stirred at 90 ºC for 1 h, then the reaction mixture was cooled to room
temperature and poured into 400 mL of ice water. The precipitate was filtered off, washed with
water, dried on air and recrystallized from ethanol. Triazide 29 (2.98 g, 98%) was obtained as
colorless needles (mp 94 ºC).
UV/VIS (EtOH): max (log ) 246 (4.60), 254 (4.59), 310 (3.04) nm.
6
Page 9 of 14

IR (microcrystals):  2135vs and 2110vs (N3), 1528m (C=C), 1411s, 1394vs, 1322w, 1254s,
1172w, 1089w, 1051w, 957s, 793s, 728m cm–1.
13C NMR (CDCl3):  121.3 (3C, C-Cl), 134.8 (3C, C- N3).
EIMS, 70 eV, m/z (rel. int.): 307 (29), 305 (100) [M]+, 303 (87), 279 (11), 277 (41), 275 (35), 184
(25), 160 (134), 158 (12), 149 (21), 132 (49), 125 (38), 124 (36), 123 (66), 122 (47), 120 (79), 112
(17), 111 (29), 108 (23), 106 (88), 101 (14), 99 (51), 97 (28), 88 (20), 87 (26), 85 (65), 75 (15), 73
(47), 63 (11), 62 (27), 61 (13), 59 (30).
Anal. Calcd. for C6Cl3N9: C, 23.67; N, 41.40. Found: C, 23.76; N, 41.29.
4.3.2. 1,3,5-Triazido-2-bromo-4,6-dichlorobenzene (30)
A solution of 1-bromo-3,5-dichloro-2,4,6-trifluorobenzene (26) (2.80 g, 10 mmol) and NaN3 (2.6 g,
40 mmol) in Me2SO (30 mL) was stirred at 90 ºC for 1 h, then the reaction mixture was cooled to
room temperature and poured into 300 mL of ice water. The precipitate was filtered off, washed
with water, dried on air and recrystallized from ethanol. Triazide 30 (3.07 g, 88%) was obtained as
colorless needles (mp 83 ºC).
UV/VIS (EtOH): max (log ) 246 (4.42), 313 (3.27) nm.
IR (microcrystals):  2129vs and 2103vs (N3), 1530m (C=C), 1404vs, 1388vs, 1314w, 1252vs,
1204w, 1164w, 953s, 794s, 759m, 722m cm–1.
13C NMR (CDCl3):  110.9 (1C, C-Br), 121.8 (2C, C-Cl), 135.3 (1C, C-5), 136.2 (2C, C-1, C-3).
15N NMR (CDCl3):  –143.1 (2N, N of 1- and 3-N3), –143.2 (1N, N of 5-N3), –149.2 (1N, N of
5-N3), –149.8 (2N, N of 1- and 3-N3), –284.2 (1N, N of 5-N3), –288.0 (2N, N of 1- and 3-N3).
EIMS, 70 eV, m/z (rel. int.): 349 (13), 347 (8) [M]+, 321 (6), 168 (10), 166 (42), 164 (33), 152 (8),
150 (6), 149 (12), 134 (13), 132 (19), 131 (12), 129 (12), 125 (21), 124 (8), 123 (62), 122 (25), 120
(38), 119 (14), 117 (14), 111 (21), 100 (10), 99 (30), 97 (20), 91 (8), 88 (15), 87 (34), 86 (11), 85
(100), 81 (10), 79 (10), 76 (33), 75 (21), 74 (12), 73 (63), 71 (17), 64 (15), 62 (30), 59 (6), 50 (13).
Anal. Calcd. for C6BrCl2N9: C, 20.65; N, 36.13. Found: C, 20.81; N, 36.02.
4.3.3. 1,3,5-Triazido-2,4,6-tribromobenzene (31)
A solution of 1,3,5-tribromo-2,4,6-trifluorobenzene (27) (3.68 g, 10 mmol) and NaN3 (1.95 g, 30
mmol) in aq acetone (50 mL, 10% H2O) was boiled at 70 ºC for 1 h, then the reaction mixture was
cooled to 10 ºC and filtered. After addition of the second portion of NaN3 (1.95 g, 30 mmol) to the
solution, the mixture was boiled again at 70 ºC for 1 h, then cooled to 10 ºC and filtered. These
operations were repeated once again. The solid material collected on the filter was washed with
7
Page 10 of 14

water, dried on air and recrystallized from acetone. Triazide 31 (3.55 g, 81%) was obtained as
colorless needles (mp 105 ºC).
UV/VIS (EtOH): max (log ) 243 (4.60), 317 (2.26) nm.
IR (microcrystals):  2125vs and 2099s (N3), 1526m (C=C), 1395s, 1375vs, 1245s, 1230m, 1158w,
1086w, 955w, 940w, 771m, 760m, 743w, 727w, 698m, 682w cm–1.
13C NMR (CDCl3):  112.4 (3C, C-Br), 139.1 (3C, C- N3).
15N NMR (CDCl3):  –142.1 (N), –148.4 (N), –279.0 (N).
EIMS, 70 eV, m/z (rel. int.): 439 (13), 437 (13) [M]+, 411 (5), 409 (5), 274 (12), 272 (5), 224 (24),
222 (36), 220 (16), 212 (44), 210 (91), 208 (48), 198 (11), 196 (14), 195 (25), 194 (7), 193 (25),
170 (5), 169 (65), 167 (67), 157 (14), 155 (16), 145 (22), 143 (51), 141 (30), 131 (96), 129 (100),
119 (60), 117 (74), 115 (17), 114 (31), 105 (10), 100 (16), 93 (37), 91 (38), 88 (38), 81 (38), 79
(40), 76 (48), 64 (38), 62 (66), 50 (32).
Anal. Calcd. for C6Br3N9: C, 16.46; N, 28.79. Found: C, 16.64; N, 28.56.
4.3.4. 1,3-Diazido-2,4,6-tribromo-5-fluorobenzene (32)
A solution of 1,3,5-tribromo-2,4,6-trifluorobenzene (27) (3.68 g, 10 mmol) and NaN3 (3.9 g, 60
mmol) in Me2SO (30 mL) was stirred at 90 ºC for 1 h, then the reaction mixture was cooled to room
temperature and poured into 500 mL of ice water. The precipitate was filtered off, washed with
water, dried on air and chromatographed on a column with silica gel 60, using a system heptane –
benzene = 4:1 as an eluent. Two fractions with Rf = 0.57 and 0.49 were collected. The evaporation
of the solvent from the fractions with Rf = 0.57 followed by recrystallization of the solid residue
from ethanol gave diazide 32 (1.24 g, 30%) as colorless crystals (mp 67 ºC).
UV/VIS (EtOH): max (log ) 227 (4.82), 312 (2.64) nm.
IR (microcrystals):  2154s and 2111vs (N3), 1557m and 1538m (C=C), 1394vs, 1374s, 1254s,
1197m, 1011m, 950w, 762m, 703m, 687s cm–1.
19F NMR (CDCl3): –91.87 (s, 1F, F-6).
13C NMR (CDCl3):  103.7 (d, 2JC,F = 25.5, C-4, C-6), 109.9 (d, 4JC,F = 4.2, C-2), 137.8 (d, 3JC,F
2.8, C-1, C-3), 155.8 (d, 1JC,F = 246.8, C-5).
=
EIMS, 70 eV, m/z (rel. int.): 416 (4), 414 (5) [M]+, 281 (50), 280 (8), 279 (100), 277 (53), 255 (6),
253 (13), 251 (7), 200 (44), 198 (45), 174 (8), 172 (9), 148 (6), 136 (8), 134 (6), 131 (10), 129 (10),
124 (5), 122 (5), 119 (39), 117 (7), 107 (6), 105 (12), 100 (13), 93 (33), 91 (10), 86 (6), 81 (22), 79
(20), 74 (7), 69 (9), 62 (9), 55 (8).
HRMS (ESI), m/z: calcd for C6HBr3FN6 412.7791 [M+H]+; found: 412.7799.
8
Page 11 of 14

The evaporation of the solvent from the fractions with Rf = 0.49 followed by
recrystallization of the solid residue from acetone gave triazide 31 (2.32 g, 56%) as colorless
needles (mp 105 ºC).
4.3.5. Azidation of hexachlorobenzene (39)
A solution of hexachlorobenzene (39) (2.85 g, 10 mmol) and NaN3 (2.6 g, 40 mmol) in Me2SO (30
mL) was stirred at 90 ºC for 2 h, then the reaction mixture was cooled to room temperature and
poured into 400 mL of ice water. The precipitate was filtered off, washed with water, dried on air
and analyzed using 13C NMR spectroscopy. The spectrum recorded showed the signal of the
starting chlorobenzene 39 (63%) at  132.2 ppm and seven new signals that were assigned to azide
41 (25%) and diazide 43 (12%).
1-Azidopentachlorobenezene (41); 13C NMR (CDCl3):  127.6 (s, 2C, C-2, C-6); 130.7 (s, 1C, C-4),
132.3 (s, 2C, C-3, C-5), 134.9 (s, 1C, C-1).
1,2-Diazidotetrachlorobenzene (43); 13C NMR (CDCl3):  127.0 (s, 2C, C-3, C-6); 130.6 (s, 2C, C-
4, C-5), 130.6 (s, 2C, C-1, C-2).
4.3.6. Azidation of hexabromobenzene (40)
A solution of hexachlorobenzene (40) (5.51 g, 10 mmol) and NaN3 (2.6 g, 40 mmol) in Me2SO (30
mL) was stirred at 90 ºC for 2 h, then the reaction mixture was cooled to room temperature and
poured into 400 mL of ice water. The precipitate was filtered off, washed with water, dried on air
and analyzed using 13C NMR spectroscopy. The spectrum recorded showed the signal of the
starting bromobenzene 40 (82%) at  128.4 ppm and seven new signals that were assigned to azide
42 (13%) and diazide 44 (5%).
1-Azidopentabromobenezene (42); 13C NMR (CDCl3):  119.9 (s, 2C, C-2, C-6); 124.4 (s, 1C, C-4),
124.8 (s, 2C, C-3, C-5), 133.2 (s, 1C, C-1).
1,2-Diazidotetrabromobenzene (44); 13C NMR (CDCl3):  117.0 (s, 2C, C-3, C-6); 121.2 (s, 2C, C-
4, C-5), 127.9 (s, 2C, C-1, C-2).
Acknowledgements
This work was financially supported by the Russian Academy of Sciences (program OX-01).
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