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(DMSO‐d6) δ ppm: 1.26 [t, 3H, CH3–CH2, J = 7.20 Hz], 4.27 [q, 2H,
CH2–CH3, J = 7.20 Hz], 4.53 [s, 2H, SCH2], 7.16–7.74 [m, 8H, aromatic],
and 9.99 [s, 1H, NH]. MS (m/z): 413 (M+, 12.08%), 415 (M+2, 3.62%),
287 (M+–NHC6H4Cl, 60.18%), and 259 (M+–CONHC6H4Cl, 100%).
Anal. calcd. for (C19H16ClN5O2S) (M.W. = 413): C, 55.14; H, 3.90;
N, 16.92%; found: C, 54.99; H, 3.92; N, 17.02%.
2‐{[5‐Ethyl‐4‐oxo‐4,5‐dihydro‐[1,2,4]triazolo[4,3‐a]quinoxalin‐1‐
yl]thio}‐N‐(p‐tolyl)acetamide (33)
White solid. Yield: 70%; m.p. 255–257°C. IR (KBr) cm−1: 3295 (NH),
3084 (C–H aromatic), 2976 (C–H aliphatic), and 1663 (2C═O). 1H NMR
(DMSO‐d6) δ ppm: 1.26 [t, 3H, CH3–CH2, J = 7.20 Hz], 2.32 [s, 3H,
CH3–C6H5], 4.27 [q, 2H, CH2–CH3, J = 7.20 Hz], 4.53 [s, 2H, SCH2],
7.06–7.81 [m, 8H, aromatic], and 10.21 [s, 1H, NH]. MS (m/z): 393 (M+,
11.75%), 364 (M+–C2H5, 4.22%), 302 (M+–C6H4CH3, 8.09%), 287
(M+–NHC6H4CH3, 81.43%), and 259 (M+–CONHC6H4CH3, 100%).
Anal. calcd. for (C20H19N5O2S) (M.W. = 393): C, 61.05; H, 4.87; N,
17.80%; found: C, 61.11; H, 4.81; N, 17.86%.
N‐(3‐Chlorophenyl)‐2‐{[5‐ethyl‐4‐oxo‐4,5‐dihydro‐[1,2,4]triazolo‐
[4,3‐a]quinoxalin‐1‐yl]thio}acetamide (29)
White solid. Yield: 82%; m.p. 231–233°C. IR (KBr) cm−1: 3262 (NH),
3055 (C–H aromatic), 2984 (C–H aliphatic), and 1664 (2C═O). 1H NMR
(DMSO‐d6) δ ppm: 1.23 [t, 3H, CH3–CH2, J = 7.20 Hz], 4.27 [q, 2H,
CH2–CH3, J = 6.90 Hz], 4.47 [s, 2H, SCH2], 7.10–7.74 [m, 8H, aromatic],
and 10.32 [s, 1H, NH]. MS (m/z): 413 (M+, 10.73%), 415 (M+2, 3.25%),
287 (M+–NHC6H4Cl, 77.81%), and 259 (M+–CONHC6H4Cl, 100%).
Anal. calcd. for (C19H16ClN5O2S) (M.W. = 413): C, 55.14; H, 3.90;
N, 16.92%; found: C, 55.22; H, 3.95; N, 16.99%.
N‐(2,6‐Dimethylphenyl)‐2‐{[5‐ethyl‐4‐oxo‐4,5‐dihydro‐[1,2,4]tri‐
azolo[4,3‐a]quinoxalin‐1‐yl]thio}acetamide (34)
White solid. Yield: 65%; m.p. 272–274°C. IR (KBr) cm−1: 3267 (NH),
3080 (C–H aromatic), and 2981 (C–H aliphatic), 1660 (2C═O).
1H NMR (DMSO‐d6) δ ppm: 1.24 [t, 3H, CH3–CH2, J = 7.20 Hz], 2.29
[s, 6H, 2CH3–C6H5], 4.25 [q, 2H, CH2–CH3, J = 7.20 Hz], 4.54 [s, 2H,
SCH2], 7.09–7.78 [m, 7H, aromatic], and 10.18 [s, 1H, NH]. MS (m/z):
407 (M+, 12.09%), 387 (M+–C2H5, 6.15%), 302 (M+–C6H3(CH3)2,
7.52%), 287 (M+–NHC6H3(CH3)2, 65.23%), and 259 (M+–CONHC6H3
(CH3)2, 100%). Anal. calcd. for (C21H21N5O2S) (M.W. = 407):
C, 61.90; H, 5.19; N, 17.19%; found: C, 61.78; H, 5.30; N, 17.08%.
N‐(4‐Chlorophenyl)‐2‐{[5‐ethyl‐4‐oxo‐4,5‐dihydro‐[1,2,4]triazolo‐
[4,3‐a]quinoxalin‐1‐yl]thio}acetamide (30)
White solid. Yield: 90%; m.p. 271–273°C. IR (KBr) cm−1: 3285 (NH),
3081 (C–H aromatic), 2976 (C–H aliphatic), and 1653 (2C═O). 1H NMR
(DMSO‐d6) δ ppm: 91.25 [t, 3H, CH3–CH2, J = 3.90 Hz], 4.28 [q, 2H,
CH2–CH3, J = 3.90 Hz], 4.47 [s, 2H, SCH2], 7.33–7.72 [m, 8H, aromatic],
and 10.52 [s, 1H, NH]. MS (m/z): 413 (M+, 11.62%), 415 (M+2, 3.31%),
287 (M+–NHC6H4Cl, 78.70%), and 259 (M+–CONHC6H4Cl, 100%).
Anal. calcd. for (C19H16ClN5O2S) (M.W. = 413): C, 55.14; H, 3.90; N,
16.92%; found: C, 55.24; H, 3.92; N, 17.01%.
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4.1.8
Synthesis of 1‐{[2‐ethoxyethyl]thio}‐5‐ethyl‐
[1,2,4]triazolo[4,3‐a]quinoxalin‐4(5H)‐one (35)
A
mixture of 5‐ethyl‐1‐mercapto‐[1,2,4]triazolo[4,3‐a]quinoxalin‐
N‐(2,5‐Dichlorophenyl)‐2‐{[5‐ethyl‐4‐oxo‐4,5‐dihydro‐[1,2,4]triazolo‐
[4,3‐a]quinoxalin‐1‐yl]thio}acetamide (31)
4(5H)‐one (25) (0.01 mol) and 2‐ethoxyethyl chloride (1.08 ml,
0.01 mol) in DMF (20 ml) was heated under reflux on a water bath
for 2 h. The reaction mixture was cooled then added to cold water
(200 ml) with continuous stirring. The white precipitated product
was filtered, washed with three portions of water (15 ml each), and
recrystallized from ethanol. White solid. Yield: 60%; m.p. 220–22°C.
IR (KBr) cm−1: 1123 (COC ether), 3062 (C–H aromatic), 2970 (C–H
aliphatic), 1682 (C═O). 1H NMR (DMSO‐d6) δ ppm: 1.10 [t, 3H,
NCH2–CH3], 1.29 [t, 3H, OCH2–CH3], 3.53 [q, 2H, NCH2–CH3], 3.89
[t, 2H, SCH2–CH2], 4.31 [q, 2H, OCH2–CH3], 4.53 [t, 2H, OCH2–CH2],
and 7.41–7.65 [m, 4H, aromatic]. MS (m/z): 318 (M+, 9.51%), 246
(M+–C2H5OC2H4, 100%), 218 (M+–C2H5OC2H4CO, 67.98%). Anal.
calcd. for (C15H18N4O2S) (M.W. = 318): C, 56.58; H, 5.70; N, 17.60%;
found: C, 56.61; H, 5.75; N, 17.63%.
White solid. Yield: 88%; m.p. 275–277°C. IR (KBr) cm−1: 3330 (NH),
3070 (C–H aromatic), 2966 (C–H aliphatic), and 1665 (2C═O).
1H NMR (DMSO‐d6) δ ppm: 1.26 [t, 3H, CH3–CH2, J = 7.20 Hz], 4.27
[q, 2H, CH2–CH3, J = 7.20 Hz], 4.53 [s, 2H, SCH2], 7.16–7.74 [m, 7H,
aromatic], and 10.02 [s, 1H, NH]. MS (m/z): 447 (M+, 16.83%), 449
(M+2, 5.47%), 287 (M+–NHCH6CH3Cl2, 93.11%), and 259
(M+–CONHCH6CH3Cl2, 100%). Anal. calcd. for (C19H15Cl2N5O2S)
(M.W. = 447): C, 50.90; H, 3.37; N, 15.62%; found: C, 51.02; H, 3.50;
N, 15.54%.
2‐{[5‐Ethyl‐4‐oxo‐4,5‐dihydro‐[1,2,4]triazolo[4,3‐a]quinoxalin‐1‐
yl]thio}‐N‐(m‐tolyl)acetamide (32)
White solid. Yield: 65%; m.p. 267–269°C. IR (KBr) cm−1: 3325 (NH),
3078 (C–H aromatic), 2973 (C–H aliphatic), and 1662 (2C═O). 1H
NMR (DMSO‐d6) δ ppm: 1.26 [t, 3H, CH3–CH2, J = 6.90 Hz], 2.23 [s,
3H, CH3], 4.28 [q, 2H, CH2–CH3, J = 6.90 Hz], 4.47 [s, 2H, SCH2],
6.87–7.72 [m, 7H, aromatic], and 10.30 [s, 1H, NH]. MS (m/z): 393
(M+, 10.86%), 364 (M+–C2H5, 5.34%), 302 (M+–C6H4CH3, 9.22%),
287 (M+–NHC6H4CH3, 80.54%), and 259 (M+–CONHC6H4CH3,
100%). Anal. calcd. for (C20H19N5O2S) (M.W. = 393): C, 61.05; H,
4.87; N, 17.80%; found: C, 61.11; H, 4.81; N, 17.86%.
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4.2
In vivo anticonvulsant activity evaluation
The in vivo animal studies were undertaken with approval from the
Ethics Committee of Al‐Azhar University, Nasr City, Cairo, Egypt
(approval #23PD/3/12/8R). All the trials were carried out according
to the respective international guidelines. The in vivo anticonvulsant
evaluation study was carried out following the reported procedure of