D. Singh, S.R. Chowdhury, S. Pramanik et al.
Tetrahedron xxx (xxxx) xxx
concentrated in a rotary evaporator and the residue was purified by
silica gel column chromatography with a plug of neutral alumina to
the top of the column to afford the desired 3-methylthiolated
imidazo[1,2-a]pyridine product.
124.5, 116.3, 115.5, 111.9, 107.5.
2-(3-bromophenyl)imidazo[1,2-a]pyridine (Tables 3 and 3h).
[7f] Light yellow Solid; mp 129e131 C; 61% yield (33 mg); R
ꢀ
f
1
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR
(
400 MHz, CDCl (ppm) 8.12e8.09 (m, 2H), 7.87e7.84 (m, 2H),
3
) d
4
.4. Characterization data of products
7.63e7.61 (m, 1H), 7.44 (ddd, J ¼ 8.3, 1.8, 1.0 Hz, 1H), 7.29 (t,
J ¼ 7.9 Hz, 1H), 7.18 (ddd, J ¼ 9.1, 6.8, 1.3 Hz, 1H), 6.78 (td, J ¼ 6.8,
13
1
2
-phenylimidazo[1,2-a]pyridine (Tables 3 and 3a) [7f]. Light
3
1.0 Hz, 1H); C{ H} NMR (101 MHz, CDCl ) d (ppm) 145.8, 144.3,
ꢀ
yellow Solid; mp 135e137 C; 62% yield (24 mg); R
f
value ¼ 0.3
135.9, 130.9,130.4,129.1,125.8,125.2,124.6,123.1,117.7, 112.8,108.6.
1
[
d
EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR (400 MHz, CDCl
3
)
2-(3-nitrophenyl)imidazo[1,2-a]pyridine (Tables 3 and 3i).
ꢀ
(ppm) 8.10 (d, J ¼ 6.8 Hz, 1H), 7.96 (d, J ¼ 7.4 Hz, 2H), 7.85 (s, 1H),
.63 (d, J ¼ 9.1 Hz, 1H), 7.44 (t, J ¼ 7.6 Hz, 2H), 7.33 (t, J ¼ 7.4 Hz, 1H),
[7h] Yellow Solid; mp 201e202 C; 74% yield (35 mg); R
f
value ¼ 0.3
1
7
7
[EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR (400 MHz, CDCl
(ppm) 8.78 (s, 1H), 8.35 (d, J ¼ 7.7 Hz, 1H), 8.19 (d, J ¼ 7.0 Hz, 2H),
8.01 (s, 1H), 7.68 (d, J ¼ 9.1 Hz, 1H), 7.63 (t, J ¼ 8.0 Hz, 1H), 7.27 (dd,
3
)
13
1
.18e7.13 (m, 1H), 6.76 (t, J ¼ 6.6 Hz, 1H); C{ H} NMR (101 MHz,
d
3
CDCl ) d (ppm) 145.9, 145.8, 133.8, 128.9, 128.1, 126.2, 125.7, 124.8,
13
1
117.6, 112.6, 108.2.
J ¼ 15.4, 7.7 Hz, 1H), 6.87 (t, J ¼ 6.7 Hz, 1H); C{ H} NMR (101 MHz,
2
-(4-methoxyphenyl)imidazo[1,2-a]pyridine (Tables 3 and
CDCl (ppm) 147.8, 145.0, 142.5, 134.8, 130.9, 128.8, 125.0, 124.6,
3
) d
ꢀ
3
b) [7f]. Yellowish solid; mp 133e135 C; 77% yield (34 mg); R
f
121.6, 119.9, 116.9, 112.2, 108.2.
1
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR
2-(naphthalen-1-yl)imidazo[1,2-a]pyridine (Tables 3 and 3j).
ꢀ
(
400 MHz, CDCl
3
)
d
(ppm) 8.06 (dt, J ¼ 6.8,1.2 Hz,1H), 7.90e7.86 (m,
[7f] Light yellow Solid; mp 158e160 C; 47% yield (23 mg); R
f
1
2
1
H), 7.75 (s, 1H), 7.60 (d, J ¼ 9.6 Hz,1H), 7.13 (ddd, J ¼ 9.2, 6.8, 1.2 Hz,
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR
13
H), 6.98e6.94 (m, 2H), 6.73 (td, J ¼ 6.8, 1.1 Hz, 1H), 3.84 (s, 3H);
C
(400 MHz, CDCl
3
)
d
(ppm) 8.63e8.61 (m, 1H), 8.14 (dt, J ¼ 6.8,1.1 Hz,
1
{
H} NMR (101 MHz, CDCl
3
)
d
(ppm) 159.7, 145.8, 145.7, 127.4, 126.6,
1H), 7.92e7.87 (m, 2H), 7.83 (dd, J ¼ 6.7, 1.4 Hz, 2H), 7.71 (d,
J ¼ 9.5 Hz, 1H), 7.57e7.55 (m, 1H), 7.53e7.50 (m, 2H), 7.20 (ddd,
125.6, 124.6, 117.4, 114.2, 112.3, 107.3, 55.4.
13
1
2
-(2-methoxyphenyl)imidazo[1,2-a]pyridine (Table 3 and 3c)
J ¼ 9.1, 6.7, 1.2 Hz, 1H), 6.79 (td, J ¼ 6.8, 0.9 Hz, 1H); C{ H} NMR
ꢀ
[
7f]. Light yellow Solid; mp 94e96 C; 41% yield (18 mg); R
f
3
(101 MHz, CDCl ) d (ppm) 145.5, 145.3, 134.0, 131.9, 131.6, 128.5,
1
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 2:3 (v/v)]; H NMR
400 MHz, CDCl
(ppm) 8.41 (dd, J ¼ 7.7, 1.8 Hz, 1H), 8.18 (s, 1H),
.10 (d, J ¼ 6.8 Hz, 1H), 7.61 (dd, J ¼ 9.2, 0.7 Hz, 1H), 7.31 (ddd,
J ¼ 8.2, 7.4, 1.9 Hz, 1H), 7.15e7.09 (m, 2H), 7.00 (dd, J ¼ 8.3, 0.6 Hz,
128.4,127.8,126.5,126.0,125.9,125.6,125.5,124.7,117.8,112.5,111.3.
(
8
3
)
d
2-(pyridin-2-yl)imidazo[1,2-a]pyridine (Tables 3 and 3k). [25]
ꢀ
Brown yellow Solid; mp 135e137 C; 33% yield (13 mg); R
f
1
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR
13
1
1
(
1
H), 6.72 (td, J ¼ 6.8, 0.9 Hz, 1H), 3.98 (s, 3H); C{ H} NMR
101 MHz, CDCl (ppm): 156.8, 144.5, 141.2, 128.9, 128.7, 125.7,
24.6, 122.4, 121.1, 117.3, 112.6, 112.1, 110.9, 55.5.
(400 MHz, CDCl (ppm) 8.62e8.60 (m, 1H), 8.24 (s, 1H), 8.18 (d,
3
) d
3
)
d
J ¼ 8.0 Hz, 1H), 8.13 (d, J ¼ 6.8 Hz, 1H), 7.77 (td, J ¼ 7.8, 1.8 Hz, 1H),
7.65e7.62 (m, 1H), 7.23e7.15 (m, 2H), 6.78 (td, J ¼ 6.8, 0.8 Hz, 1H);
13
1
2
-(3,4-dimethoxyphenyl)imidazo[1,2-a]pyridine (Tables
3
3
C{ H} NMR (101 MHz, CDCl ) d (ppm) 152.7, 149.4, 137.2, 130.0,
ꢀ
and 3d). [7g] Yellow Solid; mp 104e106 C; 47% yield (24 mg); R
f
128.4, 126.2, 125.4, 122.9, 120.8, 117.8, 113.0, 111.1.
1
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 1:1 (v/v)]; H NMR
2-(thiophen-2-yl)imidazo[1,2-a]pyridine Tables 3 and 3l). [7f]
ꢀ
(
400 MHz, CDCl
3
)
d
(ppm) 8.09 (d, J ¼ 6.7 Hz, 1H), 7.79 (s, 1H), 7.61
Yellowish Solid; mp 136e138 C; 39% yield (16 mg); R
f
value ¼ 0.3
1
(
d, J ¼ 9.1 Hz, 1H), 7.57 (d, J ¼ 1.7 Hz, 1H), 7.44 (dd, J ¼ 8.3, 1.8 Hz,
[EtOAc: Petroleum ether ¼ 2:8 (v/v)]; H NMR (400 MHz, CDCl
(ppm) 8.05 (dd, J ¼ 6.8, 0.8 Hz, 1H), 7.74 (s, 1H), 7.59 (d, J ¼ 9.2 Hz,
1H), 7.46 (d, J ¼ 3.5 Hz, 1H), 7.29 (d, J ¼ 5.0 Hz, 1H), 7.17e7.12 (m,
3
)
1
1
d
H), 7.15 (t, J ¼ 8.2 Hz, 1H), 6.92 (d, J ¼ 8.3 Hz, 1H), 6.75 (t, J ¼ 6.7 Hz,
d
13
1
H), 3.99 (s, 3H), 3.92 (s, 3H); C{ H} NMR (101 MHz, CDCl
(ppm) 149.3, 149.1, 145.8, 145.6, 126.9, 125.6, 124.7, 118.6, 117.4,
12.5, 111.4, 109.3, 107.6, 56.1, 56.0.
3
)
1
3
1
1H), 7.08 (dd, J ¼ 5.0, 3.7 Hz, 1H), 6.75 (t, J ¼ 6.7 Hz, 1H); C{ H}
1
NMR (101 MHz, CDCl (ppm) 145.5, 140.8, 137.5, 127.9, 125.5,
3
) d
2
-(4-fluorophenyl)imidazo[1,2-a]pyridine (Tables 3 and 3e).
125.1, 125.0, 123.8, 117.3, 112.7, 107.5.
ꢀ
[
7f] Brown yellow Solid; mp 156e158 C; 60% yield (25 mg); R
f
2-(furan-2-yl)imidazo[1,2-a]pyridine (Tables 3 and 3m). [7f]
1
ꢀ
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR
400 MHz, CDCl
(ppm) 8.10 (d, J ¼ 6.7 Hz,1H), 7.93e7.90 (m, 2H),
.79 (s, 1H), 7.62 (d, J ¼ 9.1 Hz, 1H), 7.19e7.15 (m, 1H), 7.12 (t,
Brown black Solid; mp 88e90 C; 36% yield (13 mg); R
f
value ¼ 0.3
1
(
7
3
)
d
[EtOAc: Petroleum ether ¼ 2:8 (v/v)]; H NMR (400 MHz, CDCl
3
)
d
(ppm) 8.11 (d, J ¼ 6.8 Hz, 1H), 7.80 (s, 1H), 7.61e7.59 (m, 1H),
13
1
J ¼ 8.7 Hz, 2H), 6.77 (t, J ¼ 6.7 Hz, 1H); C{ H} NMR (101 MHz,
CDCl
(ppm) 162.9 (d, J ¼ 247.4 Hz), 145.8, 145.0, 130.0, 127.9 (d,
J ¼ 8.5 Hz), 125.7, 125.0, 117.6, 115.8 (d, J ¼ 22.0 Hz), 112.7, 107.9;
NMR (376 MHz, CDCl
7.48e7.47 (m, 1H), 7.18 (ddd, J ¼ 9.1, 6.8, 1.3 Hz, 1H), 6.89 (d,
J ¼ 3.4 Hz, 1H), 6.79 (td, J ¼ 6.8, 1.0 Hz, 1H), 6.51 (dd, J ¼ 3.3, 1.8 Hz,
3
) d
19
13
1
F
3
1H); C{ H} NMR (101 MHz, CDCl ) d (ppm) 149.6, 145.7, 142.2,
3
)
d
(ppm): ꢂ114.1 (s, 1F).
137.9, 125.8, 125.2, 117.4, 112.7, 111.7, 108.0, 106.9.
2
-(4-bromophenyl)imidazo[1,2-a]pyridine (Tables 3 and 3f).
2-phenyl-3-propylimidazo[1,2-a]pyridine (Tables 3 and 3n).
ꢀ
[
[
d
7f] Yellow Solid; mp 210e212 C; 65% yield (35 mg); R
f
value ¼ 0.3
[26] Pale yellow oil; 23% yield (11 mg); R
f
value ¼ 0.3 [EtOAc: Pe-
1
1
EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR (400 MHz, CDCl
(ppm) 8.10 (dt, J ¼ 6.8, 1.1 Hz, 1H), 7.83e7.82 (m, 2H), 7.80 (d,
J ¼ 1.9 Hz, 1H), 7.62e7.60 (m, 1H), 7.56e7.53 (m, 2H), 7.18 (ddd,
3
)
troleum ether ¼ 3:7 (v/v)]; H NMR (400 MHz, CDCl
3
) d
(ppm) 7.95
(d, J ¼ 6.9 Hz, 1H), 7.78 (dd, J ¼ 8.3, 1.0 Hz, 2H), 7.64 (d, J ¼ 8.9 Hz,
1H), 7.46 (t, J ¼ 7.6 Hz, 2H), 7.37e7.33 (m, 1H), 7.16 (ddd, J ¼ 9.1, 6.8,
1.3 Hz, 1H), 6.81 (td, J ¼ 6.8, 1.2 Hz, 1H), 3.06e3.02 (m, 2H), 1.76 (dd,
13
1
J ¼ 8.9, 6.8, 1.2 Hz, 1H), 6.78 (td, J ¼ 6.8, 0.9 Hz, 1H); C{ H} NMR
101 MHz, CDCl (ppm) 145.8, 144.7, 132.8, 131.9, 127.6, 125.7,
25.1, 122.0, 117.6, 112.8, 108.4.
13
1
(
1
3
)
d
J ¼ 15.6, 7.6 Hz, 2H), 1.05 (t, J ¼ 7.4 Hz, 3H); C{ H} NMR (101 MHz,
3
CDCl ) d (ppm) 144.5, 142.4, 135.0, 128.6, 128.3, 127.5, 123.6, 123.1,
4
-(imidazo[1,2-a]pyridin-2-yl)phenol (Tables 3 and 3g). [22b]
120.8, 117.7, 112.1, 25.9, 21.2, 14.3.
2,3-diphenylimidazo[1,2-a]pyridine (Tables 3 and 3o). [7f]
Light yellow solid; mp 149e151 C; 22% yield (12 mg); R
ꢀ
Brown Solid; mp 142e144 C; 41% yield (17 mg); R
f
value ¼ 0.3
1
ꢀ
[
d
EtOAc: Petroleum ether ¼ 1:1 (v/v)]; H NMR (400 MHz, DMSO‑d
6
)
f
1
(ppm): 9.54 (s,1H), 8.48 (dt, J ¼ 6.8,1.1 Hz,1H), 8.21 (s,1H), 7.77 (d,
value ¼ 0.3 [EtOAc: Petroleum ether ¼ 3:7 (v/v)]; H NMR
(400 MHz, CDCl
(ppm) 7.97 (d, J ¼ 6.9 Hz,1H), 7.71e7.65 (m, 3H),
7.55e7.45 (m, 5H), 7.31e7.27 (m, 3H), 7.25e7.19 (m, 1H), 6.75 (td,
J ¼ 8.6 Hz, 2H), 7.53e7.51 (m, 1H), 7.20 (ddd, J ¼ 9.2, 6.7, 1.2 Hz, 1H),
3
) d
13
1
6
(
.86 (dd, J ¼ 6.8, 1.0 Hz, 1H), 6.82 (d, J ¼ 8.7 Hz, 2H); C{ H} NMR
13
1
101 MHz, DMSO‑d (ppm): 157.3, 144.9, 144.6, 126.1, 126.6, 124.9,
6
)
d
J ¼ 6.8, 0.9 Hz, 1H); C{ H} NMR (101 MHz, CDCl
3
) d (ppm) 144.1,
6