8
S. R. MATHAPATI ET AL.
ꢁ
1
purified by recrystallization with hot ethanol and by passing 120.30, 115.04, 111.75, 110.25; IR (KBr, in cm ): 2945,
sample through a short column of silica gel when- 2886, 1715, 1624, 1574, 1460, 1378, 1221, 1070, 760, 582;
ever required.
Mass (m/z): 186 [M þ 1].
-Phenyl benzothiazole (3o)- (Purity- 95%): H NMR
CDCl , in d ppm): 8.20-8.16 (m, 3H), 7.80 (d, 1H,
1
2
(
3
Spectral data of selective synthesized products
13
J ¼ 8.0 Hz), 7.55-7.50 (m, 4H), 7.38-7.34 (m, 1H); C NMR
1
(
CDCl , in d ppm): 169.20, 155.02, 135.09, 133.90, 132.04,
2
-Phenyl- 1H-benzimidazole (3a)- (Purity- 97%): H-NMR
3
1
30.12, 128.24, 126.80, 124.92, 123.44, 121.90; IR (KBr, in
(
(
DMSO-d , in d ppm): 8.20 (d, 2H, J ¼ 6.0 Hz), 7.65-7.59
6
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1
cm ): 3103, 2940, 1660, 1487, 1365, 1238, 875, 754, 682;
m, 4H), 7.50-7.48 (m, 1H), 7.22 (m, 2H), 5.20 (s, 1H, NH);
1
3
Mass (m/z): 212 [M þ 1].
C-NMR (DMSO-d , in d ppm): 113.26, 118.68, 122.71,
6
1
2
-(4-Chlorophenyl)benzothiazole (3q)- (Purity- 94%): H
1
1
1
23.90, 125.69, 129.20, 129.89, 130.84, 135.11, 145.52,
52.50. IR (KBr, in cm ): 3220, 2280, 1672, 1400, 1275,
119, 970, 738; Mass (m/z): 194 [M ].
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1
NMR (CDCl , in d ppm): 8.20 (d, J ¼ 8.4 Hz, 1H), 8.15 (d,
3
þ
J ¼ 8.0 Hz, 2H), 7.90 (d, J ¼ 8.5 Hz, 1H), 7.48–7.33 (m, 4H);
13
C NMR (CDCl , in d ppm): 168.02, 155.45, 137.71, 134.98,
2
-(2- Hydroxyphenyl)-1H- benzimidazole (3e)- (Purity-
3
1
1
32.60, 130.01, 128.58, 125.29, 124.89, 123.6, 120.78; IR
9
1
7
4
8%): H NMR (DMSO-d , in d ppm): 7.92 (dd, 1H, J ¼ 7.6,
6
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1
(KBr, in cm ): 3119, 3025, 1654, 1593, 1463, 1248, 864,
.4 Hz), 7.78 (d, 1H, J ¼ 7.6 Hz), 7.65 (d, 1H, J ¼ 7.4 Hz),
.48 ꢁ 7.40 (m, 1H), 7.32–7.26 (m, 2H), 7.10–7.06 (m, 2H)),
þ
6
82; Mass (m/z): 245 [M ].
1
1
3
2
-Ethylbenzothiazole (3t)- (Purity- 94%): H NMR
.91 (brs, 1H, OH), 5.19 (s, 1H, NH); C NMR (DMSO-d ,
6
(
1
CDCl in d ppm): 8.05 (d, J ¼ 8.2 Hz, 1H), 7.85 (dd, J ¼ 8.2,
in d ppm): 156.18, 149.80, 140.55, 135.10, 132.05, 131.79,
29.55, 128.71, 127.64, 124.04, 123.18, 121.19, 117.09; IR
3
.2 Hz, 1H), 7.52-7.45 (m, 1H), 7.30-7.21 (m, 1H), 3.06 (q,
1
13
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1
J ¼ 7.4, 2H), 1.50 (t, J ¼ 7.4, 3H); C NMR (CDCl , in d
(KBr, in cm ): 3560, 3390, 2185, 1640, 1610, 1090, 940,
3
þ
ppm): 168.20, 150.12, 138.64, 124.85, 124.60, 121.89, 119.05,
7
62; Mass (m/z): 211 [M ].
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1
2
1
1
7.41, 12.08; IR (KBr, in cm ): 3404, 2980, 2942, 2880,
2
-(Furan-2-yl)-1H-benzo[d]imidazole (3 g)- (Purity-
1
560, 1485, 1420, 1296, 1052, 940, 767, 685; Mass (m/z):
9
,
2
7%): H NMR (DMSO-d , in d ppm): 7.96 (d, 1H, J ¼ 1.2)
6
þ
64 [M þ 1 ].
7.65 (d, 1H, J ¼ 6.4), 7.52 (d, 1H, J ¼ 6.4 Hz), 7.30-7.21 (m,
1
1
3
2
-(Furan-2-yl)-benzothiazole (3 u)- (Purity- 95%):
H
H), 6.92-6.80 (m, 2H), 5.24 (s, 1H, NH); C NMR
NMR (CDCl in d ppm): 8.47 (d, J ¼ 8.4 Hz, 1H), 8.02 (d,
(
DMSO-d , in d ppm): 145.84, 144.86, 143.60, 140.03,
3
6
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1
J ¼ 8.0 Hz, 1H), 7.87 (d, J ¼ 3.5 Hz, 1H), 7.62 (dd, J ¼ 14.3,
1
2
5
22.48, 115.30, 112.93, 109.97; IR (KBr, in cm ): 3408,
927, 2860, 1700, 1619, 1555, 1462, 1380, 1201, 1071, 768,
85; Mass (m/z): 184 [M ].
1
3
6
.8 Hz, 2H), 7.40 (t, J ¼ 7.6 Hz, 1H), 7.20-7.12 (m, 1H);
C
þ
NMR (CDCl , in d ppm): 158.25, 153.72, 148.76, 144.70,
3
1
1
34.26, 126.47, 125.11, 123.30, 121.51, 112.55, 111.40; IR
2
-Phenyl benzoxazole (3 h)- (Purity- 95%): H NMR
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1
(KBr, in cm ): 2982, 2860, 1704, 1645, 1564, 1470, 1367,
(
CDCl , in d ppm): 8.30-8.24 (m, 2H), 7.79-7.73 (m, 1H),
3
þ
13
1
222, 1044, 785, 578; Mass (m/z): 202 [M ].
7
.58-7.53 (m, 1H), 7.46-7.39 (m, 3H), 7.35-7.30 (m, 2H);
C
NMR (CDCl , in d ppm): 163.70, 152.02, 142.51, 132.06,
3
1
29.10, 128.34, 127.20, 125.09, 123.98, 120.40, 111.05; IR
Conclusions
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1
(
(
KBr, in cm ): 3452, 2920, 1622, 1565, 1260, 756; Mass
m/z): 196 [M þ 1].
In summary, we demonstrated that fluorophosphoric acid
1
2
-(3-Methoxyphenyl)benzoxazole (3k)- (Purity- 94%): H catalyst offered an efficient, selective route to synthesize ser-
NMR (CDCl in d ppm): 7.80-7.71 (m, 3H), 7.62-7.56 (m, ies of benzimidazoles, benzoxazoles and benzothiazoles from
3
1
H), 7.42 (t, 1H, J ¼ 8.2 Hz), 7.36-7.30 (m, 2H), 7.08-6.95 1, 2-phenylenediamine, o-aminophenol and o-aminothiophe-
13
(
m, 1H), 3.86 (s, 3H); C NMR (CDCl , in d ppm): 164.20, nol with aliphatic, aromatic as well as heterocyclic alde-
3
1
1
3
6
62.01, 151.29, 144.02, 131.26, 127.69, 124.58, 123.89, hydes. The study suggested that 5 mol% fluorophosphoric
19.32, 118.98, 117.57, 110.09, 55.87. IR (KBr, in cm ): acid could effectively catalyzed these reactions in ethanol
005, 2962, 2865, 1660, 1504, 1480, 1254, 1084, 780, 669, solvent at room temperature in just reaction time of 2.2-
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1
30; Mass (m/z): 226.23 [M þ 1].
4.2 h with admirable yields. The high yields obtained are
comparable to those reported in the literature. Additionally,
1
2
-isopropylbenzo[d]oxazole (3 m)- (Purity- 94%):
H
NMR (CDCl , in d ppm): 7.82 (d, 1H, J ¼ 8.0 Hz), 7.67 (d, as compared with the works reported for the synthesis of
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1
H, J ¼ 8.2 Hz), 7.51–7.39 (m, 2H), 3.42-3.36 (hept, 1H, series of benzimidazoles, benzoxazoles and benzothiazoles,
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3
J ¼ 6.8 Hz), 1.50 (d, 6H, J ¼ 6.8 Hz); C NMR (CDCl , in d the present work holds certain merits. Precisely, the fluoro-
3
ppm): 176.48, 152.19, 143.0, 126.32, 124.81, 121.95, 119.89, phosphoric acid could be considered as inexpensive catalyst
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1
3
1
1
3.49, 21.97. IR (KBr, in cm ): 3135, 2954, 2902, 2862, in comparison to that of metal-based catalyst. There are sev-
648, 1542, 1500, 1264, 1063, 778, 670; Mass (m/z): eral problems associated with of metal-based catalyst such as
62 [M þ 1].
-(furan-2-yl)benzoxazole (3n)- (Purity- 96%): H NMR stable and offered the required acidity for driving the reac-
CDCl in d ppm): 7.75-7.69 (m, 1H), 7.58-7.55 (m, 1H), tion into the forward direction. Therefore, reported protocol
stability and acidity. Conversely, fluorophosphoric acid is
1
2
(
3
7
.48-7.43 (m, 1H), 7.35-7.29 (m, 2H), 7.18 (d, 1H, could be considered as an efficient, inexpensive synthetic
1
3
J ¼ 3.8 Hz), 6.60-6.58 (m, 1H); C NMR (CDCl , in d approach for producing moderate to excellent yields of tar-
3
ppm): 155.28, 150.51, 148.00, 141.89, 139.75, 125.38, 123.99, geted molecules not only at academic level but also can be