KHANAM ET AL.
3
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1
3
apparatus and all values were uncorrected. Bruker Tensor 37
Fourier‐transform infrared (FT‐IR) spectrometer (Selangor,
Malaysia) was used to obtain IR spectra for all compounds.
ring) C‐NMR (CDCl ) δ (ppm) 171.55, 164.15, 151.77,
3
143.65, 139.65, 136.34, 135.26, 129.18, 128.3, 127.7, 121.2,
117.38, 115.84, 73.4, 56.2, 48.35, 45.01; ESI‐MS m/z:
[M + 2] 446.96.
1
13
The H‐NMR and C‐NMR spectra were obtained using
CDCl DMSO‐d as solvents on @@Bruker Advance spectro-
3/
6
meter (Selangor, Malaysia) at 300 MHz. AB‐Sciex 2000
instrument (Ontario, Canada) was used to obtain the
electrospray ionization‐mass spectra (ESI‐MS).
N‐benzhydryl‐4‐((5‐(2,4‐dichlorophenyl)‐1,3,
4‐oxadiazol‐2‐yl)methyl)piperazine (4c)
Yield: 43.76%; mp: 165 to 167°C; Anal Calcd for
C H Cl N O: C, 65.14, H, 5.05, N, 11.69; found C,
2
6
24
2 4
−1
6
5.16, H, 5.06, N, 11.69; IR (νmax cm ): 3200 (NH stretch),
2
.1.1
of N‐benzhydrylpiperazines‐1,3,
‐oxadiazole hybrids (4a–4h)
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General procedure for synthesis
3
107, 3067 (Ar‐H), 2914, 2800 (piperazine ring), 1613, 1446
1
(C=N, C=C), 1243, 1119 (C–O–C), 1291 (C–N); H‐NMR
4
(CDCl ) δ (ppm): 7.35 to 7.33 (d, 4H, Ar‐H, J = 6.6 Hz),
3
A volume of 5 mL of phosphorous oxychloride was added
dropwise to the solution containing intermediate (3)
7.30 to 7.29 (t, 4H, Ar‐H, J = 6.7 Hz), 7.21 to 7.19 (m, 5H,
phenyl), 7.14 to 7.13 (d, 2H, Ar‐H, J = 6.6 Hz), 4.88 (s, 2H,
–CH ), 4.29 (s, 1H, –CH), 3.23 (br, s, 4H, –CH –N–CH ,
(1 mmol) and substituted benzoic acid (1 mmol) and was
2
2
2
kept for refluxing for about 12 to 15 hours. On completion,
reaction mixture was cooled to the room temperature and
poured over crushed ice followed by neutralization using
piperazine ring), 2.43 (br, s, 4H, –CH –N–CH , piperazine
2
2
13
ring) C‐NMR (CDCl ) δ (ppm) 173.15, 163.75, 153.37,
3
145.45, 138.35, 134.04, 132.36, 129.58, 128.23, 126.47,
120.22, 116.18, 113.64, 70.94, 66.82, 45.65, 43.81; ESI‐MS
m/z: [M + 2] 481.4.
5% sodium bicarbonate solution. Precipitates so obtained
were filtered and dried. Crude product was then further
purified through recrystallization using a solvent mixture
(
dichloromethane:methanol, 1:1).
N‐benzhydryl‐4‐((5‐(4‐aminophenyl)‐1,3,
4‐oxadiazol‐2‐yl)methyl)piperazine (4d)
N‐benzhydryl‐4‐((5‐phenyl ‐1,3,
4
Yield: 51.6%; mp: 153 to 155°C; Anal Calcd for
C H N O: C, 76.07; H, 6.38; N, 13.65; found C, 76.06;
H, 6.38;N, 13.63; IR (νmax cm ): 3276 (NH stretch), 3100,
3
(
(
J = 6.6 Hz), 7.31 to 7.29(t, 4H, Ar‐H, J = 6.7 Hz), 7.24 to
7
J = 6.6 Hz), 4.94 (s, 2H, –CH ), 4.29 (s, 1H, –CH), 3.2
(
Yield: 49.46%; mp: 146 to 148°C; Anal Calcd for
C H N O: C,73.39, H, 6.40, N, 16.46; found C, 73.40,
‐oxadiazol‐2‐yl) methyl)piperazine (4a)
2
6
27 5
−1
H, 6.41, N, 16.45; IR (νmax cm ): 3201 (NH stretch), 3116,
3058 (Ar‐H), 2954, 2832 (piperazine ring), 1623, 1470
(C=N, C=C), 1239, 1123 (C–O–C), 1265 (C–N) H‐NMR
(CDCl ) δ (ppm): 7.74 to 7.72 (d, 4H, Ar‐H, J = 6.6 Hz),
26
26 4
−1
1
000 (Ar‐H) 2941, 2827 (piperazine ring), 1620, 1463
3
1
C=N, C=C), 1252, 1045 (C–O–C), 1380 (C–N) ; H‐NMR
7.26 to 7.23 (t, 4H, Ar‐H, J = 6.7 Hz), 6.97 to 6.94 (m, 5H,
phenyl), 6.92 to 6.91 (d, 2H, Ar‐H, J = 6.6 Hz), 5.33 (s, 2H,
–NH ), 4.67 (s, 2H, –CH ), 4.13 (s, 1H, –CH), 3.10 (br, s,
DMSO‐d ) δ (ppm): 7.42 to 7.40 (d, 4H, Ar‐H,
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2
2
.20(m, 5H, phenyl), 7.19 to 7.17 (d, 2H, Ar‐H,
4H, –CH –N–CH , piperazine ring), 2.50 (br, s, 4H,
2
2
13
–CH –N–CH , piperazine ring)
δ (ppm) 177.31, 167.63, 151.62, 141.45, 134.59, 131.51,
C‐NMR (CDCl3)
2
2
2
br, s, 4H, –CH –N–CH , piperazine ring), 2.35 (br, s, 4H,
2
2
13
–
CH –N–CH , piperazine ring) C‐NMR (DMSO‐d6)
130.96, 129.43, 128.83, 127.62, 115.30, 114.51, 77.52,
62.34, 60.72, 40.85, 40.61; ESI‐MS m/z: [M + H] 426.53.
2
2
+
δ (ppm) 176.35, 168.5, 152.67, 145.45, 137.45, 135.34,
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5
33.76, 128.88, 127.3, 126.7, 122.2, 119.68, 116.11, 70.3,
9.1, 49.75, 45.31; ESI‐MS m/z: [M+H] 411.2.
+
N‐benzhydryl‐4‐((5‐(4‐methylphenyl)‐1,3,
4
‐oxadiazol‐2‐yl)methyl)piperazine (4e)
N‐benzhydryl‐4‐((5‐(2‐chlorophenyl)‐1,3,4‐oxadia-
zol‐2‐yl)methyl)piperazine (4b)
Yield: 46.46%; mp: 161 to 163°C; Anal Calcd for
C H ClN O: C, 70.18; H, 5.66; N, 12.59; found C, 70.16;
H, 5.68; N, 12.59; IR (νmax cm ): 3216 (NH stretch), 3101,
3
(
(
7
Yield: 51.06%; mp: 143 to 145°C; Anal Calcd for
C H N O: C,76.39, H, 6.65, N, 13.20; found C, 76.40,
H, 6.64, N, 13.21; IR (νmax cm ): 3301 (NH stretch), 3289,
3123 (Ar‐H), 2900, 2885 (piperazine ring), 1618, 1458
(C=N, C=C), 1242, 1117 (C–O–C), 1263 (C–N); H‐NMR
(DMSO‐d ) δ (ppm): 7.38 to 7.37 (d, 4H, Ar‐H,
2
7
28 4
−1
26
25
4
−1
1
016 (Ar‐H), 2943, 2817 (piperazine ring), 1618, 1458
6
1
C=N, C=C), 1256, 1123 (C–O–C), 1293 (C–N); H‐NMR
J = 6.6 Hz), 7.33 to 7.31 (t, 4H, Ar‐H, J = 6.7 Hz), 7.24 to
7.19 (m, 5H, phenyl), 7.13 to 7.12 (d, 2H, Ar‐H,
CDCl ) δ (ppm): 7.39 to 7.37 (d, 4H, Ar‐H, J = 6.6 Hz),
3
.33 to 7.31 (t, 4H, Ar‐H, J = 6.7 Hz), 7.25 to 7.21 (m, 5H,
J = 6.6 Hz), 4.81 (s, 2H, –CH ), 4.47 (s, 1H, –CH), 3.23
2
phenyl), 7.16 to 7.15 (d, 2H, Ar‐H, J = 6.6 Hz), 4.91 (s, 2H,
CH ), 4.31 (s, 1H, –CH), 3.19 (br, s, 4H, –CH –N–CH ,
(br, s, 4H, –CH –N–CH , piperazine ring), 2.46 (br, s, 4H,
2
2
13
–
–CH –N–CH , piperazine ring) C‐NMR (DMSO‐d6)
δ (ppm) 172.25, 164.53, 151.52, 143.52, 134.45, 132.11,
2
2
2
2
2
piperazine ring), 2.33 (br, s, 4H, –CH –N–CH , piperazine
2
2