Synthesis of 2-(3-methyl-2-oxoquinoxalin-1(2H)-yl)acetamide-based azetidinones as potent antimicrobial agents 133
1551 (aromatic –NO2, asym., str.) 1648 (CH=N), 1748 Light yellow solid, yield 46%, Rf (Benzene : Acetone = 8 : 2)
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(>C=O), 2341 (N–N=), 3247 (-NH).
0.85, m.p. 238◦C, H-NMR (DMSO-d6, 300 MHz,
δ ppm) : 8.18 (s, 1H, CONH), 7.86–8.07 (m, 4H,
quinoxaline ring protons, J = 1.8–7.5 Hz), 8.13–8.17
(q, 4H, A2B2 pattern, Ar–H, J = 3–5.1 Hz), 5.32 (s,
2H, CH2), 5.13 (s, 1H, CH=N), 2.64 (s, 3H, CH3); IR
(KBr, cm−1): 768 (ortho-disubstituted aromatic ring),
845 (para-disubstituted aromatic ring), 869 (aromatic
C=C), 968 (aromatic =C–H, bend), 1199 (=C–N),
1288 (aryl C–F), 1385 (C–N), 1548 (-NH, bend), 1650
(CH=N), 1745 (>C=O), 2344 (N–N=), 3245 (-NH).
2.2i
Nꢁ-(4-methoxybenzylidene)-2-(3-methyl-2-
oxoquinoxalin-1(2H)-yl)acetohydrazide (4e): Light
yellow solid, yield 43%, Rf (Benzene : Acetone = 8 : 2) 0.80,
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m.p. 218◦C, H-NMR (DMSO-d6, 300 MHz, δ ppm) :
8.02–8.05 (d, 4H, Ar–H, J = 9.6 Hz), 8.14 (s, 1H,
CONH), 7.57–7.67 (m, 4H, quinoxaline ring protons,
J = 2.4–7.5 Hz), 5.52 (s, 2H, CH2), 5.02 (s, 1H,
CH=N), 3.36 (s, 3H, OCH3), 2.35 (s, 3H, CH3); IR
(KBr, cm−1): 769 (ortho-disubstituted aromatic ring),
825 (para-disubstituted aromatic ring), 865 (aromatic
C=C), 964 (aromatic =C–H, bend), 1040 (C–O–C,
sym. str.), 1129 (aromatic C–O), 1198 (=C–N), 1240
(C–O–C, asym. str.), 1388 (C–N), 1540 (-NH, bend),
1648 (CH=N), 1745 (>C=O), 2344 (N–N=), 3250
(-NH).
2.2m Nꢁ-(2-hydroxybenzylidene)-2-(3-methyl-2-
oxoquinoxalin-1(2H)-yl)acetohydrazide (4i): Light
yellow solid, yield 48%, Rf (Benzene : Acetone = 8 : 2) 0.80,
m.p. 248◦C, H-NMR (DMSO-d6, 300 MHz, δ ppm) :
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8.15 (s, 1H, CONH), 7.77–7.87 (m, 4H, quinoxaline
ring protons, J = 1.8–6.9 Hz), 7.52–7.53 (d, 1H, Ar–H,
J = 4.8 Hz), 7.33–7.35 (d, 1H, Ar–H, J = 7.8 Hz),
7.25–7.28 (t, 2H, Ar–H, J = 4.8–5.7 Hz), 5.52 (s, 2H,
CH2), 5.03 (s, 1H, CH=N), 2.48 (s, 1H, OH), 2.54 (s,
3H, CH3); IR (KBr, cm−1): 765 (ortho-disubstituted
aromatic ring), 868 (aromatic C=C), 969 (aromatic
=C–H, bend), 1198 (=C–N), 1258 (C–O, str.) 1385
(C–N), 1545 (-NH, bend), 1649 (CH=N), 1748
(>C=O), 2340 (N–N=), 3250 (-NH), 3365 (phenolic
-OH).
2.2j Nꢁ-(3,4-dimethoxybenzylidene)-2-(3-methyl-2-
oxoquinoxalin-1(2H)-yl)acetohydrazide (4f): Light
yellow solid, yield 40%, Rf (Benzene : Acetone = 8 : 2) 0.72,
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m.p. 208◦C, H-NMR (DMSO-d6, 300 MHz, δ ppm) :
8.11 (s, 1H, CONH), 7.81–7.99 (m, 4H, quinoxaline
ring protons, J = 2.4–7.5 Hz), 7.77–7.79 (d, 1H, Ar–H,
J = 6.3 Hz), 7.67–7.69 (d, 1H, Ar–H, J = 6.6 Hz), 7.62
(s, 1H, Ar–H), 5.33 (s, 2H, CH2), 5.02 (s, 1H, CH=N),
3.62 (s, 6H, OCH3), 2.45 (s, 3H, CH3); IR (KBr, cm−1):
768 (ortho-disubstituted aromatic ring), 830 (para-
disubstituted aromatic ring), 863 (aromatic C=C), 965
(aromatic =C–H, bend), 1042 (C–O–C, sym. str.), 1132
(aromatic C–O), 1199 (=C–N), 1245 (C–O–C, asym.
str.), 1385 (C–N), 1545 (-NH, bend), 1650 (CH=N),
1745 (>C=O), 2344 (N–N=), 3245 (-NH).
2.2n
Nꢁ-(3-hydroxy-4-methoxybenzylidene)-2-(3-
methyl-2-oxoquinoxalin-1(2H)-yl)acetohydrazide (4j):
Yellow solid, yield 66%, Rf (Benzene : Acetone = 8 : 2) 0.87,
m.p. 188◦C, H-NMR (DMSO-d6, 300 MHz, δ ppm)
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: 8.12 (s, 1H, CONH), 7.87–7.97 (m, 4H, quinoxaline
ring protons, J = 2.1–8.4 Hz), 7.63 (s, 1H, Ar–H), 7.77–
7.81 (t, 1H, Ar–H, J = 3–8.2 Hz), 7.82–7.84 (d, 1H,
Ar–H, J = 6.6 Hz), 5.22 (s, 2H, CH2), 5.12 (s, 1H,
CH=N), 2.48 (s, 1H, OH), 2.54 (s, 3H, CH3), 3.62 (s,
3H, OCH3); IR (KBr, cm−1): 769 (ortho-disubstituted
aromatic ring), 849 (para-disubstituted aromatic ring),
869 (aromatic C=C), 968 (aromatic =C–H, bend),
1045 (C–O–C, sym. str.), 1132 (aromatic C–O), 1199
(=C–N), 1245 (C–O–C, asym. str.), 1252 (C–O,
str.), 1384 (C–N), 1546 (-NH, bend), 1648 (CH=N),
1749 (>C=O), 2345 (N–N=), 3245 (-NH), 3352
(phenolic -OH).
2.2k Nꢁ-(4-(dimethylamino)benzylidene)-2-(3-methyl-
2-oxoquinoxalin-1(2H)-yl)acetohydrazide (4g): Yel-
low solid, yield 54%, Rf (Benzene : Acetone = 8 : 2) 0.86, m.p.
228◦C, 1H-NMR (DMSO-d6, 300 MHz, δ ppm) : 7.03–
7.08 (q, 4H, A2B2 pattern, Ar–H, J = 3–5.7 Hz), 7.81 (s,
1H, CONH), 7.55–7.67 (m, 4H, quinoxaline ring pro-
tons, J = 2.1–8.1 Hz), 5.22 (s, 2H, CH2), 5.01 (s, 1H,
CH=N), 2.35 (s, 3H, CH3), 1.83 (s, 6H, N–CH3); IR
(KBr, cm−1): 769 (ortho-disubstituted aromatic ring),
830 (para-disubstituted aromatic ring), 865 (aromatic
C=C), 968 (aromatic =C–H, bend), 1199 (=C–N),
1384 (C–N), 1550 (-NH, bend), 1648 (CH=N), 1750
(>C=O), 2344 (N–N=), 3124 (-CH3), 3245 (-NH).
2.2o
Nꢁ-(2-fluorobenzylidene)-2-(3-methyl-2-
oxoquinoxalin-1(2H)-yl)acetohydrazide (4k): Red
solid, yield 53%, Rf (Benzene : Acetone = 8 : 2) 0.85, m.p.
248◦C, H-NMR (DMSO-d6, 300 MHz, δ ppm) : 8.14
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2.2l 2-(3-Methyl-2-oxoquinoxalin-1(2H)-yl)-Nꢁ-(4-
(s, 1H, CONH), 7.88–7.98 (m, 4H, quinoxaline ring
(trifluoromethyl)benzylidene) acetohydrazide (4h): protons, J = 1.8–7.5 Hz), 7.62–7.65 (d, 1H, Ar–H,