D. Gandhi and S. Agarwal: Synthesis of 2-arylbenzothiazolesꢊꢁꢀꢀꢀꢊ3
ethyl acetate; visualization was accomplished by UV irradiation or 2-(4-Ethoxy-phenyl)-benzothiazole (3e)ꢀYield 95%; gray crystals;
exposure to iodine. The starting material 2-amino-4,6-dimethyl-ben- mp 117–120°C; IR: 3152 (C-H stretching, Ar), 3087 (C-H stretching,
−
1
1
zenethiol was synthesized as previously reported [33].
CH ), 2925 (CH , C-H stretching), 1460 cm (aromatic C=C); H NMR:
3
2
δ 1.27 (t, 3H, CH , Jꢁ=ꢁ7.0 Hz), 4.14 (q, 2H, CH , Jꢁ=ꢁ7.0 Hz), 7.12–7.97 (m,
3
2
1
3
8
1
H, Ar-H and BT-H); C NMR: δ 14.7, 63.6, 114.5, 114.7, 122.7, 124.1, 125.2,
26.9, 127.3, 128.1, 128.5, 135.4, 154.3, 161.0, 167.1; MS (EI): m/z 255.68
M+]. Anal. Calcd for C H NOS: C, 70.56; H, 5.13; N, 5.49. Found: C,
Synthesis of urea nitrate catalyst
[
7
1
5
13
0.68; H, 5.19; N, 5.55.
Urea (3 g) in a 100-mL beaker was treated dropwise by stirring with
HNO (10 mL). A clear solution was formed upon heating. The solu-
3
2-Furan-2-yl-benzothiazole (3f)ꢀYield 97%; dark purple crystals;
tion was cooled to rt and the resultant bright shiny crystals of urea
nitrate were filtered, dried and stored in air tight vials. The catalyst is
unstable in the presence of water.
−1
mp 105–108°C; IR: 3080 (C-H stretching, Ar), 1458 cm (aromatic
1
C=C); H NMR: δ 6.70 (1H, dd, Jꢁ=ꢁ3.4, 1.8 Hz), 7.19 (1H, dd, Jꢁ=ꢁ3.4,
0
.9 Hz), 7.30–8.09 (m, 4H, BT-H), 7.98 (1H, dd, Jꢁ=ꢁ1.8 Hz and 0.9 Hz);
1
3
C NMR: δ 108.8, 112.3, 122.6, 124.6, 124.8, 126.3, 133.8, 144.1, 149.1,
1
53.1, 156.6; MS (EI): m/z 201.59 [M+]. Anal. Calcd for C H NOS: C,
11 7
General procedure for synthesis of 2-phenylbenzothia-
zoles 3a–f
65.65; H, 3.51; N, 6.96. Found: C, 65.76; H, 3.58; N, 6.93.
Acknowledgment: The authors are grateful to Depart-
ment of Chemistry, MLSU for providing laboratory facili-
ties. Analytical facilities by SAIF Chandigarh are duly
acknowledged.
An aromatic aldehyde (1 mol), o-aminothiophenol (1 mmol) and urea
nitrate (15 mol%) were grounded together using a mortar and pestle
at rt for few seconds giving rise to a dramatic color change as the reac-
tion progressed. The resultant solid mass was treated with ice-cold
water and the mixture was stirred for 30 min to remove urea. After
filtration, the solid residue of 6a–f was crystallized from ethanol.
4
-(5,7-Dimethyl-benzothiazol-2-yl)-benzonitrile (3a)ꢀYield 96%; References
dark yellow crystals; mp 212–215°C; IR: 3051 (C-H stretching, Ar), 2965
−1
(
C-H stretching, CH ), 2213 (-CN, stretching) 1470 cm (aromatic C=C); [1] Kumbhare, R. M.; Kosurkar, U. B.; Ramaiah, M. J.; Dadmal, T. L.;
3
1
H NMR: δ 2.19 (s, 3H, CH ), 2.21 (s, 3H, CH ), 7.26–7.79 (m, 6H, Ar-H
Pushpavalli, S. N. C. V. L.; Bhadra, M. P. Synthesis and biologi-
cal evaluation of novel triazoles and isoxazoles linked 2-phenyl
benzothiazole as potential anticancer agents. Bioorg. Med.
Chem. Lett. 2012, 22, 5ꢋ2ꢋ–5ꢋ27.
3
3
1
3
and BT-H); C NMR: δ 20.3, 21.6, 115.9, 117.0, 124.4, 127.1, 127.5, 129.9,
1
32.3, 132.9, 134.5, 136.4, 137.3, 139.0, 153.1, 166.2; MS (EI): m/z 264.89
[
M+]. Anal. Calcd for C H N S; C, 72.70; H, 4.58; N, 10.60. Found: C,
16
12
2
7
2.53; H, 4.52; N, 10.65.
[2] Hiyoshi, H.; Goto, N.; Tsuchiya, M.; Iida, K.; Nakajima, Y.; Hirata,
N.; Kanda, Y.; Nagasawa, K.; Yanagisawa, J. 2-(ꢋ-hydroxy-
3-methoxyphenyl)-benzothiazole suppresses tumor progres-
sion and metastatic potential of breast cancer cells by inducing
ubiquitin ligase CHIP. Sci. Rep. 2014, 4, 70ꢌ5.
2
(
-(3,4-Dimethoxy-phenyl)-5,7-dimethyl-benzothiazole
3b)ꢀYield 95%; red orange crystals; mp 174–177°C; IR: 3110 (C-H
−1
stretching, Ar), 2973 (C-H stretching, CH ), 1452 cm (aromatic C=C);
3
1
H NMR: δ 2.26 (s, 3H, CH ), 2.30 (s, 3H, CH ), 3.68 (s, 3H, OCH ), 3.82 [3] Bandyopadhyay, P.; Sathe, M.; Ponmariappan, S.; Sharma, A.;
3
3
3
13
(
s, 3H, OCH ), 6.95–7.87 (m, 5H, Ar-H and BT-H); C NMR: δ 20.5, 21.8,
Sharma, P.; Srivastava, A. K.; Kaushik, M. P. Exploration of in
vitro time point quantitative evaluation of newly synthesized
benzimidazole and benzothiazole derivatives as potential
antibacterial agents. Bioorg. Med. Chem. Lett. 2011, 21,
3
5
6.2, 57.4, 111.0, 112.2, 123.4, 128.8, 130.3, 131.5, 131.9, 138.5, 138.9,
48.3, 149.1, 152.6, 166.5; MS (EI): m/z 299.47 [M+]. Anal. Calcd for
C H NO S; C, 68.20; H, 5.72; N, 4.68. Found: C, 65.30; H, 5.82; N, 4.71.
1
17
17
2
7
306–730ꢌ.
2
-Furan-2-yl-5,7-dimethyl-benzothiazole (3c)ꢀYield 98%; dark [ꢋ] Patel, N. B.; Shaikh, F. M. Synthesis and antimicrobial activity of
purple crystals; mp 182–185°C; I: 3085 (C–H stretching, Ar), 2943 (C-H
new ꢋ-thiazolidinone derivatives containing 2-amino-6-meth-
oxybenzothiazole. Saudi Pharm. J. 2010, 18, 12ꢌ–136.
−1
1
stretching, CH ), 1473 cm (aromatic C=C); H NMR: δ 2.32 (s, 3H, CH ),
3
3
2
.38 (s, 3H, CH ), 6.63 (dd, 1H, Jꢁ=ꢁ3.4, 1.8 Hz), 7.08 (d, 2H, BT-H), 7.17 [5] Cano, N. H.; Ballari, M. S.; Lopez, A. G.; Santiago, A. N. New
3
13
(
dd, 1H, Jꢁ=ꢁ3.4, 0.8 Hz), 7.87 (dd, 1H, Jꢁ=ꢁ1.8, 0.8 Hz); C NMR: δ 20.9,
synthesis and biological evaluation of benzothiazole deri-
vates as antifungal agents. J. Agric. Food Chem. 2015, 63,
3681−3686.
2
1.4, 108.8, 112.3, 122.7, 129.7, 131.0, 137.0, 138.4, 144.1, 149.1, 151.1, 156.6;
MS (EI): m/z 229.74 [M+]. Anal. Calcd for C H NOS; C, 68.09; H, 4.84;
13
11
N, 6.11. Found: C, 68.11; H, 4.93; N, 6.23.
[6] Pejchal, V.; Pejchalova, M.; Ruzickova, Z. Synthesis, structural
characterization, antimicrobial and antifungal activity of substi-
tuted 6-fluorobenzo[d]thiazole amides. Med. Chem. Res. 2015,
24, 3660–3670.
2
-(3,4-Dimethoxy-phenyl)-benzothiazole (3d)ꢀYield 98%; dark
yellow crystals; mp 136–139°C; IR: 3120 (C-H stretching, Ar), 3053
−
1
1
(
3
C-H stretching, CH ), 1465 cm (aromatic C=C); H NMR: δ 3.68 (s, [7] Zablotskaya, A.; Segal, I.; Geronikaki, A.; Eremkina, T.; Belya-
3
1
3
H, OCH ), 3.84 (s, 3H, OCH ), 6.94–7.46 (m, 7H, Ar-H and BT-H);
C
kov, S.; Petrova, M.; Shestakova, I.; Zvejniece, L.; Nikolajeva, V.
Synthesis, physicochemical characterization, cytotoxicity, anti-
microbial, anti-inflammatory and psychotropic activity of new
N-[1,3-(benzo)thiazol-2-yl]-ω-[3,ꢋ-dihydroisoquinolin-2(1H)-yl]
alkanamides. Eur. J. Med. Chem. 2013, 70, 8ꢋ6–856.
3
3
NMR: δ 56.1, 57.3, 111.6, 113.2, 122.4, 122.8, 124.9, 126.4, 128.4, 131.0,
1
34.1, 148.5, 149.1, 153.4, 163.5; MS (EI): m/z 271.82 [M+]. Anal. Calcd
for C H NO S; C, 66.40; H, 4.83; N, 5.16. Found: C, 66.57; H, 4.93; N,
1
5
13
2
5
.26.
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