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M. KADAGATHUR ET AL.
Pure product 3 was obtained by silica gel column chromatography using EtOAc and
hexane (1:9) as eluent. All the synthesized compounds were thoroughly characterized by
1
IR, H NMR, 13C NMR and HRMS (ESI).
N-Phenylbenzo[d]oxazol-2-amine (3a).[27] 98% yield; Off-white solid; mp:
1
175–177 ꢀC. H NMR (500 MHz, DMSO-d6) d 10.63 (s, 1H), 7.77 (dd, J ¼ 8.6, 0.9 Hz,
2H), 7.48 (dd, J ¼ 16.2, 8.0 Hz, 2H), 7.41 ꢁ 7.36 (m, 2H), 7.23 (dt, J ¼ 7.7, 1.0 Hz, 1H),
7.14 (dt, J ¼ 7.8, 1.2 Hz, 1H), 7.04 (t, J ¼ 7.4 Hz, 1H). 13C NMR (125 MHz, DMSO-d6) d
158.5, 147.5, 142.9, 139.2, 129.5, 124.5, 122.6, 122.1, 118.1, 117.1, 109.4. HRMS (ESI):
m/z [M þ H]þ calcd for C13H11N2O 211.0885; found 211.0866.
General procedure for the synthesis of 2-Aminobenzimidazoles 5a–d
o-Phenylenediamine (1) (1 mmol), aryl isothiocyanate (2) (1 equiv) and H2O2 (30% in
H2O) (4.5 equiv) in ethanol (2 mL) were placed in an oven-dried microwave reaction
tube. The reaction vessel was then sealed with the cap and stirred at 100 ꢀC under
microwave irradiation for 10 min. After completion of the reaction, the reaction mixture
was cooled to room temperature, to which water was added and extracted with ethyl
acetate. The organic layer was then dried over anhydrous Na2SO4 and evaporated under
vacuum. Pure product 5 was obtained by silica gel column chromatography using
EtOAc and hexane (3:7) as eluent. All the synthesized compounds were thoroughly
1
characterized by IR, H NMR, 13C NMR and HRMS (ESI).
N-Phenyl-1H-benzo[d]imidazol-2-amine (5a).[36] 85% yield; Brown solid; mp:
1
188–191 ꢀC. H NMR (500 MHz, DMSO-d6) d 11.00 (s, 1H), 9.44 (s, 1H), 7.76 (d,
J ¼ 6.6 Hz, 2H), 7.32 (s, 4H), 7.01 (s, 2H), 6.94 (s, 1H). 13C NMR (125 MHz, DMSO-d6)
d 151.0, 141.3, 129.3, 121.1, 120.6, 117.6. HRMS (ESI): m/z [M þ H]þ calcd for
C13H11N3 210.1026; found 210.1029.
Procedure for the synthesis of 2-aminobenzothiazole 7
2-Aminothiophenol (6a) (1 mmol), phenyl isothiocyanate (2a) (1 equiv) and H2O2 (30%
in H2O) (4.5 equiv) in ethanol (2 mL) were placed in an oven-dried microwave reaction
tube. The reaction vessel was then sealed with the cap and stirred at 100 ꢀC under
microwave irradiation for 10 min. After completion of the reaction, the reaction mixture
was cooled to room temperature, to which water was added and extracted with ethyl
acetate. The organic layer was then dried over anhydrous Na2SO4 and evaporated under
vacuum. Pure product 7 was obtained by silica gel column chromatography using
EtOAc and hexane (1:9) as eluent. The synthesized compound was thoroughly charac-
1
terized by IR, H NMR, 13C NMR and HRMS (ESI).
N-Phenylbenzo[d]thiazol-2-amine (7).[27] 98% yield; Off-white solid; mp:
136–139 ꢀC.1H NMR (500 MHz, DMSO-d6) d 10.49 (s, 1H), 7.81 (d, J ¼ 8.2 Hz, 3H),
7.62 (d, J ¼ 7.9 Hz, 1H), 7.38 (dd, J ¼ 8.4, 7.5 Hz, 2H), 7.35 ꢁ 7.31 (m, 1H), 7.21 ꢁ 7.10
(m, 1H), 7.03 (t, J ¼ 7.3 Hz, 1H). 13C NMR (125 MHz, DMSO-d6) d 177.5, 164.3, 148.1,
142.1, 130.4, 129.3, 128.3, 127.4, 125.1, 123.6, 120.6. HRMS (ESI): m/z [M þ H]þ calcd
for C13H11N3 210.1026; found 210.1029.