1652 Arora et al.
Asian J. Chem.
conical flask. The reaction mixture was stirred for 15 min at
room temperature followed by the addition of 2 drops of glacial
acetic acid as catalyst. The reaction mixture was warmed on
water bath for 15 min and was then cooled in beaker containing
ice to afford crystals of respective hydrazones. The crude
hydrazones were then dried. Polyphosphoric acid (10 g) was
taken in a 150 mL beaker and synthesized hydrazones were
added in small lots to the acid with constant stirring on boiling
water bath. The mixture was further stirred for about 20 min.
The hot solution was then poured in a beaker containing ice
cold water which resulted in the formation of precipitates. The
precipitation was further completed by stirring the mixture
for 10-15 min. The crude product so formed was allowed to
settle and then filtered. The product was washed with cold
methanol and allowed to dry. The product was recrystallized
by dissolution in hot ethanol and addition of activated charcoal
(0.1 g) and was filtered hot. The filtrate was reheated to boiling
and water was added to cloudy point. The ethanol was added
dropwise to redissolve the cloudy precipitates and the solution
was allowed to cool at room temperature. Physical data of all
the synthesized compounds have been recorded (Table-1).
= 8.6 Hz), 7.53-7.51 (1H, d,Ar-H, J =7.8 Hz), 7.47-7.45 (2H,
d, Ar-H, J = 8.6 Hz), 7.40-7.38 (1H, d, Ar-H, J = 7.44 Hz),
7.11-7.07 (1H, t, Ar-H, J = 7.84 Hz), 7.01-6.97 (1H, t, Ar-H,
J = 7.84 Hz), 6.86 (s, 1H, -CH=). 13C NMR (100 MHz, CDCl3,
δ ppm) 137.11-111.16 (aromatic carbons), 98.90(-CH=).Anal.
calcd. (%) for C14H10NCl: C, 73.85; H, 4.39; N, 6.15. Found
(%): C, 73.81; H, 5.02; N, 6.18 %.
2-(4-Bromophenyl)-1H-indole (3):Yield 75 %, m.p. 215-
216 °C. UV (λmax, nm) 285, IR (KBr, νmax, cm-1): 3350 (N-H
str.), 3050 (Ar C-H str.), 1570 (Ar C-C str.), 1242 (C-N str.),
1
720 (N-H bending), 501 (C-Br str.). H NMR (400 MHz,
CDCl3, δ ppm): 11.76 (1H, s, NH), 7.77-7.75 (2H, d, Ar-H, J
= 8.6Hz), 7.58-7.56 (2H, d, Ar-H J = 8.6 Hz), 7.52-7.51 (1H,
d, Ar-H, J = 7.9 Hz), 7.40-7.38 (1H, d, Ar-H, J = 7.52 Hz),
7.11-7.07 (1H, t, Ar-H, J = 7.83 Hz), 7.01-6.99 (1H, t, Ar-H,
J = 7.83 Hz), 6.83 (1H, s, -CH=). 13C NMR (100 MHz, CDCl3,
δ ppm) 138.21-109.14 (aromatic carbons), 98.90 (-CH=).Anal.
calcd. (%) for C14H10NBr: C, 61.99; H, 3.69; N, 5.17. Found
(%): C, 62.00; H, 3.68; N, 5.18 %.
2-(3-Nitrophenyl)-1H-indole (4):Yield 68 %, m.p. 166-
167 °C. UV (λmax, nm) 284.5, IR (KBr, νmax, cm-1): 3456 (N-H
str.), 3062 (aromatic C-H str.), 1578 (aromatic C-C str.), 1485
(νas N-O str), 1335 (νs N-O str), 1242 (C-N str.), 738 (N-H
bending). 1H NMR (400 MHz, CDCl3, δ ppm): 11.75(1H, s,
NH), 8.70 (1H, s, Ar-H), 8.26-8.24 (1H, d, Ar-H, J = 7.8 Hz),
8.11-8.09 (1H, d, Ar-H, J = 8.0 Hz), 7.69-7.65 (1H, t, Ar-H, J
= 8.0 Hz), 7.57-7.55 (1H, d, Ar-H, J = 7.8 Hz), 7.44-7.42
(1H, d, Ar-H, J = 8.1 Hz) 7.16-7.12 (1H, t, Ar-H, J = 7.2
Hz),7.04-7.02 (1H, t, Ar-H, J = 7.2 Hz), 7.00 (1H, s, -CH=).
13C NMR (100 MHz, CDCl3, δ ppm): 148.11-112.45 (aromatic
carbons), 98.82 (-CH=). Anal. calcd. (%) for C14H10N2O2: C,
70.59; H, 4.20; N, 11.76. Found (%): C, 70.61; H, 4.21; N,
11.75 %.
TABLE-1
PHYSICAL PARAMETERS OF
DIFFERENT 2-PHENYL-1H-INDOLES
Compd.
No.
Yield
(%)
m.p.
(°C)
m.f.
Colour
Rfa
C15H13N
Off white
Off white
Off white
28
78
75
68
72
0.86
0.83
0.91
0.85
0.73
212-213
200-201
214-215
166-167
170-171
1
2
3
4
5
C14H10NCl
C14H10NBr
C14H10N2O2 Off white
C14H10N2O2 Light brown
aRunning solvent for thin layer chromatography dichloromethane:
petroleum ether (50:50)
2-(4-Nitrophenyl)-1H-indole (5): Yield 72 %, m.p. 170-
171 °C. UV (λmax, nm) 283.5, IR (KBr, νmax, cm-1): 3451 (N-H
str.), 3062 (aromatic C-H str.), 1575 (aromatic C-C str.), 1490
(νas N-O str), 1338 (νs N-O str), 1235 (C-N str.), 735 (N-H
bending). 1H NMR (400 MHz, CDCl3, δ ppm): 11.73 (1H, s,
NH), 8.26-8.24 (2H, d, Ar-H, J = 8.72 Hz), 8.06-8.04 (2H, d,
Ar-H, J = 8.72 Hz), 7.58-7.56 (1H, d, Ar-H, J = 7.9 Hz),
7.47-7.45 (1H, d, Ar-H, J = 8.0 Hz), 7.18-7.14 (1H, t, Ar-H, J
= 7.8 Hz), 7.05-7.01 (1H, t, Ar-H, J = 8.0 Hz), 6.49(1H, s,
-CH=). 13C NMR (100 MHz, CDCl3, δ ppm): 147.11-112.43
(aromatic carbons), 91.70 (-CH=). Anal. calcd. (%) for
C14H10N2O2: C, 70.59; H, 4.20; N, 11.76. Found (%): C, 70.57;
H, 4.19; N, 11.78 %.
Testing of fungicidal activity: Synthesized 2-phenyl-1H-
indoles (1-5) were evaluated for their in vitro antifungal activity
against R. solani and F. monilliforme by poisoned food tech-
nique [17] using DMSO as control and bavistin as standard.
The per cent inhibition and ED50 of synthesized compounds
against both the test fungi was determined.
2-(4-Tolyl)-1H-indole (1):Yield 28 %, m.p. 212-213 °C.
UV (λmax, nm) 284.5, IR (KBr, νmax, cm-1): 3470 (N-H str.),
3070 (Ar C-H str.), 2856, 2966 (aliphatic C-H str.), 1570 (Ar.
C-C str.), 1240 (C-N str.), 720 (N-H bending). 1H NMR (400
MHz, CDCl3, δ ppm): 11.48 (s, 1H), 7.76-7.74 (2H, d, Ar-H,
J = 8.2 Hz), 7.72-7.69 (1H, d, Ar-H, J = 7.4 Hz), 7.41-7.38
(1H, d, Ar-H, J = 7 Hz), 7.27-7.25 (2H, d, Ar-H, J = 8.2 Hz),
7.21-7.18 (1H, t, Ar-H, J = 7.2 Hz), 7.01-6.99 (1H, t, Ar-H, J
= 7.2 Hz), 6.86 (s, 1H, -CH=), 2.34 (3H, s, CH3). 13C NMR
(100 MHz, CDCl3, δ ppm) 137.11-115.14 (aromatic carbons),
98.70 (-CH=), 21.3 (-CH3). Anal. calcd. (%) for C15H13N: C,
86.95; H, 6.28; N, 6.76. Found (%): C, 86.97; H, 6.30; N,
6.72 %.
RESULTS AND DISCUSSION
Synthesis of 2-phenyl-1H-indoles was done by conden-
sing substituted acetophenones namely 4-methylacetophenone,
4-chloroacetophenone, 4-bromoacetophenone, 3-nitroaceto-
phenone and 4-nitroacetophenone with phenylhydrazine in
ethanolic medium in presence of glacial acetic acid as catalyst.
The crude phenylhydrazones formed were dried and were
subjected to condensation under strongly acidic conditions with
polyphosphoric acid (Scheme-I) to afford 2-phenyl-1H-indoles
(1-5).
2-(4-Chlorophenyl)-1H-indole (2):Yield 78 %, m.p. 200-
201 °C. UV (λmax, nm) 285.5, IR (KBr, νmax, cm-1): 3432 (N-H
str.), 3081 (Ar C-H str.), 1570 (Ar C-C str.), 1228 (C-N str.),
1
750 (C-Cl str.), 723 (N-H bending). H NMR (400 MHz,
CDCl3, δ ppm): 11.51 (1H, s, NH), 7.86-7.84 (2H, d, Ar-H, J