1,5-Diphenyl-4-pyrazolin-3-one (8a). Yellow amorphous solid from benzene, mp 250°C (authentic
251°C [6]); yield 76.87%. IR spectrum, ν, cm–1: 3150 (NH), 3050 (CH aromatic), 1680 (C=O amidic), 1590
(C=C). 1H NMR spectrum (DMSO-d6), δ, ppm: 5.8 (1H, s, CH, pyrazolone proton), 9.94 (1H, s, NH), a multiplet
extended at δ values: 7.12, 7.17, 7.10, 7.28, 7.24, and 7.15 (10H, aromatic protons). 13C NMR spectrum
(DMSO-d6), δ, ppm: 161.54 (C=O), 93.91 (=CH), 142.95 (C-5), 130.02, 127.84, 128.01, 127.79 (C6Hs) 139.67,
124.07, 128.21, 124.77 (C6H5). Mass spectrum, m/z (Irel, %): 236 [M]+ (100), 235 (40.2), 208 (4.9), 218 (1.8), 207
(23.8), 193 (2), 180 (11.8), 130 (1.3), 134 (1.0), 133 (4.3), 119 (1.1), 108 (1.7), 107 (1.5), 77 (53.9). Found, %:
C 76.10; H 5.07; N 11.78. C12H12N2O5 (236.27). Calculated, %: C 76.25; H 5.11; N 11.85.
5-(4'-Methylphenyl)-1-phenyl-4-pyrazolin-3-one (8b). Yellow amorphous solid from ethanol, mp
252-254°C; yield 77.86%. IR spectrum, ν, cm-1: 3160 (NH), 3050 (CH aromatic), 2950 and 2850 (CH aliphatic),
1
1660 (C=O amidic), 1580 (C=N). H NMR spectrum (DMSO-d6), δ, ppm: 5.88 (1H, s, CH, pyrazolone proton),
10.15 (1H, s, NH), 2.27 (3H, s, CH3), a multiplet extended at δ values: 7.32, 7.09, 7.11, 7.23, and 7.14 (9H,
aromatic protons). 13C NMR spectrum (DMSO-d6), δ, ppm: 94.00 (C-4, =CH), 143.19 (C-5), 161.63 (C=O), 20.72
(CH3), 139.96, 124.46, 128.16, 126.40 (C6H5), 129.06, 126.40, 128.78 and 137.74 (4-CH3C6H4). Mass spectrum,
m/z (Irel, %): 250 [M]+ (98.7), 249 (40.4), 221 (17.1), 144 (5.1), 135 (5.4), 133 (3.1), 119 (11.9), 108 (4.7), 107
(9.3), 106 (16.6), 103 (12.2), 92 (16.4), 91 (51.0), 77 (100). Found, %: C 6.77; H 5.242; N 10.91. C16H14N2O
(250.29). Calculated, %: C 76.78; H 5.63; N 11.19.
5-(4'-Methoxyphenyl)-1-phenyl-4-pyrazolin-3-one (8c). Yellow amorphous solid from benzene, mp
225°C; yield 77.39%. IR spectrum; ν, cm-1: 3220 (NH), 3050 (CH aromatic), 2900 and 2850 (CH aliphatic), 1680
1
(C=O amidic), 1600 (C=C). H NMR spectrum (DMSO-d6), δ, ppm: 5.88 (1H, s, CH, pyrazolone proton); 10.15
(1H, s, NH); 3.77 (3H, s, OCH3); a multiplet extended at δ values: 6.10, 6.88, 7.16, 7.32, 7.23 (9H, aromatic
protons). 13C NMR spectrum (DMSO-d6), δ, ppm: 93.79 (C-4, CH); 143.08 (C-5); 161.67 (C=O); 55.13 (OCH3);
122.73, 124.49, 113.98, 159.17 (4-OCH3C6H4); 140.04, 129.59, 128.82, 126.36 (C6H5). Mass spectrum, m/z
(Irel, %): 266 [M]+ (100), 265 (18.2), 248 (3.0), 210 (6.3), 135 (4.3), 133 (8.8), 119 (5.2), 92 (10.0), 105 (5.8), 77
(28.8). Found, %: C 71.85; H 4.78; N 10.35. C16H14N2O2 (266.29). Calculated, %: C 72.16; H 5.29; N 10.52.
5-(2'-Nitrophenyl)-1-phenyl-4-pyrazolin-3-one (8d). Brown amorphous solid from ethanol, mp
273-252°C; yield 71.82%. IR spectrum, ν, cm-1: 3150 (NH), 3050 (CH aromatic), 2900 (CH aliphatic), 1680
(C=O amidic), 1590 (C=C). 1H NMR spectrum (DMSO-d6), δ, ppm: 5.88 (1H, s, =CH, pyrazolone proton); 12.16
(1H, s, NH); a multiplet extended at δ values 7.90, 7.49, 7.63, 7.57, 7.12, 7.33, and 7.27 (9H, aromatic protons).
13C NMR spectrum (DMSO-d6), δ, ppm: 87.74 (C-4, =CH); 154.88 (C-5); 162.82 (C=O); 148.30, 130.71,
123.66, 128.86, 135.96, 129.03 (2-NO2, C6H4); 143.03, 113.26, 130.71, 119.44 (C6H5). Found, %: C 64.21;
H 3.89; N 14.65. C12H11N3O3 (281.26). Calculated, %: C 64.05; H 3.91; N 14.94.
Reduction of 4-arylidene(alkylidene)-1-phenyl-3,5-pyrazolidinedione (2) with Sodium Borohydride
(General Method). A slow stream of helium was bubbled through a solution of sodium borohydride (0.78 g,
0.02 mol) in water (15 ml), and compound 2 (0.01 mol) in methanol (20 ml) was added dropwise for 5 min. The
mixture was left at room temperature for further 10 min, and the solution was acidified by using diluted HC1 to
destroy the excess of sodium borohydride. The mixture was extracted with diethyl ether and dried over anhydrous
sodium sulfate. The solvent was evaporated under reduced pressure, and the solid was collected and recrystallized
from the proper solvent.
4-Isopropyl-1-phenyl-3,5-pyrazolidinedione (10e). Yellow amorphous solid from chloroform, mp 90-92°C;
yield 85.5%. IR spectrum, ν, cm-1: 3400 (NH), 3030 (CH aromatic), 2950, and 2850 (CH aliphatic), 1730 (C=O), 1670
(CO amidic). 1H NMR spectrum (CDCl3), δ, ppm (J, Hz); 3.10 (6H, d, J = 4.5, 2CH3); 2.38 (1H, octet, J = 4.5, CH);
3.05 (1H, d, J = 7.5, CH) and a multiplet centered at δ 7.3 (6H, 5-C6H5 and 1H, NH). Mass spectrum, m/z (Irel, %): 218
[M]+ (93.5), 203 [M+–CH3] (100), 105 [M+–C5H9N2O] (22.3), 176 [M+–C3H6] (28.3). Found, %: C 65.90; H 6.50;
N 13.00. C12H14N2O2 (218). Calculated, %: C 66.05; H 6.42; N 12.84.
1135