Synthesis of Imidazo[1,2-a]pyridines
J. Chin. Chem. Soc., Vol. 51, No. 6, 2004 1379
(KBr) n: 1630 cm-1; 1H NMR (CDCl3) d: 6.8 (dt, J = 1.2, 6.8
Hz, 1H), 7.19 (d, J = 8.0 Hz, 1H), 7.41 (d, J = 8.8 Hz, 2H),
7.63 (d, J = 9.0 Hz, 1H), 7.85 (s, 1H), 7.90 (d, J = 8.8 Hz, 2H),
8.13 (d, J = 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) d:
108.1, 112.5, 117.4, 124.9, 125.5, 127.2, 128.8, 132.1, 133.6,
144.5, 145.6; EI-MS m/z (relative intensity) 230 (M++2), 228
(M+), 193, 192, 114, 89, 78, 75, 63, 51.
6-Chloro-2-phenylimidazo[1,2-a]pyridine (3j)
mp 200-201 °C (lit.18 mp 201-202 °C), yield 77%. IR
(KBr) n: 1671 cm-1; 1H NMR (CDCl3) d: 7.23-7.24 (m, 1H),
7.38 (t, J = 7.2 Hz, 1H), 7.44-7.49 (m, 2H), 7.75 (d, J = 9.6
Hz, 1H), 7.85 (s, 1H), 7.94-7.97 (m, 2H), 8.22 (d, J = 2.0 Hz,
1H); 13C NMR (100 MHz, CDCl3) d: 108.4, 117.6, 120.5,
123.3, 123.8, 126.0, 126.1, 128.2, 128.7, 132.9, 143.8, 146.5;
EI-MS m/z (relative intensity) 230 (M++2), 228 (M+), 116,
89, 77, 63.
2-(4-Bromophenyl)imidazo[1,2-a]pyridine (3f)
mp 209-211 °C (lit.16 mp 210-212 °C), yield 76%. IR
(KBr) n: 1629 cm-1; 1H NMR (CDCl3) d: 6.80 (dt, J = 1.2, 6.8
Hz, 1H), 7.19 (t, J = 8.0 Hz, 1H), 7.54-7.58 (m, 2H), 7.63 (dd,
J = 0.8, 9.2 Hz, 1H), 7.81-7.85 (m, 2H), 7.86 (s, 1H), 8.12 (td,
J = 1.2, 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) d: 108.2,
112.6, 117.5, 121.9, 125.0, 125.6, 127.5, 131.8, 132.5, 144.5,
145.6; EI-MS m/z (relative intensity) 274 (M++2), 272 (M+),
193, 192, 78, 63, 51, 50.
6-Chloro-2-(4-methoxyphenyl)imidazo[1,2-a]pyridine (3k)
mp 225-226 °C (lit.17 mp 227-228 °C), yield 83%. IR
(KBr) n: 1625 cm-1; 1H NMR (CDCl3) d: 3.86 (s, 3H), 6.98 (d,
J = 8.8 Hz, 2H), 7.14 (dd, J = 2.0, 9.6 Hz, 1H), 7.59 (d, J = 9.6
Hz, 1H), 7.76 (s, 1H), 7.87 (d, J = 8.8 Hz, 2H), 8.17 (d, J = 2.0
Hz, 1H); 13C NMR (100 MHz, CDCl3) d: 55.3, 109.4, 114.2,
117.4, 120.3, 123.2, 125.4, 125.9, 127.3, 128.2, 132.0, 137.6,
146.1, 156.7; EI-MS m/z (relative intensity) 260 (M++2), 258
(M+), 243, 215, 179, 112.
2-(2-Furyl)imidazo[1,2-a]pyridine (3g)
mp 92-93 °C (lit.16 mp 92-93 °C), yield 82%. IR (KBr)
1
n: 1635 cm-1; H NMR (CDCl3) d: 6.51-6.52 (m, 1H), 6.79
(dt, J = 1.2, 6.8 Hz, 1H), 6.90 (d, J = 2.8 Hz, 1H), 7.16-7.20
(m, 1H), 7.47 (s, 1H), 7.60 (dd, J = 0.8, 9.2 Hz, 1H), 7.80 (s,
1H), 8.11 (td, J = 1.2, 6.8 Hz, 1H); 13C NMR (100 MHz,
CDCl3) d: 106.8, 107.8, 111.5, 112.5, 117.2, 125.0, 125.6,
137.8, 142.0, 145.5, 149.4; EI-MS m/z (relative intensity)
185 (M++1), 184 (M+), 156, 155, 79, 78, 63, 51.
ACKNOWLEDGEMENT
We gratefully acknowledge the National Science Coun-
cil of the Republic of China for the financial support of this
work (Grant No. 92-2113-M-037-014).
2-(2-Thienyl)imidazo[1,2-a]pyridine (3h)
Received March 29, 2004.
mp 136-137 °C (lit.17 mp 137-138 °C), yield 84%. IR
(KBr) n: 1629 cm-1; 1H NMR (CDCl3) d: 6.79 (dt, J = 1.2, 6.8
Hz, 1H), 7.10 (t, J = 4.4 Hz, 1H), 7.18 (t, J = 8.0 Hz, 1H), 7.31
(d, J = 4.8 Hz, 1H), 7.48 (d, J = 3.6 Hz, 1H), 7.62 (d, J = 9.2
Hz, 1H), 7.78 (s, 1H), 8.09 (d, J = 6.8 Hz, 1H); 13C NMR (100
MHz, CDCl3) d: 107.4, 112.5, 117.2, 123.7, 124.8, 125.0,
125.3, 127.7, 137.3, 140.7, 145.3; EI-MS m/z (relative inten-
sity) 201 (M++1), 200 (M+), 155, 78, 69, 63, 51.
REFERENCES
1. Abignente, E.; Caprariis, P. D.; Fattorusso, E.; Mayol, L. J.
Heterocycl. Chem. 1989, 26, 1875.
2. Vega, J. A.; Vaquero, J. J.; Alvarez-Builla, J.; Ezquerra, J.;
Hamdouchi, C. Tetrahedron 1999, 55, 2317.
3. Dubinsky, B.; Shriver, D. A.; Sanfilippo, P. J.; Press, J. B.;
Tobia, A. J.; Rosenthale, M. E. Drug Dev. Res. 1990, 21,
277.
3-Methyl-2-phenylimidazo[1,2-a]pyridine (3i)
mp 154-155 °C (lit.16 mp 153-154 °C), yield 75%. IR
(KBr) n: 1629 cm-1; 1H NMR (CDCl3) d: 2.66 (s, 3H), 6.87 (t,
J = 6.8 Hz, 1H), 7.19 (t, J = 8.0 Hz, 1H), 7.36 (t, J = 7.6 Hz,
1H), 7.48 (t, J = 7.6 Hz, 2H), 7.66 (d, J = 9.2 Hz, 1H), 7.79-
7.81 (m, 2H), 7.92 (d, J = 6.8 Hz, 1H); 13C NMR (100 MHz,
CDCl3) d: 9.5, 112.0, 115.8, 117.3, 122.8, 123.5, 127.3,
128.3, 128.4, 134.7, 142.3, 144.2; EI-MS m/z (relative inten-
sity) 208 (M+), 207, 103, 84, 79, 78, 63, 51.
4. (a) Katsura, Y.; Nishino, S.; Inoue, Y.; Tomoi, M.; Takasugi,
H. Chem. Pharm. Bull. 1992, 40, 371. (b) Starrett, J. E.;
Montzka, T. A.; Crosswell, A. R.; Cavanagh, R. L. J. Med.
Chem. 1989, 32, 2204.
5. (a) Louis, E. C. US Patent 2785133, 1957. (b) Chem. Abstr.
1957, 51, 9175.
6. Fisher, M. H.; Lusi, A. J. Med. Chem. 1972, 15, 982.
7. Tomoda, H.; Hirano, T.; Saito, S.; Mutai, T.; Araki, K. Bull.
Chem. Soc. Jpn. 1999, 72, 1327.