5704 Journal of Medicinal Chemistry, 2010, Vol. 53, No. 15
Xiong et al.
added. The mixture was extracted three times with 1,2-dichlor-
omethane, and the combined organic phases were dried over
sodium sulfate, filtered, and concentrated. The crude product
was purified by preparative TLC (Rf = 0.44, 60% EtOAc/
hexane, UV 254 nm) to afford 20 (67 mg, 63%) as a white solid.
1H NMR (acetonitrile-d3, 400 MHz) δ 2.42-2.48 (m, 2H),
2.48-2.54 (m, 2H), 3.35-3.42 (m, 2H), 3.37 (s, 2H), 3.57-
3.63 (m, 2H), 3.80 (s, 3H), 3.84 (s, 3H), 7.14 (t, J = 8.8 Hz, 2H),
7.60 (dd, J = 5.3, 8.8 Hz, 2H), 7.61 (s, 1H). LCMS m/z = 438.3/
440.3 [M þ H]þ.
and 4-chloro-1-methyl-1H-pyrazole-3-carboxylic acid (0.200 g,
1.20 mmol) to afford the TFA salt of 27 (0.22 g, 50%) as a white
solid. Preparation of the HCl salt was as follows. 27 (8.5 g, 23.4
mmol) was dissolved in isopropanol (60 mL), and hydrochlo-
ric acid (12 M, 7.41 mL, 89 mmol) was added. The resulting
solution was stirred at room temperature overnight. The solid
was filtered off and dried to afford 27 HCl salt (8.5 g), mp
204 °C. 1H NMR (DMSO-d6, 400 MHz) δ 3.05-3.60 (m, 4H),
3.86 (s, 3H), 3.80-4.10 (m, 4H), 4.96-5.12 (m, 2H), 7.48 (t, J =
8.8 Hz, 2H), 8.04-8.13 (m, 3H). LCMS m/z = 365.4/367.4
[M þ H]þ.
1-(4-Fluorophenyl)-2-[4-(1-methyl-1H-pyrazole-3-carbonyl)-
piperazin-1-yl]ethanone (21). 21 was prepared in a manner
similar to that described for 14 using 1-methyl-1H-pyrazole-3-
carboxylic acid (25.0 mg, 0.20 mmol) and 1-(4-fluorophenyl)-
2-(piperazin-1-yl)ethanone dihydrochloride (64 mg, 0.22 mmol)
and was obtained as a white solid (40 mg, 61%). 1H NMR
(DMSO-d6, 400 MHz) δ 3.24 (bs, 2H), 3.40-3.62 (bs, 3H),
3.78-3.88 (bs, 1H), 3.89 (s, 3H), 4.50 (bs, 1H), 4.90 (bs, 1H), 5.09
(s, 2H), 6.64 (d, J = 2.3 Hz, 1H), 7.49 (t, J = 8.8 Hz, 2H), 7.80
(d, J = 2.3 Hz, 1H), 8.06-8.11 (m, 2H), 10.4 (bs, 1H). LCMS
m/z = 331.4 [M þ H]þ.
2-[4-(4-Chloro-1-ethyl-1H-pyrazole-3-carbonyl)piperazin-1-yl]-
1-(4-fluorophenyl)ethanone (28). Compound 28 was prepared in
a manner similar to that described for 14 using 4-chloro-1-ethyl-
1H-pyrazole-3-carboxylic acid (77 mg, 0.44 mmol) and 1-(4-
fluorophenyl)-2-(piperazin-1-yl)ethanone dihydrochloride (57
mg, 0.44 mmol) and was obtained as a white solid (114 mg,
68%). 1H NMR (acetonitrile-d3, 400 MHz) δ 1.42 (t, J = 7.3 Hz,
3H), 3.31-3.50 (m, 4H), 3.90-4.11 (m, 4H), 4.15 (q, J = 7.3 Hz,
2H), 4.72 (s, 2H), 7.28-7.33 (m, 2H), 7.70 (s, 1H), 8.00-8.04 (m,
2H). LCMS m/z = 379.3/381.4 [M þ H]þ.
2-[4-(4-Bromo-1,5-dimethyl-1H-pyrazole-3-carbonyl)piperazin-
1-yl]-1-(4-fluorophenyl)ethanone (22). 22 was prepared using 25
(194 mg, 0.560 mmol) and NBS (120 mg, 0.680 mmol) as starting
materials and was obtained as the TFA salt (51 mg, 22%) as a
white solid. 1H NMR (acetonitrile-d3, 400 MHz) δ 2.27 (s, 3H),
3.30-3.53 (m, 4H), 3.79 (s, 3H), 3.78-4.28 (m, 2H), 4.46-5.05
(m, 2H), 4.77 (s, 2H), 7.32 (t, J = 8.8 Hz, 2H), 8.02 (dd, J = 5.3,
8.8 Hz, 2H). LCMS m/z = 423.3/425.3 [M þ H]þ.
2-[4-(4-Chloro-1H-pyrazole-3-carbonyl)piperazin-1-yl]-1-(4-
fluorophenyl)ethanone (29). 29 was prepared in a manner similar
to that described for 14 using 4-chloro-1H-pyrazole-3-car-
boxylic acid (29 mg, 0.2 mmol) and 1-(4-fluorophenyl)-
2-(piperazin-1-yl)ethanone dihydrochloride (65 mg, 0.22 mmol)
and was obtained as a white solid (37 mg, 53%). 1H NMR
(DMSO-d6, 400 MHz) δ 3.10-4.07 (m, 8H), 5.00 (bs, 2H),
7.45-7.49 (m, 2H), 8.05-8.10 (m, 3H), 13.6 (s, 1H). LCMS
m/z = 351.3/353.3 [M þ H]þ.
2-[4-(4-Bromo-5-methyl-1H-pyrazole-3-carbonyl)piperazin-1-
yl]-1-(4-fluorophenyl)ethanone (23). 23 was prepared using 24
(80 mg, 0.24 mmol) and NBS (116 mg, 0.65 mmol) as starting
materials and was obtained as the TFA salt (11 mg, 11%) as a
white solid. 1H NMR (acetonitrile-d3, 400 MHz) δ 2.26 (s, 3H),
3.33-3.52 (m, 4H), 3.93-4.12 (m, 4H), 4.74 (s, 2H), 7.30 (t, J =
8.8 Hz, 2H), 8.01 (dd, J = 5.3, 8.8 Hz, 2H). LCMS m/z = 409.3/
411.3 [M þ H]þ.
1-(4-Fluorophenyl)-2-[4-(1-methyl-5-trifluoromethyl-1H-pyr-
azole-3-carbonyl)piperazin-1-yl]ethanone (30). 30 was prepared
in a manner similar to that described for 14 using 1-methyl-
5-(trifluoromethyl)-1H-pyrazole-3-carboxylic acid (65 mg, 0.33
mmol) and 1-(4-fluorophenyl)-2-(piperazin-1-yl)ethanone dihy-
drochloride (107 mg, 0.36 mmol) and was obtained as a white
solid (143 mg, 100%). 1H NMR (methanol-d4, 400 MHz) δ
3.48-3.62 (m, 4H), 3.92-4.29 (m, 2H), 4.07 (s, 3H), 4.34-4.69
(m, 2H), 5.03 (s, 2H), 7.19 (s, 1H), 7.34 (t, J = 8.8 Hz, 2H), 8.12
(dd, J = 5.3, 8.8 Hz, 2H). LCMS m/z = 399.2 [M þ H]þ.
1-(4-Fluorophenyl)-2-[4-(4-iodo-1-methyl-1H-pyrazole-3-car-
bonyl)piperazin-1-yl]ethanone (31). 31 was prepared in a manner
similar to that described for 14 using 4-iodo-1-methyl-1H-
pyrazole-3-carboxylic acid (265 mg, 1.00 mmol) and 1-(4-
fluorophenyl)-2-(piperazin-1-yl)ethanone dihydrochloride (295 mg,
1.00 mmol) and was obtained as a white solid (390 mg, 85%). 1H
NMR (acetonitrile-d3, 400 MHz) δ 3.18-3.72 (m, 4H), 3.88 (s,
3H), 4.07-4.52 (m, 4H), 4.79 (s, 2H), 7.33 (t, J = 8.8 Hz, 2H),
7.69 (s, 1H), 8.02 (dd, J = 5.3, 8.8 Hz, 2H). LCMS m/z = 457.3
[M þ H]þ.
1-(4-Fluorophenyl)-2-[4-(5-methyl-2H-pyrazole-3-carbonyl)-
piperazin-1-yl]ethanone (24). 24 was prepared in a manner
similar to that described for 14 using 3-methyl-1H-pyrazole-5-
carboxylic acid (19 mg, 0.15 mmol) and 1-(4-fluorophenyl)-
2-(piperazin-1-yl)ethanone dihydrochloride (49 mg, 0.165
1
mmol) and was obtained as a solid (26 mg, 53%). H NMR
(400 MHz, CDCl3) δ 2.34 (s, 3H), 2.66 (bs, 4H), 3.82 (s, 2H), 3.88
(bs, 2H), 4.02 (bs, 2H), 6.38 (s, 1H), 7.14 (t, J = 8.6 Hz, 2H),
7.99-8.09 (m, 2H). LCMS m/z = 331.3 [M þ H]þ.
2-[4-(1,5-Dimethyl-1H-pyrazole-3-carbonyl)piperazin-1-yl]-1-
(4-fluorophenyl)ethanone (25). 25 was prepared in a manner
similar to that described for 14 using 1,5-dimethyl-1H-pyra-
zole-3-carboxylic acid (182 mg, 1.30 mmol) and 1-(4-
fluorophenyl)-2-(piperazin-1-yl)ethanone dihydrochloride (422
mg, 1.43 mmol) and was obtained as a white solid (411 mg,
91%). 1H NMR (acetonitrile-d3, 400 MHz) δ 2.27 (s, 3H),
3.19-3.58 (m, 4H), 3.76 (s, 3H), 3.84-4.17 (m, 4H), 4.76 (s,
2H), 6.43 (s, 1H), 7.32 (t, J = 8.8 Hz, 2H), 8.02 (dd, J = 5.3, 8.8
Hz, 2H). LCMS m/z = 345.4 [M þ H]þ.
1-(4-Fluorophenyl)-2-[4-(5-methyl-2-phenyl-2H-pyrazole-3-
carbonyl)piperazin-1-yl]ethanone (32). Compound 32 was pre-
pared in a manner similar to that described for 14 using
3-methyl-1-phenyl-1H-pyrazole-5-carboxylic acid (30 mg, 0.15
mmol) and 1-(4-fluorophenyl)-2-(piperazin-1-yl)ethanone dihy-
drochloride (49 mg, 0.165 mmol) and was obtained as a white
solid (32 mg, 52%). 1H NMR (400 MHz, CDCl3) δ 2.35 (s, 3H),
2.60-2.67 (m, 2H), 2.69 (bs, 2H), 3.81 (s, 2H), 3.89 (bs, 2H), 4.16
(bs, 2H), 6.62 (s, 1H), 7.13 (t, J = 8.5 Hz, 2H), 7.38-7.54 (m,
5H), 7.99-8.09 (m, 2H). LCMS m/z = 407.5 [M þ H]þ.
Biological Assays. [125I]DOI Binding to Recombinant Human
5-HT2A and 5-HT2C Receptors. Radioligand binding assays for
human 5-HT2A and 5-HT2C receptors were developed using
crude plasma membranes prepared from HEK293 cells sta-
bly expressing these receptors. The 5-HT2 agonist [125I]DOI
(0.5 nM) was used as radioligand, and nonspecific radioligand
binding was determined in the presence of 10 μM cold DOI.
Competition experiments were as follows: 95 μL of assay buffer
(20 mM HEPES, pH 7.4, 10 mM MgCl2), 50 μL of membranes
(5-25 μg of protein), 50 μL of [125I]DOI (0.5 nM final assay
2-[4-(1-tert-Butyl-5-methyl-1H-pyrazole-3-carbonyl)piperazin-
1-yl]-1-(4-fluorophenyl)ethanone (26). 26 was prepared in a
manner similar to that described for 14 using 1-tert-butyl-5-
methyl-1H-pyrazole-3-carbonyl chloride (49 mg, 0.24 mmol)
and 1-(4-fluorophenyl)-2-(piperazin-1-yl)ethanone dihydroch-
loride (78 mg, 0.26 mmol) and was obtained as a solid (49 mg,
52%). 1H NMR (acetonitrile-d3, 400 MHz) δ 1.62 (s, 9H), 2.46
(s, 3H), 3.44 (m, 4H), 3.90-4.08 (m, 4H), 4.72 (s, 2H), 6.45 (s,
1H), 7.30 (t, J = 8.8 Hz, 2H), 8.01 (d, J = 8.8 Hz, 2H). LCMS
m/z = 387.3 [M þ H]þ.
2-[4-(4-Chloro-1-methyl-1H-pyrazole-3-carbonyl)piperazin-1-
yl]-1-(4-fluorophenyl)ethanone (27). 27 was prepared in a manner
similar to that described for 14 using 1-(4-fluorophenyl)-
2-(piperazin-1-yl)ethanone dihydrochloride (0.37 g, 1.2 mmol)