Microwave promoted environmentally benign synthesis of 2- aminobenzothiazoles and their urea derivatives

Article abstract of DOI:10.1080/10426500701578506

2-Aminobenzothiazoles were efficiently synthesized using stable, crystalline tetrabutylammonium tribromide instead of toxic, corrosive liquid bromine under solvent-free and microwave irradiation condition. Furthermore, benzothiazol-2-ylureas were synthesized in good to high yield by reactions of 2-aminobenzothiazoles with N-trichloroacetanilides, which were used as a substitute for toxic, unstable isocyanates, under microwave irradiation condition. This protocol has advantages of no utilization of hazardous chemicals, rapid reaction rate, high yield, and easy work-up procedure. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426500701578506

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Phosphorus, Sulfur, and Silicon
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Microwave Promoted
Environmentally
Benign Synthesis of 2-
Aminobenzothiazoles and Their
Urea Derivatives
Zheng Li a , Shuxiu Xiao a , Guoqiang Tian a , Anguo
Zhu a , Xu Feng a & Jing Liu a
a Gansu Key Laboratory of Polymer Materials,
College of Chemistry and Chemical Engineering ,
Northwest Normal University , Lanzhou, Gansu, P.R.
China
Published online: 09 May 2008.
To cite this article: Zheng Li , Shuxiu Xiao , Guoqiang Tian , Anguo Zhu , Xu Feng
& Jing Liu (2008) Microwave Promoted Environmentally Benign Synthesis of 2-
Aminobenzothiazoles and Their Urea Derivatives, Phosphorus, Sulfur, and Silicon and
the Related Elements, 183:5, 1124-1133, DOI: 10.1080/10426500701578506
To link to this article: http://dx.doi.org/10.1080/10426500701578506
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Phosphorus, Sulfur, and Silicon, 183:1124–1133, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701578506
Microwave Promoted Environmentally Benign Synthesis
of 2-Aminobenzothiazoles and Their Urea Derivatives
Zheng Li, Shuxiu Xiao, Guoqiang Tian, Anguo Zhu,
Xu Feng, and Jing Liu
Gansu Key Laboratory of Polymer Materials, College of Chemistry and
Chemical Engineering, Northwest Normal University, Lanzhou, Gansu,
P.R. China
2-Aminobenzothiazoles were efficiently synthesized using stable, crystalline tetra-
butylammonium tribromide instead of toxic, corrosive liquid bromine under solvent-
free and microwave irradiation condition. Furthermore, benzothiazol-2-ylureas
were synthesized in good to high yield by reactions of 2-aminobenzothiazoles with
N-trichloroacetanilides, which were used as a substitute for toxic, unstable iso-
cyanates, under microwave irradiation condition. This protocol has advantages
of no utilization of hazardous chemicals, rapid reaction rate, high yield, and easy
work-up procedure.
Keywords 2-Aminobenzothiazole; microwave irradiation; N-trichloroacetanilide;
tetrabutylammonium tribromide; urea
INTRODUCTION
2-Aminobenzothiazoles are important intermediates, which have been
used in the synthesis of dithiocarbamates,1 heterocyclic compounds,2
phosphorus complexes,3 etc. 2-Aminobenzothiazoles are prepared by
many methods which include i) the cyclization of arylthioureas
with liquid bromine,4 benzyltrimethylammonium tribromide,5 thionyl
chloride,6 or sulfuryl chloride;7 ii) the reactions of arylamines with
liquid bromine and potassium thiocyanate;8−9 iii) the reactions
of 1,2-aminoiodoarenes with thiourea in the presence of nickel(0)
Received 9 July 2007; accepted 10 July 2007.
The authors thank the Gansu Natural Science Foundation (3ZS061-A25-033), ”Chun-
hui Project” of the Ministry of Education of China (Z2004-1-62034), and Key Laboratory of
Eco-Environment-Related Polymer Materials (Northwest Normal University), Ministry
of Education of China for the financial support of this work.
Address correspondence to Zheng Li, Gansu Key Laboratory of Polymer Materials,
College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou,
Gansu, 730070, P.R. China. E-mail: lizheng@nwnu.edu.cn.
1124

Aminobenzothiazoles and Their Urea Derivatives
1125
complex;10 iv) the reactions of 2-aminobenzenethiols with di(imidazole-
1-yl)methanimine;11 and v) the reactions of phenyl isothiocyanate with
amines and [Bmin]Br3 in ionic liquid12 (Scheme 1). However, the gener-
ally used reagent, liquid bromine, is a toxic and corrosive reagent, and
can be difficult to manipulate on small scale. Meanwhile, the volatile
organic solvents and other hazardous reagents are also used, which can
result in environmental pollution.
SCHEME 1 The reported synthetic methods for 2-aminobenzothiazoles.
Meanwhile N, Nꢀ-disubstituted ureas are important subunits
present in a number of naturally occurring compounds and have found
numerous applications as dyes, antioxidants, pesticides, corrosion in-
hibitors, intermediates for the preparation of pharmaceuticals, and
agricultural chemicals.13 The most commonly used synthetic method
for substituted ureas is by reactions of isocyanates with amines.14 This
method has several disadvantages: i) the synthesis of isocyanates usu-
ally involves the use of highly toxic phosgene; ii) most of the isocyanates
are toxic, unstable, and their storage is inconvenient.
In this paper, we report an expeditious and environmentally benign
method to prepare the 2-aminobenzothiazoles using nontoxic, easy to
handle tetrabutylammonium tribromide (TBATB) as the substitute for
hazardous liquid bromine under solvent-free and microwave conditions,
and further to prepare benzothiazolylureas via non-phosgene approach

1126
Z. Li et al.
using eco-friendly N-trichloroacetanilides as substitutes for toxic and
unstable isocyanates under microwave irradiation condition.
RESULTS AND DISCUSSION
In our investigation, we chose one-pot method to synthesize 2-
aminobenzothiazoles (1a–d) using commercially available aromatic
amines and potassium thiocyanate as starting materials and TBATB
as substitute reagent for liquid bromine. TBATB can be prepared by
no use of liquid bromine via environmentally benign methods, such
as by the reaction of tetrabutylammonium bromide with V2O5 and
aqueous H2O125 or the reaction of tetrabutylammonium bromide with
sodium bromate and hydrobromic acid in aqueous media.16 TBATB is
a high molecular weight, stable, crystalline organic ammonium tribro-
mide, and can deliver a stoichiometric amount of bromine where small
amounts are necessary for microscale reactions, and can be readily
utilized as an alternative electrophilic bromine source. The reactions
were performed under solvent-free and microwave irradiation condi-
tions to readily afford the 2-aminobenzothiazoles (1a–d) in high yield.
The amines bearing electron-donating groups were easier to give prod-
ucts than bearing electron-withdrawing groups.
SCHEME 2 Synthesis of 2-aminobenzothiazoles and their urea derivatives.
Furthermore, the resulting 2-aminobenzothiazoles (1a–d) reacted
with N-trichloroacetanilides, which were easily prepared by reactions
of aromatic amines with trichloroacetic acid,17 in the presence of sodium
hydroxide in DMSO under microwave irradiation to afford N-aryl-
N’-(benzothiazol-2-yl)ureas (2a–x) in good to high yield (Scheme 2,
Table I). All reactions were complete in a 4–6 min time period under
130 W of microwave power. In these reactions, N-trichloroacetanilides
acted as in situ isocyanate generating reagents for the synthesis of dis-
ubstituted ureas.17 This protocol effectively avoided the preparation,
separation, and storage of the unstable and hazardous isocyanates. The

Aminobenzothiazoles and Their Urea Derivatives
1127
TABLE I Synthesis of Compounds 1a-d and 2a-x under Microwave
Irradiation
Microwave Time
power (W) (min)
M.p.
(◦C)
Yield
(%)a
Compound
R
Rꢀ
1a
1b
1c
1d
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
2o
2p
2q
2r
2s
2t
2u
2v
2w
2x
CH3
Cl
NO2
OCH3
CH3
Cl
NO2
CH3
Cl
NO2
CH3
Cl
NO2
CH3
Cl
NO2
CH3
Cl
NO2
CH3
Cl
NO2
CH3
Cl
—
—
—
—
H
H
H
4-CH3
4-CH3
4-CH3
4-Cl
195
195
195
195
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
130
3
4
5
4
6
6
4
6
6
4
6
6
4
6
6
4
6
6
4
6
6
4
6
6
4
6
6
4
138–139 (132.5–133.5)18
199–200 (199–201)21
247–248 (247–249)20
164–166 (165–167)19
244–246
86
80
76
84
64
66
78
60
68
80
69
67
79
69
62
77
64
63
85
65
70
78
64
62
75
67
62
82
299–301
324–326
252–254
296–298
305–306 (dec.)
249–251
295–297
323–325 (dec.)
253–255
298–300
312–314 (dec.)
260–262
291–293
324–325 (dec.)
263–265
4-Cl
4-Cl
4-CH3O
4-CH3O
4-CH3O
4-NO2
4-NO2
4-NO2
2-CH3
2-CH3
2-CH3
2-CH3-4-Br
2-CH3-4-Br
2-CH3-4-Br
3-Br
281–283
342–344
238–250
298–300
NO2
CH3
Cl
315–317 (dec.)
266–268
318–320
318–320 (dec.)
3-Br
3-Br
NO2
aYields refer to the isolated products.
various substitutes on the aromatic ring have no obvious effect on the
reaction rate and product yield.
The chemical structures of compounds 2a–x were confirmed by IR,
1
1H NMR spectra and elemental analyses. H NMR analyses show the
proton peaks at 11.18–11.68, 8.96–9.93 ppm for NH. IR spectra show
the characteristic absorption at 3321–3368 cm−1 for NH and 1680–
1722 cm−1 for C O.22
In conclusion, we have developed an expeditious and convenient syn-
thetic route for the preparation of 2-aminobenzothiazoles and their urea
derivatives under microwaves irradiation. The use of TBATB as substi-
tute for hazardous liquid bromine, and avoiding the use of highly toxic

1128
Z. Li et al.
phosgene and isocyanates make this protocol more environmentally be-
nign, and a good alternative to synthesis of corresponding compounds
over the current existing methods.
EXPERIMENTAL
IR spectra were recorded using KBr pellets on a Digilab FTS 3000 FTIR
1
spectrophotometer and H NMR spectra on a Mercury-400BB instru-
ment using (CD3)2SO as solvent and Me4Si as internal standard. El-
emental analyses were performed on a Vario E1 Elemental Analysis
instrument. Melting points were observed in an electrothermal melt-
ing point apparatus. Microwave reactions were conducted in a modified
microwave oven fitted with a condenser (LG-WP650, China). TBATB15–
16
and N-trichloroacetanilides17 were prepared according to literature
procedures.
General Procedure for Preparation of 2-Aminobenzothiazoles
(1a–d)
The mixture of aromatic amine (1.0 mmol), potassium thiocyanate (1.0
mmol), and TBATB (1.0 mmol) was ground in a mortar with a pestle
until a homogeneous powder was given. Then the mixture was trans-
ferred to a round-bottomed flask and subjected to microwave irradiation
at power of 195 W for appropriate time indicated in Table I. The progress
of reaction was monitored by TLC using petroleum ether, ethyl acetate
and acetone (4:2:1) as eluent. The resulting solid was dissolved in water,
and the solution was neutralized with ammonia. Then the precipitate
was collected by filtration and recrystallized from ethanol and water
to give the product. The analytical data for represent compounds are
given below:
2-Amino-6-chlorobenzothiazole (1b)
1
IR (KBr): ν = 3455, 3087, 1632, 1532, 1445, 1304, 1105. H NMR
(DMSO-d6, 400 MHz):δ 7.77 (s, 1H, Ar-H), 7.62 (s, 2H, NH2), 7.30 (d, J
= 9.2 Hz, 1H, Ar-H), 7.21 (d, J = 9.2 Hz, 1H, Ar-H). Anal. Calcd. for
C7H5ClN2S: C, 45.53; H, 2.73; N, 15.17. Found: C, 45.67; H, 2.69; N,
15.31.
2-Amino-6-nitrobenzothiazole (1c)
1
IR (KBr): ν = 3457, 3063, 1653, 1531, 1494, 1327, 1296. H NMR
(DMSO-d6, 400 MHz):δ 8.69 (s, 1H, Ar-H), 8.26 (s, 2H, NH2), 8.10 (d,
J = 8.4 Hz, 1H, Ar-H), 7.42 (d, J = 8.4 Hz, 1H, Ar-H). Anal. Calcd. for

Aminobenzothiazoles and Their Urea Derivatives
1129
C7H5N3O2S: C, 43.07; H, 2.58; N, 21.53. Found: C, 42.96; H, 2.65; N,
21.44.
General Procedure for Preparation of N-aryl-N’-(benzothiazol-
2-yl)ureas (2a–x)
To the solution of 2-aminobenzothiazole (0.30 mmol) in 2 mL of DMSO,
N-trichloroacetanilide (0.33 mmol) and NaOH (0.60 mmol) were added.
Then the mixture was subjected to microwave irradiation under the
power of 130 W for appropriate time indicated in Table I. The completion
of reaction was monitored by TLC using petroleum ether, ethyl acetate
and acetone (4:2:1) as eluent. The resulting mixture was poured into
ice, and the solution was neutralized with 1M HCl to pH = 2–3. The
precipitate was collected by filtration and recrystallized from DMF-H2O
to give the product. The analytical data for compounds 2a–x are given
below.
N-phenyl-N’-(6-methylbenzothiazol-2-yl)urea (2a)
1
IR (KBr): ν = 3330 (N H), 1689 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.20 (s, 1H, NH), 9.74 (s, 1H, NH), 7.01–8.29 (m, 8H, Ar-H),
2.35 (s, 3H, CH3). Anal. Calcd. for C15H13N3OS: C, 63.58; H, 4.62; N,
14.83. Found: C, 63.69; H, 4.52; N, 14.74.
N-phenyl-N’-(6-chlorobenzothiazol-2-yl)urea (2b)
1
IR (KBr): ν = 3332 (N H), 1690 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.24 (s, 1H, NH), 9.77 (s, 1H, NH), 7.09–8.31 (m, 8H, Ar-H).
Anal. Calcd. for C14H10ClN3OS: C, 55.35; H, 3.32; N, 13.83. Found: C,
55.44; H, 2.28; N, 13.95.
N-phenyl-N’-(6-nitrobenzothiazol-2-yl)urea (2c)
1
IR (KBr): ν = 3348 (N H), 1717 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.35 (s, 1H, NH), 9.66 (s, 1H, NH), 7.18–8.44 (m, 8H, Ar-H).
Anal. Calcd. for C14H10N4O3S: C, 53.50; H, 3.21; N, 17.82. Found: C,
53.38; H, 3.30; N, 17.71.
N-(4-methylphenyl)-N’-(6-methylbenzothiazol-2-yl)urea (2d)
1
IR (KBr): ν = 3325 (N H), 1680 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.18 (s, 1H, NH), 9.70 (s, 1H, NH), 7.01–8.22 (m, 7H, Ar-H),
2.33 (s, 3H, CH3), 2.25 (s, 3H, CH3). Anal. Calcd. for C16H15N3OS: C,
64.62; H, 5.08; N, 14.13. Found: C, 64.75; H, 5.11; N, 14.20.
N-(4-methylphenyl)-N’-(6-chlorobenzothiazol-2-yl)urea (2e)
1
IR (KBr): ν = 3330 (N H), 1711 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.43 (s, 1H, NH), 9.08 (s, 1H, NH), 7.24–8.20 (m, 7H, Ar-H),

1130
Z. Li et al.
2.30 (s, 3H, CH3). Anal. Calcd. for C15H12ClN3OS: C, 56.69; H, 3.81; N,
13.22. Found: C, 56.75; H, 2.74; N, 13.17.
N-(4-methylphenyl)-N’-(6-nitrobenzothiazol-2-yl)urea (2f)
1
IR (KBr): ν = 3349 (N H), 1712 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.41 (s, 1H, NH), 9.49 (s, 1H, NH), 7.31–8.58 (m, 7H, Ar-H),
2.34 (s, 3H, CH3). Anal. Calcd. for C15H12N4O3S: C, 54.87; H, 3.68; N,
17.06. Found: C, 54.96; H, 3.60; N, 16.95.
N-(4-chlorophenyl)-N’-(6-methylbenzothiazol-2-yl)urea (2g)
1
IR (KBr): ν = 3328 (N H), 1712 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.33 (s, 1H, NH), 9.46 (s, 1H, NH), 7.11–8.18 (m, 7H, Ar-H),
2.26 (s, 3H, CH3). Anal. Calcd. for C15H12ClN3OS: C, 56.69; H, 3.81; N,
13.22. Found: C, 56.54; H, 3.89; N, 13.30.
N-(4-chlorophenyl)-N’-(6-chlorobenzothiazol-2-yl)urea (2h)
1
IR (KBr): ν = 3330 (N H), 1714 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.38 (s, 1H, NH), 9.50 (s, 1H, NH), 7.26–8.30 (m, 7H, Ar-H).
Anal. Calcd. for C14H9Cl2N3OS: C, 49.72; H, 2.68; N, 12.42. Found: C,
49.61; H, 2.75; N, 12.33.
N-(4-chlorophenyl)-N’-(6-nitrobenzothiazol-2-yl)urea (2i)
1
IR (KBr): ν = 3334 (N H), 1714 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.45 (s, 1H, NH), 9.38 (s, 1H, NH), 7.39–8.26 (m, 7H, Ar-H).
Anal. Calcd. for C14H9ClN4O3S: C, 48.21; H, 2.60; N, 16.06. Found: C,
48.06; H, 2.52; N, 15.94.
N-(4-methoxyphenyl)-N’-(6-methylbenzothiazol-2-yl)urea (2j)
1
IR (KBr): ν = 3326 (N H), 1710 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.31 (s, 1H, NH), 9.42 (s, 1H, NH), 7.08–8.15 (m, 7H, Ar-H),
3.84 (s, 3H, CH3), 2.25 (s, 3H, CH3). Anal. Calcd. for C16H15N3O2S: C,
61.32; H, 4.82; N, 13.41. Found: C, 61.45; H, 4.77; N, 13.33.
N-(4-methoxyphenyl)-N’-(6-chlorobenzothiazol-2-yl)urea (2k)
1
IR (KBr): ν = 3329 (N H), 1711 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.37 (s, 1H, NH), 9.49 (s, 1H, NH), 7.15–8.20 (m, 7H, Ar-H),
3.86 (s, 3H, CH3). Anal. Calcd. for C15H12ClN3O2S: C, 53.97; H, 3.62;
N, 12.59. Found: C, 54.10; H, 3.55; N, 12.64.
N-(4-methoxyphenyl)-N’-(6-nitrobenzothiazol-2-yl)urea (2l)
1
IR (KBr): ν = 3347 (N H), 1717 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.54 (s, 1H, NH), 9.23 (s, 1H, NH), 7.31–8.62 (m, 7H, Ar H),

Aminobenzothiazoles and Their Urea Derivatives
1131
3.88 (s, 3H, CH3). Anal. Calcd. for C15H12N4O4S: C, 52.32; H, 3.51; N,
16.27. Found: C, 52.22; H, 3.42; N, 16.38.
N-(4-nitrophenyl)-N’-(6-methylbenzothiazol-2-yl)urea (2m)
1
IR (KBr): ν = 3351 (N H), 1714 (C O). H NMR (DMSO-d6, 400
MHz): δ11.56 (s, 1H, NH), 9.00 (s, 1H, NH), 7.05–8.57 (m, 7H, Ar-H),
2.27 (s, 3H, CH3). Anal. Calcd. for C15H12N4O3S: C, 54.87; H, 3.68; N,
17.06. Found: C, 54.98; H, 2.73; N, 16.92.
N-(4-nitrophenyl)-N’-(6-chlorobenzothiazol-2-yl)urea (2n)
1
IR (KBr): ν = 3357 (N H), 1718 (C O). H NMR (DMSO-d6, 400
MHz): δ11.59 (s, 1H, NH), 9.08 (s, 1H, NH), 7.11–8.62 (m, 7H, Ar-H).
Anal. Calcd. for C14H9ClN4O3S: C, 48.21; H, 2.60; N, 16.06. Found: C,
48.10; H, 2.53; N, 16.12.
N-(4-nitrophenyl)-N’-(6-nitrobenzothiazol-2-yl)urea (2o)
1
IR (KBr): ν = 3368 (N H), 1722 (C O). H NMR (DMSO-d6, 400
MHz): δ11.68 (s, 1H, NH), 9.35 (s, 1H, NH), 7.22–8.69 (m, 7H, Ar-H).
Anal. Calcd. for C14H9N5O5S: C, 46.80; H, 2.52; N, 19.49. Found: C,
46.71; H, 2.46; N, 19.55.
N-(2-methylphenyl)-N’-(6-methylbenzothiazol-2-yl)urea (2p)
1
IR (KBr): ν = 3321 (N H), 1685 (C O). H NMR (DMSO-d6, 400
MHz): δ11.21 (s, 1H, NH), 8.97 (s, 1H, NH), 7.00–8.19 (m, 7H, Ar-H),
2.26 (s, 3H, CH3), 2.22 (s, 3H, CH3). Anal. Calcd. for C16H15N3OS: C,
64.62; H, 5.08; N, 14.13. Found: C, 64.50; H, 5.13; N, 14.19.
N-(2-methylphenyl)-N’-(6-chlorobenzothiazol-2-yl)urea (2q)
1
IR (KBr): ν = 3337 (N H), 1707 (C O). H NMR (DMSO-d6, 400
MHz): δ11.52 (s, 1H, NH), 8.99 (s, 1H, NH), 7.01–8.53 (m, 7H, Ar-H),
2.25 (s, 3H, CH3). Anal. Calcd. for C15H12ClN3OS: C, 56.69; H, 3.81; N,
13.22. Found: C, 56.77; H, 3.73; N, 13.15.
N-(2-methylphenyl)-N’-(6-nitrobenzothiazol-2-yl)urea (2r)
1
IR (KBr): ν = 3351 (N H), 1714 (C O). H NMR (DMSO-d6, 400
MHz): δ11.28 (s, 1H, NH), 9.93 (s, 1H, NH), 7.21–8.32 (m, 7H, Ar-H),
2.36 (s, 3H, CH3). Anal. Calcd. for C15H12N4O3S: C, 54.87; H, 3.68; N,
17.06. Found: C, 54.73; H, 2.61; N, 17.12.

1132
Z. Li et al.
N-(2-methyl-4-bromophenyl)-N’-(6-methylbenzothiazol-2-
yl)urea
(2s)
1
IR (KBr): ν = 3340 (N H), 1706 (C O). H NMR (DMSO-d6, 400
MHz): δ11.57 (s, 1H, NH), 8.96 (s, 1H, NH), 7.32–8.60 (m, 6H, Ar H),
2.28 (s, 3H, CH3), 2.21 (s, 3H, CH3). Anal. Calcd. for C16H14BrN3OS: C,
51.07; H, 3.75; N, 11.17. Found: C, 49.95; H, 3.66; N, 11.26.
N-(2-methyl-4-bromophenyl)-N’-(6-chlorobenzothiazol-2-
yl)urea
(2t)
1
IR (KBr): ν = 3343 (N H), 1709 (C O). H NMR (DMSO-d6, 400
MHz): δ11.59 (s, 1H, NH), 8.98 (s, 1H, NH), 7.34–8.61 (m, 6H, Ar H),
2.22 (s, 3H, CH3). Anal. Calcd. for C15H11BrClN3OS: C, 45.42; H, 2.79;
N, 10.59. Found: C, 45.35; H, 2.88; N, 10.67.
N-(2-methyl-4-bromophenyl)-N’-(6-nitrobenzothiazol-2-yl)urea
(2u)
1
IR (KBr): ν = 3350 (N H), 1716 (C O). H NMR (DMSO-d6, 400
MHz): δ11.61 (s, 1H, NH), 9.01 (s, 1H, NH), 7.39–8.63 (m, 6H, Ar H),
2.23 (s, 3H, CH3). Anal. Calcd. for C15H11BrN4O3S: C, 44.24; H, 2.72;
N, 13.76. Found: C, 44.11; H, 2.65; N, 13.83.
N-(3-bromophenyl)-N’-(6-methylbenzothiazol-2-yl)urea (2v)
1
IR (KBr): ν = 3329 (N H), 1713 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.35 (s, 1H, NH), 9.47 (s, 1H, NH), 7.13–8.20 (m, 7H, Ar H),
2.26 (s, 3H, CH3). Anal. Calcd. for C15H12BrN3OS: C, 49.73; H, 3.34; N,
11.60. Found: C, 49.88; H, 3.26; N, 11.53.
N-(3-bromophenyl)-N’-(6-chlorobenzothiazol-2-yl)urea (2w)
1
IR (KBr): ν = 3331 (N H), 1715 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.39 (s, 1H, NH), 9.52 (s, 1H, NH), 7.28–8.32 (m, 7H, Ar H).
Anal. Calcd. for C14H9BrClN3OS: C, 43.94; H, 2.37; N, 10.98. Found: C,
44.06; H, 2.44; N, 11.07.
N-(3-bromophenyl)-N’-(6-nitrobenzothiazol-2-yl)urea (2x)
1
IR (KBr): ν = 3335 (N H), 1716 (C O). H NMR (DMSO-d6, 400
MHz): δ 11.47 (s, 1H, NH), 9.41 (s, 1H, NH), 7.40–8.28 (m, 7H, Ar H).
Anal. Calcd. for C14H9BrN4O3S: C, 42.76; H, 2.31; N, 14.25. Found: C,
42.63; H, 2.25; N, 14.34.

Aminobenzothiazoles and Their Urea Derivatives
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