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Synthesis of Dimethyl
5-(
tert
-Butylamino)-1-phenyl-1
H
-pyrazole-3,4-dicarboxylate
(5a)
The procedure for the preparation of dimethyl
5-(tert-butylamino)-1-phenyl-1H-pyrazole-3,4-dicarboxylate (5a) is described as an example. To a magnetically
stirred solution of N′,2-diphenyl-1-hydrazinecarboxamide
(0.455 g, 2 mmol) and dimethyl acetylenedicarboxylate (0.284 g,
2
mmol) in dry acetone (10 mL) was added dropwise a solution of tert-butyl isocyanide (0.166 g, 2 mmol)
in dry acetone (2 mL) at ambient temperature over 10 min. Then the
reaction mixture was stirred for 36 h. The solvent was removed,
and the residue was purified by column chromatography using n-hexane-EtOAc (5:1) as eluent.
The solvent was removed and the product was obtained as colorless
oil; yield 0.48 g (72%). IR (KBr): 3423 (NH), 1745, 1697
(C=O), 1597, 1557, 1543, 1510, 1483, 1443, 1420, 1391,
1364, 1271, 1221, 1132, 1094, 1072, 1047, 941, 791, 758, 692 cm-¹. ¹H
NMR (500.1 MHz, CDCl3): δ = 1.46 [s,
9 H, C(CH3)3], 3.81 and 3.86 (2 s,
6 H, 2 × OCH3), 5.63 (br s, 1 H, NH), 7.33 (t, J = 7.5 Hz,
1 H, CH), 7.42 (dd, J = 8.2,
7.5 Hz, 2 H, 2 × CH), 7.49 (d, J = 8.2
Hz, 2 H, 2 × CH). ¹³C NMR
(125.8 MHz, CDCl3): δ = 29.06 [C(CH3)3], 51.37 [NC(CH3)3],
51.42 and 53.17 (2 × OCH3), 100.25 (N2C=C), 122.76, 127.71 and 129.14 (3 × CH),
135.25, 139.41 and 155.73 (3 × C), 162.34 and 164.18 (2 × C=O). MS: m/z (%) = 331
(18) [M+], 316 (56), 300(6),
284 (100), 275 (7), 252 (8), 243 (17), 214 (4), 185 (4), 143 (6),
77 (28), 57 (8), 41 (8). Anal. Calcd (%) for C17H21N3O4 (331.37):
C, 61.62; H, 6.39; N, 12.68. Found: C, 61.6; H, 6.5; N, 12.6.
Dimethyl 5-(Cyclohexylamino)-1-phenyl-1
H
-pyrazole-3,4-dicarboxylate (5c)
Yield 0.51 g (72%);
colorless crystals, mp 76 ˚C. IR (KBr): 3440 (NH), 1742
and 1688 (C=O), 1565, 1549, 1508, 1481, 1450, 1421, 1367,
1288, 1260, 1236, 1190, 1161, 1136, 1105, 1095, 1070, 792, 765,
696 cm-¹. ¹H NMR
(500.1 MHz, CDCl3): δ = 1.21-2.13 [m,
10 H, CH(CH
2)5],
3.62-3.66 (m, 1 H, NHCH), 3.81
and 3.83 (2 s, 6 H, 2 × OCH3), 5.44 (d, J = 7.6 Hz,
1 H, NH), 7.33 (t, J = 7.4
Hz, 1 H, CH), 7.41 (dd, J = 7.4,
7.7 Hz, 2 H, 2 × CH), 7.47 (d, J = 7.7
Hz, 2 H, 2 × CH). ¹³C NMR
(125.8 MHz, CDCl3): δ = 24.74,
25.87 and 33.22 (3 × CH2), 51.23 (NCH), 51.37
and 53.08 (2 × OCH3), 99.32 (N2C=C), 123.23, 127.97 and 129.15 (3 × CH), 135.96,
139.24 and 156.34 (3 × C), 161.89 and 163.98 (2 × C=O).
MS: m/z (%) = 357
(94) [M+], 342 (28), 324 (15),
314 (53), 282 (100), 275 (50), 256 (12), 243 (10), 167 (11), 149 (26),
77 (42), 69 (15), 55 (17). Anal. Calcd (%) for C19H23N3O4 (357.41):
C, 63.85; H, 6.49; N, 11.76. Found: C, 63.8; H, 6.5; N, 11.7.
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Ugi I.
Isonitrile Chemistry
Academic
Press;
London:
1971.
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Chem., Int. Ed. Engl.
1982,
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Walborsky HM.
Periasamy MP. In The Chemistry of Functional Groups
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Rappaport Z.
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1983.
Chap.
20.
p.835-837
<A NAME="RD25008ST-16">16</A>
After 2 h from the beginning of the
reaction, TLC analysis of the reaction mixture clearly indicated
formation of an intermediate in good yield. The reaction was quenched
by rapid evaporation of the solvent and the intermediate was purified
by a rapid column chromatography using n-hexane-EtOAc
(1:1) as eluent. The solvent was removed and the intermediate precipitated
from H2O-EtOH (1:1).
Dimethyl
2-(Anilinocarbonyl)-5-(cyclohexylamino)-1-phenyl-2,3-dihydro-1
H
-pyrazole-3,4-dicarboxylate
(10c)
White powder, mp 79-81 ˚C.
IR (KBr): 3381 and 3300 (NH), 1745, 1710 and 1685 (C=O),
1624, 1599, 1537, 1495, 1443, 1365, 1313, 1259, 1198, 1088, 1053,
1030, 1005, 781, 754, 692 cm-¹. ¹H
NMR (500.1 MHz, CDCl3): δ = 1.17-1.91 [m,
10 H, CH(CH
2)5],
3.17-3.25 (m, 1 H, NHCH), 3.58
and 3.73 (2 s, 6 H, 2 × OCH3), 5.63 (s, 1 H,
NCH), 7.11 (t, J = 7.5 Hz,
1 H, CH), 7.21 (d, J = 8.5
Hz, 1 H, NH), 7.25 (t, J = 7.4 Hz,
1 H, CH), 7.34 (dd, J = 7.8,
7.5 Hz, 2 H, 2 × CH), 7.38 (dd, J = 8.4,
7.4 Hz, 2 H, 2 × CH), 7.44 (d, J = 7.7
Hz, 2 H, 2 × CH), 7.47 (d, J = 8.4
Hz, 2 H, 2 × CH), 8.20 (s, 1 H, NHCO). ¹³C
NMR (125.8 MHz, CDCl3): δ = 24.04,
24.13, 25.06, 32.28 and 34.68 (5 × CH2), 50.62
(NHCH), 52.20 and 53.10 (2 × OCH3), 62.79 (NCH),
83.40 (N2C=C), 119.17, 122.28,
123.85, 126.90, 129.01 and 129.27 (6 × CH), 137.51 and
145.79 (2 × C), 157.16 and 159.71 (N2
C=C and C=O, urea),
166.28 and 171.07 (2 × C=O, ester). MS: m/z (%) = 479
(20) [M+ + 1], 463
(10) [M - CH3], 446 (12) [M - OCH3],
419 (46) [M - CO2CH3],
386 (11) [M - PhNH], 343 (8) [M - (CO2CH3 + Ph)],
326 (10) [M - (CO2CH3 + PhNH)],
300(100) [M - (CO2CH3 + PhNHCO)],
252 (69), 225 (15) [PhN=NCOPh+],
218 (30), 186 (25), 170 (58), 119 (34) [PhNCO+],
91 (34), 77 (62), 55 (88). Anal. Calcd (%) for C26H30N4O5 (478.55):
C, 65.26; H, 6.32; N, 11.71. Found: C, 65.0; H, 6.6; N, 11.4.