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V. G. DESAI ET AL.
General Procedure for the Synthesis of Pyrazoles from N-Aryl
Hydrazones (4 and 7)
Dichlorodicyanoquinone (1.33 mmol) was added with stirring to a solution of
N-arylhydrazones 3 or 6 (0.669 mmol) in dichloromethane (5 mL) at rt. The solution
immediately turned greenish in color. After stirring for 2 h, the reaction mixture was
monitored by thin-layer chromatography (TLC) and was then filtered and washed
with dichloromethane. The dichloromethane layer was washed with 2N sodium
hydroxide (2 ꢂ 10 mL) and then with water (1 ꢂ 5 mL). The organic layer was dried
over anhydrous sodium sulfate and concentrated to give a light yellow solid, which
was recrystallized from ethanol to give 1,3,5-triarylsubstitutedpyrazole 4 or 7.
Selected Data
5-(4’-Chlorophenyl)-1,3-diphenylpyrazole 4 (Table 1, Entry 3). Yield
1
68.71%; mp 114–116ꢀC. H NMR (300 MHz, CDCl3): d 6.83 (s, 1H), 7.20–7.29
(m, 5H), 7.31–7.42 (m, 5H) 7.92 (d, 2H), 7.45 (d, 2H).
3-(4’-Methoxyphenyl)-1,5-diphenylpyrazole 4 (Table 1, Entry 6). Yield
84.5%; mp 78–79 ꢀC. IR (KBr): 3050, 2880, 1600, 1490, 1250 cmꢁ1 1H NMR
.
(300 MHz, CDCl3): d3.88 (s, 3H), d 6.75 (s, 1H, 4-H), d7.828–8.058 (m, 5H),
7.53–7.66 (m, 5H) 6.97–7.35 (m, 4H).
3-(p-Chlorophenyl)-5-phenyl-1-(2’,4’-dinitrophenyl)pyrazole 4 (Table 1,
Entry 10). Yield 88.43%; mp 196–197 ꢀC, IR (KBr): 3100, 1620, 1550, 1500,
680 cmꢁ1 1H NMR (300 MHz, CDCl3): d 6.9 (s, 1H, 4-H), 7.1–7.4 (m, 5H),
.
7.76–7.83 (m, 4H), 7.83 (d, 1H), 8.75 (d, 1H), 9.058 (d, 1H). 13C NMR (75 MHz,
CDCl3): d 116, 117, 116, 126,127, 127.6, 128.3, 128.4, 128.7, 129.05, 129.11,
129.45, 129.46, 129.53, 129.6, 129.91, 130.0, 130.19, 130.39, 130.61, 137.469, 141.3,
155.1, 157.5.
3-(4’’-Methoxyphenyl)-5-phenyl-1-(2’,4’-dinitrophenyl)-pyrazole4(Table1,
Entry 11). Yield 88.43%; mp 196–197 ꢀC. IR (KBr): 3100, 2950, 1630, 1550, 1500,
1
1250 cmꢁ1. H NMR (300 MHz, CDCl3): d 3.87 (s, 3H), d 6.87 (s, 1H), 7.25–7.44
(m, 5H), 7.78 (d, 2H), 7.35 (d, 2H) 7.78 (d, 2H), 8.71 (d, 1H).
3-(4’’Bromophenyl)-5-(4’-methoxyphenyl)-1-phenylpyrazole 4 (Table 1,
Entry 14). Yield 84%; mp 139 ꢀC. IR (KBr): 3050, 2900, 1600, 1510, 1250,
1
700 cmꢁ1. H NMR (300 MHz, CDCl3): d 3.85 (s, 3H,), d 6.834 (s, 1H), 7.34–7.37
(m, 4H), 7.530–7.642 (m, 5H), 7.772–7.88 (m, 4H).
3-(p-Bromophenyl)-5-(p-chlorophenyl)-1-(2’,4’-dinitrophenyl)pyrazole 4
(Table 1, Entry 16). Yield 75%; mp 146 ꢀC. IR (KBr): 3100, 1620, 1550, 1500, 820,
1
650 cmꢁ1. H NMR (300 MHz, CDCl3): d 6.79 (s, 1H), 7.29–7.81 (m, 8H), 8.30 (d,
2H), 8.68 (d, 1H).
3-Methyl-5-(p-chlorophenyl)-1-(2’,4’-dinitrophenyl)pyrazole 7a (Table 2,
1
Entry 4). Yield 90%; mp 133 ꢀC. H NMR (300 MHz, CDCl3): d 2.35 (s, 3H), 6.79
(s, 1H, 4-H), 7.08–7.51 (m, 4H), 8.75 (dd, 1H, J ¼ 1.8 Hz), 9.16 (d, 2H, J ¼ 1.2 Hz).
13C NMR (75 MHz, CDCl3): d 14.1, 107.1, 110, 117, 120, 121.4, 123.9, 127.7, 128.3,