SYNTHESIS OF 2-(4-AMINOPHENYL)BENZOTHIAZOLES
681
were performed on a Perkin-Elmer Model 240 analy-
tical apparatus. MW irradiation was performed in an
unmodified Galanz WD 900M domestic microwave
oven. All compounds were purified by thick layer
chromatography using silica gel from Merck.
(DMSO-d6), δ, ppm: 7.85 s (Ar-H), 7.80 d (J = 4.8 Hz,
2H, Ar-H), 7.35 d (J = 2.4 Hz, Ar-H), 7.04 m (3H, Ar-H),
3.98 s (2H, NH2), 3.85 s (3H, OCH3). MS (ESI): m/z
256.07 (calculated), 257.08 [M + H]+ (found).
Calculated, %: C 65.60; H 4.72; N 10.93. C14H12N2OS.
Found, %: C 65.35; H 4.90; N 10.67.
Preparation of MF-supported sulfuric acid.
Polymer-supported reagent was prepared according to
the previously reported method [12]. To a solution of
melamine–formaldehyde resin (6 g) in 60mL of
acetone commercial sulfuric acid (98%, 6 mL) was
added dropwise over a period of 30 min at room
temperature. The precipitate was filtered off and dried
in vacuum.
4-(6-Ethyl-benzothiazol-2-yl)-phenylamine
(IIId). Yellow solid, 83%; mp 153–155°C; IR (KBr),
ν, cm–1: 3306, 3198, 1634, 1609, 830.1H NMR spectra
(DMSO-d6), δ, ppm: 7.86 m (3H, Ar-H), 7.65 d (J =
0.4 Hz, Ar-H), 7.25 d (J = 7.6 Hz, Ar-H), 6.80 d (J =
4.8 Hz, 2H, Ar-H), 3.98 s (2H, NH2) 2.76 (q, 2H,
CH2), 1.29 t (3H, CH3). MS (ESI): m/z 254.09
(calculated), 255.09 [M + H]+ (found). Calculated, %:
70.83; H 5.55; N 11.01. C15H14N2S. Found, %: C
70.62; H 5.30; N 10.90.
Compounds IIIa–IIIg (general procedure). To a
solution of o-aminothiophenol (Ia–Id, 5 mmol) and
(un)substituted p-aminobenzoic acid (IIa–IIe, 10 mmol)
in diethyl ether (10 mL) was added MFR-supported
sulfuric acid (IIIg). The slurry was mixed thoroughly
and the solvent was removed by rotary evaporation.
The resulting solid was irradiated in a MW oven at
900 W for 6–8 min. On completion of the process, the
reaction mixture was cooled down to room tem-
perature and ethanol (20 mL) was added. The
suspended resin was isolated by filtration and washed
with diethyl ether. The filtrate was concentrated under
reduced pressure and subjected to chromatography on
silica gel to afford the products IIIa–IIIj.
4-Benzothiazol-2-yl-2-methyl-phenylamine
(IIIe). Yellow solid, 85%; mp 145–147°C; IR(KBr), ν,
cm–1: 3304, 3205, 1637, 1614, 830.1H NMR spectra
(DMSO-d6), δ, ppm: 7.99 m (Ar-H), 7.83 m (2H, Ar-H),
7.75 d (J = 8.0 Hz, Ar-H), 7.43 d (J = 8.0 Hz, Ar-H),
7.31 d (J = 8.0 Hz, Ar-H), 6.71 d (J = 8.0 Hz, Ar-H),
3.94 s (2H, NH2), 2.23 s (3H, CH3). MS (ESI): m/z
240.07 (calculated), 241.07 [M + H]+ (found).
Calculated, %: 69.97; H 5.03; N 11.66. C14H12N2S.
Found, %: C 69.83; H 5.03; N 11.72.
4-Benzothiazol-2-yl-2-chlorophenylamine (IIIf).
4-Benzothiazol-2-yl phenylamine (IIIa). Yellow
solid, 87%, mp 130–132°C; IR (KBr), ν, cm–1: 3300,
White solid, 83%; mp 185–187°C; IR (KBr), ν, cm–1:
1
3450, 3295, 1627, 1474, 1224, 750. H NMR spectra
1
3200, 1635, 1610, 830. H NMR spectra spectra
(DMSO-d6), δ, ppm: 8.09 m ( Ar-H), 8.03 m (Ar-H),
7.85 d (J = 8.0 Hz, Ar-H), 7.79 d (J = 8.0 Hz, Ar-H),
7.53 d (J = 8.0 Hz, Ar-H), 7.37 d (J = 8.0 Hz, Ar-H),
6.81 d (J = 8.0 Hz, Ar-H), 4.44(s, 2H, NH2). MS (ESI):
m/z 260.02 (calculated), 259.02 [M – H]–, 261.02, [M –
H + 2] (found). Calculated, %: 59.88; H 3.48; N 10.74.
C13H9ClN2S. Found, %: C 59.80; H 3.53; N 10.68.
(DMSO-d6), δ, ppm: 7.92 m (3H, Ar-H), 7.84 m (1H,
Ar-H), 7.44 m (1H, Ar-H), 7.32 m (1H, Ar-H), 6.72 d
(J = 4.2 Hz, 2H, Ar-H), 4.00 s (2H, NH2). MS (ESI):
m/z 226.05 (calculated), 227.05, [M + H]+ (found).
Calculated, %: 69.00; H 4.45; N 12.38. C13H10N2S.
Found, %: C 69.03; H 4.69; N 12.29.
4-(6-Methylbenzothiazol-2-yl)phenylamine (IIIb).
Yellow solid; 86%; mp 180–182°C; IR (KBr), ν, cm–1:
3302, 3199, 1636, 1610, 830. 1H NMR spectra
(DMSO-d6), δ, ppm: 7.85 m (3H, Ar-H), 7.63 s (Ar-H),
7.28 m (2H, Ar-H), 6.71 m (Ar-H), 4.00 s (2H, NH2),
2.46 s (3H, CH3). MS (ESI): m/z 240.07 (calculated),
241.08, [M + H]+ (found). Calculated, %: C 69.97; H
5.03; N 11.66. C14H12N2S. Found, %: C 69.84; H 5.01;
N 11.70.
4-Benzothiazol-2-yl-2-bromophenylamine (IIIg).
White solid, 81%; mp 162–164°C; IR (KBr), ν, cm–1:
1
3440, 3291, 1625, 1476, 1320, 1225, 754; H NMR
spectra (DMSO-d6), δ, ppm: 8.05 m (2H, Ar-H), 7.95 d
(J = 8.0 Hz, Ar-H), 7.78 d (J = 8.0 Hz, Ar-H), 7.50 d
(J = 8.0 Hz, Ar-H), 7.39 d (J = 8.0 Hz, Ar-H), 6.91 d
(J = 8.0 Hz, Ar-H), 6.14 s (2H, NH2). MS (ESI): m/z
305.19 (calculated), 304.19, [M – H]–, 306.18, [M –
H + 2] (found). Calculated, %: 51.16; H 2.97; N 9.18.
C13H9BrN2S. Found, %: C 51.08; H 3.03; N 9.22%.
4-(6-Methoxy-benzothiazol-2-yl)-phenylamine
(IIIc). Yellow solid, 88%; mp 174–176°C; IR(KBr), ν,
4-Benzothiazol-2-yl-2-iodophenylamine (IIIh).
1
cm–1: 3300, 3200, 1635, 1607, 830. H NMR spectra
Yellow solid, 84%; mp 165–167°C; IR (KBr), ν, cm–1:
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 3 2015