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2.2. General procedure for the synthesis of compounds 2
Ethyl 1-(2-oxo-2-phenylethyl)-3-phenyl-1H-pyrazole-5-
2.3.6. 6-(4-Chlorophenyl)-2-(4-methoxyphenyl)pyrazolo[1,5-
a]pyrazin-4(5H)-one
(2f)
carboxylate derivatives 1 (2.0 mmol) was dissolved in AcOH
(15 ml), and then formamide (5 ml) was added. The mixture was
stirred and heated to reflux for 3–7 h, until the TLC indicated the
end of the reaction. After this time, the reaction mixture was
cooled to room temperature. Precipitate was filtered and washed
with ethanol (5 ml), aqueous solution of NaHCO3 (10%, 2 × 6 ml)
and water (10 ml). Compounds 2 were obtained in 77–94% yield
with high-purity.
White solid, yield 86%; mp 324–325 ◦C; IR (KBr, cm−1):
3168–3041 (NH), 1642 (C O), 1610 (C N); 1H NMR (DMSO,
400 MHz) ı: 3.81 (s, 3H, OCH3), 7.03 (d, 2H, J = 8.8 Hz, Ar–H), 7.46 (s,
1H, pyrazole–H), 7.55 (d, 2H, J = 8.6 Hz, Ar–H), 7.80 (d, 2H, J = 8.6 Hz,
Ar–H), 7.92 (d, 2H, J = 8.8 Hz, Ar–H), 8.14 (s, 1H, pyrazine–H), 11.59
(s, 1H, NH); HRMS (C19H15ClN3O2): calcd for [M+H]+ 352.0853;
found 352.0856.
2.3.7.
2.3. The characterization of compounds 2
6-(4-Methoxyphenyl)-2-phenylpyrazolo[1,5-a]pyrazin-4(5H)-one
(2g)
2.3.1. 2,6-Diphenylpyrazolo[1,5-a]pyrazin-4(5H)-one (2a)
White solid, yield 77%; mp 307–308 ◦C; IR (KBr, cm−1):
3167–3036 (NH), 1678 (C O), 1607 (C N); 1H NMR (DMSO,
400 MHz) ı: 3.82 (s, 3H, OCH3), 7.05 (d, 2H, J = 8.7 Hz, Ar–H),
7.39 (t, 1H, J = 7.7 Hz, Ar–H), 7.48 (t, 2H, J = 7.7 Hz, Ar–H), 7.53
(s, 1H, pyrazole–H), 7.73 (d, 2H, J = 8.7 Hz, Ar–H), 7.99 (d, 2H,
J = 7.7 Hz, Ar–H), 8.04 (s, 1H, pyrazine–H), 11.50 (s, 1H, NH); HRMS
(C19H16N3O2): calcd for [M+H]+ 318.1243; found 318.1247.
White solid, yield 78%; mp 277–278 ◦C; IR (KBr, cm−1):
3165–3040 (NH), 1641 (C = O); 1H NMR (DMSO, 400 MHz) ı:
7.40 (t, 1H, J = 7.2 Hz, Ar–H), 7.46–7.52 (m, 5H, Ar–H), 7.56
(s, 1H, pyrazole–H), 7.79 (d, 2H, J = 8.2 Hz, Ar–H), 8.00 (d, 2H,
J = 7.2 Hz, Ar–H), 8.12 (s, 1H, pyrazine–H), 11.59 (s, 1H, NH); HRMS
(C18H14N3O): calcd for [M+H]+ 288.1137; found 288.1137.
2.3.2.
2-(4-Chlorophenyl)-6-phenylpyrazolo[1,5-a]pyrazin-4(5H)-one
(2b)
2.3.8. 2-(4-Chlorophenyl)-6-(4-methoxyphenyl)pyrazolo[1,5-
a]pyrazin-4(5H)-one
(2h)
White solid, yield 94%; mp 321–322 ◦C; IR (KBr, cm−1):
3167–3048 (NH), 1673 (C O); 1H NMR (DMSO, 400 MHz) ı:
7.46–7.52 (m, 3H, Ar–H), 7.54 (d, 2H, J = 8.6 Hz, Ar–H), 7.61
(s, 1H, pyrazole–H), 7.78 (d, 2H, J = 8.4 Hz, Ar–H), 8.02 (d, 2H,
J = 8.6 Hz, Ar–H), 8.13 (s, 1H, pyrazine–H), 11.65 (s, 1H, NH); HRMS
(C18H13ClN3O): calcd for [M+H]+ 322.0747; found 322.0732.
Yellow solid, yield 84%; mp 295–297 ◦C; IR (KBr, cm−1):
3168–3045 (NH), 1673 (C O), 1612 (C N); 1H NMR (DMSO,
400 MHz) ı: 3.82 (s, 3H, OCH3), 7.05 (d, 2H, J = 8.8 Hz, Ar–H), 7.53 (d,
2H, J = 8.5 Hz, Ar–H), 7.56 (s, 1H, pyrazole–H), 7.72 (d, 2H, J = 8.8 Hz,
Ar–H), 8.00 (d, 2H, J = 8.5 Hz, Ar–H), 8.02 (s, 1H, pyrazine–H), 11.54
(s, 1H, NH); HRMS (C19H15ClN3O2): calcd for [M+H]+ 352.0853;
found 352.0844.
2.3.3.
2-(4-Methoxyphenyl)-6-phenylpyrazolo[1,5-a]pyrazin-4(5H)-one
(2c)
White solid, yield 85%; mp 275–276 ◦C; IR (KBr, cm−1):
3164–3036 (NH), 1664 (C O), 1610 (C N); 1H NMR (DMSO,
400 MHz) ı: 3.81 (s, 3H, OCH3), 7.04 (d, 2H, J = 8.8 Hz, Ar–H), 7.46
(s, 1H, pyrazole–H), 7.47–7.49 (m, 3H, Ar–H), 7.77 (d, 2H, J = 7.3 Hz,
Ar–H), 7.92 (d, 2H, J = 8.8 Hz, Ar–H), 8.09 (s, 1H, pyrazine–H), 11.55
(s, 1H, NH); HRMS (C19H16N3O2): calcd for [M+H]+ 318.1243; found
318.1245.
2.3.9.
2,6-Bis(4-methoxyphenyl)pyrazolo[1,5-a]pyrazin-4(5H)-one (2i)
White solid, yield 85%; mp 305–307 ◦C; IR (KBr, cm−1):
3162–3025 (NH), 1658 (C O), 1613 (C N); 1H NMR (DMSO,
400 MHz) ı: 3.81 (s, 3H, OCH3), 3.82 (s, 3H, OCH3), 7.03 (d,
2H, J = 8.7 Hz, Ar–H), 7.04 (d, 2H, J = 8.7 Hz, Ar–H), 7.44 (s, 1H,
pyrazole–H), 7.72 (d, 2H, J = 8.7 Hz, Ar–H), 7.92 (d, 2H, J = 8.7 Hz,
Ar–H), 8.02 (s, 1H, pyrazine–H), 11.50 (s, 1H, NH); HRMS
(C20H18N3O3): calcd for [M+H]+ 348.1348; found 348.1349.
2.3.4.
6-(4-Chlorophenyl)-2-phenylpyrazolo[1,5-a]pyrazin-4(5H)-one
(2d)
White solid, yield 92%; mp 316–318 ◦C; IR (KBr, cm−1):
3173–3028 (NH), 1697 (C O); 1H NMR (DMSO, 400 MHz) ı: 7.40
(t, 1H, J = 8.0 Hz, Ar–H), 7.48 (t, 2H, J = 8.0 Hz, Ar–H), 7.55 (d, 2H,
J = 8.6 Hz, Ar–H), 7.56 (s, 1H, pyrazole–H), 7.81 (d, 2H, J = 8.6 Hz,
Ar–H), 8.00 (d, 2H, J = 8.0 Hz, Ar–H), 8.17 (s, 1H, pyrazine–H), 11.72
(s, 1H, NH); HRMS (C18H13ClN3O): calcd for [M+H]+ 322.0747;
found 322.0751.
2.4. Crystallography
Suitable single crystals of 2c for X-ray structural analysis were
obtained by slow evaporation of ethanol solution. The X-ray diffrac-
diffractometer. The structure was solved by direct methods with
method on F2 data using the SHELXL-97 program [29]. PLATON pro-
gram was used for the structure analysis [30]. Molecular graphics
were drawn by ORTEP-3 for Windows. The crystal data and details
concerning the data collection and structure refinement are given
in Table 1.
CCDC 808752 (2c) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Director, CCDC, 12, Union Road, Cambridge, CB2 1EZ,
2.3.5. 2,6-Bis(4-chlorophenyl)pyrazolo[1,5-a]pyrazin-4(5H)-one
(2e)
Yellow solid, yield 91%; mp >330 ◦C; IR (KBr, cm−1): 3156–3041
(NH), 1681 (C O); 1H NMR (DMSO, 400 MHz) ı: 7.55 (d, 2H,
J = 8.4 Hz, Ar–H), 7.57 (d, 2H, J = 8.4 Hz, Ar–H), 7.62 (s, 1H,
pyrazole–H), 7.80 (d, 2H, J = 8.4 Hz, Ar–H), 8.02 (d, 2H, J = 8.4 Hz,
Ar–H), 8.18 (s, 1H, pyrazine–H), 11.70 (s, 1H, NH); HRMS
(C18H12Cl2N3O): calcd for [M+H]+ 356.0357; found 356.0346.